Compressed gas energy storage system coupled with residual pressure power generation and operation method

Abstract

The invention discloses a compressed gas energy storage system for coupling residual pressure power generation, which relates to the technical field of compressed gas energy storage and comprises a compression energy storage system, an expansion power generation system, a heat storage and exchange system and a gas storage system. The system further comprises an excess pressure heat storage system and an excess pressure power generation system. The excess pressure heat storage system comprises an excess pressure high-temperature heat storage tank and an excess pressure low-temperature heat storage tank. The residual pressure power generation system comprises a residual pressure expansion machine, a gear box, a residual pressure power generator and a residual pressure heat exchanger. Compared with existing conventional compressed gas energy storage, the gas storage can be effectively used for storing excess pressure potential energy of high-pressure gas, throttling loss of a conventional system expansion machine is reduced, station electricity consumption is reduced, the on-grid electricity quantity of a power station is improved, and therefore the electricity-electricity conversion efficiency of the power station and the operation economical efficiency of the power station are improved.

Description

Technical Field

[0001] This invention relates to the field of compressed gas energy storage technology, and more specifically to a compressed gas energy storage system coupled with residual pressure power generation; the invention also relates to a method for operating such a compressed gas energy storage system coupled with residual pressure power generation. Background Technology

[0002] Compressed gas energy storage systems include various gas energy storage systems such as compressed air energy storage and compressed CO2 energy storage. They are currently recognized as large-capacity, ultra-long-term energy storage technologies comparable to pumped hydro storage. In recent years, they have been extensively studied in China, and several demonstration projects have been carried out. Currently, the largest single-unit capacity of a compressed gas energy storage power station that has been officially connected to the grid reaches 300MW.

[0003] The working principle of the compressed gas energy storage system is as follows: During the off-peak period of power grid consumption or by using the curtailed wind and solar power of new energy sources, an electric compressor is used to compress gas, which is then compressed into high pressure and stored in a gas storage tank. At the same time, the heat generated during the compression process is decoupled and stored in a heat storage medium. During the peak period of power consumption, the high-pressure gas stored in the gas storage tank is released, heated by the stored heat storage medium, and then sent to an expander to generate electricity.

[0004] Compressed gas energy storage systems typically use fixed-volume gas storage tanks. During energy release, the gas pressure inside the storage tank gradually decreases as high-pressure gas is released. To ensure stable output of the expander generator unit during energy release, the following two expander inlet regulation schemes are generally adopted: One method is to use throttling regulation, that is, the expander uses the minimum pressure of the gas storage tank as the rated inlet pressure. When the pressure of the gas storage tank is higher than the minimum pressure, the high-pressure gas is reduced to the minimum pressure through the throttling valve set at the inlet of the expander before being sent into the expander. Secondly, a throttling + gas replenishment regulation is adopted. The expander is generally rated as the midpoint of the gas storage pressure range. When the gas storage pressure is higher than the rated inlet pressure, the regulation method is the same as the throttling regulation scheme, that is, the pressure is reduced to the rated inlet pressure by using the throttling valve at the expander inlet; when the gas storage pressure is lower than the rated inlet pressure, the throttling valve is fully opened, and a high-pressure gas is led from the front of the throttling valve to the intermediate stage of the expander for gas replenishment.

[0005] Both of the above schemes can enable the expander generator unit to operate at rated output within the entire working pressure range of the gas storage tank, each with its own advantages and disadvantages. The throttling regulation scheme only uses one throttling valve, making the system simple, but throttling losses exist throughout the entire process, resulting in lower system efficiency. The throttling + gas replenishment regulation scheme uses both a throttling valve and a gas replenishment valve, making the system complex and difficult to control, but throttling losses only exist within the range above the rated intake pressure, resulting in higher system efficiency. Regardless of which scheme is adopted, there are certain throttling losses during the expansion power generation process, which affects the economic operation of the power plant.

[0006] Therefore, it is necessary to develop a compressed gas energy storage system and its operation method that effectively reduces the high-pressure gas throttling loss during the expansion stage of a compressed gas energy storage power station, improves the power station's electro-electric conversion efficiency, and has good economic benefits by coupling residual pressure power generation. Summary of the Invention

[0007] The purpose of this invention is to overcome the problem of increased system losses caused by high-pressure gas throttling regulation during the expansion power generation stage in existing compressed gas energy storage systems described in the background art. This invention improves the system's electro-electric conversion efficiency and enhances the operational economy of compressed gas energy storage power stations.

