A compressed gas energy storage system and method for coupling an electrolysis device and a fuel cell

Abstract

This invention discloses a compressed gas energy storage system and method that couples an electrolysis device and a fuel cell. The system includes a water electrolysis device, with its hydrogen and oxygen outlets connected to a hydrogen compressor unit and an oxygen compressor unit, respectively. Both the hydrogen and oxygen compressor units are sequentially connected to a liquid piston near-isothermal expansion module, an expander, and a hydrogen-oxygen fuel cell, which is connected to the water electrolysis device. Both the hydrogen and oxygen compressor units are equipped with heat exchangers and heat accumulators. The hot side of the heat exchanger is connected to the compressor, and the cold side inlet is connected to a cold water source, while the outlet is connected to the liquid piston near-isothermal expansion module. A heat exchanger is also provided at the expander outlet, with its cold side connected to the expander and the hydrogen-oxygen fuel cell, and its hot side connected to the hydrogen-oxygen fuel cell and a water tank. This system couples the water electrolysis fuel cell system with a compressed hydrogen and oxygen system, fully utilizing the waste heat from water electrolysis and fuel cell products, thus achieving cascaded energy utilization.

Description

Technical Field

[0001] This invention belongs to the field of energy storage technology, specifically relating to a compressed gas energy storage system and method that couples an electrolysis device and a fuel cell. Background Technology

[0002] With the continuous development of renewable energy, its volatility and instability are increasingly impacting the power grid. To address this, renewable energy needs to be combined with energy storage technology to store electricity during low loads and release it during high loads. Simultaneously, as global environmental protection requirements become increasingly stringent, the demand for clean energy technologies is becoming more urgent. The application of hydrogen-oxygen fuel cells has become crucial for achieving a stable supply and efficient utilization of clean energy. Traditional energy storage technologies include battery storage and supercapacitor storage, but they suffer from low energy density, high cost, and short lifespan. Compressed gas energy storage systems, as a sustainable, efficient, controllable, and reliable energy storage technology, are receiving increasing attention. Compressed gas energy storage systems are considered one of the most promising technologies for future energy storage. However, existing compressed gas energy storage technologies suffer from insufficient energy utilization efficiency, lower energy density compared to chemical energy storage systems, lower utilization of low-quality compression heat, and low efficiency in gas expansion work within traditional compressed gas energy storage expansion units. Improving the efficiency of compressed gas energy storage expansion units is also one of the challenges in energy storage technology. Summary of the Invention

[0003] To address the problems of low utilization of low-quality heat of compression and low energy density in existing compressed gas energy storage technologies, this invention aims to provide a novel compressed gas energy storage system and method that couples an electrolysis device and a fuel cell. By coupling the electrolysis cell, fuel cell, and compressed gas energy storage technology, the energy density of the compressed gas energy storage system is improved, and the low-quality heat of compression is effectively utilized. Furthermore, a near-isothermal expansion unit with a liquid piston that can stably exhaust gas is proposed, which significantly improves the gas's work capacity, achieving efficient and high-density energy storage, and contributing to the promotion and application of compressed gas energy storage technology.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a compressed gas energy storage system coupling an electrolysis device and a fuel cell, comprising a water electrolysis device, a heat exchanger, a hydrogen compressor unit, an oxygen compressor unit, a liquid piston near-isothermal expansion module, an expander, and a hydrogen-oxygen fuel cell; the hydrogen outlet and oxygen outlet of the water electrolysis device are respectively connected to the hydrogen compressor unit and the oxygen compressor unit, and the hydrogen compressor unit and the oxygen compressor unit are sequentially connected to the liquid piston near-isothermal expansion module, the expander, and the hydrogen-oxygen fuel cell, and the outlet of the hydrogen-oxygen fuel cell is connected to the inlet of the water electrolysis device; both the hydrogen compressor unit and the oxygen compressor unit are equipped with heat exchangers and heat accumulators, the hot side inlet and outlet of the heat exchanger are connected to the compressor, the cold side inlet of the heat exchanger is connected to a cold water source, and the outlet is connected to the hot water inlet of the liquid piston near-isothermal expansion module; a heat exchanger is installed at the outlet of the expander, the cold side of the heat exchanger is connected to the expander and the hydrogen-oxygen fuel cell, and the hot side is connected to the hydrogen-oxygen fuel cell and the water tank.

