Work extraction from underwater compressed gas energy storage system

Abstract

The invention relates to an underwater energy storage system interconnected to a thermal storage system positioned on land. The invention also relates to an underwater energy storage system interconnected to a thermal storage system that harvest heat from self-generating sources and / or from external sources (like the environment, external factories, nuclear plants, etc.). The invention also relates to an underwater energy storage system interconnected to a thermal storage system that utilizes the same storage tanks for storing, at one time hot water, at another time cold water. In some embodiments, there is at least one storage tank that remains empty. The invention also relates to a thermal storage system that utilizes the same storage tanks for storing, at one time hot water, at another time cold water. In some embodiments, there is at least one storage tank that remains empty.

Description

[0001] WORK EXTRACTION FROM UNDERWATER COMPRESSED GAS ENERGY STORAGE SYSTEM RELATED APPLICATIONS

[0002] This application claims the benefit of priority of U.S. Provisional Patent Application Nos. 63 / 762,182 filed on February 24, 2025; 63 / 873,605 filed on August 31, 2025, and 63 / 907,962 filed on October 30, 2025, the contents of which are incorporated herein by reference in their entirety.

[0003] This application is part of a group of filings which include this PCT application, “WORK EXTRACTION FROM UNDERWATER COMPRESSED GAS ENERGY STORAGE SYSTEM”, Docket No. 106535, and the PCT application “STRUCTURES FOR UNDERWATER ENERGY STORAGE”, Docket No. 105992, filed on the same date by the same applicant.

[0004] The contents of the above applications are all incorporated by reference as if fully set forth herein in their entirety.

[0005] FIELD AND BACKGROUND OF THE INVENTION

[0006] The present invention, in some embodiments thereof, relates to compressing gas, storing the compressed gas and allowing the gas to expand for extracting work and, more particularly, but not exclusively, to compressing gas, storing the compressed gas, allowing the gas to expand for extracting work and further transferring heat from the compressed gas to improve the overall energetic cycle.

[0007] Additional background art includes U.S. Patent No. 4,873,828 disclosing a method and apparatus for storing excess electricity generated during off-peak periods. The electricity is used to run compressors which compress the air in a plurality of stages. The air is cooled after each stage to remove the heat of enthalpy. The air is stored in bags on the bottom of the sea. To recover the energy, the compressed air is run through turbines and the heat removed during compression is reintroduced;

[0008] U.S. patent No. 11,644,150 B2 disclosing a thermal storage subsystem may include at least a first storage reservoir configured to contain a thermal storage liquid at a storage pressure that is greater than atmospheric pressure. A liquid passage may have an inlet connectable to a thermal storage liquid source and configured to convey the thermal storage liquid to the liquid reservoir. A first heat exchanger may be provided in the liquid inlet passage and may be in fluid communication between the first compression stage and the accumulator, whereby thermal energy can be transferred from a compressed gas stream exiting a gas compressor / expander subsystem to the thermal storage liquid;

[0009] International Patent Application No. WO 2019 / 011593 Al disclosing a Compressed gas energy storage and energy recovery system comprising at least one means for compressing said gas, at least one storage means for said compressed gas, at least one expansion means of said gascompressed gas, at least one heat exchange means between said compressed gas and a heat transfer fluid, heat storage means, the heat exchange means being arranged at the outlet of the compression means of said gas and / or at the inlet of the expansion means of the gas, the heat exchange means comprises means for direct contact with the gas and the heat transfer fluid.

[0010] International Patent Application No. WO 2024 / 064155 Al disclosing a system for storing compressed gas that includes a surface structure, a gas storage assembly and a thermal storage assembly. The surface structure includes a compressor and expander assembly associated therewith. The gas storage assembly includes at least one gas receiver and is in fluid communication with the compressor and expander assembly. In use, the gas storage assembly is disposed in a body of water. The gas storage assembly is configured to move within the body of water from a first level to a second level when compressed gas is added to the gas storage assembly. The second level is deeper than the first level. The thermal storage assembly includes a tank containing water therein. The thermal storage assembly is in thermal communication with the compressor and expander assembly. The heat generated from the compression of the gas is transferred to the water in the tank in the thermal storage assembly.

[0011] SUMMARY OF THE INVENTION

[0012] According to an aspect of some embodiments of the present invention there is provided method for operating a thermal energy storage (TES) system comprising one or more tanks, the method comprising: a. storing a thermal storage liquid in one or more tanks; and b. selectively cycling 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 used to contain either cold or hot thermal storage liquid.

[0013] According to some embodiments of the invention, the selectively cycling comprises transferring cold thermal storage liquid from at least one tank to a first heat exchanger for absorbing heat from compressed gas during gas compression.

[0014] According to some embodiments of the invention, the selectively cycling comprises transferring hot thermal storage liquid from at least one tank to a second heat exchanger for transferring heat to compressed gas prior to expansion in a turboexpander.

[0015] According to some embodiments of the invention, storing a thermal storage liquid comprising storing at a pressure greater than the vapor pressure of the thermal storage liquid at an operating temperature.

[0016] According to some embodiments of the invention, the storing comprising providing compressed gas above the thermal storage liquid to exert the pressure.According to some embodiments of the invention, storing the thermal storage liquid comprises maintaining at least one of the one or more tanks in an empty state.

[0017] According to some embodiments of the invention, the selectively cycling comprises coordinating the discharge of thermal storage liquid from one tank simultaneously with the filling of another tank with thermal storage liquid.

[0018] According to an aspect of some embodiments of the present invention there is provided an energy storage system comprising: a. one or more tanks configured to contain a thermal storage liquid at hot and cold temperatures; and b. 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.

[0019] According to some embodiments of the invention, the thermal storage liquid is water.

[0020] According to some embodiments of the invention, 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.

[0021] According to an aspect of some embodiments of the present invention there is provided 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; 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.

[0022] According to some embodiments of the invention, the at least one environmental heat exchanger is configured to transfer heat from the waterbody surrounding the underwater compressed gas storage devices.According to some embodiments of the invention, the at least one environmental heat exchanger is configured to transfer heat from an industrial heat source.

[0023] According to some embodiments of the invention, the at least one environmental heat exchanger is configured to transfer heat from a geothermal source.

[0024] According to some embodiments of the invention, the thermal energy storage (TES) comprises one or more tanks configured to contain a thermal storage liquid, the one or more tanks being selectively connected to the one or more first heat exchangers and / or the one or more second heat exchangers.

[0025] According to some embodiments of the invention, at least one of the one or more tanks is configured to store cold thermal storage liquid, and is configured to store hot thermal storage liquid.

[0026] According to some embodiments of the invention, at least one tank 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 for preventing boiling and phase transition of the hot thermal storage liquid into vapor.

[0027] According to some embodiments of the invention, further comprising a controller configured to selectively regulate operation of the one or more first heat exchangers, the one or more second heat exchangers, and the at least one environmental heat exchanger based on at least one of: temperature of the compressed gas, availability of environmental heat, and amount of heat stored in the TES.

[0028] According to some embodiments of the invention, the one or more turboexpanders comprise a plurality of turboexpanders arranged in series to facilitate multi-stage expansion of the compressed gas.

[0029] According to some embodiments of the invention, further comprising at least one intermediate heat exchanger positioned between two of the plurality of turboexpanders, the intermediate heat exchanger being configured to transfer heat from the TES and / or an environmental heat source to the compressed gas between expansion stages.

[0030] According to an aspect of some embodiments of the present invention there is provided an energy storage system, comprising: a. one or more underwater compressed gas storage tanks positioned at a depth in a waterbody and configured to store compressed gas; b. a thermal energy storage (TES) assembly positioned above water and comprising one or more tanks configured to contain thermal storage liquid in hot or cold states; d. at least one environmental heat exchanger positioned in the waterbody and configured to transfer heat from the waterbody to thermal storage liquid flowing through the one or more conduits; and e. a controller configured to determine heat requirements for heating the compressed gas prior to expansion based on a depth of the one or moreunderwater compressed gas storage tanks and to selectively control heat transfer from the TES assembly and / or via at least one environmental heat exchanger.

[0031] According to some embodiments of the invention, the controller is configured to calculate a temperature difference between (i) the temperature of the waterbody at the depth of the one or more underwater compressed gas storage tanks, and (ii) the temperature of the cold thermal storage liquid in the TES assembly.

[0032] According to some embodiments of the invention, the controller is configured to activate the at least one environmental heat exchanger to further cool the cold thermal storage liquid when the calculated temperature difference exceeds a predefined threshold.

[0033] According to some embodiments of the invention, the controller is configured to regulate operation of the at least one environmental heat exchanger to reduce the temperature of the thermal storage liquid to a level proximate to the temperature of the surrounding waterbody.

[0034] 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.

[0035] Example 1. A method for operating a thermal energy storage (TES) system comprising one or more tanks, the method comprising:

[0036] a. storing a thermal storage liquid in one or more tanks; and

[0037] b. selectively cycling the thermal storage liquid among the one or more tanks during a thermal cycling process,

[0038] wherein during the thermal cycling process, the thermal storage liquid is alternately heated and cooled, and wherein the same tanks are used to contain either cold or hot thermal storage liquid.

[0039] Example 2. The method according to example 1, wherein the selectively cycling comprises transferring cold thermal storage liquid from at least one tank to a first heat exchanger for absorbing heat from compressed gas during gas compression.

[0040] Example 3. The method according to example 1 or example 2, wherein the selectively cycling comprises transferring hot thermal storage liquid from at least one tank to a second heat exchanger for transferring heat to compressed gas prior to expansion in a turboexpander.

[0041] Example 4. The method according to any one of examples 1-3, wherein storing a thermal storage liquid comprising storing at a pressure greater than the vapor pressure of the thermal storage liquid at an operating temperature.

[0042] Example 5. The method according to any one of examples 1-4, wherein the storing comprising providing compressed gas above the thermal storage liquid to exert the pressure.Example 6. The method according to any one of examples 1-5, wherein storing the thermal storage liquid comprises maintaining at least one of the one or more tanks in an empty state.

[0043] Example 7. The method according to any one of examples 1-6, wherein the selectively cycling comprises coordinating the discharge of thermal storage liquid from one tank simultaneously with the filling of another tank with thermal storage liquid.

[0044] Example 8. An energy storage system comprising:

[0045] a. one or more tanks configured to contain a thermal storage liquid at hot and cold temperatures; and

[0046] b. a thermal cycling subsystem configured to selectively cycle the thermal storage liquid among the one or more tanks during a thermal cycling process,

[0047] 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.

[0048] Example 9. The system according to example 8, wherein the thermal storage liquid is water.

[0049] Example 10. The system according to example 8 or example 9, 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.

[0050] Example 11. An energy storage system, comprising:

[0051] 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;

[0052] 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;

[0053] 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;

[0054] e. one or more first heat exchangers positioned above water and configured to transfer heat from the compressed gas after compression to the TES;

[0055] 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; andg. 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.

[0056] Example 12. The system according to example 11, wherein the at least one environmental heat exchanger is configured to transfer heat from the waterbody surrounding the underwater compressed gas storage devices.

[0057] Example 13. The system according to example 11 or example 12, wherein the at least one environmental heat exchanger is configured to transfer heat from an industrial heat source.

[0058] Example 14. The system according to any one of examples 11-13, wherein the at least one environmental heat exchanger is configured to transfer heat from a geothermal source.

[0059] Example 15. The system according to any one of examples 11-14, wherein the thermal energy storage (TES) comprises one or more tanks configured to contain a thermal storage liquid, the one or more tanks being selectively connected to the one or more first heat exchangers and / or the one or more second heat exchangers.

[0060] Example 16. The system according to any one of examples 11-15, wherein at least one of the one or more tanks is configured to store cold thermal storage liquid, and is configured to store hot thermal storage liquid.

[0061] Example 17. The system according to any one of examples 11-16, wherein at least one tank 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 for preventing boiling and phase transition of the hot thermal storage liquid into vapor.

[0062] Example 18. The system according to any one of examples 11-17, further comprising a controller configured to selectively regulate operation of the one or more first heat exchangers, the one or more second heat exchangers, and the at least one environmental heat exchanger based on at least one of: temperature of the compressed gas, availability of environmental heat, and amount of heat stored in the TES.

[0063] Example 19. The system according to any one of examples 11-18, wherein the one or more turboexpanders comprise a plurality of turboexpanders arranged in series to facilitate multi-stage expansion of the compressed gas.

[0064] Example 20. The system according to any one of examples 11-19, further comprising at least one intermediate heat exchanger positioned between two of the plurality of turboexpanders, the intermediate heat exchanger being configured to transfer heat from the TES and / or an environmental heat source to the compressed gas between expansion stages.Example 21. The system according to any of examples 11 -20, comprising at least one shared heat exchanger, configured to function both as at least one of the one or more first heat exchangers and as at least one of the one or more second heat exchangers.

[0065] Example 22. The system according to example 21, comprising at least one switching valve configured to selectively direct flow of compressed gas either (i) from the one or more compressors toward the one or more underwater compressed gas storage devices during a compression mode, or (ii) from the one or more underwater compressed gas storage devices toward the one or more turboexpanders during a generation mode.

[0066] Example 23. The system according to any of examples 21-22, comprising at least one additional switching valve configured to selectively direct thermal storage liquid from either (i) at least one tank containing cold thermal storage liquid or (ii) at least one tank containing hot thermal storage liquid to the at least one shared heat exchanger.

[0067] Example 24. The system according to any one of examples 21-23, further comprising at least one second additional switching valve configured to selectively direct thermal storage liquid exiting the at least one shared heat exchanger to either (i) at least one tank containing hot thermal storage liquid or (ii) at least one tank containing cold thermal storage liquid.

[0068] Example 25. The system according to example 24, further comprising a controller configured to actuate the switching valve, the additional switching valve and the second additional switching valve such that, in a compression mode, compressed gas flows toward the underwater compressed gas storage devices while cold thermal storage liquid flows to the shared heat exchanger and returns to at least one tank containing hot thermal storage liquid, and, in a generation mode, compressed gas flows toward the one or more turboexpanders while hot thermal storage liquid flows to the shared heat exchanger and returns to at least one tank containing cold thermal storage liquid.

[0069] Example 26. The system according to any one of examples 11-25, further comprising at least one additional heat exchanger positioned downstream of a last one of the one or more turboexpanders and configured to cool a thermal storage liquid using expanded compressed gas to produce extracooled thermal storage liquid.

[0070] Example 27. The system according to example 26, further comprising at least one tank configured to store the extra-cooled thermal storage liquid.

[0071] Example 28. The system according to any one of examples 26-27, further comprising at least one heat exchanger positioned downstream of a last one of the one or more compressors and configured such that the extra-cooled thermal storage liquid flows therethrough to cool compressed gas and induce condensation of at least a portion of moisture contained in the compressed gas.Example 29. The system according to example 28, comprising a water trap configured to collect condensed liquid separated from the compressed gas, wherein the water trap is positioned in one or both:

[0072] (a) within the at least one heat exchanger; and

[0073] (b) along a conduit between an outlet of the at least one heat exchanger and an inlet of the one or more underwater compressed gas storage devices.

[0074] Example 30. The system according to any one of examples 11-29, wherein the one or more underwater compressed gas storage devices comprise a plurality of underwater compressed gas storage tanks.

[0075] Example 31. The system according to any one of examples 11-29, wherein the one or more underwater compressed gas storage devices comprise a plurality of underwater compressed gas storage tanks.

[0076] Example 32. The system according to example 31, wherein the plurality of underwater compressed gas storage tanks are arranged in one or more of:

[0077] a stacked configuration;

[0078] a clustered configuration; and

[0079] distributed along a seabed slope.

[0080] Example 33. The system according to any of examples 31-32, wherein the plurality of underwater compressed gas storage tanks are positioned at substantially a same height on a seabed.

[0081] Example 34. The system according to any of examples 31-32, wherein the plurality of underwater compressed gas storage tanks are positioned at different heights.

[0082] Example 35. The system according to any one of examples 31-34, wherein the plurality of underwater compressed gas storage tanks are in fluid communication with one another such that the plurality of tanks operate as one unit for receiving and releasing compressed gas.

[0083] Example 36. The system according to any one of examples 11 -35, wherein at least one of the one or more underwater compressed gas storage devices comprises an elongated polymer conduit configured to store compressed gas.

[0084] Example 37. The system according to example 36, further comprising one or more anchors mounted on the elongated polymer conduit and configured to counteract buoyancy and to submerge the elongated polymer conduit toward a seabed.

[0085] Example 38. The system according to example 36 or 37, wherein the elongated polymer conduit is at least partially encased in concrete cast around the elongated polymer conduit to form the one or more anchors.Example 40. The system according to any one of examples 36-39, further comprising at least one steel cable extending along at least a portion of the elongated polymer conduit and coupled to the one or more anchors.

[0086] Example 41. An energy storage system, comprising:

[0087] a. one or more underwater compressed gas storage tanks positioned at a depth in a waterbody and configured to store compressed gas;

[0088] b. a thermal energy storage (TES) assembly positioned above water and comprising one or more tanks configured to contain thermal storage liquid in hot or cold states;

[0089] d. at least one environmental heat exchanger positioned in the waterbody and configured to transfer heat from the waterbody to thermal storage liquid flowing through the one or more conduits; and

[0090] e. a controller configured to determine heat requirements for heating the compressed gas prior to expansion based on a depth of the one or more underwater compressed gas storage tanks and to selectively control heat transfer from the TES assembly and / or via at least one environmental heat exchanger.

[0091] Example 42. The system according to example 41, wherein the controller is configured to calculate a temperature difference between (i) the temperature of the waterbody at the depth of the one or more underwater compressed gas storage tanks, and (ii) the temperature of the cold thermal storage liquid in the TES assembly.

[0092] Example 43. The system according to example 41 or example 42, wherein the controller is configured to activate the at least one environmental heat exchanger to further cool the cold thermal storage liquid when the calculated temperature difference exceeds a predefined threshold.

[0093] Example 44. The system according to any one of examples 41-43, wherein the controller is configured to regulate operation of the at least one environmental heat exchanger to reduce the temperature of the thermal storage liquid to a level proximate to the temperature of the surrounding waterbody. 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.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0094] 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.

[0095] In the drawings:

[0096] Figure 1A 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;

[0097] Figure IB is a simplified block diagram of an exemplary system for storing energy and extracting work from a compressed gas energy storage system via a multi stages gas expansion process, according to some embodiments of the invention;

[0098] Figure 1C is a simplified block diagram of an exemplary system for storing energy and extracting work from a compressed gas energy storage system via a multi stages gas expansion process, according to some embodiments of the invention;

[0099] Figure 2A is a schematic representation of a cross section of an exemplary turbine used for converting energy of compressed gas to mechanical work, according to some embodiments of the invention;

[0100] Figure 2B is a schematic representation of a cross-section of an exemplary compressor used for increasing the pressure of a gas, according to some embodiments of the invention;

[0101] Figure 3A is a schematic representation of an exemplary system for storing energy and extracting work from the energy in a compressed gas energy storage system, according to some embodiments of the invention;

[0102] Figure 3B is a schematic representation of an exemplary compression subsystem, according to some embodiments of the invention;

[0103] Figure 3C is a schematic representation of an exemplary generation subsystem, according to some embodiments of the invention;

[0104] Figure 3D is a schematic representation of an exemplary generation subsystem, according to some embodiments of the invention;

[0105] Figure 3E is a schematic representation of an exemplary compression subsystem, according to some embodiments of the invention;

[0106] Figure 3F is a schematic representation of an exemplary compression subsystem, according to some embodiments of the invention;Figure 3G is a schematic representation of an exemplary compression subsystem, according to some embodiments of the invention;

[0107] Figure 3H is a schematic representation of an exemplary compression subsystem, according to some embodiments of the invention;

[0108] Figure 31 is a schematic representation of an exemplary generation subsystem, according to some embodiments of the invention;

[0109] Figure 3J is a schematic representation of an exemplary generation subsystem, according to some embodiments of the invention;

[0110] Figure 3K is a schematic representation of an exemplary generation subsystem, according to some embodiments of the invention;

[0111] Figure 3L is a schematic representation of an exemplary generation subsystem comprising an environment heat source, according to some embodiments of the invention;

[0112] Figure 3M is a schematic representation of an exemplary generation subsystem comprising an environment heat source, according to some embodiments of the invention;

[0113] Figure 4A is a schematic representation of an exemplary system for storing energy and extracting work from the energy in a compressed gas energy storage system, according to some embodiments of the invention;

[0114] Figure 4B is a schematic representation of an exemplary system for storing energy and extracting work from the energy in a compressed gas energy storage system, according to some embodiments of the invention;

[0115] Figure 4C is a schematic representation of an exemplary system for storing energy and extracting work from the energy in a compressed gas energy storage system, according to some embodiments of the invention;

[0116] Figure 4D is a schematic representation of an exemplary system for storing energy and extracting work from the energy in a compressed gas energy storage system, according to some embodiments of the invention;

[0117] Figure 4E is a schematic representation of an exemplary gas reservoir in a system which cycles gas, according to some embodiments of the invention;

[0118] Figure 4F is a schematic representation of an exemplary gas reservoir in a system which cycles gas, according to some embodiments of the invention;

[0119] Figure 5A is a schematic representation of an exemplary thermal energy storage, according to some embodiments of the invention;

[0120] Figure 5B is a schematic representation of an exemplary composite material for thermal energy storage, according to some embodiments of the invention;Figure 5C is a schematic representation of an exemplary thermal energy storage, according to some embodiments of the invention;

[0121] Figure 5D is a schematic representation of an exemplary TES system, according to some embodiments of the invention;

[0122] Figure 5E is a schematic representation of an exemplary TES system, according to some embodiments of the invention;

[0123] Figure 6 is a flowchart of an exemplary method for suppling heat to a thermal energy storage for preventing temperature decrease of a thermal energy storage, according to some embodiments of the invention;

[0124] Figure 7 is a schematic representation of a cross section of an exemplary thermal energy storage heating system, according to some embodiments of the invention;

[0125] Figure 8 is a flowchart of an exemplary method for preventing ice formation on blades of a turbine, according to some embodiments of the invention;

[0126] Figure 9 is a flowchart of an exemplary method for removing ice crystals formed on blades of a turbine, according to some embodiments of the invention;

[0127] Figures 10A-M are schematic representations of exemplary thermal exchange systems, according to some embodiments of the invention;

[0128] Figure 11 A 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;

[0129] Figure 1 IB 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;

[0130] Figures 12A-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;

[0131] Figures 12D-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;

[0132] Figure 13 is a schematic representation of a storage tank of a TES, according to some embodiments of the invention;

[0133] Figure 14A is a schematic representation of an exemplary generation subsystem comprising a stage for producing extra-cooled water for drying compressed gas, according to some embodiments of the invention;Figure 14B is a schematic representation of an exemplary compression subsystem configured to utilize extra-chilled water for removing moisture from compressed gas, according to some embodiments of the invention;

[0134] Figures 15A-C, are a schematic representation of an exemplary system for storing energy and extracting work from the energy in a compressed gas energy storage system using a shared heat exchanger configuration, according to some embodiments of the invention;

[0135] Figure 16A is 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;

[0136] Figure 16B is a schematic representation of an underwater energy storage device comprising a plurality of individual storage tank units stacked one of top of the other, according to some embodiments of the invention;

[0137] Figure 16C 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;

[0138] Figure 16D 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;

[0139] Figure 17 A 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;

[0140] Figure 17B 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;

[0141] Figure 17C 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;

[0142] Figures 18A-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;

[0143] Figure 18C 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;

[0144] Figure 18D 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;Figure 18E is a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention;

[0145] Figure 18F is a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention;

[0146] Figure 18G is a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention;

[0147] Figure 18H is a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention;

[0148] Figure 19 is a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention;

[0149] Figures 20A-B are a schematic representation of an energy storage device comprising a cluster of tubular structures, according to some embodiments of the invention;

[0150] Figure 20C is a schematic representation of a cluster of inter-connected tubular structures, according to some embodiments of the invention;

[0151] Figure 20D is a schematic representation of a cluster of inter-connected tubular structures, according to some embodiments of the invention;

[0152] Figure 21 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;

[0153] Figure 22 is a schematic representation of an energy storage device comprising a horizontally positioned tubular structure, according to some embodiments of the invention;

[0154] Figures 23A-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;

[0155] Figures 24A-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;

[0156] Figure 25 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;

[0157] Figure 26 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; and

[0158] Figure 27 is a schematic representation of an energy storage device comprising a plurality of interconnected storage tanks, according to some embodiments of the invention.DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

[0159] The present invention, in some embodiments thereof, relates to energy storage by compressing gas and storing the compressed gas, and utilization the energy by allowing the gas to expand for extracting work and, more particularly, but not exclusively, to energy storage by compressing gas and storing the compressed gas, and utilization the energy by allowing the gas to expand for extracting work and further transferring heat from both the compressed gas during the previously mentioned gas compression, and from an environmental source, to improve the overall energetic cycle.

