A compressed air energy storage system and method

Abstract

The application provides a compressed air energy storage system and method, and relates to the technical field of energy storage.The compressed air energy storage system comprises a compression device, a multistage gas storage device and a multistage expansion device.The multistage gas storage device comprises a main gas storage device and a plurality of sub gas storage devices.The gas inlet of the main gas storage device is communicated with the gas outlet of the compression device.The first gas outlet of the main gas storage device is respectively communicated with the gas inlets of the sub gas storage devices.The multistage expansion device comprises a plurality of sub expansion machines connected in series.The gas inlet of the multistage expansion device is communicated with the second gas outlet of the main gas storage device.The gas inlet of each sub expansion machine is communicated with the gas outlet of the corresponding sub gas storage device.The compressed air energy storage system has a wide adjustable operation range when releasing energy, and the operation boundary of the system is expanded.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, specifically to a compressed air energy storage system and method. Background Technology

[0002] Compressed air energy storage technology is a novel energy storage technology. It involves storing large amounts of renewable energy using compressed air under high pressure, and then releasing the compressed air to generate electricity during peak electricity demand periods (such as daytime). Compressed air energy storage technology offers advantages such as large storage capacity, long storage period, low investment, and environmental friendliness, and thus has broad development prospects.

[0003] Existing compressed air energy storage systems mostly employ non-combustion adiabatic compression systems. During energy storage, atmospheric air must be compressed to high pressure for storage, and the heat of compression must be recovered through a heat exchanger. During energy release, the high-pressure air is expanded to atmospheric pressure via a multi-stage series expander and then discharged into the atmosphere. Due to the limitations of the expander's normal operating range, the operating range of a multi-stage series expander is essentially the same as that of a single-stage expander, approximately 30%-100%. Since the system's energy release process is essentially the expander generating electricity, the expander's operating range is the same as the system's adjustable operating range during energy release. This results in a narrow adjustable operating range for compressed air energy storage systems during energy release, significantly hindering their widespread adoption and application. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is that the operating range of the expander in the existing compressed air energy storage system is relatively narrow, which leads to the defect that the adjustable operating range during energy release is also narrow. The present invention provides a compressed air energy storage system and method with a wider operating range of the expander and a wider adjustable operating range during energy release, thereby expanding the energy release operating boundary of the system.

[0005] To address the above problems, the present invention provides a compressed air energy storage system, comprising:

[0006] Compression device;

[0007] A multi-stage gas storage device includes a main gas storage device and several stage gas storage devices. The inlet of the main gas storage device is connected to the outlet of the compression device, and the first outlet of the main gas storage device is connected to the inlet of each stage gas storage device.

[0008] The multi-stage expansion device includes several stage expanders connected in series. The air inlet of the multi-stage expansion device is connected to the second air outlet of the main gas storage device, and the air inlet of each stage expander is connected to the corresponding air outlet of the stage gas storage device.

[0009] As a preferred technical solution for the compressed air energy storage system, it also includes a pressure regulating device, which is installed on the pipeline between the second air outlet and the air inlet of the multi-stage expander. Each stage expander is connected to the pressure regulating device through a bypass pipeline.

[0010] As a preferred technical solution for compressed air energy storage systems, the pressure regulating device includes an ejector.

[0011] As a preferred technical solution for the compressed air energy storage system, it also includes a heat exchange device, which includes a first heat exchanger, a second heat exchanger and an interstage heat exchanger. The first heat exchanger is installed on the pipeline between the outlet of the compression device and the inlet of the main air storage device. The second heat exchanger is installed between the pressure regulating device and the inlet of the multi-stage expansion device. The interstage heat exchanger is installed on the pipeline between the inlets of two adjacent stages of the stage expander.

[0012] As a preferred technical solution for compressed air energy storage systems, a bypass regulating valve is provided on the bypass pipeline.

[0013] As a preferred technical solution for compressed air energy storage systems, the bypass pipeline shown is equipped with an isolation valve.

