Underground constant-pressure compressed air energy storage system for multi-stage segmented compression

Abstract

The invention discloses an underground constant-pressure compressed air energy storage system with a multi-stage segmented compression function. The underground constant-pressure compressed air energy storage system comprises an overground system and an underground system. The underground system comprises an underground water and gas containing grotto arranged in surrounding rock, and a gas transmission vertical shaft and a water transmission vertical shaft which are respectively communicated with the grotto; the overground system comprises a compressor unit, a cooler unit, a renewable energy power station, a motor, a battery energy storage cabinet, a heat storage tank, a cold storage tank, a heat exchanger, a turbine expansion generator, an earth surface reservoir, an electric booster water pump and a water conveying pipeline. According to the system, a traditional constant-volume variable-pressure compressed air energy storage system is coupled with a constant-pressure compressed air energy storage system, water head pressure generated by the overground and underground height difference is fully utilized, a battery energy storage cabinet is adopted for supplementing energy, constant high-pressure output in the energy release process is guaranteed, meanwhile, the energy efficiency of the system is remarkably improved by adopting a staged multi-stage compression strategy, and the energy efficiency of the system is improved. The constant-voltage power generation characteristic in the energy-releasing power generation stage is remarkable, the heat energy management system is perfect, and the overall energy and resource comprehensive utilization degree of the system is high.

Description

Technical Field

[0001] This invention belongs to the technical field of compressed air energy storage and multi-energy complementary energy system, specifically relating to a multi-stage segmented compression underground constant pressure compressed air energy storage system, which is suitable for energy storage and peak shaving applications of large-scale renewable energy access to the power system. Background Technology

[0002] Compressed air energy storage, as a novel physical energy storage technology, has received widespread attention in recent years. It boasts advantages such as large scale, long cycle time, long continuous discharge time, and minimal environmental impact. Its working principle is as follows: during off-peak electricity demand, it absorbs electrical energy from the grid or utilizes compressed air from wind or solar energy sources, storing it in underground gas storage facilities; when electricity is needed, the high-pressure air is released to generate electricity.

[0003] Existing compressed air energy storage systems, such as advanced adiabatic compressed air energy storage systems and non-combustion compressed air energy storage systems, typically employ a "multi-stage compression + multi-stage expansion" energy storage and release mode, and use a constant-capacity variable-pressure mode for gas storage. During system operation, the air pressure in the underground gas storage cavern fluctuates significantly, leading to unstable operation of the compressor and turbine expander generator, low energy conversion efficiency, and poor power generation quality and supply stability. Specifically, conventional compressed air energy storage systems generally suffer from the following problems: 1) During compression and expansion, the system air pressure changes significantly, making it difficult to achieve quasi-constant pressure operation, resulting in low system energy efficiency; 2) The drastic fluctuations in air pressure in the gas storage cavern lead to complex stress conditions on the surrounding rock and sealing structure, affecting structural safety; 3) During the energy release phase, the system output power fluctuates significantly, which is detrimental to grid connection and stable power supply.

[0004] Therefore, researchers have gradually shifted their focus to constant-pressure compressed air energy storage systems. Currently, most of these systems utilize water level differences to maintain constant air pressure within the cavern, and their applications are typically located on the seabed or lakebed. However, the head pressure generated by natural water level differences is often far lower than the maximum air pressure required by compressed air energy storage systems. Therefore, relying solely on the head pressure generated by natural water levels is insufficient to support the efficient operation of constant-pressure compressed air energy storage systems.

