Underwater energy harvesting drone and method of operation

Abstract

The present invention relates to an underwater energy harvesting drone and a method of operating the same. The underwater energy harvesting drone has a main housing submerged in seawater and a plurality of thermoelectric modules, each of the plurality of thermoelectric modules having a first operating interface in thermal contact with the main housing. A heat transfer element is in contact with a second operating interface on the plurality of thermoelectric modules and a power storage device is connected to the plurality of thermoelectric modules. The configuration of the submerged main housing that establishes a thermal gradient between the main housing and the heat transfer element enables power to be generated by the thermoelectric modules, thereby charging the power storage device.

Description

Technical Field

[0001]

[0013] The embodiments shown in this disclosure relate generally to an unmanned underwater vehicle (UUV), and more particularly, to a UUV that employs a thermoelectric system to generate electrical power using temperature differences in the environment in which the UUV operates. Background Art

[0002] UUVs are used for a variety of missions including seafloor exploration, environmental monitoring, and security operations. The operational profile of UUVs results in limited refueling capabilities and requirements. The deep sea is an ideal environment for covert military operations. Such operations often rely on UUVs to complete combat and reconnaissance missions.

[0003] Some prior art UUVs use thermal gradients in the ocean's thermoclimatic layer to generate energy or achieve a propulsion effect. However, the thermoclimatic layer asymptotically approaches a temperature of about 3.5 degrees Celsius below about 1,000 meters. Therefore, UUVs that rely on gradients in the thermoclimatic layer lack energy in deep-sea environments. Therefore, UUVs must frequently surface to increase their visibility, placing the UUVs at potential risk of collision with ships in the water or interruption of their course. Summary of the invention

[0004] An exemplary embodiment provides an underwater energy harvesting drone having a main housing immersed in seawater and a plurality of thermoelectric modules, each of the plurality of thermoelectric modules having a first operational interface in thermal contact with the main housing. A heat transfer element is in contact with a second operational interface on the plurality of thermoelectric modules, and a power storage device is connected to the plurality of thermoelectric modules. The configuration of the submerged main housing establishes a thermal gradient between the main housing and the heat transfer element to induce power generation by the thermoelectric modules, thereby charging the power storage device.

[0005] Exemplary embodiments allow for a first method for operating an unmanned underwater vehicle (UUV) in which cold seawater is delivered to an internal storage tank at a first location. The internal storage tank is then placed at a second location to store the cold seawater. The UUV is navigated to a hydrothermal outlet location, placing the main hull in a "hot zone" compared to the surrounding seawater. Electricity is generated using a thermoelectric module based on a thermal gradient between the main hull and the internal storage tank to charge a power storage device.

[0006] The exemplary embodiment allows for a second method for operating an unmanned underwater vehicle (UUV), wherein the submerged UUV surfaces to expose a heat sink to air. The thermoelectric module is operated to provide generated electrical energy for charging a power storage device using a temperature difference between a main housing submerged in seawater and a heat sink in convective contact with air. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The features, functions, and advantages that have been discussed can be achieved independently of each embodiment or in combination with yet other embodiments, further details of which can be seen with reference to the following description and drawings.

[0008] Figure 1A is a diagrammatic representation of a UUV employing a first exemplary embodiment as described herein;

[0009] Figure 1B is a diagrammatic representation of a UUV employing a second exemplary embodiment as described herein;

[0010] Figure 2A yes Figure 1A A front sectional view of an embodiment of the present invention;

[0011] Figure 2B is a front cross-sectional view of a structural alternative to the first embodiment having a rectangular shape;

[0012] Figure 3 is a schematic side sectional view of a first embodiment;

[0013] Figure 4 is a side view of the first embodiment in a "pogo" orientation;

[0014] Figure 5 is a block diagram of an exemplary control system having navigation and sensing components;

[0015] Figure 6 is a schematic side sectional view of a second embodiment;

[0016] Fig. 7A , Figure 7B ,as well as Figure 7C is a graphical representation of the sequence of operations of the second embodiment;

[0017] Fig. 8A is a side view of a structural alternative of the second embodiment;

[0018] Figure 8B is a schematic side cross-sectional view of an alternative embodiment of the second embodiment;

[0019] Fig. 9 is a flowchart illustrating a first method of power generation of the first embodiment; and

[0020] Fig.10 : is a flowchart showing a second method of generating electric power according to the second embodiment. DETAILED DESCRIPTION

[0021] Exemplary embodiments of the UUV described herein provide an underwater energy harvesting drone (UEHD), more generally described as an energy harvesting underwater vehicle, having a submerged main housing in thermal contact with a first operational interface on a plurality of thermoelectric modules, and a heat transfer element in contact with a second operational interface on the plurality of thermoelectric modules, whereby the UEHD is configured to establish a thermal gradient between the main housing and the heat transfer element, enabling the thermoelectric modules to generate electricity.