[0014] As a preferred technical solution for the compressed air energy storage system, it also includes an energy storage device, wherein the first heat exchanger, the second heat exchanger and the interstage heat exchanger are connected to the energy storage device.

[0015] As a preferred technical solution for compressed air energy storage system, the energy storage device includes a high-temperature thermal storage unit and a low-temperature thermal storage unit, which are connected to each other.

[0016] As a preferred technical solution for compressed air energy storage systems, each stage of the graded air storage device is equipped with an air storage inlet switch component at the air inlet and an air storage outlet switch component at the air outlet.

[0017] A compressed air energy storage method, wherein the multi-stage gas storage device of the compressed air energy storage system includes a main gas storage device, a first stage gas storage device, and a second stage gas storage device, and the multi-stage expansion device of the compressed air energy storage system includes a first stage expander, a second stage expander, and a third stage expander, and the compressed air energy storage method includes an energy storage process and an energy release process.

[0018] The energy release process includes the following steps:

[0019] S21, Expansion and Energy Release: The main gas storage device generates electricity by expanding high-pressure compressed air through the first stage expander, the second stage expander and the third stage expander; after the system stabilizes, the pressure at the outlet of the main gas storage device is regulated by the compressed air at the outlet of the first stage expander and the pressure regulating device.

[0020] S22, Low-load expansion and energy release: Adjust the airflow at the inlet of each stage expander;

[0021] S23, Ultra-low load expansion and energy release: After compressed air generates electricity by performing work through the first stage expander and the second stage expander, it is stored in the second stage gas storage device; if the power generation load is further reduced, the compressed air generates electricity only by performing work through the first stage expander and is stored in the first stage gas storage device.

[0022] S24. Exhausting gas from the staged gas storage tank: Close the first outlet of the main gas storage device and close the isolation valve. The exhaust from the second staged gas storage device drives the third staged expander to do work until the pressure of the second staged gas storage device drops to the minimum. Then close the gas discharge switch at the outlet of the second staged gas storage device. Then open the isolation valve. The exhaust from the first staged gas storage device directly drives the third staged expander to do work until the pressure of the first staged gas storage device drops to the minimum and the exhaust is completed.

[0023] The technical solution of this invention has the following advantages:

[0024] 1. The compressed air energy storage system provided by this invention includes a compression device, a multi-stage air storage device, and a multi-stage expansion device. The multi-stage air storage device includes a main air storage device and several staged air storage devices. The air inlet of the main air storage device is connected to the air outlet of the compression device, and the first air outlet of the main air storage device is connected to the air inlet of each staged air storage device. The multi-stage expansion device includes several staged expanders connected in series. The air inlet of the multi-stage expansion device is connected to the second air outlet of the main air storage device, and the air inlet of each staged expander is connected to the corresponding air outlet of the staged air storage device. By setting up a multi-stage air storage device, which cooperates with the multi-stage expansion device, the compressed air energy storage system of this invention allows for the switching of individual operation of each staged expander and the corresponding staged air storage device. This achieves independent operation of the series-connected multi-stage expansion devices, increases the operating range of the expanders and the adjustable operating range during system energy release, expands the system's energy release operating boundary, and avoids the problem of reduced expander efficiency caused by low-load operation of the multi-stage expanders, thus achieving efficient and stable system operation.

[0025] 2. The compressed air energy storage system provided by this invention further includes a pressure regulating device, which is installed on the pipeline between the second air outlet and the air inlet of the multi-stage expander. Each stage expander is connected to the pressure regulating device via a bypass pipeline. By connecting each stage expander to the pressure regulating device through the bypass pipeline, and by using a pressure regulating ejector to eject the exhaust gas discharged from the outlet of each stage expander, the compressed air pressure is regulated. This avoids the throttling losses caused by the throttling valve in traditional technology, thereby improving the efficiency of the compressed air energy storage system.