[0160] Overview

[0161] An aspect of some embodiments of the invention relates to an underwater energy storage system interconnected to a thermal storage system positioned on land.

[0162] An aspect of some embodiments of the invention relates to an underwater energy storage system interconnected to a thermal storage system that harvest heat from self-generating sources and / or from external sources (like the environment, external factories, nuclear plants, etc.).

[0163] An aspect of some embodiments of the invention relates to an underwater energy storage system interconnected to a thermal storage system that utilizes the same storage tanks for storing, at one time hot water, at another time cold water. In some embodiments, there is at least one storage tank that remains empty. In some embodiments, “cold” water is defined as water at a temperature sufficiently low to cool gas exiting a compressor to a desired extent, subject to limitations and / or operational constraints of a given heat exchanger. In some embodiments, “hot” water is defined as water at a temperature sufficiently high to heat compressed gas entering a turbine to a desired extent, likewise subject to limitations and / or operational constraints of the heat exchanger used for heat transfer.An aspect of some embodiments of the invention relates to a thermal storage system that utilizes the same storage tanks for storing, at one time hot water, at another time cold water. In some embodiments, there is at least one storage tank that remains empty.

[0164] An aspect of some embodiments of the invention relates to increasing the Round-Trip Efficiency (RTE) of a process involving storing energy by compressing gas, storing the gas and extracting work from the compressed gas, while using from one or more of: heat generated during the gas compression, and heat from an external source that does not generate heat specifically for the purpose of the process.

[0165] RTE is a measure of how effectively an energy storage system captures and later delivers energy. RTE is defined as the ratio of the energy received from the system during discharge to the energy input during charging:

[0166] Energy Outout (Discharge)

[0167] RTE = - — - - —

[0168] Energy Input (Charge)A higher RTE indicates a more efficient system.

[0169] In some embodiments, the external heat source is an environmental source, for example seawater, lake water, or ambient air.

[0170] In some embodiments, the external heat source is industrial unused heat generated as a byproduct of a separate process, such as a coal-based power plant, a steel manufacturing facility, or a nuclear reactor.

[0171] Optionally, the system which 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 from the nuclear reactor. Additionally, when the electrical grid demands increased power, the system is capable of supplying energy to the electrical grid. In this manner, excess energy generated by the reactor during periods of low demand (e.g., at night) is stored and later released to the grid during periods of higher demand (e.g., during the day). A potential benefit of pairing such an energy storage system with a nuclear reactor or coal power station is that such stations often have a slow response to a sudden increase (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. The presence of the storage system allows the reactor to operate at a stable base-load level while the stored energy is dispatched to the grid as needed, thereby bridging the temporal gap between energy production and energy demand.

[0172] Similarly, an air-based storage system may be integrated with a steel plant, as steel production processes typically generate substantial amounts of excess heat. Such waste heat can be utilized by the storage system to improve overall thermal efficiency and round-trip efficiency (RTE). Energy may be stored, for example, during off peak hours and used for peak demand and / or if there are electrical supply problems.

[0173] Potential advantages of using compression heat along with heat from at least one external heat source in the process involving storing energy by compressing gas, storing the gas and extracting work from the compressed gas are:• reducing or eliminating the size and cost of thermal storage needed for storing the heat from gas compression;

[0174] • utilizing otherwise unused thermal energy, thereby improving sustainability of the system. An aspect of some embodiments of the invention relates to using the same tanks for storing liquids at different phases of a heat cycling process.

[0175] In some embodiments, a thermal storage liquid is used to store and move heat in a thermal process, and it is stored in two forms: cold thermal storage liquid, and hot thermal storage liquid. As used herein, the term “thermal storage liquid” means any type of liquid capable of storing thermal energy, for example water, oil and / or glycol.

[0176] In some embodiments, the tanks are configured to operate under pressure conditions selected to ensure that the hot thermal storage liquid remains in the liquid phase at elevated operating temperatures, for example, after the thermal storage liquid absorbed heat from gas during gas compression. In some embodiments, where the thermal storage liquid is water, its saturation pressure increases with temperature: approximately 1 bar at 100 °C, 2 bar at 120 °C, 10 bar at 180 °C, 20 bar at 212 °C, 50 bar at 260 °C, and 100 bar at 311 °C. By maintaining the tank at a pressure above the saturation pressure for the corresponding temperature, the hot thermal storage liquid is prevented from boiling and undergoing a phase transition to vapor, potentially preventing uncontrolled, dangerous pressure spikes due to boiling.

[0177] In some embodiments, both the cold and the hot thermal storage liquid is maintained in the tanks at a boiling preventing pressure, potentially preventing pressure differences between the tanks.

[0178] Typically, separate storage devices are used for these two forms, for example, hot liquid is stored in closed tanks while cold liquid is stored in open pools or reservoirs.

[0179] In contrast, in some embodiments, the same tanks are configured to serve alternately as hot or cold liquid reservoirs. After hot thermal storage liquid is discharged and cooled, it can be returned into one of the (now empty) tanks as cold liquid, thereby eliminating the need for separate cold storage devices. At any given time, one tank may be emptied and subsequently refilled with liquid at a different temperature.

[0180] Potential advantages of using the same tanks for storing liquids at different stages of a heat cycling process are reducing costs of manufacturing by reducing the number of tanks, and / or reducing the space required for storing the thermal storage liquid.

[0181] An aspect of some embodiments of the invention relates to managing heat in an energy storage system that combines underwater compressed gas storage with above- thermal energy storage (TES).

[0182] In some embodiments, compressed gas is stored in one or more tanks positioned at depth in a waterbody. Heat generated during compression of the gas is stored in an above-water TES in thermalstorage liquid contained within one or more tanks. During discharge, the compressed gas is heated with heat from the TES before the compressed gas is allowed to enter and expand in a turboexpander for extracting work.

[0183] In some embodiments, one or more conduits circulate the thermal storage liquid between the TES and one or more heat exchangers. In some embodiments, the system is configured to utilize environmental heat.

[0184] In some embodiments, a controller determines how much heating of the compressed gas is required prior to expansion based on the pressure.

[0185] An aspect of some embodiments of the invention relates to supplying compressed gas to turbines at a substantially constant pressure.

[0186] In conventional compressed air energy storage (CAES) systems, compressed gas is typically stored in a rigid cavern or tank where the pressure decreases as the gas is discharged. As a result, the turbine inlet pressure and temperature vary significantly during discharge, which may reduce aerodynamic efficiency.

[0187] In contrast, in some embodiments, the compressed gas is stored in an underwater storage in which the pressure of the compressed gas is counterbalanced by hydrostatic pressure, which maintains a substantially fixed pressure at a given depth. Maintaining substantially fixed turbine inlet pressure ensures that the turbine operates at a consistent working point during work extraction from the compressed gas.

[0188] In some embodiments, a control system is configured to coordinate between a compressed gas heating unit and the turbine inlet such that the turbine always receives compressed gas at the same pressure and the same temperature.

[0189] A potential advantage of operating the turbine at a constant working point, for example by maintaining a fixed inlet pressure and temperature of the compressed gas, is improved turbine efficiency. Turbines are typically optimized to perform at a defined set of operating conditions, and fluctuations away from that point reduce aerodynamic efficiency.

[0190] An aspect of some embodiments of the invention relates to storing compressed gas in underwater elongated pipe structures positioned horizontally on a seabed. In some embodiments, the system comprises one or more pipes (for example, elongated pipes) laid along the seabed. In some embodiments, the one or more pipes are made of commercially available pipes. A potential advantage of the one or more pipes made of commercially available pipes is easiness of production.

[0191] The one or more pipes 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 pipes comprise an opening located a lower portion of the one or more pipes for enabling water to enter and exit as gas volume within the one or more pipes changes.

[0192] In some embodiments, optionally, weights are attached to or placed over the one or more pipes to prevent the one or more pipes from floating, for example when the one or more pipes are filled with compressed gas. In some embodiments, other means are used to ensure that pipes will stay under water in any situation (for example, when empty or when filled with compressed gas).

[0193] A potential advantage of the one or more elongated pipes is scalability and cost-effectiveness compared to rigid concrete or metallic tanks.

[0194] An aspect of some embodiments of the invention relates to anchoring one or more underwater compressed gas storage conduits using one or more anchors configured to secure the conduits to a seabed and counteract buoyancy forces when the conduits are empty and / or when filled with compressed gas. In some embodiments, the use of anchors allows the storage conduits to be formed from relatively lightweight materials, such as polymer pipes (e.g., polyethylene (PE) pipes). A potential advantage of utilizing such polymer pipes is reduced manufacturing cost, ease of transportation and handling, corrosion resistance in marine environments, mechanical flexibility that accommodates seabed irregularities, and / or scalability through the use of commercially available pipe sections. In some embodiments, the one or more anchors are mounted onto the conduit prior to deployment into the waterbody. In some embodiments, the conduit together with the pre-mounted anchors is temporarily coupled to one or more flotation elements (e.g., buoys), allowing the conduit to be navigated and / or towed along the water surface to a designated offshore deployment location. Upon reaching the deployment location, the conduit is detached from the flotation element, thereby allowing the anchored conduit to descend and settle onto the seabed in a controlled manner. In some embodiments, at least some of the disclosed implementations cover different anchoring configurations and design tradeoffs, including configurations in which a ratio is maintained between (i) a volume (and / or mass) of anchoring material (e.g., concrete) configured to sink the conduit and (ii) a volume of trapped gas contained within the conduit, thereby ensuring that the net buoyancy is counterbalanced by the anchoring arrangement. In some embodiments, the anchoring arrangement comprises a plurality of anchors positioned along a length of the conduit and spaced apart from one another to reduce total anchoring material usage (e.g., to reduce concrete consumption). In some embodiments, a spacing between adjacent anchors is selected to reduce bending, bowing, and / or excessive curvature (“arching”) of the conduit between anchors. In other embodiments, the anchors are positioned in a closely spaced arrangement (optionally substantially adjacent, with small gaps or without gaps) alongat least a portion of the conduit length, potentially to further reduce bending and / or localized deformation of the conduit wall and / or to form a substantially continuous anchored region.

[0195] In some embodiments, the anchoring arrangement further comprises a tensile element (e.g., a steel cable) extending along at least a portion of the conduit length, optionally routed through one or more anchors via a cable passage, clearance channel, notch, slot, and / or opening. The tensile element may further reduce bending and / or flexing of the conduit and / or reduce mechanical loading on anchoring elements (e.g., concrete-based anchors). In some embodiments, the tensile element (e.g., cable) is further configured to assist in alignment and / or positioning of the anchors during installation, for example, by maintaining the anchors in a predetermined spatial relationship along the conduit as they are deployed and lowered to the seabed. In some embodiments, the anchor at least partially surrounds the conduit, for example, comprising a ring-like portion configured to be slid onto and / or closed around the conduit, and / or in some embodiments, the anchor comprises an encasement formed by casting (e.g., concrete cast) around at least a portion of the conduit. In some embodiments, the anchor comprises a weighted portion at a lower region configured to sink the conduit, optionally including protrusions, spikes, and / or sharp regions configured to engage the seabed, wherein a center of mass of the anchor biases the protrusions to face downward.

[0196] An aspect of some embodiments of the invention relates to drying and / or dehumidifying compressed gas supplied to an underwater compressed gas storage system by utilizing thermal energy and / or cooling capacity generated within the energy storage process itself (e.g., process-derived cooling), optionally reducing and / or eliminating a need for dedicated external drying and / or refrigeration equipment (optionally, while improving overall system efficiency and / or round-trip efficiency (RTE)). In some embodiments, during discharge the compressed gas is conveyed through one or more underwater conduits, where heat transfer to surrounding water cools the gas and may cause condensation. Accordingly, in some embodiments, drying and / or dehumidifying the compressed gas reduces and / or prevents condensation in the underwater conduit, thereby reducing flow disturbances, pressure losses, and / or partial blockage.

[0197] In some embodiments, the system comprises a cooling stage positioned at or near an outlet of a last compression stage, configured to cool the compressed gas to induce controlled condensation and / or removal of moisture prior to introduction into the underwater storage tanks. In some embodiments, the cooling stage comprises a heat exchanger and a water trap configured to collect and discharge condensed water.

[0198] In some embodiments, the cooling medium (thermal storage liquid) comprises extra-cooled liquid (e.g., water) produced during a discharge (generation) process, for example, by using cooled expanded gas downstream of one or more turboexpanders to cool a thermal storage liquid below atemperature of the surrounding waterbody. The extra-cooled liquid is optionally stored and / or recirculated to cool the compressed gas during a subsequent compression process.

[0199] An aspect of some embodiments of the invention relates to a compressed gas energy storage system comprising one or more shared heat exchangers configured to operate selectively in different operational modes, including a compression mode and a power generation mode.

[0200] In some embodiments, the system comprises an array of shared switching valves and / or an array of shared conduits, configured to selectively determine whether the shared heat exchangers operate in a heating configuration (e.g., supplying heat to compressed gas during generation mode) or in a cooling configuration (e.g., removing heat from compressed gas during compression mode). In some embodiments, during compression mode, relatively cold thermal storage liquid is directed from a cold storage tank to the shared heat exchangers, absorbs heat from the compressed gas, and / or is subsequently delivered to a hot storage tank. In some embodiments, during generation mode, relatively hot thermal storage liquid is directed from the hot storage tank to the shared heat exchangers, transfers heat to the compressed gas prior to expansion, and / or is subsequently returned as cooled liquid to the cold storage tank.

[0201] In some embodiments, the system further comprises the same or additional array of shared switching valves and / or an array of shared conduits, configured to selectively route compressed gas either (i) from one or more compressors to an underwater compressed gas storage unit during compression mode, and / or (ii) from the underwater compressed gas storage unit through one or more turbines during generation mode.

[0202] A potential advantage of utilizing shared heat exchangers is reducing system cost and / or complexity by reducing the number of dedicated heat exchangers required for separately supporting compression and generation processes, potentially while maintaining efficient thermal coupling to a thermal energy storage (TES) system.

[0203] An aspect of some embodiments of the invention relates to an underwater energy storage system comprising a plurality of underwater compressed gas storage units positioned at depth in a waterbody, the plurality of underwater compressed gas storage units being fluidly interconnected and configured to operate collectively as a single storage system for receiving and releasing compressed gas. In some embodiments, the plurality of underwater compressed gas storage units are arranged at substantially the same height, at different heights, stacked, clustered, or distributed along a seabed slope, and is configured to share one or more common gas conduits and / or valves, thereby potentially providing scalable capacity, modular construction, improved load distribution, and enhanced operational flexibility.An aspect of some embodiments of the invention relates to systems for storing energy and / or extracting work from a compressed gas energy configured to be operatively coupled to and / or integrated with substantially any suitable compressed gas storage arrangement, irrespective of structural configuration, operating methodology, or geographic location. In some embodiments, the compression, thermal management, heating, expansion, and / or control subsystems described herein are configured to receive compressed gas from and / or to deliver compressed gas to any compatible gas storage system, whether positioned on land, underground, underwater, offshore, airborne, elevated, mobile, or distributed across multiple locations. In some embodiments, the gas storage arrangement may comprise rigid pressure vessels, underground caverns, hydrostatically balanced underwater structures, pipeline-based storage networks, modular storage units, flexible membranebased reservoirs, phase-changing gas storage systems (e.g., supercritical or liquefied gas storage), and / or combinations thereof. In some embodiments, the thermodynamic and thermal subsystems described herein are structurally and operationally decoupled from the physical configuration of the gas storage unit, thereby allowing the disclosed energy storage and work extraction methodologies to be implemented independently of the specific storage topology.

[0204] 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.

[0205] 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.

[0206] 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 turbine, converting the energy from the compressed gas into mechanical work, which can then be used to generate electricity.

[0207] The efficiency of the energy production process is calculated by comparing the energy produced by the turbine 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 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 turbine. It has been proposed to store heat generated during the gas compression to be used in other parts of the energy production process,reducing the need for additional heating and thereby increasing the efficiency of the energy production process.

[0208] Referring now to Figure 1A, showing 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. In some embodiments, a system 100 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 100 compresses and stores the gas during periods of energy surplus and generates energy from the compressed gas during periods of energy shortage.

[0209] The system 100 comprises one or more gas compressors 102, which use energy to increase the pressure of the gas, resulting in compressed gas. An example of a gas compressor from the one or more gas compressors 102 is presented in Figure 2B.

[0210] During the compression of the gas in the one or more gas compressors 102, heat is generated, and the temperature of the gas increases.

[0211] In some embodiments, the heat generated during the compression is transferred to a Thermal Energy Storage 106 (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 102, thereby allowing the use of more cost-efficient materials that are optimized for lower temperature operation.

[0212] While in some embodiments, the TES 106 has one chamber for storing heat at a single temperature, in some embodiments, the TES 106 is a multi-chambers assembly for storing heat at different temperatures.

[0213] In some embodiments, the compressed gas is stored in a compressed gas storage unit 104. In some embodiments, the compressed gas storage unit 104 is positioned in an underwater location for counterbalancing the pressure of the compressed gas by the natural hydrostatic pressure provided by the water body. Tn some embodiments, the compressed gas storage unit 104 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 in U.S. Provisional Patent Application No. 63 / 762,182, and as shown in Figures 13A-C.

[0214] In some embodiments, the compressed gas storage unit 104 is a closed tank.

[0215] In some embodiments, a Work-Extracting Gas Expander (WEGE) 108 converts the energy stored in the compressed gas to mechanical work. In some embodiments, upon demand, the compressed air is released from the compressed gas storage unit 104 and allowed to enter the WEGE 108 and expand. In some embodiments, the WEGE 108 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, as further illustrated in relation to Figure 2 A.

[0216] In some embodiments, the WEGE 108 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.

[0217] During the expansion of the compressed gas in the WEGE 108, the temperature of the gas decreases.

[0218] In some embodiments, it is desirable to heat the compressed gas just before it enters the WEGE 108, thereby controlling the temperature of the gas after expansion. For example, by pre-heating the compressed gas, the temperature at the WEGE 108 outlet is maintained at or above a target temperature, for example, 0.5°C, thereby preventing freezing of water vapor present in the compressed gas. Potential advantages of pre-heating the compressed gas before entering the WEGE 108 are enabling effective work extraction by increasing the enthalpy of the compressed gas prior to expansion, and preventing ice formation that could damage system components.

[0219] In some embodiments, the compressed gas flows from the compressed gas storage unit 104 to the WEGE 108 via a connector 110. In some embodiments, within the connector 110, the compressed gas is heated prior to entering the WEGE 108.

[0220] In some embodiments, the compressed gas is heated by absorbing heat from multiple heat sources.

[0221] Optionally, in a first heating stage, heat is transferred to the compressed gas using heat from the environment 112, for example, heat from industrial processes and / or geothermal activity, and / or heat from the surrounding waterbody. A potential advantage of using heat from the environment 112 for heating the compressed gas is increasing the RTE of the work extraction process by using available, low-cost energy.

[0222] In some embodiments, alternatively or additionally, optionally in a second heating stage, heat is transferred from the TES 106. A potential advantage of using heat from the TES 106 to heat the compressed gas is increasing the RTE of the work extraction process by using heating emitted during compression to heat the compressed gas.

[0223] Referring now to Figure IB, showing a simplified block diagram of an exemplary system for storing energy and extracting work from a compressed gas energy storage system via a multi-stage gas expansion process, according to some embodiments of the invention.

[0224] In some embodiments, the system 100 facilitates the gas to expand through a multi stages process. In this process, the gas pressure is initially lowered to a certain pressure in a first stage, thenfurther decreased in one or more additional stages, gradually reducing the pressure until the pressure reaches a desired low pressure, for example atmospheric pressure. The gradual pressure reduction results with a gradual decrease in temperature of the gas. Potential advantages are high temperature control of the gas expansion, enabling the prevention of ice formation and enabling the use of materials designed to withstand a smaller temperature range, and increasing the RTE of the process by providing the gas at a temperature difference from the outside water environment, which is suitable to absorb heat from the outside water environment.

[0225] In some embodiments, the WEGE 108 comprises a 1stWEGE 108A and a 2ndstage WEGE 108B, for facilitating a multi stages gas expansion.

[0226] In some embodiments, a compression heat exchanger 114 transfers the heat from the compressed gas to the TES 106.

[0227] The compressed gas flows from the compressed gas storage unit 104 to the 1stWEGE 108A via a connector 110A. In some embodiments, within the connector 110A, the compressed gas is heated prior to entering the 1stWEGE 108A.

[0228] Optionally, the compressed gas is first heated prior to entering a first expansion stage at a 1stWEGE 108A, via a 1stenvironmental heat exchanger 116. In some embodiments, the 1stenvironmental heat exchanger 116 transfers heat from the environment 112.

[0229] In some embodiments, additionally or alternatively, the compressed gas is heated prior to entering a first expansion stage at a 1stWEGE 108A, via a 1stTES heat exchanger 118, which transfers heat from the TES 106 to the compressed gas.

[0230] After the compressed gas expands through the 1stWEGE 108A, the partially compressed gas then flows via a connector HOB to a second expansion stage.

[0231] In some embodiments, within the connector HOB, the partially compressed gas is heated prior to entering the 2ndWEGE 108B. Optionally, the partially compressed gas is first heated via a 2ndenvironmental heat exchanger 120, which transfers heat from the heat from the environment 112.

[0232] Additionally or alternatively, the 2ndenvironmental heat exchanger 120 transfers heat to the partially compressed gas from the surrounding environment by the connector HOB being immersed within, for example, a waterbody.

[0233] In some embodiments, additionally or alternatively, the partially compressed gas is heated via a 2ndTES heat exchanger 122, which transfers heat from the TES 106 to the partially compressed gas.

[0234] In some embodiments, at least one of the compression heat exchanger 114, the 1stenvironmental heat exchanger 116, the 1stTES heat exchanger 118, the 2ndenvironmental heat exchanger 120, and the 2ndTES heat exchanger 122, transfers heat within the system 100 using one or more heat transfer mediums.In some embodiments, the one or more intermediate elements are solid thermal pathways, and are made of a high thermal conductivity material, for example, aluminum, stainless steel, and / or graphite.

[0235] Alternatively, the one or more intermediate elements are pipes which allow a heat transfer fluid to flow inside the pipes, optionally to circulate within the system 100. In some embodiments, the heat transfer fluid is, for example, water, oil, or Glycol. A potential advantage of the pipes, which allow a fluid to fluid is avoiding the need to directly circulate the gas to transfer its heat, minimizing potential pressure loss.

[0236] Alternatively or optionally, one or more gas pipes directly transfer gas (input gas and / or output gas) to and / or from the TES 106, allowing the heat storage device to either absorb heat from the gas or to transfer heat to the gas.

[0237] Alternatively or additionally, at least one of the compression heat exchangers 114, the 1stenvironmental heat exchanger 116, the 1stTES heat exchanger 118, the 2ndenvironmental heat exchanger 120, and the 2ndTES heat exchanger 122, transfers the heat within the system 100 by directing the gas to make direct contact with the TES 106, thereby transferring heat directly.

[0238] In some embodiments, at least one of the compression heat exchanger 114, the 1stenvironmental heat exchanger 116, the 1stTES heat exchanger 118, the 2ndenvironmental heat exchanger 120, and the 2ndTES heat exchanger 122 transfers the heat within the system 100 using design features that enhance heat exchange, for example, potentially increasing and optionally maximizing surface area.

[0239] In some embodiments, at least one of the compression heat exchanger 114, the 1stenvironmental heat exchanger 116, the 1stTES heat exchanger 118, the 2ndenvironmental heat exchanger 120, and the 2ndTES heat exchanger 122 are commercially available heat exchangers.