[0022] With reference to the accompanying drawings, Figure 1A A first embodiment of a UEHD 10 is shown. The UEHD 10 has a main housing 12 and is maneuvered (e.g., navigated) in a marine environment using thrusters 13 (illustratively shown as standard multi-blade screws) and a control panel 14 (e.g., a steering rudder or hydraulic control surface) pivotally connected to the main housing 12 for controlling the direction of the UEHD 10. Figure 2A As can be seen in the figure, an internal storage tank 16 (which may be filled with cold seawater as described later) is used as a heat transfer element. In the illustrated embodiment, the internal storage tank 16 is substantially concentric within the main housing 12, and a plurality of thermoelectric modules 18 are mounted between the internal storage tank 16 and the main housing 12, with a first operating surface 20 on each thermoelectric module 18 in thermal contact with the main housing 12 and a second operating surface 22 in thermal contact with the internal storage tank 16. The thermoelectric modules may be selected from at least one of a Pearl junction device (Seebeck, Thompson effect) and a Stirling engine. The temperature difference between the main housing 12 and the internal storage tank 16 will provide a thermal gradient for the operation of the thermoelectric modules 18.

[0023] In the central cross section shown, Figure 2A The UEHD in is basically circular. Figure 2B An exemplary alternative embodiment is shown in FIG, wherein the central cross-section is rectangular in shape and the main housing 12' and the internal storage box 16' have rectangular cross-sections. Thermoelectric modules 18 are mounted intermediate the flat side 17 of the storage box 16' and the inner flat side 19 of the main housing 12' to achieve the desired thermal gradient.

[0024] from Figure 3As seen in FIG. 1 , the main housing 12 houses electric motors 24 for the thrusters 13 and a control system 26 for operation and navigation of the UEHD 10. Specifically, the control system 26 operates the thrusters 13 and one or more control panels 14 to propel and navigate the UEHD 10 through the water. A power storage device 28 (which may be a rechargeable battery including a single cell element, a storage battery pack such as lithium ion, lithium ion polymer, nickel cadmium, nickel metal hydride, lead acid, or a capacitive storage system such as a nanotechnology supercapacitor) is connected to the thermoelectric module 18 and the electric motor 24 through a transformer circuit 30. Power for the control system 26 may also be provided from the power storage device 28.

[0025] Figure 3 The exemplary embodiment shown in has an air inlet 32 ​​and an air outlet 34 connecting the internal storage tank 16 with seawater outside the main hull 12. The air inlet 32 ​​and the air outlet 34 can be retractable or integrated gates for open and closed positions to allow selective fluid communication with the external seawater. A pump 36 powered by the power storage device 28 can be used to pump water from the air inlet 32 ​​into the internal storage tank 16 and discharge water from the air outlet 34 to replace the water in the internal storage tank. Alternatively, the air inlet 32 ​​and the air outlet 34 can be opened to the seawater outside the UEHD 10 underway, allowing the dynamic pressure of the water to form a water flow through the internal storage tank 16. When the air inlet 32 ​​and the air outlet 34 are in the closed position, the cold seawater delivered to the internal storage tank 16 is stored.