[0026] 3. The compressed air energy storage system provided by the present invention further includes a heat exchange device, which comprises a first heat exchanger, a second heat exchanger, and an interstage heat exchanger. The first heat exchanger is disposed on the pipeline between the outlet of the compressor and the inlet of the main air storage device. The second heat exchanger is disposed between the pressure regulating device and the inlet of the multi-stage expander. The interstage heat exchanger is disposed on the pipeline between the inlets of two adjacent stage expanders. By setting up the first heat exchanger, the high-pressure, high-temperature air compressed by the compressor is heat-exchanged, transforming the high-temperature, high-pressure air into high-pressure, low-temperature air before entering the main air storage device. By setting up the second heat exchanger, the high-pressure, high-temperature air passing through the pressure regulating device is heat-exchanged, allowing the high-temperature, high-pressure air to enter the multi-stage expander. By setting up the interstage heat exchanger, the air between each stage expander can be heated to meet the system operation requirements.

[0027] 4. The compressed air energy storage system provided by the present invention further includes an energy storage device. A first heat exchanger, a second heat exchanger, and an interstage heat exchanger are all connected to the energy storage device. The energy storage device includes a high-temperature heat storage unit and a low-temperature heat storage unit, which are connected to each other. By setting up the energy storage device, the first heat exchanger, the second heat exchanger, and the interstage heat exchanger transfer and store the heat released during gas compression in the high-temperature heat storage unit. This heat is used to heat the compressed air during expansion. The low-temperature heat storage unit stores the low-temperature heat exchange medium after heat exchange, allowing the heat exchange medium to be recycled. This avoids energy waste, improves energy utilization efficiency, and significantly reduces the operating cost of the compressed air energy storage system.

[0028] 5. The compressed air energy storage system provided by this invention has an air inlet switch component at the air inlet of each stage of the air storage device and an air outlet switch component at the air outlet. By setting switch components at the air inlet and outlet of each stage of the air storage device, the individual operation of each stage of the air storage device can be controlled, achieving efficient and stable system operation and improving system operating efficiency.

[0029] 6. The compressed air energy storage method provided by the present invention, since it includes the above-mentioned compressed air energy storage system, has the beneficial effects of the compressed air energy storage system, which will not be elaborated here. Attached Figure Description

[0030] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the compressed air energy storage system of the present invention.

[0032] Explanation of reference numerals in the attached figures:

[0033] 1. Compression unit; 2. Main gas storage unit; 3. First-stage gas storage unit; 4. Second-stage gas storage unit; 5. Electric motor; 6. Ejector; 7. First-stage expander; 8. Second-stage expander; 9. Third-stage expander; 10. Generator; 11. First heat exchanger; 12. Second heat exchanger; 13. Third heat exchanger; 14. Fourth heat exchanger; 15. Heat storage tank; 16. Cold storage tank; 17. Gas storage bypass; 18. Bypass pipeline; 19. Bypass regulating valve; 20. First-stage inter-stage pipeline valve; 21. Second-stage inter-stage pipeline valve; 22. First-stage gas storage inlet valve; 23. Second-stage gas storage inlet valve; 24. First-stage gas storage outlet valve; 25. Second-stage gas storage outlet valve; 26. Isolation valve. Detailed Implementation

[0034] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] like Figure 1 The diagram shows a preferred embodiment of the compressed air energy storage system of the present invention. This compressed air energy storage system has a wide adjustable operating range during energy release, thus expanding the system's energy release operating boundaries.

[0039] The compressed air energy storage system of this embodiment includes a compression device, a multi-stage air storage device, and a multi-stage expansion device. The multi-stage air storage device includes a main air storage device 2 and several staged air storage devices. The air inlet of the main air storage device 2 is connected to the air outlet of the compression device, and the first air outlet of the main air storage device 2 is connected to the air inlet of each staged air storage device. The multi-stage expansion device includes several staged expanders connected in series. The air inlet of the multi-stage expansion device is connected to the second air outlet of the main air storage device 2, and the air outlet of each staged expander is connected to the corresponding staged air storage device's air outlet.

