Structures for underwater energy storage

Abstract

The invention relates to underwater energy storage system having an energy storage device. The device having a storage tank having one or more air openings for enabling flow of air into and from the storage tank; one or more water openings for enabling flow of water into and from the storage tank; and one or more air pipes connected to the one or more air openings; the water openings are located at a bottom part of the storage tank; and the one or more air openings are located at an upper part of the storage tank and / or on a roof of said storage tank; the underwater energy storage device further includes a clamp fastened around the storage tank for reinforcing a discrete part of the storage tank.

Description

[0001] STRUCTURES FOR UNDERWATER ENERGY STORAGE

[0002] RELATED APPLICATIONS

[0003] This application claims the benefit of priority of U.S. Provisional Patent Application No.

[0004] 63 / 762,182 filed on February 24, 2025, U.S. Provisional Patent Application No. 63 / 873,605 filed on August 31, 2025, and U.S. Provisional Patent Application No.63 / 907 ,962 filed on October 30, 2025, the contents of which are incorporated herein by reference in their entirety.

[0005] This application is part of a group of filings which include this PCT application, “STRUCTURES FOR UNDERWATER ENERGY STORAGE”, Docket No. 105992, and the PCT application “WORK EXTRACTION FROM UNDERWATER COMPRESSED GAS ENERGY STORAGE SYSTEM”, Docket No. 106535, filed on the same date by the same applicant. The contents of the above applications are all incorporated by reference as if fully set forth herein in their entirety.

[0006] FIELD AND BACKGROUND OF THE INVENTION

[0007] The present invention, in some embodiments thereof, relates to underwater energy storage and, more particularly, but not exclusively, to underwater energy storage of compressed air.

[0008] Additional background art includes U.S. Patent No. US10894660B2 disclosing an underwater energy storage system including a tank for storing a compressed gas that is adapted to be stored underwater. The tank includes at least one water opening through which water from surrounding environment can flow into and out of the tank, and at least one gas opening through which the compressed gas is received. The underwater energy storage system further includes at least one duct communicating between the at least one opening for gas flow and a source of compressed gas and a compartment constructed over a roof of the tank, wherein said compartment is adapted for receiving weights at a sinking site of the tank.

[0009] Additional background art includes U.S. Patent No. US11767950B2 disclosing a compressed gas energy storage system that may include an accumulator for containing a layer of compressed gas atop a layer of liquid. A gas conduit may have an upper end in communication with a gas compressor / expander subsystem and a lower end in communication with accumulator interior for conveying compressed gas into the compressed gas layer of the accumulator when in use. A shaft may have an interior for containing a quantity of a liquid and may be fluidly connectable to a liquid source / sink via a liquid supply conduit. A partition may cover may separate the accumulator interior from the shaft interior. An internal accumulator force may act on the inner surface of the partition andthe liquid within the shaft may exert an external counter force on the outer surface of the partition, whereby a net force acting on the partition is less than the accumulator force.

[0010] SUMMARY OF THE INVENTION

[0011] Following is a non-exclusive list including some examples of embodiments of the invention. The invention also includes embodiments which include fewer than all the features in an example and embodiments using features from multiple examples, also if not expressly listed below.

[0012] Example 1. An underwater energy storage device comprising:

[0013] a. a storage tank having at least one wall and a roof comprising:

[0014] i. one or more air openings for enabling flow of air into and from said storage tank;

[0015] ii. one or more water openings for enabling flow of water into and from said storage tank; and b. one or more air pipes connected to said one or more air openings;

[0016] said water openings are located at a bottom part of said at least one wall of said storage tank; and said one or more air openings are located at an upper part of said at least one wall of said storage tank and / or on said roof of said storage tank;

[0017] said underwater energy storage device further comprises a clamp fastened around said at least one wall of said storage tank for reinforcing a discrete part of said storage tank; said clamp comprises one or more rigid elements; and

[0018] wherein said one or more rigid elements are made of one or more of: metal, polymer and composite material comprising reinforcing fibers.

[0019] Example 2. The device according to example 1, wherein said storage tank further comprises an external coating.

[0020] Example 3. The device according to example 2, wherein said external coating is made of one or more of fiberglass, carbon, epoxy fibers and metal.

[0021] Example 4. The device according to any one of examples 2-3, wherein said external coating is positioned in a discrete part of said storage tank.

[0022] Example 5. The device according to any one of example 1-4, wherein said storage tank further comprises an internal coating for sealing said storage tank from said air.

[0023] Example 6. The device according to example 5, wherein said internal coating is made of one or more of: Polyurea, epoxy and polyethylene.

[0024] Example 7. The device according to any one of example 1-6, wherein said clamp comprises one or more adjustable elements configured for connecting said one or more rigid elements.

[0025] Example 8. The device according to example 7, wherein said one or more adjustable elements are made of one or more of: metal and polymer.Example 9. The device according to any one of examples 1-8, wherein said one or more water openings comprise one or more of the following shapes: circle, arc and oval.

[0026] Example 10. The device according to any one of examples 1-9, wherein said roof has one or more of the following shapes: flat, conical surface and dome.

[0027] Example 11. The device according to any one of examples 1-10, wherein said device is anchored by a self-weight of said device configured for counterbalancing a buoyancy force exerted on said device.

[0028] Example 12. The device according to any one of examples 1-11, further comprising at least one anchoring means comprising one or more of the following:

[0029] a. one or more weights distributed on top of and / or inside said storage tank;

[0030] b. one or more caisson anchors;

[0031] c. one or more anchor points; and

[0032] d. one or more planks;

[0033] e. one or more fillers.

[0034] Example 13. The device according to any one of examples 1-12, wherein said storage tank further comprises peripheral edges located at a bottom part of said storage tank.

[0035] Example 14. The device according to example 13, wherein one or more weights are positioned on said peripheral edges.

[0036] Example 15. The device according to example 12, further comprising an upper banister located on said roof of said storage tank; and wherein said one or more weights and / or said one or more fillers are positioned in said upper banister.

[0037] Example 16. The device according to example 15, wherein said upper banister is partitioned into a plurality of chambers.

[0038] Example 17. The device according to example 12, wherein said fillers comprise one or more of: concrete sacks, metal beams, stones, gravel sand, and precast elements having predetermined shape and / or weight.

[0039] Example 18. The device according to example 17, wherein said device further comprises a plurality of tank piercing sticks located on said roof of said device; and wherein said tank piercing sticks penetrate said concrete sacks.

[0040] Example 19. The device according to example 12, wherein said one or more weights comprise one or more of: stones, gravel and precast elements having predetermined shape and / or weight.

[0041] Example 20. The device according to example 13, further comprising a lower banister located on said peripheral edges.Example 21. The device according to any one of examples 1-20, further comprising one or more water pipes fluidly connected to said one or more water openings for communicating the storage tank with seawater outside the storage tank.

[0042] Example 22. The device according to example 21, wherein at least one water pipe from said one or more water pipes passes through a width of a lower banister.

[0043] Example 23. The device according to any one of examples 1-22, wherein said storage tank comprises a floor.

[0044] Example 24. The device according to example 23, wherein said floor is made of one or more of concrete and metal.

[0045] Example 25. The device according to example 23, wherein said one or more water openings are located to be in contact with said floor.

[0046] Example 26. The device according to any one of examples 1-25, wherein said storage tank is internally partitioned into two or more chambers; wherein said two or more chambers are interconnected by one or more internal openings that permit flow of air and water between said chambers.

[0047] Example 27. The device according to example 23, wherein said floor is conical shaped. Example 28. The device according to example 27, wherein heights at a center of said floor are higher than heights extending from said center towards walls of said storage tank.

[0048] Example 29. The device according to any one of examples 1-22, wherein said storage tank is floorless.

[0049] Example 30. The device according to any one of examples 1-29, wherein at least a portion of said one or more air pipes is positioned vertically to said roof of said storage tank.

[0050] Example 31. The device according to any one of examples 1-30, wherein at least a portion of said one or more air pipes is anchored to said storage tank.

[0051] Example 32. The device according to any one of examples 1-31, wherein said at least a portion of said one or more air pipes contacts a length of said storage tank.

[0052] Example 33. The device according to any one of examples 1-31, wherein said at least a portion of said one or more air pipes spirals around said storage tank.

[0053] Example 34. The device according to any one of example 1-34, further comprising a base; and wherein said storage tank is positioned on top of said base.

[0054] Example 35. The device according to example 34, wherein said storage tank is anchored to said base by a weight of said device.

[0055] Example 36. The device according to any one of examples 34-35, wherein said device further comprises connectors for connecting said storage tank to said base.Example 37. The device according to any one of examples 34-36, wherein said base comprises one or more discrete units positioned in proximity to one another to form said base.

[0056] Example 38. The device according to any one of examples 34-37, wherein said base comprises vertically standing poles.

[0057] Example 39. The device according to any one of examples 34-38, wherein said base further comprises a plurality of beams arranged horizontally.

[0058] Example 40. The device according to any one of examples 34-39, wherein said base comprises an upper part onto which said storage tank is mounted on and a lower part configured to conform to a surface.

[0059] Example 41. The device according to example 40, wherein said surface is a seabed.

[0060] Example 42. The device according to any one of examples 34-41, wherein said lower part of said base is horizontal.

[0061] Example 43. The device according to any one of examples 34-42, wherein said base comprises an edge.

[0062] Example 44. The device according to example 43, wherein said edge is shaped and sized to reduce a level of a turbulent water flow generated around said storage tank by maintaining the flow of water to be orderly and parallel to the surface of said base.

[0063] Example 45. The device according to example 44, wherein said edge comprises an angle from 1 degree to 89 degrees.

[0064] Example 46. The device according to example 40, wherein said lower part of said base comprises a geometry matching a geometry of a slope of the seabed.

[0065] Example 47. The device according to any one of examples 34-46, wherein said base comprises a lumen and wherein said lumen is occupied by one or more fillers.

[0066] Example 48. The device according to example 47, wherein said one or more fillers comprise a plurality of concrete sacks.

[0067] Example 49. The device according to example 48, wherein said device further comprises connecting means configured for connecting said plurality of concrete sacks to one another comprising a connecting element.

[0068] Example 50. The device according to any one of examples 34-49, wherein one or more planks are positioned in one or more of: adjacent or below to said base for securing said base in place.

[0069] Example 51. The device according to example 50, wherein said one or more planks penetrate said base.

[0070] Example 52. The device according to any one of examples 1-51, further comprising at least one means for increasing a buoyancy force exerted on said device during submerging of said device.Example 53. The device according to example 52, wherein said one or more means comprises one or more of the following:

[0071] a. Compressed air; wherein said compressed air is stored in said storage tank;

[0072] b. One or more adjustable floats configured for containing air;

[0073] c. One or more floats strings comprising a plurality of floats connected by one or more wires.

[0074] Example 54. The device according to any one of examples 1-53, comprising one or more means for preventing water entry to said one or more air pipes.

[0075] Example 55. The device according to example 54, wherein said one or more means for preventing water entry comprises a floating element; wherein actuation of said floating element is according to a rise in a water level in said storage tank.

[0076] Example 56. The device according to example 55, wherein said floating element is located in a structure configured for restricting movement of said floating element, said structure comprising one or more of: a cage and one or more vertical columns inserts.

[0077] Example 57. The device according to example 56, wherein said one or more means for preventing water entry further comprises a sealing layer positioned above said floating element, said sealing layer configured for blocking an air opening from said one or more air openings.

[0078] Example 58. The device according to example 57, wherein said floating element and said sealing layer comprise one or more holes traversing through a length of said floating element and said sealing layer for allowing positioning of said one or more vertical columns inserts inside said one or more holes and for allowing an upward movement of said sealing layer to seal said air opening from said one or more air openings.

[0079] Example 59. The device according to any one of examples 55-58, wherein said floating element is configured for blocking an air opening from said one or more air openings.

[0080] Example 60. The device according to example 55, wherein said one or more means for preventing water entry further comprises:

[0081] a. a pivot;

[0082] b. a closing element.

[0083] Example 61. The device according to example 60, wherein said closing element connects said pivot to said floating element.

[0084] Example 62. The device according to any one of examples 60-61, wherein said closing element is configured for blocking an air opening from said one or more air openings.

[0085] Example 63. The device according to any one of examples 55-58, wherein said floating element comprises a coating.Example 64. The device according to example 54, wherein said one or more means for preventing water entry comprises one or more air valves located in said one or more air pipes for enabling releasing of pressurized air from an air source; said pressurized air counteracts a pressure of incoming water.

[0086] Example 65. The device according to example 64, wherein said one or more air valves are controlled remotely.

[0087] Example 66. The device according to any one of examples 1-65 comprising one or more means for evacuating water from said one or more air pipes.

[0088] Example 67. The device according to example 66, wherein said means for evacuating water from said one or more air pipes comprises a mobile robot comprising:

[0089] a. a body;

[0090] b. at least one wheel;

[0091] c. a water pump comprising a suction tube having a distal end and configured for drawing water;

[0092] d. one or more exhaust tubes configured for releasing said water in an overall downward direction;

[0093] wherein when said mobile robot is located in said air pipe, said distal end of said suction tube contacts said water located in said air pipe.

[0094] Example 68. The device according to example 67, wherein said mobile robot further comprises one or more of the following:

[0095] a. one or more batteries;

[0096] b. a motor;

[0097] c. an illumination source;

[0098] d. a camera;

[0099] e. a safety wire configured for retrieving said mobile robot;

[0100] f. a cable; wherein said cable is connected to a power source and / or a controller.

[0101] Example 69. The device according to example 66, wherein said means for evacuating water from said one or more air pipes comprises a valve positioned in a low part of an air pipe from said one or more air pipes.

[0102] Example 70. The device according to example 69, wherein said valve is configured for releasing water to an outside water environment by a pressure difference between an air pressure inside said air pipe and a water pressure in said outside water environment.

[0103] Example 71. The device according to example 66, wherein said means for evacuating water from said one or more air pipes includes a piston device configured to move inside an air pipe fromthe one or more air pipes according to an air pressure in said air pipe from the one or more air pipes, said piston device comprising a piston having a diameter.

[0104] Example 72. The device according to example 71, wherein said piston device further comprises one or more of the following:

[0105] a. a wire connecting said piston to a controller;

[0106] b. a safety wire configured for retrieving said piston;

[0107] c. an adjustable balloon configured for adjusting said diameter of said piston;

[0108] d. a camera;

[0109] e. an illumination source;

[0110] f. a main body having one or more openings and one or more flaps; wherein said one or more openings traverse through the length of said piston; and wherein said one or more flaps are configured for controlling air passage via said one or more openings.

[0111] Example 73. The device according to any one of examples 71-72, wherein said piston device further comprises a main body having one or more openings and one or more flaps; wherein said one or more openings traverse through the length of said piston; and wherein said one or more flaps are configured for controlling air passage via said one or more openings.

[0112] Example 74. The device according to any one of examples 71-73, wherein said piston comprises a water-soluble material for eliminating a need to retrieve said piston after use.

[0113] Example 75. The device according to any one of examples 71-74, wherein said piston is made of one or more of: ice, PVA, sugar and salt.

[0114] Example 76. The device according to any one of examples 71-75, wherein said piston comprises a water soluble coating configured for reducing said diameter of said piston to a predetermined diameter following exposure to water.

[0115] Example 77. The device according to example 76, wherein said water soluble coating is made of one or more of: ice, PVA, sugar and salt.

[0116] Example 78. The device according to example 66, wherein an air pipe from said one or more air pipes comprises a main part having an opening configured for insertion of said means for evacuating water from said one or more air pipes; and a sealing element configured for sealing said main part.

[0117] Example 79. A method of fabricating a base to be positioned in an underwater location comprising:

[0118] a. scouring an existing underwater topographic map for an appropriate location according to relevant parameters;

[0119] b. selecting a plurality of optional locations according to said relevant parameters;c. performing one or more surveys for vetting said optional locations;

[0120] d. defining a general area in the seabed on which said base is to be positioned;

[0121] e. allocating markers surrounding the general area in the seabed on which said base is to be positioned;

[0122] f. scanning the surface in the area in the seabed in which said base is to be positioned to receive updated inclinations input data;

[0123] g. calculating inclinations based on said updated inclination input data;

[0124] h. generating a topographic map of the general area in the seabed on which said base is to be positioned;

[0125] i. determining a specific location of said base according to said topographic map and one or more requirements for said base;

[0126] j. calculating a graphic representation of said base shape according to said topographic map; k. fabricating said base according to said graphic representation of said base.

[0127] Example 80. The method according to example 79, wherein said relevant parameters includes one of more of: an angle of a slope or a type of ground.

[0128] Example 81. The method according to any one of examples 79-80, wherein said on or more surveys include one or more of: geographic, geologic and geotechnical surveys.

[0129] Example 82. The method according to any of examples 79-81, wherein said fabricating includes one or more of: milling, cutting, casting and 3D printing.

[0130] Example 83. The method according to any one of examples 79-82, further comprising positioning one or more rods inside and / or around said base.

[0131] Example 84. The method according to any one of examples 79-83, further comprising positioning planks in a surface to be one or more of: adjacent or below to said base for securing said base to said surface.

[0132] Example 85. The method according to any one of examples 79-84, further comprising positioning said base on said surface.

[0133] Example 86. The method according to any one of examples 79-85, further comprising positioning one or more fillers inside said base.

[0134] Example 87. An underwater energy storage system comprising:

[0135] a. a plurality of storage tanks wherein each storage tank from the plurality of storage tanks has at least one wall and a roof and comprises one or more air openings for enabling flow of air to and from said storage tank;

[0136] b. one or more first air pipes connected to each air opening from said one or more air openings;c. a second air pipe connected to said one or more first pipes configured for connecting one storage tank from said plurality of storage tanks to one or more storage tanks from said plurality of storage tanks;

[0137] d. a turbomachinery unit comprising a compressor and expander and fluidly coupled to said second pipe and configured to selectively provide air to said plurality of storage tanks and selectively receive air from said plurality of storage tanks and extract useful work form said air;

[0138] said one or more air openings are located at an upper part of said at least one wall of said storage tank from a plurality of storage tanks and / or on said roof of said storage tank from a plurality of storage tanks;

[0139] at least one storage tank from said plurality of storage tanks further comprises one or more water openings configured for enabling flow of water to and from said storage tank from the plurality of storage tanks; and

[0140] wherein at least one of said one or more water openings connect to one or more downward facing water pipes configured for enabling flow of water to and from a lower part of an outside water environment.

[0141] Example 88. The system according to example 87, wherein said system further comprises mounting means comprising at least one base configured for leveling at least one storage tank from said plurality of storage tanks.

[0142] Example 89. The system according to any one of examples 87-88, wherein said plurality of storage tanks are arranged vertically.

[0143] Example 90. The system according to any one of examples 87-89, wherein said one or more downward facing water pipes connect to a main water pipe; said water pipe positioned at a height that is at most equal to a height of a lowest positioned storage tank from said plurality of storage tanks.

[0144] Example 91. The system according to any one of examples 87-90, wherein said system further comprises a plurality of valves located on said one or more first pipes and configured for controlling communication of said one or more first pipes and said second pipe.

[0145] Example 92. An underwater energy storage system comprising:

[0146] a first storage tank having one or more water openings for water flow into the first storage tank and first one or more exit air openings for air flow in and / or out of the first storage tank

[0147] a second storage tank having:

[0148] first one or more input air openings for receiving air from said first storage tank via one or more air conducting interconnecting said first one or more air openings and said first one or more exit air openings; and

[0149] a second exit one or more air openings for air flow out of said second storage tank,a turbomachinery unit comprising a compressor and expander and fluidly coupled to said second exit one or more air openings configured to selectively provide air to said second exit one or more air openings and selectively receive air from said second exit one or more air openings and extract useful work form said air, and

[0150] wherein said openings and said storage tanks are positioned so that when air is removed from said second exit air opening, water flows into said first storage tank via said at least one water opening and when air is provided under pressure into said second exit one or more air openings, air flows into said first tank via said first air exit opening and water is pushed out of said first storage tank via said at least one water opening.

[0151] Example 93. The system according to example 92, further comprising at least one additional storage tank connected to said first storage tank and said second storage tank and configured for one or more of: receiving, releasing and storing air.

[0152] Example 94. The system according to example 93, wherein said first, second and at least one additional storage tanks are arranged vertically.

[0153] Example 95. The system according to any one of examples 93-94, wherein said first, second and at least one additional storage tanks are positioned on a surface and wherein said surface is inclined.

[0154] Example 96. A method of submerging an energy storage device and adding weights in a controlled manner comprising:

[0155] a. positioning said energy storage device in the water at a submerging site;

[0156] b. supplying a storage tank with air for storing an air volume at partial capacity of said storage tank;

[0157] c. connecting said energy storage device to a floating crane;

[0158] d. lifting said energy storage device by said floating crane until said energy storage device is stabilized only by a lifting force of said floating crane;

[0159] e. supplying said storage tank with air for storing an air volume at full capacity of said storage tank for maximizing a buoyancy force exerted on said energy storage device;

[0160] f. adding weights and / or a plurality of fillers to said energy storage device;

[0161] g. lowering said energy storage device by said floating crane;

[0162] h. assessing whether said storage tank is fully submerged;

[0163] If said energy storage tank is not fully submerged go back to step h, otherwise:

[0164] i. supplying said storage tank with air while lowering said energy storage device for maintaining a balanced weight of said energy storage device within a lifting weight capacity of said floating crane; j. assessing whether said energy storage device has reached a final position site on the seabed;If said energy storage device has not reached a final position site on the seabed go back to step k, otherwise:

[0165] k. stop lowering said energy storage device by said floating crane.

[0166] Example 97. The method according to example 96, further comprising connecting said energy storage device to floats for stabilizing said energy storage device in the water.

[0167] Example 98. The method according to any one of examples 96-97, further comprising releasing said floats following said lifting said energy storage device by said floating crane until said energy storage device is stabilized only by said lifting force of said floating crane.

[0168] Example 99. An underwater energy storage device comprising:

[0169] a. a storage tank having at least one wall and a roof comprising:

[0170] i. one or more air openings for enabling flow of air into and from said storage tank;

[0171] ii. one or more water openings for enabling flow of water into and from said storage tank; and b. one or more air pipes connected to said one or more air openings;

[0172] said one or more air openings are located at an upper part of said at least one wall of said storage tank and / or on said roof of said storage tank;

[0173] wherein said underwater energy storage device further comprises peripheral edges located at a bottom part of said storage tank.

[0174] Example 100. An underwater energy storage device comprising:

[0175] a. a storage tank having at least one wall and a roof comprising:

[0176] i. one or more air openings for enabling flow of air into and from said storage tank;

[0177] ii. one or more water openings for enabling flow of water into and from said storage tank; and b. one or more air pipes connected to said one or more air openings;

[0178] said one or more air openings are located at an upper part of said at least one wall of said storage tank and / or on said roof of said storage tank;

[0179] wherein said underwater energy storage device further comprises a floor; and wherein heights at a center of said floor are higher than heights extending from said center towards walls of said storage tank for encouraging sand removal.

[0180] Example 101. An underwater energy storage device comprising:

[0181] a. a storage tank having at least one wall, a floor and a roof and comprising:

[0182] i. one or more air openings for enabling flow of air into and from said storage tank;

[0183] ii. one or more arc shaped water openings for enabling flow of water into and from said storage tank; and

[0184] b. one or more air pipes connected to said one or more air openings;wherein said one or more air openings are located at an upper part of said at least one wall of said storage tank and / or on said roof of said storage tank; and

[0185] wherein said one or more arc shaped water openings are located to be in contact with said floor for facilitating sand removal.

[0186] Example 102. An underwater energy storage device comprising:

[0187] a. a metal storage tank having at least one wall and a roof comprising:

[0188] i. one or more air openings for enabling flow of air into and from said metal storage tank;

[0189] ii. one or more water openings for enabling flow of water into and from said metal storage tank; and b. one or more air pipes connected to said one or more air openings;

[0190] said water openings are located at a bottom part of said at least one wall of said storage tank; and said one or more air openings are located at an upper part of said at least one wall of said metal storage tank and / or on said roof of said metal storage tank;

[0191] wherein said underwater energy storage device further comprises linear structural reinforcing elements for reinforcing the metal storage tank to withstand a tensile force exerted on said metal storage tank.

[0192] Example 103. The device according to example 102, wherein said linear structural reinforcing elements comprises one or more columns.

[0193] Example 104. The device according to example 103, wherein said one or more columns are made of one or more of metal and cement.

[0194] Example 105. The device according to any one of examples 102-104, wherein said linear structural reinforcing elements comprises one or more flexible linear elements in a tensioned state.

[0195] Example 106. The device according to example 105, wherein said one or more flexible linear elements are made of one or more of metal cable and polymer.

[0196] Example 107. The device according to any one of examples 102-106, wherein said linear structural reinforcing elements are positioned vertical to a floor of said metal storage tank.

[0197] Example 108. The device according to any one of examples 102-107, wherein said linear structural reinforcing elements are positioned in an oblique angle to a floor of said metal storage tank.

[0198] Example 109. The device according to example 1, wherein said storage tank comprises a plurality of tubular structures, and wherein said plurality of tubular structures are interconnected for allowing gas exchange between said plurality of tubular structures.

[0199] Example 110. A method for manufacturing an energy storage device, the method comprising: providing a plurality of industrial tubular structures configured for storing compressed gas; arranging said plurality of industrial tubular structures in a clustered configuration;fluidly inter-connecting said industrial tubular structures to enable gas and / or water flow between said industrial tubular structures; and

[0200] connecting said cluster of said plurality of industrial tubular structures to a gas pipe for enabling flow of gas into and from said cluster of said plurality of industrial tubular structures.

[0201] Example 111. An underwater energy storage system comprising:

[0202] a. one or more storage tanks, each storage tank having at least one wall and a roof, each comprising:

[0203] i. one or more air openings for enabling flow of air into and from the respective storage tank;

[0204] ii. one or more water openings for enabling flow of water into and from the respective storage tank;

[0205] b. a main gas pipe configured for supplying compressed air and / or exhausting compressed air; c. one or more internal air pipes positioned within the one or more storage tanks and fluidly connected to said main gas pipe via the one or more air openings; and

[0206] wherein said one or more water openings are located at a bottom part of said at least one wall of each storage tank; and

[0207] wherein said one or more internal air pipes enable compressed gas from the main gas pipe to flow into and / or out of the respective storage tanks.

[0208] Example 112. The system according to example 111, wherein said one or more storage tanks comprises a plurality of storage tanks, and further comprising one or more interconnecting gas conduits fluidly connecting two or more of the plurality of storage tanks, wherein each interconnecting gas conduit comprises a first end positioned within a first storage tank and a second end positioned within a second storage tank, thereby enabling air flow between the first storage tank and the second storage tank.

[0209] Example 113. An underwater energy storage device comprising:

[0210] a plurality of vertically extending tubular structures defining at least one internal lumen configured for storing compressed gasfor storing compressed gas;

[0211] wherein said plurality of tubular structures are arranged in a clustered configuration, and are fluidly connected to one another,

[0212] wherein at least one of the plurality of the tubular structures comprises one or more water openings, configured for one or both of: (a) water ingress; and (b) water egress.

[0213] Example 114. The underwater energy storage device of example 113, wherein each of the plurality of the tubular structures comprises the one or more water openings, or at least oneof the tubular structures is sealed to the outside environment and does not comprise the one or more water openings.

[0214] Example 115. The underwater energy storage device of any of examples 113-114, wherein the plurality of tubular structures operate as one unit in terms of one or both of receiving and releasing compressed gas.

[0215] Example 116. The underwater energy storage device of any of examples 113-115, wherein the plurality of tubular structures are fluidly interconnected by a plurality of connectors.

[0216] Example 117. The underwater energy storage device of example 116, wherein said plurality of connectors are configured to transfer one or both of water and gas between the plurality of tubular structures.

[0217] Example 118. The underwater energy storage device of any of examples 113-117, wherein the plurality of tubular structures are connected to one or more gas connectors configured to allow gas transfer between the plurality of tubular structures.

[0218] Example 119. The underwater energy storage device of example 118, wherein the plurality of connectors comprises one or more connectors at different heights.

[0219] Example 120. The underwater energy storage device of any of examples 113-119, wherein the plurality of tubular structures are attached to one another.

[0220] Example 121. The underwater energy storage device of any of examples 113-120, comprising a cement cast positioned in between the plurality of the tubular structures.

[0221] Example 122. The underwater energy storage device of any of examples 113-121, wherein at least one of the plurality of the tubular structures comprises one or more air openings, connected to one or more air pipes configured for communicating the plurality of tubular structures to a turbomachinery unit.

[0222] Example 123. The underwater energy storage device of example 122, wherein the at least two of the plurality of the tubular structures is directly connected to the one or more air pipes.

[0223] Example 124. The underwater energy storage device of any of examples 123, wherein the at least two of the plurality of the tubular structures which are directly connected to the one or more air pipes are separated by at least one tubular structure.

[0224] Example 125. The underwater energy storage device of any of examples 113-124, wherein at least one of said tubular structures is made of one or more of metal, cement, and polymer.Example 126. The underwater energy storage device of example 113-125, comprising at least one weight.

[0225] Example 127. The underwater energy storage device of example 113-126, comprising more than one plurality of tubular structures arranged in a clustered configuration, wherein each of the more than one plurality of tubular structures arranged in a clustered configuration are connected to a local gas pipe configured to one or both of receive and provide gas to and from the more than one plurality of tubular structures arranged in a clustered configuration.

[0226] Example 128. The underwater energy storage device of example 127, wherein each local gas pipe is connects to a main gas pipe, wherein the main gas pipe is configured to communicates the more than one plurality of tubular structures arranged in a clustered configuration to a turbomachinery unit.

[0227] Example 129. An underwater energy storage device comprising:

[0228] at least one tubular structure positioned in a horizontal alignment relative to a seabed, and comprising one or more water openings, configured for one or both of: (a) water ingress; and (b) water egress,

[0229] wherein the at least one tubular structure is configured to store compressed gas above a water level within the tubular structure.

[0230] Example 130. The underwater energy storage device of example 129, wherein the one or more water openings are positioned at a bottom part of the at least one tubular structure.

[0231] Example 131. The underwater energy storage device of any of examples 129-130, comprising one or more air openings positioned in a top part of the tubular structure.

[0232] Example 132. The underwater energy storage device of any of examples 129-131, comprising a water exchange pipe configured for controlled insertion and removal of water.

[0233] Example 133. The underwater energy storage device of any of examples 129-132, wherein the at least one tubular structure is anchored to the seabed by one or more anchors.