[0026] In operation, the UEHD 10 is autonomously or remotely navigated by the control system 26 to the location of a hydrothermal vent near the seafloor according to a navigation profile (including part of the mission / operation profile). The geographical distribution of the hydrothermal vent field is currently throughout the world's oceans. The thermal vent produces a hot water plume with a temperature range of 60° to 646°C. When the UEHD 10 is located in open water, the air inlet 32 ​​and the air outlet 34 are deployed or opened at a first position of the internal storage tank 16 and cold seawater is delivered to the internal storage tank 16, which is then maintained by closing the air inlet 32 ​​and the air outlet 34, while the internal storage tank 16 is placed in a second position to store cold seawater. The UEHD can be as low as 12°C to 4°C or lower at a depth of 500 meters and below. The UEHD 10 is then navigated by the control system 26 to position the main housing 12 in the hydrothermal outlet and to hover in the outlet's thermal plume or follow the outlet's plume stream while maintaining the main housing 12 in the "hot zone" compared to the surrounding seawater and maintaining the initial temperature of the water stored in the internal storage tank 16. The temperature difference between the thermal plume in convective and conductive thermal contact with the main housing 12 and the cold water stored in the internal storage tank 16, which acts as a thermal capacitor, provides a thermal gradient for the operation of the thermoelectric module 18, which generates electricity to charge the power storage device 28. The operation of the thermoelectric module heats the water in the internal storage tank 16. When the temperature difference between the external outlet plume and the internal storage tank decreases to a point where generation of effective electricity by the thermoelectric module ceases, the UEHD 10 is maneuvered by the control system 26 into open water and the internal storage tank 16 is drained and refilled by operation of the air inlet 32 ​​and the air outlet 34. The UEHD 10 may then be reconfigured within the outlet plume or moved to a different outlet plume as needed for recharging of the power storage device 28. Between charging cycles, the UEHD 10 may be operated by the control system 26 on its intended mission profile.

[0027] Alternatively, the thermal gradient is reversed by navigating the UEHD 10 into the plume of the hot outlet and opening the air inlet 32 ​​and the air outlet 34 to deliver hot water from the plume. The UEHD 10 is then navigated into open cold seawater by the control system 26, and the temperature difference between the cold seawater in convective and conductive thermal contact with the main housing 12 and the hot water from the plume stored using the internal storage tank 16 acting as a thermal capacitor provides a reverse thermal gradient for operation of the thermoelectric module 18, which generates electricity to charge the power storage device 28. The transformer circuit 30 may be adapted to sense the reverse heat flow generated by the thermoelectric module based on the reverse thermal gradient and provide rectification for charging the power storage device 28. Operation of the thermoelectric module will produce cooling of the water in the internal storage tank 16. When the temperature difference between the internal storage tank and the external seawater in contact with the main housing 12 decreases to a point where the effective power generated by the thermoelectric module ceases, the UEHD 10 is manipulated back to the hot air outlet by the control system 26, and the internal storage tank 16 is drained and refilled by operation of the air inlet 32 ​​and the air outlet 34.

[0028] The system provided in the UEHD 10 allows "surfing" between hydrothermal vents to provide recharging of the power storage device 28 to achieve substantially uninterrupted operation on the mission profile. As described, the mission (e.g., operation) profile can include activities such as exploration, environmental monitoring, and security operations.

[0029] Depending on the size of the UEHD 10 and other considerations, a directional ballast tank 36 with appropriate control valves 40 and a pump or other ventilation system (including the use of a pump 36 in the exemplary embodiment) may be used to vary the ballast of the UEHD 10 to selectively adjust the ballast weight of the UEHD 10. Figure 4 The vertical or "pogo" orientation shown. If the internal storage tank 16 has been filled with cold seawater, the UEHD 10 can then be maneuvered into the hydrothermal outlet plume 42 and reconfigured to the pogo position by filling the ballast tanks 38 so that the main hull 12 is more exposed to the outlet plume. Once the thermoelectric charging cycle is completed or the temperature differential in the internal storage tank 16 is exhausted, the water is drained from the ballast tanks 38 and the UEHD 10 is redirected to its normal operating orientation to provide normal cruising capabilities. If a negative temperature differential between the main hull 12 and the internal storage tank 16 is used for the charging cycle, the pogo orientation can also be used to assist in filling the internal storage tank 16 with water from the plume.

[0030] from Figure 5As seen in FIG. 1 , the control system 26 incorporates a navigation system 502 that may be preloaded with a specific mission (e.g., operating) profile 503 for autonomous operation using input from a global positioning system (GPS) 504 or GPS sensor, an inertial navigation (e.g., guidance) system 506, or a comparative navigation element, or may be remotely controlled using a communication module 508 and a remote control system 509. Artificial intelligence (AI) may be integrated into a control processor 510 for maneuvering or wandering within specified parameters in a mission profile. Control signals for physical control of the UEHD 10 by the control system 26 are provided by a motor controller 512 connected to the motor 24 and a control panel actuation system 514 connected to the control panel 14.