[0008] To achieve the aforementioned first objective, the technical solution of the present invention is as follows: a compressed gas energy storage system coupled with residual pressure power generation, comprising a compressed energy storage system, an expansion power generation system, a heat exchange system, and a gas storage tank system; the compressed energy storage system comprises n compressors connected in series; the expansion power generation system comprises m expanders and generators connected in series; the heat exchange system comprises a heat storage system, a heat exchange system, and a cooling tower, the heat storage system comprises a high-temperature storage tank and a low-temperature storage tank, and the heat exchange system comprises n compression-side heat exchangers and m expansion-side heat exchangers; both the high-temperature storage tank and the low-temperature storage tank are connected to the n compression-side heat exchangers and the m expansion-side heat exchangers; Adjacent compressors are connected via compression-side heat exchangers. The nth compressor is connected to the gas storage system via the nth compression-side heat exchanger. The cooling tower is connected to the nth compression-side heat exchanger. The gas storage system is connected to the first-stage expander through the first expansion-side heat exchanger, and adjacent expanders are connected through expansion-side heat exchangers. Its features include: a residual pressure thermal storage system and a residual pressure power generation system, wherein the residual pressure thermal storage system includes a residual pressure high-temperature thermal storage tank and a residual pressure low-temperature thermal storage tank, and both the residual pressure high-temperature thermal storage tank and the residual pressure low-temperature thermal storage tank are connected to the nth compression-side heat exchanger; The waste pressure power generation system includes a waste pressure expander, a gearbox, a waste pressure generator, and a waste pressure heat exchanger. The first expansion-side heat exchanger is connected to the gas storage system in sequence through the waste pressure expander and the waste pressure heat exchanger. The waste pressure generator is connected to the waste pressure expander through the gearbox. The waste pressure high-temperature heat storage tank and the waste pressure low-temperature heat storage tank are both connected to the waste pressure heat exchanger.

[0009] In the above technical solution, the first expansion-side heat exchanger is connected to the residual pressure expander through a residual pressure power generation outlet shut-off valve; the residual pressure heat exchanger is connected to the gas storage system through a residual pressure power generation inlet shut-off valve.

[0010] In the above technical solution, the nth compression-side heat exchanger is connected to the gas storage system through a compression-side shut-off valve, and the gas storage system is connected to the residual pressure power generation inlet shut-off valve through an expansion-side shut-off valve.

[0011] In the above technical solution, the residual pressure power generation system also includes a bypass system. The bypass system includes a residual pressure power generation bypass and a residual pressure power generation bypass valve installed on the residual pressure power generation bypass. One end of the residual pressure power generation bypass is connected between the residual pressure power generation outlet shut-off valve and the first expansion side heat exchanger, and the other end is connected between the expansion side shut-off valve and the residual pressure power generation inlet shut-off valve.

[0012] In the above technical solution, the residual pressure generator is connected to the station's power supply system.

[0013] In the above technical solution, both the residual pressure high-temperature heat storage tank and the residual pressure low-temperature heat storage tank are atmospheric pressure tanks, and water is used as the heat storage medium.

[0014] In the above technical solution, the outlet pressure of the residual pressure expander is the rated inlet pressure of the expander.

[0015] In the above technical solution, n=4 and m=3.