[0234] Example 134. The underwater energy storage device of any of examples ***ERROR***_197-133, wherein the at least one tubular structure comprises an elongated polymer conduit.

[0235] Example 135. The underwater energy storage device of any of examples 129-134, wherein the at least one tubular structure comprises a cluster of tubular structures positioned in a generally horizontal alignment relative to a seabed.

[0236] Example 136. The underwater energy storage device of example 135, wherein the tubular structures are arranged parallel to one another.Example 137. The underwater energy storage device of example 135, wherein the tubular structures are arranged in a stacked formation.

[0237] Example 138. An energy storage system, comprising:

[0238] a. one or more compressors positioned above water and configured to compress gas; b. one or more underwater compressed gas storage devices positioned in a waterbody and configured to receive the compressed gas from the one or more compressors and store the compressed gas;

[0239] c. one or more turboexpanders positioned above water and configured to receive compressed gas from the one or more underwater compressed gas storage devices and to extract mechanical work from expansion of the compressed gas;

[0240] d. a thermal energy storage (TES) positioned and configured to store heat from the compressed gas generated during compression and to allow transfer of heat to the compressed gas prior to expansion in the one or more turboexpanders;

[0241] e. one or more first heat exchangers positioned and configured to transfer heat from the compressed gas after compression to the TES;

[0242] f. one or more second heat exchangers positioned and configured to transfer heat from the TES to the compressed gas before expansion in the one or more turboexpanders; and g. at least one external heat exchanger configured to transfer heat from an external heat source to the compressed gas before expansion in the one or more turboexpanders.

[0243] Example 139. The energy storage system of example 138, wherein at least one of the one or more underwater compressed gas storage devices is according to any of examples 113-128

[0244] Example 140. The energy storage system of any of examples 138-139, wherein at least one of the one or more underwater compressed gas storage devices is according to any of examples 129-137

[0245] Example 141. The energy storage system of any of examples 138-140, wherein the thermal energy storage (TES) comprises:

[0246] a. one or more tanks configured to contain a thermal storage liquid at hot and cold temperatures; and

[0247] b. a thermal cycling subsystem configured to selectively cycle the thermal storage liquid among the one or more tanks during a thermal cycling process,

[0248] wherein during a thermal cycling process the thermal storage liquid is alternately heated and cooled, and wherein the same tanks are employed to contain either cold or hot thermal storage liquid.Example 142. An energy storage system, comprising:

[0249] a. one or more compressors positioned above water and configured to compress gas; b. one or more underwater compressed gas storage devices positioned in a waterbody and configured to receive the compressed gas from the one or more compressors and store the compressed gas;

[0250] c. one or more turboexpanders positioned above water and configured to receive compressed gas from the one or more underwater compressed gas storage devices and to extract mechanical work from expansion of the compressed gas;

[0251] d. a thermal energy storage (TES) positioned above water and configured to store heat from the compressed gas generated during compression and to allow transfer of heat to the compressed gas prior to expansion in the one or more turboexpanders;

[0252] e. one or more first heat exchangers positioned above water and configured to transfer heat from the compressed gas after compression to the TES;

[0253] f. one or more second heat exchangers positioned above water and configured to transfer heat from the TES to the compressed gas before expansion in the one or more turboexpanders;

[0254] wherein the TES comprises:

[0255] i. one or more tanks configured to contain a thermal storage liquid at hot and cold temperatures; and

[0256] ii. a thermal cycling subsystem configured to selectively cycle the thermal storage liquid among the one or more tanks during a thermal cycling process,

[0257] wherein during the thermal cycling process the thermal storage liquid is alternately heated and cooled, and wherein the same tanks are employed to contain either cold or hot thermal storage liquid.

[0258] Example 143. The energy storage system of example 142, wherein at least one of the one or more tanks is configured to withstand a pressure greater than the vapor pressure of the thermal storage liquid at an operating temperature, thereby preventing boiling and phase transition of the thermal storage liquid into vapor

[0259] Example 144. The energy storage system of any of examples 142-143, wherein at least one of the one or more underwater compressed gas storage devices is according to any of examples 113-128

[0260] Example 145. The energy storage system of any of examples 142-143, wherein at least one of the one or more underwater compressed gas storage devices is according to any of examples 129-137.Example 146. The energy storage system of any of examples 142-145, comprising at least one environmental heat exchanger configured to transfer heat from an environmental heat source to the compressed gas before expansion in the one or more turboexpanders.

[0261] Example 147. An underwater energy storage device comprising:

[0262] a. a metal storage tank having at least one wall and a roof comprising:

[0263] i. one or more air openings for enabling flow of air into and from said metal storage tank;

[0264] ii. one or more water openings for enabling flow of water into and from said metal storage tank; and

[0265] b. one or more air pipes connected to said one or more air openings;

[0266] said water openings are located at a bottom part of said at least one wall of said storage tank; and said one or more air openings are located at an upper part of said at least one wall of said metal storage tank and / or on said roof of said metal storage tank;

[0267] wherein said underwater energy storage device further comprises linear structural reinforcing elements for reinforcing the metal storage tank to withstand a tensile force exerted on said metal storage tank.

[0268] Example 148. The device according to example 147, wherein said storage tank comprises a plurality of tubular structures, and wherein said plurality of tubular structures are interconnected for allowing gas exchange between said plurality of tubular structures.

[0269] Example 149. A method for manufacturing an energy storage device, the method comprising:

[0270] providing a plurality of industrial tubular structures configured for storing compressed gas;

[0271] arranging said plurality of industrial tubular structures vertically extending in a clustered configuration;

[0272] fluidly inter-connecting said industrial tubular structures to enable gas and / or water flow between said industrial tubular structures; and

[0273] connecting said cluster of said plurality of industrial tubular structures to a gas pipe for enabling flow of gas into and from said cluster of said plurality of industrial tubular structures.

[0274] Example 150. An underwater energy storage system comprising:

[0275] a. one or more storage tanks, each storage tank having at least one wall and a roof, each comprising:

[0276] i. one or more air openings for enabling flow of air into and from the respective storage tank;ii. one or more water openings for enabling flow of water into and from the respective storage tank;

[0277] b. a main gas pipe configured for supplying compressed air and / or exhausting compressed air;

[0278] c. one or more internal air pipes positioned within the one or more storage tanks and fluidly connected to said main gas pipe via the one or more air openings; and

[0279] wherein said one or more water openings are located at a bottom part of said at least one wall of each storage tank; and

[0280] wherein said one or more internal air pipes enable compressed gas from the main gas pipe to flow into and / or out of the respective storage tanks.

[0281] Example 151. The system of example 150, wherein said one or more storage tanks comprises a plurality of storage tanks, and further comprising one or more interconnecting gas conduits fluidly connecting two or more of the plurality of storage tanks, wherein each interconnecting gas conduit comprises a first end positioned within a first storage tank and a second end positioned within a second storage tank, thereby enabling air flow between the first storage tank and the second storage tank.

[0282] Example 152. An underwater energy storage device, comprising:

[0283] a. one or more compressors positioned above water and configured to compress gas; b. one or more underwater compressed gas storage devices positioned in a waterbody and configured to receive the compressed gas from the one or more compressors and store the compressed gas;

[0284] wherein the one or more underwater compressed gas storage devices comprises: a. a storage tank having at least one wall and a roof comprising:

[0285] i. one or more air openings for enabling flow of air into and from said storage tank; ii. one or more water openings for enabling flow of water into and from said storage tank; and

[0286] b. one or more air pipes connected to said one or more air openings;

[0287] wherein said one or more air openings are located at an upper part of said at least one wall of said storage tank and / or on said roof of said storage tank.

[0288] c. one or more turboexpanders positioned above water and configured to receive compressed gas from the one or more underwater compressed gas storage devices and to extract mechanical work from expansion of the compressed gas;d. a thermal energy storage (TES) positioned above water and configured to store heat from the compressed gas generated during compression and to allow transfer of heat to the compressed gas prior to expansion in the one or more turboexpanders;

[0289] e. one or more first heat exchangers positioned above water and configured to transfer heat from the compressed gas after compression to the TES;

[0290] f. one or more second heat exchangers positioned above water and configured to transfer heat from the TES to the compressed gas before expansion in the one or more turboexpanders; and

[0291] g. at least one environmental heat exchanger configured to transfer heat from an environmental heat source to the compressed gas before expansion in the one or more turboexpanders.

[0292] Example 153. An energy storage system, comprising:

[0293] a. one or more compressors positioned above water and configured to compress gas; b. one or more underwater compressed gas storage devices positioned in a waterbody and configured to receive the compressed gas from the one or more compressors and store the compressed gas;

[0294] wherein the one or more underwater compressed gas storage devices comprises: a. a storage tank having at least one wall and a roof comprising:

[0295] i. one or more air openings for enabling flow of air into and from said storage tank; ii. one or more water openings for enabling flow of water into and from said storage tank; and

[0296] b. one or more air pipes connected to said one or more air openings;

[0297] wherein said one or more air openings are located at an upper part of said at least one wall of said storage tank and / or on said roof of said storage tank.

[0298] c. one or more turboexpanders positioned above water and configured to receive compressed gas from the one or more underwater compressed gas storage devices and to extract mechanical work from expansion of the compressed gas;

[0299] d. a thermal energy storage (TES) positioned above water and configured to store heat from the compressed gas generated during compression and to allow transfer of heat to the compressed gas prior to expansion in the one or more turboexpanders;

[0300] e. one or more first heat exchangers positioned above water and configured to transfer heat from the compressed gas after compression to the TES;f. one or more second heat exchangers positioned above water and configured to transfer heat from the TES to the compressed gas before expansion in the one or more turboexpanders;

[0301] wherein the TES comprises:

[0302] i. one or more tanks configured to contain a thermal storage liquid at hot and cold temperatures; and

[0303] ii. a thermal cycling subsystem configured to selectively cycle the thermal storage liquid among the one or more tanks during a thermal cycling process,

[0304] wherein during the thermal cycling process the thermal storage liquid is alternately heated and cooled, and wherein the same tanks are employed to contain either cold or hot thermal storage liquid.

[0305] Example 154. The energy storage system of any of examples 152-153, wherein said water openings are located at a bottom part of said at least one wall of said storage tank.

[0306] Example 155. The energy storage system of any of examples 152-154, wherein said underwater energy storage device further comprises peripheral edges located at a bottom part of said storage tank.

[0307] Example 156. The energy storage system of any of examples 152-155, wherein said underwater energy storage device further comprises a floor.

[0308] Example 157. The energy storage system of example 156, wherein the storage tank comprises heights at a center of said floor are higher than heights extending from said center towards walls of said storage tank for encouraging sand removal.

[0309] Example 158. The energy storage system of any of examples 152-157, wherein the storage tank comprises one or more arc shaped water openings.

[0310] Example 159. The energy storage system of any of example 158, wherein said one or more arc shaped water openings are located to be in contact with said floor configured for facilitating sand removal.

[0311] Example 160. The energy storage system of example 153, wherein the one or more tanks of the thermal energy storage (TES) are maintained at substantially the same pressure.

[0312] Example 161. A method for storing and releasing energy using an underwater energy storage device comprising at least one tubular structure positioned in a waterbody, the method comprising:

[0313] introducing compressed gas into the tubular structure during an energy storage phase;allowing at least a portion of water within the tubular structure to exit the tubular structure;

[0314] storing the compressed gas within the tubular structure above a water level defined therein;

[0315] withdrawing at least a portion of the compressed gas from the tubular structure during an energy release phase; and

[0316] allowing water to enter into the tubular structure as the compressed gas is withdrawn, wherein the tubular structure is anchored to a seabed such that the tubular structure remains substantially fixed while water exits and enters during operation.

[0317] Example 162. An underwater energy storage device comprising:

[0318] a plurality of tubular structures defining at least one internal lumen configured for storing compressed gasfor storing compressed gas;

[0319] wherein said plurality of tubular structures are arranged in a clustered configuration, and are fluidly connected to one another,

[0320] wherein at least one of the plurality of the tubular structures comprises one or more water openings, configured for one or both of: (a) water ingress; and (b) water egress.

[0321] Example 163. The underwater energy storage device of example 162, wherein the plurality of tubular structures comprises vertically extending tubular structures.

[0322] Example 164. The underwater energy storage device of any of examples 162-163, wherein at least one tubular structure of the plurality of tubular structures is positioned in a horizontal alignment relative to a seabed.

[0323] Example 165. The underwater energy storage device of any examples 162-164, wherein each of the plurality of the tubular structures comprises the one or more water openings, or at least one of the tubular structures is sealed to the outside environment and does not comprise the one or more water openings.

[0324] Example 166. The underwater energy storage device of any of examples 162-165, wherein the plurality of tubular structures operate as one unit in terms of one or both of receiving and releasing compressed gas.

[0325] Example 167. The underwater energy storage device of any of examples 162-166, wherein the plurality of tubular structures are fluidly interconnected by a plurality of connectors.Example 168. The underwater energy storage device of example 167, wherein said plurality of connectors are configured to transfer one or both of water and gas between the plurality of tubular structures.

[0326] Example 169. The underwater energy storage device of any of examples 162-168, wherein the plurality of tubular structures are connected to one or more gas connectors configured to allow gas transfer between the plurality of tubular structures.

[0327] Example 170. The underwater energy storage device of example 169, wherein the plurality of connectors comprises one or more connectors at different heights.

[0328] Example 171. The underwater energy storage device of any of examples 162-170, wherein the plurality of tubular structures are attached to one another.

[0329] Example 172. The underwater energy storage device of any of examples 162-171, comprising a cement cast positioned in between the plurality of the tubular structures.

[0330] Example 173. The underwater energy storage device of any of examples 162-172, wherein at least one of the plurality of the tubular structures comprises one or more air openings, connected to one or more air pipes configured for communicating the plurality of tubular structures to a turbomachinery unit.

[0331] Example 174. The underwater energy storage device of example 173, wherein the at least two of the plurality of the tubular structures is directly connected to the one or more air pipes.

[0332] Example 175. The underwater energy storage device of any of examples 174, wherein the at least two of the plurality of the tubular structures which are directly connected to the one or more air pipes are separated by at least one tubular structure.

[0333] Example 176. The underwater energy storage device of any of examples 162-175, wherein at least one of said tubular structures is made of one or more of metal, cement, and polymer.

[0334] Example 177. The underwater energy storage device of example 162-176, comprising at least one

[0335] weight.

[0336] Example 178. The underwater energy storage device of example 162-177, comprising more than one plurality of tubular structures arranged in a clustered configuration, wherein each of the more than one plurality of tubular structures arranged in a clustered configuration are connected to a local gas pipe configured to one or both of receive and provide gas to and from the more than one plurality of tubular structures arranged in a clustered configuration.Example 179. The underwater energy storage device of example 178, wherein each local gas pipe is connects to a main gas pipe, wherein the main gas pipe is configured to communicates the more than one plurality of tubular structures arranged in a clustered configuration to a turbomachinery unit.

[0337] Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and / or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

[0338] BRIEF DESCRIPTION OF THE SEVERAL VIEW OF THE DRAWINGS

[0339] Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

[0340] In the drawings:

[0341] Figure 1 is a simplified schematic representation of an energy storage device mounted on a surface, according to some embodiments of the invention;

[0342] Figure 2A is a simplified schematic representation of an energy storage device positioned on a seabed, according to some embodiments of the invention;

[0343] Figure 2B is a simplified schematic representation of an energy storage system, according to some embodiments of the invention;

[0344] Figure 3 is a simplified schematic representation of an energy storage device mounted on a base positioned on the seabed, according to some embodiments of the invention;

[0345] Figure 4A is a schematic representation of an energy storage device including the storage tank having a combination of structural features for reinforcing the device, according to some embodiments of the invention;

[0346] Figure 4B is a schematic representation of an underwater energy storage device comprising one or more air pipes located outside and anchored to the storage tank, according to some embodiments of the invention;Figure 4C is a schematic representation of a cross section view of an underwater energy storage device comprising one or more air pipes located inside and anchored to the storage tank, according to some embodiments of the invention;

[0347] Figure 5 is a schematic representation of an energy storage device comprising a storage tank partitioned into interconnected chambers, according to some embodiments of the invention;

[0348] Figure 6 is a schematic representation of an energy storage device comprising an exemplary peripheral clamp, according to some embodiments of the invention;

[0349] Figure 7 is a schematic representation of an energy storage device mounted on poles, according to some embodiments of the invention;

[0350] Figure 8 is a schematic representation of an energy storage device having a floorless tank mounted on poles, according to some embodiments of the invention;

[0351] Figure 9 is a schematic representation of an energy storage device comprising the storage tank with a conical shaped floor, according to some embodiments of the invention;

[0352] Figure 10 is a schematic representation of an underwater energy storage device comprising one or more water openings contacting the storage tank floor which reduces sand accumulation, according to some embodiments of the invention;

[0353] Figure 11 is a schematic representation of an energy storage device having a combination of arc and oval shaped water openings, according to some embodiments of the invention;

[0354] Figure 12 is a schematic representation of an energy storage device having a combination of structural features which promote sand accumulation prevention, according to some embodiments of the invention;

[0355] Figure 13 A is a schematic representation of an energy storage device configured for operating on an unleveled ground by having a conical surface roof, according to some embodiments of the invention;

[0356] Figure 13B is a schematic representation of an energy storage device configured for operating on an unleveled ground by having a dome shaped roof, according to some embodiments of the invention;

[0357] Figure 13C is a schematic representation of an energy storage device configured for operating on an unleveled ground by positioning the one or more air openings at an edge of the storage tank roof, according to some embodiments of the invention;

[0358] Figure 13D is a schematic representation of an energy storage device configured for operating on an unleveled ground, according to some embodiments of the invention;

[0359] Figure 13E is a schematic representation of an energy storage device configured for operating on an unleveled ground, according to some embodiments of the invention;Figure 14A is a schematic representation of an energy storage device having peripheral edges, according to some embodiments of the invention;

[0360] Figure 14B is a schematic representation of an energy storage device having peripheral edges, according to some embodiments of the invention;

[0361] Figure 15 is a schematic representation of an exemplary method of anchoring an energy storage device by distributing weights on the storage tank, according to some embodiments of the invention;

[0362] Figure 16A is a schematic representation of a method of anchoring an energy storage device by distributing one or more weights on the tank floor, according to some embodiments of the invention;

[0363] Figure 16B is a schematic representation of a method of anchoring an energy storage device by distributing one or more weights on the storage tank floor, according to some embodiments of the invention;

[0364] Figure 16C is a schematic representation of a top view of an individual weight element positioned on a floor of a tank, according to some embodiments of the invention;

[0365] Figure 17 is a schematic representation of a method for anchoring an energy storage device by distributing weights on the storage tank, according to some embodiments of the invention;

[0366] Figure 18 is a schematic representation of a method of anchoring an energy storage device by applying weights on the storage tank roof, according to some embodiments of the invention;

[0367] Figure 19 is a schematic representation of a method of anchoring an energy storage via caisson anchors, according to some embodiments of the invention;

[0368] Figure 20A is a schematic representation of a method for anchoring an energy storage via one or more anchor points, according to some embodiments of the invention;

[0369] Figure 20B is a schematic representation of a method of anchoring an energy storage via anchor points, according to some embodiments of the invention;

[0370] Figure 21 is a schematic representation of an energy storage device including a combination of structural features for facilitating submerging and anchoring of the device, according to some embodiments of the invention;

[0371] Figure 22 is a schematic representation of an exemplary base comprising poles and a plurality of beams for mounting an energy storage device, according to some embodiments of the invention;

[0372] Figure 23 is a schematic representation of an energy storage device positioned on a base with peripheral edges, according to some embodiments of the invention;

[0373] Figure 24A is a schematic representation of an energy storage device positioned on a base, according to some embodiments of the invention;Figure 24B is a schematic representation of a modular base comprising one or more discrete units for mounting an energy storage device, according to some embodiments of the invention;

[0374] Figure 25 is a schematic representation of a side view of a base positioned on a slope of the seabed, according to some embodiments of the invention;

[0375] Figure 26 is a schematic representation of a side view of an energy storage device positioned on a base comprising holes, according to some embodiments of the invention;

[0376] Figure 27 is a schematic representation of a top view of a frame enclosing fillers, according to some embodiments of the invention;

[0377] Figure 28A is a schematic representation of a side view of a base comprising a plurality of cement sacks fillers positioned on the seabed and secured by planks, according to some embodiments of the invention;

[0378] Figure 28B is a schematic representation of a connecting element for connecting two or more cement sacks, according to some embodiments of the invention;

[0379] Figure 29 is a schematic representation of a method of fixating a base comprising a cement sack to the seabed by piercing the cement sack with a piercing stick, according to some embodiments of the invention;

[0380] Figure 30 is a schematic representation of a cement sack comprising a bag containing handles, according to some embodiments of the invention;

[0381] Figure 31 is a schematic representation of cement sacks occupying space on the storage tank roof, according to some embodiments of the invention;

[0382] Figure 32 is a schematic representation of a base comprising combination of fillers, according to some embodiments of the invention;

[0383] Figure 33 A is a schematic representation of mapping inclinations in the seabed on which a base is to be positioned, according to some embodiments of the invention;

[0384] Figure 33B is a schematic representation of a topographic map of the seabed, defining a general area on which a base is to be positioned, according to some embodiments of the invention;

[0385] Figure 33C is a schematic representation of a base fabricated according to updated input data, according to some embodiments of the invention;

[0386] Figure 33D is a schematic representation of a top view of a base positioned on the seabed and in between planks, according to some embodiments of the invention;

[0387] Figure 34A-B are a flow chart of an exemplary method of fabricating a slope-fitted base to be positioned on seabed at an underwater location, according to some embodiments of the invention;

[0388] Figure 35 is a schematic representation of a method for submerging an energy storage device in the sea in a controlled manner, according to some embodiments of the invention;Figure 36 is a schematic representation of a method for submerging an energy storage device in the sea in a controlled manner, according to some embodiments of the invention;

[0389] Figure 37 is a schematic representation of a method for submerging an energy storage device in the sea in a controlled manner, according to some embodiments of the invention;

[0390] Figure 38A is a schematic representation of a method for adding weight and / or fillers during submerging of an energy storage device, according to some embodiments of the invention;

[0391] Figure 38B is a schematic representation of a method for adding weight and / or fillers during submerging of an energy storage device, according to some embodiments of the invention;

[0392] Figure 39A-B are a flow chart of an exemplary method of submerging an energy storage device and adding weights in a controlled manner, according to some embodiments of the invention;

[0393] Figure 40 is a schematic representation of a plurality of an underwater energy storage device comprising a plurality of storage tanks that have air flow communication between them positioned on one or more bases;

[0394] Figure 41 is a schematic representation of a schematic representation of an underwater energy storage device comprising a plurality of individual units storage tanks stacked one of top of the other, according to some embodiments of the invention;

[0395] Figure 42 is a schematic representation of an underwater energy storage device including a combination of storage tanks that have air and water flow communication between them, according to some embodiments of the invention;

[0396] Figure 43 is a schematic representation of an underwater energy storage device comprising a plurality of closed tanks that have air flow communication between them, according to some embodiments of the invention;

[0397] Figure 44A is a schematic representation of an underwater energy storage device comprising a plurality of storage tanks having air and water flow communication between them, according to some embodiments of the invention;

[0398] Figure 44B is a schematic representation of an underwater energy storage device comprising a plurality of storage tanks having air flow communication between them, according to some embodiments of the invention;

[0399] Figure 44C is a schematic representation of an underwater energy storage device comprising a plurality of storage tanks having air and water flow communication between them, according to some embodiments of the invention;

[0400] Figure 45A is a schematic representation of a system comprising a floating element for prevention of water from entering an air pipe positioned on a roof of the storage tank, according to some embodiments of the invention;Figure 45B is a schematic representation of a system comprising a floating element for prevention of water from entering an air pipe positioned on a roof of the storage tank, according to some embodiments of the invention;

[0401] Figure 46 is a schematic representation of a system comprising a floating element for preventing water from entering an air pipe, according to some embodiments of the invention;

[0402] Figure 47 is a schematic representation of a mobile robot for evacuating water from an air pipe, according to some embodiments of the invention;

[0403] Figure 48 is a schematic representation of a mobile robot device for evacuating water from one or more air pipes, according to some embodiments of the invention;

[0404] Figure 49 is a flow chart of an exemplary method of evacuating water from an underwater air pipe using a mobile robot device, according to some embodiments of the invention;

[0405] Figure 50 is a schematic representation of a piston for evacuation of water in an air pipe, according to some embodiments of the invention;

[0406] Figure 51A is a schematic representation of a piston for evacuation of water in an air pipe, according to some embodiments of the invention;

[0407] Figure 5 IB is a schematic representation of a piston for evacuation of water in an air pipe during piston retrieval, according to some embodiments of the invention;

[0408] Figure 52A is a schematic representation of a water evacuating system for air pipe using a water soluble piston, according to some embodiments of the invention;

[0409] Figure 52B is a schematic representation of a water evacuating system from air pipe using a water soluble piston, according to some embodiments of the invention;

[0410] Figure 53 is a flow chart of an exemplary method of evacuating water from an underwater air pipe by pushing water using a piston, according to some embodiments of the invention;

[0411] Figure 54A is a schematic representation of an energy storage device comprising a metal storage tank, according to some embodiments of the invention;

[0412] Figure 54B is a schematic representation of a top view of a star shaped column positioned in a metal storage tank, according to some embodiments of the invention;

[0413] Figure 55 is a schematic representation of an energy storage device comprising a closed metal storage tank, according to some embodiments of the invention;

[0414] Figure 56 is a schematic representation of an energy storage device comprising a tubular structure, according to some embodiments of the invention;

[0415] Figures 57A-B are a schematic representation of a cross-sectional of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention;Figure 57C is a schematic representation of a cross-sectional view of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention;

[0416] Figure 57D is a schematic representation of a cross-sectional view of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention;

[0417] Figure 57E is a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention;

[0418] Figure 57F is a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention;

[0419] Figure 57G is a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention;

[0420] Figure 57H is a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention;

[0421] Figure 58 is a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention;

[0422] Figures 59A-B are a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention;

[0423] Figure 59C is a schematic representation of a cluster of inter-connected tubular structures, according to some embodiments of the invention;

[0424] Figure 59D is a schematic representation of a cluster of inter-connected tubular structures, according to some embodiments of the invention;

[0425] Figure 60 is a schematic representation of an energy storage device comprising a plurality of clusters of inter-connected tubular structures, according to some embodiments of the invention;

[0426] Figure 61 is a schematic representation of an energy storage device comprising a horizontally positioned tubular structure, according to some embodiments of the invention;

[0427] Figures 62A-B are a schematic representation of an energy storage device comprising a cluster of generally parallel horizontally positioned tubular structures, according to some embodiments of the invention;

[0428] Figures 63A-B are a schematic representation of an energy storage device comprising a cluster of stacked horizontally positioned tubular structures, according to some embodiments of the invention;

[0429] Figure 64 is a schematic representation of an energy storage device comprising a storage tank and one or more internal gas pipes, according to some embodiments of the invention;

[0430] Figure 65 is a schematic representation of an energy storage device comprising a plurality of storage tanks housing one or more internal gas pipes, according to some embodiments of the invention;Figure 66 is a schematic representation of an energy storage device comprising a plurality of interconnected storage tanks, according to some embodiments of the invention;

[0431] Figure 67 A is a simplified block diagram of an exemplary system for storing energy and extracting work from a compressed gas energy storage system, according to some embodiments of the invention;

[0432] Figure 67B is a schematic representation of an exemplary system for compressing gas, storing the compressed gas in an underwater storage tank, and extracting work from the compressed gas, according to some embodiments of the invention;

[0433] Figure 67C is a schematic representation of an exemplary system for compressing gas, storing the compressed gas in an underwater storage tank, and extracting work from the compressed gas, according to some embodiments of the invention;

[0434] Figure 67D, showing a schematic representation of exemplary a thermal exchange systems, according to some embodiments of the invention;

[0435] Figures 68A-C are a schematic representation of an exemplary storage tank system for storing compressed gas in an underwater location, according to some embodiments of the invention; and Figures 68D-G are schematic representations of exemplary anchoring configurations for a storage tank system for storing compressed gas in an underwater location, according to some embodiments of the invention.

[0436] DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

[0437] The present invention, in some embodiments thereof, relates to underwater energy storage and, more particularly, but not exclusively, to underwater energy storage of compressed air. As used herein, the term ”air” means any type of gas or combination of gases.