[0040] The multi-stage gas storage device in this embodiment includes a main gas storage device 2, a first-stage gas storage device 3, and a second-stage gas storage device 4. All three devices are gas storage tanks. The compression device 1 includes one or more compressors. Atmospheric pressure air is compressed by the compressors and stored in the main gas storage device 2. The main gas storage device 2 is connected to the first-stage gas storage device 3 and the second-stage gas storage device 4 via a gas storage bypass 17. The multi-stage expansion device of the compressed air energy storage system includes a first-stage expander 7, a second-stage expander 8, and a third-stage expander 9. The outlet of each expander is connected to a generator 10.

[0041] The aforementioned compressed air energy storage system, by setting up multi-stage air storage devices, can switch between the operation of each stage expander and the corresponding stage air storage device, thereby realizing the independent operation of the series-connected multi-stage expanders. This improves the operating range of the expanders and the adjustable operating range during system energy release, expands the system's energy release operating boundary, and avoids the problem of reduced expander efficiency caused by low-load operation of multi-stage expanders, thus achieving efficient and stable system operation.

[0042] In a preferred embodiment, the compressed air energy storage system of this embodiment further includes a pressure regulating device, which is disposed on the pipeline between the second air outlet and the air inlet of the multi-stage expander. Each stage expander is connected to the pressure regulating device through a bypass pipeline 18. Specifically, as Figure 1 As shown, the inlet of the pressure regulating device is connected to the second outlet, and the outlet of the pressure regulating device is connected to the inlet of the first stage expander 7. Furthermore, the first stage expander 7, the second stage expander 8, and the third stage expander 9 are connected to the inlet of the pressure regulating device through the bypass pipeline 18. By setting up the pressure regulating device, the outlet pressure of the main gas storage device 2 can be regulated, which reduces the throttling loss caused by throttling when the multi-stage expander is running at low load, and improves the efficiency and stability of the system operation.

[0043] In a preferred embodiment, the pressure regulating device includes an ejector 6. A second outlet is connected to the inlet of the ejector 6 to allow compressed air stored in the main air storage device 2 to be introduced into the ejector 6. The outlet of the ejector 6 is connected to the first stage expander 7 to allow depressurized air to be introduced into the first stage expander 7. At the same time, each stage expander is connected to the ejector 6 through a bypass pipe 18. The ejector 6 ejects the exhaust gas discharged from the outlet of each stage expander, mixing the high-pressure air with the lower-pressure exhaust gas between the stages of the expander, reducing the overall inlet pressure of the expander and increasing the flow rate, thereby regulating the compressed air pressure. This avoids the throttling losses caused by the throttling valve in conventional technology and improves the efficiency of the compressed air energy storage system.

[0044] In a preferred embodiment, a bypass regulating valve 19 is provided on the bypass pipeline 18. Specifically, as shown... Figure 1 As shown, a bypass regulating valve 19 is provided on the bypass pipeline 18 between the ejector 6 and the first stage expander 7, a first interstage pipeline valve 20 is provided on the bypass pipeline 18 between the first stage expander 7 and the second stage expander 8, and a second interstage pipeline valve 21 is provided on the bypass pipeline 18 between the second stage expander 8 and the third stage expander 9. The bypass regulating valve 19, the first interstage pipeline valve 20, and the second interstage pipeline valve 21 are all connected to the controller. The controller regulates the flow rate in the bypass pipeline 18 by controlling the bypass regulating valve 19, the first interstage pipeline valve 20, and the second interstage pipeline valve 21, thereby regulating the flow rate of the exhaust gas discharged from the outlet of each stage expander. The ejector 6 ejects the exhaust gas discharged from the outlet of each stage expander, thereby regulating the pressure of the compressed air.

[0045] In a preferred embodiment, an isolation valve 26 is also provided on the bypass pipeline 18. Specifically, as shown... Figure 1As shown, the isolation valve 26 is installed on the bypass line 18 between the first stage expander 7 and the third stage expander 9. The isolation valve 26 can prevent air in the bypass line 18 from flowing from the third stage expander 9 to the first stage expander 7.