[0016] To achieve the second objective mentioned above, the technical solution of the present invention is: an operation method of a compressed gas energy storage system coupled with residual pressure power generation, characterized in that it includes an energy storage stage and an energy release stage; The energy storage stage includes the following steps: ambient gas or gas from a low-pressure gas storage facility is compressed to a high-pressure state through each stage of compressors. The high-temperature gas from the outlets of the first three compressors is cooled down in the first three compression-side heat exchangers, and the heat of compression is stored in a high-temperature storage tank through a heat storage medium. The medium-temperature gas from the outlet of the fourth compressor is cooled down in the fourth compression-side heat exchanger, and part of the heat of compression is stored in a residual pressure high-temperature heat storage tank through a heat storage medium. The excess heat of compression is dissipated through a cooling tower. The cooled high-pressure gas is stored in the gas storage system. The energy release stage includes the following steps: When the pressure of the gas storage system is above the rated inlet pressure of the expander: the waste pressure power generation bypass valve is closed, and the waste pressure power generation inlet shut-off valve and waste pressure power generation outlet shut-off valve are opened. The high-pressure gas from the gas storage system first enters the waste pressure power generation system. The heat storage medium in the waste pressure high-temperature heat storage tank enters the waste pressure heat exchanger to heat the high-pressure gas and then enters the waste pressure expander to do work, converting the waste pressure potential energy of the high-pressure gas from the gas storage system into the mechanical energy of the waste pressure expander, and then driving the waste pressure generator to convert the mechanical energy into electrical energy. The high-pressure air at the outlet of the residual pressure expander enters the expansion power generation system. After being heated by the expansion-side heat exchanger at the inlet of each stage of expander, it enters each stage of expander to do work and generate electricity. The outlet of the residual pressure generator is connected to the power station's auxiliary power system, reducing the generator's power consumption and thus improving the power station's power conversion efficiency and economy.

[0017] In the above technical solution, when the pressure of the gas storage system drops below the rated inlet pressure of the expander or when the residual pressure power generation system malfunctions, the residual pressure power generation bypass valve is opened, and the residual pressure power generation inlet shut-off valve and the residual pressure power generation outlet shut-off valve are closed. High-pressure gas from the gas storage system enters the expansion power generation system through the residual pressure power generation bypass.

[0018] Compared with the prior art, the present invention has the following advantages: 1) Compared with existing conventional compressed gas energy storage, this invention can effectively utilize the residual pressure potential energy of high-pressure gas in the gas storage tank, reduce the throttling loss of the expander in conventional systems, reduce the power consumption of the station, increase the power grid connection of the power station, thereby improving the power conversion efficiency and the economic efficiency of the power station operation.

[0019] 2) When the residual pressure power generation system fails or the gas storage pressure drops below the rated inlet pressure of the expander, the bypass system of the present invention will be activated to isolate the residual pressure power generation system, ensuring that the power station operates according to the conventional regulation scheme and improving the reliability and safety of the compressed gas energy storage system. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the present invention.

[0021] Figure 2 This is a schematic diagram of the existing technology.

[0022] Among them, 100-compression energy storage system, 110-compressor, 111-motor, 200-expansion power generation system, 210-expander, 211-generator, 300-heat exchange system, 310-heat storage system, 311-high temperature storage tank, 312-low temperature storage tank, 320-heat exchange system, 321-compression side heat exchanger, 322-expansion side heat exchanger, 330-cooling tower, 400-gas storage system, 411-compression side shut-off valve, 412-expansion... Expansion-side shut-off valve, 500-Residual pressure thermal storage system, 510-Residual pressure high-temperature thermal storage tank, 520-Residual pressure low-temperature thermal storage tank, 600-Residual pressure power generation system, 610-Residual pressure expander, 620-Gearbox, 630-Residual pressure generator, 640-Residual pressure heat exchanger, 651-Residual pressure power generation outlet shut-off valve, 652-Residual pressure power generation inlet shut-off valve, 660-Bypass system, 661-Residual pressure power generation bypass, 662-Residual pressure power generation bypass valve, 700-Station power supply system. Detailed Implementation

[0023] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but these descriptions are not intended to limit the invention and are merely illustrative. The advantages of the present invention will become clearer and easier to understand through this description.