[0240] In some embodiments, the system 100 circulates water from the surrounding waterbody through at least one of the compression heat exchanger 114, the 1stenvironmental heat exchanger 116, the 1stTES heat exchanger 118, the 2ndenvironmental heat exchanger 120, and the 2ndTES heat exchanger 122. In some embodiments, the water is returned to the surrounding waterbody at a lower temperature.

[0241] Referring now to Figure 1C, showing a simplified block diagram of an exemplary system for storing energy and extracting work from a compressed gas energy storage system via a multi-stage gas expansion process, according to some embodiments of the invention.

[0242] In some embodiments, Figure 1C illustrates an implementation (i.e., a specific example) of the multi-stage configuration described in relation to Figure IB, in which the heating of the gas prior to each expansion stage is performed using selected heat sources (e.g., using environmental heatexchanger 116 or heat exchanger 122). It is to be noted that although Figure 1C illustrates an example comprising two expansion stages, the expansion process is not limited to two stages. In some embodiments, the compressed gas expands through three or more expansion stages, for example, from 3 to 5 stages, optionally from 4 to 8 stages, optionally from 6 to 12 stages, or a lower, intermediate, or higher number of stages.

[0243] In some embodiments, prior to a first expansion stage at 1st WEGE 108 A, compressed gas flowing from gas storage unit 104 to 1st WEGE 108A via a connector 110A is heated using environmental heat exchanger 116 that transfers heat from the environment. After the gas expands through the 1st WEGE 108A and flows via a connector HOB toward a second expansion stage at a 2nd WEGE 108B, the partially expanded gas is heated using a TES heat exchanger 122 that transfers heat from Thermal Energy Storage (TES) 106. In some embodiments, this arrangement provides an example of a two-stage expansion process in which environmental heat is used in a first heating stage and stored compression heat (via the TES), which is used in a subsequent heating stage, thereby potentially supporting temperature management across stages and / or improving overall work extraction performance. In other embodiments, the order of the heating sources may be reversed, such that prior to the first expansion stage at 1st WEGE 108A, compressed gas flowing via the connector 110A is heated using TES heat exchanger 122, which transfers heat from Thermal Energy Storage (TES) 106. After the gas expands through 1st WEGE 108A and flows via connector 110B toward the second expansion stage at 2nd WEGE 108B, the partially expanded gas is heated using environmental heat exchanger 116, which transfers heat from the environment.

[0244] In some embodiments, the order of the heating sources (i.e., using environmental heat exchanger 116 prior to the first expansion stage and TES heat exchanger 122 prior to the second expansion stage, or vice versa) is selected based on temperature-related considerations. For example, the selected order is based on one or more of: a temperature of the compressed gas upstream of a respective expansion stage, a target inlet temperature to the 1 st WEGE 108 A and / or the 2nd WEGE 108B, a temperature level and / or available thermal capacity of the TES 106, and a temperature of the environment.

[0245] A potential advantage of the separation between the environmental heat exchange and the TES heat exchange is improved thermal management and / or operational efficiency. The use of environmental heating potentially allows the utilization of readily available, low-cost thermal energy, optionally while allowing more efficient and targeted heat transfer from the TES. This separation potentially improves overall heat exchange performance and / or the thermodynamic efficiency of the system.Referring now to Figure 2A, showing a schematic representation of a cross section of anexemplary turbine used for converting energy of compressed gas to mechanical work, according to some embodiments of the invention.

[0246] As a gas expands and increases in volume, the gas pushes against external constraints. For example, if a gas is used to drive a piston or a turbine, the gas exerts a force over a distance (corresponding to the movement of the piston or turbine blades), transferring energy from the gas to the mechanical system (piston or turbine). This transferred energy is the work extracted from the gas. During this expansion, the temperature of the gas decreases due to the reduction in pressure and the associated conversion of internal energy into mechanical work.

[0247] In some embodiments, a turbine 200 operates to convert the energy of high-pressure compressed gas into mechanical rotational energy. In some embodiments, the turbine 200 is positioned in a housing 202. In some embodiments, the housing 202 is a pipe. In some embodiments, compressed gas enters through an inlet 204 and is directed by one or more nozzles 206 to a turbine impeller 208 which is equipped with a plurality of blades 210. In some embodiments, the plurality of blades 210 are shaped and angled to efficiently capture energy from the compressed gas by enabling the compressed gas to exert lift and drag forces on the plurality of blades 210, creating a torque that causes the turbine impeller 208 to rotate. In some embodiments, the rotational energy is transmitted via a shaft 212 to a generator or another system (not shown in Figure 2A) for work output. As the compressed gas expands within the housing 202, the pressure and temperature of the compressed gas decrease. In some embodiments, the expanded gas is directed through an exhaust outlet 214 for exiting the housing 202.

[0248] Optionally, one or more heating elements 216 heat the plurality of blades 210 to prevent ice crystals formation on the plurality of blades 210 due to the temperature decrease of the expended gas, for example using infrared (IR) heating. Optionally, the plurality of blades 210 are equipped with a heat absorption enhancing coating, for example, the heat absorption enhancing coating may be a high-emissivity material or a dark, infrared-absorbing layer.

[0249] Referring now to Figure 2B, showing a schematic representation of a cross-section of an exemplary compressor used for increasing the pressure of a gas, according to some embodiments of the invention. In some embodiments, a compressor 250 operates to convert mechanical energy into pressure energy in a gas. In some embodiments, the mechanical energy is generated from electrical energy, for example by an electric motor, and is then converted by the compressor into pressure energy in the gas. In some embodiments, the compressor 250 is positioned within a housing 218, which in some embodiments may be a pipe. In some embodiments, gas enters the compressor 250 through an inlet 220 and is directed by one or more nozzles 222 onto a compressor impeller 224, which is equipped with a plurality of blades 226.In some embodiments, the plurality of blades 226 are shaped and angled to efficiently impart energy to the gas. The efficiently imparting energy to the gas is achieved by the rotation of the compressor impeller 224, which accelerates the gas and increases its kinetic energy. The kinetic energy of the gas is then converted into pressure energy as the gas flows through a diffuser 228. The rotation of the impeller is driven by a shaft 230, which is connected to a motor or another mechanical energy source (not shown in Figure 2B). In some embodiments, the compressed gas exits the housing 218 through an outlet 232, to be stored or used in downstream systems.

[0250] During compression, the temperature of the gas increases.

[0251] In some embodiments, the compressor 250 is equipped with a heat exchanger 234, positioned downstream of the diffuser 228 and outlet 232, for transferring heat from the compressed gas to a thermal heat storage device, for example the TES shown in Figures 5A-D.

[0252] and work extraction

[0253]

[0254] Referring now to Figure 3A, showing a schematic representation of an exemplary system for storing energy and extracting work from the energy in a compressed gas energy storage system, according to some embodiments of the invention. A system 300 compresses gas, stores the compressed gas, and extracts work from the compressed gas. In some embodiments, at least a portion of the system 300 is positioned in an underwater location. The system 300 comprises a compression subsystem 300A which compresses a gas 302A and harvests heat from the gas 302A after compression. The system 300 further transfers the heat to a thermal energy storage (TES) 306, as further explained in relation to Figure 3B. In some embodiments, the gas 302A is in an uncompressed state and has atmospheric pressure.

[0255] The compression subsystem 300A compresses the gas 302A and communicates a gas 302D, which is a compressed state of the gas 302A, to a compressed gas storage unit 304 which is designed to withstand the pressure of the gas 302D.

[0256] The system 300 further comprises a generation subsystem 300B which extracts work from the gas 302D. Upon demand, the compressed gas storage unit 304 releases the gas 302D to the generation subsystem 300B. The generation subsystem 300B transfers heat from the TES 306 to gases 302D, 302E and 302F, which are the gas 302D in different expansion stages, as further explained in relation to Figure 3C.

[0257]

[0258] Referring now to Figure 3B, showing a schematic representation of an exemplary compression subsystem, according to some embodiments of the invention. In some embodiments, the gas 302A issupplied to a first compressor 310A from a gas source (not shown in Figure 3B) via a first connector 308A and, in some embodiments, the gas source directly contacts the first compressor 310A. In some embodiments, the first connector 308A is a pipe, fluidly connecting the gas source to the first compressor 310A.

[0259] In some embodiments, the first compressor 310A increases the pressure of the gas 302A, optionally, by reducing the volume of the gas 302A. In some embodiments, the gas 302B then flows to a first heat exchanger 312A via a second connector 308B. In some embodiments, the heat exchanger 312A transfers the heat from the gas 302A after compression, to the TES 306. Optionally, the TES 306 comprises a plurality of chambers for storing heat at different temperatures, for example as shown in Figures 3H and 3K.

[0260] In some embodiments, the gas 302B, having been cooled, then flows via a third connector 308C to a second compressor 310B.

[0261] In some embodiments, the second compressor 310B compresses the gas 302B.

[0262] In some embodiments, the gas 302C flows via a fourth connector 308D to a second heat exchanger 312B, which transfers the heat from the gas 302B after compression, to the TES 306.

[0263] In some embodiments, the gas 302C, having been cooled, then flows via a fifth connector 308E to a third compressor 310C.

[0264] In some embodiments, the third compressor 310C compresses the gas 302C. In some embodiments, the gas 302D flows via a sixth connector 308F to a third heat exchanger 312C, which transfers the heat from the gas 302C after compression, to the TES 306.

[0265] In some embodiments, the gas 302D then flows via a seventh connector 308G to the compressed gas storage unit 304, where the gas 302D is stored to be released upon demand.

[0266] In some embodiments, the gas 302D which is in a compressed state, has a pressure, for example, from lOatm to 70atm, optionally from 30atm to lOOatm, optionally from 5 atm to 120atm.

[0267] Tn some embodiments, each of the heat exchangers 312A, 312B and 312C is connected to conduits 314A, 314B and 314C accordingly for transferring heat. In some embodiments, each of the conduits 314A, 314B and 314C connect to a main conduit 316, accumulating the heat and transferring the accumulated heat to the TES 306 and, in some embodiments, each of the conduits 314A, 314B and 314C is connected directly to the TES 306, for example as shown in Figure 3D, and in some embodiments, the conduits 314A and 314B connect the heat exchangers 312A, 312B and 312C to one another and the one or more conduits 314C transfer the accumulated heat to the TES 306, for example as shown in Figure 3F. Potential advantages of the main conduit 316 connected to the conduits 314A, 314B and 314C is simple design and space saving.Alternatively, the gases 302B, 302C and 302D which underwent compression contact directly the TES 306 for transferring heat to the TES 306, for example as shown in Figure 3G.

[0268] Referring now to Figure 3C, showing a schematic representation of an exemplary generation subsystem, according to some embodiments of the invention. In some embodiments, upon demand, the gas 302D is released from the compressed gas storage unit 304 and allowed to expand. In some embodiments, the gas 302D flows to a fourth heat exchanger 312D via an eighth connector 308H. In some embodiments, the fourth heat exchanger 312D transfers heat from the TES 306 to heat the gas 302D.

[0269] In some embodiments, the gas 302D which is heated then flows via a ninth connector 3081 to the first turbine 318A which extracts work from the gas 302D. In some embodiments, the gas 302E then flows via a tenth connector 308J to a fifth heat exchanger 312E which transfers heat from the TES 306 to heat the gas 302E.

[0270] In some embodiments, the gas 302E being heated then flows via an eleventh connector 308K to a second generator 318B which extracts work from the gas 302E. In some embodiments, the gas 302F then flows via a twelfth connector 308L to a sixth heat exchanger 312F which transfers heat from the TES 306 to heat the gas 302F.

[0271] In some embodiments, the gas 302F being heated then flows via a thirteenth connector 308M to a third turbine 318C which extracts work from the gas 302F. In some embodiments, a gas 302G then flows via a fourteenth connector 308N to a gas outlet (not shown in Figure 3C).

[0272] A potential advantage of extracting work from the gas 302D in a multi stage process comprising the turbines 318A, 318B and 318C is preventing ice formation on the blades.

[0273] In some embodiments, the TES 306 connects to a main conduit 322 which branches to conduits 320A, 320B, and 320C for transferring heat from the TES 306 to the gases 302D, 302E and 302F, via the heat exchangers 312D, 312E and 312F, accordingly. In some embodiments, each of the conduits 320A, 320B and 320C is connected directly to the TES 306, for example as shown in Figure 3H.

[0274] Alternatively, the gases 302D, 302E, and 302F, before undergoing expansion, contact directly the TES 306 for receiving heat from the TES 306, for example, as shown in Figures 31 and 3J.

[0275] Referring now to Figure 3D, showing a schematic representation of an exemplary generation subsystem, according to some embodiments of the invention. In some embodiments, the generation subsystem 300B further comprises environmental heat exchangers 324A and 324B for pre-heating the gas 302E and 302F to approximately ambient temperature before being further heated by the heat exchangers 312E and 312F, accordingly.

[0276] In some embodiments, the gases 302E and 302F flow to the environmental heat exchangers 324A, and 324B, via connectors 308P and 308Q, accordingly.In some embodiments, the environmental heat exchangers 324A and 324B use water at ambient temperature, optionally sourced from a water body where at least a portion of the generation subsystem 300B is located. A potential advantage of pre-heating the gas 302E and 302F with water from a water body where at least a portion of the generation subsystem 300B is located is increasing the efficiency of the work extraction process.

[0277] In some embodiments, the ambient temperature is from about 20 to 25 degrees Celsius, optionally from about 30 to 45 degrees Celsius, optionally from about 10 to 20 degrees Celsius.

[0278] Referring now to Figure 3E, showing a schematic representation of an exemplary compression subsystem, according to some embodiments of the invention. In some embodiments, each of the conduits 314A, 314B and 314C are connected directly to the TES 306, facilitating separate connection of each of the heat exchangers 312A, 312B and 312C to the TES 306. A potential advantage of having a separate connection for each of the heat exchangers 312A, 312B and 312C is the ability to omit at least one of the heat exchangers, for example, due to maintenance or repairs.

[0279] Referring now to Figure 3F, showing a schematic representation of an exemplary compression subsystem, according to some embodiments of the invention. In some embodiments, the first heat exchanger 312A transfers heat to the second heat exchanger 312B via the conduit 314A. In some embodiments, similarly, the second heat exchanger 312B transfers heat to the third heat exchanger 312C via the conduit 314B. In some embodiments, the third heat exchanger 312C then transfers heat to TES 306 via the conduit 314C. A potential advantage of connecting the heat exchangers 312A, 312B and 312C in a series in terms of heat exchange is that this arrangement can be easily scaled up to include additional heat exchangers.

[0280] Referring now to Figure 3G, showing a schematic representation of an exemplary compression subsystem, according to some embodiments of the invention. In some embodiments, the compression subsystem 300A transfers heat from the gases 302B, 302C, and 302D which are compressed, directly to the TES 306.

[0281] In some embodiments, the gases 302B, 302C and 302D come into direct contact with the TES 306. Potential advantages of this arrangement are preventing heat losses by minimizing the number of occurrences of heat transfer and / or enabling a simple design of the compression subsystem 300A.

[0282] In some embodiments, the gas 302B flows from the first compressor 310A to the TES 306 via the second connector 308B. In some embodiments, after contacting the TES 306 and transferring heat to the TES 306, the gas 302B, having been cooled, then flows to the second compressor 310B via the third connector 308C.

[0283] In some embodiments, the gas 302C then flows from the second compressor 310B to the TES 306 via the fourth connector 308D. In some embodiments, after contacting the TES 306 andtransferring heat to the TES 306, the gas 302B, having been cooled, then flows to the fourth compressor 310D via the fifth connector 308E.

[0284] In some embodiments, the gas 302D then flows from the third compressor 310C to the TES 306 via the sixth connector 308F. In some embodiments, after contacting the TES 306 and transferring heat to the TES 306, the gas 302D, having been cooled, then flows to the compressed gas storage unit 304 via the seventh connector 308G.

[0285]

[0286] Referring now to Figure 3H, showing a schematic representation of an exemplary compression subsystem, according to some embodiments of the invention. In some embodiments, the TES 306 comprises the following: Zone 1 chamber 306A, Zone 2 chamber 306B, and a Zone 3 chamber 306C.

[0287] In some embodiments, each of the Zone 1 chamber 306A, Zone 2 chamber 306B and Zone 3 chamber 306C is designed to operate at a different temperature range, such that heat is transferred at each stage according to a thermal gradient between the compressed gas and the storage zone.

[0288] In some embodiments, the temperature of the gases 302B, 302C and 302D increases after compression. In some embodiments, the TES 306 is configured to direct the flow of any of the gases 302B, 302C and 302D after compression, sequentially through the Zone 3 chamber 306C, the Zone 2 chamber 306B, and the Zone 1 chamber 306A. In some embodiments, heat from any of the gases 302B, 302C and 302D is transferred primarily to the Zone 3 chamber 306C when the temperature is at its highest, then to the Zone 2 chamber 306B as the temperature decreases, and finally to the Zone 1 chamber 306 A with the remaining lower- temperature energy.

[0289] A potential advantage of direct the flow the gases 302B, 302C and 302D after compression, sequentially through the Zone 3 chamber 306C, the Zone 2 chamber 306B, and the Zone 1 chamber 306A is maximizing energy capture from the gases 302B, 302C and 302D, by ensuring that heat is transferred efficiently at each stage. The highest-temperature gas transfers its heat to the Zone 3 chamber 306C, where the largest thermal gradient exists, enabling optimal energy absorption.

[0290] Exemplary configurations of generation subsystems

[0291] Referring now to Figure 31, showing a schematic representation of an exemplary generation subsystem, according to some embodiments of the invention. In some embodiments, each of the conduits 320A, 320B and 320C are connected directly to the TES 306, facilitating separate connection of each of the heat exchangers 312D, 312E and 312F to the TES 306. A potential advantage of having a separate connection of the each of the each of the heat exchangers 312D, 312E and 312F is the ability to omit at least one of the heat exchangers, for example due to maintenance or repairs.Referring now to Figure 3 J, showing a schematic representation of an exemplary generation subsystem, according to some embodiments of the invention. In some embodiments, the TES 306 directly transfers heat to the gases 302E, 302F, and 302G which are expanded.

[0292] In some embodiments, the gases 302D, 302E and 302F, prior to entering the first turbine 318A, the second turbine 318B and the third turbine 318C respectfully, come into direct contact with the TES 306 for heating the gases. Potential advantages of this arrangement are preventing heat losses by minimizing the number of occurrences of heat transfer and enabling a simple design of the generation subsystem 300B.

[0293] In some embodiments, the gas 302D flows to the TES 306 from the compressed gas storage unit 304 via the eighth connector 308H. In some embodiments, after contacting the TES 306 and absorbing heat from the TES 306, the gas 302D having been heated then flows to the first turbine 318A via the ninth connector 3081.

[0294] In some embodiments, the gas 302E flows to the TES 306 via the tenth connector 308J. In some embodiments, after contacting the TES 306 and absorbing heat from the TES 306, the gas 302E flows to the second turbine 318B via the eleventh connector 308K.

[0295] In some embodiments, the gas 302F then flows to the TES 306 via the twelfth connector 308L. In some embodiments, after contacting the TES 306 and absorbing heat from the TES 306, the gas 302F having been heated then flows to the third turbine 318B via the thirteenth connector 308M.

[0296] In some embodiments, the gas 302G then flows to an outlet (not shown in Figure 31) via the fourteenth connector 308N.

[0297] Exemplary Configuration of a Generation Subsystem with Zonal Thermal Energy

[0298] Referring now to Figure 3K, showing a schematic representation of an exemplary generation subsystem, according to some embodiments of the invention. In some embodiments, the TES 306 is configured to direct the flow of any of the gases 302D, 302E, and 302F sequentially through the Zone 1 chamber 306A, the Zone 2 chamber 306B, and the Zone 3 chamber 306C. In some embodiments, any of the gases 302D, 302E, and 302F absorbs heat first from the Zone 1 chamber 306A when the temperature of any of the gases 302D, 302E, and 302F is at its lowest, then from the Zone 2 chamber 306B as the temperature of any of the gases 302D, 302E, and 302F increases, and finally from the Zone 3 chamber 306C when the temperature of any of the gases 302D, 302E, and 302F reaches its highest.

[0299] A potential advantage of directing the flow of the gas sequentially through the Zone 1 chamber 306A, the Zone 2 chamber 306B, and the Zone 3 chamber 306C is maximizing the efficiency of heat transfer to the gas, by allowing the gas to absorb heat progressively as it moves through the chambers.The low-temperature gas absorbs heat from the Zone 1 chamber 306A, where the largest thermal gradient exists initially, followed by absorption from the Zone 2 chamber 306B and finally from the Zone 3 chamber 306C, enabling the gas to transfer heat efficiently.

[0300] Exemplary Configuration of a Generation Subsystem with combined heat sources: TES and environment heat source

[0301] Referring now to Figure 3L, showing a schematic representation of an exemplary generation subsystem comprising an environment heat source, according to some embodiments of the invention. In some embodiments, the generation subsystem 300B comprises an environment heat source 326. In some embodiments, the environment heat source 326 utilizes heat emitted during industrial processes, for example a steel manufacturing plant, or a nuclear facility. In some embodiments, the environment heat source 326 utilizes heat from geothermal activity, or heat from the surrounding waterbody.

[0302] In some embodiments, the environment heat source 326 provides heat via the conduit 320B to the compressed gas before it is allowed to expand in the turbine 318B, by transferring to the fifth heat exchanger 312E.

[0303] A potential advantage of the environment heat source 326 is increasing the RTE of the work extraction process by using heat from the environment.

[0304] Referring now to Figure 3M, showing a schematic representation of an exemplary generation subsystem comprising an environment heat source, according to some embodiments of the invention. In some embodiments, each of the fourth, fifth, and sixth heat exchangers 312D, 312E, and 312F is further connected to the environment heat source 326 via heat transmitting conduits 328A, 328B, and 328C respectfully.

[0305] In some embodiments, a controller (not shown in Figure 3M) is operatively connected to the fourth, fifth, and sixth heat exchangers 312D, 312E, and 312F. The controller is configured to selectively direct heat flow from either the TES 306, or from the environment heat source 326, or from both the TES 306 and the environment heat source 326. Tn some embodiments, the controller selectively direct heat flow according a heat optimization algorithm based on real-time measurements of system parameters, for example gas pressure, gas temperature, the TES 306 heat state, and available heat from environment heat source 326, and, in some embodiments, the controller selectively direct heat flow according to instruction from an operator.

[0306] A potential advantage of the controller is improving RTE by maximizing utilization of heat sources.

[0307] It is to be noted that, in some embodiments, at least one heat exchanger of the system (optionally all of them) is dedicated to only one of the subsystems, such that the heat exchanger isused exclusively in the compression subsystem 300A or exclusively in the generation subsystem 300B, as shown, for example, in Figure 3 A.

[0308] In other embodiments, at least one heat exchanger is shared between the compression subsystem 300A and the generation subsystem 300B. Optionally, all of the heat exchangers are shared between the compression subsystem 300A and the generation subsystem 300B, for example, as shown in Figures 15A-C. A potential advantage of such sharing is cost savings, for example, by reducing the number of heat exchangers, reducing installation and / or maintenance requirements. It is to be noted, however, that in some embodiments only a portion of the heat exchangers are shared, while one or more heat exchangers remain dedicated exclusively to either the compression subsystem or the generation subsystem.

[0309] Exemplary Open Compressed Gas Energy Storage and work Extraction System (Air Intake and Release to Environment)

[0310] Referring now to Figure 4A, showing a schematic representation of an exemplary system for storing energy and extracting work from the energy in a compressed gas energy storage system, according to some embodiments of the invention. In some embodiments, the system 400 uses gas 402. Arrows 404A, 404B, and 404C indicate the direction of gas flow in the system 400. In some embodiments, the gas 402 enters the system 400 via a gas inlet 406. In some embodiments, the gas 402 is ambient air from the surrounding environment. In some embodiments, the gas 402 is compressed in a compressor 408, and then flows via a first connector 410, for example, a pipe or conduit, to a compression heat exchanger 412.

[0311] In some embodiments, the compression heat exchanger 412 transfers heat from the gas 402 after compression via a heat conductor 414 to a TES 416. In some embodiments, the TES 416 is configured to store heat. In some embodiments, the gas 402 then flows via a second connector 418 to a compressed gas storage tank 420, where the gas 402 in a compressed state is stored.