[0046] In a preferred embodiment, the compressed air energy storage system of this embodiment further includes a heat exchange device, which includes a first heat exchanger 11, a second heat exchanger 12, and an interstage heat exchanger. The first heat exchanger 11 is disposed on the pipeline between the outlet of the compressor and the inlet of the main air storage device 2. The second heat exchanger 12 is disposed between the pressure regulating device and the inlet of the multi-stage expander. The interstage heat exchanger is disposed on the pipeline between the inlets of two adjacent stage expanders. Specifically, as shown... Figure 1 As shown, the interstage heat exchangers include a third heat exchanger 13 and a fourth heat exchanger 14. The third heat exchanger 13 is located between the first stage expander 7 and the second stage expander 8, and the fourth heat exchanger 14 is located between the second stage expander 8 and the third stage expander 9. The first heat exchanger 11, the second heat exchanger 12, the third heat exchanger 13, and the fourth heat exchanger 14 are direct contact heat exchangers, such as gas condensers, where hot and cold fluids directly contact each other for heat exchange. By setting the first heat exchanger 11, the high-pressure, high-temperature air compressed by the compression device is heat-exchanged, transforming the high-temperature, high-pressure air into high-pressure, low-temperature air before entering the main gas storage device 2. By setting the second heat exchanger 12, the high-pressure, high-temperature air passing through the pressure regulating device is heat-exchanged, allowing the high-temperature, high-pressure air to enter the multi-stage expander. By setting up interstage heat exchangers, the air between each stage expander can be heated to meet the system operating requirements and ensure the efficient and stable operation of the system.

[0047] In a preferred embodiment, the system further includes an energy storage device, wherein the first heat exchanger 11, the second heat exchanger 12, and the interstage heat exchanger are all connected to the energy storage device; the energy storage device includes a high-temperature thermal storage unit and a low-temperature thermal storage unit, which are connected to each other. Specifically, as shown... Figure 1As shown, the high-temperature thermal storage unit includes a thermal storage tank 15, and the low-temperature thermal storage unit includes a cold storage tank 16. A first heat exchanger 11 is installed on the pipeline between the compression device 1 and the main gas storage device 2. The first heat exchanger 11 is connected to the thermal storage tank 15 and the cold storage tank 16. High-pressure, high-temperature air is stored in the main gas storage device 2 after heat exchange through the first heat exchanger 11, and the released heat is stored in the thermal storage tank 15. At the same time, the low-temperature heat exchange medium after heat exchange is stored in the cold storage tank 16. A second heat exchanger 12 is installed on the pipeline between the ejector 6 and the first stage expander 7. The second heat exchanger 12 is connected to the thermal storage tank 15 and the cold storage tank 16. High-pressure, low-temperature air is entered into the first stage expander 7 after heat exchange through the second heat exchanger 12, and the low-temperature heat exchange medium after heat exchange is stored in the cold storage tank 16. The warm heat exchange medium is stored in the cold storage tank 16. The third heat exchanger 13 heats the air between the first stage expander 7 and the second stage expander 8, and the fourth heat exchanger 14 heats the air between the second stage expander 8 and the third stage expander 9. The first heat exchanger 11 and the second heat exchanger 12 transfer and store the heat released during gas compression in the heat storage tank 15. This heat is used to heat the gas during expansion, utilizing the heat of compression. The cold storage tank 16 stores the low-temperature heat exchange medium after heat exchange. The third heat exchanger 13 and the fourth heat exchanger 14 use this heat of compression to heat the air between each stage expander, making the heat exchange medium recyclable. This avoids energy waste, improves energy utilization efficiency, and greatly reduces the cost of compressed air energy storage.