[0438] Overview

[0439] An aspect of some embodiments of the invention relates to storing energy in underwater environments. In some embodiments, energy storage is done in dedicated underwater energy storage devices configured for storing compressed air. In some embodiments, the underwater energy storage devices store energy during periods of high energy production rate. Optionally, the energy is derived from renewable sources, for example sunlight and wind which are not continuously available and, in some embodiments, the production and storing of energy occurs during periods in which the renewable energy sources are in high availability. In some embodiments, the compressed air is used as an energy source, optionally during periods of low renewable energy sources availability. In some embodiments, underwater energy storage devices comprise at least one tank configured for storing the compressed air. In some embodiments, underwater energy storage devices are configured forsustaining the unique underwater conditions, such as differential pressure between the tank and the outside water environment, water currents and sand originating from the seabed. In some embodiments, the underwater energy storage devices comprise one or more reinforcements configured to reinforce at least part of the tank. A potential advantage of reinforcing at least part of the tank is that it potentially avoids damages to the tank due to the underwater pressure differences between the tank and the outside water environment at different parts of the tank. In some embodiments, the underwater energy storage devices comprise at least one anchoring means, for example, added weights, the self-weight of the energy storage device or tank, cables, anchors including caisson anchors, and foundations configured for anchoring the tank to the seabed. In some embodiments, a potential advantage of providing at least one anchoring means to the tank is that it potentially avoids the movement of the tank due to one or more of: the buoyancy of the tank, the water currents and / or a slope in the seabed. In some embodiments, the underwater energy storage devices comprise one or more openings configured to allow the entry and exit of sea water to and from the tank. In some embodiments, a potential advantage of the one or more openings is that they additionally potentially allow for the sand found in sea water to enter and exit (especially exit) the tank. In some embodiments, optionally, the tank is positioned on an elevating base, which elevates the tank from the seabed and allows positioning a plurality of the tanks in the same height, where more than one tank is used. In some embodiments, a potential advantage of positioning the tank on a base is that it potentially reduces the entry of sand into the tank. In some embodiments, the tank is designed to facilitate the exit of sand from within the tank thereby potentially avoiding the accumulation of sand within the tank. In some embodiments, this is done by providing the floor of the tank with an inclination that encourages the movement of sand towards the one or more openings. As used herein, the term ’’floor” means a bottom part of the tank that encloses the tank. In some embodiments, the tank is connected to air pipes for communicating the tank with either a receiver of the compressed gas or a provider of the compressed gas. In some embodiments, a portion of the air pipes that is in proximity to the energy storage device is anchored to the tank. In some embodiments, a potential advantage of anchoring the portion of the air pipes that is in proximity to the energy storage device to the tank is preventing fragile connection of the air pipes to the tank. In some embodiments, the portion of the air pipe anchored to the tank has a spiraling shape. In some embodiments, potential advantages of the portion of the air pipe anchored to the tank having a spiraling shape are the following: prevention of acute or right angles in the air pipe which may lead to mechanical failure due to stress concentration in the water environment having water currents and prevention of turbulent air flow inside the air pipe. In some embodiments, optionally, the tank is equipped with peripheral edges for preventing from natural occurring turbulences generated at the part of the energy storage device meeting the sand to cause unwanteddowncutting or moving of sand from the seabed to create pits in the underwater surface. In some embodiments, optionally, the tank is equipped with peripheral edges having an inclination configured for reducing the level around the tank. In some embodiments, potential advantages of equipping the tank with peripheral edges is potentially securing the leveling and stability of the tank and potentially preventing sand accumulation in the tank. In some embodiments, during the submerging of the energy storage device, for example by a floating crane and / or winch, air is supplied to the tank for increasing a buoyancy force which counterbalances a gravitational force. In some embodiments, a potential advantage of supplying air to the tank during submerging is enabling the use of, for example, a small floating crane and / or winch configured for lifting lighter loads. In some embodiments, weights are added during the lowering of the energy storage device to a submerging site. In some embodiments, a potential advantage of adding weights during the lowering of the energy storage device to a submerging site is avoiding either a complex mobilizing of the energy storage device to a submerging site or a complex procedure of adding weights when the energy storage device is located on the seabed. Optionally or additionally, weights are added before the lowering of the energy storage device to a submerging site. Optionally or additionally, weights are added at the submerging site.

[0440] An aspect of some embodiments of the invention relates to the use of prefabricated industrial structures for compressed gas storage, potentially benefiting from industrial manufacturing processes to reduce costs and improve structural resilience.

[0441] In some embodiments, the industrial structures are repurposed from pre-existing industrial components - such as pipes, structural tubing, or other manufactured hollow structures.

[0442] In some embodiments, a cover is added to enclose the open top of the industrial structure, providing sealing, weight distribution, and additional reinforcement. In some embodiments, the cover which is flat or dome-shaped, is attached through welding, gluing, or other industrial fastening methods. Optionally, a weighted platform or anchoring system may be added to prevent floating.

[0443] An aspect of some embodiments of the invention relates to utilizing a plurality of tubular structures for storing compressed gas. Instead of large-diameter pressure vessels, which present significant engineering and logistical challenges, the system comprises a clustered arrangement of smaller tubular structures that are fluidly interconnected to function as a unified storage unit. These structures are designed to withstand underwater conditions, including pressure differentials, water currents, and seabed instability. In some embodiments, anchoring mechanisms, such as weighted platforms, stackable weights, and anchoring rods, help secure the system in place. In some embodiments, gas and water exchange within the system is facilitated by strategically positioned connectors and air pipes, ensuring efficient operation. Optionally or additionally, multiple clusters oftubular structures can be interconnected via local and main gas pipes, potentially enabling scalable energy storage.

[0444] An aspect of some embodiments of the invention relates to an underwater energy storage system comprising one or more storage tanks, each housing one or more internal air pipes fluidly connected to a main gas pipe. Each internal air pipe extends within the respective storage tank and is configured to enable the flow of compressed gas into and from the tank.

[0445] In some embodiments, multiple storage tanks are interconnected via gas conduits to form a shared gas volume, facilitating modular and scalable energy storage.

[0446] Water openings located at lower portions of the storage tanks allow controlled water ingress and egress, maintaining pressure balance during charging and discharging operations. Optionally or additionally, water removal units are provided to prevent water accumulation within gas conduits and main pipes, ensuring continuous and efficient system operation. A potential advantage of the one or more internal air pipes fluidly connected to a main gas pipe is facilitating a cost-effective construction of the energy storage device.

[0447] An aspect of some embodiments of the invention relates to storing compressed gas in underwater tubular structures (e.g., elongated pipe)positioned horizontally on a seabed. In some embodiments, the system comprises one or more tubular structures (for example, elongated pipes) laid along the seabed. In some embodiments, the one or more tubular structures are made of commercially available pipes. A potential advantage of the one or more tubular structures made of commercially available pipes is easiness of production. The one or more tubular structures are connected at an upper portion to an air conduit, which allows compressed gas to be transferred to and from a land-based and / or an offshore location. Additionally, the one or more tubular structures comprise an opening located a lower portion of the one or more tubular structures for allowing water to enter and / or exit as gas volume within the one or more pipes changes. In some embodiments, optionally, weights are attached to and / or placed over the one or more tubular structures to potentially reduce and / or prevent the one or more tubular structures from floating, for example when the one or more tubular structures are filled with compressed gas. In some embodiments, other means are used to ensure that the tubular structures will stay under water in any situation (for example, when empty or when filled with compressed gas). A potential advantage of the one or more elongated pipes is scalability and costeffectiveness compared to rigid concrete or metallic tanks.

[0448] An aspect of some embodiments of the invention relates to underwater compressed gas storage structures (e.g., as described herein), having the ability to interface with substnially any system configured to generate compressed gas and / or to utilize compressed gas. In some embodiments, the underwater storage tanks and / or tubular structures are configured to receive compressed gas from anysuitable compressed gas generation system, including but not limited to compressor units, industrial compression facilities, power plant auxiliary systems, renewable energy conversion systems, gas liquefaction or separation systems, and mobile or offshore compression units. In some embodiments, the underwater storage tanks are further configured to supply compressed gas to any system requiring pressurized gas, including but not limited to systems for extracting mechanical work, generating electricity, driving turbines or expanders, operating pneumatic equipment, supporting industrial processes, or performing energy recovery operations. Accordingly, the underwater storage structures described herein are not limited to a specific energy storage cycle or work extraction configuration, and may function as a bidirectional compressed gas reservoir capable of both receiving and delivering compressed gas in accordance with operational demands.

[0449] An aspect of some embodiments of the invention relates to an underwater compressed gas storage system configured to supply compressed gas to, and receive compressed gas from, an energy conversion system comprising shared-use thermal storage tanks. In some embodiments, one or more underwater gas storage tanks and / or tubular structures (e.g., as described herein) are fluidly connected to a compression subsystem and to a generation subsystem, wherein the energy conversion system further comprises a thermal energy storage (TES) including a plurality of shared-use thermal storage tanks configured for alternating storage of heated and cooled thermal storage liquid.

[0450] In some embodiments, during a compression phase, compressed gas delivered from the underwater storage tanks to a compression heat exchanger transfers heat to a thermal storage liquid, which is circulated into one of the plurality of shared-use thermal storage tanks that is initially substantially empty. In some embodiments, during a generation phase, compressed gas supplied from the underwater storage tanks is heated prior to expansion by circulating heated thermal storage liquid withdrawn from one of the shared-use thermal storage tanks through a pre-expansion heat exchanger, and / or the resulting cooled liquid is delivered into another storage tank that is initially substantially empty.

[0451] In some embodiments, the plurality of shared-use thermal storage tanks are not permanently dedicated to hot-only or cold-only operation, but are selectively operable to store either heated or cooled thermal storage liquid at different times during system operation. In some embodiments, the system is configured such that at least one thermal storage tank remains substantially empty during operation, thereby potentially cyclical thermal transfer without intermixing of liquids at different temperatures. A potential advantage of integrating underwater compressed gas storage tanks with a shared-use thermal storage architecture includes reduction in the total number of thermal storage tanks required, decreased facility footprint, simplified piping and / or valve infrastructure, reduced insulation requirements, and / or improved modular scalability of the overall energy storage system.An aspect of some embodiments of the invention relates to integrating an underwater compressed gas energy storage system with external thermal energy sources for pre-expansion heating of compressed gas. A potential advantage of using external heat for heating the compressed gas includes utilizing readily available and low-cost thermal energy sources that would otherwise be wasted. In some embodiments, the external heat source comprises industrial waste heat generated by high-temperature processes, including but not limited to steel manufacturing plants, glass production facilities, ceramic kilns, and / or cement plants. Many such industrial facilities employ high-temperature furnaces, reheating furnaces, smelters, kilns, and similar thermal processing units that operate at elevated temperatures and / or require substantial cooling infrastructure to dissipate excess heat.Such industrial facilities often expend significant efforts and / or infrastructure resources to remove excess heat from their processes, and integration of the compressed gas energy storage system described herein potentially allow recovery and / or beneficial use of such waste heat, having the potential advantage of improving overall energy efficiency of both the energy storage system and the associated industrial facility.

[0452] In some embodiments, external heat additionally or alternatively comprises waste heat from power plants, combined-cycle facilities, nuclear reactors, desalination plants, or other large-scale thermal installations. More generally, the external heat source may comprise any thermal energy source capable of transferring heat to the compressed gas and / or to a thermal storage liquid at a temperature suitable for pre-expansion heating. In some embodiments, geothermal heat sources, natural hot springs, elevated seawater temperatures under specific environmental conditions, and / or other naturally occurring thermal reservoirs may be utilized as supplementary heat inputs.

[0453] Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and / or methods set forth in the following description and / or illustrated in the drawings and / or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

[0454] Compressed air energy storage is a way to store energy generated during periods of energy production surplus for use during periods of high energy demands. This enables to balance the supply and demand of energy for energy production facilities without altering the energy production rate, for example, nuclear plants can store energy with compressed air energy storage during periods of low energy demands and use the stored energy during periods of high energy demand while maintaining a constant energy production rate. Furthermore, compressed air energy storage enables storing energy generated from natural resources such as sunlight, wind, rain, waves and tides for use during periods of low availability of the natural resources and / or high energy demands. It has been proposed to storecompressed air in a high-pressure environment such as deep underwater to avoid the costs of high-pressure vessels for storing the compressed air.

[0455] Underwater energy storage devices operate in water environment and, as such, experience environmental conditions such as water currents and sand originating from the seabed. Furthermore, pressure is exerted on the device due to the weight of the water. Those conditions are problematic in underwater storage systems.

[0456] Referring now to Figure 1, showing a simplified schematic representation of an underwater energy storage device mounted on a surface, according to some embodiments of the invention.

[0457] In some embodiments, there is provided an underwater energy storage structure including a rigid storage tank 100 comprising at least one storage tank wall 103 and a storage tank roof 105 having a thickness, for example, from about 0.005 meters to about 5 meters, optionally from about 0.05 to about 2 meters, optionally from about 0.1 to about 3 meters. In some embodiments, the storage tank 100 has a width, for example, from about 10 meters to about 100 meters, optionally from about 15 meters to about 60 meters. In some embodiments, the storage tank 100 has a height, for example, from about 2 meters to about 30 meters, optionally from about 7 meters to about 15 meters. In some embodiments, a potential advantage of the rigid storage tank 100 is that it is durable to underwater conditions, for example water pressure differences between the outside environment and the inside environment, water currents, erosion for example chemical, biological or mechanical and waves. In some embodiments, the storage tank 100 further comprises one or more apertures 102 for enabling flow of air into and out of the storage tank 100. In some embodiments, the storage tank 100 further comprises one or more apertures 104 through which water freely flows into and out of the storage tank 100. In some embodiments, the storage tank 100 disclosed herein is configured for storing compressed air and / or water, and enabling the releasing or receiving of air from and to the storage tank 100. In some embodiments, the compressed air stored in the storage tank 100 is at pressure equilibrium with water contacting the compressed air in the storage tank 100. In some embodiments, the storage tank 100 is located at an underwater depth, for example, from about -100 meters to about -5000 meters depth, optionally from about -50 to -2000 meters depth, optionally from about -100 to -3000 meters depth. It is known that water is significantly denser compared to air such that air reside above water. In some embodiments, the one or more apertures 102 configured for air flow are located in the upper part of the storage tank 100. In some embodiments, during release of air from the storage tank 100, air flows upward to exit the storage tank 100 via the one or more air apertures 102, during which water enters the storage tank 100 via the one or more water apertures 104 to compensate for the change in air volume. In some embodiments, the storage tank 100 is mounted on a surface 106.In some embodiments, the surface 106 is the bottom of the sea (seabed), as shown for example in Figures 2A-B, and, in some embodiments the surface 106 is a base, as shown for example in Figure 3.

[0458] In some embodiments, the storage tank 100 is substantially sealed against ingress of water from the surrounding underwater environment and is configured to allow gas flow while preventing water entry. In such embodiments, the storage tank 100 does not comprise water apertures permitting free water communication with the surrounding environment. Optionally, the storage tank 100 is hermetically sealed except for the one or more apertures 102 configured for enabling controlled inflow and / or outflow of compressed gas.

[0459] Referring now to Figure 2A, showing a simplified schematic representation of an underwater energy storage device positioned on a seabed, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 200 includes the storage tank 100 comprising one or more water openings 204 having, for example, a curved shape. In some embodiments, a potential advantage of curved shaped water openings is preventing formation of cracks in the openings due to the equal distribution of stress applied by the self-weight of the storage tank 100 over the opening, instead of concentrating at any one point in the opening as would happen for example, in an opening having sharp angles (triangles, squares, etc.). In some embodiments, the storage tank 100 comprises one or more air openings 206. In some embodiments, the one or more air openings 206 are connected to one or more air pipes 202 for communicating the storage tank 100 to a turbomachinery unit (not shown in figure), for example a compressor which supplies the compressed air or a generator that uses the compressed air for energy production, which will be further explained in Figure 2B. In some embodiments, an air opening from the one or more air openings 206 has a width, for example, from about 5 cm to about 200 cm, optionally from about 20 cm to about 120 cm, optionally from about 50 cm to about 150 cm. In Figures 2A-B, the device 200 is mounted or positioned on the seabed 250.

[0460] Referring now to Figure 2B, showing a simplified schematic representation of an underwater energy storage system, according to some embodiments of the invention. In some embodiments, the storage tank 100 is fluidly coupled via the one or more air pipes 202 to a turbomachinery unit 208 to selectively provide air to the storage tank 100 and selectively receive air from the storage tank 100 and extract useful work form the air. In some embodiments, the turbomachinery unit 208 is a compressor which uses energy to increase the pressure of air by reducing its volume, the compressed air is thereafter supplied to the storage tank 100 and stored inside the storage tank 100. In some embodiments, the turbomachinery unit 208 is an expender device. In some embodiments, thecompressed air received from the storage tank 100 is expended in the expender to drive a turbine (not shown in figure) thus converting the potential energy of the compressed gas into mechanical work.

[0461] Referring now to Figure 3, showing a simplified schematic representation of an underwater energy storage device mounted on a base positioned on the seabed, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 300 includes the storage tank 100. In some embodiments, the storage tank 100 is mounted on a base 302. In some embodiments, mounting the storage tank 100 on a base 302 elevates the storage tank 100 in relation to the seabed and potentially allows for leveling the storage tank 100 in view of an inclined seabed surface in which the device 300 is positioned. In Figure 3, the base 302 is positioned on the seabed 250.

[0462] Exemplary storage tanks

[0463] Referring now to Figure 4A, showing a schematic representation of an underwater energy storage device including the storage tank having a combination of structural features for reinforcing the device, according to some embodiments of the invention. In some embodiments, pressure differences occur between the compressed air within the storage tank 100 and pressure of water from outside the storage tank 100. In some embodiments, the storage tank 100 is made of high strength materials comprising for example iron, steel or other metals, concrete, iron incorporated within concrete, polymer and / or other high strength materials or combination of materials. In some embodiments, a potential advantage of making the storage tank 100 of high strength materials is that it avoids the generations of cracks in the storage tank 100 due to the difference in the pressure between the external environment and the internal environment. In some embodiments, the compressed air stored in the storage tank 100 is at pressure equilibrium with water contacting the compressed air in the storage tank 100. In some embodiments, the compressed air exerts a uniform pressure on the storage tank 100. It is known that the pressure exerted by the water increases with an underwater depth due to the incremental weight of the water. In some embodiments, the pressure exerted on the storage tank 100 by the water outside changes along the height of the storage tank 100 according to the underwater depth. In some embodiments, the pressure exerted on the storage tank 100 by the water outside along the height of the storage tank 100 is such that an external pressure in an upper portion of the storage tank 100 is lower than a pressure in a lower part of the storage tank 100. In some embodiments, a net pressure exerted on the storage tank 100 results from the differences between the pressure exerted by the water outside and the opposite direction pressure exerted by the compressed air inside the storage tank 100. In some embodiments, the net pressure exerted on the storage tank 100 changes along the height of the storage tank 100. In some embodiments, the net pressure exerted on the storage tank 100 increases with the height of the storage tank 100 such that the net pressure in an upper portion of the storage tank 100 is higher than the net pressure in a lower part of the storage tank100. In some embodiments, the net pressure exerted on the storage tank 100 operates in an outward direction. In some embodiments, exertion of a net pressure on the storage tank 100 in an outward direction may harm the structural stability of the storage tank 100, for example, leading to generation of cracks in the storage tank 100. In some embodiments, local reinforcement is desired for counterbalancing the net pressure exerted on the storage tank 100, optionally in the upper part of the storage tank 100 where the net pressure is higher. In some embodiments, the local reinforcement is provided in a form of peripheral clamps attached to the storage tank 100 as shown for example in Figure 6, and, in some embodiments, a heterogeneous composition of the storage tank 100 configured for reinforcing a discrete area in the storage tank 100 is provided. In some embodiments, the storage tank 100 is made of a composition comprising a heterogeneous distribution of materials, for example the upper portion of the storage the storage tank 100 comprises more iron than a lower portion of the storage tank 100. In some embodiments, a potential advantage of the storage tank 100 having the upper portion comprising more iron than the lower portion is enhancing the structural stability of the upper part of the storage tank 100 which experiences a higher net pressure. Optionally, the storage tank 100 is made of a composition comprising a homogenous distribution of materials. In some embodiments, optionally, the storage tank 100 is provided with at least one reinforcement configured for enhancing the structure of the storage tank 100. In some embodiments, the storage tank 100 is coated with an external coating 402 configured for enhancing the mechanical stability of the storage tank 100 and avoiding formation of cracks. In some embodiments, the external coating 402 is made of, for example, fiberglass, carbon, epoxy fibers and / or metals. In some embodiments, a thickness of the external coating 402 gradually increases with the height of the storage tank 100 to counterbalance the gradually changing net pressure along the height of the storage tank 100. In some embodiments, the thickness of the external coating 402 is uniform. In some embodiments, the external coating 402 is applied in discrete parts of the storage tank 100, for example in the upper part of the storage tank 100. In some embodiments, the storage tank 100 is coated with an internal coating 404 configured for sealing the internal surface of the storage tank 100. In some embodiments, the internal coating 404 is characterized by being a durable, waterproof and oxygen inert material or combination of materials. In some embodiments, the internal coating 404 is for example one or more of Polyurea, epoxy and polyethylene. In some embodiments, potential advantages of an internal coating 404 configured for sealing the storage tank 100 internally are potentially preventing oxidation of the iron in the storage tank 100 by oxygen in the compressed air which may harm the mechanical stability of the storage tank 100, and potentially preventing air leakage via cracks in the storage tank 100.Referring now to Figure 4B, showing a schematic representation of an underwater energy storage device comprising one or more air pipes located outside and anchored to the storage tank, according to some embodiments of the invention. In some embodiments, the connection of the one or more air pipes 202 to the storage tank 100 in the one or more openings 206 can be affected by movement of the one or more air pipes 202. In some embodiments, movement of the one or more air pipes 202 due to, for example water flows can lead to failure in the connection of the one or more air pipes 202 to the storage tank 100 in the one or more openings 206. In some embodiments, an energy storage device 430 comprises the storage tank 100 comprising the one or more air openings 206 which are connected to the one or more air pipes 202. In some embodiments, a portion of the one or more air pipes 202 which is in proximity to the one or more air openings 206 is anchored to the storage tank 100. In some embodiments, a potential advantage of a portion of the one or more air pipes 202 which is in proximity to the one or more air openings 206 being anchored to the storage tank 100 is enabling a secure of the connection of the one or more air pipes 202 to the storage tank 100 in the one or more openings 206 by minimizing movement of the portion of the one or more air pipes 202 which is in proximity to the one or more air openings 206. In some embodiments, the portion of the one or more air pipes 202 which is in proximity to the one or more air openings 206 contacts an exterior of the storage tank 100. In some embodiments, the portion of the one or more air pipes 202 which is in proximity to the one or more air openings 206 follows a shortest path to a bottom part of the storage tank 100, for example having an L shape. In some embodiments, optionally, the portion of the one or more air pipes 202 which is in proximity to the one or more air openings 206 has a spiraling shape, eliminating sharp angles. In some embodiments, potential advantages of the portion of the one or more air pipes 202 which is in proximity to the one or more air openings 206 having a spiraling shape are the following: preventing turbulent air flow inside the one or more air pipes 202 and preventing failure in the one or more air pipes 202 which may occur due to stress concentration.

[0464] In some embodiments, the portion of the one or more air pipes 202 which surround a portion of the storage tank 100 is anchored to the storage tank 100. In some embodiments, a potential advantage of the portion of the one or more air pipes 202 which is in proximity to the one or more air openings 206 being anchored to the storage tank 100 is enhancing the structural durability of the connection of the one or more air pipes 202 to the storage tank 100 and reducing the probability to failure in the connection located in the one or more air openings 206.

[0465] Referring now to Figure 4C, showing a schematic representation of a cross section view of an underwater energy storage device comprising one or more air pipes located inside and anchored to the storage tank, according to some embodiments of the invention. In some embodiments, the energy storage device 460 comprises the storage tank 100, which houses a portion of the one or more air pipes202, the portion being in proximity one or more air pipe opening 462 located in a distal end of the one or more one or more air pipes 202. In some embodiments, the portion of the one or more air pipes 202 is anchored to the storage tank 100. In some embodiments, the portion of the one or more air pipes 202 anchored to the storage tank 100 contacts the interior of the storage tank 100. In some embodiments, the portion of the one or more air pipes 202 anchored to the storage tank 100 follows a shortest path to a bottom part of the storage tank 100, for example having an L shape. In some embodiments, optionally, the portion of the one or more air pipes 202 anchored to the storage tank 100 and contacting the interior of the storage tank 100 has a spiraling shape, optionally originating from the one or more air openings 206. In some embodiments, the one or more one or more air pipes 202 is connected to the one or more air openings 206 for enabling flow of compressed air to and from the storage tank 100. In some embodiments, a potential advantage of the portion of the one or more air pipes 202 which is in proximity to the one or more air pipe openings 462 being anchored to the storage tank 100 is enhancing the structural durability of the connection of the one or more air pipes 202 to the storage tank 100 and reducing the probability to failure in the connections located in the one or more air openings 206.

[0466] Referring now to Figure 5, showing a schematic representation of an underwater energy storage device comprising a storage tank partitioned into interconnected chambers, according to some embodiments of the invention. In some embodiments, the storage tank 100 comprising a floor (not shown in figure) is internally partitioned into two or more chambers 502 interconnected by one or more internal openings 504 that permit flow of air and water between the chambers 502. In some embodiments, a potential advantage of the partitioning is potentially providing additional reinforcements to the storage tank 100 structure. In some embodiments, the one or more internal openings 504 are located on one or more of: a top portion of the partition, a middle portion of the partition and a bottom portion of the partition.

[0467] Referring now to Figure 6, showing a schematic representation of an underwater energy storage device comprising an exemplary peripheral clamp, according to some embodiments of the invention. In some embodiments, in view of the differences in the net pressure exerted on the storage tank 100 along the height of the storage tank 100, a localized reinforcement solution is desired. In some embodiments, reinforcement of high pressure regions is obtained by using one or more peripheral clamps 602 (one shown in Figure 6) tightly fastened around the storage tank 100. In some embodiments, the one or more peripheral clamps 602 are configured for counterbalancing a net pressure exerted on the storage tank 100. In some embodiments, the one or more peripheral clamps 602 are configured to withstand a net pressure operating on the storage tank 100. In some embodiments, the one or more peripheral clamps 602 apply local pressure on the storage tank 100. Insome embodiments, a clamp from the one or more peripheral clamps 602 comprises one or more rigid elements 604 and one or more adjustable elements 606 for connecting and fastening the one or more rigid elements 604. In some embodiments, the one or more rigid elements 604 comprise belts comprising, for example, metal such as steel, polymer, composite material comprising reinforcing fibers and / or other high strength materials. In some embodiments, the one or more adjustable elements 606 comprise wires or cables made of for example metal or polymer.

[0468] In some embodiments, the storage tank 100 comprises a floor as shown for example in Figure 7, and, in some embodiments the storage tank 100 is floorless, as shown for example in Figure 8.

[0469] Referring now to Figure 7, showing a simplified schematic representation of an underwater energy storage device mounted on poles, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 700 including the storage tank 100, optionally comprising a storage tank floor 702, is mounted on a base 302 comprising poles 704. In some embodiments, a potential advantage of mounting the underwater energy storage device 700 on the poles 704 is that it potentially reduces sand accumulation in the storage tank 100 via the one or more water openings 204 and potentially prevents the underwater energy storage device 700 from being buried in sand. In some embodiments, the storage tank floor 702 is made of for example concrete, metal or combination of concrete and metal. In some embodiments, the poles 704 allow water currents to flow under the device 700 and move sand. In some embodiments, the storage tank floor 702 is flat. Optionally, the storage tank floor 702 is conical shaped as shown for example in Figure 12.

[0470] Referring now to Figure 8, showing a schematic representation of an underwater energy storage device having a floorless tank mounted on poles, according to some embodiments of the invention. In some embodiments, device 800 includes the storage tank 100 being floorless and having an opening 802 located in the bottom of the storage tank 100 for receiving and expelling water to and from the storage tank 100. In some embodiments, a potential advantage of having a water opening 820 located in the bottom of the storage tank 100 is preventing sand clogging of the one or more water apertures 104 due to its location in the bottom of the storage tank 100. In some embodiments, the device 800 is mounted on poles 704 for elevating the device and allowing water flow via the water opening 802.

[0471] Referring now to Figure 9, showing a schematic representation of an underwater energy storage device comprising the storage tank with a conical shaped floor, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 900 comprising the storage tank 100 includes a conical shaped floor 902 in which heights at the center are higher than heights extending from the center towards the at least one storage tank wall 103. The conical shaped floor 902 has a slope for facilitating expulsion of sand sediment in the tank floor thatis adjacent to the one or more water openings 204 via the one or more water openings 204. In some embodiments, the slope has an angle for facilitating sand expulsion, for example the angle is from about 20 degrees to about 70 degrees, optionally from about 30 degrees to about 30 degrees to 50 degrees, optionally from about 40 degrees to about 60 degrees.

[0472] Exemplary water openings

[0473] In some embodiments, the one or more water openings 204 allow water to flow to and from the storage tank 100. However, since water currents carry sand sediments, the one or more water openings 204 also facilitate accumulation of sand in the storage tank 100. In some embodiments, shape design of the one or more water openings 204 promotes sand evacuation from the storage tank 100, for example arc, spherical, elliptic or any other shape facilitating water transfer or combination of shapes. In some embodiments, the shape of the one or more water openings 204 is such that it comprises no acute comers or no comers at all, which potentially prevents the generation of cracks along the border of the opening due to the equal distribution of stress applied by the self- weight of the storage tank 100, instead of concentrating at any one point on the border of the opening, like it could happen on an acute comer. In some embodiments, the shape for the one or more water openings 204 is characterized by having a minimal height for maximizing the potential volume for storing compressed air in the storage tank 100 while having an accumulative area for enabling sufficient water flow rate to the storage tank 100 from the outside water environment.

[0474] Referring now to Figure 10, showing a schematic representation of an underwater energy storage device comprising one or more water openings contacting the storage tank floor which reduces sand accumulation, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 1000 comprises the storage tank 100 including one or more arc shaped water openings 1002 wherein a wide part of the arc shaped water opening 1002 is located adjacent to the storage tank floor 702 for allowing sedimented sand to evacuate via the one or more openings 1002. In some embodiments, a potential advantage of arc shaped water openings is potentially maximizing evacuation of sand that is sedimented and accumulated on the storage tank floor 702. In some embodiments, the one or more arc shaped water openings 1002 have a spherical, elliptic or any other shape facilitating water transfer or combination of shapes.

[0475] Referring now to Figure 11, showing a schematic representation of an underwater energy storage device having a combination of arc and oval shaped water openings, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 1100 comprises the storage tank 100 including a combination of the one or more arc shaped water openings 1002 and one or more oval shaped water openings 1102. In some embodiments, a potential advantage of combining two or more shapes for the one or more water openings 204 having different beneficialfeatures is providing a storage tank 100 tailor made for a specific environment, for example, for an environment comprising both sand and rocks, the storage tank 100 could enable sufficient sand evacuation with the one or more arc shaped openings 1002 which promotes sand evacuation while preventing the formation of cracks with the oval shaped openings 1102 having no acute angles and thus facilitate optimal performance of the underwater energy storage device 1100 in the specific environment comprising both sand and rocks.

[0476] Referring now to Figure 12, showing a schematic representation of an underwater energy storage device having a combination of structural features which promote sand accumulation prevention, according to some embodiments of the invention. In some embodiments, distancing the storage tank 100 from the seabed 250 by elevating assists in prevention of sand accumulation, however it does not ensure elimination of sand accumulation altogether since sand is carried in the water and may accumulate in the storage tank 100. For that reason, combination of features designed for sand accumulation prevention is desired. In some embodiments, an underwater energy storage device 1200 includes the storage tank 100 comprising the one or more arc shaped water openings 1002 wherein the wide part of the opening is located adjacent to the conical shaped floor 902. In some embodiments, the storage tank 100 is mounted on a base comprising elevating poles 704, the poles 704 being positioned on the seabed 250.