[0031] Figure 1B A second embodiment of a UEHD 110 is shown. As with the first embodiment, the UEHD 110 has a main housing 112 and is maneuvered in a marine environment using a propeller 113 (illustratively shown as a standard multi-blade screw) and a control panel 114. The heat transfer element of the second embodiment is a heat sink 116 mounted to and extending from a top surface 117 of the main housing 112. The heat sink 116 can be telescopically expanded to increase the surface area. Figure 6 As seen in FIG. 1 , the main housing 112 houses electric motors 124 for the thrusters 113 and a control system 126 for operation of the UEHD 110. A power storage device 128 is connected to the thermoelectric modules 118 and the electric motors 124 through a transformer circuit 130, and the power storage device 128 may be a single battery element, a storage battery pack such as lithium ion, lithium ion polymer, nickel cadmium, nickel metal hydride, lead acid, or a capacitive storage system such as a nanotechnology supercapacitor. Power for the control system 126 may also be provided from the power storage device 128. The thermoelectric modules 118 are connected to a first operating surface 120 and a second operating surface 122 on each thermoelectric module 118, the first operating surface 120 being in thermal contact with the main housing 112, and the second operating surface 122 being in thermal contact with the heat sink 116.

[0032] In such FIG. 7A to FIG. 7C In operation of the second embodiment shown, the UEHD 110 operates in accordance with a mission profile established by the control system 126. Fig. 7A Cruising under submerged conditions as shown. The intended operation of the second embodiment occurs in arctic waters where the sea temperature is relatively constant (at least -2°C or warmer) and the air temperature (particularly at night) is significantly cold (approximately -20°C, but ranging from about -60° to -10°C). Figure 7BAs shown, when the power storage device 128 needs to be charged, the control system 126 causes the UEHD 110 to surface so that the heat sink 116 is selectively exposed to the air from the seawater. The temperature difference between the main housing 112 immersed in the seawater 140 and the heat sink 116 in convective contact with the surrounding air 142 is significant and sufficient for the operation of the thermoelectric module 118 to provide the generated electrical energy for charging the power storage device. Figure 7C As seen in FIG. 1 , once charging is complete or operation is otherwise required, the control system 126 causes the UEHD 110 to be submerged to continue operation.

[0033] Each ballast tank and associated operating system that provides the disclosed embodiments of the UEHD for driving, surfacing, and depth control of desired operating depths are well known in the art and are not described herein.

[0034] Fig. 8A and Figure 8B An alternative structural arrangement of the second embodiment is shown in FIG. Fig. 8A As seen in FIG. 1 , UEHD 210 incorporates a main housing 212 having an upper portion 212a and a lower portion 212b separated by an insulating barrier 213. Although housing portions 212a, 212b are shown as being symmetrically located above and below insulating barrier 213, an asymmetrical arrangement may be employed. Figure 8B 2, the thermoelectric modules 218 are joined with a first operating surface 220 and a second operating surface 222 on each thermoelectric module 218, the first operating surface 220 being in thermal contact with the upper portion 212a, and the second operating surface 222 being in thermal contact with the lower portion 212b. A heat transfer plate 214 or other thermally conductive element may be employed for effective contact between the second operating surface 222 and the lower portion 212b, or conversely, for effective contact between the first operating surface 220 and the upper portion 212a. As in the first structural arrangement, the UEHD 210 incorporates a power storage device 228, a transformer circuit 230, a motor 224, and a control system 226. The UEHD 210 operates in a similar manner to the UEHD 110, with the upper portion 212a of the main housing 212 exposed to air being a heat sink.

[0035] With any of the structural arrangements of the second embodiment, if the air temperature is hotter than the water temperature, the heat transfer of the UEHD 110, 210 through the thermoelectric modules 118, 218 can be reversed, thereby providing a reverse thermal gradient. When a reverse temperature gradient occurs, the direction of the current generated by the thermoelectric modules 118, 218 is reversed. The reverse current is captured using a diode circuit within the transformer circuit 130, 230 and the charge is then stored in the power storage device 128, 228.

[0036] The disclosed embodiments of the UEHD provide methods for operation of a UUV. Fig. 9 As shown (reference Figure 1A and Figure 3 ), at step 902, the UEHD 10 is automatically or remotely navigated by the control system 26 between the locations of the hydrothermal vents near the seafloor.