[0312] Tn some embodiments, the compressed gas storage tank 420 is positioned inside a waterbody 422. Optionally, the compressed gas storage tank 420 comprises a water opening 424, which allows water from the waterbody 422 to enter the compressed gas storage tank 420, the water exerting a pressure which counterbalances the pressure of the gas 402 in a compressed state.

[0313] In some embodiments, upon demand, the gas 402 is released from the compressed gas storage tank 420 via a third connector 426 and allowed to expand in a first turbine 428.

[0314] In some embodiments, the gas 402 after having been expanded in the first turbine 428 and thereby cooled, is then released to a fourth connector 430. In some embodiments, the fourth connector 430 is configured to allow the gas 402 to absorb heat from the waterbody 422, such that the fourth connector 430 acts as a heat exchanger, for example the fourth connector 430 is sufficiently long suchthat in the time it takes the gas 402 to flow from the compressed gas storage tank 420 to a generation heat exchanger 432, the gas reaches thermal equilibrium or near thermal equilibrium with the waterbody 422. A potential advantage of the fourth connector 430 being configured to allow the gas 402 to absorb heat from the waterbody 422 is enabling passive heat transfer from the waterbody 422, enhancing the overall efficiency of the system. Alternatively, the gas 402 after being released from the compressed gas storage tank 420, is stored in a secondary gas storage tank for allowing the gas 402 to absorb heat from the waterbody 422, for example, as shown in Figures 4B and 4D.

[0315] In some embodiments, the generation heat exchanger 432 transfers heat from the TES 416, via a heat conductor 434 to the gas 402. In some embodiments, the gas 402 having been heated, then flows via a fifth connector 438 to a second turbine 438, where the gas 402 is allowed to expand. In some embodiments, the gas 402 after having been expanded in the second turbine 438 is then allowed to exit the system 400 to the surrounding environment, via a gas outlet 440.

[0316] In some embodiments, the TES 416 is positioned outside the water body 422. Potential advantages of positioning the TES 416 outside the water body 422 are high accessibility, for example, for repairs and maintenance, and prevention of heat loss to the surrounding environment due to the lower thermal conductivity of the air compared to water.

[0317] Referring now to Figure 4B, showing a schematic representation of an exemplary system for storing energy and extracting work from the energy in a compressed gas energy storage system, according to some embodiments of the invention. In some embodiments, the system 400 comprises a secondary gas storage tank 442 which receives the gas 402 after having been released from the first turbine 428. In some embodiments, the secondary gas storage tank 442 temporarily stores the gas 402, the gas 402 being at a pressure which is lower than the pressure of the gas 402 when stored in the gas storage tank 420. In some embodiments, the secondary gas storage tank 442 has a larger volume compared to the compressed gas storage tank 420. In some embodiments, the secondary gas storage tank 442 is configured for allowing the gas 402 to absorb heat from the waterbody 422.

[0318] Exemplary Closed-Loop Compressed Gas Energy Storage and Work Extraction System Referring now to Figure 4C, showing a schematic representation of an exemplary system for storing energy and extracting work from the energy in a compressed gas energy storage system, according to some embodiments of the invention. In some embodiments, the gas 402 is cycled in a system 450. Potential advantages of cycling gas in the system 450 are as follows:

[0319] 1. Enhancing the reliability of the system 450 by using the gas 402 having the same properties in each cycle;2. Eliminating the need for filtering the gas 402 from contaminants, for example, water vapor.

[0320] 3. Enabling the use of gases, for example carbon dioxide (CO2) which liquefy under the pressure and temperature conditions created by the compressor 408. This liquefaction significantly increases the storage capacity of the compressed gas storage tank 420. In some embodiments, the conditions of the deep-sea environments (e.g., temperature and pressure in) of the compressed gas storage tank 420 naturally support the liquefaction of CO2, in accordance with the phase diagram of CO2.

[0321] 4. Enabling the use of gases, for example carbon dioxide (CO2), which liquefy under the pressure and temperature conditions created by the compressor 408.

[0322] 5. Increasing the storage capacity of the compressed gas storage tank 420 when the gas is stored in liquid form, enabling the containment of a greater mass of gas.

[0323] 6. Utilizing the conditions of the deep-sea environment (e.g., temperature and pressure) of the compressed gas storage tank 420 to naturally support the liquefaction of CO2, in accordance with the phase diagram of CO2.

[0324] 7. Increasing the RTE of the process by allowing the liquefied gas, during its flow toward shore and exposure to increasing seawater temperatures, to change from liquid to gas, absorbing heat from the outside water environment.

[0325] In some embodiments, a gas reservoir 444 stores the gas 402 after expansion in the second turbine 438 and / or before compression in the compressor 408. The gas reservoir 444 is configured for allowing the gas 402 to enter and exit the gas reservoir 444, for example as shown and further explained in relation to Figures 4E and 4F.

[0326] In some embodiments, the gas 402 stored in the gas reservoir 444 is CO2 which has the potential advantage of increasing the amount of heat harvested from the gas 402 after compression, due to the high latent heat which is released during phase transition from gas to liquid.

[0327] Referring now to Figure 4D, showing a schematic representation of an exemplary system for storing energy and extracting work from the energy in a compressed gas energy storage system, according to some embodiments of the invention. In some embodiments, the system 450 comprises the secondary gas storage tank 442.

[0328] Exemplary gas reservoirs for a system which cycles gas

[0329] Referring now to Figure 4E, showing a schematic representation of an exemplary gas reservoir in a system which cycles gas, according to some embodiments of the invention.In some embodiments, the gas reservoir 444 has a volume which is greater than a volume of the compressed gas storage tank 420, for allowing the gas 402 to decrease in pressure, for example, reaching a pressure of latm. The gas reservoir 444 has a volume, for example, from about 10 times to 300 times the volume of the compressed gas storage tank 420, optionally from 100 times to 700 times, optionally from 500 times to 1500 times.

[0330] In some embodiments, the gas reservoir 444 comprises a piston 446. In some embodiments, the gas 402 enters the gas reservoir 444, causing the piston to move, thereby increasing the volume of an adjustable portion of the gas reservoir 444, which is allocated for storing the gas 402. The total external volume of the gas reservoir 444 remains fixed while only the partitioned internal volume changes dynamically. In some embodiments, the gas 402 exerts pressure on the piston 446, causing the piston 446 to move and, in some embodiments, the piston 446 is moveable by an electric engine (not shown in figure 4E).

[0331] In some embodiments, a filler gas 448 initially occupies the gas reservoir 444 before the entry of the gas 402. A potential advantage of having the filler gas 448 initially occupy the gas reservoir 444 is maintaining internal pressure and provide structural support before the entry of gas 402. Optionally, the gas reservoir 444 comprises an opening (not shown in figure 4E) which allows the filler gas 448 to exit as the gas 402 enters. Optionally, a pump (not shown in figure 4E) is used to remove the filler gas 448.

[0332] Referring now to Figure 4F, showing a schematic representation of an exemplary gas reservoir in a system which cycles gas, according to some embodiments of the invention.

[0333] In some embodiments, the gas 402 has a different density compared to the filler gas 448. A potential advantage of the gas 402 and the filler gas 448 having different densities is preventing mixing thereby allowing the selective removal of the filler gas 448 from the gas reservoir 444. In some embodiments, the different density results from difference in the temperatures of the gas 402 and the filler gas 448.

[0334] Optionally, one or more filters 449 allow removal of the filler gas 448 from the gas reservoir 444.

[0335] Alternatively, the gas reservoir 444 is made of a flexible material, for example rubber, polyurethane and polyethylene (PE), allowing the gas reservoir 444 to expand or compress to accommodate the volume change of the gas 402. Potential advantages of the gas reservoir 444 being made of a flexible material are efficient space utilization and reducing the risk of overpressure or under-pressure which may lead to ruptures in the gas reservoir 444.thermal

[0336] Referring now to Figure 5A, showing a schematic representation of an exemplary thermal energy storage, according to some embodiments of the invention.

[0337] The composition of a TES 500 which stores and allow transfer of heat, is influenced by several factors. One key factor is the thermal properties of the materials used, such as specific heat capacity and thermal conductivity. Materials with high specific heat capacity can store more heat energy per unit mass, while those with high thermal conductivity allow for efficient heat transfer within the storage medium. The stability and durability of the materials are also crucial, as the heat storage device must withstand numerous heating and cooling cycles without degrading in performance.

[0338] The present inventors have found that it is beneficial to use a composite material comprising one or more materials with high specific heat capacity and one or more materials with high thermal conductivity.

[0339] In some embodiments, the TES 500 is made of a composite material 502. In some embodiments, the composite material 502 comprises a matrix 504 and one or more fillers 506.

[0340] In some embodiments, the matrix 504 is a high thermal conductivity material, for example, Aluminum, Copper, oil or dispersion of carbon particles in oil, and the one or more fillers 506 are made of high specific heat capacity, for example clay, sand, gravel, quartz, phase change materials (PCMs) or combination of the materials. A potential advantage of the TES 500 comprising a matrix 504 made of high thermal conductivity material and the one or more fillers 506 are made of high specific heat capacity is uniform heat distribution throughout the TES 500, preventing localized hot spots and ensuring even heat dissipation.

[0341] In some embodiments, the composite material 502 is manufactured by casting a melt of the high thermal conductivity material, for example Aluminum onto the one or more fillers 506, for example rocks, gravel and / or salt granules.

[0342] Tn some embodiments, the matrix 504 is a high specific heat capacity material, for example, water, PCMs, concrete, clay, salt hydrates, silica gel or combination of the materials, and the one or more fillers 506 are made of high thermal conductivity material, for example Aluminum particles, Copper particles, carbon particles, diamond particles or combination of the materials.

[0343] In some embodiments, the composite material 502 comprises a high thermal conductivity material arranged in a 2D or 3D network (not shown in Figure 5A), for example a metal mesh, embedded within the matrix 504 which is made of a high specific heat capacity material. A potential advantage of the high thermal conductivity material arranged in a 2D or 3D is enabling a rapid and efficient heat transfer across the composite material 502, promoting a more uniform heat distribution and minimizing thermal gradients.Referring now to Figure 5B, showing a schematic representation of an exemplary composite material for thermal energy storage, according to some embodiments of the invention. In some embodiments, the composite material 502 is made of two or more bulk elements 508 separated by an intermediate 510. In some embodiments, the two or more bulk elements 508 are made of a solid material having high specific heat capacity, for example concrete or clay. In some embodiments, the intermediate 510 is made of a high thermal conductivity material, for example Aluminum.

[0344] Referring now to Figure 5C, showing a schematic representation of an exemplary TES system, according to some embodiments of the invention. In some embodiments, the TES 500 comprises a pressure tank 512 that holds a working fluid 514, for example water. When the working fluid 514 is heated, the working fluid 514 vaporizes, storing thermal energy in the form of latent heat. In some embodiments, the pressure tank 512 is at least partially immersed within a medium 516. In some embodiments, the medium 516 can be made of high specific heat capacity materials, like concrete or clay, which absorb and store significant amounts of heat, helping to maintain the temperature of the vaporized liquid over time. Alternatively or additionally, the medium 516 can be made of high thermal conductivity materials, such as aluminum, which facilitate rapid heat transfer.

[0345] Referring now to Figure 5D, showing a schematic representation of an exemplary TES system, according to some embodiments of the invention. In some embodiments, a high liquid phase TES 550 comprises water 518 maintained in a liquid phase at a high temperature, for example from 90 °C to 150 °C, optionally from 120 °C to 250 °C, optionally from 200 °C to 350 °C. A gas 520, for example compressed air, is maintained above the water 518 at a pressure greater than the saturation pressure of the water at the high temperature, preventing the water 518 from boiling and transitioning into steam.

[0346] A potential advantage of preventing the water 518 from boiling and transitioning into steam is avoiding safety hazards associated with uncontrolled boiling, such as sudden pressure surges, mechanical stress on the container, and the risk of steam release.

[0347] In some embodiments, during energy generation, the water 518 are transferred via a conduit 522 to be used for heating compressed gas before it is allowed to expand in the turbine. In some embodiments, the water 518 after having been cooled is then stored, and transferred to be heated by absorbing heat from the compressed gas.

[0348] In some embodiments, the water 518 after having been heated is maintained above the water 518 at a pressure greater than the saturation pressure of the water by allowing compressed gas via a conduit 524 to reach the water 518.

[0349] Referring now to Figure 5E, showing a schematic representation of an exemplary TES system, according to some embodiments of the invention. In some embodiments, one or more heat conductors524 is embedded within the TES 500. In some embodiments, the one or more heat conductors 524 are made of a high thermal conductivity material, for example aluminum, stainless steel and graphite In some embodiments, the one or more heat conductors 524 are conduits which allow a heat transfer fluid to circulate, thereby moving heat from one location to another location, for example from the compressed gas to the TES 500. In some embodiments, the heat transfer fluid is, for example oil, water or Glycol or other fluid providing stable performance under the required operating temperatures. A potential advantage of the conduits which allow a fluid to circulate is avoiding the need to directly circulate the gas to transfer its heat, minimizing potential pressure loss.

[0350] Alternatively or additionally, the one or more heat conductors 524 are pipes which direct gas from a compressor to the TES 500 and / or from the TES 500 to a turbine, allowing the gas to make direct or indirect contact with the TES 500, thereby allowing direct transferring heat.

[0351] A potential advantage of the one or more heat conductors 524 embedded within the TES 500 is effective heat transfer to and from the TES 500.

[0352] In some embodiments, the TES 500 is made of one or more molten salts, for example inorganic salts such as sodium nitrate, potassium nitrate, and calcium nitrate.

[0353] In some embodiments, the TES 500 is made of one or more PCMs, absorbing and releasing thermal energy during the process of changing their physical state (phase) for example, from solid to liquid and vice versa.

[0354] In some embodiments, the TES 500 utilizes thermochemical heat storage, releasing or absorbing thermal energy through reversible chemical reactions.

[0355] In some embodiments, the TES 500 utilizes mechanical-thermal heat storage, storing thermal energy using mechanical processes.

[0356] Exemplary method for maintaining a temperature of a thermal energy storage

[0357] In some embodiments, it is desired to prevent temperature decrease, or optionally to increase the temperature of a TES. Tn some embodiments, the temperature is from about 50°C to 500°C, optionally from about 100°C to 600°C, optionally from about 700°C to 1200°C.

[0358] Referring now to Figure 6, showing a flowchart of an exemplary method for heating a TES for preventing temperature decrease.

[0359] The method of Figure 6 includes:

[0360] 1. providing a TES having a TES temperature (602);

[0361] 2. optionally, providing temperature sensors (604);

[0362] 3. optionally, monitoring the TES temperature (606);

[0363] In some embodiments, the TES temperature is continuously monitored using the temperature sensors.4. providing a heat source (608);

[0364] In some embodiments, the heat source is an electricity-powered heater. In some embodiments, the electricity for the electricity-powered heater is generated using green energy, such as solar energy or wave energy, during periods of high availability. Optionally, the electricity is sourced from the power grid during times when electricity costs are lower.

[0365] In some embodiments, the heat source utilizes heat from the sun. In some embodiments, the heat source is one or more dark panels which absorb heat from the sun and in some embodiments, the heat source is a working fluid which absorb heat from the sun, for example oil.

[0366] 5. heating the TES (610).

[0367] Optionally, the TES is heated in response to the TES temperature which is monitored. In some embodiments, when a decrease in the TES temperature is detected by the temperature sensors, the TES is heated.

[0368] In some embodiments, the TES is heated by the heat source directly contacting the TES and, in some embodiments, one or more thermal conducting connectors transfer heat from the heat source to the TES.

[0369] Exemplary system for preventing heat loss from a thermal energy storage

[0370] Referring now to Figure 7, showing a schematic representation of a cross section of an exemplary thermal energy storage heating system, according to some embodiments of the invention.

[0371] In some embodiments, preventing heat loss from the TES 500 to a surrounding environment is desired to prevent temperature decrease of the TES 500.

[0372] In some embodiments, heat loss from the TES 500 to a surrounding environment is minimized by reducing a differentiation between a temperature of an inner portion of the TES 500 and a temperature of a TES outer surface of the TES 500.

[0373] In some embodiments, a system 700 is designed to heat the outer surface of the TES 500. In some embodiments, the system 700 comprises a channel 702 that surrounds the outer surface of the TES 500. In some embodiments, a fluid (not shown in Figure 7) is introduced into the channel 702 through one or more inlet ports 704, allowing the fluid to circulate around the outer surface or periphery of the TES 500. In some embodiments, as the fluid flows through the channel 702, the fluid transfers heat to the outer surface or periphery of the TES 500, thereby raising their temperature.

[0374] In some embodiments, the fluid is cycled in the channel 702.

[0375] In some embodiments, the fluid is heated in the channel 702.

[0376] In some embodiments, the fluid is heated before entering the channel, and, after the fluid transfers the heat, the fluid exits the channel 702 through one or more outlet ports 706.In some embodiments the fluid is heated with a heat source (not shown in figure 7). In some embodiments, the heat source is an electricity-powered heater. In some embodiments, the electricity for the electricity-powered heater is generated using green energy, such as solar energy or wave energy, during periods of high availability. Optionally, the electricity is sourced from the power grid during times of low demand when electricity costs are lower.

[0377] In some embodiments, the heat source utilizes heat from the sun. In some embodiments, the heat source is one or more dark panels which absorb heat from the sun and in some embodiments, the heat source is a working fluid which absorb heat from the sun, for example oil.

[0378] In some embodiments, the heat source is heat from compressed gas.

[0379] Referring now to Figure 8, showing a flowchart of an exemplary method for preventing ice formation on blades of a turbine.

[0380] The method of Figure 8 includes:

[0381] 1. providing a turbine including turbine blades (802);

[0382] optionally, applying hydrophobic coating on the turbine blades.

[0383] A potential advantage of hydrophobic coating on the turbine blades is preventing water adhesion to the turbine blades and therefore preventing ice formation on the turbine blades. In some embodiments, the hydrophobic coating is made of one or more of: PTFE (Teflon®), FEP, siloxane, PDMS, and / or or polyamide-imide (PAI, commercially available as Torlon®.

[0384] In some embodiments, the heat source is the TES 500 and, in some embodiments, the heat source is an electricity-powered heater. In some embodiments, the electricity for the electricity-powered heater is generated using green energy, such as solar energy or wave energy, during periods of high availability. Optionally, the electricity is sourced from the power grid during times when electricity costs are lower. Optionally, in some embodiments, the heat source is one or more IR lamps.

[0385] 2. optionally, removing moisture from a gas before the gas enters the turbine (804);

[0386] Tn some embodiments, the gas flows via a bed of desiccant material, for example silica gel or activated alumina which adsorbs moisture from the gas.

[0387] In some embodiments, the gas is directed via a membrane which selectively allow water vapor to pass through to an outlet, allowing the dry gas to flow to the turbine.

[0388] In some embodiments, the gas is cooled to condense water vapor into liquid droplets.

[0389] 3. pre-heating the gas entering the turbine with heat from the heat source (806);

[0390] 4. monitoring parameters of the gas with sensors (808);

[0391] In some embodiments, the temperature of the gas is monitored at different locations in the turbine. In some embodiments, the temperature of the gas at the gas inlet of the turbine is measured and monitored.In some embodiments, the flow rate of the gas entering the turbine is monitored.

[0392] In some embodiments, the humidity of the gas is monitored in order to decide when to activate moisture removal.

[0393] 5. optionally, adjusting at least one parameter of the gas in response to the monitoring (810).

[0394] In some embodiments, based on the measured temperature at the gas outlet, if the temperature is determined to be, for example, above 0.5 degrees of a predefined temperature threshold, the flow rate of the gas is reduced and / or heating is initiated or increased, for example the temperature is determined to be 0.5°C.

[0395] Referring now to Figure 9, showing a flowchart of an exemplary method for removing ice crystals formed on blades of a turbine.

[0396] The method of Figure 9 includes:

[0397] 1. providing a turbine including turbine blades (902);

[0398] 2. providing a heat source (904);

[0399] In some embodiments, the heat source is the TES 500 and, in some embodiments, the heat source is an electricity-powered heater. In some embodiments, the electricity for the electricity-powered heater is generated using green energy, such as solar energy or wave energy, during periods of high availability. Optionally, the electricity is sourced from the power grid during times of low demand when electricity costs are lower.

[0400] 3. providing sensors for detecting ice crystals formation on the turbine blades (906);

[0401] In some embodiments, the sensors for detecting ice crystals formation on the turbine blades are one or more of: optical, capacitive, thermal, or acoustic sensors.

[0402] 4. monitoring formation of ice crystals on the turbine blades (908);

[0403] In some embodiments, the monitoring formation of ice crystals on the turbine blades comprises measuring a temperature of the gas after expansion in the turbine.

[0404] 5. are ice crystals detected on the turbine blades? (910);

[0405] if no, go back to 908, if yes, continue to 912:

[0406] 6. heating the gas entering the turbine using the heat source (912).

[0407] optionally, heating the turbine blades.

[0408] Exemplary system which manages thermal storage liquid storing at different temperatures As explained herein elsewhere, in the process of compressing air, a lot of heat is created. It would be advantageous to store that heat in order to allow using that stored heat later, for example during decompression of air, thereby providing a more energetically efficient process.

[0409] In some embodiments, also as explained herein elsewhere, a dedicated thermal energy storage (TES) system is used in concomitance with an air compression / storage / decompression system, inorder to harvest heat from the compression process and using the stored heat during the decompression process, thereby providing a more energetically efficient process.

[0410] In some embodiments, the TES comprises a separate hot storage tank and cold storage tank .In some embodiments, thermal energy storage is performed using water as the thermal storage medium. Typically, hot water storage tanks and / or the piping associated therewith are maintained at high pressure, thereby preventing the hot water contained therein from boiling. The hot water flows through pressure-rated conduits and into storage tanks capable of storing liquid under pressure, where the water is accumulated under compressed air. The internal pressure may be controlled by regulating the introduction and discharge of compressed air, and the heated water is maintained under such controlled conditions until the time when the turboexpander is activated. After transferring its heat, the water continues toward one or more cold-water storage tanks, which are not necessarily required to withstand high pressure, where the cooled water remains stored for subsequent use in the compression process.

[0411] If it is desired to store the cold water under pressure (in pressure-rated tanks) as well, for example, to potentially reduce energy consumption associated with re-pressurizing the liquid and / or overcoming pressure differentials within the piping network during a subsequent compression cycle, this is feasible; however, such pressure-rated storage tanks are significantly more expensive.

[0412] In some embodiments, the hot storage tanks pressure-rated tanks) are managed such that the same tanks are also selectively usable for storing the cold water at different stages of operation (i.e., not concurrently with hot-water storage). Potentially, such shared use of the hot storage tanks for both hot and cold water may reduce the total number of storage tanks required, for example, by up to about 50%, thereby providing savings in tank cost, construction / installation cost, and facility footprint (e.g., reduced building area and / or required space).

[0413] In some embodiments, more than one storage tank may be maintained substantially empty at a given time in order to allow cooling of a tank between discharge of hot water and subsequent introduction of cold water. In some embodiments, cooling of an emptied tank may be facilitated by selectively opening portions of the thermal insulation (for example, insulation panels or thermal windows) and / or by introducing ambient air into the empty tank to enhance convective cooling.

[0414] Figure 10A shows the two systems: the system 1000 and the compression / storage / decompression system 1002.

[0415] Exemplary compression / storage / decompression systems are explained herein elsewhere, for the present explanations, a simplified version will be used. In some embodiments, the compression / storage / decompression system 1002 comprises: a compressor 1004, a storage for pressured air 1006 (for example, located underwater - as explained herein elsewhere) and aturboexpander 1008, all interconnected by pipes (generally numbered 1010). In some embodiments, the compression / storage / decompression system 1002 comprises dedicated valves 1012 / 1014 configured to be opened or closed strategically during the compression / decompression process in order to guarantee proper redirection of the flow of the air, for example, from the compressor to the storage for pressured air 1006, and from the storage for pressured air 1006 to the turboexpander 1008.

[0416] Figure 10A discloses a schematic representation of a system 1000 configured to: 1. Harvest heat from the act of compressing air; 2. Store the harvested heat; and 3. Deliver the harvested heat when necessary.

[0417] In some embodiments, two systems are required: one that manages the harvesting of heat and another the manages the delivery of heat.

[0418] The inventors have found a novel system that manages to incorporate these two systems into a single, efficient, productive and low-cost system. The principal characteristics of this advantageous system is that it utilizes the same storage containers for storing heated / hot water and for storing cold water (not at the same time); and that at least one of the storage containers is always empty.