[0005] Against this backdrop, it is of great significance to study how to couple traditional compressed air energy storage systems with constant pressure compressed air energy storage systems, and to achieve multi-energy coupling and complementarity of "wind-solar-hydro-gas-electricity" by optimizing compression strategies, thereby improving system operating efficiency and power generation quality. Summary of the Invention

[0006] The technical problem this invention aims to solve is to provide a multi-stage, segmented compression underground constant-pressure compressed air energy storage system, addressing the shortcomings of existing technologies. This system couples a traditional constant-capacity variable-pressure compressed air energy storage system with a constant-pressure compressed air energy storage system, fully utilizing the water head pressure generated by the elevation difference between above-ground and underground levels. It also employs a battery energy storage cabinet for supplementary energy, ensuring a constant high-pressure output during the energy release process. Simultaneously, the multi-stage, segmented compression strategy significantly improves system energy efficiency, exhibits remarkable constant-pressure power generation characteristics during the energy release and power generation phase, has a sophisticated thermal energy management system, and demonstrates high overall energy and resource utilization efficiency.

[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is: a multi-stage segmented compression underground constant pressure compressed air energy storage system, which includes an above-ground system and an underground system; The underground system includes a cavern containing underground water and gas within the surrounding rock, and gas transmission shafts and water transmission shafts respectively connected to the cavern. The above-ground system includes a compressor unit, a cooler unit, a renewable energy power station, an electric motor, a battery energy storage cabinet, a thermal storage tank, a cold storage tank, a heat exchanger, a turboexpansion generator, a surface water reservoir, an electric booster pump, and water pipelines. The renewable energy power station is electrically connected to the electric motor and the battery energy storage cabinet, and the electric motor is electrically connected to the compressor unit. The battery energy storage cabinet supplies power to the electric booster pump. The compressor unit includes a first-stage compressor, a second-stage compressor, a third-stage compressor, and a fourth-stage compressor connected in series. The air inlet of the first-stage compressor is open to the atmosphere. The cooler unit includes a first cooler, a second cooler, a third cooler, and a fourth cooler, which are respectively installed on the first-stage compressor, the second cooler, the third cooler, and the fourth cooler. Downstream of the second, third, and fourth stage compressors; the heat storage tank and cold storage tank are connected to the cooler assembly via fluid pipelines, forming a thermal cycle loop for recovering, storing, and utilizing compression heat; the air inlet of the heat exchanger is connected to the cavern via an air supply pipeline, the hot-side inlet of the heat exchanger is connected to the heat storage tank, and the hot-side outlet is connected to the cold storage tank; the air inlet of the turbine expander is connected to the air outlet of the heat exchanger for generating electricity and connecting to the ground power grid; the water supply pipeline connects the surface reservoir to the cavern via the electric booster pump; the cavern, through connecting pipelines and a valve control system, can be selectively connected to the compressed air flow path of the air outlet of the second or fourth cooler, thereby achieving staged energy storage; One operating cycle of the energy storage system includes energy storage, gas storage, energy release for power generation, and water storage reset, wherein the energy storage process includes the following stages: Constant pressure air filling and energy storage stage: When the cavern is filled with water, the first-stage compressor and the second-stage compressor are used to compress air and inject it into the cavern. The water in the cavern is gradually discharged to the surface reservoir through the water pipeline. During this process, the air pressure and the water head pressure in the cavern are kept in dynamic balance. Variable pressure air-filling energy storage stage: After the water in the cavern is completely drained, the first-stage compressor, second-stage compressor, third-stage compressor and fourth-stage compressor continue to compress air and inject it into the cavern, so that the air pressure in the cavern rises. At the same time, the pressure ratio of the fourth-stage compressor is dynamically adjusted according to the cavern pressure to optimize efficiency until the cavern reaches the preset maximum working pressure.