[0024] like Figure 1 As shown, a compressed gas energy storage system coupled with residual pressure power generation includes a compressed energy storage system 100, an expansion power generation system 200, a heat exchange system 300, and a gas storage tank system 400. The compressed energy storage system 100 includes n compressors 110 connected in series. The expansion power generation system 200 includes m expanders 210 and generators 211 connected in series. The heat exchange system 300 includes a heat storage system 310, a heat exchange system 320, and a cooling tower 330. The heat storage system 310 includes a high-temperature storage tank 311 and a low-temperature storage tank 312. The heat exchange system 320 includes n compression-side heat exchangers 321 and m expansion-side heat exchangers 322. Both the high-temperature storage tank 311 and the low-temperature storage tank 312 are connected to the n compression-side heat exchangers 321 and the m expansion-side heat exchangers 322. Adjacent compressors 110 are connected by a compression-side heat exchanger 321. The nth compressor 110 is connected to the gas storage system 400 through the nth compression-side heat exchanger 321. The cooling tower 330 is connected to the nth compression-side heat exchanger 321. The gas storage system 400 is connected to the first-stage expander 210 through the first expansion-side heat exchanger 322, and adjacent expanders 210 are connected through the expansion-side heat exchanger 322. It also includes a waste pressure heat storage system 500 and a waste pressure power generation system 600. The waste pressure heat storage system 500 includes a waste pressure high temperature heat storage tank 510 and a waste pressure low temperature heat storage tank 520. Both the waste pressure high temperature heat storage tank 510 and the waste pressure low temperature heat storage tank 520 are connected to the nth compression-side heat exchanger 321. The waste pressure power generation system 600 includes a waste pressure expander 610, a gearbox 620, a waste pressure generator 630, and a waste pressure heat exchanger 640. The first expansion-side heat exchanger 322 is connected to the gas storage system 400 in sequence through the waste pressure expander 610 and the waste pressure heat exchanger 640. The waste pressure generator 630 is connected to the waste pressure expander 610 through the gearbox 620. The waste pressure high-temperature heat storage tank 510 and the waste pressure low-temperature heat storage tank 520 are both connected to the waste pressure heat exchanger 640.

[0025] The first expansion-side heat exchanger 322 is connected to the residual pressure expander 610 via the residual pressure power generation outlet shut-off valve 651; the residual pressure heat exchanger 640 is connected to the gas storage system 400 via the residual pressure power generation inlet shut-off valve 652.

[0026] The nth compression-side heat exchanger 321 is connected to the gas storage system 400 via the compression-side shut-off valve 411, and the gas storage system 400 is connected to the residual pressure power generation inlet shut-off valve 652 via the expansion-side shut-off valve 412.

[0027] The waste pressure power generation system 600 also includes a bypass system 660, which includes a waste pressure power generation bypass 661 and a waste pressure power generation bypass valve 662 disposed on the waste pressure power generation bypass 661. One end of the waste pressure power generation bypass 661 is connected between the waste pressure power generation outlet shut-off valve 651 and the first expansion side heat exchanger 322, and the other end is connected between the expansion side shut-off valve 412 and the waste pressure power generation inlet shut-off valve 652.

[0028] The residual pressure generator 630 is connected to the station power system 700.

[0029] Both the residual pressure high-temperature heat storage tank 510 and the residual pressure low-temperature heat storage tank 520 are atmospheric pressure tanks, and water is used as the heat storage medium.

[0030] The outlet pressure of the residual pressure expander 610 is the rated inlet pressure of the expander 210.

[0031] With n=4 and m=3, this formula can also be applied to other schemes such as n=3, m=2, n=2 and m=2, n=4 and m=4 in practice.

[0032] An operation method for a compressed gas energy storage system coupled with residual pressure power generation, comprising an energy storage stage and an energy release stage; The energy storage stage includes the following steps: ambient gas or gas from a low-pressure gas storage facility is compressed to a high-pressure state through each stage of compressor 110. The high-temperature gas from the outlet of the first three stage compressors 110 is cooled down in the first three compression-side heat exchangers 321, and the heat of compression is stored in the high-temperature storage tank 311 through the heat storage medium. The medium-temperature gas from the outlet of the fourth stage compressor 110 is cooled down in the fourth compression-side heat exchanger 321, and part of the heat of compression is stored in the residual pressure high-temperature heat storage tank 510 through the heat storage medium. The excess heat of compression is dissipated through the cooling tower 330. The high-pressure gas after cooling down is stored in the gas storage system 400. The energy release stage includes the following steps: When the pressure of the gas storage system 400 is above the rated inlet pressure of the expander 210: the residual pressure power generation bypass valve 662 is closed, and the residual pressure power generation inlet shut-off valve 652 and the residual pressure power generation outlet shut-off valve 651 are opened. The high-pressure gas from the gas storage system 400 first enters the residual pressure power generation system 600. The heat storage medium in the residual pressure high-temperature heat storage tank 510 enters the residual pressure heat exchanger 640 to heat the high-pressure gas and then enters the residual pressure expander 610 to do work, converting the residual pressure potential energy of the high-pressure gas from the gas storage system 400 into the mechanical energy of the residual pressure expander 610, and then driving the residual pressure generator 630 to convert the mechanical energy into electrical energy. The high-pressure air at the outlet of the residual pressure expander 610 enters the expansion power generation system 200, and after being heated by the expansion-side heat exchanger 322 at the inlet of each stage expander 210, it enters each stage expander 210 to do work and generate electricity. The outlet of the residual pressure generator 630 is connected to the power station's auxiliary power system 700, thereby improving the power station's power conversion efficiency and economy.