[0477] Referring now to Figure 13 A, showing a schematic representation of an underwater energy storage device configured for operating on an unleveled ground by having a conical surface roof, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 1300 includes storage tank 100 comprising a conical surface roof 1302 and one or more air openings 206 in which at least one air opening from the one or more air openings 206 is located at a top part of the conical surface roof 1302. In some embodiments, the storage tank 100 is positioned on a ground 1304, for example the seabed 250. In some embodiments, the storage tank 100 is leveled. In some embodiments, the storage tank 100 undesirably moves and becomes unleveled. In some embodiments, the ground 1304 is unleveled and the storage tank 100 is unleveled. In some embodiments, a potential advantage of having the conical surface roof 1302 in which the at least one air opening from the one or more air openings 206 is located at a top part of the conical surface roof 1302 when the storage tank 100 is not leveled is preventing air from being caged in a top corner in the storage tank 100 during and following air release, thereby allowing the proper flow of air from and to the storage tank 100. In some embodiments, a further potential advantage of having the conical surface roof 1302 is high pressure resistance compared to a flat roof due to the curved surface of the conical surface roof 1302.In some embodiments, the underwater storage device 1300 is anchored to the seabed 250 by foundations (not shown in figure). In some embodiments, the foundations are made of for example concrete and / or steel piles.

[0478] In some embodiments, the underwater energy storage device 1300 further comprises an upper banister (not shown) located on top the conical shaped roof 1302. In some embodiments, a space defined by the upper banister above the conical surface roof 1302 is partitioned into a plurality of chambers to provide reinforcement to the at least one storage tank wall 103 and the conical surface roof 1302 of the storage tank 100. In some embodiments, the space defined by the upper banister is filled with weights as is further described in Figure 17.

[0479] Referring now to Figure 13B, showing a schematic representation of an underwater energy storage device configured for operating on an unleveled ground by having a dome shaped roof, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 1320 includes storage tank 100 comprising a dome shaped roof 1306 and one or more air openings 206 in which at least one air opening from the one or more air openings 206 is located at a top part of the dome shaped roof 1306. In some embodiments, the storage tank 100 is positioned on a ground 1304, for example the seabed 250. In some embodiments, the storage tank 100 is leveled. In some embodiments, the storage tank 100 undesirably moves and becomes unleveled. In some embodiments, the ground 1304 is unleveled and the storage tank 100 is unleveled. In some embodiments, a potential advantage of having the dome shaped roof 1306 in which the at least one air opening from the one or more air openings 206 is located at a top part of the dome shaped roof 1306 when the storage tank 100 is not leveled is preventing air from being caged in a top corner in the storage tank 100 during and following air release, thereby allowing the proper flow of air from and to the storage tank 100 while maximizing the volume of stored compressed air due to the curvature of the dome shaped roof 1306. In some embodiments, a further potential advantage of having the dome shaped roof 1306 is high pressure resistance compared to a flat roof due to the curved surface of the dome shaped roof 1306. In some embodiments, the underwater energy storage device 1350 further comprises an upper banister (not shown) located on top the dome shaped roof 1306. In some embodiments, a space defined by the upper banister above the dome roof 1306 is partitioned into a plurality of chambers to provide reinforcement to the at least one storage tank wall 103 and the dome shaped roof 1306 of the storage tank 100. In some embodiments, the space defined by the upper banister is filled with weights as is further described in Figure 17.

[0480] Referring now to Figure 13C, showing a schematic representation of an underwater energy storage device configured for operating on an unleveled ground by positioning the one or more air openings at an edge of the storage tank roof, according to some embodiments of the invention. Insome embodiments, an underwater energy storage device 1340 includes at least one of the one or more air openings 206 positioned on an edge of the storage tank roof 105. In some embodiments, the storage tank 100 is positioned on a ground 1304, for example the seabed 250. In some embodiments, the storage tank 100 is leveled. In some embodiments, the storage tank 100 undesirably moves and becomes unleveled. In some embodiments, the ground 1304 is unleveled and the storage tank 100 is unleveled. In some embodiments, a potential advantage of positioning the at least one of the one or more air openings 206 on an edge of the storage tank roof 105 is preventing air from being caged in a top corner in the storage tank 100 during and following air release, thereby allowing the proper flow of air from and to the storage tank 100.

[0481] In some embodiments, the storage tank 100 is unleveled. In some embodiments, water is accumulated in a lowest part inside storage tank 100 in an unleveled position. In some embodiments, at least one of the one or more water openings 204 is sealed for preventing passage of air and / or water. In some embodiments, a potential advantage of sealing at least one of the one or more water openings 204 when the storage tank 100 is unleveled is preventing loss of stored compressed air from the storage tank 100.

[0482] Referring now to Figure 13D, showing a schematic representation of an underwater energy storage device configured for operating on an unleveled ground, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 1360 is configured such that at least one of the one or more water openings 204 connected to one or more water pipes 1308. In some embodiments, preferably, the one or more water openings 204 which are positioned higher are connected to the one or more water pipes 1308. In some embodiments, the one or more water pipe 1308 is oriented downwards. A potential advantage of the one or more water pipes 1308 oriented downwards is increasing the maximal gas volume capacity of the storage tank 100.

[0483] Referring now to Figure 13E, showing a schematic representation of an underwater energy storage device configured for operating on an unleveled ground, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 1380 is configured such that each of the one or more water openings 204 connect to each of the one or more water pipes 1308. In some embodiments, the one or more water pipes 1308 connect to a downward facing main water pipe 1310. A potential advantage of the one or more water pipes 1308 which connect to a downward facing main water pipe 1310 is further increasing the maximal gas volume capacity of the storage tank 100.

[0484] In some embodiments, one or more planks protruding from the ground 1304 secure and prevent movement of the storage tank 100 on the ground 1304. In some embodiments, the one or more planks are positioned adjacent to the storage tank 100. Optionally, the one or more planks are positionedbelow the storage tank 100. In some embodiments, the one or more planks are made of materials for example metals such as stainless steel and / or concrete foundations.

[0485] Referring now to Figure 14A, showing a schematic representation of an underwater energy storage device having peripheral edges, according to some embodiments of the invention. In some embodiments, water currents encountering the exterior of the storage tank 100 may lead to a generation of turbulent flows. In some embodiments, turbulent flows meeting a sandy ground on the seabed 250 may cause downcutting or moving of sand from the seabed 250 to create pits in the underwater surface. In some embodiments, turbulent flows may remove sand from an area in the seabed 250 positioned under the storage tank 100 due to downcutting to form pits. In some embodiments, formation of pits under the storage tank 100 may cause an undesired shift in the orientation of the area in the seabed 250 positioned under the storage tank 100 making the storage tank 100 unleveled. In some embodiments, an underwater energy storage device 1400 is equipped with peripheral edges 1402 contacting the bottom part of the storage tank 100 or, alternatively, being an integral part of the bottom part of the storage tank 100. In some embodiments, equipping the underwater energy storage device 1400 with peripheral edges 1402 lowers a location of the center of mass of the underwater energy storage device 1400. In some embodiments, a potential advantage of an energy storage device 1400 with a lower center of mass is higher structural stability and reduced tilting risk. In some embodiments, the peripheral edges 1402 have a width from about 1 meter to about 10 meters, optionally from about 2 meters to about 6 meters, optionally from about 4 meters to about 8 meters. In some embodiments, the peripheral edges 1402 are made of a high strength material, for example concrete, steel or combination of concrete and steel. In some embodiments, potential advantages of peripheral edges 1402 contacting the bottom part of the storage tank 100 or, alternatively, being an integral part of the bottom part of the storage tank 100 are the following: a. preventing formation of pits under the storage tank 100 due to turbulent flows by being the surface in contact with the storage tank 100 on which the turbulent flows are generated such that downcutting is prevented.

[0486] b. stabilizing the storage tank 100 due to the peripheral edges 1402 contacting the whole periphery of the storage tank 100 and preventing movement of the storage tank 100.

[0487] Referring now to Figure 14B, showing a schematic representation of an underwater energy storage device having peripheral edges, according to some embodiments of the invention. In some embodiments, the peripheral edges 1402 comprises an inclined edge 1404. In some embodiments, the inclined edge 1404 is prevents or reduces the level of turbulence generated around the peripheral edges 1402 by streamlining the flow of water around the peripheral edges 1402 to maintain the flow of water to be orderly and parallel to the surface of the peripheral edges 1402, reducing the likelihood of flowseparation and the subsequent turbulent wake. In some embodiments, the inclination of the inclined edge 1404 comprises an angle from about 1 degree to about 89 degrees, optionally from about 15 degrees to about 60 degrees, optionally from about 30 degrees to about 50 degrees. In some embodiments, a potential advantage of preventing or reducing level of turbulence generated around the peripheral edges 1402 is preventing downcutting through the seabed 250 to form holes under the peripheral edges 1402.

[0488] Exemplary Anchoring means

[0489] The storage tank 100 typically holds air and as such needs to counterbalance the upward buoyancy force exerted by seawater. To that affect providing anchoring means is desired.

[0490] In some embodiments, the anchoring means is provided by configuring an underwater energy storage device to apply sufficient gravitational force by weight to counterbalance a buoyancy force exerted on the energy storage device. As used herein, the term “buoyancy force exerted on the underwater energy storage device” means buoyancy force exerted on the underwater energy storage device and on compressed air stored in the storage tank 100 in case there is any. In some embodiments, the gravitational forces are provided by the self-weight of the underwater energy storage device and / or the storage tank 100 and / or by distributing one or more weights on the storage tank 100 as shown for example in Figures 15, 16A, 16B, 16C, 17 and 18.

[0491] In some embodiments, the weight of the underwater energy storage device or the storage tank 100 required for anchoring the storage tank 100 to a surface (e.g., the seabed or a surface) is from about 5% to 30% more of the buoyancy force exerted by / on the storage tank 100, optionally from about 10% to 20%, optionally from about 15% to 25%.

[0492] In some embodiments, the weight of the storage tank 100 is from about 70 tons to about 20000 tons, optionally from about 500 tons to about 10000 tons, optionally from about 100 tons to about 15000 tons. In some embodiments, the weight of the storage tank 100 is greater than 20000 tons.

[0493] In some embodiments, the storage tank 100 has a balanced weight which is a balance between the gravitational and the buoyancy force exerted by / on the storage tank 100. In some embodiments, the storage tank 100 is fully submerged in water.

[0494] Exemplary anchoring by customized self-weight energy storage device

[0495] In some embodiments, buoyancy force exerted on the underwater energy storage device 200 is counterbalanced by gravitational forces provided either by the self- weight of the underwater energy storage device 200 as a whole or by the self-weight of the storage tank 100 for preventing floatation of the underwater energy storage device 200. In some embodiments, the underwater energy storagedevice 200 is customized for having a specific self-weight required for counterbalancing the buoyancy force exerted on the underwater energy storage device 200.

[0496] Exemplary anchoring by added weights

[0497] In some embodiments, one or more weights are distributed on top of and / or inside of the storage tank 100 for anchoring it.

[0498] Referring now to Figure 15, showing a schematic representation of an exemplary method of anchoring an underwater energy storage device by distributing weights on the storage tank, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 1500 (shown in a cross section view) is equipped with peripheral edges 1402 contacting the bottom part of the storage tank 100 or, alternatively, being an integral part of the bottom part of the storage tank 100. In some embodiments, one or more weights 1506 are distributed on the storage tank 100 acting to counterbalance pressure and anchor the device 1500. In some embodiments, the one or more weights 1506 are made of materials comprising for example stones, gravel, magnetite, metal and / or concrete.

[0499] In some embodiments, the one or more weights 1506 comprise precast elements. In some embodiments, optionally, the one or more weights 1506 comprising precast elements have a predetermined weight and / or shape, for example, quadrangular shaped precast elements. In some embodiments, potential advantages of precast elements having a predetermined weight and / or shape are the following:

[0500] a. Optimal occupancy of space;

[0501] b. Accurate control on the weight distribution in the underwater energy storage device 1500;

[0502] and

[0503] c. Easy removal of the precast elements.

[0504] In some embodiments, the one or more weights 1506 are distributed on the peripheral edges 1402 and on the storage tank roof 105, surrounding the air pipe 202. In some embodiments, a potential advantage of distributing the one or more weights 1506 on both the storage tank roof 105 and the peripheral edges 1402 is potentially preventing deterioration of the one or more weights 1506 by forming a hydrodynamic and low drag shape.

[0505] Referring now to Figure 16A showing a schematic representation of a method of anchoring an underwater energy storage device by distributing one or more weights on the tank floor, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 1600 (shown in a cross section view) positioned on a seabed 250 comprises the storage tank 100 and one or more water pipes 1602 for communicating the storage tank 100 with seawater outside the storage tank 100. In some embodiments, the one or more weights 1506 are distributed inside the storage tank100, on the floor 702, and are used for anchoring the storage tank 100. In some embodiments, the one or more weights 1506 are positioned in a manner that allows water flow to and from the storage tank 100 via the one or more water pipes 1602. In some embodiments, the storage tank 100 is further anchored by the peripheral edges 1402.

[0506] Referring now to Figure 16B showing a schematic representation of a method of anchoring an underwater energy storage device by distributing one or more weights on the storage tank floor, according to some embodiments of the invention. In some embodiments, the one or more weights 1506 comprise an individual weight element 1604 (shown in a cross section view) positioned on the storage tank floor 702 for anchoring the storage tank 100.

[0507] Referring now to Figure 16C showing a schematic representation of a top view of an individual weight element positioned on a floor of a tank, according to some embodiments of the invention. In some embodiments, the individual weight element 1604 is positioned on the storage tank floor 702. The individual weight element 1604 possess a geometry that allows water to access the one or more water pipes 1602.

[0508] Referring now to Figure 17 showing a schematic representation of a method for anchoring an underwater energy storage device by distributing weights on the storage tank, according to some embodiments of the invention. In some embodiments, an upper banister 1702 (shown in a cross section view) is mounted on the edges of the storage tank roof 105 and are configured for containing the one or more weights 1506 or fillers as will be described later. In some embodiments, the upper banister 1702 is made of for example concrete or a metal mesh. In some embodiments, a lower banister 1704 is positioned on the peripheral edges 1402 and are configured for containing more of the one or more weights 1506. In some embodiments, the lower banister 1704 is made of for example concrete or a metal mesh. In some embodiments, the one or more weights 1506 are optionally distributed further on the storage tank floor 702. In some embodiments, the one or more water pipes 1602 are positioned in an angle such that an opening 1706 is positioned above the lower banister 1704 and, in some embodiments, at least one water pipe from the one or more water pipes 1602 passes through a width of the lower banister 1704 such that an opening 1708 is positioned outside the lower banister 1704. In some embodiments, potential advantages of the one or more water pipes 1602 being positioned in an angle to be above the lower banister 1704 or in at least one water pipe from the one or more water pipes 1602 passing through the width of the lower banister 1704 is preventing interference to water flow due to the lower banister 1704 and / or the weights 1506.

[0509] In some embodiments, a space defined by the upper banister 1702 is partitioned into a plurality of chambers to provide reinforcement to the least one storage tank wall 103 and the storage tank roof 105. In some embodiments, weights and / or fillers are distributed in the plurality of chambers.Referring now to Figure 18 showing a schematic representation of a method of anchoring an underwater energy storage device by applying weights on the storage tank roof 105, according to some embodiments of the invention. In some embodiments, a weight 1802 (shown in a cross section view) is mounted on the storage tank roof 105, the weight 1802 having a shape suitable to be positioned firmly on the storage tank roof 105. In some embodiments, the weight 1802 is made of materials comprising for example concrete. In some embodiments, the one or more weights 1506 are further distributed on the weight 1802.

[0510] In some embodiments, optionally, the underwater energy storage device 1800 further comprises peripheral edges 1402 (not shown) contacting the bottom part of the storage tank 100 or, alternatively, being an integral part of the bottom part of the storage tank 100 for potentially preventing downcutting and potentially stabilizing the underwater energy storage device 100.

[0511] Exemplary anchors

[0512] In some embodiments, anchoring of an underwater energy storage device is provided by one or more anchors mechanically or physically connecting the device to the seabed 250.

[0513] Referring now to Figure 19 showing a schematic representation of a method of anchoring an underwater energy storage device via caisson anchors, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 1900 is anchored to the seabed 250 by one or more caisson anchors 1902 partially embedded in the seabed 250 and connecting the device 1900 to the seabed 250 by applying suction in contact points 1904 situated in the lower surface of the device 1900. In some embodiments, a potential advantage of caisson type anchors is potentially improving the mechanical strength of high localized strain areas and counterbalancing vertical pressures.

[0514] Referring now to Figure 20A showing a schematic representation of a method for anchoring an energy storage via one or more anchor points, according to some embodiments of the invention. In some embodiments, an underwater storage device is anchored to the seabed 250 by one or more anchor points 2004 partially protruding from the seabed 250 and connecting the underwater energy storage device 2000 to the seabed by cables 2002. In some embodiments, the cables 2002 connect the device 2000 to the seabed 250 by attaching one end of the cable 2002 to another anchor point 2002 positioned on a wall of the storage tank 100 and the other end of the cable 2002 to an anchor point 2004. In some embodiments, a potential advantage of anchor points 2004 is potentially counterbalancing horizontal loads due to water currents

[0515] Referring now to Figure 20B showing a schematic representation of a method of anchoring an underwater energy storage via anchor points, according to some embodiments of the invention. Insome embodiments, an underwater energy storage device 2050 comprises the storage tank 100 comprising one or more poles 2008 positioned vertically to the ground. In some embodiments, a potential advantage of poles 2008 comprised in the storage tank 100 is potentially reinforcing the storage tank 100. In some embodiments, the cables 2002 connect the device 2050 to the seabed 250 by attaching one end of the cable 2002 to an anchor point 2006 positioned on the upper part of the pole 2008 and the other end of the cable 2002 to the anchor point 2004 positioned on the seabed surface.

[0516] Referring now to Figure 21, showing a schematic representation of an underwater energy storage device including a combination of structural features for facilitating submerging and anchoring of the device, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 2100 includes the storage tank 100 comprising a storage tank floor 702 which holds one or more weights 1506. In some embodiments, an upper banister 1702 is located on the storage tank roof 105 configured for containing the one or more weights 1506. In some embodiments, the storage tank 100 is equipped with a structure comprising the peripheral edges 1402 contacting the bottom part of the storage tank 100. In some embodiments, a lower banister 1704 is located on the peripheral edges 1402 for containing the one or more weights 1506. In some embodiments, the device 2100 is anchored to the seabed 250 by caisson anchors 1902 and by anchor points 2004 connectable by the cables 2002.

[0517] In some embodiments, optionally, a space defined by the upper banister 1702 is partitioned into a plurality of chambers to provide reinforcement to the at least one storage tank wall 103 and the storage tank roof 105. In some embodiments, weights and / or fillers are distributed in the plurality of chambers.

[0518] Exemplary bases for mounting an underwater energy storage device

[0519] In some embodiments, the underwater energy storage device 200 is mounted on a base for elevating and / or leveling the storage tank 100. In some embodiments, the weight of the underwater energy storage device 200, either the self-weight of the underwater energy storage device alone and / or with added weights is sufficient for preventing lateral and / or horizontal movement of the underwater energy storage device 200. In some embodiments, one or more connectors connect the underwater energy storage device 200 to a base. In some embodiments, one or more stoppers are installed on the base configured for preventing lateral movement of the underwater energy storage device 200.

[0520] In some embodiments, the self-weight of the underwater energy storage device 200 required for counterbalancing a buoyancy force and prevent floatation of the underwater energy storage device 200 includes the weight of a base the underwater energy storage device is mounted on. Alternatively,the self-weight of the underwater energy storage device required for counterbalancing the buoyancy force does not include the weight of a base the underwater energy storage device is mounted on.

[0521] Referring now to Figure 22, showing a schematic representation of an exemplary base comprising poles and a plurality of beams for mounting an underwater energy storage device, according to some embodiments of the invention. In some embodiments, a base 2200 is used for mounting and elevating the underwater energy storage device 200 (not shown in figure). In some embodiments, the base 2200 includes vertically standing poles 604 for elevating the underwater energy storage device 200. In some embodiments, the base 2200 further comprises a plurality of beams 2202 to be used as a surface for the energy storage device 200. In some embodiments, the plurality of beams 2202 are arranged horizontally. In some embodiments, the beams are intertwined and / or the beams are parallel.

[0522] In some embodiments, optionally, the base 2200 comprises a solid surface for mounting and elevating the energy storage device 200.

[0523] Referring now to Figure 23, showing a schematic representation of an underwater energy storage device positioned on a base with peripheral edges, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 1000 is mounted on a base 2302 configured for elevating and potentially leveling the underwater energy storage device 1000. In some embodiments, the base 2302 comprises peripheral edges 1402 contacting the bottom part of the base 2302 or, alternatively, being an integral part of the bottom part of the base 2302 for potentially preventing downcutting and potentially stabilizing the underwater energy storage device 100.

[0524] Referring now to Figure 24A showing a schematic representation of an underwater energy storage device positioned on a base, according to some embodiments of the invention. In some embodiments, water currents encountering the exterior of the storage tank 100 may lead to a generation of turbulent flows. In some embodiments, an underwater energy storage device 200 is mounted on a base 2302 being a horizontal platform having an edge 2402. In some embodiments, the edge 2402 has an inclination configured for preventing the generation of turbulence flows or reducing the level of turbulence generated around the base 2302 by streamlining the flow of water around the base 2302 to maintain the flow of water to be orderly and parallel to the surface of the base 2302, reducing the likelihood of flow separation and the subsequent turbulent wake. In some embodiments, the inclination comprises an angle from about 1 degree to about 89 degrees; optionally from about 15 degrees to about 60 degrees, optionally from about 30 degrees to about 50 degrees. In some embodiments, a potential advantages of having the base 2302 being a horizontal platform having the edge 2402 is potentially preventing formation of pits under the storage tank 100 due to prevention of the generation of turbulence flows or reduction of the level of turbulence generated around the storagetank 100. In some embodiments, the base 2302 is made of high strength materials, for example, metal, concrete and / or polymer. In some embodiments, the base 2302 is equipped with foundations (not shown) configured for anchoring the base 2302 to the seabed 250.

[0525] Referring now to Figure 24B showing a schematic representation of a modular base comprising one or more discrete units for mounting an energy storage device, according to some embodiments of the invention. In some embodiments, the base 2302 for mounting an underwater energy storage device (not shown) is configured for being modular. In some embodiments, the base 2302 comprises one or more discrete units 2404 which when positioned in proximity to one another form the base 2302 which may be used for mounting of an underwater energy storage device (not shown) on the base 2302.

[0526] Referring now to Figure 25 showing a schematic representation of a side view of a base positioned on a slope of the seabed, according to some embodiments of the invention. In some embodiments, the base 2302 is configured to fit a slope of the seabed 250. In some embodiments, the base 2302 comprises a lower surface 2504 having inclinations which correspond to the slope of the seabed 250. In some embodiments, the base 2302 further comprises an upper surface 2502 for mounting an underwater energy storage device (not shown in figure). In some embodiments, the upper surface 2502 is leveled. In some embodiments, one or more planks 2506 protruding from the seabed 250 secure and prevent movement of the base 2302. In some embodiments, the one or more planks 2506 are positioned adjacent to the base 2302. Optionally, the one or more planks 2506 are positioned below the base 2302. In some embodiments, the one or more planks 2506 are made of materials for example metals such as stainless steel and / or concrete foundations. In some embodiments, the one or more planks 2506 are positioned in the seabed 250 prior to positioning the base 2302 on the seabed 250. Optionally, the one or more planks 2506 are positioned in the seabed 250 following positioning of the base 2302 on the seabed 250.

[0527] Referring now to Figure 26, showing a schematic representation of a side view of an underwater energy storage device positioned on a base comprising holes, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 200 is mounted on a base 2302 comprising one or more holes 2602. In some embodiments, at least one of the one or more holes 2602 transverse from one side of the base 2302 to another side of the base 2302 for allowing flow of water. In some embodiments, a potential advantage of allowing water flow via the base 2302 is potentially preventing the storage tank 100 from being buried in sand due to the water flows potentially carrying sand away from the base 2302.Exemplary fillers

[0528] Referring now to Figure 27 showing a schematic representation of a top view of a frame enclosing fillers, according to some embodiments of the invention. In some embodiments, a plurality of fillers 2702 occupy a vacant space defined by a frame 2704, the plurality of fillers 2702 being able to assume a form of the space they are confined within. In some embodiments, potential advantages of filling a space with a plurality of fillers 2702 is easiness of assembly and applying weight. In some embodiments, the plurality of fillers 2702 confined within a space are used as a base for mounting the storage tank 100 as shown in Figures 28A and 32 and in some embodiments, the fillers 2702 are used to occupy space in the upper banister 1702 as shown in Figure 31.

[0529] In some embodiments, device 2700 comprises a plurality of fillers 2702 which serve to occupy space in a void defined by frame 2704 and optionally to anchor device 2700. In some embodiments, the plurality of fillers 2702 comprise concrete sacks. Optionally the concrete sacks are positioned in the space defined by frame 2704 in a “fresh” state, prior to hardening of the concrete due to a hydration process in which the concrete reacts with water to form a hard solid, such that the concrete sacks are flexible at the time of positioning. In some embodiments, a potential advantage of fillers comprising flexible concrete sacks is high occupancy of free space due to the flexibility of the concrete sacks. In some embodiments, optionally, the concrete sacks comprise an additive which delays hardening of a liquid concrete slurry contained in the concrete sacks, allowing the concrete sacks to flex and optimally fit the free space before they harden and solidify. In some embodiments, the plurality of fillers 2702 comprises for example metal beams, stones, gravel, sand, or combination of one or more types of fillers.

[0530] Referring now to Figure 28A, showing a schematic representation of a side view of a base comprising a plurality of concrete sacks fillers positioned on the seabed and secured by planks, according to some embodiments of the invention. In some embodiments, the underwater energy storage device 200 is mounted on the base 2302, the base 2302 comprising a frame 2704, which encloses a plurality of concrete sacks 2802. In some embodiments, the plurality of concrete sacks 2802 are positioned in the space defined by frame 2704 in a “fresh” state, prior to hardening of the concrete due to hydration, such that the concrete sacks are flexible at the time of positioning and configured for assuming a shape of a space the plurality of concrete sacks 2802 are confined in. In some embodiments, the planks 2506 protruding from seabed 250, penetrate the base 2302. In some embodiments, the plurality of concrete sacks 2802 are arranged to occupy the free space in the base 2302 and surround the planks 2506.

[0531] Referring now to Figure 28B, showing a schematic representation of a connecting element for connecting two or more concrete sacks, according to some embodiments of the invention. In someembodiments, two or more cement sacks from the plurality of concrete sacks 2802 (not shown in figure) are connected to one another by a connecting element 2850 comprising a plurality of radially protruding branches 2806 configured for penetrating the plurality of concrete sacks 2802 (not shown). In some embodiments, the plurality of radially protruding branches 2806 comprise a sharp edge 2804 for enhancing the penetrating ability of the plurality of radially protruding branches 2806 in the plurality of concrete sacks 2802 (not shown). In some embodiments, at least two of the plurality of radially protruding branches 2806 penetrate at least two of the plurality of concrete sacks 2802 to form an accumulation of concrete sacks connected to one another.

[0532] In some embodiments, a plurality of ribbed rebars connects the at least two of the plurality of concrete sacks 2802. In some embodiments, a potential advantage of connecting the least two of the plurality of concrete sacks 2802 with the plurality of ribbed rebars is high durability of the concreterebar connection due to the high friction of the surface deformations of the rebar.

[0533] Referring now to Figure 29, showing a schematic representation of a method of fixating a base comprising a concrete sack to the seabed by piercing the concrete sack with a piercing stick, according to some embodiments of the invention. In some embodiments, a piercing stick 2904 protruding from the seabed 250 is entrapped in a concrete sack 2802. In some embodiments, the piercing stick 2904 comprises a sharp edge 2908 for piercing the concrete sack 2802. In some embodiments, and a plurality of anchoring extensions 2906 configured to hold the piercing stick 2904 in the concrete sack 2802 and fixate the frame 2704 and the concrete sack 2802 to the seabed 250. In some embodiments, the piercing stick 2904 is a ribbed rebar.

[0534] In some embodiments, optionally, the base 2302 is mounted on a horizontal platform (not shown) made of high strength material for example, concrete or steel or combination of concrete and steel. In some embodiments, the horizontal platform facilitates making adjustment to a height or angle in which the storage tank 100 is positioned in. In some embodiments, a potential advantage of the horizontal platform facilitating making adjustment to a height or angle in which the storage tank 100 is positioned in is preventing a costly manufacturing of a new base. In some embodiments, the horizontal platform is equipped with concrete foundations (not shown) configured for anchoring the horizontal platform to the seabed 250. In some embodiments, the horizontal platform is further equipped with piercing sticks (not shown) for piercing the frame 2704 and the concrete sacks 2802 and securing the base 2302 to the horizontal platform. In some embodiments, the horizontal platform is configured for being modular. In some embodiments, the horizontal platform comprises one or more discrete units which when positioned in proximity to one another form the horizontal platform.Referring now to Figure 30, showing a schematic representation of a concrete sack comprising a bag containing handles, according to some embodiments of the invention. In some embodiments, the concrete sack 3000 comprises an inner concrete sack 3002 comprising concrete or cement in a “fresh” state i.e. prior to hardening of the concrete due to hydration. In some embodiments, the inner concrete sack 3002 is placed in a bag 3004, optionally comprising handles 3006 for enabling lifting of the concrete sack 3002. In some embodiments, the bag 3004 is made of a flexible material for example a polymer. In some embodiments, the bag 3004 is made of a high strength fabric, being able to carry the weight of the inner concrete sack 3002 without tearing, for example ballistic nylon, ripstop nylon and high-denier polyester. In some embodiments, a potential advantage of concrete sack placed in a bag 3004 with handles 3006 is facilitating transferring the concrete sack 3000 by a floating crane and / or winch (not shown in the figure).

[0535] Referring now to Figure 31, showing a schematic representation of concrete sacks occupying space on the storage tank roof, according to some embodiments of the invention. In some embodiments, the plurality of concrete sacks 2802 occupy space located on the storage tank roof 105 and defined by the upper banister 1702. In some embodiments, the concrete confined in the plurality of concrete sacks 2802 is in a “fresh” state i.e., prior to hardening of the concrete due to hydration, such that the plurality of concrete sacks 2802 are flexible and configured for assuming a shape of a space the plurality of concrete sacks 2802 are confined in.

[0536] In some embodiments, precast elements (not shown) having a predetermined weight and / or shape occupy the space located on the storage tank roof 105 and defined by the upper banister 1702.