[0005] Furthermore, the oxygen compressor unit includes a first compressor, a first heat exchanger, a second compressor, a first accumulator, and an oxygen storage tank connected in sequence; the hot side of the first heat exchanger is connected to the first compressor and the second compressor, and the cold side of the first heat exchanger is connected to a cold water source and a liquid piston near-isothermal expansion module; the hydrogen compressor unit includes a third compressor, a second heat exchanger, a fourth compressor, a second accumulator, and a hydrogen storage tank connected in sequence; the hot side of the second heat exchanger is connected to the third compressor and the fourth compressor, and the cold side of the second heat exchanger is connected to a cold water source and a liquid piston near-isothermal expansion module.

[0006] Furthermore, the outlet of the oxygen storage tank is connected to the liquid piston near-isothermal expansion module and the first expander via the first accumulator, and the hydrogen storage tank is connected to the liquid piston near-isothermal expansion module and the second expander via the second accumulator.

[0007] Furthermore, the liquid piston near-isothermal expansion module includes a first piston near-isothermal expansion module and a second liquid piston near-isothermal expansion module with the same structure and function; the first piston near-isothermal expansion module includes a first piston tank, a second piston tank, a water pump, a buffer chamber inlet and outlet, a buffer chamber outlet and an outlet, and a buffer chamber; pressure and temperature sensors are installed in the first piston tank, the second piston tank, and the buffer chamber; a first sprayer and a second sprayer are respectively installed in the first piston tank and the second piston tank; the first sprayer and the second sprayer are connected to the outlet of the water pump; the inlet of the water pump is connected to the outlet of the first piston tank and the second piston tank; a water turbine is installed between the first piston tank and the second piston tank; the hot water inlets of the first piston tank and the second piston tank are connected to the cold side outlet of the heat exchanger in the compressor unit; the gas inlets of the first piston tank and the second piston tank are connected to the gas outlet of the compressor unit; the gas inlets and outlets of the first piston tank and the second piston tank are also connected to the outlet and outlet of the buffer chamber; the outlet and outlet of the buffer chamber are connected to a water source; and the exhaust port of the buffer chamber is connected to the expander.

[0008] Furthermore, the outlet of the water tank is connected to the cold side of the fifth heat exchanger, and the oxygen and hydrogen outlets of the water electrolysis unit are connected to the hot side of the fifth heat exchanger.

[0009] The present invention also provides an operating method for the compressed gas energy storage system of the coupled electrolysis device and fuel cell, wherein the electrolysis produces oxygen and hydrogen, which are adiabatically compressed after being cooled by a heat exchanger, and the high-pressure oxygen and high-pressure hydrogen after adiabatically compressed are stored separately, and the oxygen and hydrogen release heat through the heat exchanger during the adiabatically compressed process; the compressed oxygen and hydrogen undergo near-isothermal expansion and then enter an expander to do work, and the hydrogen and oxygen after doing work are oxidized and burned to generate water for storage, and the stored water is electrolyzed; the cold water absorbs the heat generated by the adiabatically compressed oxygen and hydrogen through a heat exchanger to become hot water, and the hot water heats the compressed oxygen and hydrogen through a liquid piston near-isothermal expansion module.

[0010] Furthermore, the compressed hydrogen and oxygen absorb heat in the accumulator and then enter the liquid piston near-isothermal expansion module for near-isothermal expansion.

[0011] Furthermore, hot water enters the near-isothermal expansion module of the liquid piston. The near-isothermal expansion module of the liquid piston operates through a first intake stage, an expansion stage, a second intake stage, and an exhaust stage. During the first intake stage, water in the first piston tank flows to the second piston tank via a water turbine. The air inlet valve of the first piston tank opens, and high-pressure gas enters the first piston tank. The first intake stage ends when the water level in the first piston tank drops to the set level, and the expansion stage begins. Spraying begins at the start of the expansion stage, and the hot water in the liquid piston tank replenishes the oxygen. Water in the first piston tank continues to flow to the second piston tank via a water turbine until the gas pressure in the first piston tank expands to the exhaust pressure. The expansion stage ends then, and the second intake stage begins. During the second intake phase, water in the first piston tank continues to flow to the second piston tank via the turbine until the water level in the first piston tank reaches its minimum. At this point, the second intake phase stops, and the exhaust phase begins. The intake air source for the second intake phase is the buffer chamber. During the exhaust phase, water in the second piston tank flows to the first piston tank via the turbine, causing the water level in the first piston tank to rise. Gas in the first piston tank is discharged into the buffer chamber until the water level in the first piston tank reaches its maximum. At this point, the exhaust phase stops, and the next cycle begins. The second piston tank operates in the same manner for the first intake phase, expansion phase, second intake phase, and exhaust phase. Gas in the buffer chamber is continuously discharged at a stable pressure and temperature through the buffer chamber gas inlet and outlet.