[0008] Specifically, one operating cycle of the energy storage system is as follows: S1. Energy storage: Utilizing the electrical energy from renewable energy power plants to drive electric motors, which in turn drive compressor units to perform multi-stage compression and cooling of air from the atmosphere, and then inject the compressed air into the cavern for storage in stages, performing constant pressure gas filling energy storage and variable pressure gas filling energy storage; S2. Gas Storage: Stop the gas filling and close the valve control system to allow the high-pressure air to be statically stored in the cavern. S3. Energy Release and Power Generation: The electric energy stored in the battery energy storage cabinet drives the electric booster water pump. Through the gravitational potential energy of the electric booster water pump and the water, the water in the surface reservoir is injected into the cavern through the water pipeline. The constant pressure high-pressure air stored in the cavern is discharged into the heat exchanger through the air pipeline. After being heated by the heat exchanger, the high-pressure air drives the turbine expansion generator to generate electricity. The generated electricity is input into the ground power grid. S4. Water Storage Reset: After the energy release and power generation ends, water from the surface reservoir is continuously injected into the cavern by an electric booster pump until the cavern is refilled with water. This state is maintained until the next cycle begins.

[0009] Preferably, the valve control system includes a first air valve, a second air valve, and a water valve. The first air valve is located in the compressed air flow path between the second cooler and the third-stage compressor. The second air valve is located in the compressed air flow path between the second cooler and the cavern. The surface reservoir is connected to the water supply pipeline in sequence via the water valve and the electric booster pump.

[0010] As a further preferred embodiment, the outlet of the first-stage compressor is connected to the inlet of the first cooler; the outlet of the first cooler is connected to the inlet of the second-stage compressor; the outlet of the second-stage compressor is connected to the inlet of the second cooler; the outlet of the second cooler is connected to the inlet of the third-stage compressor via the first air valve; the outlet of the second cooler is connected to the first air supply pipe via the second air valve; the outlet of the third-stage compressor is connected to the inlet of the third cooler; the outlet of the third cooler is connected to the inlet of the fourth-stage compressor; and the outlet of the fourth-stage compressor is connected to the inlet of the fourth cooler. The outlets of the first, second, third, and fourth coolers are connected to the inlet of the heat storage tank. The outlet of the heat storage tank is connected to the hot-side inlet of the heat exchanger. The hot-side outlet of the heat exchanger is connected to the inlet of the cold storage tank. The outlet of the cold storage tank is connected to the inlet of the first, second, third, and fourth coolers. The first, second, and third air supply pipes and the air supply pipelines pass through the air supply shaft and extend into the cavern. The outlet gas of the turbine expander generator is connected to the atmosphere. The water supply pipeline passes through the water supply shaft and extends into the cavern.

[0011] Preferably, the inner wall of the cavern is provided with a heat-insulating sealing layer. By setting a heat-insulating sealing layer, the air heat can be preserved to the maximum extent while ensuring the sealing performance of the cavern, preventing heat transfer to the surrounding rock and reducing heat loss.

[0012] Compared with existing technologies, the multi-stage segmented compression underground constant pressure compressed air energy storage system of the present invention has the following advantages: (1) Phased multi-stage compression strategy improves energy efficiency. The compression process of the energy storage system of the present invention is divided into two stages: In the first stage, when there is water in the cavern, a two-stage constant pressure compression strategy is adopted to always maintain the dynamic balance between the air pressure and the water head pressure in the cavern, and the compressor is in constant pressure ratio mode; In the second stage, after the water in the cavern is drained, a four-stage variable pressure compression strategy is adopted to control the outlet pressure of the fourth stage compressor to always be equal to the air pressure in the cavern, thus avoiding the energy efficiency loss of traditional constant pressure ratio compressors in the high pressure stage.

[0013] (2) The constant-pressure power generation characteristics are significant during the energy release power generation stage. During the energy release power generation stage, gravitational potential energy and electric booster water pump are used together to inject water, so that air enters the turbine expander generator at a constant pressure, resulting in stable power output and higher power quality. Constant-pressure energy release ensures stable power output of the turbine expander generator, improves power generation efficiency and operational reliability, and enhances the quality of grid-connected power.

[0014] (3) Improved thermal energy management system. By setting up heat storage tanks and cold storage tanks on the ground, the heat of compression is recovered, stored and utilized during the compression and expansion stages, respectively, to achieve quasi-isothermal compression and expansion processes and improve the overall thermal efficiency of the system. In addition, the system can achieve dynamic coupling with the surface ambient temperature through heat exchangers and heat storage tanks, optimizing the seasonal operating performance of the system.