[0537] Referring now to Figure 32, showing a schematic representation of a base comprising combination of fillers, according to some embodiments of the invention. In some embodiments, the base 3200 is positioned on seabed 250 and comprises a frame 2704, which defines a space in which a plurality of the fillers 2702 are positioned. In some embodiments, the fillers 2702 comprise stones 3202 and / or sand 3204. In some embodiments, one or more ribs 3206 are positioned in the base 3200 and contacting the frame 2704 for avoiding deformation of the frame 2704 and maintaining a geometry of the frame 2704.

[0538] Exemplary method of fabricating a base

[0539] In some embodiments, fabrication of a base initiates with scouring an existing underwater map for an appropriate location and selecting appropriate optional locations according to relevant parameters, for example the angle of the slope in the seabed, the type of ground (i.e., whether it comprises rocks or sand).

[0540] In some embodiments, one or more vetting surveys are performed in the potential locations, for example geographic, geological, geophysical and geotechnical surveys. In some embodiments, ageneral area in the seabed 250 on which the base 2302 is to be positioned is defined according to an input provided by the one or more surveys.

[0541] Referring now to Figure 33A, showing a schematic representation of mapping inclinations in the seabed on which a base is to be positioned, according to some embodiments of the invention. In some embodiments, markers 3302 are positioned on the seabed 250 for indicating a general location for positioning the base 2302. In some embodiments, a sonar 3306 is used in the water 3304 to scan the seabed 250 location defined by markers 3302 and provides an updated input data regarding the surface of the seabed. In some embodiments, additionally, one or more comprehensive surveys are performed in the general location, for example, geological and geotechnical.

[0542] Referring now to Figure 33B, showing a schematic representation of a topographic map of the seabed, defining a general area on which a base is to be positioned, according to some embodiments of the invention. In some embodiments, the updated input data received from the sonar 3306 is used to generate a topographic map 3310. In some embodiments, a specific location for positioning the base 2302 is defined according to the topographic map 3310. In some embodiments, a specific location for positioning the base 2302 is defined according to information received from the comprehensive surveys, for example, geological and geotechnical. In some embodiments, a specific location for positioning the base 2302 is defined according to one or more requirements for the base 2302 determined by the underwater energy storage device 200 attributes. In some embodiments, a graphic representation of the base shape 3308 is calculated according to inclinations data obtained from the topographic map 3310 and one or more requirements for the base 2302.

[0543] In some embodiments, further comprehensive geotechnical survey is performed in the specific location for gathering data on the seabed 250 and generate an appropriate plan for securing the base 2302 (e.g., drilling for inserting concrete foundations).

[0544] In some embodiments, optionally, leveling of the seabed 250 in the specific location is done. Referring now to Figure 33C, showing a schematic representation of a base fabricated according to updated input data, according to some embodiments of the invention. In some embodiments, utilizing the graphic representation of the base shape 3308, the base 2302 is fabricated. In some embodiments, the base 2302 is fabricated by milling a bulk piece of material, for example metal. In some embodiments, the base 2302 is fabricated by casting to a customized mold. In some embodiments, the base is fabricated by 3D printing. In some embodiments, the base 2302 is fabricated by cutting a lower part of a hollow tube and removing parts of the tube to match the seabed surface. Alternatively, a flexible sheet is cut, bent and has its edges brought together and joined to form a ring shape, the ring having a bottom part which fits the seabed surface. In some embodiments, the cut tubeor sheet is placed on the seabed and is filled with fillers, for example concrete sacks. In some embodiments, the base 2302 is made of waterproof material, for example metal, concrete or polymer.

[0545] Referring now to Figure 33D, showing a schematic representation of a top view of a base positioned on the seabed and in between planks, according to some embodiments of the invention. In some embodiments, the base 2302 is positioned above and adjacent to the planks 2506 protruding from seabed 250, thereby securing the base 2302 in place.

[0546] In some embodiments, one or more ribs 3204 are positioned in the base 3200 and contacting the frame 2704 for avoiding deformation of the frame 2704 and maintaining a geometry of the frame 2704. In some embodiments, the one or more ribs 3204 are positioned in the base 2302 prior to positioning the base 2302 on the seabed 250.

[0547] Referring now to Figure 34A-B, showing a flow chart of an exemplary method of fabricating a slope-fitted base to be positioned on seabed at an underwater location, according to some embodiments of the invention.

[0548] In some embodiments, an exemplary method of fabricating a slope-fitted base comprises: 1. Scouring an existing underwater map for an appropriate location according to relevant parameters, for example an angle of a slope in the seabed 250 or the type of ground (3402);

[0549] 2. Selecting a plurality of optional locations according to the relevant parameters (3404); 3. Performing one or more surveys for vetting the optional locations, for example geographic, geologic, geophysical, geotechnical and topographical surveys (3406);

[0550] 4. Defining a general area in the seabed 250 on which the base 2302 is to be positioned (3408);

[0551] 5. Allocating markers 3302 surrounding the general area in the seabed 250 on which the base 2302 is to be positioned (3410);

[0552] 6. Scanning the surface, for example using a sonar, in the area in the seabed 250 in which the base 2302 is to be positioned to receive updated inclinations input data (3412);

[0553] 7. Calculating inclinations based on the updated inclination input data (3414);

[0554] 8. Generating a topographic map 3310 of the general area in the seabed 250 on which the base 2302 is to be positioned (3416);

[0555] 9. Optionally, performing one or more comprehensive surveys, for example, geotechnical, geophysical, topographical and geographical surveys to receive survey information (3418);

[0556] 10. Determining a specific location of the base 2302 according to one or more of the following: the topographic map 3310, survey information and one or more requirements for the base 2302 (3420);

[0557] 11. Calculating a graphic representation of the base shape 3308 according to the topographic map 3310 (3422);12. Fabricating the base 2302 for example by milling, casting or 3D printing (3424).

[0558] 13. Optionally, positioning one or more rods 3204 inside the base 2302 (3426);

[0559] 14. Optionally, positioning one or more fillers 2702 inside the base 2302 (3428).

[0560] Exemplary methods for submerging an energy storage device

[0561] In some embodiments, the underwater energy storage device 200 is fabricated on land and then is submerged in the sea.

[0562] Referring now to Figure 35, showing a schematic representation of a method for submerging an underwater energy storage device in the sea in a controlled manner, according to some embodiments of the invention. In some embodiments, submerging the underwater energy storage device 200 in water 3304 in a controlled manner is performed by a floating crane 3510 and / or winch (not shown). In some embodiments, the floating crane 3510 and / or winch lowers the underwater energy storage device 200 for submerging in a controlled manner. In some embodiments, a downward gravitational force exerted by the energy storage device 200 causes the underwater energy storage device 200 to submerge. In some embodiments, it is desirable to counterbalance some of the downward gravitational force so that the controlled submerging of the underwater energy storage device 200 can be facilitated with the floating crane 3510 and / or winch configured for lifting lighter loads. In some embodiments, the floating crane 3510 and / or winch configured for lifting lighter loads is characterized by being smaller in size. In some embodiments, a potential advantage of using a smaller floating crane 3510 and / or winch is reducing the costs associated with the submerging of the energy storage device 200. In some embodiments, the underwater energy storage device 200 is being submerged in water 3304 by the floating crane 3510 and / or winch (not shown) configured for lowering a main cable 3504 connected to a plurality of cables 3502 which are attached to the underwater energy storage device 200 in a plurality of lifting points 3514. In some embodiments, a spreader beam (not shown) configured for distributing the weight of the underwater energy storage device 200 facilitates in lifting the underwater energy storage device 200 by the floating crane 3510. In some embodiments, the floating crane 3510 and / or winch (not shown) has installed a lifting weight gauge (not shown) for measuring a balanced weight of the underwater energy storage device 200 according to a balance of the downward gravitational forces exerted by the underwater energy storage device 200 and the buoyancy force exerted on the underwater energy storage device 200. In some embodiments, a compressor 3512 is positioned on the floating crane 3510 and / or winch (not shown) for supplying air. In some embodiments, one or more air valves (not shown) controls air flow to and from the storage tank 100 via the one or more air openings 206. In some embodiments, the one or more air pipes 202 are connected to the compressor 3512 via a T connection (not shown) configured for either navigate compressed air from the compressor 3512 to the storage tank 100 or for navigating compressed airfrom the storage tank 100 to an outside receiver (not shown). In some embodiments, the compressor 3512 has an operating pressure, for example, from about 5 bars to about 500 bars, optionally from about 50 bars to about 200 bars, optionally from about 20 bars to about 100 bars. In some embodiments, the compressor 3512 has an air flow rate, for example, from about 100 L / sec to about 15000 L / sec, optionally from about 500 L / sec to about 10000 L / sec, optionally from about 300 L / sec to about 12000 L / sec. In some embodiments, compressed air 3506 stored in the storage tank 100 increases an upward buoyancy force exerted on the underwater energy storage device 200 which partially counterbalances the downward gravitational force exerted by the energy storage device 200 and allows the use of the floating crane 3510 and / or winch configured for lifting lighter weights. In some embodiments, the underwater energy storage device 200 is lowered by the floating crane 3510 and / or winch (not shown) at a lowering speed. In some embodiments, the lowering speed of the underwater energy storage device 200 by the floating crane 3510 and / or winch is determined according to the compressor 3512 air flow rate. In some embodiments, as the underwater energy storage device 200 is lowered in water 3304, a volume of the compressed air 3506 decreases. It is known that the upward buoyancy force depends on a volume of the compressed air 3506 such that as the volume of the compressed air 3506 reduces, the upward buoyancy force reduces accordingly. In some embodiments, air is supplied to the storage tank 100 via the one or more air pipes 202 to increase the volume of the compressed air stored in the storage tank 100 and maintain an exertion of the upward buoyancy force that partially counterbalances the downward gravitational force and allows the use of the floating crane 3510 configured for lifting lighter weights. In some embodiments, the one or more water openings 204 allow water flow during the submerging of the energy storage device 200. In some embodiments, the one or more water openings 204 are sealed during the submerging of the energy storage device 200. In some embodiments, a potential advantage of sealed one or more water openings 204 during the submerging of the energy storage device 200 is increasing an air volume which increases an upward buoyancy force. In some embodiments, during the submerging of the energy storage device 200, the one or more water openings 204 are sealed and an opening located in a central part of the storage tank floor 702 allows water flow during the submerging of the energy storage device 200. In some embodiments, a potential advantage of an opening located in a central part of the storage tank floor 702 during the submerging of the energy storage device 200 is preventing compressed air loss in an event of titling of the energy storage device 200 during submerging. In some embodiments, during the submerging of the underwater energy storage device 200, the one or more air pipes 202 are inserted to the storage tank 100 via the one or more water openings 204 for supplying air to the storage tank 100. In some embodiments, a potential advantage of connecting the one or more air pipes 202 to the storage tank 100 via the one or more water openings 204 is potentially allowingsimple and robust connections between the storage tank 100 and the one or more air pipes 202, potentially persisting during the displacement of the underwater energy storage device 200 while being submerged.

[0563] In some embodiments, floats are attached to the energy storage device 200 for increasing buoyancy, as shown for example in Figures 36-37.

[0564] Referring now to Figure 36, showing a schematic representation of a method for submerging an underwater energy storage device in the sea in a controlled manner, according to some embodiments of the invention. It is known that a pressure gradient in shallow depths is significantly higher compared to a pressure gradient in deeper depths. For example, a pressure difference between 0 meters and -10 meters is 50% while a pressure difference between -100 meters and -110 meters is 10%. In some embodiments, an increase in a pressure exerted by the water 3508 surrounding the underwater energy storage device 200 caused a decrease in a volume of the compressed air 3506 in the storage tank 100. In some embodiments, a decrease in a volume of the compressed air 3506 causes a decrease in the buoyancy force exerted on the underwater energy storage device 200. In some embodiments, in order to maintain a controlled submerging of the underwater energy storage device 200 by the floating crane 3510 and / or winch, particularly in the shallow depths in which the pressure gradient is high, one or more adjustable floats 3602 configured for containing air and releasing the air are connected to the underwater energy storage device 200. In some embodiments, the one or more adjustable floats 3602 are connected to the underwater energy storage device 200 by one or more ropes 3604. In some embodiments, the one or more adjustable floats 3602 are connected to the compressor 3512 (not shown) positioned on the floating crane 3510 and / or winch, via one or more air pipes 3606 configured for supplying air to the one or more adjustable floats 3602. In some embodiments, the one or more adjustable floats 3602 comprises a valve (not shown) configured for releasing air from the one or more adjustable floats 3602. In some embodiments, air is supplied to the storage tank 100 from the compressor 3512 via the one or more air pipes 202 to increase the volume of the compressed air stored in the storage tank 100 during the submerging of the underwater energy storage device 200. In some embodiments, during the submerging of the underwater energy storage device 200 in the shallow depths, the one or more adjustable floats 3602 are inflated with air. In some embodiments, during the lowering of the underwater energy storage device 200 in the high pressure gradient shallow water, the one or more adjustable floats 3602 inflated with air lead to exertion of an upward buoyancy force that compensate for the reduction of the buoyancy force due to the abrupt volume decrease of the compressed air 3506 stored in the storage tank 100. In some embodiments, optionally, the air contained in the one or more adjustable floats 3602 is released during the lowering of the underwater energy storage device 200.Referring now to Figure 37, showing a schematic representation of a method for submerging an underwater energy storage device in the sea in a controlled manner, according to some embodiments of the invention. In some embodiments, one or more floats strings 3702 comprising a plurality of floats 3704 connected by one or more wires 3706 are connected to the underwater energy storage device 200 for exerting an upward buoyancy force that partially counterbalances a downward gravitational force exerted by the underwater energy storage device 200. In some embodiments, during the submerging of the underwater energy storage device 200, the one or more floats strings 3702 connected to the underwater energy storage device 200 are gradually inserted to the water 3304. In some embodiments, by continuously lowering the underwater energy storage device 200, additional floats from the plurality of floats 3704 become submerged in water 3304, incrementally increasing the upward buoyancy force that partially counterbalances the downward gravitational force. In some embodiments, at least one of the plurality of floats 3704 is adjustable and configured to change volume in response to an exerted pressure by water 3304. In some embodiments, at least one of the plurality of floats 3704 has a fixed volume which is not dependent on a pressure exerted pressure by water 3304. In some embodiments, potential advantages of submerging an energy storage device equipped with one or more floats strings 3702 is the following:

[0565] a. Maintaining a sufficient buoyancy force at various depths for using a floating crane and / or winch configured for lifting lighter weights.

[0566] b. Preventing rapid submerging of the energy storage device 200 in an unfavorable event of floating crane / winch loss of control.

[0567] Exemplary method for adding weights and / or fillers during submerging of an underwater energy storage device

[0568] In some embodiments, the energy storage device 200 is fabricated on land and is then moved to a submerging site from which it can be submerged to the seabed 250. In some embodiments, addition of the weights 1506 to the energy storage device 200 is done prior to the insertion of the energy storage device 200 to the water. In some embodiments, alternatively or additionally, addition of the weights 1506 to the energy storage device 200 is done during the submerging of the energy storage device 200 when the energy storage device 200 is fully immersed in water. In some embodiments, alternatively or additionally, addition of the weights 1506 to the energy storage device 200 is done when the energy storage device 200 is positioned on the seabed 250. In some embodiments, alternatively or additionally, addition of the weights 1506 to the energy storage device 200 is done following the insertion of the energy storage device 200 to the water, when the energy storage device 200 is only partly immersed. In some embodiments, potential advantages of adding theweights 1506 to the energy storage device 200 when the energy storage device 200 is partly immersed are the following:

[0569] a. Avoid a complex procedure of mobilizing the energy storage device 200 with weights 1506 having an uneven distribution of weight which requires complex and expensive equipment. b. Avoid a complex procedure of mobilizing the weights 1506 separately from the energy storage device 200 and positioning the weights 1506 in the energy storage device 200 which requires special equipment for operating in the underwater environment.

[0570] Referring now to Figure 38 A, showing a schematic representation of a method for adding weight and / or fillers during submerging of an energy storage device, according to some embodiments of the invention. In some embodiments, an underwater energy storage device 3800 and the weights 1506 (not shown) and / or the plurality of fillers 2702 (not shown) are transported to the submerging site separately. In some embodiments, positioning of the weights 1506 and / or the plurality of fillers 2702 in an energy storage device 3800 is done during a controlled submerging of the underwater energy storage device 3800 by the floating crane 3510 (not shown) and / or winch (not shown). In some embodiments, a potential advantage of transporting the underwater energy storage device 3800 and the weights 1506 and / or the plurality of fillers 2702 separately to the submerging site is potentially using less expensive equipment for transportation to the submerging site. In some embodiments, the underwater energy storage device 3800 comprising an upper banister 1702 for containing the weights 1506 and / or the plurality of fillers 2702 is being submerged in water 3304. In some embodiments, optionally, the underwater energy storage device 3800 further comprises a plurality of tank piercing sticks 3802 protruding from the storage tank roof 105 for piercing concrete sacks (not shown in figure) and securing the concrete sacks to the storage tank 100.

[0571] Referring now to Figure 38B, showing a schematic representation of a method for adding weight and / or fillers during submerging of an energy storage device, according to some embodiments of the invention. In some embodiments, the weights 1506 and / or the plurality of fillers 2802 are positioned in the underwater energy storage device 3800 during the submerging of the underwater energy storage device 3800. In some embodiments, compressed air (not shown) is stored in the storage tank 100 for increasing the buoyancy force exerted by the underwater energy storage device 3800 and counterbalance the gravitational force exerted by the underwater energy storage device 3800 and the weights 1506 and / or the plurality of fillers 2702 and allow the use of the floating crane 3510 (not shown) and / or winch (not shown) configured for lifting lighter loads. In some embodiments, a number and type of the weights 1506 and / or the plurality of fillers 2702 to be positioned on the underwater energy storage device 3800 is decided according to a calculation of a maximal buoyancy force exerted on the underwater energy storage device 3800 (i.e., when a maximal volume of air is stored in thestorage tank 100) which counterbalances the gravitational force exerted by the underwater energy storage device 3800 and the added weights 1506 and / or plurality of fillers 2702. In some embodiments, the number and type of the weights 1506 and / or the plurality of fillers 2702 to be positioned on the underwater energy storage device 3800 is determined according to the maximal lifted weight capacity of the floating crane 3510 and / or winch (not shown). In some embodiments, during the submerging of underwater energy storage device 3800, a plurality of concrete sacks 3804 are distributed in the space defined by the upper banister 1702 and are secured to the storage tank 100 by the plurality of tank piercing sticks 3802. In some embodiments, optionally, liquid concrete i.e., in a “fresh” state is cast onto the space defined by the upper banister 1702. In some embodiments, weights 1506 are distributed in the space defined by the upper banister 1702. In some embodiments, weights 1506 are distributed on the peripheral edges 1402 in the space defined by the lower banister 1704. In some embodiments, a center of mass of the energy storage device 3800 is located in a lower part of the energy storage device 3800. In some embodiments, a potential advantage of the energy storage device 3800 having a center of mass located in a lower part is enhanced stability i.e., reduced risk of tipping over during lowering and submerging of the energy storage device 3800. In some embodiments, the center of mass of the energy storage device 3800 is not located in a lower part. In some embodiments, the weights 1506 and / or fillers 2702 positioned in a lower part of the energy storage device 3800 (e.g., on the peripheral edges 1402) causes the center of mass to shift to a lower part of the energy storage device 3800.

[0572] Exemplary method of a submerging of an energy storage device and adding weights in a controlled manner

[0573] In some embodiments, during the submerging of the underwater energy storage device 200 the gravitational force exerted by the underwater energy storage device 200 during the submerging of the underwater energy storage device 200 is counterbalanced by the buoyancy force exerted by the compressed air stored in the storage tank 100 for allowing the use of the floating crane 3510 configured for applying medium lifting force.

[0574] It is known that buoyancy force exerted on an object being submerged increases with increase of a submerged volume of the object being submerged. In some embodiments, during the submerging of the underwater energy storage device 200, in an initial stage, the underwater energy storage device 200 is partly submerged. In some embodiments, lowering the underwater energy storage device 200 being partly submerged increases the buoyancy force exerted on the underwater energy storage device 200 due to an increase of a submerged volume of the underwater energy storage device 200. In some embodiments, following the initial stage, the underwater energy storage device 200 is fully submerged. In some embodiments, lowering the underwater energy storage device 200 being fullysubmerged reduces the buoyancy force exerted on the underwater energy storage device 200 due to a decrease of a volume of the compressed air stored in the storage tank 100. In some embodiments, air is supplied to the storage tank 100 during the submerging of the underwater energy storage device 200 for increasing the volume of the compressed air stored in the storage tank 100 and increasing the buoyancy force.

[0575] In some embodiments, the supplying the storage tank 100 with compressed air while lowering and submerging the underwater energy storage device 200 is controlled and monitored. In some embodiments, uncontrolled and / or unmonitored lowering and submerging of the energy storage device 200 may lead to loss of compressed air. In some embodiments, a potential advantage of controlling and monitoring the supplying the storage tank 100 with air is preventing the underwater energy storage device 200 from exerting a downward force that may be not compatible with the lifting capabilities of the floating crane 3510 and / or winch.

[0576] In some embodiments, the adding the weights 1506 and / or the plurality of fillers 2702 to the underwater energy storage device 200 while lowering and submerging is monitored. In some embodiments, a potential advantage of monitoring the adding the weights 1506 and / or the plurality of fillers 2702 to the underwater energy storage device 200 is preventing the underwater energy storage device 200 from exerting a downward force that may be not compatible with the lifting capabilities of the floating crane 3510 and / or winch.

[0577] In some embodiments, the lowering the underwater energy storage device 200 by the floating crane 3510 and / or winch is controlled and monitored. In some embodiments, a potential advantage of controlling and monitoring the lowering of the underwater energy storage device 200 by the floating crane 3510 and / or winch is preventing loss of compressed air from the storage tank 100 that may result with an increase of the downward force exerted by the underwater energy storage device 200 which may be not compatible with the capabilities of the floating crane 3510 and / or winch.

[0578] Referring now to Figures 39A-B, showing a flow chart of an exemplary method of submerging an energy storage device and adding weights in a controlled manner, according to some embodiments of the invention.

[0579] In some embodiments, an exemplary method of submerging an energy storage device in a controlled manner comprises:

[0580] a. Optionally, connecting the underwater energy storage device 200 to floats for stabilizing the underwater energy storage device 200 in the water (3902);

[0581] b. Positioning the underwater energy storage device 200 in the water at the submerging site (3904);c. Supplying the storage tank 100 with air for storing an air volume at partial capacity of the storage tank 100 (3906);

[0582] d. Connecting the underwater energy storage device 200 to the floating crane 3510 and / or winch (3908);

[0583] e. Lifting the underwater energy storage device 200 by the floating crane 3510 and / or winch (3910);

[0584] f. Optionally, releasing the floats (3912);

[0585] g. Supplying the storage tank 100 with air for storing an air volume at full capacity of the storage tank 100 for maximizing the buoyancy force exerted on the underwater energy storage device 200 (3914);

[0586] Flowchart continues following the letter A to Figure 39B.

[0587] h. Adding the weights 1506 and / or the plurality of fillers 2702 to the underwater energy storage device 200 (3916);

[0588] i. Lowering the underwater energy storage device 200 by the floating crane 3510 and / or winch (3918);

[0589] j. Assessing whether the storage tank 100 is fully submerged (3920);

[0590] If the energy storage tank 200 is not fully submerged go back to step h, otherwise: k. Supplying the storage tank 100 with air while lowering the underwater energy storage device 200 for maintaining a balanced weight of the underwater energy storage device 200 under the maximal lifting weight capacity of the floating crane 3510 and / or winch (3922); l. Assessing whether the underwater energy storage device 200 has reached a final position site on the seabed 250 (3924);

[0591] If the underwater energy storage device 200 has not reached a final position site on the seabed 250 go back to step k, otherwise:

[0592] m. Stop lowering the underwater energy storage device 200 by the floating crane 3510 and / or winch (3926).

[0593]

[0594] In some embodiments, a plurality of storage tanks 100 is operated and managed. In some embodiments, the plurality of storage tanks 100 is at the same height, for example by being positioned on a flat surface in the seabed 250 or by being mounted on one or more bases 2302, as shown in Figure 40. In some embodiments, the plurality of storage tanks 100 are positioned at different heights. In some embodiments, the plurality of storage tanks 100 are stacked one on top of the other, for example as shown in Figures 41 and 42. In some embodiments, the plurality of storage tanks 100 is positionedon an inclined surface in the seabed 250 and each storage tank 100 from the plurality of storage tanks 100 is positioned in a different height, for example as shown in Figures 44A, 44B and 44C. In some embodiments, the plurality of storage tanks 100 being positioned at different heights acts as one unit in terms of receiving and releasing of compressed air. In some embodiments, a water level in each storage tank 100 from the plurality of storage tanks 100 is matched. In some embodiments, each storage tank 100 from the plurality of storage tanks 100 contains compressed air and / or water. In some embodiments, a water / air ratio increases with a decrease of a height of the storage tank 100. In some embodiments, each storage tank 100 from the plurality of storage tanks 100 experiences a net pressure which is the sum of the pressure exerted by the water outside and the opposite direction pressure exerted by the compressed air inside the storage tank 100. In some embodiments, a net pressure increase with an increase of a height of the storage tank 100 from the plurality of storage tanks 100. In some embodiments, reinforcement is provided for counterbalancing the net pressure exerted on the storage tank 100, optionally in the storage tank 100 positioned highest where the net pressure is higher.

[0595] Exemplary tanks configurations for operating at the same height

[0596] Referring now to Figure 40, showing a schematic representation of an underwater energy storage device comprising a plurality of storage tanks that have air flow communication between them positioned on one or more bases, according to some embodiments of the invention. In some embodiments, a device 4000 comprises an air flow pipe 4002 which branches into a plurality of pipes 4004 that directly communicate with a plurality of storage tanks 100. In some embodiments, the plurality of storage tanks 100 operates as one unit in terms of releasing and receiving of compressed air. In some embodiments, the plurality of storage tanks 100 is mounted on the one or more base 2302 such that the plurality of storage tanks 100 are leveled and are relatively at the same height in relation to one another. In some embodiments, the plurality of storage tanks 100 being leveled and relatively at the same height in relation to one another have a single valve configured for controlling air flow to and from the plurality of storage tanks 100. In some embodiments, potential advantages of having a plurality of storage tanks 100 acting as one unit being relatively in the same height is the following:

[0597] a. reducing the number of valves required for controlling air flow to and from the plurality of storage tanks 100.

[0598] b. enabling the use of a homogeneous variety of storage tanks 100 from the plurality of storage tanks 100 due to an even distribution of net pressure between the plurality of storage tanks 100.

[0599] c. Maximal capacity of stored compressed air of each storage tank 100 from the plurality of storage tanks 100 is independent on other storage tanks 100 from the plurality of storage tanks 100.In some embodiments, a plurality of air valves (not shown) are installed on the plurality of pipes 4004 for allowing individual control of air flow to and from the plurality of storage tanks 100. In some embodiments, a potential advantage of installing an air valve on the pipe 4004 is allowing isolation of one storage tank 100 from the rest of the plurality of storage tanks 100 for handling due to for example, maintenance.

[0600] Exemplary tanks configuration for operating at different heights

[0601] Referring now to Figure 41, showing a schematic representation of an underwater energy storage device comprising a plurality of individual units storage tanks stacked one of top of the other, according to some embodiments of the invention. In some embodiments, the plurality of storage tanks 100 are stacked one on top on the other such that each of the storage tanks from the plurality of storage tanks 100 is positioned at a different height. In some embodiments, device 4100 comprises an air flow pipe 4002 which branches into the plurality of pipes 4004 that are directly connect to the plurality of storage tanks 100. In some embodiments, air flowing via pipes 4004 is controlled according to a plurality of valves 4102. In some embodiments, each of the storage tanks from the plurality of storage tanks 100 differ in a pressure of the stored compressed air. In some embodiments, potential advantages of stacking the plurality of storage tanks 100 is minimizing an occupied space by the underwater energy storage device 4100 on the seabed 250 and lowering a cost of a positioning of the storage tank 100.

[0602] Referring now to Figure 42, showing a schematic representation of an underwater energy storage device including a combination of storage tanks that have air and water flow communication between them, according to some embodiments of the invention. In some embodiments, device 4200 comprises a vertical arrangement of storage tanks comprising the storage tank 100 located in the bottom of the device including the one or more water openings 204 and the storage tank 4202 connected vertically to the one or more storage tanks 100 by one or more connectors 4204 allowing passage of water and air. The device 4200 further comprises the one or more air pipes 202 for receiving and releasing of air. In some embodiments, the underwater energy storage device 4200 is fabricated on land and is then mobilized in parts to the submerging site on the seabed 250. In some embodiments, potential advantages of mobilizing the underwater energy storage device 4200 in parts to the submerging site on the seabed 250 are the following: enabling the use of simpler and / or less expensive equipment requiring smaller weight lifting capacity and requiring minimal area on the seabed 250, allowing more volume of compressed air to be stored in the same seabed 250 area, both which leads to reducing costs for positioning and operating the underwater energy storage device 4200.Referring now to Figure 43, showing a schematic representation of an underwater energy storage device comprising a plurality of closed tanks that have gas flow communication between them, according to some embodiments of the invention. In some embodiments, a device 4300 comprises a gas flow pipe 4002 which branches into the plurality of pipes 4004, which are attached to a plurality of storage tanks 4302. In some embodiments, the plurality of storage tanks 4302 operates as one unit in terms of receiving and releasing compressed gas. In some embodiments, optionally, each storage tank 4302 from the plurality of storage tanks 4302 is a closed storage tank having no openings for flow of water. In some embodiments, potential advantages of having a plurality of closed storage tanks 4302 operating as one unit are the following:

[0603] a. Preventing sand accumulation in the storage tank 4302.

[0604] b. Prevention of moisture in the gas stored in the storage tank 4302 since water do not enter the storage tank 4302.

[0605] Maximal volume capacity of stored compressed air of each storage tank 4302 from the plurality of storage tanks 4302 is independent on a height of other storage tanks 4302 from the plurality of storage tanks 4302. In some embodiments, the compressed gas stored in a storage tank from the plurality of storage tanks 4302 has a volume which is constant with an increase of pressure of the compressed gas. In some embodiments, the compressed gas stored in the storage tank from the plurality of storage tanks 4302 undergoes a transition from gaseous phase to liquid phase in temperature and pressure conditions according to a phase diagram of the material of the compressed gas. In some embodiments, the storage tank from the plurality of storage tanks 4302 stores the liquid phase of the compressed gas. In some embodiments, a potential advantage of storing the compressed gas in the liquid phase is increasing the storage capacity of the compressed gas.