[0012] Furthermore, the heat generated by electrolysis to produce hydrogen and oxygen heats the water from the tank in a heat exchanger.

[0013] Furthermore, the hydrogen and oxygen, after performing work, undergo oxidation and combustion in the heat exchanger after being heated by hot water, and the released water enters the water tank.

[0014] Compared with the prior art, the present invention has at least the following beneficial effects:

[0015] This system couples an electrolytic water fuel cell system with a compressed hydrogen and oxygen system, making full use of the waste heat from water electrolysis and fuel cell products. This enables cascaded energy utilization, improving system efficiency and economy. The oxygen and hydrogen produced by water electrolysis are first compressed and stored by a compressor, increasing the system's energy storage capacity. During energy release, the hydrogen and oxygen are first released by an expander before entering the fuel cell, which helps increase the energy release power. The released oxygen then enters the fuel cell, increasing the concentration during the fuel cell reaction, which helps improve fuel cell efficiency and thus improves system economy. At the same time, oxygen can be appropriately mixed with air before entering the fuel cell, improving battery efficiency while ensuring safety. The heat from the water produced by the fuel cell is fully utilized before entering the water storage tank, enabling water recycling. During energy release, the fuel cell and expander simultaneously supply energy to the outside, increasing energy storage density and providing reactive power to the system, which helps improve power quality.

[0016] Furthermore, a liquid piston expansion unit with stable exhaust is provided, which can significantly improve the gas's work capacity and further enhance efficiency. The proposed liquid piston expansion unit adopts a cyclic mode of first intake stage - expansion stage - second intake stage - exhaust stage, introducing the second intake stage after the expansion stage, thereby ensuring continuous and stable operation of the liquid piston expansion. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a novel compressed gas energy storage system that couples an electrolysis device and a fuel cell according to the present invention.

[0018] Figure 2 This is a schematic diagram of the near-isothermal expansion module of the liquid piston in this invention.

[0019] Figure 3 This is a PV diagram of the operation method of the near-isothermal expansion module of the liquid piston in this invention.

[0020] In the attached diagram: 1. First compressor; 2. First heat exchanger; 3. Second compressor; 4. First accumulator; 5. Oxygen storage tank; 6. First liquid piston near-isothermal expansion module; 7. Third heat exchanger; 8. First expander; 9. Hydrogen-oxygen fuel cell; 10. Fourth heat exchanger; 11. Water tank; 12. Fifth heat exchanger; 13. Electrolyte; 14. Third compressor; 15. Second heat exchanger; 16. Fourth compressor; 17. Second accumulator; 18. Hydrogen storage tank; 19. Second liquid piston near-isothermal expansion module; 20. Second expander; 61. First piston tank; 62. Second piston tank; 63. Water pump; 64. First sprayer; 65. Second sprayer; 66. Buffer chamber inlet / outlet; 67. Buffer chamber inlet / outlet; 68. Buffer chamber; 69. Water turbine. Detailed Implementation

[0021] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0022] This invention provides a novel compressed gas energy storage system and method that couples an electrolysis device and a fuel cell. By coupling the electrolysis cell, the fuel cell and the compressed gas energy storage technology, the energy storage density of the compressed gas energy storage system is improved, and the low-quality heat of compression is effectively utilized. Furthermore, a liquid piston near-isothermal expansion unit that can stably exhaust gas is proposed, which greatly improves the gas's work capacity and achieves efficient and high-density energy storage.