[0419] A system that utilizes two separate systems to manage the storage of hot water and to storage cold water are shown in relation to Figures 11A-B.

[0420] The system shown in Figures 10A-C show a specific embodiment where the same storage containers used for storing hot water can be used to store cold water.

[0421] In some embodiments, in general, the system comprises a plurality of storage tanks interconnected by pipes to heat exchangers. In some embodiments, the system comprises a plurality of dedicated valves configured to be strategically opened or closed at very specific times, as will further explained below.

[0422] As mentioned above, one important feature of the system is that at any certain point of the process, at least one storage tank is empty (see below for further explanations).

[0423] Tn order to simplify the explanations, the following system will be used. Tn some embodiments, the system 1000 comprises a closed loop system comprising pumps 1016 / 1018, heat exchangers 1020 / 1022, a plurality of storage containers 1024 / 1026 / 1028 / 1030 / 1032 / 1034, and a plurality of individually controllable valves (from 1036 to 1066). In some embodiments, the whole system is interconnected using a plurality of pipes (generally numbered 1068).

[0424] In a specific embodiment, the heat is stored using water. Therefore, in the following explanations, water will be used as example to store heat. The hot compressed air from the compression passes through a heat exchanger that transfers the heat to the water that enters cold and leaves hot, for example, at a temperature of from about 150 degrees Celsius to about 250 degrees Celsius - for example 200 degrees Celsius.of the and actuation of the parts of the system

[0425] In general, two processes are performed in the system:

[0426] 1. Harvesting of heat from the compression of air using water and storage of the heated water in storage containers.

[0427] 2. Delivery of heated water from the storage containers to heat the air before reaching the turbo expander.

[0428] Harvesting of heat from the compression of air using water and storage of the heated water in storage containers

[0429] Air enters the compressor 1004. Heat is generated in this process. Using a heat exchanger 1020, water is heated.

[0430] The “cold water” (water that has not been heated is referred herein as cold water) comes from one of the storage containers, for the explanations, storage container 1024 has cold water in it.

[0431] In order to deliver cold water from the storage container 1024, pump 1016 is actuated, valve 1062 is opened, valve 1038 of storage container 1024 is opened, valves 1042, 1046, 1050, 1054, 1058 are closed, valve 1060 is closed.

[0432] The pump 1060 brings the cold water from the storage container 1024 into the heat exchanger 1020, where the cold water is heated.

[0433] At this point, the just heated water is stored in an empty storage container, one that is not storage container 1024. The reason that the storage container that is going to receive the heated water is not storage container 1024, is that the heating process can occur while the storage container 1024 has not yet been completely emptied. Therefore, in order to avoid mixing between the cold water and the heated water, the heated water is directed into a different, empty storage container.

[0434] For the explanations, storage container 1024 has cold water in it and storage container 1030 is an empty storage container.

[0435] The below process is schematically shown in Figure 10B.

[0436] The process of harvesting heat will comprise: Activating the air compressor 1004 to begin the process of compressing air. Harvesting the heat generated by the compression process by delivering cold water from storage container 1024 and delivering the heated water into empty storage container 1030.

[0437] During this process: Pump 1016 is actuated. Valve 1062 is opened. Valve 1038 of storage container 1026 is opened. Valves 1042, 1046, 1050, 1054, 1058 are closed. Valve 1064 is opened to allow entry of heated water into the area of the storage containers. Valve 1048 of the empty storagecontainer 1030 is opened to allow entry of heated water into it. Valves 1036, 1040, 1044, 1052, 1056 are closed. Valve 1066 (which allows delivery of heated water to the area of air decompression) is closed. Valve 1060 (which brings recently made cold water from the area of air decompression) is closed.

[0438] Delivery of heated water from the storage containers to the heat the air before reaching the turbo expander

[0439] The air that was compressed by compressor 1004 is delivered into a storage for pressured air 1006, while opening valve 1012 and closing valve 1014. The compressed air stays there until it is needed. At the moment of need, valve 1012 is closed and valve 1014 is opened, allowing the compressed air to exit the storage for pressured air 1006 and reach the turboexpander 1008 in order to generate work / electricity. It is advantageous to increase the temperature of the compressed air before reaching the turboexpander 1008. The compressed air is passed through heat exchanger 1022 before reaching the turboexpander 1008.

[0440] Heated water that was stored in one of the storage containers of the system is used to heat the compressed air.

[0441] For the following explanations, storage container 1028 has heated water in it and storage container 1034 is an empty storage container.

[0442] The below process is schematically shown in Figure 10C.

[0443] The process of delivering heat will comprise: Closing valve 1012. Opening valve 1014 thereby allowing compressed air to exit and reach the heat exchanger 1022. Delivering heat to the compressed air, thereby increasing the temperature of the compressed air, which then reaches the turboexpander 1008 in order to generate work / electricity. The heat used to heat the compressed air comes from heated water that comes from one of the storage containers, for example storage container 1028, reaching the heat exchanger 1022 and heating the compressed air. Then, the now generated cold water is transported into an empty storage container, for example storage container 1034.

[0444] During this process: Pump 1018 is actuated. Valve 1064 is closed. Valve 1044 of storage container 1028 is opened. Valves 1036, 1040, 1048, 1052, 1056) are closed. Valve 1066 is opened to allow entry of heated water into the heat exchanger 1022. Valve 1060 is opened to allow entry of the just generated cold water into the area of the storage compartments. Valve 1062 is closed. Valve 1058 of the empty storage container 1034 is opened to allow entry of cold water into it. Valves 1038, 1042, 1046, 1050, 1054 are closed. Valve 1056 of the empty storage container 1034 is closed. Therefore, storage container 1034 changed from being empty to storing cold water.Again, the reason to bring the cold water into an empty storage container is to avoid mixing cold water and heated water.

[0445] Figures 10D-H schematically shows exemplary cycles of heating water, according to some embodiments of the invention. Storage containers are marked for either comprising cold water (C), hot water (H) or empty (E).

[0446] In Figure 10D, storage tanks 1024, 1026, 1028, 1030 and 1032 comprise cold water and storage tank 1034 is empty. The cold water from storage tank 1024 is passed through the heat exchanger, in which the cold water is heated, and moved into the empty storage tank 1034 - thereby having storage tank 1024 empty, storage tanks 1026, 1028, 1030 and 1032 with cold water and storage tank 1034 with hot water.

[0447] In Figure 10E, the process is repeated by using the cold water from storage tank 1026, heating it, and delivering it into empty storage tank 1024.

[0448] In Figure 10F, the process is repeated by using the cold water from storage tank 1030, heating it, and delivering it into empty storage tank 1026.

[0449] In Figure 10G, the process is repeated by using the cold water from storage tank 1032, heating it, and delivering it into empty storage tank 1030.

[0450] In Figure 10H, the process is repeated by using the cold water from storage tank 1028, heating it, and delivering it into empty storage tank 1032. Thereby having storage tanks 1024, 1026, 1030, 1032 and 1034 with hot water and storage tank 1028 empty.

[0451] As mentioned above, there is always at least one tank empty.

[0452] Figures 10I-M schematically shows exemplary cycles of using the heated water, according to some embodiments of the invention. Storage containers are marked for either comprising cold water (C), hot water (H) or empty (E).

[0453] In Figure 101, storage tanks 1024, 1026, 1030, 1032 and 1034 comprise hot water and storage tank 1028 is empty. The hot water from storage tank 1024 is passed through the heat exchanger 1022, in which the hot water is cooled, and moved into the empty storage tank 1028 - thereby having storage tank 1024 empty, storage tanks 1026, 1030, 1032 and 1034 with hot water and storage tank 1028 with cold water.

[0454] In Figure 10J, the process is repeated by using the hot water from storage tank 1026, cooling it, and delivering it into empty storage tank 1024.

[0455] In Figure 10K, the process is repeated by using the hot water from storage tank 1030, cooling it, and delivering it into empty storage tank 1026.

[0456] In Figure 10L, the process is repeated by using the hot water from storage tank 1032, cooling it, and delivering it into empty storage tank 1030.In Figure 10M, the process is repeated by using the hot water from storage tank 1034, cooling it, and delivering it into empty storage tank 1032. Thereby having storage tanks 1024, 1026, 1028, 1030 and 1032 with cold water and storage tank 1034 empty.

[0457] As mentioned above, there is always at least one tank empty.

[0458] General additional characteristics of the system

[0459] The hot water is moved and stored within the system using pipes and storage tanks configured to withstand high pressures - meaning the heated water is moved and stored at high pressures. In some embodiments, the hot water is moved and stored so as to avoid boiling of the hot water.

[0460] The hot water is stored in the storage tanks under pressure, under compressed air. The pressure, insertion of air and extraction of air of the compressed air in the storage tank is actively monitored and controlled. In some embodiments, the compressed gas is delivered from a separated and dedicated system.

[0461] As mentioned above, the water is stored under compressed air, where the pressure and the introduction and removal of air is monitored and controlled. When the turboexpander is activated to generate electricity, the valves of the system are closed or opened to allow delivery of heated water into the heat exchanger that deliver heat to the compressed air that will activate the turboexpander.

[0462] It should be noted that cold water stored in the storage containers do not require to be stored under pressure.

[0463] In some embodiments, where necessary and possible, one-way valves can be placed on the pipes to maintain flow in the required directions (not shown).

[0464] In some embodiments, it is possible to keep the cold water under pressure if wanted, in order to save energy during compression and the pressure increase in the pipes.

[0465] In some embodiments, there are several empty storage containers to allow them to cool between the heated water leaving and the cold water entering by opening insulated windows or circulating ambient air inside the empty tank to cool it (not shown).

[0466] In some embodiments, the system configured to harvest heat and deliver heat is an independent system, for example, not connected to a compression / storage / decompression system, but to a different system.

[0467] Exemplary system for compressing gas, storing the compressed gas in an underwater storage tank, and work from the

[0468] Referring now to Figure 11 A, showing a schematic representation of an exemplary system 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 embodimentsof the invention. In some embodiments, a system 1100 comprises an electrical connection 1102, which provides a connection to an electrical power grid 1104. In some embodiments, the electrical power grid 1104 supplies electrical power during energy surplus. In some embodiments, a compressor assembly 1106 is configured to receive electrical power from the electrical connection 1102 and to compress gas. In some embodiments, the compressor assembly 1106 comprises a plurality of compressors which compress the gas in a multi-stage compression, for example, as shown in Figure 11B.

[0469] Optionally, 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 or coal power station is that such stations often have a slow response to a sudden increase (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.

[0470] 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.

[0471] When there is a need to energy, a turboexpander 1108 is configured to receive compressed gas and allow the gas to expand, converting pressure energy into work.

[0472] In some embodiments, the turboexpander 1108 comprises a plurality of turboexpander which allow the gas to expand in a multi-stage, for example as shown in Figure 1 IB.

[0473] In some embodiments, after compression, the compressed gas flows through a one or more gas pipes 1110 to one or more underwater storage tanks 1112 located below sea level 1114 and on the seabed 1115. In some embodiments, one or more underwater storage tanks 1112 are open to ambient water at their lower portion such that the ambient water exert hydrostatic pressure on thepressure gas, such that the one or more underwater storage tanks 1112 are configured for withstanding lower pressures compared to closed tanks for storing compressed gas on the land, for example as described in U.S. Provisional Patent Application No. 63 / 762,182, and for example as shown in Figures 13A-C.

[0474] The one or more underwater storage tanks 1112 are positioned on in 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.

[0475] In some embodiments, the one or more underwater storage tanks 1112 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 1112 are one or more clusters of tubular structures, for example as shown in figure 1 IB.

[0476] In some embodiments, as will be further discussed below, 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.

[0477] In some embodiments, the system 1100 further comprises a compression heat exchanger 1116 arranged downstream of the compressor assembly 1106. The compression heat exchanger 1116 transfers heat from the compressed gas to a thermal storage liquid, which circulates through one or more conduits 1118. The heated thermal storage liquid is thereby stored in a hot storage tank 1120 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.

[0478] When there is a need for energy, compressed gas flows from the one or more underwater storage tanks 1112 through the one or more gas pipes 1110 to a pre-expansion heat exchanger 1122.

[0479] The pre-expansion heat exchanger 1122 transfers heat to the compressed gas from the hot thermal storage liquid drawn from the hot storage tank 1120 of the TES, potentially increasing the RTE of the work extraction process. The compressed gas is then allowed to expand in the turboexpander 1108, which in some embodiments is used to generate electricity which supplied to the electricalpower grid 1104. After the thermal storage liquid has transferred heat, the cooled thermal storage liquid is returned via the one or more conduits 1118 to the cold storage container 1142.

[0480] In some embodiments, when the compressor assembly 1106 compresses gas, the cooled thermal storage liquid in the cold storage tank 1142 is circulated back through the compression heat exchanger 1116 to absorb heat and is circulated to the hot storage tank 1120 of the TES.

[0481] In some embodiments, the system 1100 further comprises a controller 1126, which controls, all the elements of the system (valves, pumps, compressor, etc.), for example, valves 1128A and 1128B via communication cable 1130.

[0482] In some embodiments, the controller 1126 is configured to control the release of compressed gas from the one or more underwater storage tanks 1112 into the turboexpander 1108, and the reception and storage of compressed gas generated by the compressor assembly 1106.

[0483] In some embodiments, when it is desired to store energy, for example when a surplus electricity is available on the power grid 1104, the controller 1126 instructs valve 1128A to open, thereby allowing the compressor assembly 1106 to receive electrical power from the grid 1104 via electrical connection 1102, and compress gas. Conversely, in some embodiments, when it is desired to produce electricity, for example, during periods of increased energy demand, the controller 1126 commands valve 1128B to open, releasing compressed gas from the one or more underwater storage tanks 1112 through the heat exchanger 1108 and into the turboexpander 1108, generating electricity, for example the electricity is supplied to the power grid 1104, or to a user.

[0484] In some embodiments, only the one or more underwater storage tanks 1112 are positioned underwater, while the remainder of the system 1100 is located on land, or alternatively on a floating barge above the sea. As used herein, the term “land” means an offshore platform, for example, a converted drilling rig.

[0485] Referring now to Figure 1 IB, 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 1150 comprises compressors 1132A-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 1132A-C via the electrical connection 1102 such that the compressors 1132A-C compresses gas, and a corresponding heat exchanger 1134A-C transfer heat to the TES by thermal storage liquid which is circulated in the one or more conduits 1118.In some embodiments, the system 1150 expands the compressed gas in a multi stage expansion via the turboexpanders 1136A-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 1136A-C by absorbing heat from the hot thermal storage liquid via a corresponding heat exchanger 1138A-C. The turboexpanders 1136A-C generate electricity, which is transferred via an electrical connection 1140, optionally to an energy storage unit.

[0486] In some embodiments, the thermal storage liquid, having been cooled, then circulated to the cold storage tank (not shown - in Figure 1 lb a general square showing storage tanks is shown), where it is stored.

[0487] In some embodiments, the compressed gas after being compressed by the compressors 1132A-C is stored in a plurality of clusters of tubular structures, for example as described in U.S. Provisional Patent Application No. 63 / 762,182, or in one or more elongated storage conduits, for example, as shown in Figures 13A-C.

[0488] Exemplary Depth-Based Heat Requirement Determination

[0489] In some embodiments, system further comprises a controller configured to determine heat requirements for heating the compressed gas prior to expansion based on a depth of the one or more underwater compressed gas storage tanks, and / or to selectively control heat transfer from the TES assembly and / or via the at least one environmental heat exchanger.

[0490] In some embodiments, the depth of the one or more underwater compressed gas storage tanks determines a hydrostatic pressure acting on the stored compressed gas. The controller may determine the storage pressure based on the depth in the waterbody, for example using known hydrostatic relationships. By way of non-limiting example, the hydrostatic pressure may be approximated according to:

[0491] P ~ Po + p g h

[0492] where Po is atmospheric pressure at the water surface, p is the density of the water, g is gravitational acceleration, and h is the storage depth.

[0493] Based on the determined storage pressure and / or an expected expansion ratio, the controller may estimate a temperature of the compressed gas following expansion in a turboexpander. By way of non-limiting example, the temperature after expansion may be estimated using an isentropic relationship such as:

[0494] T2~ TI (P2 / PI)A( (k-l) / k)

[0495] where Ti and Pi are inlet temperature and pressure, T2and P2are outlet temperature and pressure, and k is the specific heat ratio of the gas.In some embodiments, the controller determines the heat requirements for heating the compressed gas prior to expansion by calculating a required temperature increase of the compressed gas such that a desired turbine inlet temperature and / or turbine outlet temperature is achieved.

[0496] In some embodiments, the controller is configured to selectively control heat transfer from the TES assembly and / or via the at least one environmental heat exchanger in response to the determined heat requirements.

[0497] In some embodiments, the controller selectively activates, modulates, or prioritizes heat transfer from:

[0498] (i) the TES assembly,

[0499] (ii) the at least one environmental heat exchanger positioned in the waterbody, and / or (iii) a combination thereof,

[0500] based on the depth of the underwater compressed gas storage tanks and corresponding thermodynamic conditions.

[0501] In some embodiments, the controller may further take into account a temperature of the waterbody at the depth of the one or more underwater compressed gas storage tanks when determining the heat requirements.

[0502] In some embodiments, determining the heat requirements includes calculating a temperature difference between:

[0503] (i) a predicted gas temperature after expansion, and

[0504] (ii) a target minimum temperature for preventing icing and / or optimizing turbine efficiency. In some embodiments, selectively controlling heat transfer includes controlling one or more flow control elements, including valves, pumps, or combinations thereof, to regulate a flow rate of thermal storage liquid and / or heat exchange fluid through the TES assembly and / or the at least one environmental heat exchanger.

[0505] Referring now to Figures 12A-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 1200 comprises one or more storage conduits 1202 configured to store compressed gas underwater, for example, the one or more underwater storage tanks 1112. In some embodiments, the one or more storage conduits 1202 are positioned on a seabed 1204.

[0506] In some embodiments, one or more water openings 1206 are positioned at a distal and / or lower portion of the one or more storage conduits 1202, configured to allow water to enter and exit the one or more storage conduits 1202 as compressed gas is respectively introduced into or released from the one or more storage conduits 1202.In some embodiments, one or more gas conduits 1208 are connected to the one or more storage conduits 1202, the one or more gas conduits 1208 being configured to deliver compressed gas from an onshore or offshore compression station to the one or more storage conduits 1202 and / or to receive compressed gas from the one or more storage conduits 1202 during energy discharge.

[0507] In some embodiments, the one or more storage conduits 1202 are made of polymer, optionally commercial polyethylene (PE) pipes such as PE 100 RC, or custom-manufactured pipes. Additionally or alternatively, the one or more storage conduits 1202 are made of cement and / or metal. In some embodiments, the conduit 1202 comprises a polymer pipe at least partially encased in cast concrete, thereby potentially providing additional structural strength and / or sufficient weight to potentially facilitate submergence and / or stabilization on the seabed.

[0508] Each of the one or more storage conduits 1202 has a cross sectional diameter, optionally from 1 to 5m, optionally from 3 to 6m, optionally from 5 to 15m.

[0509] Each of the one or more storage conduits 1202 has a length, optionally from 100m to 500m, optionally from 200m to 700m, optionally from 400 to 100m. In some embodiments, the length of the one or more storage conduits 1202 is very long, for example, 1km, 2km, 5km or 100km. In some embodiments, the length of the one or more storage conduits 1202 is chosen according to the requirements. In some embodiments, the length of the one or more storage conduits 1202 can be any length.

[0510] In some embodiments, optionally, the one or more storage conduits 1202 are anchored to the seabed 1204 using weights 1210, made of, for example, concrete mattresses, gabions, rocks, or metal elements. In some embodiments, the weights 1210 are distributed along the length of the one or more storage conduits 1202 to counterbalance buoyancy of the one or more storage conduits 1202, for example, when the one or more storage conduits 1202 are filled with compressed gas.

[0511] In some embodiments, the system 1200 further comprises at least one manifold 1212 configured to distribute compressed gas between the one or more storage conduits 1202. Optionally, each elongated storage conduit from the one or more storage conduits 1202 operates independently. Alternatively, the one or more storage conduits 1202 are interconnected via gas and / or water connections (not shown in Figures 12A-C).

[0512] In some embodiments, optionally, the one or more storage conduits are one or more elongated storage conduits.anchors

[0513] In some embodiments, Figures 12D-G illustrate configurations in which an elongated storage conduit 1202 is secured to a seabed without requiring the conduit itself to be sufficiently heavy to counteract buoyancy, for example, without requiring the conduit to (at least entirely) be made of concrete and / or another high-density material. Using at least one anchor (1210, 1210a, 1210b, and / or 1210c) rather than relying on the weight of the conduit itself allows the use of lighter- weight conduits, for example polymer pipes such as polyethylene (PE) pipes, thereby potentially reducing manufacturing and / or installation costs, increasing flexibility in material selection, and allowing the conduit to be at least partially buoyant, for example, when released from anchoring. In some embodiments, anchors 1210a, 1210b, and / or 1210c are an exemplary Implementations of weights 1210 described herein.

[0514] In some embodiments, the anchoring design is determined based on a ratio between (i) the weight of the anchoring material (e.g., concrete) required to counteract buoyancy and facilitate submergence, and (ii) the internal volume of the conduit containing compressed gas, which generates upward buoyant forces. In some embodiments, this ratio is predefined and maintained during selection and design of the anchor configuration, The overall cost of anchoring may depend on the number of anchoring elements used and the spacing between them along the conduit. In some embodiments, instead of mounting discrete weights at intervals, concrete is cast around at least a portion of the polymer conduit to form a composite structure having an inner polyethylene pipe and an outer concrete layer, for example as shown in Figure 12G. In some embodiments, the concrete encasement extends along substantially an entire length of the conduit, while in other embodiments it extends along one or more spaced-apart segments or along adjacent segments forming a substantially continuous encased region. The segments may have a length, for example, from 20 to 60 meters, optionally from 50 to 100 meters, optionally from 80 to 150 meters, optionally from 100 to 300 meters. Such a configuration may reduce installation complexity and anchoring assembly costs, which can vary depending on transportation, handling, sliding or clamping of weights onto the conduit, mold preparation, and other deployment conditions. Accordingly, multiple anchoring configurations are contemplated.

[0515] Referring now to Figure 12D, showing a schematic representation of an exemplary anchoring configuration for an underwater storage conduit 1202, according to some embodiments of the invention.

[0516] In some embodiments, a plurality of anchors 1210a can be deployed on conduit 1202. In some embodiments, plurality of anchors 1210a are spaced along the length of the conduit 1202, such that the conduit is held in a stable position relative to the seabed, and / or such that the conduit is at least partially embedded (e.g., sunk) into the seabed and / or supported / secured thereagainst. Optionallyplurality of anchors 1210a are spaced along the entire length of conduit 1202. This configuration potentially allows anchoring of a long conduit, for example, having a length of hundreds of meters (or more) while using a relatively low amount of concrete and / or other high-density material.

[0517] In some embodiments, plurality of anchors 1210a are made of concrete and / or another high-density material (mattresses, gabions, rocks, and / or metal elements), for example, for providing gravitational downward force. In some embodiments, the plurality of anchors 1202a are configured to counterbalance buoyancy of the conduit 1202 itself and / or buoyancy forces when the conduit is at least partially filled with compressed gas, such that the conduit remains secured near and / or on the seabed.

[0518] In some embodiments, plurality of anchors 1210a comprises and / or are shaped as anchoring rings 1210a positioned around at least a portion of the outer circumference of the conduit 1202, optionally surrounding substantially the entire outer circumference of the conduit 1202. In some embodiments, each anchoring ring comprises a clamp portion 1240 configured to mechanically engage the conduit 1202 and a weighted portion 1242 configured to apply a downward force. In some embodiments, resistance to buoyancy is provided by both the weighted clamp portion 1240 and the weighted portion 1242. In some embodiments, a majority of the buoyancy-resisting force is provided by the weight portion 1242. For example, in some embodiments, the weight of the clamp portion 1240 provides about 5%-30%, or about 15%— 35%, or about 20%-40% of the buoyancy-resisting force, while the weight portion 1242 provides about 70%-90%, or about 65%-85%, or about 60%80% of the buoyancy-resisting force.