[0033] When the pressure in the gas storage system 400 drops below the rated inlet pressure of the expander 210 or when the residual pressure power generation system 600 malfunctions, the residual pressure power generation bypass valve 662 is opened, and the residual pressure power generation inlet shut-off valve 652 and the residual pressure power generation outlet shut-off valve 651 are closed. High-pressure gas from the gas storage system 400 enters the expander power generation system 200 through the residual pressure power generation bypass valve 661.

[0034] In practical use, the function of the compression energy storage system 100 is to compress atmospheric or low-pressure gas step by step to a high-pressure state. The compression energy storage system 100 includes a multi-stage compressor or a multi-stage compressor. This invention is described using a multi-stage compressor. The compressor 110 can be an axial flow compressor, a centrifugal compressor, or a multi-shaft gearbox compressor. Each compressor 110 is connected to an electric motor 111.

[0035] In the expansion power generation system 200, each of the m-stage expanders 210 connected in series is connected to a generator 211. The function of the expansion power generation system 200 is to use the gas storage system 400 to do work with the high-pressure gas, converting the potential energy of the high-pressure gas into mechanical energy, thereby driving the generator 211 to generate electricity. The function of the compression-side heat exchanger 321 in the heat exchange system 320 is to cool the high-temperature gas at the outlet of the compressor 110 during the energy storage stage, thereby reducing the inlet temperature of the next stage or next-stage compressor 110; and to transfer the heat stored in the high-temperature storage tank 311 to the expansion-side heat exchanger 322 in the heat exchange system 320 through the heat storage medium during the energy release stage to heat the gas. The heat storage medium in the heat exchange system 320 can be water, molten salt, heat transfer oil, or solid heat storage medium.

[0036] The main function of the gas storage system 400 is to store the compressed high-pressure gas during the compression stage and release the gas during the energy release stage. Gas storage facilities can be underground salt cavern gas storage facilities, artificial chamber gas storage facilities, or surface pressure vessel gas storage facilities.

[0037] The residual pressure expander 610 is selected as a single-stage or multi-stage expander according to the amount of residual pressure energy that can be released. Its function is to use the high-pressure gas from the gas storage system 400 to expand and do work. During operation, its inlet pressure gradually decreases with the pressure of the gas storage system 400, and the outlet pressure is stabilized at the rated inlet pressure of the expander 210 in the conventional compressed gas energy storage system, so as to make full use of the high-pressure potential energy lost during the throttling of the expander's high-pressure inlet.

[0038] The gearbox 620 is configured according to system requirements and can be either a speed-increasing or speed-reducing gearbox. Its function is to match the speed of the residual pressure expander 610 with the speed of the residual pressure generator 630.

[0039] The function of the residual pressure generator 630 is to convert the mechanical energy of the residual pressure expander 610 into electrical energy. The outlet of the residual pressure generator 630 is connected to the station power system 700 of the compressed gas energy storage power station. The power generated by the residual pressure generator 630 is used as station power consumption, thereby reducing the power generation consumption of the conventional expander 211 and increasing the power grid connection of the power station.

[0040] The heat source for the residual pressure heat exchanger 640 comes from the heat stored in the residual pressure heat storage system 500, which is used to heat the high-pressure gas at the inlet of the residual pressure expander 610, ensuring that the exhaust parameters of the residual pressure expander 610 operate according to the rated inlet parameters of the expander 210 in a conventional compressed air energy storage system. The residual pressure heat exchanger can be installed on the inlet or outlet side of the residual pressure expander 610 as needed.

[0041] The function of the bypass system 660 is to isolate the residual pressure power generation system 600 when the residual pressure power generation system 600 fails or the pressure of the gas storage system 400 drops below the rated intake pressure of the expander 210, so as to ensure that the power station operates according to the conventional regulation scheme.

[0042] Example The solution of the present invention is compared with the throttling regulation solution and the throttling + gas replenishment regulation solution in the prior art: Taking a 300MW compressed air energy storage power station as an example, the compressor operates for 8 hours and the expander operates for 5 hours. The inlet pressure range of its expander 210 is 8-6MPa.