[0023] refer to Figure 1 This invention provides a compressed gas energy storage system coupling an electrolysis device and a fuel cell, comprising a water electrolysis device, a heat exchanger, a hydrogen compressor unit, an oxygen compressor unit, a liquid piston near-isothermal expansion module, an expander, and a fuel cell. The hydrogen and oxygen outlets of the water electrolysis device are respectively connected to the hydrogen and oxygen compressor units. Both the hydrogen and oxygen compressor units are sequentially connected to the liquid piston near-isothermal expansion module, the expander, and the fuel cell. The outlet of the fuel cell is connected to the inlet of the water electrolysis device. Both the hydrogen and oxygen compressor units are equipped with heat exchangers and heat accumulators. The hot-side inlet and outlet of the heat exchanger are connected to the compressor, the cold-side inlet is connected to a cold water source, and the outlet is connected to the hot water inlet of the liquid piston near-isothermal expansion module. A heat exchanger is installed at the outlet of the expander. The cold side of the heat exchanger is connected to the expander and the fuel cell, and the hot side is connected to the fuel cell and a water tank. The water electrolysis device employs an electrolysis cell.

[0024] Examples, such as Figure 1As shown, a novel compressed gas energy storage system coupling an electrolysis device and a fuel cell includes compressed oxygen and hydrogen energy storage units and an electrolytic water fuel cell unit; specifically, it includes a first compressor 1, a first heat exchanger 2, a second compressor 3, a first heat accumulator 4, an oxygen storage tank 5, a first liquid piston near-isothermal expansion module 6, a third heat exchanger 7, a first expander 8, a hydrogen-oxygen fuel cell 9, a fourth heat exchanger 10, a water tank 11, a fifth heat exchanger 12, an electrolysis cell 13, a third compressor 14, a second heat exchanger 15, a fourth compressor 16, a second heat accumulator 17, a hydrogen storage tank 18, a second liquid piston near-isothermal expansion module 19, and a second expander 20.

[0025] The compressed oxygen and hydrogen energy storage unit is divided into two parts: compressed oxygen energy storage and compressed hydrogen energy storage. The compressed oxygen energy storage part includes, in sequence, a first compressor 1, a first heat exchanger 2 between the two compressor stages, a second compressor 3, a first heat accumulator 4, an oxygen storage tank 5, a first liquid piston near-isothermal expansion module 6, a first expander 8, and a third heat exchanger 7. The first heat exchanger 2 between the first compressor 1 and the second compressor 3 is connected to the first liquid piston near-isothermal expansion module 6. The compressed hydrogen energy storage part includes, in sequence, a third compressor 14, a second heat exchanger 15 between the two compressor stages, a fourth compressor 16, a second heat accumulator 17, a hydrogen storage tank 18, a second liquid piston near-isothermal expansion module 19, a second expander 20, and a fourth heat exchanger 10. The second heat exchanger 15 between the third compressor 14 and the fourth compressor 16 is connected to the second liquid piston near-isothermal expansion module 19.

[0026] The water electrolysis fuel cell unit includes a hydrogen-oxygen fuel cell 9, a water tank 11, a fifth heat exchanger 12, and an electrolysis water pool 13. The cold end outlet of the third heat exchanger 7 is connected to the inlet of the hydrogen-oxygen fuel cell 9, and one outlet of the hot water from the hydrogen-oxygen fuel cell 9 is connected to the hot end inlet of the third heat exchanger 7. The cold end outlet of the fourth heat exchanger 10 is connected to the inlet of the hydrogen-oxygen fuel cell 9, and the other outlet of the hot water from the hydrogen-oxygen fuel cell 9 is connected to the hot end inlet of the fourth heat exchanger 10.