[0519] In some embodiments, the anchors are installed onto the conduit prior to deployment into the waterbody. In some embodiments, installation comprises closing the clamp portion 1240 around the conduit using one or more fastening elements 1241, for example bolts, screws, pins, latches, and / or locking mechanisms. In some embodiments, one or more polymer liners and / or sleeves 1243 (for example, PE sleeves) are positioned between the clamp portion and the conduit, for example, to reduce abrasion, reduce friction, and / or reduce risk of damage to the conduit during installation and / or operation. In some embodiments, after installation of the anchoring rings, the conduit is deployed into the waterbody and the weight portions pull the conduit downward toward the seabed. In some embodiments, the weighted portion 1242 comprises one or more protrusions, spikes, and / or teeth 1246 configured to engage the seabed and potentially reduce lateral movement of the conduit. In some embodiments, the anchoring ring is configured such that a center of mass of the anchoring ring biases the protrusions 1246 to face downward, thereby assisting the protrusions to engage the seabed during deployment and / or operation. In some embodiments, the anchor further comprises one or more cables 1250, optionally, steel cables. In some embodiments, one or more cables 1250 may at leastpartially surround the conduit (as illustrated, for example, in Fig. 12D) and / or extend at least partially along the conduit (as illustrated, for example, in Fig. 12F). The one or more cables may be positioned at a lower portion of the weighted portion positioned at a lower portion of the weight portion (e.g., concrete weight), optionally arranged in a tensioned configuration (for example pre-tensioned and / or maintained under tensile load). The steel cables may extend along at least a portion of the conduit length and / or between adjacent anchors, for example, routed through designated passages, channels, and / or openings formed in the weight portions. In some embodiments, the tensioned steel cables are configured to carry tensile loads and thereby reduce bending, folding, excessive curvature, and / or local buckling of the conduit. Additionally or alternatively, the steel cables 1250 may function as tensile reinforcement elements for the anchoring elements (e.g., concrete portions), potentially reducing flexural stresses and decreasing the risk of cracking. In some embodiments, the one or more cables 1250 further assist in alignment and / or positioning of the anchors, for example, during installation, for example by maintaining relative positioning between adjacent anchors and / or stabilizing the anchors with respect to the conduit during deployment.

[0520] Referring now to Figure 12E, showing a schematic representation of an exemplary deployment method of an underwater storage conduit 1202 with an anchoring configuration, according to some embodiments of the invention. Figure 12E illustrates a non-limiting example in which the conduit 1202 is coupled to anchors 1210a (f described in relation to Figure 12D); however, it is appreciated that the anchor(s) may alternatively and / or additionally comprise any of the anchor configurations described herein, for example, one or more anchors 1210b and / or 1210c as described in relation to Figure 12F and / or Figure 12G, respectively.

[0521] In some embodiments, prior to and / or during deployment, elongated storage conduit 1202 is coupled to one or more anchors (e.g., anchors 1210a). In some embodiments, the conduit is temporarily coupled to at least one floter (e.g., buoy) 1248 using one or more securing elements 1249 (e.g., straps, ropes, and / or tethers), such that the conduit is supported above or near the water surface. Optionally, at least one floter 1248 is an elongated buoy extending along at least a portion of the conduit 1202, for example having a length shorter than the conduit, approximately equal to the conduit, and / or longer than the conduit. In some embodiments, the conduit 1202 is towed along the water surface to a desired offshore location while supported by the buoy. After positioning the conduit 1202 at the desired location, the one or more securing elements 1249 (e.g., straps, ropes, and / or tethers) are released and / or cut (for example by a release mechanism and / or by an operator), thereby detaching the buoy and allowing the anchors 1210a to pull the conduit 1202 downward toward the seabed for installation. A potential advantage of deploying the conduit using a temporary buoy and towing isfacilitating controlled installation and accurate positioning of the conduit prior to sinking, optionally without requiring heavy lifting equipment.

[0522] Referring now to Figure 12F, showing a schematic representation of an alternative anchoring configuration for an underwater storage conduit, according to some embodiments of the invention. In some embodiments, anchoring rings 1210b may be a variant of anchoring rings 1210A described herein (for example, with reference to Figure 12D). In some embodiments, the anchoring rings 1210b are configured to be slid onto the conduit 1202 through the lume of the rings, alterantively or additionally, anchoring rinngs 1210b are configured to be mounted on conduit, for example in a manner similar to that described with respect to anchoring rings 1210a.

[0523] In some embodiments, Figure 12F illustrates an anchoring arrangement in which a plurality of concrete anchoring elements are mounted directly onto an elongated storage conduit (for example one of the storage conduits 1202). In some embodiments, the concrete anchoring elements are configured as discrete blocks or segments that “ride” on the conduit and are mechanically coupled to the conduit, for example by clamps, brackets, or mating profiles that engage an outer surface of the conduit.

[0524] In some embodiments, the anchoring rings 1210b (and / or anchoring rings 1210a shown in Figure 12D) are positioned along at least a portion of the conduit 1202 in a closely spaced arrangement, for example, adjacent to one another and / or with small gaps therebetween (e.g., substantially without gaps or without large gaps), optionally along substantially an entire length of the conduit 1202 and / or along one or more selected sections thereof. In some embodiments, “adjacent” or “closely spaced” includes configurations in which at least a portion of neighboring anchoring rings are in direct physical contact with one another.

[0525] In some embodiments, such a closely spaced arrangement potentially reduces local bending, kinking, and / or localized deformation of the conduit wall, for example, when the conduit is formed from a polymeric material such as polyethylene (PE) or another plastic material, thereby potentially reducing risk of localized indentation and / or “digging-in” of the anchoring element into the conduit. In some embodiments, installation of a plurality of anchoring rings 1210b in a closely spaced arrangement potentially allows formation of a substantially continuous anchored region along the conduit 1202. A potential advantage of such a configuration is that continuous and / or near-continuous anchoring can be achieved by simple installation of multiple relatively small anchoring units, for example, without requiring a single elongated anchor structure.

[0526] In some embodiments, one or more cablea 1250, optionally a steel cable, is coupled to lower portions of the anchoring elements and extends along at least a portion of the conduit length. In some embodiments, the steel cable 1250 is further configured to limit bending, flexing, and / or excessivecurvature of the conduit during deployment and / or operation, for example, to potentially reduce and / or optionally to prevent buckling and / or excessive sagging between adjacent anchoring elements.

[0527] In some embodiments, the cable 1250 extends along the conduit 1210 in configurations where the anchors are closely spaced (as shown for example in Fig. 12E), spaced apart (as shown for example in Fig. 12D), and / or in configurations including sections of densely arranged anchores separated by one or more gaps between the section.

[0528] In some embodiments, anchors 1210b comprise at least one, optionally two, cable passages and / or a clearance channel (e.g., a notch, slot, opening, or through-bore) configured to receive and guide the steel cable along the conduit, optionally located at a lower portion of the anchor for maintaining the cable near a lower portion of the conduit.

[0529] Referring now to Figure 12G, showing a schematic representation of an additional anchoring configuration for an underwater storage conduit, according to some embodiments of the invention. In some embodiments, anchor 1210c may be in the form of and / or comprise a concrete and / or any other high-density material case. In some embodiments, the conduit 1202 is a polymer conduit (for example, a polyethylene (PE) pipe) is at least partially encased in concrete and / or any other high-density material to form anchor 1210c. In some embodiments, the concrete is cast around the polymer conduit along substantially the entire length of the conduit, while in other embodiments the concrete is cast only around one or more portions or segments of the conduit, for example, discrete sections spaced along the conduit length. In some embodiments, casting concrete only on selected segments of the conduit potentially reduces overall material usage and cost while still providing sufficient anchoring force. In some embodiments, a length of the concrete-encased segments is determined based on structural and deployment constraints, such as submergence without fracture and the lifting capacity of installation equipment. For example, segments may have a length of 30-60 meters, and in other embodiments may extend to hundreds of meters.

[0530] Tn some embodiments, the anchor 1210c comprises one or more openings and / or channels 1240, for example, two channels positioned at a lower portion of the concrete encasement (anchor 1210c). In some embodiments, the channels are configured to receive a steel cable, chain, and / or similar tensile element (e.g., such as cable 1250 shown in Fig. 12C). In some embodiments, the cable potentially reduces tensile loading of the concrete encasement (anchor 1210c), for example by bearing at least a portion of tensile forces, thereby potentially reducing cracking, fracture, and / or bending (e.g., flexural deformation) of the concrete. In some embodiments, the steel cable is used to mechanically connect the conduit to additional and / or adjacents anchors (e.g., adjacent sections of conduit 1202 cased within anchor 1210c). In some embodiments, the cable is configured to limit bending, flexing, and / or verticalmovement of the conduit 1202 between the anchors, for example, to potentially reduce and / or prevent uplift, excessive curvature, and / or displacement due to buoyancy forces or seabed currents.

[0531] additional embodiments

[0532] In the following paragraphs, additional embodiments of the invention will be explained. These embodiments present variations and / or complementary information of the systems described herein.

[0533] In some embodiments, the hot-water system and the cold-water system are separated.

[0534] Exemplary TES system comprising one tank for storing thermal storage liquid

[0535] Referring now to Figure 13, showing a schematic representation of an exemplary TES assembly for storing hot and cold pressurized thermal storage liquid comprising one tank, according to some embodiments of the invention. In some embodiments, the TES assembly 1314 comprises a tank 1328 configured to withstand pressure and temperature conditions, as disclosed in relation to the storage tanks above.

[0536] In some embodiments, the tank 1328 contains thermal storage liquid which naturally separates according to temperature. Hot thermal storage liquid, having lower density, rises and accumulates in an upper region of the tank 1328, while cold thermal storage liquid, having higher density, settles in a lower region of the tank 1328. A valve 1330 allows extraction of thermal storage liquid from the upper region of the tank 1328, while valve 1332 allows extraction of thermal storage liquid from the lower region of the tank, potentially allowing the same tank to simultaneously serve as a hot thermal storage liquid and cold thermal storage liquid storage.

[0537] In some embodiments, the tank 1328 comprises at least one inlet opening 1334 configured for introducing thermal storage liquid into the tank 1328. Optionally, the at least one inlet opening 1334 comprises a controlled port connected to the conduit 1312 that circulates thermal storage liquid in the system 1000.

[0538] Potential advantages of the TES assembly 1314 configured for storing pressurized cold and hot thermal storage liquid are:

[0539] • Reducing space required for the TES assembly 1314 by enabling the same tanks to serve alternately as hot and cold liquid reservoirs;

[0540] • Reducing construction and installation costs.

[0541] In some embodiments, the TES assembly 1314 stores hot and cold in the system 1000, and, in some embodiments, the TES assembly 1314 stores hot and cold in a system which cycles a liquid and requires storing of hot and cold liquid.Exemplary system for drying compressed gas supplied to an underwater compressed gas storage system

[0542] Without being bound by theory, gas discharged from a compressor is at elevated pressure, at a temperature higher than the ambient temperature, for example by several tens of degrees Celsius, and at a high moisture content, generally at about 100% relative humidity. In some embodiments, as the compressed gas flows through a conduit (e.g., fourth connector 430, shown in Figs. 4A-4D) toward one or more underwater storage tanks, the gas cools down as a result of heat transfer to the surrounding environment. Cooling of the gas causes water vapor to condense out of the gas. Generally, the condensed water accumulates in low points along the conduit, which may restrict flow and / or cause partial and / or complete blockage. In some embodiments, it is desirable to reduce the moisture content of the compressed gas already at the compressor outlet and / or prior to introduction into the storage tank. Conventional approaches include drying using desiccant-based dryers and / or adsorption systems, and / or cooling the gas to a low temperature to induce condensation followed by draining the condensate; however, such drying systems are expensive, particularly at the flow rates relevant to the systems described herein.

[0543] In some embodiments, during the generation process, the gas cools naturally as it expands. In some embodiments, this cooling is utilized to create a cold reservoir that is subsequently used to cool the compressed gas at the compressor outlet (e.g., a last compressor prior to introduction of the compressed gas into the underwater storage tank), thereby inducing controlled condensation and removal of water potentially without requiring dedicated, costly drying systems.

[0544] Referring now to Figure 14 A, showing a schematic representation of an exemplary generation subsystem 1400b comprising a stage for producing extra-cooled water for drying compressed gas, according to some embodiments of the invention.

[0545] In some embodiments, heat is transferred from a thermal energy storage (TES) unit 1406, for example by circulating a heating liquid such as hot water from a hot storage tank 1420, for example comprised in the TES 1406. In some embodiments, the hot water flows through a main conduit 1422, which branches into secondary conduits 1422A and 1422B. In some embodiments, the hot water transfers heat via the secondary conduits 1422 A and 1422B to the gas through corresponding heat exchangers 1412D and 1412E, respectively, prior to entry of the gas into turbines 1418A and 1418B, respectively, it is to be noted that the above-described heat transfer path (e.g., from the TES 1406 via the main conduit 1420 and the secondary conduits 1422 A and 1422B through the heat exchangers 1412D and 1412E) is a non-limiting example provided for purposes of illustration. In some embodiments, heat transfer between the TES and the gas in the generation subsystem 1400B is implemented using other configurations, for example any of the heat transfer arrangements describedin relation to Figures 3A-3M. Additionally, it is to be noted that water is a non-limiting example of a heating and / or cooling medium (thermal storage liquid). In some embodiments, the heating and / or cooling medium comprises any suitable thermal storage liquid and / or heat transfer medium, including liquids and / or other phases of matter, for example gases, vapors, and / or phase-change materials, and may comprise one or more materials selected to facilitate heat transfer within the system.

[0546] In some embodiments, the water exiting heat exchangers 1412D and 1412E has a lower temperature and / or lower enthalpy (e.g., latent heat) than the water entering the heat exchangers 1412D and 1412E via conduits 1422A and 1422B, respectively. In some embodiments, the temperature and / or enthalpy of the water exiting heat exchanger 1412D is not necessarily equal to the temperature and / or enthalpy of the water exiting heat exchanger 1412E.

[0547] In some embodiments, water exiting at least one of the heat exchangers 1412D and 1412E is further cooled. For example, in some embodiments, water exiting one or both of the heat exchangers 1412D and 1412E is directed to an additional cooling stage (e.g., additional heat exchanger).

[0548] In the example shown in Figure 14A, water exiting heat exchanger 1412D is stored in a cold water storage tank 1424, as descried herein. In some embodiments, water exiting heat exchanger 1412E is directed to an additional heat exchanger 1412F positioned downstream of the last turbine stage. In some embodiments, an operating regime of the last turbine is defined such that the gas temperature at the turbine outlet is lower than a temperature of the surrounding waterbody by a predefined temperature difference, for example by a few degrees Celsius. In some embodiments, in the heat exchanger 1412F positioned downstream of the turbine, the cold expanded gas further cools the water to a temperature below the temperature of the surrounding waterbody, thereby producing extra-cooled water. In some embodiments, the extra-cooled water exits the heat exchanger 1412F via conduit 1423C and is stored in one or more insulated tanks 1443, and maintained, for example, until a subsequent compression processe.

[0549] Without being bound by theory, in a multi-stage expansion system, the gas temperature decreases at each expansion stage, and downstream of the last turbine stage the gas temperature is generally the lowest within the system. A potential advantage of positioning heat exchanger 1412F for producing extra-cooled water downstream of the last turbine. e.g.,1418B, is that this location generally provides the coldest available gas stream to be utilzed forcooling. This positioning potentially allows a sufficient temperature difference between the expanded gas and the water being cooled (optionally a maximized temperature difference), thereby potentially improving heat transfer effectiveness and / or facilitating cooling of the water to a temperature below the temperature of the surrounding waterbody.In some embodiments, water supplied to the heat exchanger 1412F for producing extra-cooled water is received from any heat exchanger of the system and / or from a plurality of heat exchangers of the system.

[0550] A potential advantage of directing water exiting from thre last heat exchanger of the genration process (e.g., 1412E) to heat exchanger 1412F for producing extra-cooled water, is that heat exchanger 1412E is that that gas upstream of heat exchanger 1412E has already undergone expansion in one or more previous turbine stages and is therefore at a lower temperature. Consequently, the water transferring heat to the gas in heat exchanger 1412E may be cooled to a lower temperature compared to water exiting an upstream generation-stage heat exchanger (e.g., heat exchanger 1412D), thereby improving production of extra-cooled water in the subsequent heat exchanger 1412F.

[0551] Referring now to Figure 14B, showing a schematic representation of an exemplary compression subsystem 1400a configured to utilize extra-chilled water for removing moisture from compressed gas, according to some embodiments of the invention.

[0552] In some embodiments, the system comprises a heat exchanger 1412C for cooling the compressed gas. In some embodiments, heat exchanger 1412C is positioned to cool the compressed gas prior to its introduction into storage tank 1304 (e.g., positioned downstream of the last compressor 1408F), optionally immediately upon exiting the last compressor 1408F.

[0553] In some embodiments, the compressed gas is cooled in heat exchanger 1412C by transferring heat to extra-cooled water supplied from extra-cooled water storage tank 1443, for example via conduit 1415A. In some embodiments, the extra-cooled water has a sufficiently low temperature to cool the compressed gas so as to induce condensation of at least a portion of water vapor and / or to achieve a desired degree of condensation of moisture contained in the compressed gas, (taking into account heat transfer characteristics of the heat exchanger 1412C). For example, the extra-cooled water may have a temperature lower than the temperature of the surrounding waterbody, and the heat exchanger 1412C is configured to cool the compressed gas to a temperature that results in condensation, for example to a temperature at and / or near the seawater surface temperature. In some embodiments, the condensed water is collected in a water trap 1470 and, optionally, is automatically drained throughout the compression process. In some embodiments, the condensed water exits the heat exchanger together with the compressed gas (for example, via conduit 1408G, as shown in the Figure) and is subsequently captured in the water trap 1470 positioned upstream of heat exchanger 1412C, along conduit 1408G. Alternatively and / or additionally, condensation and separation of at least a portion of the water occur within the heat exchanger 1412C, and the separated water is discharged from the heat exchanger.In some embodiments, after cooling and / or moisture removal, the compressed gas exits the heat exchanger and / or water trap 1470 at a temperature close to the temperature of the surrounding waterbody and at approximately 100% relative humidity (the gas reaches a new saturation state at the reduced temperature, e.g., at or near the waterbody temperature (e.g., seawater temperature)). Without being bound by theory, the absolute moisture content of the gas is reduced compared to the moisture content at the compressor outlet, since saturated gas at a lower temperature contains less water vapor than saturated gas at a higher temperature. A potential advantage of the compressed gas exits the heat exchanger at a temperature close to the temperature of the surrounding waterbody, potentially reducing the risk for significant additional cooling along the subsea conduit, thereby potentially reducing the likelihood of additional condensation and water accumulation within the conduit. A potential advantage of the compressed gas exiting the heat exchanger at a temperature close to the temperature of the surrounding waterbody is that it potentially reduces the extent of additional cooling along the subsea conduit, thereby reducing the likelihood of further condensation and water accumulation within the conduit. In some embodiments, additional condensation may occur along the subsea conduit during transport to the underwater storage tank; however, since most of the water vapors have already been removed in the cooling stage, the remaining amount of condensate is expected to be negligible, thereby significantly reducing the risk of accumulation and / or blockage in the subsea conduit.

[0554] In some embodiments, water exiting the heat exchanger (for example via conduit 1415B) is directed to a collection tank 1421. In some embodiments, the temperature of the water exiting the heat exchanger is higher than the temperature of the extra-cooled water entering the heat exchanger; however, in some embodiments, the exiting water remains at a sufficiently low temperature to be reused for cooling the compressed gas during the compression process. For example, in some embodiments, such water is supplied to a cold water storage tank 1442 for subsequent use in cooling stages of the compression subsystem.

[0555] In some embodiments, cooling of the compressed gas for inducing condensation and water removal may be performed using, alternatively and / or in addition to, the extra-cooled water generated during the generation process using another chilling medium, for example water cooled by an external cooling system, a glycol-based cooling solution, seawater subjected to active refrigeration, a brine solution, or any other suitable heat transfer medium having a temperature and / or enthalpy sufficiently low to induce condensation of moisture from the compressed gas (not necessarily a liquid medium). Utilizing the extra-cooled water generated during the generation process, where the cooling energy is derived from the natural temperature reduction occurring during gas expansion provide the potential advantages of reducing and optionally eliminating the need for dedicated refrigeration equipment, andimproving overall system energy efficiency and / or round-trip efficiency (RTE). Additionally, the extra-cooled water generated during the generation process may, in addition to or alternatively to the water-condensation process, be used for other purposes within the system.

[0556]

[0557] Referring now to Figure 15A-B, showing a schematic representation of an exemplary system for storing energy and extracting work from the energy in a compressed gas energy storage system using a shared heat exchanger configuration, according to some embodiments of the invention.

[0558] In some embodiments, at least one heat exchanger is shared between the compression subsystem (e.g., compression subsystem 300A) and the generation subsystem (e.g., generation subsystem 300B). Optionally, all of the heat exchangers used for compression subsystem and / or the generation subsystem are shared A potential advantage of such sharing is cost savings, for example, by reducing the number of heat exchangers, and / or reducing installation and / or maintenance requirements. In such embodiments, the shared heat exchangers are configured to operate selectively in different modes, such that it is used to transfer heat from the gas during compression and, at other times, to transfer heat to the gas during generation, according to system requirements. In some embodiments, such sharing is facilitated by an arrangement of valves and / or conduits that selectively directs gas flow and / or heat transfer fluid flow through the shared heat exchanger according to the operational mode.

[0559] Figure 15A illustrates an exemplary system with a shared heat exchanger configuration. In some embodiments, the system comprises a plurality of compressors, for example, three compressors 1508A-1508C, as shown in the figure, and a plurality of turbines (e.g., turboexpanders), for example, two turbines 1518A and 1518B as shown in the figure. In some embodiments, the system comprises a plurality of shared heat exchangers, optionally, as the number of compressors in the plurality of compressors, for example, three heat exchangers 1512A-1512C, as shown in the figure. In such embodiments, each of the shared heat exchangers 1510A-1510C is configured to operate in a first mode during compression, in which heat is transferred from the compressed gas exiting at least one of the compressors 1508A-1508C to a thermal storage liquid (e.g., cool water), and in a second mode during generation, in which heat is transferred from the thermal storage liquid (e.g., hot water) to the compressed gas prior to entry into at least one of the turboexpanders 1518A and 1518B. In some embodiments, the system comprises a thermal energy storage (TES) 1506, for example comprising a hot thermal storage tank 1520, and a cold thermal storage tank 1542.

[0560] In some embodiments, the system comprises a valve and / or conduit arrangement configured to selectively control flow of gas between the turbine array (e.g., turboexpanders 1518A- 1518C) andthe compressor array (e.g., compressors 1508A-1508C), thereby allowing switching between a compression mode and a power generation mode.

[0561] In some embodiments, this arrangement comprises: (i) an outlet of at least one compressor (e.g., compressor 1508A, 1508B) is fluidly connected to an inlet of a corresponding (e.g., adjacent) turbine (e.g., turbine 1518A, 1518B, respectively) by a conduit network comprising at least one shared conduit (e.g., 1584A and 1584C, respectively) and / or by a shared valve (e.g., valvel588A and 1588C, respectively); and / or (ii) an inlet of at least one compressor (e.g., compressor 1508B, 1508C) fluidly connected to an outlet of the corresponding (e.g., adjacent) turbine (e.g., turbine 1518B, 1518C, respectively) by a conduit network comprising at least one shared conduit (e.g., 1584B and 1584D, respectively) and / or at lest one shared vlave (e.g., valve 1588B and 1588D, respectively). In some embodiments, the valves (e.g., 1588A-E) are one or more gas switching valves, optionally disposed along the shared conduits, optionally, at each shared conduit, and are configured to selectively establish a gas flow path according to an operational mode of the system. In some embodiments, alternatively to (or in addition to) using a shared conduit, the outlet(s) and / or inlet(s) of the compressors and the corresponding inlet(s) and / or outlet(s) of the turbines are connected directly to a shared switching valve (e.g., a manifold valve), such that the shared switching valve itself provides the shared flow junction and selectively routes the gas flow according to the operational mode.