[0606] Referring now to Figure 44A, showing a schematic representation of an underwater energy storage device comprising a plurality of storage tanks having air and water flow communication between them, according to some embodiments of the invention. In some embodiments, a device 4400 comprises the storage tank 100 comprising one or more water openings 204 and a plurality of enclosed storage tanks 4402. In some embodiments, the device 4400 is positioned on an inclined surface in the seabed 250. In some embodiments, each of the storage tank 100 and the plurality of enclosed storage tanks is connected to one or two neighboring tanks by a pipe 4404 by a plurality of connectors 4404 for enabling transfer of air and / or water. In some embodiments, the storage tank 100 is positioned in a lowest height of the device 440. In some embodiments, an enclosed storage tank 4402 from the plurality of enclosed storage tanks 4402 positioned in a highest height is connected to the one or more air pipes 202 for communicating the device 4400 to a compressor and / or an air outlet (not shown in figure). In some embodiments, during the receiving of compressed air to the device 4400, compressedair is supplied via the one or more air pipes 202 to occupy first the upmost enclosed storage tank 4402 from the plurality of enclosed storage tanks 4402 followed by the occupying of a lower enclosed storage tank 4402 from the plurality of enclosed storage tanks 4402 and lastly occupying the storage tank 100 such that a water level 4406 exists in the storage tank 100. In some embodiments, during the releasing of compressed air from the device 4400, water enter via the one or more water openings 204 to gradually occupy the storage tank 100 and the plurality of enclosed storage tanks 4402, in a time sequence according to a height of the storage tank 100 and the plurality of enclosed storage tanks 4402. In some embodiments, the connectors 4404 from the plurality of connectors 4404 connects two neighboring tanks from the plurality of enclosed storage tanks 4402 and storage tank 100 from an upper opening 4408 from a plurality of upper openings 4408 to a lower opening 4410 from a plurality of upper openings 4410. In some embodiments, a potential advantage of a connector 4404 connecting an upper opening 4408 from a plurality of upper openings 4408 to a lower opening 4410 from a plurality of upper openings 4410 is efficient water and / or air transfer.

[0607] Referring now to Figure 44B, showing a schematic representation of an underwater energy storage device comprising a plurality of storage tanks having air flow communication between them, according to some embodiments of the invention. In some embodiments, a device 4430 comprises the air flow pipe 4002 which branches into the plurality of pipes 4004 that directly connect to the plurality of storage tanks 100 positioned on an inclined surface on the seabed 250. In some embodiments, one or more storage tank 100 from the plurality of storage tanks 100 connects to the outside water by one or more downward facing water pipes 4432 which are attached to the one or more water openings 204. In some embodiments, each downward facing water pipe 4432 from the one or more downward facing water pipes 4432 comprise a water opening 4434 for enabling entry and / or exit to and / or from the storage tank 100. In some embodiments, one or more storage tank 100 from the plurality of storage tanks 100 positioned in a lowest height of the device 4430 contains water and compressed air having the water level 4406. In some embodiments, due to hydrostatic pressure, water and compressed air contained in the one or more downward facing water pipes 4432 has the water level 4406. In some embodiments, a potential advantage of equipping the device 4430 with one or more downward facing water pipes 4432 connecting the storage tank 100 with the outside water is lowering the water level 4406 in the device 4430 and increasing a compressed air capacity of the device 4430.

[0608] Referring now to Figure 44C, showing a schematic representation of an underwater energy storage device comprising a plurality of storage tanks having air and water flow communication between them, according to some embodiments of the invention. In some embodiments, a system 4460 comprises the air flow pipe 4002 which branches into the plurality of pipes 4004 that directlyconnect to the plurality of storage tanks 100. In some embodiments, the plurality of storage tanks 100 are positioned in different heights to match a slope in the seabed 250.

[0609] In some embodiments, the air flow pipe 4002 has a sealed end 4002A. In some embodiments, the system 4460 is configured such that the sealed end 4002A is positioned at a height which is at least equal (or higher) to a highest portion of the storage tank 100. A potential advantage of the sealed end 4002A is positioned at a height which is at least equal or higher to the highest portion of the storage tank 100 is preventing water accumulation in the air flow pipe 4002.

[0610] In some embodiments, the plurality of pipes 4004 are made of a rigid material. In some embodiments, the air flow pipe 4002 is made of a rigid material. A potential advantage of the plurality of pipes 4004 or the air flow pipe 4002 being made of a rigid material is preventing formation of pockets or depressions in which water may be accumulated.

[0611] In some embodiments, each storage tank 100 from the plurality of storage tanks 100 connects to a main water pipe 4462 by the one or more downward facing water pipes 4432 which are attached to the one or more water openings 204. In some embodiments, the main water pipe 4462 is positioned in an oblique angle to the surface of the earth, the oblique angle being generally following the slope in the seabed 250. In some embodiments, the main water pipe 4462 comprises a water opening 4464 located in a part of the main water pipe 4462 positioned at a lower height, optionally in a first end of the main water pipe 4462, for enabling entry of water from the outside water to the main water pipe 4462 and vice versa. In some embodiments, the water opening 4464 is positioned at a height that is at most equal to a height of a lowest positioned storage tank 100 from the plurality of storage tanks 100. In some embodiments, the main water pipe 4462 has a sealed second end 4466 which is positioned higher to the first end. In some embodiments, due to hydrostatic pressure, water entering the system 4460 via the water opening 4464 has the unanimous water level 4406, i.e., a uniform water level across exists throughout the system 4460. In some embodiments, a potential advantage of equipping the device 4460 with the main water pipe 4462 having the water opening 4464 positioned at a height that is at most equal to a height of a lowest positioned storage tank 100 from the plurality of storage tanks 100 is increasing a compressed air capacity of the device 4460 since the water level 4406 is not dependent on the location of the one or more water openings 204 in the lowest positioned storage tank 100 from the plurality of storage tanks 100.

[0612] Exemplary systems for prevention of water entry to the air pipe

[0613] In some embodiments, water accumulated in the one or more air pipes 202 may harm the efficiency of the underwater energy storage device 200, for example the water may limit the air flow during receive and release of compressed air. In some embodiments, prevention of water entry to the one or more air pipes 202 is desired.In some embodiments, an air valve located in the one or more air pipes 202 controls air release via the one or more air pipes 202 and additionally prevents water entry to the one or more air pipes 202. In some embodiments, sensors are located in the storage tank 100 and measure properties that give information on the water level, for example, water level and / or pressure and / or air volume in the storage tank 100. In some embodiments, a controller controls operation of the air valve according to the measurements.

[0614] Referring now to Figure 45A, showing a schematic representation of a system comprising a floating element for prevention of water from entering an air pipe positioned on a roof of the storage tank, according to some embodiments of the invention. In some embodiments, a floating element 4502 is located inside the storage tank 100, which in some embodiments, contains water 4506 at an exemplary water level 4508. In some embodiments, the storage tank 100 comprises an air opening from the one or more air openings 206 connected to an air pipe from the one or more air pipes 202 located on the storage tank roof 105. In some embodiments, the floating element 4502 is buoyant with regards to the water level 4508. In some embodiments, rise of the water level 4508 causes the floating element 4502 to come into contact and block the air opening from the one or more air openings 206, preventing water entry to the air pipe 202. In some embodiments, the floating element 4502 is confined in cage 4504 for prevention of movement of the floating element 4502 within the storage tank 100. In some embodiments, the floating element 4502 is made of polymeric materials having a lower density compared to water for example PE or PVV. Optionally, the floating element 4502 is coated with a sealing agent. In some embodiments, the floating element 4502 comprises a hermetically sealed shell (i.e., a balloon) filled with oil.

[0615] Referring now to Figure 45B, showing a schematic representation of a system comprising a floating element for prevention of water from entering an air pipe positioned on a roof of the storage tank, according to some embodiments of the invention. In some embodiments, a system 4550 comprises a floating element 4552 and a sealing layer 4554 positioned above the floating element 4552. In some embodiments, the floating element 4552 is made of polymeric materials having a lower density compared to water, for example PE or PVV. In some embodiments, the sealing layer 4554 is made of a waterproof flexible material for example, rubber or silicon. In some embodiments, a potential advantage of the sealing layer 4554 made of a flexible material is being able seal an opening surrounded with surfaces of various curvatures and smoothness. In some embodiments, the sealing layer 4554 is attached to the floating element 4554. In some embodiments, both the floating element 4552 and the sealing layer 4554 comprise one or more holes (not shown) traversing through the length of both the floating element 4552 and the sealing layer 4554 for allowing positioning of one or more vertical columns 4556 inside the one or more holes (not shown) and for allowing a vertical movementof the floating element 4552 and the sealing layer 4554. In some embodiments, the one or more vertical columns 4556 are connected in a one end to a ceiling of the storage tank 100. In some embodiments, the one or more vertical columns 4556 limits a lateral movement range of the floating element 4552 and the sealing layer 4554. In some embodiments, each vertical column from the one or more vertical columns 4556 is equipped with a blocker 4558 for limiting a vertical movement range for the floating element 4552 and the sealing layer 4554. In some embodiments, the floating element 4552 and the sealing layer 4554 are located inside the storage tank 100, which in some embodiments, contains water at an exemplary water level 4562. In some embodiments, the storage tank 100 comprises an air opening 206 from the one or more air openings 206 connected to an air pipe 202 from the one or more air pipes 202 located on the storage tank roof 105. In some embodiments, the floating element 4552 is buoyant with regards to the water level 4508. In some embodiments, a rise of the water level 4562 causes the floating element 4552 and the sealing layer 4554 to move in an upward direction towards the air opening 206 from the one or more air openings 206. In some embodiments, the sealing layer 4554 reaches and attaches to the air opening 206 from the one or more air openings 206 to seal it and prevent water entry to the air pipe 202 from the one or more air pipes 202.

[0616] Referring now to Figure 46, showing a schematic representation of a system comprising a floating element for preventing water from entering an air pipe, according to some embodiments of the invention. In some embodiments, a floating element 4604 is located inside the storage tank 100, which in some embodiments, contains water 4506 at an exemplary water level 4508. In some embodiments, the one or more air openings 206 are located in the wall of the storage tank 100. In some embodiments, an air pipe from the one or more air pipes 202 is connected to an air opening from the one or more air openings 206 located in the wall of the storage tank 100. In some embodiments, the floating element 4604 is connected to a closing element 4610, which is connected to a pivot 4602. In some embodiments, the floating element 4604 is buoyant with regards to water level 4508. In some embodiments, the closing element 4610 limits a movement of the floating element 4604. In some embodiments, a rise in the water level 4508 causes the floating element 4604 to rise, which then causes the closing element 4610 to move in the direction presented by arrow 4606, which is in the direction of the air opening 206 to block it and prevent water to enter into the air pipe from the one or more air pipes 202. In some embodiments, when the floating element 4604 reaches a maximal height, the rise the water level 4508 leads to a submerging of the floating element 4604. In some embodiments, due to the submerging of the floating element 4604, an upward buoyancy force is exerted on the floating element 4604 and the attached closing element 4610 which increases a blocking effect of the air opening 206.Exemplary systems for evacuation of water from an air pipe

[0617] Exemplary mobile robot device for evacuation of water from an air pipe

[0618] In some embodiments, water may enter the one or more air pipes 202 and as such, evacuation of water from the one or more air pipes 202 is desired.

[0619] Referring now to Figure 47, showing a schematic representation of a mobile robot for evacuating water from an air pipe, according to some embodiments of the invention. In some embodiments, a mobile robot device 4700 is used for the evacuation of water from the one or more air pipes 202. In some embodiments, preferably, the mobile robot device 4700 evacuates water to a downward heading side in the air pipe 202 from the one or more air pipes 202 to be poured into the storage tank 100. In some embodiments, the mobile robot device 4700 comprises a body 4702 and at least one wheel 4704. In some embodiments, the mobile robot 4700 further comprises a water pump (not shown in the figure) comprised in the body 4702, a suction tube 4706 for evacuating water from the one or more air pipes 202. In some embodiments, the mobile robot 4700 further comprises a front exhaust tube 4708 for releasing the water into the storage tank 100. Optionally, the mobile robot device further comprises a rear exhaust tube 4710 for releasing water to the outside the energy storage tank 100. In some embodiments, the mobile robot device 4700 comprises a battery (not shown in Figure 47). In some embodiments, the mobile robot device 4700 comprises a motor (not shown). In some embodiments, the mobile robot device 4700 is attached to a safety wire 4710 for retrieval of the mobile robot device 4700. In some embodiments, the mobile robot device 4700 comprises an illumination source 4716. In some embodiments, the mobile robot device 4700 comprises a camera 4714. In some embodiments, a potential advantage of a mobile robot device 4700 comprising a camera 4714 is potentially facilitating air pipe maintenance data collection. In some embodiments, the mobile robot device 4700 is operated autonomously. Optionally, the mobile robot device 4700 is operated remotely. In some embodiments, mobile robot device 4700 is attached to a wire and / or a cable (not shown) for connecting the mobile robot device 4700 with a power source and / or a controller (not shown).

[0620] Referring now to Figure 48, showing a schematic representation of a mobile robot device for evacuating water from one or more air pipes, according to some embodiments of the invention. In some embodiments, a mobile robot device 4700 is positioned inside an air pipe from the one or more air pipes 202 and evacuates water 4802 from an air pipe low part 4804 from one or more air part low parts, in which water is most likely to accumulate. In some embodiments, as mentioned above, the mobile robot device 4700 comprises a suction tube 4706 contacting and pumping water 4802, a front exhaust tube 4708 for releasing water to an overall downward direction and a rear exhaust tube 4710 for releasing water.In some embodiments, one or more water valves are positioned in the air pipe low part 4804 from the one or more air pipe low parts configured for controlling release of the water 4802 to an outside water environment. In some embodiments, the one or more water valves are operated remotely. In some embodiments, the air pressure in an air pipe from the one or more air pipes 202 is higher than a water pressure outside the air pipe low part 4804. In some embodiments, upon opening of a water valve from the one or more water valves positioned in the air pipe low part 4804 from the one or more air pipe low parts, water 4802 are released via the water valve from the one or more water valves to the outside water environment.

[0621] Referring now to Figure 49, showing a flow chart of an exemplary method of evacuating water from an underwater air pipe using a mobile robot device, according to some embodiments of the invention.

[0622] In some embodiments, an exemplary method of evacuating water from an underwater air pipe using a mobile robot device comprises:

[0623] 1. Providing a mobile robot device 4700 having a pump and a suction tube 4706 for water evacuation (4902);

[0624] 2. Positioning the mobile robot device 4700 in the air pipe 202 (4904);

[0625] 3. Mobilizing the mobile robot device 4700 to the water to be evacuated 4802 (4906); and 4. Pumping the water 4802 via the suction tube 4706 (4908);

[0626] 5. Releasing the water 4802 to an overall downward direction (4910).

[0627] Exemplary pistons for evacuation of water from an air pipe

[0628] In some embodiments, a piston evacuates water by pushing water away from the one or more air pipes 202, the piston being moveable within the one or more air pipes 202.

[0629] Referring now to Figure 50, showing a schematic representation of a piston for evacuation of water in an air pipe, according to some embodiments of the invention. In some embodiments, a piston 5002 is located within an air pipe 202. In some embodiments, the piston 5002 is connected to a controller via a wire (not shown). In some embodiments, the piston 5002 comprises an adjustable balloon. In some embodiments, a potential advantage of a piston comprising an adjustable balloon is potentially enabling reduction of the diameter of the piston 5002 to dislodge from the air pipe 202.

[0630] In some embodiments, the piston 5002 comprises a camera. In some embodiments, a potential advantage of the piston 5002 comprising a camera is potentially facilitating air pipe maintenance data collection.

[0631] In some embodiments, the piston 5002 comprises an illumination source.

[0632] Referring now to Figure 51 A, showing a schematic representation of a piston for evacuation of water in an air pipe, according to some embodiments of the invention. In some embodiments, apiston 5002 located within an air pipe 202 (not shown) comprises a main body 5102 having one or more openings 5104 traversing through the length of the piston 5002 and one or more piston flaps 5106 being a thin sheet configured for covering the one or more openings 5104 and prevents air passage via the one or more openings 5104. In some embodiments, the piston flaps 5106 are connected to an exterior of the piston 5002 in a side facing the water to be evacuated (not shown) by one more pivots 5108 configured for enabling rotational motion of the one or more piston flaps 5106 for controlling a passage of air via the one or more openings 5104. In some embodiments, the piston 5002 is attached to one or more retrieval wires 5110 for retrieving the piston 5002 following the water evacuation. In some embodiments, the piston 5002 is moved in the air pipe 202 for evacuation of water (not shown). In some embodiments, during the moving the piston 5002 in the air pipe 202 for evacuation of water, the one or more piston flaps 5106 are pushed to cover the one or more openings 5104 due to a resistance of air. In some embodiments, the covering of the one or more openings 5104 seal the piston 5002 and prevent air and water passage via the one or more openings 5104 such that water can be evacuated.

[0633] Referring now to Figure 5 IB, showing a schematic representation of a piston for evacuation of water in an air pipe during piston retrieval, according to some embodiments of the invention. In some embodiments, following an evacuation of water the piston 5002 is retrieved to a base location to be removed from the air pipe 202. In some embodiments, the piston 5002 is retrieved by pulling the one or more retrieval wires 5110. In some embodiments, during the retrieval of the piston 5002 in the air pipe 202, the piston 5002 moves in a closed system such that during the pulling of the piston 5002 by the one or more retrieval wires 5110, air pushes the one or more piston flaps 5106 which pivots by the one more pivots 5108, thus enabling passage of air via the one or more openings 5104 and preventing vacuum formation.

[0634] Referring now to Figure 52A, showing a schematic representation of a water evacuating system for air pipe using a water-soluble piston, according to some embodiments of the invention. In some embodiments, an area in the air pipe 202 that requires handling by the piston 5002 due to water accumulation is located in an underwater location. In some embodiments, it is desirable to have the piston 5002 be dissolvable, such that a need for retrieving the piston 5002, for example due to malfunctioning, is eliminated. In some embodiments, an air pipe 202 comprises an opening 5202 for inserting the piston 5002 into the air pipe 202 and a sealing element 5206 having a shape suitable for covering the opening 5202. In some embodiments, the opening 5202 is located outside the waterbody the storage tank 100 is positioned in, such that the piston 5002 is administered to the air pipe 202 outside the waterbody. In some embodiments, the diameter of the piston 5002 is reduced with time and / or exposure to water. In some embodiments, the piston 5002 is made of water soluble materialfor example PVA, ice, sugar and / or salt. In some embodiments, potential advantages of a piston 5002 made of a water-soluble material is eliminating the risk for the piston 5002 of being stuck in the air pipe 202 and eliminating the need to retrieve the piston 5002. In some embodiments, the piston 5002 is coated with a water soluble material, for example PVA.

[0635] Referring now to Figure 52B, showing a schematic representation of a water evacuating system from air pipe using a water soluble piston, according to some embodiments of the invention. In some embodiments, an air pipe 202 is sealed by sealing element 5206. In some embodiments, the piston 5002 is located and moveable within the air pipe 202.

[0636] Referring now to Figure 53, showing a flow chart of an exemplary method of evacuating water from an underwater air pipe by pushing water using a piston, according to some embodiments of the invention.

[0637] In some embodiments, an exemplary method of evacuating water from an underwater air pipe by pushing water using a piston comprises:

[0638] 1. Providing a piston (5302);

[0639] 2. Positioning the piston in an air pipe (5304); and

[0640] 3. Moving the piston to push water by applying air pressure (5306).

[0641] Exemplary metal storage tanks

[0642] Referring now to Figure 54A, showing a schematic representation of an energy storage device comprising a metal storage tank, according to some embodiments of the invention. It is known that metals, by their nature, are ductile which allows them to absorb and distribute tensile stress effectively. Concrete, on the other hand has a high compressive strength but relatively low tensile strength. The present inventors have found that a storage tank made of metal equipped with concrete element can have beneficial properties for underwater compressed energy storage. In some embodiments, an energy storage device 5400 comprises a metal storage tank 5402 which is made of, for example steel or any other metal. In some embodiments, the thickness of the metal storage tank 5402 is lower compared to an equivalent concrete storage tank. Additionally, the metal storage tank 5402 has a smaller weight relative to an equivalent concrete storage tank. In some embodiments, the metal storage tank 5402 has the following potential advantages:

[0643] a. requires simpler equipment to transfer the energy storage device 5400 (e.g., during shipping to a submerging site, during lifting, during submerging etc.) due to the relatively small weight. b. High durability to tensile stress exerted on the metal storage tank 5402.

[0644] In some embodiments, the metal storage tank 5402 has at least one storage tank wall 5403, a roof 5404 and a metal storage tank floor 5410 having a thickness, for example, from about 1mm to 20mm, optionally from about 2mm to about 8mm, optionally from about 3mm to about 15mm. Insome embodiments, the at least one storage tank wall 5403 has a sandwich structure comprising an outer metal layer, intermediate cement layer and an inner metal layer. In some embodiments, weights 1506 are distributed on the energy storage device 5400. In some embodiments, a potential advantage of the weights 1506 being distributed on the energy storage device 5400 is exerting gravitational force which counterbalances a buoyancy force exerted on the energy storage device 5400. In some embodiments, the roof 5404 has a shape, for example dome, flat or conical surface. In some embodiments, the roof 5404 is equipped with an upper banister 5406 for containing the weights 1506.

[0645] In some embodiments, optionally, a horizontal platform 5406 having a lower part designed to contact the roof 5404 is positioned on the roof 5404. In some embodiments, the horizontal platform 5408 is contained in a space defined by the upper banister 5406. In some embodiments, the weights 1506 are distributed on the horizontal platform 5406. In some embodiments, the horizontal platform 5408 is a concrete cast. In some embodiment, the horizontal platform 5408 is made of one or more of sand, gravel and fillers.

[0646] In some embodiments, the metal storage tank 5402 is equipped with the peripheral edges 1402.

[0647] In some embodiments, the weights 1506 are distributed on the peripheral edges 1402. In some embodiments, the lower banister 1704 is positioned on the peripheral edges 1402 for containing the weights 1506 which are positioned on the peripheral edges 1402. In some embodiments, positioning the weights 1506 on the peripheral edges 1402 shifts a center of weight of the energy storage device 5400 to a lower part of the energy storage device 5400. In some embodiments, a potential advantage of lowering the center of weight of the energy storage device 5400 is enhancing stability of the energy storage device 5400 against tipping or overturning. In some embodiments, the energy storage device 5400 comprises the one or more water pipes 1602 which enable water flow to and from the metal storage tank 5402. In some embodiments, the one or more water pipes 1602 are at least partially embedded in the lower banister 1704 such that one or more pipe openings of the one or more water pipes 1602 extend beyond the space defined by the lower banister 1704. In some embodiments, a potential advantage of the one or more water pipes 1602 is preventing an interruption to water flow due to the weights contained in the space defined by the lower banister 1704.

[0648] Exemplary structural reinforcements to the metal storage tank

[0649] In some embodiments, the metal storage tank 5402 is subjected to tensile force. In some embodiments, a horizontal tensile force is exerted on the metal storage tank 5402 by a difference in the pressure between the external seawater environment and the internal compressed air environment, and a vertical tensile force is exerted on the metal storage tank 5402 by the upward buoyancy of the compressed air and the downward gravitational force. In some embodiments, the metal storage tank 5402 is equipped with structural reinforcing elements for reinforcing the metal storage tank 5402 towithstand the tensile force. In some embodiments, one or more columns 5412 are positioned such that one end contacts the metal storage tank floor 5410 and the other end contacts the roof 5404 for redistribution the weight of the structure above the one or more columns 5412. In some embodiments, the metal storage tank floor 5410 is made of one or more of metal and concrete. In some embodiments, the weight of the structure above the one or more columns 5412 includes the weight of the roof 5404, the weight of the horizontal platform 5408 and the weights 1506. In some embodiments, a potential advantage of the one or more columns 5412 redistributing the weight of the structure above is preventing collapse of the roof 5404. In some embodiments, the one or more columns 5412 are made of high strength materials, for example metal. In some embodiments, the one or more columns 5412 are attached to the metal storage tank floor 5410 by one or more of welding and inserting screws. In some embodiments, the one or more columns 5412 are attached to the roof 5404 by one or more of welding and inserting screws. In some embodiments, optionally, angle brackets (not shown in figure) are positioned between at least one side of the one or more columns 5412 and the metal storage tank floor 5410 for reinforcing the metal storage tank 5402 by redistributing the weight of the structure above. In some embodiments, the one or more columns 5412 comprise a metal casing and a concrete core. In some embodiments, a potential advantage of the one or more columns 5412 comprising a metal casing and a concrete core is preventing collapse of the one or more columns 5412 due to the high resistance of the concrete to compression forces. In some embodiments, the one or more columns 5412 are positioned vertically to the metal storage tank floor 5410. In some embodiments, a potential advantage of the one or more columns 5412 positioned vertically to the metal storage tank floor 5410 is reinforcing the metal storage tank 5402 to withstand an outward vertical tensile force exerted on the metal storage tank 5402. In some embodiments, the one or more columns 5412 are positioned in an oblique angle to the metal storage tank floor 5410. In some embodiments, a potential advantage of the one or more columns 5412 positioned in an oblique angle to the metal storage tank floor 5410 is reinforcing the metal storage tank 5402 to further withstand an outward horizontal force due to outside environmental conditions, for example water currents. In some embodiments, the one or more columns 5412 are positioned adjacent to the wall of the metal storage tank 5402, for example in inside or outside the metal storage tank 5402. In some embodiments, a potential advantage of the one or more columns 5412 positioned adjacent to a wall of the metal storage tank 5402 is reinforcing the wall of the metal storage tank 5402.

[0650] In some embodiments, the metal storage tank 5402 is equipped with one or more flexible linear elements 5414 which are connected to the metal storage tank floor 5410 in an element one end 5416A and the roof 5404 in an element second end 5416B. In some embodiments, the one or more flexible linear elements 5414 are tensioned for redistribution of forces exerted on the metal storage tank 5402due to a difference in the pressure between the external seawater environment and the internal compressed air environment. In some embodiments, a potential advantage of the metal storage tank 5402 being equipped with the one or more flexible linear elements 5414 in a tensioned state enhancing the durability of the metal storage tank 5402 to withstand tensile forces. In some embodiments, the one or more flexible linear elements 5414 are positioned vertical to the roof 5404 and / or the metal storage tank floor 5410 as shown in the figure. Additionally or alternatively, the one or more flexible linear elements 5414 are positioned in an oblique angle to the roof 5404 and / or the metal storage tank floor 5410, providing reinforcement in different angles. In some embodiments, the one or more flexible linear elements 5414 in made of for example, metal cable or polymer.

[0651] In some embodiments, the metal storage tank floor 5410 is reinforced with beams, for example double T or double H.

[0652] Referring now to Figure 54B, showing a schematic representation of a top view of a star shaped column positioned in a metal storage tank, according to some embodiments of the invention. In some embodiments, the metal storage tank 5402 is equipped with a star shaped column 5418 positioned inside the metal storage tank 5402, such that one end contacts the metal storage tank floor 5410 and the other end contacts the roof 5404 (not shown in figure). In some embodiments, the star shaped column 5418 is made of a high strength material, for example concrete and / or metal. In some embodiments, potential advantages of the star shaped column 5418 positioned in the metal storage tank 5402 are the following:

[0653] a. the star shape increases resistance to lateral forces coming from various angles by providing support in multiple directions.

[0654] b. the star shape has more surface area in contact with the roof 5404 and the metal storage tank floor 5410 compared to a rectangular shape. This increased contact area helps distribute forces more evenly and effectively, reducing stress concentrations.

[0655] In some embodiments, the star shaped column 5418 has a diameter 5418A. In some embodiments, the diameter 5418A is at least 20% of a width of the metal storage tank floor 5410A.

[0656] In some embodiments, the star shaped column 5418 is positioned in a center of the metal storage tank 5402 and in some embodiments, the star shaped column 5418 is positioned in the periphery of the metal storage tank 5402.

[0657] Exemplary inner protective coatings

[0658] Most metals by nature, are susceptible to corrosion. In some embodiments, the interior of the metal storage tank 5402 is subjected to highly corrosive conditions due to the presence of compressed air and optionally saltwater. In some embodiments, the metal storage tank 5402 is coated with an internal coating for isolating the interior of the metal storage tank 5402 from the compressed air andoptionally saltwater contained in the metal storage tank 5402, the internal coating comprising for example one or more of Polyurea, epoxy and polyethylene. In some embodiments, the interior of the metal storage tank 5402 is galvanized. In some embodiments, a potential advantage of the interior of the metal storage tank 5402 being galvanized is prevention of metal corrosion in the interior of the metal storage tank 5402. In some embodiments, active cathodic protection is provided to the interior of the metal storage tank 5402. Alternatively or additionally, passive cathodic protection is provided to the interior of the metal storage tank 5402.

[0659] Exemplary anchoring of the metal storage tank

[0660] In some embodiments, the energy storage device 5400 is equipped with anchoring means, for example, foundations, caisson anchors and anchor points. In some embodiments, the anchor points, as described in Figure 20A, are equipped with cables for connecting the energy storage device 5400 with the point anchors. In some embodiments, the cables are positioned on the energy storage device 5400. In some embodiments, a potential advantage of the cables being positioned on the energy storage device 5400 is further anchoring the energy storage device 5400 to the seabed 250.

[0661] In some embodiments, holes are created in rock formations. In some embodiments, the anchoring means are installed in the holes. In some embodiments, a potential advantage of creating holes in rock formations to install the anchoring means is providing stable and secure anchoring to the seabed 250.

[0662] Exemplary closed metal storage tank

[0663] Referring now to Figure 55, showing a schematic representation of an energy storage device comprising a closed metal storage tank, according to some embodiments of the invention. In some embodiments, the energy storage device 5500 comprises a closed metal storage tank 5502, i.e., the closed metal storage tank 5502 does not comprise water openings. In some embodiments, potential advantages of the closed storage tank 5502 are preventing sand accumulation and preventing humidity in a compressed gas stored in the closed storage tank 5502. In some embodiments, the compressed gas stored in the closed metal storage tank 5502 has a volume which is constant with an increase of pressure of the compressed gas. In some embodiments, the compressed gas stored in the closed metal storage tank 5502 undergoes a transition from gaseous phase to liquid phase in temperature and pressure conditions according to a phase diagram of the material of the compressed gas. In some embodiments, the closed metal storage tank 5502 stores the liquid phase of the compressed gas. In some embodiments, a potential advantage of storing the compressed gas in the liquid phase is increasing the storage capacity of the compressed gas.