[0027] The first liquid piston near-isothermal expansion module and the second liquid piston near-isothermal expansion module are completely identical. Taking the first liquid piston near-isothermal expansion module as an example, it includes a first piston tank 61, a second piston tank 62, a water pump 63, a first sprayer 64, a second sprayer 65, a buffer chamber inlet / outlet 66, a buffer chamber air inlet / outlet 67, and a buffer chamber 68. The first liquid piston near-isothermal expansion module 6 includes a first piston tank 61, a second piston tank 62, a water pump 63, a buffer chamber inlet / outlet 66, a buffer chamber air inlet / outlet 67, and a buffer chamber 68. Pressure and temperature sensors are installed in the first piston tank 61, the second piston tank 62, and the buffer chamber 68. The first piston tank 61 and the second piston tank 62 are respectively equipped with a first sprayer 64 and a second sprayer 65. The first sprayer 64 and the second sprayer 65 are connected to the outlet of the water pump 63, and the inlet of the water pump 63 is connected to the first... The water outlets of piston tank 61 and second piston tank 62 are connected to a water turbine 69 located between them. The hot water inlets of first piston tank 61 and second piston tank 62 are connected to the cold-side outlet of the heat exchanger in the compressor unit. The gas inlets of first piston tank 61 and second piston tank 62 are connected to the gas outlet of the compressor unit. These gas inlets and outlets are also connected to the buffer chamber inlet / outlet 67. The buffer chamber inlet / outlet 66 is connected to a water source, and the buffer chamber inlet / outlet 67 is connected to an expander. First piston tank 61 and second piston tank 62 are constructed with insulated tank bodies.

[0028] The operating method of the novel compressed gas energy storage system that couples an electrolysis device and a fuel cell, as described in this invention, is as follows:

[0029] The oxygen produced by electrolysis in electrolytic cell 13 is cooled by the fifth heat exchanger 12 and then enters the first compressor 1 for adiabatic compression. After being cooled by the first heat exchanger 2, it enters the second compressor 3 for adiabatic compression. The gas compressed by the second compressor 3 enters the first heat accumulator 4 to store heat before entering the oxygen storage tank 5. The hydrogen produced by electrolysis in electrolytic cell 13 is cooled by the fifth heat exchanger 12 and then enters the third compressor 14 for adiabatic compression. After being cooled by the second heat exchanger 15, it enters the fourth compressor 16 for adiabatic compression. The gas compressed by the fourth compressor 16 enters the second heat accumulator 17 to store heat before entering the hydrogen storage tank 18. During the discharge phase, oxygen in oxygen storage tank 5 is heated by the first accumulator 4 and then enters the first liquid piston near-isothermal expansion module 6 for near-isothermal expansion. After near-isothermal expansion, the gas with a certain temperature enters the first expander 8 to expand and do work. Hydrogen in hydrogen storage tank 18 is heated by the second accumulator 17 and then enters the second liquid piston near-isothermal expansion module 19 for near-isothermal expansion. After near-isothermal expansion, the gas with a certain temperature enters the second expander 20 to expand and do work. The oxygen after expansion by the first expander 8 and the hydrogen after expansion by the second expander 20 are heated by the third heat exchanger 7 and the fourth heat exchanger 10 respectively, and then mixed with air before entering the hydrogen-oxygen fuel cell 9 for reaction. The water produced after the reaction in the hydrogen-oxygen fuel cell 9 is stored in water tank 11. During the electrolysis process, the water stored in water tank 11 is heated by the fifth heat exchanger 12 and then enters the electrolytic cell 13 for electrolysis to complete one cycle. The cold water, after passing through the first heat exchanger 2 between the first compressor 1 and the second compressor 3, becomes hot water, which is used in the first liquid piston near-isothermal expansion module 6. The cold water becomes hot water after passing through the second heat exchanger 15 between the third compressor 14 and the fourth compressor 16, which is then used for the near-isothermal expansion module 19 of the second liquid piston.

[0030] refer to Figure 1 The heat generated by the electrolysis of hydrogen and oxygen in the electrolytic cell 13 is used in the fifth heat exchanger 12. The water in the water tank 11 is heated by the fifth heat exchanger 12 and then enters the electrolytic cell 13 to improve the energy efficiency of the electrolytic cell 13.