[0037] In the first sequence, when the UEHD 10 is located in open water, in step 904, in a first position, the air inlet 32 ​​and the air outlet 34 are deployed or placed in an open position, and cold seawater is delivered to the internal storage tank 16 by pumping or dynamic pressure, and then, in step 906, the air inlet 32 ​​and the air outlet 34 are closed, thereby placing the internal storage tank 16 in a second position to store cold seawater. In step 908, the UEHD 10 is navigated to the hydrothermal outlet position by the control system 26 and the main hull 12 is caused to hover in the hot plume of the outlet or follow the outlet plume steam flow to maintain the main hull 12 in the "hot zone" compared to the surrounding seawater and maintain the initial temperature of the water in the internal storage tank 16. In step 910, the directional ballast tanks 38 can be filled to orient the UEHD 10 in the pogo position. Similarly, the directional ballast tanks 38 are filled to orient the UEHD in the pogo position. At step 912, the temperature difference between the heat plume in convective and conductive thermal contact with the main housing 12 and the cold water stored in the internal storage tank 16 using the thermal capacitor provides a thermal gradient for the thermoelectric module 18 operating based on the thermal gradient between the main housing and the internal storage tank to generate electricity for charging the power storage device 28. At step 914, the UEHD 10 is maneuvered to open water by the control system 26, and at step 904, the internal storage tank 16 is drained and refilled by the operation of the air inlet 32 ​​and the air outlet 34 to repeat the first sequence of processes.

[0038] In a second sequence, in step 911, the directional ballast tanks 38 may be filled while the UEHD 10 is in the outlet plume, thereby orienting the UEHD 10 in a pogo position. In step 905, in a first position, the air inlet 32 ​​and the air outlet 34 are deployed and opened and hot water is transferred from the plume to the internal storage tank 16 by pumping or dynamic pressure, and then, in step 907, the air inlet 32 ​​and the air outlet 34 are closed, thereby placing the internal storage tank 16 in a second position (e.g., rotated relative to the pogo position) to store hot water. In step 909, the UEHD 10 is navigated by the control system 26 outside the outlet plume and onto the open ocean, where the cold water provides a negative temperature difference relative to the initial temperature of the hot water in the internal storage tank 16. In step 913, the temperature difference between the cold open seawater in convective and conductive thermal contact with the main shell 12 and the hot water stored in the internal storage tank 16 used as a thermal capacitor provides a thermal gradient and operates the thermoelectric module 18 based on the thermal gradient between the main shell and the internal storage tank to generate electricity for charging the power storage device 28. In step 915, the UEHD 10 is manipulated back to the hydrothermal outlet plume by the control system 26, and in step 905, the internal storage tank 16 is drained and refilled by operation of the air inlet 32 ​​and the air outlet 34 to repeat the process in the second sequence. Then, through any sequence, in step 916, the UEHD can be operated in the desired mission profile with respect to navigation and operating the thermoelectric module (18, 118, 218) to charge the power storage device (28, 128, 228). Starting from steps 904, 905, the UEHD 10 can be reconfigured in the outlet plume or moved to a different outlet plume as needed to recharge the power storage device 28.

[0039] like Fig.10 As shown (reference Figure 1B , Figure 6 ,as well as Fig. 8A and Figure 8B ), in step 1002, the submerged UEHD 110, 210 is operated on a mission profile directed by the control system 126. In step 1004, when the power storage device 128 needs to be charged, the control system 126 causes the UEHD 110, 210 to surface to expose the heat sink 116, 212a to the air. In step 1006, the thermoelectric module 118 operates to provide the electrical energy generated when the power storage device is charged using the temperature difference between the main housing 112 (or 212b) submerged in the seawater 140 and the heat sink 116, 212a in convective contact with the surrounding air 142. In step 1008, once charging is completed or when operated in other ways as needed, the control system 126 causes the UEHD 110 to continue to operate submerged.

[0040] Further, the present disclosure includes embodiments according to the following items:

[0041] Item 1. An underwater energy collection drone, comprising: a main shell submerged in seawater; a plurality of thermoelectric modules, each of the plurality of thermoelectric modules having a first operating interface in thermal contact with the main shell; a heat transfer element in contact with a second operating interface on the plurality of thermoelectric modules; and a power storage device connected to the plurality of thermoelectric modules; wherein the configuration of the main shell for establishing a thermal gradient between the main shell and the heat transfer element enables power to be generated by the thermoelectric modules, thereby charging the power storage device.