[0562] In some embodiments, an inlet of the last compressor stage (e.g., compressor 1508C) is fluidly connected to an outlet of the compressed gas storage unit 1504 via a conduit network comprising at least one shared conduit (e.g., shared conduit 1584D) and / or at least one shared gas valve (e.g., valve 1588C). In some embodiments, an outlet of the last compressor stage (e.g., compressor 1508C) is fluidly connected to an inlet of the compressed gas storage unit 1504 via a conduit network comprising at least one shared conduit and / or a shared valve (e.g., valve 1588E). In such embodiments, the switching gas valves are positioned and configured to selectively establish either (i) a charging flow path from the compressor 1508C to the compressed gas storage unit 1504 during a compression mode, or (ii) a discharge flow path from the compressed gas storage unit 1504 toward the turbine array during a generation mode, while blocking reverse and / or undesired flow paths.

[0563] In some embodiments, the system comprises a valve and / or conduit arrangement configured to selectively control flow of thermal storage liquid between a cold thermal storage tank 1542 and a hot thermal storage tank (e.g., tank 1520 of TES 1506), thereby allowing the selective supply of either cold or hot thermal storage liquid according to an operational mode of the system. In some embodiments, the cold thermal storage tank 1542 and the hot thermal storage tank 1520 are fluidly connected by a conduit network comprising at least one shared outlet conduit 1582 A and at least oneshared return (inlet) conduit 1582B. In some embodiments, a thermal storage meduim valve 1580A is positioned along the outlet conduit 1582A and is configured to selectively permit and / or block discharge of thermal storage liquid from the cold thermal storage tank 1542 (e.g., valve 1580A functions as a switching valve configured to determine whether a cold or a hot thermal storage liquid is supplied downstream components to the heat exchangers. In some embodiments, thermal storage medium valve 1580B is positioned along a retum / inlet conduit 1582B. In some embodiments, valve 1580B is configured to (i) permit introduction of heated thermal storage liquid into the hot thermal storage tank 1520 while preventing introduction of the heated thermal storage liquid into the cold thermal storage tank 1542, and / or (ii) permit introduction of cooled thermal storage liquid into the cold thermal storage tank 1542 while preventing introduction of the cooled thermal storage liquid into the hot thermal storage tank 1520 (e.g., valve 1580B functions as a switching valve configured to determine whether returned thermal storage liquid is directed to the hot thermal storage tank 1520 or to the cold thermal storage tank 1542)

[0564] Figure 15B illustrates an exemplary compression process using the shared heat exchanger configuration.

[0565] In some embodiments, during the compression mode, gas switching valves 1588A-1588E are positioned and configured to permit gas flow through the compressor array (e.g., compressors 1508A-1508C) and toward the compressed gas storage unit 1504, while blocking gas flow toward and / or from the turbine array (e.g., turboexpanders 1518A-1518B). In such embodiments, gas is sequentially compressed by one or more compressors and directed into the compressed gas storage unit 1504, while discharge of gas from the storage unit toward and / or through the turbines is prevented.

[0566] In some embodiments, thermal storage medium valve 1580A is configured to permit discharge of cold thermal storage liquid from the cold thermal storage tank 1542, while blocking discharge of hot thermal storage liquid from the hot thermal storage tank 1520. The cold thermal storage liquid is directed toward one or more of the shared heat exchangers 1512A-1512C. Tn some embodiments, within the shared heat exchangers 1512A-1512C, heat is transferred from the compressed gas to the thermal storage liquid, thereby heating the thermal storage liquid and cooling the compressed gas prior to storage. In some embodiments, the heated thermal storage liquid exiting the shared heat exchangers is directed toward thermal storage medium valve 1580B. In some embodiments, valve 1580B is configured to permit introduction of the heated thermal storage liquid into the hot thermal storage tank 1520, while preventing introduction of the heated thermal storage liquid into the cold thermal storage tank 1542.

[0567] Figure 15C illustrates an exemplary power generation process using the shared heat exchanger configuration.In some embodiments, during generation mode, gas switching valves 1588A-1588D are positioned and configured to permit discharge of compressed gas from the compressed gas storage unit 1504 and to route the discharged gas toward the turbine array (e.g., turboexpanders 1518A-1518B), while blocking gas flow toward the compressor array (e.g., compressors 1508A-1508C) and / or blocking introduction of gas into the compressed gas storage unit 1504. In such embodiments, the compressed gas is directed from gas storage unit 1504 through one or more of the shared heat exchangers 1512A-1512B and subsequently toward one or more turbines for expansion and work extraction. In some embodiments, thermal storage medium valve 1580A is configured to permit discharge of hot thermal storage liquid from the hot thermal storage tank 1520, while blocking discharge of cold thermal storage liquid from the cold thermal storage tank 1542. The hot thermal storage liquid is directed toward one or more of the shared heat exchangers 1512A-1512B. In some embodiments, within the shared heat exchangers 1512A-1512B, heat is transferred from the hot thermal storage liquid to the compressed gas, thereby heating the compressed gas prior to expansion in the turbine (1518A and / or 1518B). In some embodiments, the cooled thermal storage liquid exiting the shared heat exchangers is directed toward thermal storage medium valve 1580B. In some embodiments, valve 1580B is configured to permit introduction of the cooled thermal storage liquid into the cold thermal storage tank 1542, while preventing introduction of the cooled thermal storage liquid into the hot thermal storage tank 1520.

[0568] In the exemplary configuration shown in Figure 15C, the turbine array comprises two turbines (1518A and 1518B) and the shared heat exchanger set comprises two active heat exchangers (1512A and 1512B) during the generation process. Accordingly, in this example, heat exchanger 1512C is not active during the generation mode. In some embodiments, flow of thermal storage liquid to and / or from the inactive heat exchanger 1512C is selectively blocked, optionally by one or more additional valves (not shown) configured to isolate the heat exchanger 1512C from the thermal storage liquid circuit during generation.

[0569] Exemplary underwater gas storage units

[0570] In some embodiments, the systems and methods for storing energy and extracting work from a compressed gas energy storage system as described herein are configured to receive compressed gas from and / or to deliver compressed gas to substantially any suitable gas storage system. The disclosed systems are not limited to any particular storage configuration and / or geographic location, whether positioned on land, underwater, underground, offshore, airborne, and / or in elevated structures.

[0571] By way of non-limiting examples, the compressed gas storage unit may comprise one or more above-ground pressure vessels, buried and / or partially buried tanks, underground caverns (e.g., saltcaverns, mined caverns, porous rock formations, depleted hydrocarbon reservoirs), spherical and / or cylindrical steel tanks, composite pressure vessels, flexible membrane-based storage structures, floating storage units, suspended storage structures (e.g., tethered buoyant tanks), high-pressure pipeline sections, pipeline-based storage networks, or modular containerized storage assemblies. In some embodiments, the storage unit may comprise closed rigid tanks; in other embodiments, partially open or hydrostatically balanced structures; and in yet other embodiments, storage volumes configured to accommodate phase-changing gases (e.g., supercritical or liquefied gases).

[0572] In some embodiments, the compressed gas storage unit (e.g., storage unit 104-1504) comprises one or more underwater gas storage units configured to be positioned at depth in a waterbody (e.g., on and / or near a seabed), for example, as described herein, for example, with reference to figures 11A-B, and / or 12A-G. In some embodiments, for example, the one or more underwater gas storage units are similar and / or as the storage tanks described in U.S. Provisional Patent Application No. 63 / 762,182 filed on February 24, 2025, U.S. Provisional Patent Application No.63 / 907, 962 filed on October 30, 2025, and / or in the corresponding PCT application, “STRUCTURES FOR UNDERWATER ENERGY STORAGE”, Docket No. 105992, 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.

[0573] Exemplary tanks configurations

[0574] In some embodiments, the system’s compressed gas storage unit comprises a plurality of compressed gas storage units 1604 (that may also be referred to as storage tanks). In some embodiments, the plurality of storage tanks 1604 is at the same height, for example, by being positioned on a flat surface in the seabed 1615 or by being mounted on one or more bases 1690, as shown, for example, in Figure 16A. In some embodiments, the plurality of storage tanks 1604 is positioned at different heights. In some embodiments, the plurality of storage tanks 1604 is stacked one on top of the other, for example, as shown in Figures 16B and 16C. Tn some embodiments, the plurality of storage tanks 1604 is positioned on an inclined surface in the seabed 1615, and each storage tank 1604 from the plurality of storage tanks 1604 is positioned in a different height, for example, as shown in Figures 16 A, 16B and 16C. In some embodiments, the plurality of storage tanks 1604, positioned at different heights, acts as one unit in terms of receiving and / or releasing of compressed air. In some embodiments, a water level in each storage tank 1604 from the plurality of storage tanks 1604 is matched. In some embodiments, each storage tank 1604 from the plurality of storage tanks 1604 contains compressed air and / or water. In some embodiments, a water / air ratio increases with a decrease of a height of the storage tank 1604. In some embodiments, each storage tank 1604 from the plurality of storage tanks 1604 experiences a net pressure which is the sum of thepressure exerted by the water outside and the opposite direction pressure exerted by the compressed air inside the storage tank 1604. In some embodiments, a net pressure increase with an increase of a height of the storage tank 1604 from the plurality of storage tanks 1604. In some embodiments, reinforcement is provided for counterbalancing the net pressure exerted on the storage tank 1604, optionally in the storage tank 1604 positioned highest where the net pressure is higher.

[0575] In some embodiments, the storage tank 100 further comprises one or more apertures 1696 (water openings) through which water freely flows into and out of the storage tank 1604.

[0576] Exemplary tanks configurations for operating at the same height

[0577] Referring now to Figure 16 A, showing a schematic representation of an underwater energy storage device and / or system comprising a plurality of storage tanks 1604 that have air flow communication between them positioned on one or more bases, 1690 according to some embodiments of the invention. In some embodiments, a device 1600a comprises an air flow pipe 1691 which branches into a plurality of pipes 1692 that directly communicate with a plurality of storage tanks 1604. In some embodiments, the plurality of storage tanks 1604 operates as one unit in terms of releasing and receiving of compressed air. In some embodiments, the plurality of storage tanks 1604 is mounted on the one or more bases 1690 such that the plurality of storage tanks 1604 are leveled and are relatively at the same height in relation to one another. In some embodiments, the plurality of storage tanks 1604 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 1604. In some embodiments, potential advantages of having a plurality of storage tanks 1604 acting as one unit, being relatively at the same height is the following:

[0578] a. reducing the number of valves required for controlling air flow to and from the plurality of storage tanks 1604.

[0579] b. enabling the use of a homogeneous variety of storage tanks 1604 from the plurality of storage tanks 1604 due to an even distribution of net pressure between the plurality of storage tanks 1604.

[0580] c. maximal capacity of stored compressed air of each storage tank 1604 from the plurality of storage tanks 1604 is independent of other storage tanks 1604 from the plurality of storage tanks 1604.

[0581] In some embodiments, a plurality of air valves (not shown) is installed on the plurality of pipes 1692 for allowing individual control of air flow to and / or from the plurality of storage tanks 1604. In some embodiments, a potential advantage of installing an air valve on the pipe 1692 is allowing isolation of one storage tank 1604 from the rest of the plurality of storage tanks 1604 for handling, due to, for example, maintenance.Exemplary tank configuration for operating at different heights

[0582] Referring now to Figure 16B, showing a schematic representation of an underwater energy storage device comprising a plurality of individual units of storage tanks stacked one on top of the other, according to some embodiments of the invention. In some embodiments, at least one storage tank 1604 of the plurality of storage tanks 1604 is stacked on top of another storage tank 1604 of the plurality of storage tanks 1604, optionally, all of the storage tanks 1604 of the plurality of storage tanks 1604 are stacked one above another, such that each of the storage tanks from the plurality of storage tanks 1604 is positioned at a different height. In some embodiments, device 1600b comprises an air flow pipe 1691, which branches into the plurality of pipes 1692 that are directly connected to the plurality of storage tanks 1604. In some embodiments, air flowing via pipes 1692 is controlled according to a plurality of valves 1694. In some embodiments, each of the storage tanks from the plurality of storage tanks 1604 differs in a pressure of the stored compressed air therein. In some embodiments, potential advantages of stacking the plurality of storage tanks 1604 are minimizing an occupied space by the underwater energy storage device 1600b on the seabed 1615 and / or lowering the cost of positioning the storage tanks 1604.

[0583] Referring now to Figure 16C, 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 1600c comprises a vertical arrangement of storage tanks 1604 comprising one or more storage tanks 1604A located at the bottom of the device, optionally, including the one or more water openings 1696. In some embodiments, storage tank 1604B is connected vertically to the one or more storage tanks 1604A by one or more connectors 1698, configured for allowing passage of water and / or air. In some embodiments, device 1600c further comprises one or more air pipes 1699 for receiving and / or releasing air (and / or any other used gass). In some embodiments, the underwater energy storage device 1600c is fabricated on land and is then mobilized in parts to the submerging site on the seabed 1615.

[0584] In some embodiments, potential advantages of mobilizing the underwater energy storage device 1600c in parts to the submerging site on the seabed 1615 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 1615, allowing more volume of compressed air to be stored in the same seabed 1615 area, both which leads to reducing costs for positioning and / or operating the underwater energy storage device 1600c.

[0585] Referring now to Figure 16D, 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 and / or system1600D comprises a gas flow pipe 1691 which branches into the plurality of pipes 1692, which are attached to a plurality of storage tanks 1604D. In some embodiments, the plurality of storage tanks 1604D operates as one unit in terms of receiving and releasing compressed gas. In some embodiments, optionally, each storage tank 1604D from the plurality of storage tanks 1604D 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 1604D operating as one unit are the following:

[0586] a. Preventing sand accumulation in the storage tank 1604D.

[0587] b. Prevention of moisture in the gas stored in the storage tank 1604D since water do not enter the storage tank 1604D.

[0588] In some embodiments, optionally, maximal volume capacity of stored compressed air of each storage tank 1604D from the plurality of storage tanks 1604D is independent of the height of other storage tanks 1604D from the plurality of storage tanks 1604D. In some embodiments, the compressed gas stored in a storage tank from the plurality of storage tanks 1604D has a volume that is constant with an increase in pressure of the compressed gas. In some embodiments, the compressed gas stored in the storage tank from the plurality of storage tanks 1604D 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 1604D 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.

[0589] Referring now to Figure 17 A, 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 (and / or system) 1700a comprises an at least one storage tank 1704, comprising one or more water openings 1796, and a plurality of enclosed storage tanks 1704E. Tn some embodiments, the device 1700a is positioned on an inclined surface in the seabed 1715. In some embodiments, each of the storage tanks of at least one storage tank 1704 and the plurality of enclosed storage tanks 1704E is connected to one or two neighboring tanks by a pipe 1792 by a plurality of connectors 1792 for enabling transfer of air and / or water. In some embodiments, the storage tank 1704 is positioned at the lowest height of the device 1700a. In some embodiments, an enclosed storage tank 1704E from the plurality of enclosed storage tanks 1704E positioned in a highest height is connected to the one or more air pipes 1799 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, compressed air is supplied via the one or more air pipes 1799 to occupy first the upmost enclosedstorage tank 1704E from the plurality of enclosed storage tanks 1704E followed by the occupying of a lower enclosed storage tank 1704E from the plurality of enclosed storage tanks 1704E and lastly occupying the storage tank 1704 such that a water level 1713 exists in the storage tank 1704. In some embodiments, during the release of compressed air from the device 1700a, water enters via the one or more water openings 1796 to gradually occupy the storage tank 1704 and the plurality of enclosed storage tanks 1704E, in a time sequence according to a height of the storage tank 1704 and the plurality of enclosed storage tanks 1704E. In some embodiments, the connectors 1792 from the plurality of connectors 1792 connect two neighboring tanks from the plurality of enclosed storage tanks 1704E and storage tank 1704 from an upper opening 1797 from a plurality of upper openings 1797 to a lower opening 1799 from a plurality of upper openings 1799. In some embodiments, a potential advantage of a connector 1792 connecting an upper opening 1797 from a plurality of upper openings 1797 to a lower opening 1799 from a plurality of upper openings 1799 is efficient water and / or air transfer.

[0590] Referring now to Figure 17B, 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 (and / or a system) 1700b comprises the air flow pipe 1791 which branches into the plurality of pipes 1792 that directly connect to the plurality of storage tanks 1704 positioned on an inclined surface on the seabed 1715. In some embodiments, one or more storage tanks 1704 from the plurality of storage tanks 1704 connect to the outside water by one or more downward facing water pipes 1795, which are attached to the one or more water openings 1796. In some embodiments, each downward facing water pipe 1795 from the one or more downward facing water pipes 1795 comprises a water opening 1795B for enabling entry and / or exit to and / or from the storage tank 1704. In some embodiments, one or more storage tank 1704 from the plurality of storage tanks 1704 positioned at the lowest height of the device 1700b contains water and compressed air having the water level 1713. In some embodiments, due to hydrostatic pressure, water and compressed air contained in the one or more downward facing water pipes 1795 have the water level 1713. In some embodiments, a potential advantage of equipping the device 1700b with one or more downward facing water pipes 1795 connecting the storage tank 1704 with the outside water is lowering the water level 1713 in the device 1700b and increasing a compressed air capacity of the device 1700b.

[0591] Referring now to Figure 17C, 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 1700c comprises the air flow pipe 1791 which branches into the plurality of pipes 1792 that directlyconnect to the plurality of storage tanks 1704. In some embodiments, the plurality of storage tanks 1704 are positioned in different heights to match a slope in the seabed 1715.

[0592] In some embodiments, the air flow pipe 1791 has a sealed end 1791 A. In some embodiments, the system 1700c is configured such that the sealed end 1791A is positioned at a height which is at least equal (or higher) to a highest portion of the storage tank 1714. A potential advantage of the sealed end 1791A is positioned at a height which is at least equal or higher to the highest portion of the storage tank 1704 is preventing water accumulation in the air flow pipe 1791.

[0593] In some embodiments, the plurality of pipes 1792 are made of a rigid material. In some embodiments, the air flow pipe 1791 is made of a rigid material. A potential advantage of the plurality of pipes 1792 or the air flow pipe 1791 being made of a rigid material is preventing formation of pockets or depressions in which water may be accumulated.

[0594] In some embodiments, each storage tank 1704 from the plurality of storage tanks 1704 connects to a main water pipe 1793 by the one or more downward facing water pipes 1795 which are attached to the one or more water openings 1796. In some embodiments, the main water pipe 1793 is positioned in an oblique angle to the surface of the earth, the oblique angle being generally following the slope in the seabed 1715. In some embodiments, the main water pipe 1793 comprises a water opening 1793A located in a part of the main water pipe 1793 positioned at a lower height, optionally in a first end of the main water pipe 1793, for enabling entry of water from the outside water to the main water pipe 1793 and vice versa. In some embodiments, the water opening 1793A 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 1793 has a sealed second end 1793B which is positioned higher to the first end. In some embodiments, due to hydrostatic pressure, water entering the system 1700c via the water opening 1793A has the unanimous water level 1713, i.e., a uniform water level across exists throughout the system 1700c. In some embodiments, a potential advantage of equipping the device 1700c with the main water pipe 1793 having the water opening 1793A 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 1700c since the water level 1713 is not dependent on the location of the one or more water openings 1796 in the lowest positioned storage tank 100 from the plurality of storage tanks 1704.

[0595] Exemplary energy storage device comprising a cluster of tubular structures

[0596] device and / or water connection

[0597] 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 manualwelding, 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.

[0598] The present inventors have found that clustering a plurality of the tubular structures 1804, 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.

[0599] Referring now to Figures 18A-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 1800 comprises a cluster comprising a plurality of the tubular structure 1804, optionally, vertically extending tubular structures. In some embodiments, the tubular structure 1804 defines at least one internal lumen configured to contain compressed gas therein.

[0600] In some embodiments, each of the plurality of the tubular structures 1804 extends along a substantially vertical axis when the energy storage device 1800 is deployed, for example, when positioned on a seabed. In such embodiments, for example, a lower end of each tubular structure 1804 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.

[0601] In some embodiments, all the tubular structures 1804 are made of the same material, for example, all the tubular structures 1804 are made of metal, and, in some embodiments, at least one of the plurality of the tubular structures 1804 is made of a different material, for example, at least one of the plurality of the tubular structures 1804 is made of metal and the other tubular structures 1804 are made of cement.

[0602] In some embodiments, the plurality of tubular structures 1804 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.

[0603] In some embodiments, the plurality of the tubular structures 1804 are attached to one another. In some embodiments, the plurality of the tubular structures 1804 are attached to one another by soldering to adhere the tubular structures 1804 to one another. Alternatively or additionally, a fastening mechanism (not shown in Figures 18A-B) is used to secure the plurality of the tubularstructures 1804 together. In some embodiments, the fastening mechanism is, for example, a metal band, a metal cable, or structural frame.

[0604] In some embodiments, the plurality of tubular structures 1804 are fluidly inter-connected to one another by a plurality of connectors 1892. In some embodiments, the plurality of connectors 1892 allow transfer of water and gas between the plurality of tubular structure 1804, such that the plurality of the tubular structures 1804 operate as one unit in terms of receiving and / or releasing of compressed gas.

[0605] In some embodiments, at least one of the plurality of the tubular structures 1804 comprises the one or more air openings 1806, the one or more air openings 1806 being connected to one or more air pipes 1899 (not shown in Figures 18A-B) for communicating the plurality of the tubular structures 1804 to a turbomachinery unit. In some embodiments, each of the plurality of the tubular structures 1804 comprises the one or more water openings 1896, for example as shown in Figure 18 A, and, in some embodiments, at least one of the tubular structures 1804 is sealed to the outside environment and does not comprise the one or more water openings 1896, for example as shown in Figure 18B. In some embodiments, the one or more water openings 1896 and / or the one or more air openings 1806 are in fluid communication with the at least one internal lumen.

[0606] In some embodiments, the plurality of the tubular structures 1804 are arranged in various configurations, for example round, hexagonal, or rectangular formations, depending on design and operational requirements.

[0607] Referring now to Figure 18C, 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 1800 comprises a cement cast 18704, which is positioned in between the plurality of the tubular structures 1804. A potential advantage of the cement cast 18704 positioned in between the plurality of the tubular structures 1804 is adhering to the plurality of the tubular structures 1804 and enhancing the structural stability of the energy storage device 1800.

[0608] Referring now to Figure 18D, 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 1804 arranged in a triangular formation, a gap 18705 is formed. In some embodiments, the gap 18705 is a chimneylike space (in view of the height of the tubular structures 1804). In some embodiments, the one or more water openings 1896 are arranged to allow for water exchange between the plurality of the tubular structures 1804 and the water outside via the space.Referring now to Figure 18E, 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 1800 stores compressed gas. In some embodiments, the volume of the compressed gas stored in the energy storage device 1800 is defined by the water level 18706 inside the energy storage device 1800. In some embodiments, the plurality of connectors 1892 comprise connectors positioned at different heights of the energy storage device 1800. In some embodiments, the plurality of connectors 1892 comprise the following:

[0609] one or more high connectors 1892A which are mainly used for gas transfer, as they are located above the water level 18706 during gas storing;

[0610] one or more middle connectors 1892B which facilitate the exchange of both water and gas, depending on the water level 18706; and

[0611] one or more low connectors 1892C which are mainly used for water transfer, as they are located below the water level 18706 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 1804 are equipped with the weight 1810.

[0612] Referring now to Figure 18F, 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 1804 and the weight 1810. In some embodiments, the overall cover 5710 seals the plurality of the tubular structures 1804. In some embodiments, the overall cover 5710 is configured to allow gas flow from the plurality of the tubular structures 1804 via the one or more air pipes 1899.

[0613] Referring now to Figure 18G, 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 1804 are connected to one or more gas connectors 18712, which connect each of the plurality of the tubular structures 1804 to one another and allow for gas transfer between the plurality of the tubular structures 1804, thereby facilitating the plurality of the tubular structures 1804 to operate as one unit in terms of receiving and / or releasing of compressed gas.

[0614] Referring now to Figure 18H, 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 1800 comprises an air flow pipe 18616 which branches into a plurality of pipes 18614 that directly communicate with the plurality of the tubular structures 1804,thereby facilitating the plurality of the tubular structures 1804 to operate as one unit in terms of receiving and / or releasing of compressed gas.

[0615]

[0616] means

[0617] Referring now to Figure 19, 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 1900 comprises the plurality of the tubular structures 1804. In some embodiments, at least two of the plurality of the tubular structures 1804 is directly connected to the one or more air pipes 1899. In some embodiments, at least two of the plurality of the tubular structures 1804 which are directly connected to the one or more air pipes 1899 are not adjacent to each other but are instead separated by at least one tubular structure 1804, potentially reducing localized pressure differences.