[0031] refer to Figure 2 and Figure 3The first liquid piston near-isothermal expansion module 6 and the second liquid piston near-isothermal expansion module 19 operate in exactly the same way. Therefore, only one of the liquid piston near-isothermal expansion modules needs to be described. Since the two piston tanks within the liquid piston near-isothermal expansion module operate in exactly the same way, only one tank needs to be described. Taking the first piston tank 61 as an example, during the first intake stage, water in the first piston tank 61 flows to the second piston tank 62 via the water turbine 69. The air inlet valve of the first piston tank 61 opens, and high-pressure gas enters the first piston tank 61, causing its water level to drop. The first intake stage ends and the expansion stage begins when the water level in the first piston tank 61 drops to the set level. During the expansion phase, spraying begins at the start, and hot water in the liquid piston tank replenishes the oxygen, increasing the air's ability to perform work. Water in the first piston tank 61 continues to flow to the second piston tank 62 via the water turbine 69 until the gas pressure in the first piston tank 61 expands to the exhaust pressure, at which point the expansion phase ends and the second intake phase begins. During the second intake phase, water in the first piston tank 61 continues to flow to the second piston tank 62 via the water turbine 69 until the water level in the first piston tank 61 reaches its minimum level, at which point the second intake phase stops and the exhaust phase begins. The intake air source for the second intake phase is the buffer chamber. During the exhaust phase, water in the second piston tank 62 flows to the first piston tank 61 via the water turbine 69, causing the water level in the first piston tank 61 to rise. At this time, the gas in the first piston tank 61 is discharged into the buffer chamber until the water level in the first piston tank 61 reaches its maximum level, at which point the exhaust phase stops and the next cycle begins. The gas in the buffer chamber is continuously discharged through the gas inlet and outlet of the buffer chamber, and the gas pressure and temperature are relatively stable, providing a stable gas source for the subsequent expander. The water inlet and outlet of the buffer chamber are connected to the ground water tank to maintain the constant pressure state of the buffer chamber.

Claims

1. A compressed gas energy storage system coupling an electrolysis device and a fuel cell, characterized in that, The system includes a water electrolysis unit, a heat exchanger, a hydrogen compressor unit, an oxygen compressor unit, a liquid piston near-isothermal expansion module, an expander, and a hydrogen-oxygen fuel cell. The hydrogen and oxygen outlets of the water electrolysis unit are connected to the hydrogen and oxygen compressor units, respectively. Both the hydrogen and oxygen compressor units are sequentially connected to the liquid piston near-isothermal expansion module, the expander, and the hydrogen-oxygen fuel cell. The outlet of the hydrogen-oxygen fuel cell is connected to the inlet of the water electrolysis unit. Both the hydrogen and oxygen compressor units are equipped with heat exchangers and heat accumulators. The hot-side inlet and outlet of the heat exchangers are... The compressor is connected, the cold side inlet of the heat exchanger is connected to a cold water source, and the outlet is connected to the hot water inlet of the liquid piston near-isothermal expansion module; a heat exchanger is installed at the outlet of the expander, the cold side of which is connected to the expander and the hydrogen-oxygen fuel cell, and the hot side is connected to the hydrogen-oxygen fuel cell (9) and the water tank (11); the liquid piston near-isothermal expansion module includes a first liquid piston near-isothermal expansion module (6) and a second liquid piston near-isothermal expansion module (19) with the same structure and function; the first liquid piston near-isothermal expansion module (6) includes a first piston tank (61) and a second piston tank (62). 62) Water pump (63), buffer chamber inlet and outlet (66), buffer chamber air inlet and outlet (67), and buffer chamber (68); pressure and temperature sensors are installed in the first piston tank (61), the second piston tank (62), and the buffer chamber (68). The first piston tank (61) and the second piston tank (62) are respectively equipped with a first sprayer (64) and a second sprayer (65). The first sprayer (64) and the second sprayer (65) are connected to the outlet of the water pump (63). The inlet of the water pump (63) is connected to the first piston tank (61) and the second piston tank (62). The outlet of the second piston tank (62) is connected to the water turbine (69) between the first piston tank (61) and the second piston tank (62); the hot water inlets of the first piston tank (61) and the second piston tank (62) are connected to the cold side outlet of the heat exchanger in the compressor unit; the gas inlets of the first piston tank (61) and the second piston tank (62) are connected to the gas outlet of the compressor unit; the gas inlets and outlets of the first piston tank (61) and the second piston tank (62) are also connected to the air inlet and outlet of the buffer chamber (67); the water inlet and outlet of the buffer chamber are connected to the water source; and the exhaust port of the buffer chamber is connected to the expander.

2. The compressed gas energy storage system for the coupled electrolysis device and fuel cell according to claim 1, characterized in that, The oxygen compressor unit includes a first compressor (1), a first heat exchanger (2), a second compressor (3), a first accumulator (4), and an oxygen storage tank (5) connected in sequence. The hot side of the first heat exchanger (2) is connected to the first compressor (1) and the second compressor (3), and the cold side of the first heat exchanger (2) is connected to a cold water source and a liquid piston near-isothermal expansion module. The hydrogen compressor unit includes a third compressor (14), a second heat exchanger (15), a fourth compressor (16), a second accumulator (17), and a hydrogen storage tank (18) connected in sequence. The hot side of the second heat exchanger (15) is connected to the third compressor (14) and the fourth compressor (16), and the cold side of the second heat exchanger (15) is connected to a cold water source and a liquid piston near-isothermal expansion module.