[0015] (4) The system has a high overall energy and resource utilization rate. The system can be directly coordinated with photovoltaic, wind power and battery energy storage systems to achieve multi-energy coupling and complementarity of "wind-solar-water-gas-electricity". In addition, the underground water and gas co-containment cavern reduces the scale of ground facilities, which has good engineering economy and environmental adaptability. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the underground constant pressure compressed air energy storage system with multi-stage segmented compression in the embodiment; The specific reference numerals in the figure are as follows: 1-First stage compressor; 2-Second stage compressor; 3-Third stage compressor; 4-Fourth stage compressor; 5-First cooler; 6-Second cooler; 7-Third cooler; 8-Fourth cooler; 9-First air valve; 10-Second air valve; 11-Electric motor; 12-Heat storage tank; 13-Cold storage tank; 14-Gas transmission shaft; 15-Cavity; 16-Insulation sealing layer; 17-Water transmission shaft; 18-Heat exchanger; 19-Electric booster pump; 20-Water valve; 21-Turbine expander generator; 22-Ground power grid; 23-Surface water reservoir; 24-Battery energy storage cabinet; 25-Renewable energy power station; 26-Surrounding rock; 27-Water transmission pipeline; 28-First gas transmission pipeline; 29-Second gas transmission pipeline; 30-Gas transmission pipeline. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0018] Example: A multi-stage segmented compression underground constant pressure compressed air energy storage system, which includes a surface system and an underground system.

[0019] The underground system includes a cavern 15 containing underground water and gas within the surrounding rock 26, and a gas transmission shaft 14 and a water transmission shaft 17 connected to the cavern 15 respectively. The inner wall of the cavern 15 is provided with a heat insulation and sealing layer 16.

[0020] The above-ground system includes a compressor unit, a cooler unit, a renewable energy power station 25, an electric motor 11, a battery energy storage cabinet 24, a thermal storage tank 12, a cold storage tank 13, a heat exchanger 18, a turboexpansion generator 21, a surface water reservoir 23, an electric booster pump 19, and a water pipeline 27. The renewable energy power station 25 is either a wind power station or a photovoltaic power station. The renewable energy power station 25 is electrically connected to the electric motor 11 and the battery energy storage cabinet 24. The electric motor 11 is electrically connected to the compressor unit. The battery energy storage cabinet 24 supplies power to the electric booster pump 19 and can smooth out power fluctuations from renewable energy sources. The compressor unit includes a first-stage compressor 1, a second-stage compressor 2, a third-stage compressor 3, and a fourth-stage compressor 4 connected in series to compress air from the atmosphere in stages. The air inlet of the first-stage compressor 1 is open to the atmosphere. The cooler unit includes a first cooler 5, a second cooler 6, a third cooler 7, and a fourth cooler 8. The first stage compressor 1 and the fourth stage compressor 8 are respectively located downstream of the first stage compressor 1, the second stage compressor 2, the third stage compressor 3 and the fourth stage compressor 4, and are used to cool the compressed air after each stage. The heat storage tank 12 and the cold storage tank 13 are connected to the cooler group through fluid pipelines to form a heat cycle loop for recovering, storing and utilizing the heat of compression. The air inlet of the heat exchanger 18 is connected to the cavern 15 through the air transmission pipeline 30. The hot side inlet of the heat exchanger 18 is connected to the heat storage tank 12 and the hot side outlet is connected to the cold storage tank 13. The air inlet of the turbine expander 21 is connected to the air outlet of the heat exchanger 18 for generating electricity and connecting to the ground power grid 22. The water transmission pipeline 27 connects the surface water reservoir 23 to the cavern 15 through the electric booster water pump 19. The cavern 15 can be selectively connected to the compressed air flow path of the air outlet of the second stage compressor 6 or the fourth stage compressor 8 through connecting pipelines and valve control system, so as to realize staged energy storage.