[0664] In some embodiments, the energy storage device 5500 further comprises the one or more air pipes 202 connected to the one or more air openings 206. In some embodiments, a portion of the oneor more air pipes 202 which is in proximity to the one or more air openings 206 contact an exterior of the closed metal storage tank 5502. In some embodiments, the portion of the one or more air pipes 202 which contact the exterior of the closed metal storage tank 5502 is anchored to the closed metal storage tank 5502. In some embodiments, a potential advantage of the portion of the one or more air pipes 202 which is in proximity to the one or more air openings 206 being anchored to the closed metal storage tank 5502 is enhancing the structural durability of the connection of the one or more air pipes 202 to the closed metal storage tank 5502 and reducing the probability to failure in the connection located in the one or more air openings 206. In some embodiments, the portion of the one or more air pipes 202 which is in contact with the exterior of the closed metal storage tank 5502 comprises a first linear part 202A which attaches to a length of the closed metal storage tank 5502 and a second part 202B which connects to the one of more air openings 206, the first linear part 202A and the second part 202B having an angle between them. In some embodiments, the angle ranges from about 1 degree to about 90 degrees, optionally from about 20 degrees to about 60 degrees, optionally from about 30 degrees to about 50 degrees.

[0665] In some embodiments, the portion of the one or more air pipes 202 which is in contact with the exterior of the closed metal storage tank 5502 surround the exterior of the closed metal storage tank 5502 in a spiraling shape, eliminating sharp angles. The potential advantages of the one or more air pipes 202 having a spiraling shape were described previously in relation to Figure 4B.

[0666] Exemplary energy storage device comprising tubular structures

[0667] Referring now to Figure 56, showing a schematic representation of an energy storage device comprising a tubular structure, according to some embodiments of the invention. In some embodiments, an energy storage device 5600 comprises a tubular structure 5602, which is used to store the compressed gas. In some embodiments, the tubular structure 5602 defines at least one internal lumen configured to contain compressed gas therein. As used herein, the term ’’tubular structure” means any prefabricated, hollow, load-bearing or containment elements that are designed for storage, structural reinforcement, or fluid management.

[0668] In some embodiments, the tubular structure 5602 is, for example, a pipe.

[0669] In some embodiments, the tubular structure 5602 is recycled, repurposed, or adapted from preexisting industrial components, such as industrial gas pipes, structural tubing, or other manufactured hollow structures. A potential advantage of energy storage device 5600 comprising the tubular structure 5602 is reducing costs of manufacturing of the energy storage device 5600.

[0670] Alternatively, the tubular structure 5602 is specifically designed and manufactured for use in the energy storage device 5600. A potential advantage of the tubular structure 5602 being specifically designed and manufactured for use in the energy storage device 5600 is allowing for customizeddimensions, materials, and structural features to optimize performance and efficiency of the energy storage device 5600.

[0671] In some embodiments, the tubular structure 5602 has a profile which defines the cross-sectional shape of the tubular structure 5602. Examples of possible profiles include circular and rectangular.

[0672] In some embodiments, the width of the tubular structure 5602 is from about 1 meter to about 7 meters, optionally from about 3 meters to about 10 meters, optionally from about 5 meters to about 15 meters.

[0673] In some embodiments, the tubular structure 5602 is positioned vertically on the seabed 250, and, in some embodiments, the tubular structure 5602 is positioned generally horizontally in relation to the seabed 250, for example as shown in Figures 61-63B.

[0674] In some embodiments, the tubular structure 5602 is made of, for example metal, PVC, cement or combination of metal, and / or PVC, and / or cement.

[0675] In some embodiments, the tubular structure 5602 has an open top 5604. Optionally, the open top 5604 is enclosed by a cover 5606.

[0676] In some embodiments, the cover 5606 is flat, and, in some embodiments, the cover 5606 is dome shaped. In some embodiments, the cover 5606 is attached to the tubular structure 5602, for example by soldering or gluing the cover 5606 to the tubular structure 5602.

[0677] In some embodiments, a weight 5608 is positioned on top the cover 5606 and, in some embodiments, the weight 5608 is positioned directly on top the tubular structure 5602. A potential advantage of the weight 5608 is enhancing the structural stability of the energy storage device 5600.

[0678] In some embodiments, the tubular structure 5602 is partially immersed within the weight 5608.

[0679] In some embodiments, the weight 5608 is cement cast. In some embodiments, the cement cast is cast during manufacturing of the energy storage device 5600 in a manufacturing facility on land, and in some embodiments, the cement cast is cast onto the cover 5606 when the energy storage device 5600 is submerged in seawater, before or after landing on the seabed 250.

[0680] In some embodiments, the tubular structure 5602 is attached to a weight platform 5610. In some embodiments, the platform 5610 is made of cement. A potential advantage of the tubular structure 5602 being attached to the weight platform 5610 is preventing the tubular structure 5602 from floating.

[0681] In some embodiments, the tubular structure 5602 is at least partly immersed within the weight platform 5610. In some embodiments, one or more anchoring rods 5612 anchor the tubular structure 5602 to the weight platform 5610. In some embodiments, each of the one or more anchoring rods 5612 comprises an embedded anchor 5614 for anchoring the weight platform 5610 and connector5616 for connecting the embedded anchor 5614 with the tubular structure 5602. A potential advantage of the one or more anchoring rods 5612 enabling efficient force distribution.

[0682] In some embodiments, at least one of the plurality of tubular structures is substantially sealed against ingress of water from the surrounding underwater environment and is configured to allow gas flow while preventing water entry. In such embodiments, the tubular structure does not comprise water openings permitting free water communication with the surrounding environment. Optionally, the tubular structure is hermetically sealed except for one or more gas connectors configured for transferring compressed gas into and / or out of the tubular structure. In some embodiments, all of the plurality of tubular structures are substantially sealed against ingress of water and do not comprise water openings permitting free water communication with the surrounding underwater environment.

[0683] Exemplary energy storage device comprising a cluster of tubular structures

[0684] Exemplary energy storage device comprising gas and / or water connection

[0685] Traditionally, large-diameter pressure vessels present significant engineering challenges. As the diameter of a pressure vessel increases, the stress on its walls also increases, necessitating a greater wall thickness. This results in complex construction requirements, including extensive manual welding, which significantly raises costs. Additionally, the size and weight of such large vessels create logistical challenges, such as crane lifting limitations and constraints at docking sites for marine deployment.

[0686] The present inventors have found that clustering a plurality of the tubular structures 5602, which are fluidly connected to one another, provides an effective alternative to large-diameter pressure vessels. By using multiple smaller-diameter tubular structures instead of a single large vessel, mechanical loads are more evenly distributed across the system, reducing the need for excessively thick walls and minimizing construction complexity.

[0687] Referring now to Figures 57A-B, showing a schematic representation of a cross-sectional of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention. In some embodiments, an energy storage device 5700 comprises a cluster comprising a plurality of the tubular structure 5602, optionally, vertically extending tubular structures. In some embodiments, each of the plurality of the tubular structures 5602 extends along a substantially vertical axis when the energy storage device 5700 is deployed, for example, when positioned on a seabed. In such embodiments, for example, a lower end of each tubular structure 5602 is positioned adjacent to or supported by the seabed, and a longitudinal axis of each tubular structure extends upwardly away from the seabed such that the cluster is arranged in an upright configuration rather than in a horizontal configuration along the seabed.In some embodiments, all the tubular structures 5602 are made of the same material, for example, all the tubular structures 5602 are made of metal, and, in some embodiments, at least one of the plurality of the tubular structures 5602 is made of a different material, for example, at least one of the plurality of the tubular structures 5602 is made of metal and the other tubular structures 5602 are made of cement.

[0688] In some embodiments, the plurality of tubular structures 5602 may be positioned and / or connected relative to one another laterally, for example side-by-side to form a cluster, and / or longitudinally, for example end-to-end to form a sequence of tubular structures extending along a longitudinal direction.

[0689] In some embodiments, the plurality of the tubular structures 5602 are attached to one another. In some embodiments, the plurality of the tubular structures 5602 are attached to one another by soldering to adhere the tubular structures 5602 to one another. Alternatively or additionally, a fastening mechanism (not shown in Figures 57A-B) is used to secure the plurality of the tubular structures 5602 together. In some embodiments, the fastening mechanism is, for example, a metal band, a metal cable, or structural frame.

[0690] In some embodiments, the plurality of tubular structures 5602 are fluidly inter-connected to one another by a plurality of connectors 5702. In some embodiments, the plurality of connectors 5702 allow transfer of water and gas between the plurality of tubular structure 5602, such that the plurality of the tubular structures 5602 operate as one unit in terms of receiving and / or releasing of compressed gas.

[0691] In some embodiments, at least one of the plurality of the tubular structures 5602 comprises the one or more air openings 206, the one or more air openings 206 being connected to one or more air pipes 202 (not shown in Figures 57A-B) for communicating the plurality of the tubular structures 5602 to a turbomachinery unit. In some embodiments, each of the plurality of the tubular structures 5602 comprises the one or more water openings 204, for example as shown in Figure 57A, and, in some embodiments, at least one of the tubular structures 5602 is sealed to the outside environment and does not comprise the one or more water openings 204, for example as shown in Figure 57B. In some embodiments, the one or more water openings 204 and / or the one or more air openings 206 are in fluid communication with the at least one internal lumen.In some embodiments, the plurality of the tubular structures 5602 are arranged in various configurations, for example round, hexagonal, or rectangular formations, depending on design and operational requirements.

[0692] Referring now to Figure 57C, showing a schematic representation of a cross-sectional view of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention. In some embodiments, the energy storage device 5700 comprises a cement cast 5704,which is positioned in between the plurality of the tubular structures 5602. A potential advantage of the cement cast 5704 positioned in between the plurality of the tubular structures 5602 is adhering to the plurality of the tubular structures 5602 and enhancing the structural stability of the energy storage device 5700.

[0693] Referring now to Figure 57D, showing a schematic representation of a cross-sectional view of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention. In some embodiments, between every three adjacent tubular structures 5602 arranged in a triangular formation, a gap 5705 is formed. In some embodiments, the gap 5705 is a chimney-like space (in view of the height of the tubular structures 5602). In some embodiments, the one or more water opening 204 are arranged to allow for water exchange between the plurality of the tubular structures 5602 and the water outside via the space.

[0694] Referring now to Figure 57E, showing a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention. In some embodiments, the energy storage device 5700 stores compressed gas. In some embodiments, the volume of the compressed gas stored in the energy storage device 5700 is defined by the water level 5706 inside the energy storage device 5700. In some embodiments, the plurality of connectors 5702 comprise connectors positioned at different heights of the energy storage device 5700. In some embodiments, the plurality of connectors 5702 comprise the following:

[0695] one or more high connectors 5702A which are mainly used for gas transfer, as they are located above the water level 5706 during gas storing;

[0696] one or more middle connectors 5702B which facilitate the exchange of both water and gas, depending on the water level 5706; and

[0697] one or more low connectors 5702C which are mainly used for water transfer, as they are located below the water level 5706 during gas storing. Referring now to Figure 57F, showing a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention. In some embodiments, one or more of the tubular structures 5602 are equipped with the weight 5608.

[0698] Referring now to Figure 57F, showing a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention. In some embodiments, an overall cover 5710 is positioned on top the tubular structures 5602 and the weight 5608. In some embodiments, the overall cover 5710 seals the plurality of the tubular structures 5602.

[0699] In some embodiments, the overall cover 5710 is configured to allow gas flow from the plurality of the tubular structures 5602 via the one or more air pipes 202.Referring now to Figure 57G, showing a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention. In some embodiments, the plurality of the tubular structures 5602 are connected to one or more gas connectors 5712, which connect each of the plurality of the tubular structures 5602 to one another and allow for gas transfer between the plurality of the tubular structures 5602, thereby facilitating the plurality of the tubular structures 5602 to operate as one unit in terms of receiving and / or releasing of compressed gas.

[0700] Referring now to Figure 57H, showing a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention. In some embodiments, the energy storage device 5700 comprises an air flow pipe 5616 which branches into a plurality of pipes 5614 that directly communicate with the plurality of the tubular structures 5602, thereby facilitating the plurality of the tubular structures 5602 to operate as one unit in terms of receiving and / or releasing of compressed gas.

[0701] Exemplary energy storage device

[0702]

[0703] means

[0704] Referring now to Figure 58, showing a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention. In some embodiments, an energy storage device 5800 comprises the plurality of the tubular structures 5602.

[0705] In some embodiments, at least two of the plurality of the tubular structures 5602 is directly connected to the one or more air pipes 202. In some embodiments, at least two of the plurality of the tubular structures 5602 which are directly connected to the one or more air pipes 202 are not adjacent to each other but are instead separated by at least one tubular structure 5602, potentially reducing localized pressure differences.

[0706] In some embodiments, the energy storage device 5800 comprises an upper banister 5802. In some embodiments, a space defined by the upper banister 5802 is configured for containing more of the one or more weights 1506. A potential advantage of the one or more weights 1506 contained in the space defined by the upper banister 5802 is anchoring the energy storage device 5800 to the seabed 250. In some embodiments, when anchored to the seabed 250, the plurality of tubular structures 5602 extend upwardly in a substantially vertical direction from the seabed.

[0707] In some embodiments, the energy storage device 5800 comprises a lower banister 5804, positioned on the platform 5610. In some embodiments, the lower banister 5804 allows for water exchange with the surrounding environment via a water pipe 5806, which protrudes from the lower banister 5804.

[0708] Referring now to Figure 59A-B, showing a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention. Insome embodiments, an energy storage device 5900 comprises a cluster of inter-connected tubular structures 5902. In some embodiments, the cluster of inter-connected tubular structures 5902 is configured to allow to operate as one unit in terms of receiving and / or releasing of compressed gas, as will be further explained in relation to Figure 59D. In some embodiments, the cluster of interconnected tubular structures 5902 is connected to the one or more air pipes 202.

[0709] In some embodiments, the cluster of inter-connected tubular structures 5902 is mounted on a surface 5904. In some embodiments, the tubular structures 5602 within the cluster 5902 extend substantially vertically from the surface 5904. In some embodiments, the surface 5904 comprises metal beams. In some embodiments, the cluster of inter-connected tubular structures 5902 is attached to the surface 5904, for example by welding or by attaching with screws.

[0710] In some embodiments, one or more columns 5906 surround the cluster of inter-connected tubular structures 5902. In some embodiments, the one or more columns 5906 are configured to guide one or more weights, for example as shown in figure 59C. A potential advantage of one or more columns 5906 surrounding the cluster of inter-connected tubular structures 5902 is keeping the cluster of inter-connected tubular structures 5902 in place.

[0711] Referring now to Figure 59C, showing a schematic representation of a cluster of interconnected tubular structures, according to some embodiments of the invention. In some embodiments, an upper banister 5908 is positioned on the cluster of inter-connected tubular structures 5902. In some embodiments, weights (not shown in figure 59C) are distributed in the space defined by the upper banister 5908.

[0712] In some embodiments, one or more stackable weights 5910 are positioned on the surface 5904.

[0713] In some embodiments, the one or more stackable weights 5910 are guided by the one or more columns 5906, which can have different lengths, for example, a stackable weight from the one or more stackable weights 5910 is placed on a taller column from the one or more columns 5906, before being guided onto a shorter column from the one or more columns 5906. A potential advantage is reducing the need for precise simultaneous alignment of the weight with multiple columns, thereby preventing potential misalignment or jamming.

[0714] Referring now to Figure 59D, showing a schematic representation of a cluster of interconnected tubular structures, according to some embodiments of the invention. In some embodiments, the cluster of inter-connected tubular structures 5902, shown in figure 59D from above, comprises a plurality of the tubular structures 5602. In some embodiment, each of the plurality of the tubular structures 5602 is covered by a dome shaped cover 5908 which seals each of the plurality of the tubular structures 5602. In some embodiments, each of the plurality of the tubular structures 5602 is fluidlyconnected to another tubular structure 5602 from the plurality of the tubular structure 5602, for example as shown in Figures 57F and 57G.

[0715] Exemplary energy storage device

[0716]

[0717] of clusters of tubular structures Referring now to Figure 60, showing a schematic representation of an energy storage device comprising a plurality of clusters of inter-connected tubular structures, according to some embodiments of the invention. In some embodiments, an energy storage device 6000 comprises a plurality of clusters of inter-connected tubular structures 5902. In some embodiments, each cluster comprises a plurality of vertically extending tubular structures configured to operate as one unit. In some embodiments, each of the plurality of clusters of inter-connected tubular structures 5902 is connected to local gas pipe 6002, which receives and provides gas to and from the cluster of interconnected tubular structures 5902. In some embodiments, each local gas pipe 6002 connects to a main gas pipe 6004, which communicates the plurality of clusters of inter-connected tubular structures 5902 to a turbomachinery unit (not shown in figure 60).

[0718] Exemplary energy storage device

[0719]

[0720] tubular structure.

[0721] Referring now to Figure 61, showing a schematic representation of an energy storage device comprising a horizontally positioned tubular structure, according to some embodiments of the invention. In some embodiments, an energy storage device 6100 comprises the tubular structure 5602 positioned in a generally horizontal alignment relative to the seabed 250. Potential advantages of the tubular structure 5602 positioned in a generally horizontal alignment relative to the seabed 250 are the following:

[0722] • improved stability of the energy storage device 6100 due to low center of gravity, reducing susceptibility to displacement by underwater currents;

[0723] • enhanced load distribution, as the energy storage device 6100 footprint minimizes localized stress on the seabed;

[0724] • increased gas storage capacity, as the tubular structure 5602 can be designed with a greater length, facilitating high-volume gas storage;

[0725] • suitability for energy storage in shallow water reservoirs, where vertical configurations may be impractical due to depth constraints; and

[0726] • lower setup costs, as horizontal placement simplifies installation, anchoring, and maintenance.

[0727] In some embodiments, the tubular structure 5602 has a length 6102. In some embodiments, the length 6102 is from about 10 meters to about 100 meters, optionally from about 200 meters to about 1000 meters, optionally above 1000 meters.In some embodiments the tubular structure 5602 is equipped with two covers 6104A and 6104B for enclosing the tubular structure 5602.

[0728] In some embodiments, the one or more air openings 206 are positioned in a top part of the tubular structure 5602 for allowing gas release from the tubular structure 5602 and / or gas insertion to the tubular structure 5602.

[0729] In some embodiments, the tubular structure 5602 stores gas having a volume defined by a water level 6206 in the tubular structure 5602. In some embodiments, in a steady- state condition, the tubular structure 5602 comprises compressed gas and water therein, wherein the water occupies a lower portion of the tubular structure 5602 and the compressed gas occupies a volume above the water level 6206, thereby defining an interface between the compressed gas and the water within the tubular structure 5602. In some embodiments, during an energy storage phase, compressed gas is introduced into the tubular structure 5602, causing at least a portion of the water to exit the tubular structure 5602, for example through the one or more water openings 204 and / or via the water exchange pipe 6108. In some embodiments, during an energy release phase, at least a portion of the compressed gas is withdrawn from the tubular structure 5602, for example toward the turbomachinery unit, thereby allowing water to enter into the tubular structure 5602, wherein the tubular structure 5602 is anchored to the seabed 250 or otherwise secured in position such that the tubular structure 5602 remains substantially fixed while water enters and exits during operation of the energy storage device 6100. In some embodiments, the compressed gas and the water within the tubular structure 5602 are in thermal communication at the interface defined by the water level 6206. Thermal energy is transferred across the interface in accordance with the temperature gradient between the compressed gas and the water. When the compressed gas is at a higher temperature, thermal energy is transferred from the compressed gas to the water, and when the water is at a higher temperature, thermal energy is transferred from the water to the compressed gas. In some embodiments, the temperature of the water within the tubular structure 5602 is influenced by surrounding seawater through the walls of the tubular structure 5602 and / or through the one or more water openings 204, such that the water may function as a heat sink or as a heat source (i.e., absorbing thermal energy from the compressed gas when at a lower temperature, or transferring thermal energy to the compressed gas when at a higher temperature) during operation of the energy storage device 6100. In some embodiments, heat transfer between the compressed gas and the water occurs during both the energy storage phase and the energy release phase. Additionally, movement of the compressed gas into and / or out of the tubular structure 5602 and / or movement of water into and / or out of the tubular structure 5602 during operation further contribute to thermal exchange.In some embodiments, a water exchange pipe 6108 facilitates the controlled insertion and removal of water within the energy storage device 6100. In some embodiments, the water exchange pipe 6108 comprises an internal portion 6108A, which extends into the tubular structure 5602, and an external portion 6108B, which exits the tubular structure 5602 to connect with an external water source the energy storage device 6100 is positioned in. The internal portion 6108A is positioned to allow efficient water inflow and outflow to and from the energy storage device 6100. A potential advantage of water exchange pipe 6108 is preventing the one or more water openings 204 from being clogged, for example due to mud sedimentation.

[0730] In some embodiments, the tubular structure 5602 is anchored to the seabed 250 by one or more anchoring means (not shown in Figure 61), for example the anchoring means are foundations and / or weights.

[0731] In some embodiments, the energy storage device 6100 is positioned in an artificial water reservoir, for example a lake.

[0732] In some embodiments, preparatory groundwork is performed before flooding the artificial water reservoir, to enhance the stability of the energy storage device 6100. In some embodiments, foundations are constructed within the ground to secure the tubular structure 5602, optionally shaped in a manner that enhances stability.

[0733] Alternatively or additionally, support platforms are constructed above the tubular structure 5602, optionally equipped with banisters, over which soil, rocks, or other stabilizing materials is deposited.

[0734] Exemplary energy storage device comprising a cluster of horizontally positioned tubular structures

[0735] Exemplary energy storage device comprising a cluster of generally parallel horizontally positioned tubular structures

[0736] Referring now to Figures 62A-B, showing a schematic representation of an energy storage device comprising a cluster of generally parallel horizontally positioned tubular structures, according to some embodiments of the invention. In some embodiments, an energy storage device 6200 comprises a cluster of the tubular structure 5602. In some embodiments, the cluster of the tubular structure 5602are arranged such that the horizontally positioned tubular structures 5602 are generally parallel to one another.

[0737] In some embodiments, a plurality of connectors 6202 inter-connect the tubular structures 5602 in the cluster of tubular structures 5602. In some embodiments, the plurality of connectors 6202 allow transfer of water and gas between the cluster of tubular structure 5602, such that the cluster of tubular structure 5602 operate as one unit in terms of receiving and / or releasing of compressed gas.device a cluster of stacked

[0738] tubular structures

[0739] Referring now to Figures 63A-B, showing a schematic representation of an energy storage device comprising a cluster of stacked horizontally positioned tubular structures, according to some embodiments of the invention. In some embodiments, an energy storage device 6300 comprises a cluster of the tubular structure 56O2.In some embodiments, the cluster of the tubular structure 5602 are arranged such that the horizontally positioned tubular structures 5602 are in a generally stack formation. In some embodiments, only the tubular structures 5602 positioned at the bottom of the stack of the cluster of the tubular structures 5602 include the one or more water openings 204, allowing water to enter or exit the energy storage device 6300. In some embodiments, water can then flow to the upper tubular structures 5602 via the plurality of connectors 6202. In some embodiments, the one or more water openings 204 are connected to water pipes (not shown in Figure 63A-B).

[0740] Exemplary Configurations for Connecting Storage Tanks to a Main Gas Pipe

[0741] connections between a tank and a main

[0742] Referring now to Figure 64, showing a schematic representation of an energy storage device comprising a storage tank and one or more internal gas pipes, according to some embodiments of the invention.

[0743] The present inventors have found that connecting a storage tank 6402 or a plurality of storage tanks 6402 to a main gas pipe 6404 via one or more vertically oriented internal gas pipes 6406 provides a simple and cost-effective construction method while enabling efficient gas flow into and from the storage tank 6402. In some embodiments, the storage tank 6402 is configured for storing compressed gas in a gas volume located above a water level within the storage tank 6402. In some embodiments, the storage tank 6402 comprises one or more water openings 6408 positioned at a bottom part of the storage tank 6402 and configured to allow water from the surrounding environment to enter the storage tank 6402 as compressed gas is released, and to exit the storage tank 6402 as compressed gas is introduced, thereby maintaining internal pressure balance.

[0744] A potential advantage of connecting the storage tank 6402 or a plurality of storage tanks 6402 to a main gas pipe 6404 via one or more vertically oriented internal gas pipes 6406 is avoiding complex fabrication processes, such as creating wall penetrations or welding fittings between adjacent storage tanks, thereby reducing structural complexity and enabling rapid modular assembly.

[0745] In some embodiments, the one or more vertically oriented internal gas pipes 6406 are made of for example, metal, polymer or a combination thereof.

[0746] In some embodiments, an energy storage device 6400 comprises the storage tank 6402. In some embodiments, the storage tank 6404 houses one or more vertically oriented internal gas pipes6406, which are fluidly connected to the main gas pipe 6402. The main gas pipe 6404 is configured to supply and receive compressed gas, and is therefore connected at a first end 6410A to a gas compressor (not shown in Figure 64) and at a second end 6410B to a turbomachinery unit configured for energy extraction (not shown in Figure 64).

[0747] In some embodiments, each of the one or more vertically oriented gas pipes 6406 extend from the main gas pipe 6402 into the interior of the storage tank 6402 and terminate at an upper opening 6406A, located within the storage tank 6402.

[0748] In some embodiments, the upper opening 6406A is equipped with a valve 6412, configured to permit gas flow into and from the storage tank 6402 while preventing water from entering the one or more vertically oriented gas pipes 6406.

[0749] when compressed gas is supplied into the main gas pipe 6402, the compressed gas flows through the one or more vertically oriented gas pipes 6406 and enters the interior of the storage tank 6402 via the upper opening 6406A.

[0750] As compressed gas accumulates in the upper portion of the storage tank 6402, water is displaced and exits the storage tank 6402 through the one or more water openings 6408.

[0751] When energy extraction is desired, for example in response to a demand signal from a control system, a downstream valve (not shown in Figure 64) is opened, causing a drop in pressure in the main gas pipe 6404. The pressure differential between the compressed gas stored in the storage tank 6402 and the main gas pipe 6404 causes the compressed gas to flow from the storage tank 6402, optionally through the valve 6412 at the upper opening 6406A, and into the gas pipe 6406. As gas exits the storage tank 6402, the resulting decrease in internal pressure in the storage tank 6402 causes water from the surrounding environment to enter the storage tank 6402 via the water openings 6408. Exemplary connections between a plurality of storage tanks and a main gas pipe Referring now to Figure 65, showing a schematic representation of an energy storage device comprising a plurality of storage tanks housing one or more internal gas pipes, according to some embodiments of the invention. In some embodiments, an energy storage device 6500 comprises a plurality of the energy storage devices 6400, each including the storage tank 6402 fluidly connected to the main gas pipe 6404 via the vertically oriented internal gas pipe 6406.

[0752] In some embodiments, the plurality of energy storage devices 6400 operates as one unit for purposes of receiving and releasing compressed gas, in which the plurality of energy storage devices 6400 is fluidly connected to the main gas pipe 6404 via a shared valve (not shown in Figure 65), the valve configured to control the flow of compressed gas between the plurality of energy storage devices 6400 and the main gas pipe 6404. Alternatively, in some embodiments, each of the energy storagedevices 6400 is equipped with an individual valve (not shown in Figure 65), allowing selective charging or discharging of an energy storage device from the plurality of energy storage devices 6400.

[0753] Optionally, the energy storage device 6500 is equipped with a water removal unit 6502 fluidly connected to the main gas pipe 6404. In some embodiments, the water removal unit 6502 is configured to remove water that accumulate within the main gas pipe 6404 during operation.

[0754] In some embodiments, the water removal unit 6502 comprises a pump, a valve, or a combination thereof, configured to discharge water from the main gas pipe 6404 to the surrounding environment.

[0755] In operation, in the case that water obstructs the flow of compressed gas within the main gas pipe 6404, the water removal unit 6502 is activated to expel the water.

[0756] Referring now to Figure 66, showing a schematic representation of an energy storage device comprising a plurality of interconnected storage tanks, according to some embodiments of the invention. In some embodiments, an energy storage device 6600 comprises a plurality of the storage tank 6402 which operates as one unit for purposes of receiving and releasing compressed gas.

[0757] In some embodiments, at least one storage tank from the plurality of storage tanks 6402 is fluidly connected to the main gas pipe 6404 via the one or more vertically oriented internal gas pipes 6406. In some embodiments, the remaining storage tanks 6402 are fluidly interconnected with one another via one or more tubes 6602 which allow gas flow between storage tanks 6402, optionally storage tanks 6402 which are adjacent to one another. A potential advantage of the one or more tubes 6602 interconnecting the storage tanks 6402 is enabling a cost-efficient manufacturing of the energy storage device 6600.

[0758] In some embodiments, each of the one or more tubes 6602 comprises two openings, in which each opening is positioned within a respective storage tank 6402. In some embodiments, each opening is equipped with the valve 6412 configured to prevent water from the storage tank 6402 from entering the tube 6602.

[0759] In some embodiments, the one or more tubes 6602 has a shape, for example a U shape, in which one “leg” of the tube 6602 is positioned within a first storage tank from the plurality of storage tanks 6402 and the other “leg” is positioned within a second storage tank from the plurality of storage tanks 6402. A potential advantage of the one or more tubes 6602 having a U- shape which avoids sharp angles, is reducing mechanical stress concentrations and improving structural robustness, thereby minimizing the risk of fatigue or cracking over time.lt is known that maintaining the one or more tubes 6602 substantially filled with compressed gas is critical for proper performance of the energy storage device 6600.In some embodiments, at least one of the one or more tubes 6602 comprises a water removal unit 6604 positioned at a lower portion of the tube 6602. In some embodiments, the water removal unit 6604 comprises a pump, a valve, or a combination thereof, configured to remove water accumulated within the tube 6602 during operation.

[0760] work extraction from underwater

[0761]

[0762] In some embodiments, the underwater compressed gas storage tanks described herein are configured to operate in conjunction with any suitable system for storing energy and extracting work from compressed gas. The storage tanks may function as a gas reservoir configured to receive compressed gas during a charging phase and / or to supply compressed gas during a discharging phase. In some embodiments, compressed gas is generated by one or more compressors powered by grid electricity, renewable energy sources (such as wind turbines, photovoltaic systems, tidal generators, or wave energy converters), or conventional power plants operating during off-peak demand periods. During discharge, the stored compressed gas may be directed to one or more expansion devices, such as expanders, turbines, turbomachinery units, or combined compressor-expander assemblies, configured to convert the stored pressure energy into mechanical work and / or electrical energy.