3. The compressed gas energy storage system for the coupled electrolysis device and fuel cell according to claim 2, characterized in that, The outlet of the oxygen storage tank (5) is connected to the liquid piston near-isothermal expansion module and the first expander (8) via the first accumulator (4), and the hydrogen storage tank (18) is connected to the liquid piston near-isothermal expansion module and the second expander (20) via the second accumulator (17).

4. The compressed gas energy storage system for the coupled electrolysis device and fuel cell according to claim 1, characterized in that, The outlet of the water tank (11) is connected to the cold side of the fifth heat exchanger (12), and the oxygen and hydrogen outlets of the water electrolysis unit are connected to the hot side of the fifth heat exchanger (12).

5. The method of operating the compressed gas energy storage system of the coupled electrolysis device and fuel cell as described in any one of claims 1-4, characterized in that, Electrolysis produces oxygen and hydrogen. After cooling in a heat exchanger, the oxygen and hydrogen undergo adiabatic compression. The high-pressure oxygen and hydrogen produced by adiabatic compression are stored separately. During the adiabatic compression process, the oxygen and hydrogen release heat through the heat exchanger. The compressed oxygen and hydrogen undergo near-isothermal expansion and then enter an expander to perform work. The hydrogen and oxygen produced after work are oxidized and burned to generate water, which is then stored. The stored water is electrolyzed. The cold water absorbs the heat generated during the adiabatic compression process of the oxygen and hydrogen through a heat exchanger to become hot water. The hot water then heats the compressed oxygen and hydrogen through a near-isothermal expansion module with a liquid piston.

6. The operating method according to claim 5, characterized in that, After being compressed, the hydrogen and oxygen absorb heat in the accumulator and then enter the liquid piston near-isothermal expansion module for near-isothermal expansion.

7. The operating method according to claim 5, characterized in that, Hot water enters the near-isothermal expansion module of the liquid piston. The near-isothermal expansion module of the liquid piston operates in the first intake stage, the expansion stage, the second intake stage, and the exhaust stage. In the first intake stage, water in the first piston tank (61) flows to the second piston tank (62) through the water turbine (69). The air inlet valve of the first piston tank (61) is opened, and high-pressure gas enters the first piston tank (61). When the water level in the first piston tank (61) drops to the set water level, the first intake stage ends and the expansion stage begins. Spraying begins when the expansion stage begins. The hot water in the liquid piston tank is used to supplement oxygen. The water in the first piston tank (61) continues to flow to the second piston tank (62) through the water turbine (69). When the gas pressure in the first piston tank (61) expands to the exhaust pressure, the expansion stage ends and the second intake stage begins. At this time, the water in the first piston tank (61) continues to flow to the second piston tank (62) through the water turbine (69) until the water level in the first piston tank (61) reaches the lowest water level. At this time, the second intake stage stops and the exhaust stage begins. The intake air source for the second intake stage is the buffer chamber. During the exhaust stage, the water in the second piston tank (62) flows to the first piston tank (61) through the water turbine (69). The water level in the first piston tank (61) begins to rise, and the gas in the first piston tank (61) is discharged into the buffer chamber. At this time, the exhaust stage stops and the next cycle begins when the water level in the first piston tank (61) reaches the highest water level. The second piston tank (62) operates the first intake stage, the expansion stage, the second intake stage, and the exhaust stage in the same way. The gas in the buffer chamber is continuously discharged through the gas inlet and outlet of the buffer chamber, and the pressure and temperature of the gas are stable.

8. The operating method according to claim 5, characterized in that, The heat generated by the electrolysis of hydrogen and oxygen heats the water from the water tank (11) in the heat exchanger.

9. The operating method according to claim 5, characterized in that, After the work is done, the hydrogen and oxygen are heated by hot water in the heat exchanger and then undergo oxidation and combustion. The water that releases heat enters the water tank (11).

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