[0618] In some embodiments, the energy storage device 1900 comprises an upper banister 19802. In some embodiments, a space defined by the upper banister 19802 is configured for containing more of the one or more weights 1910. A potential advantage of the one or more weights 1910 contained in the space defined by the upper banister 19802 is anchoring the energy storage device 1900 to the seabed. In some embodiments, when anchored to the seabed, the plurality of tubular structures 1904 extend upwardly in a substantially vertical direction from the seabed.

[0619] In some embodiments, the energy storage device 1900 comprises a lower banister 19804, positioned on the platform 18610. In some embodiments, the lower banister 19804 allows for water exchange with the surrounding environment via a water pipe 1995, which protrudes from the lower banister 19804.

[0620] Referring now to Figure 20A-B, 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 2000 comprises a cluster of inter-connected tubular structures 2004. Tn some embodiments, the cluster of inter-connected tubular structures 2004 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 20D. In some embodiments, the cluster of interconnected tubular structures 2004 is connected to the one or more air pipes 1899.

[0621] In some embodiments, the cluster of inter-connected tubular structures 2004 is mounted on a surface 2090. In some embodiments, the tubular structures 1904 within the cluster 1904 extend substantially vertically from the surface 2090. In some embodiments, the surface 2090 comprises metal beams. In some embodiments, the cluster of inter-connected tubular structures 2004 is attached to the surface 2090, for example by welding or by attaching with screws.In some embodiments, one or more columns 2089 surround the cluster of inter-connected tubular structures 2004. In some embodiments, the one or more columns 2089 are configured to guide one or more weights, for example as shown in figure 20C. A potential advantage of one or more columns 2089 surrounding the cluster of inter-connected tubular structures 2004 is keeping the cluster of inter-connected tubular structures 2004 in place.

[0622] Referring now to Figure 20C, showing a schematic representation of a cluster of interconnected tubular structures, according to some embodiments of the invention. In some embodiments, an upper banister 20908 is positioned on the cluster of inter-connected tubular structures 2004. In some embodiments, weights (not shown in figure 59C) are distributed in the space defined by the upper banister 20908.

[0623] In some embodiments, one or more stackable weights 2010 are positioned on the surface 2090. In some embodiments, the one or more stackable weights 2010 are guided by the one or more columns 2089, which can have different lengths, for example, a stackable weight from the one or more stackable weights 2010 is placed on a taller column from the one or more columns 2089, before being guided onto a shorter column from the one or more columns 2089. A potential advantage is reducing the need for precise simultaneous alignment of the weight with multiple columns, thereby preventing potential misalignment or jamming.

[0624] Referring now to Figure 20D, 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 2004, shown in figure 59D from above, comprises a plurality of the tubular structures 1804. In some embodiment, each of the plurality of the tubular structures 1804 is covered by a dome shaped cover 20908 which seals each of the plurality of the tubular structures 1804. In some embodiments, each of the plurality of the tubular structures 1804 is fluidly connected to another tubular structure 1804 from the plurality of the tubular structure 1804, for example as shown in Figures 18F and 18G.

[0625] Exemplary energy storage device comprising a plurality of clusters of tubular structures Referring now to Figure 21, 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 2100 comprises a plurality of clusters of inter-connected tubular structures 2104. . 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 2104 is connected to local gas pipe 2192, which receives and provides gas to and from the cluster of interconnected tubular structures 2004. In some embodiments, each local gas pipe 2192 connects to a maingas pipe 2191, which communicates the plurality of clusters of inter-connected tubular structures 2104 to a turbomachinery unit (not shown in figure 21).

[0626] Exemplary energy storage device comprising horizontally positioned tubular structures.

[0627] Referring now to Figure 22, 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 2200 comprises the tubular structure 2204 positioned in a generally horizontal alignment relative to the seabed 2215. Potential advantages of the tubular structure 2204 positioned in a generally horizontal alignment relative to the seabed 2215 are the following:

[0628] • improved stability of the energy storage device 2200 due to low center of gravity, reducing susceptibility to displacement by underwater currents;

[0629] • enhanced load distribution, as the energy storage device 2200 footprint minimizes localized stress on the seabed;

[0630] • increased gas storage capacity, as the tubular structure 2204 can be designed with a greater length, facilitating high-volume gas storage;

[0631] • suitability for energy storage in shallow water reservoirs, where vertical configurations may be impractical due to depth constraints; and

[0632] • lower setup costs, as horizontal placement simplifies installation, anchoring, and maintenance.

[0633] In some embodiments, the tubular structure 2204 has a length 22102. In some embodiments, the length 22102 is from about 10 meters to about 100 meters, optionally from about 200 meters to about 1000 meters, optionally above 1000 meters.

[0634] In some embodiments the tubular structure 2204 is equipped with two covers 22104A and 22104B for enclosing the tubular structure 2204.

[0635] In some embodiments, the one or more air openings 2206 are positioned in a top part of the tubular structure 2204 for allowing gas release from the tubular structure 2204 and / or gas insertion to the tubular structure 2204.

[0636] In some embodiments, the tubular structure 2204 stores gas having a volume defined by a water level in the tubular structure 2204.

[0637] In some embodiments, in a steady-state condition, the tubular structure 2204 comprises compressed gas and water therein, wherein the water occupies a lower portion of the tubular structure 2204 and the compressed gas occupies a volume above the water level, thereby defining an interface between the compressed gas and the water within the tubular structure 2204. In some embodiments, during an energy storage phase, compressed gas is introduced into the tubular structure 2204, causing at least aportion of the water to exit the tubular structure 2204, for example through the one or more water openings 1896 and / or via the water exchange pipe 22108. In some embodiments, during an energy release phase, at least a portion of the compressed gas is withdrawn from the tubular structure 2204, for example toward the turbomachinery unit, thereby allowing water to enter into the tubular structure 2204, wherein the tubular structure 5602 is anchored to the seabed 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 2200.

[0638] In some embodiments, the compressed gas and the water within the tubular structure 2204 are in thermal communication at the interface defined by the water level. 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 2204 is influenced by surrounding seawater through the walls of the tubular structure 2204 and / or through the one or more water openings 1896, 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 2200. 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 2204 and / or movement of water into and / or out of the tubular structure 2204 during operation further contribute to thermal exchange.

[0639] In some embodiments, a water exchange pipe 22108 facilitates the controlled insertion and removal of water within the energy storage device 2200. In some embodiments, the water exchange pipe 22108 comprises an internal portion 22108A, which extends into the tubular structure 2204, and an external portion 22108B, which exits the tubular structure 2204 to connect with an external water source the energy storage device 2200 is positioned in. The internal portion 22108A is positioned to allow efficient water inflow and outflow to and from the energy storage device 2100. A potential advantage of water exchange pipe 22108 is preventing the one or more water openings 1896 from being clogged, for example due to mud sedimentation.

[0640] In some embodiments, the tubular structure 1804 is anchored to the seabed 1815 by one or more anchoring means (not shown in Figure 61), for example the anchoring means are foundations and / or weights.In some embodiments, the energy storage device 2100 is positioned in an artificial water reservoir, for example a lake.

[0641] In some embodiments, preparatory groundwork is performed before flooding the artificial water reservoir, to enhance the stability of the energy storage device 2100. In some embodiments, foundations are constructed within the ground to secure the tubular structure 2204, optionally shaped in a manner that enhances stability.

[0642] Alternatively or additionally, support platforms are constructed above the tubular structure 2204, optionally equipped with banisters, over which soil, rocks, or other stabilizing materials is deposited.

[0643] Exemplary energy storage device comprising a cluster of horizontally positioned tubular structures

[0644] Exemplary energy storage device comprising a cluster of generally parallel horizontally tubular structures

[0645] Referring now to Figures 23A-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 2300 comprises a cluster of the tubular structure 2304. In some embodiments, the cluster of the tubular structure 2304 are arranged such that the horizontally positioned tubular structures 2304 are generally parallel to one another.

[0646] In some embodiments, a plurality of connectors 2392 inter-connect the tubular structures 2304 in the cluster of tubular structures 2304. In some embodiments, the plurality of connectors 2392 allow transfer of water and gas between the cluster of tubular structure 2304, such that the cluster of tubular structure 2304 operate as one unit in terms of receiving and / or releasing of compressed gas.

[0647] Exemplary energy storage device comprising a cluster of stacked horizontally positioned tubular structures

[0648] Referring now to Figures 24A-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 2400 comprises a cluster of the tubular structure 2404. In some embodiments, the cluster of the tubular structure 2404 are arranged such that the horizontally positioned tubular structures 2404 are in a generally stack formation. In some embodiments, only the tubular structures 2404 positioned at the bottom of the stack of the cluster of the tubular structures 2404 include the one or more water openings 2496, allowing water to enter or exit the energy storage device 2400. In some embodiments, water can thenflow to the upper tubular structures 2404 via the plurality of connectors 24202. In some embodiments, the one or more water openings 2496 are connected to water pipes (not shown in Figure 24A-B).

[0649] Exemplary Configurations for Connecting Storage Tanks to a Main Gas Pipe

[0650] connections between a tank and a main

[0651] Referring now to Figure 25, 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.

[0652] The present inventors have found that connecting a storage tank 2504 or a plurality of storage tanks 2504 to a main gas pipe 2591 via one or more vertically oriented internal gas pipes 2592 provides a simple and cost-effective construction method while enabling efficient gas flow into and from the storage tank 2504. In some embodiments, the storage tank 2504 is configured for storing compressed gas in a gas volume located above a water level within the storage tank 2504. In some embodiments, the storage tank 2504 comprises one or more water openings 2596 positioned at a bottom part of the storage tank 2504 and configured to allow water from the surrounding environment to enter the storage tank 2504 as compressed gas is released, and to exit the storage tank 2504 as compressed gas is introduced, thereby maintaining internal pressure balance.

[0653] A potential advantage of connecting the storage tank 2504 or a plurality of storage tanks 2504 to a main gas pipe 2591 via one or more vertically oriented internal gas pipes 2592 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.

[0654] In some embodiments, the one or more vertically oriented internal gas pipes 2592 are made of for example, metal, polymer or a combination thereof.

[0655] In some embodiments, an energy storage device 2500 comprises the storage tank 2504. In some embodiments, the storage tank 2504 houses one or more vertically oriented internal gas pipes 2591, which are fluidly connected to the main gas pipe 2591. The main gas pipe 2591 is configured to supply and receive compressed gas, and is therefore connected at a first end 2591 A to a gas compressor (not shown in Figure 64) and at a second end 2591B to a turbomachinery unit configured for energy extraction (not shown in Figure 25).

[0656] In some embodiments, each of the one or more vertically oriented gas pipes 2592 extend from the main gas pipe 2591 into the interior of the storage tank 2504 and terminate at an upper opening 2592A, located within the storage tank 2504.

[0657] In some embodiments, the upper opening 2592A is equipped with a valve 25412, configured to permit gas flow into and from the storage tank 2504 while preventing water from entering the one or more vertically oriented gas pipes 2592.when compressed gas is supplied into the main gas pipe 2591, the compressed gas flows through the one or more vertically oriented gas pipes 2592 and enters the interior of the storage tank 2504 via the upper opening 2592A.

[0658] As compressed gas accumulates in the upper portion of the storage tank 2504, water is displaced and exits the storage tank 2504 through the one or more water openings 2596.

[0659] 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 2591. The pressure differential between the compressed gas stored in the storage tank 2504 and the main gas pipe 2591 causes the compressed gas to flow from the storage tank 2504, optionally through the valve 25412 at the upper opening 2592A, and into the gas pipe 2592. As gas exits the storage tank 2504, the resulting decrease in internal pressure in the storage tank 2504 causes water from the surrounding environment to enter the storage tank 2504 via the water openings 2596.

[0660] connections between a plurality of storage tanks and a main gas pipe Referring now to Figure 26, 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 2600 comprises a plurality of the energy storage devices 2500, each including the storage tank 2504 fluidly connected to the main gas pipe 2591 via the vertically oriented internal gas pipe 2592.

[0661] In some embodiments, the plurality of energy storage devices 2500 operates as one unit for purposes of receiving and releasing compressed gas, in which the plurality of energy storage devices 2400 is fluidly connected to the main gas pipe 2591 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 2500 and the main gas pipe 2591. Alternatively, in some embodiments, each of the energy storage devices 2500 is equipped with an individual valve (not shown in Figure 25), allowing selective charging or discharging of an energy storage device from the plurality of energy storage devices 2500.

[0662] Optionally, the energy storage device 2500 is equipped with a water removal unit 26502 fluidly connected to the main gas pipe 2591. In some embodiments, the water removal unit 26502 is configured to remove water that accumulate within the main gas pipe 2591 during operation.

[0663] In some embodiments, the water removal unit 26502 comprises a pump, a valve, or a combination thereof, configured to discharge water from the main gas pipe 2591 to the surrounding environment.

[0664] In operation, in the case that water obstructs the flow of compressed gas within the main gas pipe 2591, the water removal unit 26502 is activated to expel the water.Referring now to Figure 27, 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 2700 comprises a plurality of the storage tank 2504 which operates as one unit for purposes of receiving and releasing compressed gas.

[0665] In some embodiments, at least one storage tank from the plurality of storage tanks 2504 is fluidly connected to the main gas pipe 2591 via the one or more vertically oriented internal gas pipes 2592. In some embodiments, the remaining storage tanks 2504 are fluidly interconnected with one another via one or more tubes 26602 which allow gas flow between storage tanks 2504, optionally storage tanks 2504 which are adjacent to one another. A potential advantage of the one or more tubes 26602 interconnecting the storage tanks 2504 is enabling a cost-efficient manufacturing of the energy storage device 6600.

[0666] In some embodiments, each of the one or more tubes 26602 comprises two openings, in which each opening is positioned within a respective storage tank 2504. In some embodiments, each opening is equipped with the valve 25412 configured to prevent water from the storage tank 2504 from entering the tube 26602.

[0667] In some embodiments, the one or more tubes 27602 has a shape, for example a U shape, in which one “leg” of the tube 27602 is positioned within a first storage tank from the plurality of storage tanks 2504 and the other “leg” is positioned within a second storage tank from the plurality of storage tanks 2504. A potential advantage of the one or more tubes 27602 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 27602 substantially filled with compressed gas is critical for proper performance of the energy storage device 2700.

[0668] In some embodiments, at least one of the one or more tubes 27602 comprises a water removal unit 27604 positioned at a lower portion of the tube 27602. Tn some embodiments, the water removal unit 27604 comprises a pump, a valve, or a combination thereof, configured to remove water accumulated within the tube 27602 during operation.

[0669] The terms “comprises”, “comprising”, “includes”, “including”, “has”, “having” and their conjugates mean “including but not limited to”.

[0670] The term “consisting of’ means “including and limited to”.

[0671] The term “consisting essentially of’ means that the composition, method or structure may include additional ingredients, steps and / or parts, but only if the additional ingredients, steps and / or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.As used herein, the singular forms “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “a compound” or “at least one compound” may include a plurality of compounds, including mixtures thereof.

[0672] Throughout this application, embodiments of this invention may be presented with reference to a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as “from 1 to 6” should be considered to have specifically disclosed subranges such as “from 1 to 3”, “from 1 to 4”, “from 1 to 5”, “from 2 to 4”, “from 2 to 6”, “from 3 to 6”, etc.; as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0673] Whenever a numerical range is indicated herein (for example “10-15”, “10 to 15”, or any pair of numbers linked by these another such range indication), it is meant to include any number (fractional or integral) within the indicated range limits, including the range limits, unless the context clearly dictates otherwise. The phrases “range / ranging / ranges between” a first indicate number and a second indicate number and “range / ranging / ranges from” a first indicate number “to”, “up to”, “until” or “through” (or another such range-indicating term) a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numbers therebetween.

[0674] Unless otherwise indicated, numbers used herein and any number ranges based thereon are approximations within the accuracy of reasonable measurement and rounding errors as understood by persons skilled in the art.

[0675] In addition, any priority document(s) of this application is / are hereby incorporated herein by reference in its / their entirety.

Claims

WHAT IS CLAIMED IS:

1. A method for operating a thermal energy storage (TES) system comprising one or more tanks, the method comprising:a. storing a thermal storage liquid in one or more tanks; andb. selectively cycling 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 used to contain either cold or hot thermal storage liquid.

2. The method according to claim 1, wherein the selectively cycling comprises transferring cold thermal storage liquid from at least one tank to a first heat exchanger for absorbing heat from compressed gas during gas compression.

3. The method according to claim 1 or claim 2, wherein the selectively cycling comprises transferring hot thermal storage liquid from at least one tank to a second heat exchanger for transferring heat to compressed gas prior to expansion in a turboexpander.

4. The method according to any one of claims 1-3, wherein storing a thermal storage liquid comprising storing at a pressure greater than the vapor pressure of the thermal storage liquid at an operating temperature.

5. The method according to any one of claims 1-4, wherein the storing comprising providing compressed gas above the thermal storage liquid to exert the pressure.

6. The method according to any one of claims 1-5, wherein storing the thermal storage liquid comprises maintaining at least one of the one or more tanks in an empty state.

7. The method according to any one of claims 1-6, wherein the selectively cycling comprises coordinating the discharge of thermal storage liquid from one tank simultaneously with the filling of another tank with thermal storage liquid.

8. An energy storage system comprising: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 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.

9. The system according to claim 8, wherein the thermal storage liquid is water.

10. The system according to claim 8 or claim 9, 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.

11. 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; 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.

12. The system according to claim 11, wherein the at least one environmental heat exchanger is configured to transfer heat from the waterbody surrounding the underwater compressed gas storage devices.

13. The system according to claim 11 or claim 12, wherein the at least one environmental heat exchanger is configured to transfer heat from an industrial heat source.

14. The system according to any one of claims 11-13, wherein the at least one environmental heat exchanger is configured to transfer heat from a geothermal source.

15. The system according to any one of claims 11-14, wherein the thermal energy storage (TES) comprises one or more tanks configured to contain a thermal storage liquid, the one or more tanks being selectively connected to the one or more first heat exchangers and / or the one or more second heat exchangers.

16. The system according to any one of claims 11-15, wherein at least one of the one or more tanks is configured to store cold thermal storage liquid, and is configured to store hot thermal storage liquid.

17. The system according to any one of claims 11-16, wherein at least one tank 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 for preventing boiling and phase transition of the hot thermal storage liquid into vapor.

18. The system according to any one of claims 11-17, further comprising a controller configured to selectively regulate operation of the one or more first heat exchangers, the one or more second heat exchangers, and the at least one environmental heat exchanger based on at least one of: temperature of the compressed gas, availability of environmental heat, and amount of heat stored in the TES.

19. The system according to any one of claims 11-18, wherein the one or more turboexpanders comprise a plurality of turboexpanders arranged in series to facilitate multi-stage expansion of the compressed gas.

20. The system according to any one of claims 11-19, further comprising at least one intermediate heat exchanger positioned between two of the plurality of turboexpanders, the intermediate heat exchanger being configured to transfer heat from the TES and / or an environmental heat source to the compressed gas between expansion stages.

21. The system according to any of claims 11-20, comprising at least one shared heat exchanger, configured to function both as at least one of the one or more first heat exchangers and as at least one of the one or more second heat exchangers.

22. The system according to claim 21, comprising at least one switching valve configured to selectively direct flow of compressed gas either (i) from the one or more compressors toward the one or more underwater compressed gas storage devices during a compression mode, or (ii) from the one or more underwater compressed gas storage devices toward the one or more turboexpanders during a generation mode.

23. The system according to any of claims 21-22, comprising at least one additional switching valve configured to selectively direct thermal storage liquid from either (i) at least one tank containing cold thermal storage liquid or (ii) at least one tank containing hot thermal storage liquid to the at least one shared heat exchanger.

24. The system according to any one of claims 21-23, further comprising at least one second additional switching valve configured to selectively direct thermal storage liquid exiting the at least one shared heat exchanger to either (i) at least one tank containing hot thermal storage liquid or (ii) at least one tank containing cold thermal storage liquid.

25. The system according to claim 24, further comprising a controller configured to actuate the switching valve, the additional switching valve and the second additional switching valve such that, in a compression mode, compressed gas flows toward the underwater compressed gas storage devices while cold thermal storage liquid flows to the shared heat exchanger and returns to at least one tank containing hot thermal storage liquid, and, in a generation mode, compressed gas flows toward the one or more turboexpanders while hot thermal storage liquid flows to the shared heat exchanger and returns to at least one tank containing cold thermal storage liquid.

26. The system according to any one of claims 11-25, further comprising at least one additional heat exchanger positioned downstream of a last one of the one or more turboexpanders and configured to cool a thermal storage liquid using expanded compressed gas to produce extra-cooled thermal storage liquid.

27. The system according to claim 26, further comprising at least one tank configured to store the extra-cooled thermal storage liquid.

28. The system according to any one of claims 26-27, further comprising at least one heat exchanger positioned downstream of a last one of the one or more compressors and configured such that the extra-cooled thermal storage liquid flows therethrough to cool compressed gas and induce condensation of at least a portion of moisture contained in the compressed gas.

29. The system according to claim 28, comprising a water trap configured to collect condensed liquid separated from the compressed gas, wherein the water trap is positioned in one or both:(a) within the at least one heat exchanger; and(b) along a conduit between an outlet of the at least one heat exchanger and an inlet of the one or more underwater compressed gas storage devices.

30. The system according to any one of claims 11-29, wherein the one or more underwater compressed gas storage devices comprise a plurality of underwater compressed gas storage tanks.

31. The system according to any one of claims 11-29, wherein the one or more underwater compressed gas storage devices comprise a plurality of underwater compressed gas storage tanks.

32. The system according to claim 31, wherein the plurality of underwater compressed gas storage tanks are arranged in one or more of:a stacked configuration;a clustered configuration; anddistributed along a seabed slope.

33. The system according to any of claims 31-32, wherein the plurality of underwater compressed gas storage tanks are positioned at substantially a same height on a seabed.

34. The system according to any of claims 31-32, wherein the plurality of underwater compressed gas storage tanks are positioned at different heights.

35. The system according to any one of claims 31-34, wherein the plurality of underwater compressed gas storage tanks are in fluid communication with one another such that the plurality of tanks operate as one unit for receiving and releasing compressed gas.

36. The system according to any one of claims 11-35, wherein at least one of the one or more underwater compressed gas storage devices comprises an elongated polymer conduit configured to store compressed gas.

37. The system according to claim 36, further comprising one or more anchors mounted on the elongated polymer conduit and configured to counteract buoyancy and to submerge the elongated polymer conduit toward a seabed.

38. The system according to claim 36 or 37, wherein the elongated polymer conduit is at least partially encased in concrete cast around the elongated polymer conduit to form the one or more anchors.

39. The system according to any one of claims 36-38, further comprising at least one steel cable extending along at least a portion of the elongated polymer conduit and coupled to the one or more anchors.

40. An energy storage system, comprising:a. one or more underwater compressed gas storage tanks positioned at a depth in a waterbody and configured to store compressed gas;b. a thermal energy storage (TES) assembly positioned above water and comprising one or more tanks configured to contain thermal storage liquid in hot or cold states; andd. a controller configured to determine heat requirements for heating the compressed gas prior to expansion based on a depth of the one or more underwater compressed gas storage tanks and to selectively control heat transfer from the TES assembly and / or via at least one environmental heat exchanger.

41. The system according to claim 40, wherein the controller is configured to calculate a temperature difference between (i) the temperature of the waterbody at the depth of the one or more underwater compressed gas storage tanks, and (ii) the temperature of the cold thermal storage liquid in the TES assembly.

42. The system according to claim 40 or claim 41, wherein the controller is configured to activate the at least one environmental heat exchanger to further cool the cold thermal storage liquid when the calculated temperature difference exceeds a predefined threshold.

43. The system according to any one of claims 40-42, wherein the controller is configured to regulate operation of the at least one environmental heat exchanger to reduce the temperature of the thermal storage liquid to a level proximate to the temperature of the surrounding waterbody.

44. The system according to any one of claims 40-43, further comprising at least one environmental heat exchanger positioned in the waterbody and configured to transfer heat from the waterbody to thermal storage liquid flowing through the one or more conduits.

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