[0763] In some embodiments, the one or more storage tanks of the underwater energy storage system described herein, are configured to store compressed gas for use in extracting work, for example, as part of a compressed gas energy storage (CGES) system, for example, similar to and / or as described in U.S. Provisional Patent Application 63 / 873,605 filed on August 31, 2025, and / or in the PCT application, “WORK EXTRACTION FROM UNDERWATER COMPRESSED GAS ENERGY STORAGE SYSTEM”, Docket No. 106535, filed on the same date as this disclosure, by the same applicant. The contents of the above applications are all incorporated by reference as if fully set forth herein in their entirety. In some embodiments, compressed gas energy storage (CGES) systems are designed to efficiently store and generate energy. As used herein, the term “gas” means any type of gas or combination of gases, for example, air and / or CO2. In this system, gas is compressed and stored underwater, taking advantage of the natural pressure in a sea or water body. When energy is needed, the stored compressed gas is released and allowed to expand through a Work-Extracting Gas Expander (WEGE) (such as a turbine and / or turboexpander), converting the energy from the compressed gas into mechanical work, which can then be used to generate electricity.

[0764] The efficiency of the energy production process is calculated by comparing the energy produced by the WEGE to the energy invested in both the compression and energy production processes. This includes all the energy required to compress the gas, as well as any additional energy needed for heating, cooling and / or other processes involved in compressing the gas, releasing the gas and allowing the gas to expand and drive a plurality of blades in the WEGE.for the in an underwater tank, and extracting work from the compressed gas

[0765] Referring now to Figure 67 A, showing a simplified block diagram of an exemplary system for storing energy and extracting work from a compressed gas energy storage system 6701, according to some embodiments of the invention. In some embodiments, system 6701 uses energy to compress gas, the compressed gas is then stored, and upon demand, the compressed gas is released to generate energy. In some embodiments, the system 6701 compresses and stores the gas during periods of energy surplus and generates energy from the compressed gas during periods of energy shortage.

[0766] The system 6701 comprises one or more gas compressors 6712, which use energy to increase the pressure of the gas, resulting in compressed gas. (In some embodiments, one or more gas compressors 6712 correspond to compressor 3512 and / or the compressor of turbomachinery unit 208).

[0767] During the compression of the gas in the one or more gas compressors 6712, heat is generated, and the temperature of the gas increases.

[0768] In some embodiments, the heat generated during the compression is transferred to a Thermal Energy Storage 6709 (TES), which stores the heat and optionally isolates the heat from the surrounding environment. A potential advantage of transferring heat from the compressed gas is reducing and / or preventing temperature increase of the one or more gas compressors 6712, thereby allowing the use of more cost-efficient materials that are optimized for lower temperature operation.

[0769] While in some embodiments, the TES 6709 has one chamber for storing heat at a single temperature, in some embodiments, the TES 6709 is a multi-chambers assembly for storing heat at different temperatures.

[0770] In some embodiments, the compressed gas is stored in a compressed gas storage unit 6700 (e.g., comprises and / or is defined by one or more storage tanks 100). In some embodiments, the compressed gas storage unit 6700 is positioned in an underwater location for counterbalancing the pressure of the compressed gas by the natural hydrostatic pressure provided by the water body. In some embodiments, the compressed gas storage unit 6700 is a tank which includes at least one water opening positioned in a lower portion of the tank, allowing water from the water body to flow into and out of the tank, for example, as described herein.

[0771] In some embodiments, the compressed gas storage unit 6700 is a closed tank.

[0772] In some embodiments, a Work-Extracting Gas Expander (WEGE) 6713 converts the energy stored in the compressed gas to mechanical work. In some embodiments, WEGE 6713 corresponds to the expander of turbomachinery unit 208 described herein). In some embodiments, upon demand, the compressed air is released from the compressed gas storage unit 6700 and allowed to enter the WEGE 6713 and expand. In some embodiments, the WEGE 6713 is a turbine engine generator (TEG)comprising a plurality of blades in which the expansion of the compressed gas generates a high-velocity flow that drives the blades, causing a shaft to rotate. The shaft is mechanically coupled to a generator, which converts the rotational mechanical energy into electrical energy. In some embodiments, the WEGE 6713 is a pneumatic engine based on alternative gas expansion mechanisms, for example, a rotary vane motor, a piston-cylinder system, or a screw expander. These configurations also utilize gas expansion to extract mechanical work.

[0773] During the expansion of the compressed gas in the WEGE 6713, the temperature of the gas decreases. In some embodiments, it is desirable to heat the compressed gas just before it enters the WEGE 6713, thereby controlling the temperature of the gas after expansion. For example, by preheating the compressed gas, the temperature at the WEGE 6713 outlet is maintained at or above a target temperature, for example, 0.5 °C, thereby potentially reducing and / or optionally preventing freezing of water vapor present in the compressed gas. Potential advantages of pre-heating the compressed gas before entering the WEGE 6713 are allowing effective work extraction by increasing the enthalpy of the compressed gas prior to expansion, and / or reducing and / or preventing ice formation that could damage system components.

[0774] In some embodiments, the compressed gas flows from the compressed gas storage unit 6700 to the WEGE 6713 via a connector 6704. In some embodiments, within the connector 6704, the compressed gas is heated prior to entering the WEGE 6713.

[0775] In some embodiments, the compressed gas is heated by absorbing heat from multiple heat sources.

[0776] Optionally, in a first heating stage, heat is transferred to the compressed gas using external heat 6711, for example, heat from the environment and / or any other heat source that is not derived from the compressed gas (e.g., not derived from heat generated during compression of the gas), for example, heat from industrial processes and / or geothermal activity, and / or heat from the surrounding waterbody. A potential advantage of using external heat 6711 for heating the compressed gas is increasing the RTE of the work extraction process by using available, low-cost energy.

[0777] In some embodiments, alternatively or additionally, optionally in a second heating stage, heat is transferred from the TES 6709. A potential advantage of using heat from the TES 6709 to heat the compressed gas is increasing the RTE of the work extraction process by using the heat emitted during compression to heat the compressed gas.

[0778] In some embodiments, the expansion process in the WEGE 6713 is a single-stage expansion process, and heat from the TES 6709 and / or from external heat 6711 is transferred to (and / or introduced into) the compressed gas prior to entry of the compressed gas into the WEGE 6713. In some embodiments, the expansion process in the WEGE 6713 comprises more than one expansionstage, and heat from the TES 6709 and / or from external heat 6711 is transferred to (and / or introduced into) the compressed gas prior to a first expansion stage and / or prior to at least one of the expansion stages, and optionally prior to each of the plurality of expansion stages, for example via one or more heat exchangers positioned along the flow path.

[0779] In some embodiments, system 6701 comprises (and / or is partitioned into) two subsystems, including a compression subsystem and a generation subsystem. In some embodiments, the compression subsystem is configured to compress the gas, to communicate the gas (e.g., in a compressed state), to compressed gas storage unit 6700, and / or to harvest heat from the gas after compression.

[0780] In some embodiments, the generation subsystem is configured to extract work from the gas. Upon demand, the compressed gas storage unit 6700 releases the gas to the generation subsystem, and / or to transfer heat to the gas (e.g., heat from the TES 6709 and / or from external heat 6711).

[0781] In some embodiments, system 6701 comprises one or more heat exchangers positioned and / or configured to transfer heat from the gas exiting the one or more compressors 6712 to the TES 6709, and to transfer heat from the TES 6709 and / or from external heat 6711 to the compressed gas prior to entry of the compressed gas into the WEGE 6713 (e.g., a turboexpander). As used herein, “heat transfer” may comprise circulating a thermal medium (e.g., water, oil, glycol, molten salt, or any other heat transfer fluid) that absorbs heat from a heat source and / or delivers heat to the compressed gas via indirect heat exchanges. A potential advantage of using external heat 6711 for heating the compressed gas includes utilizing readily available and / or low-cost thermal energy sources, optionally that would otherwise be wasted. In some embodiments, the external heat source comprises industrial waste heat generated by high-temperature processes, including but not limited to steel manufacturing plants, glass production facilities, ceramic kilns, and / or cement plants.

[0782] Referring now to Figure 67B, showing a schematic representation of an exemplary system 6701b for compressing gas, storing the compressed gas in an underwater storage tank, extracting work from the compressed gas, and storing heat generated from gas compression according to some embodiments of the invention. In some embodiments, a system 6701b comprises an electrical connection 6702, which provides a connection to an electrical power grid 6704. In some embodiments, the electrical power grid 6704 supplies electrical power during energy surplus. In some embodiments, a compressor assembly 6712 is configured to receive electrical power from the electrical connection 6702 and to compress gas. In some embodiments, the compressor assembly 6712 optionally, comprises a plurality of compressors which compress the gas in a multi-stage compression.Optionally, in some embodiments, the system which potentially facilitates the process, operates as a temporary energy storage buffer for continuous but relatively inflexible energy sources, such as nuclear reactors. For example, the system is positioned and configured such that it can receive unused heat and / or excess electrical energy generated by the nuclear reactor during periods of low demand (e.g., at night) and store that energy. During periods of increased demand, the system supplies stored energy to the electrical grid, thereby complementing the reactor’s output and bridging the temporal gap between energy production and energy demand. A potential benefit of pairing such an energy storage system with a nuclear reactor and / or coal power station is that such stations often have a slow response to a sudden increase (and / or decrease) in demand. Responding to such a sudden increase with additional electrical power is optionally provided by an energy storage system as described herein. It is noted that the use of waste heat from a nuclear reactor effectively increases the RTE of such a storage system as compared to other energy storage systems, such as gravity-based systems. Charging of the storage system may be, for example, from the nuclear reactor output as it is being ramped down due to a reduction in need. Such charging can also be used to bleed excess electrical power from a grid or from entering a grid. Similarly, power from an air-based storage system may be used to provide power to a steel plant. Energy may be stored, for example, during off-peak hours and used for peak demand and / or if there are electrical supply problems.

[0783] When there is a need for energy, a turboexpander 6713 is configured to receive compressed gas and allow the gas to expand, converting pressure energy into work. In some embodiments, the turboexpander 6713 optionally comprises a plurality of turboexpander which allow the gas to expand in a multi-stage.

[0784] In some embodiments, after compression, the compressed gas flows through a one or more gas pipes 6710 to one or more underwater storage tanks 6700 located below sea level 6714 and on the seabed 6715. In some embodiments, one or more underwater storage tanks 6700 are open to ambient water at their lower portion such that the ambient water exerts hydrostatic pressure on the pressure gas, such that the one or more underwater storage tanks 6700 are configured for withstanding lower pressures compared to closed tanks for storing compressed gas on land, for example, as described herein. In some embodiments, the one or more underwater storage tanks 6700 are positioned at a depth of, for example, from 90 meters to 200 meters, optionally from 200 meters to 600 meters, optionally from 600 meters to 1500 meters or more.

[0785] In some embodiments, the one or more underwater storage tanks 6700 comprise a plurality of separate tanks, which are fluidly connected to one another to allow water and / or gas flow between the plurality of separate tanks, and, in some embodiments, the one or more underwater storage tanks 6700 are one or more clusters of tubular structures, for example as shown in figure 67B.In some embodiments, the system comprises a dedicated system to store hot water and a dedicated system to store cold water. In some embodiments, the systems are separated. A potential advantage of having two separate systems is that it allows using a lower number of specialized containers for hot water and using cheap, unspecialized means to store the cold water.

[0786] In some embodiments, the system 6701b further comprises a compression heat exchanger 6716 arranged downstream of the compressor assembly 6712. The compression heat exchanger 6716 transfers heat from the compressed gas to a thermal storage liquid, which circulates through one or more conduits 6718. The heated thermal storage liquid is thereby stored in a hot storage tank 6720 in the TES (it should be noted that storage of cold water is done in a separate system and / or storage tanks). In some embodiments, the TES comprises one or more tanks for storing the thermal storage liquid. In some embodiments, the one or more tanks comprise a layer of compressed gas maintained above the heated thermal storage liquid, in which the pressure of the compressed gas is greater than the vapor pressure of the heated thermal storage liquid at the storage temperature, such that the thermal storage liquid does not boil.

[0787] In some embodiments, when there is a need for energy, compressed gas flows from the one or more underwater storage tanks 6700 through the one or more gas pipes 6710 to a pre-expansion heat exchanger 6722. The pre-expansion heat exchanger 6722 transfers heat to the compressed gas from the hot thermal storage liquid drawn from the hot storage tank 6720 of the TES (e.g., TES 6709), potentially increasing the RTE of the work extraction process. The compressed gas is then allowed to expand in the turboexpander 6713, which, in some embodiments, is used to generate electricity which supplied to the electrical power grid 6704. After the thermal storage liquid has transferred heat, the cooled thermal storage liquid is returned via the one or more conduits 6718 to the cold storage tank 6742.

[0788] In some embodiments, when the compressor assembly 6713 compresses gas, the cooled thermal storage liquid in the cold storage tank 6742 is circulated back through the compression heat exchanger 6716 to absorb heat and is circulated to the hot storage tank 6720 of the TES.

[0789] In some embodiments, the system 6701b further comprises a controller 6726, which potentially controls, all the elements of the system (valves, pumps, compressor, etc.), for example, valves 6728A and 6728B via communication cable 6730.

[0790] In some embodiments, controller 6726 is configured to control the release of compressed gas from the one or more underwater storage tanks 6712 into the turboexpander 6713, and the reception and storage of compressed gas generated by the compressor assembly 6712.

[0791] In some embodiments, when it is desired to store energy, for example, when a surplus of electricity is available on the power grid 6704, the controller 6726 instructs valve 6728A to open,thereby allowing the compressor assembly 6713 to receive electrical power from the grid 6704 via electrical connection 6702, and compress gas. Conversely, in some embodiments, when it is desired to produce electricity, for example, during periods of increased energy demand, the controller 6726 commands valve 6728B to open, releasing compressed gas from the one or more underwater storage tanks 6700 through the heat exchanger 6708 and into the turboexpander 6713, generating electricity, for example the electricity is supplied to the power grid 6704, or to a user.

[0792] In some embodiments, only the one or more underwater storage tanks 6700 are positioned underwater 6714, while the remainder of the system 6701b is located on land, or alternatively or additionally on a floating barge above the sea. As used herein, the term “land” means an offshore platform, for example, a converted drilling rig.

[0793] Referring now to Figure 67C, showing a schematic representation of an exemplary system for compressing gas, storing the compressed gas in an underwater storage tank, and extracting work from the compressed gas, according to some embodiments of the invention. In some embodiments, a system 6701c comprises compressors 6712A-C. In some embodiments, when it is desired to store energy, for example, when there is an electricity surplus, electricity is supplied to each of the compressors 6712A-C via the electrical connection 6702 such that the compressors 6712A-C compresses gas, and a corresponding heat exchanger 6716A-C transfer heat to the TES by thermal storage liquid which is circulated in the one or more conduits 6718.

[0794] In some embodiments, the system 6701c expands the compressed gas in a multi stage expansion via the turboexpanders 6713A-C. In some embodiments, when it is desired to produce electricity from the compressed gas, compressed gas is heated before it is allowed to expand in each of the turboexpanders 6713A-C by absorbing heat from the hot thermal storage liquid via a corresponding heat exchanger 6717A-C. The turboexpanders 6713A-C generate electricity, which is transferred via an electrical connection 6740, optionally to an energy storage unit.

[0795] In some embodiments, the thermal storage liquid, having been cooled, is then circulated to the cold storage tank (not shown in Figure 67C, a general square showing storage tanks is shown), where it is stored.

[0796] In some embodiments, the compressed gas after being compressed by the compressors 6712A-C is stored in a plurality of clusters of tubular structures, for example, as described herein.

[0797] Referring now to Figures 68A-C, showing a schematic representation of an exemplary storage tank system for storing compressed gas in an underwater location, according to some embodiments of the invention. In some embodiments, a system 6801 comprises one or more storage conduits 6800 configured to store compressed gas underwater. In some embodiments, one or more storage conduits6800 correspond to one or more underwater storage tanks 6700, or are an exemplary implementation thereof.

[0798] In some embodiments, the one or more storage conduits 6800 are positioned on a seabed 6815.

[0799] In some embodiments, one or more water openings 6806 are positioned at a distal and / or lower portion of the one or more storage conduits 6800, configured to allow water to enter and exit the one or more storage conduits 6800 as compressed gas is respectively introduced into or released from the one or more storage conduits 6800.

[0800] In some embod...

Claims

WHAT IS CLAIMED IS:

1. An underwater energy storage device comprising:a plurality of vertically extending tubular structures defining at least one internal lumen configured for storing compressed gasfor storing compressed gas;wherein said plurality of tubular structures are arranged in a clustered configuration, and are fluidly connected to one another,wherein at least one of the plurality of the tubular structures comprises one or more water openings, configured for one or both of: (a) water ingress; and (b) water egress.

2. The underwater energy storage device of claim 1, wherein each of the plurality of the tubular structures comprises the one or more water openings, or at least one of the tubular structures is sealed to the outside environment and does not comprise the one or more water openings.

3. The underwater energy storage device of any of claims 1-2, wherein the plurality of tubular structures operate as one unit in terms of one or both of receiving and releasing compressed gas.

4. The underwater energy storage device of any of claims 1-3, wherein the plurality of tubular structures are fluidly interconnected by a plurality of connectors.

5. The underwater energy storage device of claim 4, wherein said plurality of connectors are configured to transfer one or both of water and gas between the plurality of tubular structures.

6. The underwater energy storage device of any of claims 1-5, wherein the plurality of tubular structures are connected to one or more gas connectors configured to allow gas transfer between the plurality of tubular structures.

7. The underwater energy storage device of claim 6, wherein the plurality of connectors comprises one or more connectors at different heights.

8. The underwater energy storage device of any of claims 1-7, wherein the plurality of tubular structures is attached to one another.

9. The underwater energy storage device of any of claims 1-8, comprising a cement cast positioned between the plurality of the tubular structures.

10. The underwater energy storage device of any of claims 1-9, wherein at least one of the plurality of the tubular structures comprises one or more air openings, connected to one or more air pipes configured for communicating the plurality of tubular structures to a turbomachinery unit.

11. The underwater energy storage device of claim 10, wherein the at least two of the plurality of the tubular structures is directly connected to the one or more air pipes.

12. The underwater energy storage device of claim 11, wherein the at least two of the plurality of the tubular structures which are directly connected to the one or more air pipes are separated by at least one tubular structure.

13. The underwater energy storage device of any of claims 1-12, wherein at least one of said tubular structures is made of one or more of metal, cement, and polymer.

14. The underwater energy storage device of claim 1-13, comprising at least one weight.

15. The underwater energy storage device of claim 1-14, comprising more than one plurality of tubular structures arranged in a clustered configuration,wherein each of the more than one plurality of tubular structures arranged in a clustered configuration are connected to a local gas pipe configured to one or both of receive and provide gas to and from the more than one plurality of tubular structures arranged in a clustered configuration.

16. The underwater energy storage device of claim 15, wherein each local gas pipe is connects to a main gas pipe, wherein the main gas pipe is configured to communicates the more than one plurality of tubular structures arranged in a clustered configuration to a turbomachinery unit.

17. An underwater energy storage device comprising:at least one tubular structure positioned in a horizontal alignment relative to a seabed, and comprising one or more water openings, configured for one or both of: (a) water ingress; and (b) water egress,wherein the at least one tubular structure is configured to store compressed gas above a water level within the tubular structure.

18. The underwater energy storage device of claim 17, wherein the one or more water openings are positioned at a bottom part of the at least one tubular structure.

19. The underwater energy storage device of any of claims 17-18, comprising one or more air openings positioned in a top part of the tubular structure.

20. The underwater energy storage device of any of claims 17-19, comprising a water exchange pipe configured for controlled insertion and removal of water.

21. The underwater energy storage device of any of claims 17-20, wherein the at least one tubular structure is anchored to the seabed by one or more anchors.

22. The underwater energy storage device of any of claims 17-21, wherein the at least one tubular structure comprises an elongated polymer conduit.

23. The underwater energy storage device of any of claims 17-22, wherein the at least one tubular structure comprises a cluster of tubular structures positioned in a generally horizontal alignment relative to a seabed.

24. The underwater energy storage device of claim 23, wherein the tubular structures are arranged parallel to one another.

25. The underwater energy storage device of claim 23, wherein the tubular structures are arranged in a stacked formation.

26. An energy storage system, comprising:a. one or more compressors positioned above water and configured to compress gas;b. one or more underwater compressed gas storage devices positioned in a waterbody and configured to receive the compressed gas from the one or more compressors and store the compressed gas;c. one or more turboexpanders positioned above water and configured to receive compressed gas from the one or more underwater compressed gas storage devices and to extract mechanical work from expansion of the compressed gas;d. a thermal energy storage (TES) positioned and configured to store heat from the compressed gas generated during compression and to allow transfer of heat to the compressed gas prior to expansion in the one or more turboexpanders;e. one or more first heat exchangers positioned and configured to transfer heat from the compressed gas after compression to the TES;f. one or more second heat exchangers positioned and configured to transfer heat from the TES to the compressed gas before expansion in the one or more turboexpanders; andg. at least one external heat exchanger configured to transfer heat from an external heat source to the compressed gas before expansion in the one or more turboexpanders.

27. The energy storage system of claim 26, wherein at least one of the one or more underwater compressed gas storage devices is according to any of claims 1-16.

28. The energy storage system of any of claims 26-27, wherein at least one of the one or more underwater compressed gas storage devices is according to any of claims 17-25.

29. The energy storage system of any of claims 26-28, wherein the thermal energy storage (TES) comprises:a. one or more tanks configured to contain a thermal storage liquid at hot and cold temperatures; andb. a thermal cycling subsystem configured to selectively cycle the thermal storage liquid among the one or more tanks during a thermal cycling process,wherein during a thermal cycling process the thermal storage liquid is alternately heated and cooled, and wherein the same tanks are employed to contain either cold or hot thermal storage liquid.

30. An energy storage system, comprising:a. one or more compressors positioned above water and configured to compress gas; b. one or more underwater compressed gas storage devices positioned in a waterbody and configured to receive the compressed gas from the one or more compressors and store the compressed gas;c. one or more turboexpanders positioned above water and configured to receive compressed gas from the one or more underwater compressed gas storage devices and to extract mechanical work from expansion of the compressed gas;d. a thermal energy storage (TES) positioned above water and configured to store heat from the compressed gas generated during compression and to allow transfer of heat to the compressed gas prior to expansion in the one or more turboexpanders;e. one or more first heat exchangers positioned above water and configured to transfer heat from the compressed gas after compression to the TES;f. one or more second heat exchangers positioned above water and configured to transfer heat from the TES to the compressed gas before expansion in the one or more turboexpanders;wherein the TES comprises:i. one or more tanks configured to contain a thermal storage liquid at hot and cold temperatures; andii. a thermal cycling subsystem configured to selectively cycle the thermal storage liquid among the one or more tanks during a thermal cycling process,wherein during the thermal cycling process the thermal storage liquid is alternately heated and cooled, and wherein the same tanks are employed to contain either cold or hot thermal storage liquid.

31. The energy storage system of claim 30, wherein at least one of the one or more tanks is configured to withstand a pressure greater than the vapor pressure of the thermal storage liquid at an operating temperature, thereby preventing boiling and phase transition of the thermal storage liquid into vapor.

32. The energy storage system of any of claims 30-31, wherein at least one of the one or more underwater compressed gas storage devices is according to any of claims 1-16.

33. The energy storage system of any of claims 30-31, wherein at least one of the one or more underwater compressed gas storage devices is according to any of claims 17-25.

34. The energy storage system of any of claims 30-33, comprising at least one environmental heat exchanger configured to transfer heat from an environmental heat source to the compressed gas before expansion in the one or more turboexpanders.

35. An underwater energy storage device comprising:a. a metal storage tank having at least one wall and a roof comprising:i. one or more air openings for enabling flow of air into and from said metal storage tank;ii. one or more water openings for enabling flow of water into and from said metal storage tank; andb. one or more air pipes connected to said one or more air openings;said water openings are located at a bottom part of said at least one wall of said storage tank; and said one or more air openings are located at an upper part of said at least one wall of said metal storage tank and / or on said roof of said metal storage tank;wherein said underwater energy storage device further comprises linear structural reinforcing elements for reinforcing the metal storage tank to withstand a tensile force exerted on said metal storage tank.

36. The device according to claim 35, wherein said storage tank comprises a plurality of tubular structures, and wherein said plurality of tubular structures are interconnected for allowing gas exchange between said plurality of tubular structures.

37. A method for manufacturing an energy storage device, the method comprising: providing a plurality of industrial tubular structures configured for storing compressed gas; arranging said plurality of industrial tubular structures vertically extending in a clustered configuration;fluidly inter-connecting said industrial tubular structures to enable gas and / or water flow between said industrial tubular structures; andconnecting said cluster of said plurality of industrial tubular structures to a gas pipe for enabling flow of gas into and from said cluster of said plurality of industrial tubular structures.

38. An underwater energy storage system comprising:a. one or more storage tanks, each storage tank having at least one wall and a roof, each comprising:i. one or more air openings for enabling flow of air into and from the respective storage tank;ii. one or more water openings for enabling flow of water into and from the respective storage tank;b. a main gas pipe configured for supplying compressed air and / or exhausting compressed air;c. one or more internal air pipes positioned within the one or more storage tanks and fluidly connected to said main gas pipe via the one or more air openings; andwherein said one or more water openings are located at a bottom part of said at least one wall of each storage tank; andwherein said one or more internal air pipes enable compressed gas from the main gas pipe to flow into and / or out of the respective storage tanks.

39. The system of claim 38, wherein said one or more storage tanks comprises a plurality of storage tanks, and further comprising one or more interconnecting gas conduits fluidly connecting two or more of the plurality of storage tanks, wherein each interconnecting gas conduit comprises a first end positioned within a first storage tank and a second end positioned within a second storage tank, thereby enabling air flow between the first storage tank and the second storage tank.

40. An underwater energy storage device, comprising:a. one or more compressors positioned above water and configured to compress gas;b. one or more underwater compressed gas storage devices positioned in a waterbody and configured to receive the compressed gas from the one or more compressors and store the compressed gas;wherein the one or more underwater compressed gas storage devices comprises: a. a storage tank having at least one wall and a roof comprising:i. one or more air openings for enabling flow of air into and from said storage tank; ii. one or more water openings for enabling flow of water into and from said storage tank; andb. one or more air pipes connected to said one or more air openings;wherein said one or more air openings are located at an upper part of said at least one wall of said storage tank and / or on said roof of said storage tank.c. one or more turboexpanders positioned above water and configured to receive compressed gas from the one or more underwater compressed gas storage devices and to extract mechanical work from expansion of the compressed gas;d. a thermal energy storage (TES) positioned above water and configured to store heat from the compressed gas generated during compression and to allow transfer of heat to the compressed gas prior to expansion in the one or more turboexpanders;e. one or more first heat exchangers positioned above water and configured to transfer heat from the compressed gas after compression to the TES;f. one or more second heat exchangers positioned above water and configured to transfer heat from the TES to the compressed gas before expansion in the one or more turboexpanders; and g. at least one environmental heat exchanger configured to transfer heat from an environmental heat source to the compressed gas before expansion in the one or more turboexpanders.

41. An energy storage system, comprising:a. one or more compressors positioned above water and configured to compress gas;b. one or more underwater compressed gas storage devices positioned in a waterbody and configured to receive the compressed gas from the one or more compressors and store the compressed gas;wherein the one or more underwater compressed gas storage devices comprises: a. a storage tank having at least one wall and a roof comprising:i. one or more air openings for enabling flow of air into and from said storage tank; ii. one or more water openings for enabling flow of water into and from said storage tank; andb. one or more air pipes connected to said one or more air openings;wherein said one or more air openings are located at an upper part of said at least one wall of said storage tank and / or on said roof of said storage tank.c. one or more turboexpanders positioned above water and configured to receive compressed gas from the one or more underwater compressed gas storage devices and to extract mechanical work from expansion of the compressed gas;d. a thermal energy storage (TES) positioned above water and configured to store heat from the compressed gas generated during compression and to allow transfer of heat to the compressed gas prior to expansion in the one or more turboexpanders;e. one or more first heat exchangers positioned above water and configured to transfer heat from the compressed gas after compression to the TES;f. one or more second heat exchangers positioned above water and configured to transfer heat from the TES to the compressed gas before expansion in the one or more turboexpanders;wherein the TES comprises:i. one or more tanks configured to contain a thermal storage liquid at hot and cold temperatures; andii. a thermal cycling subsystem configured to selectively cycle the thermal storage liquid among the one or more tanks during a thermal cycling process,wherein during the thermal cycling process the thermal storage liquid is alternately heated and cooled, and wherein the same tanks are employed to contain either cold or hot thermal storage liquid.

42. The energy storage system of any of claims 40-41, wherein said water openings are located at a bottom part of said at least one wall of said storage tank.

43. The energy storage system of any of claims 40-42, wherein said underwater energy storage device further comprises peripheral edges located at a bottom part of said storage tank.

44. The energy storage system of any of claims 40-43, wherein said underwater energy storage device further comprises a floor.

45. The energy storage system of claim 44, wherein the storage tank comprises heights at a center of said floor are higher than heights extending from said center towards walls of said storage tank for encouraging sand removal.

46. The energy storage system of any of claims 40-45, wherein the storage tank comprises one or more arc shaped water openings.

47. The energy storage system of claim 46, wherein said one or more arc shaped water openings are located to be in contact with said floor configured for facilitating sand removal.

48. The energy storage system of claim 41, wherein the one or more tanks of the thermal energy storage (TES) are maintained at substantially the same pressure.

49. A method for storing and releasing energy using an underwater energy storage device comprising at least one tubular structure positioned in a waterbody, the method comprising:introducing compressed gas into the tubular structure during an energy storage phase; allowing at least a portion of water within the tubular structure to exit the tubular structure;storing the compressed gas within the tubular structure above a water level defined therein;withdrawing at least a portion of the compressed gas from the tubular structure during an energy release phase; andallowing water to enter into the tubular structure as the compressed gas is withdrawn, wherein the tubular structure is anchored to a seabed such that the tubular structure remains substantially fixed while water exits and enters during operation.

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