[0043] When the expander 210 uses throttling + supplemental air regulation, that is, when the rated intake pressure of the expander 210 is 7MPa, when the incoming air pressure of the gas storage system 400 is between 8-7MPa, throttling regulation is used, and the intake pressure is adjusted to 7MPa through the regulating valve; when the incoming air pressure of the gas storage system 400 is between 7-6MPa, the throttling valve is fully open, and the supplemental air valve is opened to supplement air.

[0044] After adding the waste pressure power generation system 600, the intake pressure of the waste pressure expander 610 is 8-7 MPa. After the exhaust pressure of the waste pressure expander 610 stabilizes at 7 MPa, it enters the conventional expansion power generation system 200 (the regulating valve is not throttled and remains fully open). According to calculations, the maximum output of the waste pressure generator 630 can reach 8MW, and the entire energy release process can generate 20MWh of electricity. The power station's electricity-to-electricity conversion efficiency can be improved by 0.91%, which is a significant effect.

[0045] When the expander 210 adopts a throttling regulation scheme for air intake, the maximum output of the residual pressure power generation system 600 can reach 16.5MW, and the entire energy release process can generate 41MWh of electricity. The power station's power-to-power conversion efficiency can be improved by 1.86%, and the effect is more obvious.

[0046] In summary, compared with existing technologies, the compressed gas energy storage system and operation method of this invention, which uses coupled residual pressure power generation, can effectively utilize the residual pressure potential energy of high-pressure gas in the gas storage tank, reduce the throttling losses of the expander in conventional systems, reduce the power consumption of the station, increase the grid-connected power of the power station, thereby improving the power conversion efficiency and the economic efficiency of the power station operation.

[0047] All other unspecified parts belong to the prior art.

Claims

1. A compressed gas energy storage system coupled with residual pressure power generation, comprising a compressed energy storage system (100), an expansion power generation system (200), a heat exchange system (300), and a gas storage tank system (400); the compressed energy storage system (100) comprises n compressors (110) connected in series; the expansion power generation system (200) comprises m expanders (210) and generators (211) connected in series; the heat exchange system (300) comprises a gas storage tank... The system comprises a thermal system (310), a heat exchange system (320), and a cooling tower (330). The thermal storage system (310) includes a high-temperature storage tank (311) and a low-temperature storage tank (312). The heat exchange system (320) includes n compression-side heat exchangers (321) and m expansion-side heat exchangers (322). Both the high-temperature storage tank (311) and the low-temperature storage tank (312) are connected to the n compression-side heat exchangers (321) and the m expansion-side heat exchangers (322). Adjacent compressors (110) are connected by a compression-side heat exchanger (321), the nth compressor (110) is connected to the gas storage system (400) through the nth compression-side heat exchanger (321), and the cooling tower (330) is connected to the nth compression-side heat exchanger (321). The gas storage system (400) is connected to the first-stage expander (210) through the first expansion-side heat exchanger (322), and adjacent expanders (210) are connected through expansion-side heat exchangers (322); Its features are: It also includes a residual pressure thermal storage system (500) and a residual pressure power generation system (600). The residual pressure thermal storage system (500) includes a residual pressure high-temperature thermal storage tank (510) and a residual pressure low-temperature thermal storage tank (520). Both the residual pressure high-temperature thermal storage tank (510) and the residual pressure low-temperature thermal storage tank (520) are connected to the nth compression-side heat exchanger (321). The waste pressure power generation system (600) includes a waste pressure expander (610), a gearbox (620), a waste pressure generator (630), and a waste pressure heat exchanger (640). The first expansion-side heat exchanger (322) is connected to the gas storage system (400) in sequence through the waste pressure expander (610) and the waste pressure heat exchanger (640). The waste pressure generator (630) is connected to the waste pressure expander (610) through the gearbox (620). The waste pressure high-temperature heat storage tank (510) and the waste pressure low-temperature heat storage tank (520) are both connected to the waste pressure heat exchanger (640).

2. The compressed gas energy storage system for coupled residual pressure power generation according to claim 1, characterized in that: The first expansion-side heat exchanger (322) is connected to the residual pressure expander (610) via the residual pressure power generation outlet shut-off valve (651); the residual pressure heat exchanger (640) is connected to the gas storage system (400) via the residual pressure power generation inlet shut-off valve (652).