[0021] Specifically, in this embodiment, the valve control system includes a first air valve 9, a second air valve 10, and a water valve 20. The first air valve 9 is located in the compressed air flow path between the second cooler 6 and the third-stage compressor 3. The second air valve 10 is located in the compressed air flow path between the second cooler 6 and the cavern 15. The surface reservoir 23 is connected to the water supply pipeline 27 via the water valve 20 and the electric booster pump 19. The air outlet of the first-stage compressor 1 is connected to the air inlet of the first cooler 5. The air outlet of the first cooler 5 is connected to the air inlet of the second-stage compressor 2. The air outlet of the second-stage compressor 2 is connected to the air inlet of the second cooler 6. The air outlet of the second cooler 6 is connected to the air inlet of the third-stage compressor 3 via the first air valve 9. The air outlet of the second cooler 6 is connected to the first air supply pipe 28 via the second air valve 10. The air outlet of the third-stage compressor 3 is connected to the third... The air inlet of cooler 7 is connected to the air outlet of the third cooler 7, which is connected to the air inlet of the fourth stage compressor 4. The air outlet of the fourth stage compressor 4 is connected to the air inlet of the fourth cooler 8, which is connected to the air outlet of the fourth cooler 8. The air outlet of the fourth cooler 8 is connected to the second air supply pipe 29. The liquid outlets of the first cooler 5, the second cooler 6, the third cooler 7, and the fourth cooler 8 are respectively connected to the liquid inlet of the heat storage tank 12. The liquid outlet of the heat storage tank 12 is connected to the hot side inlet of the heat exchanger 18. The hot side outlet of the heat exchanger 18 is connected to the liquid inlet of the cold storage tank 13. The liquid outlet of the cold storage tank 13 is respectively connected to the liquid inlets of the first cooler 5, the second cooler 6, the third cooler 7, and the fourth cooler 8. The first air supply pipe 28, the second air supply pipe 29, and the air supply pipeline 30 pass through the air supply shaft 14 and extend into the cavern 15. The outlet gas of the turbine expansion generator 21 is connected to the atmosphere. The water supply pipeline 27 passes through the water supply shaft 17 and extends into the cavern 15.