[0042] Item 2. An underwater energy harvesting drone according to Item 1, wherein the power storage device includes at least one of a rechargeable battery and a capacitor.

[0043] Item 3. An underwater energy harvesting drone according to Item 2, wherein the battery is one of lithium-ion, lithium-ion polymer, nickel-cadmium, nickel-metal hydride, and lead-acid batteries.

[0044] Item 4. An underwater energy harvesting drone as described in Item 2, wherein the capacitor comprises a nanotechnology supercapacitor.

[0045] Item 5. An underwater energy harvesting drone according to Item 1, wherein the thermoelectric module includes at least one of a Peltier junction device and a Stirling engine.

[0046] Item 6. The underwater energy harvesting drone according to Item 1 also includes: an electric motor connected to receive power from a power storage device; a thruster driven by the electric motor; a control panel coupled to the main housing; and a control system suitable for providing control signals to the electric motor and the control panel according to a navigation profile.

[0047] Item 7. An underwater energy harvesting drone as described in Item 6, wherein the heat transfer element includes an internal storage tank adapted to receive cold seawater at a first location and store the cold seawater at a second location, and the navigation profile configures the main housing in a thermal plume of a hydrothermal outlet.

[0048] Item 8. An underwater energy harvesting drone according to Item 7, wherein the internal storage box includes an air inlet and an air outlet, and the air inlet and the air outlet have an open position for a first position of the internal storage box and a closed position for placing the internal storage box in a second position.

[0049] Item 9. The underwater energy harvesting drone of Item 7, further comprising a ballast tank adapted to be selectively induced into a pogo position of the main hull.

[0050] Item 10. An underwater energy harvesting drone according to Item 7, wherein, when the navigation profile positions the main housing in the thermal plume, the internal storage tank is also suitable for receiving hot water from the thermal plume of the hydrothermal outlet at a first position, and when the navigation profile configures the main housing in cold seawater, the internal storage tank is also suitable for storing hot water at a second position, thereby reversing the thermal gradient used to operate the thermoelectric module to generate electricity for charging the power storage device, and the transformer circuit is suitable for sensing the reverse current generated by the thermoelectric module based on the reverse thermal gradient and providing rectification for charging the power storage device.

[0051] Item 11. An underwater energy harvesting drone as described in Item 6, wherein the heat transfer element includes a radiator mounted to and extending from the top surface of the main housing, and the navigation profile causes the main housing to selectively surface to expose the radiator from the sea water.

[0052] Item 12. An underwater energy harvesting drone according to Item 6, wherein the main shell includes an upper portion and a lower portion, the upper portion and the lower portion are separated by an insulating partition, wherein the upper portion includes a heat transfer element and the navigation profile enables the main shell to selectively float to the surface to expose the upper portion from the sea water.

[0053] Item 13. A method for operating an unmanned underwater vehicle (UUV), comprising the steps of: delivering cold seawater to an internal storage tank at a first location; placing the internal storage tank at a second location to store the cold seawater; navigating the UUV to a hydrothermal outlet location, placing the main hull in a "hot zone" of the outlet plume relative to the surrounding seawater; and generating electricity using a thermoelectric module based on a thermal gradient between the main hull and the internal storage tank to charge a power storage device.

[0054] Item 14. The method of Item 13, further comprising: filling a directional ballast tank to orient the UUV in a pogo position.

[0055] Item 15. The method of Item 13, further comprising the steps of: maneuvering to open water; draining the internal storage tank; and refilling the internal storage tank by operating the air inlet and the air outlet.

[0056] Item 16. The method of Item 13, further comprising: operating the UUV in a desired mission profile.

[0057] Item 17. The method of Item 16, further comprising: reconfiguring within the outlet plume and moving to a different outlet plume for recharging the power storage device.

[0058] Item 18. A method of operating an unmanned underwater vehicle (UUV), comprising: surfacing to expose a heat sink to the outside air; and operating a thermoelectric module to use the temperature difference between a main shell immersed in seawater and a heat sink in convection contact with the outside air to provide generated electrical energy for charging a power storage device.

[0059] Item 19. The method of Item 18, further comprising: immersing the UUV upon completion of charging.

[0060] Item 20. The method according to Item 18 further comprises: immersing the mission profile operation directed by the control system.