3. The compressed gas energy storage system for coupled residual pressure power generation according to claim 2, characterized in that: The nth compression-side heat exchanger (321) is connected to the gas storage system (400) via the compression-side shut-off valve (411), and the gas storage system (400) is connected to the residual pressure power generation inlet shut-off valve (652) via the expansion-side shut-off valve (412).

4. The compressed gas energy storage system for coupled residual pressure power generation according to claim 3, characterized in that: The waste pressure power generation system (600) also includes a bypass system (660), which includes a waste pressure power generation bypass (661) and a waste pressure power generation bypass valve (662) installed on the waste pressure power generation bypass (661). One end of the waste pressure power generation bypass (661) is connected between the waste pressure power generation outlet shut-off valve (651) and the first expansion side heat exchanger (322), and the other end is connected between the expansion side shut-off valve (412) and the waste pressure power generation inlet shut-off valve (652).

5. A compressed gas energy storage system for coupled residual pressure power generation according to claim 4, characterized in that: The residual pressure generator (630) is connected to the station power system (700).

6. The compressed gas energy storage system for coupled residual pressure power generation according to claim 1, characterized in that: Both the residual pressure high-temperature heat storage tank (510) and the residual pressure low-temperature heat storage tank (520) are atmospheric pressure tanks, and water is used as the heat storage medium.

7. The compressed gas energy storage system for coupled residual pressure power generation according to claim 1, characterized in that: The outlet pressure of the residual pressure expander (610) is the rated inlet pressure of the expander (210).

8. A compressed gas energy storage system for coupled residual pressure power generation according to claim 5, characterized in that: n=4, m=3.

9. The operation method of a compressed gas energy storage system coupled with residual pressure power generation according to claim 8, characterized in that, Includes the energy storage phase and the energy release phase; The energy storage stage includes the following steps: ambient gas or gas from a low-pressure gas storage tank is compressed to a high-pressure state through each stage of compressors (110). The high-temperature gas from the outlet of the first three stage compressors (110) is cooled down in the first three compression-side heat exchangers (321) and the heat of compression is stored in the high-temperature storage tank (311) through the heat storage medium. The medium-temperature gas from the outlet of the fourth stage compressor (110) is cooled down in the fourth compression-side heat exchanger (321) and part of the heat of compression is stored in the residual pressure high-temperature heat storage tank (510) through the heat storage medium. The excess heat of compression is dissipated through the cooling tower (330). The high-pressure gas after cooling down is stored in the gas storage system (400). The energy release stage includes the following steps: When the pressure of the gas storage system (400) is above the rated inlet pressure of the expander (210): the residual pressure power generation bypass valve (662) is closed, the residual pressure power generation inlet shut-off valve (652) and the residual pressure power generation outlet shut-off valve (651) are opened, the high pressure gas from the gas storage system (400) first enters the residual pressure power generation system (600), the heat storage medium in the residual pressure high temperature heat storage tank (510) enters the residual pressure heat exchanger (640) to heat the high pressure gas and then enters the residual pressure expander (610) to do work, converting the residual pressure potential energy of the high pressure gas from the gas storage system (400) into the mechanical energy of the residual pressure expander (610), and then driving the residual pressure generator (630) to convert the mechanical energy into electrical energy; The high-pressure air from the outlet of the residual pressure expander (610) enters the expansion power generation system (200), and after being heated by the expansion-side heat exchanger (322) at the inlet of each stage of expander (210), it enters each stage of expander (210) to do work and generate electricity. The outlet of the residual pressure generator (630) is connected to the power station's auxiliary power system (700), reducing the power consumption of the generator (211) and thus improving the power conversion efficiency and economy of the power station.

10. The operation method of a compressed gas energy storage system coupled with residual pressure power generation according to claim 9, characterized in that: When the pressure of the gas storage system (400) drops below the rated inlet pressure of the expander (210) or when the residual pressure power generation system (600) malfunctions, the residual pressure power generation bypass valve (662) is opened, and the residual pressure power generation inlet shut-off valve (652) and the residual pressure power generation outlet shut-off valve (651) are closed. The high-pressure gas from the gas storage system (400) enters the expander power generation system (200) through the residual pressure power generation bypass (661).

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