[0022] One operating cycle of the aforementioned energy storage system includes energy storage, gas storage, energy release for power generation, and water storage for resetting, specifically: S1. Energy Storage: The electric motor 11 is driven by the electricity from the renewable energy power station 25 (the battery energy storage cabinet 24 also absorbs the electricity from the renewable energy power station 25 for supplementary power), which in turn drives the compressor unit to compress and cool the air from the atmosphere in multiple stages, and injects the compressed air into the cavern 15 for storage in stages, and performs the following constant pressure gas charging energy storage and variable pressure gas charging energy storage processes in sequence: Constant pressure air-filling energy storage stage: When the cavern 15 is filled with water, the second air valve 10 and the water valve 20 are opened, and the first air valve 9 is closed. Air from the environment is compressed and injected into the cavern 15 using the first-stage compressor 1 and the second-stage compressor 2. At this time, the water in the cavern 15 is gradually discharged to the surface reservoir 23 through the water pipeline 27. During this process, the air pressure and the water head pressure in the cavern 15 are kept in dynamic equilibrium, with both being equal. p 0; Variable pressure air-filling energy storage stage: After the water in cavern 15 is completely drained, the second air valve 10 and the water valve 20 are closed, and the first air valve 9 is opened. The first-stage compressor 1, the second-stage compressor 2, the third-stage compressor 3, and the fourth-stage compressor 4 continue to compress air and inject it into cavern 15, causing the air pressure inside cavern 15 to rise. Simultaneously, the pressure ratio of the fourth-stage compressor 4 is dynamically adjusted according to the pressure in cavern 15 to optimize efficiency. The pressure ratio of the fourth-stage compressor 4 gradually increases as the pressure in cavern 15 increases until the preset maximum working pressure is reached inside cavern 15. p max ; S2. Gas storage: After the compression process is completed, the gas storage stage begins. At this time, the inflation is stopped and the valve control system is closed, so that the high-pressure air is statically stored in the cavern 15. Under the action of the heat insulation and sealing layer 16, the air in the cavern 15 will not penetrate into the surrounding rock 26, and the heat of the air is also preserved in the cavern 15 to the greatest extent. S3. Energy Release and Power Generation: Open the water valve 20 and the electric booster pump 19. Use the electrical energy stored in the battery energy storage cabinet 24 to drive the electric booster pump 19 to work. Through the gravitational potential energy of the electric booster pump 19 and the water, the water in the surface reservoir 23 is injected into the cavern 15 through the water pipeline 27. Under the driving force of the water pressure, the constant pressure high-pressure air stored in the cavern 15 is pushed to the surface through the gas pipeline 30 and discharged into the heat exchanger 18. After being heated by the heat exchanger 18, it enters the turbine expansion generator 21 and drives the turbine expansion generator 21 to generate electricity. The generated energy is input into the ground power grid 22. Throughout the entire energy release and power generation process, the air pressure entering the turbine expansion generator 21 is kept constant, and its magnitude is equal to the air pressure in the cavern 15 at the end of the gas storage process. S4. Water Storage Reset: After the energy release and power generation ends, the water in the surface water reservoir 23 is continuously injected into the cavern 15 by the electric booster water pump 19 until the cavern 15 is refilled with water. This state is maintained until the next cycle begins.

Claims

1. A multi-stage, segmented compressed, underground constant pressure compressed air energy storage system, characterized in that, The energy storage system comprises an above-ground system and an underground system; The underground system comprises a cavern compatible with water and gas arranged in surrounding rock, and a gas delivery shaft and a water delivery shaft respectively communicating with the cavern; The above-ground system comprises a compressor set, a cooler set, a renewable energy power station, an electric motor, a battery energy storage cabinet, a heat storage tank, a cold storage tank, a heat exchanger, a turbo-expander generator, a surface reservoir, an electric booster water pump and a water delivery pipeline; the renewable energy power station is electrically connected with the electric motor and the battery energy storage cabinet respectively, the electric motor is electrically connected with the compressor set, and the battery energy storage cabinet is used for supplying power to the electric booster water pump; the compressor set comprises a first-stage compressor, a second-stage compressor, a third-stage compressor and a fourth-stage compressor connected in series; the first-stage compressor is communicated with the atmosphere; the cooler set comprises a first cooler, a second cooler, a third cooler and a fourth cooler arranged downstream of the first-stage compressor, the second-stage compressor, the third-stage compressor and the fourth-stage compressor respectively; the heat storage tank and the cold storage tank are connected with the cooler set through fluid pipelines to form a heat cycle loop for recycling, storing and utilizing compression heat; the heat exchanger is communicated with the cavern through a gas delivery pipeline, and the heat side inlet of the heat exchanger is connected with the heat storage tank, and the heat side outlet is connected with the cold storage tank; the gas inlet of the turbo-expander generator is connected with the gas outlet of the heat exchanger for power generation and connection with the ground power grid; the water delivery pipeline communicates the surface reservoir with the cavern through the electric booster water pump; the cavern is selectively communicated with the compressed air flow path of the gas outlet of the second cooler or the fourth cooler through a connecting pipeline and a valve control system, so as to realize staged energy storage; One operation cycle of the energy storage system comprises energy storage, gas storage, energy release and water storage reset, wherein the energy storage process comprises the following staged processes: Constant-pressure air charging and energy storage stage: when the cavern is filled with water, the air is compressed by the first-stage compressor and the second-stage compressor and injected into the cavern, and the water in the cavern is gradually discharged to the surface reservoir, during which the air pressure and the water head pressure of the cavern are kept in dynamic balance; Variable-pressure air charging and energy storage stage: when the water in the cavern is completely discharged, the air is continuously compressed by the first-stage compressor, the second-stage compressor, the third-stage compressor and the fourth-stage compressor and injected into the cavern to increase the air pressure in the cavern, and the pressure ratio of the fourth-stage compressor is dynamically adjusted according to the pressure of the cavern to optimize the efficiency until the cavern reaches the preset maximum working pressure.