[0061] Having now described in detail each embodiment required by the patent statutes, those skilled in the art will recognize variations and substitutions to the specific embodiments disclosed herein. Such variations are within the scope and intent of the invention as defined by the following claims.

Claims

1. An underwater energy harvesting drone (10, 110, 210), comprising: The main housing (12, 112, 212) is submerged in seawater; A plurality of thermoelectric modules (18, 118, 218), each of the plurality of thermoelectric modules having a first operating interface (20, 120, 220) in thermal contact with the main housing; A heat transfer element (16, 116, 212a) in contact with a second operating interface (22, 122, 222) on the plurality of thermoelectric modules; as well as a power storage device (28, 128, 228) connected to the plurality of thermoelectric modules; wherein the configuration of the main housing for establishing a thermal gradient between the main housing and the heat transfer element induces generation of power by the thermoelectric modules to charge the power storage device, an electric motor (24, 124, 224) connected to receive power from the power storage device; a propeller (13, 113), driven by the electric motor; a control panel (14, 114) coupled to the main housing; and a control system (26, 126, 226) adapted to provide control signals to the motor and the control panel to position the main housing in a thermal plume of a hot liquid outlet according to a navigation profile, The heat transfer element comprises an internal storage tank (16) adapted to receive cold seawater at a first location and store the cold seawater at a second location.

2. The underwater energy harvesting drone according to claim 1, wherein: The power storage device includes at least one of a rechargeable battery and a capacitor.

3. The underwater energy harvesting drone according to claim 2, wherein: The battery is one of a lithium ion, lithium ion polymer, nickel cadmium, nickel metal hydride, and lead acid battery.

4. The underwater energy harvesting drone according to claim 2, wherein: The capacitor comprises a nanotechnology supercapacitor.

5. The underwater energy harvesting drone according to claim 1, wherein: The thermoelectric module includes at least one of a Peltier junction device and a Stirling engine.

6. The underwater energy harvesting drone according to claim 1, wherein: The internal storage box includes an air inlet (32) and an air outlet (34), the air inlet and the air outlet having an open position for the first position of the internal storage box and a closed position for placing the internal storage box in the second position.

7. The underwater energy harvesting drone of claim 1, further comprising a ballast tank (38) adapted to selectively induce a pogo position of the main hull.

8. The underwater energy harvesting drone according to claim 1, wherein: The internal storage tank is further adapted to receive hot water from the hot plume of the hydrothermal outlet at the first position when the navigation profile positions the main housing in the hot plume, and to store the hot water at the second position when the navigation profile positions the main housing in the cold seawater, thereby inducing a reversal of the thermal gradient for operating the thermoelectric module to generate power for charging the power storage device, and the transformer circuit (30) is adapted to sense a reverse current generated by the thermoelectric module based on the reverse thermal gradient and provide rectification for charging the power storage device.

9. The underwater energy harvesting drone according to claim 1, wherein: The heat transfer element includes a heat sink (116) mounted to and extending from a top surface (117) of the main housing, and the navigation profile causes the main housing to selectively surface to expose the heat sink from seawater.

10. The underwater energy harvesting drone according to claim 1, wherein: The main hull comprises an upper portion (212a) and a lower portion (212b), the upper portion and the lower portion being separated by an insulating partition (213), wherein the upper portion comprises the heat transfer element and the navigation profile causes the main hull to selectively surface to expose the upper portion from seawater.

11. A method for operating an underwater energy harvesting drone according to any one of claims 1 to 10, comprising the following steps: delivering cold seawater to an internal storage tank at a first location (904); placing the internal storage tank at a second location to store the cold seawater (906); Automatically navigating the underwater energy harvesting drone to the location of the hydrothermal vent, placing the main housing in a "hot zone" of the vent plume relative to the surrounding seawater (908); and Based on the thermal gradient between the main housing and the internal storage tank, electricity is generated using a thermoelectric module to charge a power storage device (912).

12. The method according to claim 11, further comprising at least one of the following: filling a directional ballast tank to orient the underwater energy harvesting drone in a pogo position (910); and The underwater energy harvesting drone is operated using the requested mission profile (916).

13. The method according to claim 11, further comprising the steps of: Maneuver to open water (914); emptying the internal storage tank (904); and The internal storage tank is refilled by operating the air inlet and outlet (904).

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