2. The multi-stage segmented compressed underground constant pressure compressed air energy storage system of claim 1, wherein, One operation cycle of the energy storage system is as follows: S1. Energy storage: the electric motor is driven by the electric energy of the renewable energy power station, and then the compressor set is driven to compress and cool the air from the atmosphere in multiple stages, and the compressed air is injected into the cavern in stages to store, and constant-pressure air charging and energy storage and variable-pressure air charging and energy storage are performed; S2. Gas storage: stop air charging and close the valve control system to store the high-pressure air in the cavern statically; S3. Energy release power generation: using the electric energy stored in the battery energy storage cabinet to drive the electric booster water pump, through the action of the electric booster water pump and the gravitational potential energy of water, the water in the surface reservoir is injected into the cavern through the water pipeline, so that the constant pressure high pressure air stored in the cavern is discharged into the heat exchanger through the gas pipeline, after the high pressure air is heated through the heat exchanger, the turbine expansion generator drives the turbine expansion generator to generate electricity, and the generated electricity is input into the ground power grid; S4. Water storage reset: after the energy release power generation is completed, the electric booster water pump continues to inject the water in the surface reservoir into the cavern, until the water fills the cavern again, and the state remains unchanged until the next cycle.

3. The multi-stage segmented compressed underground constant pressure compressed air energy storage system of claim 1 or 2, wherein, The valve control system comprises a first air valve, a second air valve and a water valve, the first air valve is arranged on the compressed air flow path between the second cooler and the third stage compressor, the second air valve is arranged on the compressed air flow path between the second cooler and the cavern, and the surface reservoir is connected with the water pipeline through the water valve and the electric booster water pump in sequence.

4. The multi-stage segmented compressed underground constant pressure compressed air energy storage system of claim 3, wherein, The gas outlet of the first stage compressor is connected with the gas inlet of the first cooler, the gas outlet of the first cooler is connected with the gas inlet of the second stage compressor, the gas outlet of the second stage compressor is connected with the gas inlet of the second cooler, the gas outlet of the second cooler is connected with the gas inlet of the third stage compressor through the first air valve, the gas outlet of the second cooler is connected with the first gas pipeline through the second air valve, the gas outlet of the third stage compressor is connected with the gas inlet of the third cooler, the gas outlet of the third cooler is connected with the gas inlet of the fourth stage compressor, the gas outlet of the fourth stage compressor is connected with the gas inlet of the fourth cooler, the gas outlet of the fourth cooler is connected with the second gas pipeline, the liquid outlets of the first cooler, the second cooler, the third cooler and the fourth cooler are connected with the liquid inlets of the heat storage tank respectively, the liquid outlet of the heat storage tank is connected with the hot side inlet of the heat exchanger, the hot side outlet of the heat exchanger is connected with the liquid inlet of the cold storage tank, the liquid outlet of the cold storage tank is connected with the liquid inlets of the first cooler, the second cooler, the third cooler and the fourth cooler respectively, the first gas pipeline, the second gas pipeline and the gas pipeline are respectively inserted into the cavern through the gas vertical shaft, the outlet gas of the turbine expansion generator is communicated with the atmosphere, and the water pipeline is inserted into the cavern through the water vertical shaft.

5. The multi-stage segmented compressed underground constant pressure compressed air energy storage system of claim 1, wherein, The inner wall of the cavern is provided with a heat insulation sealing layer.

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