[0048] In a preferred embodiment, each stage of the gas storage device is equipped with a gas inlet switch at the inlet and a gas outlet switch at the outlet. Specifically, as shown... Figure 1 As shown, the gas inlet switch component includes a primary gas inlet valve 22 and a secondary gas inlet valve 23, and the gas outlet switch component includes a primary gas outlet valve 24 and a secondary gas outlet valve 25. The primary gas inlet valve 22 is located at the inlet of the first-stage gas storage device 3, the primary gas outlet valve 24 is located at the outlet of the first-stage gas storage device 3, the secondary gas inlet valve 23 is located at the inlet of the second-stage gas storage device 4, and the secondary gas outlet valve 25 is located at the outlet of the second-stage gas storage device 4. The primary gas inlet valve 22, the secondary gas inlet valve 23, the primary gas outlet valve 24, and the secondary gas outlet valve 25 are all connected to the controller. By setting up gas storage inlet switch components and gas storage outlet switch components, the controller controls the opening and closing of the first stage gas storage device 3 and the second stage gas storage device 4 by controlling the first stage gas storage inlet valve 22, the second stage gas storage inlet valve 23, the first stage gas storage outlet valve 24 and the second stage gas storage outlet valve 25, so as to realize the control of a single stage gas storage device and a single stage expander, thereby improving the system operating efficiency.

[0049] This embodiment also proposes a compressed air energy storage method. The multi-stage compressed air energy storage system includes a main air storage device 2, a first-stage air storage device 3, and a second-stage air storage device 4. The multi-stage expansion device of the compressed air energy storage system includes a first-stage expander 7, a second-stage expander 8, and a third-stage expander 9. The compressed air energy storage method includes an energy storage process and an energy release process. The energy storage process involves compressing atmospheric pressure air into high-temperature, high-pressure air using a compression device, and then filling the main air storage device 2 and several staged air storage devices with this air. The specific steps are as follows:

[0050] S11. Start-up preparation: Close the bypass regulating valve 19, the primary gas storage discharge valve 24, and the secondary gas storage discharge valve 25. Open the valves at the inlet of the main gas storage device 2, the primary gas storage inlet valve 22, and the secondary gas storage inlet valve 23 to ensure unobstructed gas storage bypass 17. S12. Multi-stage gas storage preparation: Start the compressor, the first heat exchanger 11, and the second heat exchanger 12 to charge the main gas storage device 2, the first stage gas storage device 3, and the second stage gas storage device 4. When the compressed air pressure reaches the minimum operating pressure P2min of the second stage gas storage device 4, close the secondary gas storage inlet valve 23. Then continue charging. When the compressed air pressure reaches the minimum operating pressure P1min of the first stage gas storage device 3, close the primary gas storage inlet valve 22 to complete the multi-stage gas storage preparation. S13. Compressed energy storage: Continue charging the main gas storage device 2 through the compressor to complete the energy storage process.

[0051] The energy release process includes the following steps:

[0052] S21, Expansion and Energy Release: The main gas storage device 2 generates electricity by expanding high-pressure compressed air through the first stage expander 7, the second stage expander 8 and the third stage expander 9; after the system stabilizes, the pressure at the outlet of the main gas storage device 2 is regulated by the compressed air at the outlet of the first stage expander 7 and the pressure regulating device.

[0053] S22, Low-load expansion and energy release: Adjust the airflow at the inlet of each stage expander;

[0054] S23, Ultra-low load expansion and energy release: After compressed air generates electricity by doing work through the first stage expander 7 and the second stage expander 8, it is stored in the second stage gas storage device 4; if the power generation load is further reduced, the compressed air generates electricity only by doing work through the first stage expander 7 and is stored in the first stage gas storage device 3.

[0055] S24. Exhausting gas from the staged gas storage tank: Close the first outlet of the main gas storage device 2 and close the isolation valve 26. The exhaust of the second staged gas storage device 4 drives the third staged expander 9 to do work until the pressure of the second staged gas storage device 4 drops to the minimum. Then close the gas discharge switch component at the outlet of the second staged gas storage device 4. Then open the isolation valve 26. The exhaust of the first staged gas storage device 7 directly drives the third staged expander 9 to do work until the pressure of the first staged gas storage device 7 drops to the minimum and the exhaust is completed.

[0056] The energy release process includes three steps: expansion energy release, low-load expansion energy release, and ultra-low-load expansion energy release. Specifically, the expansion energy release process involves the simultaneous activation of the first-stage expander 7, the second-stage expander 8, and the third-stage expander 9, causing the three expanders to operate in series. The main gas storage device 2 generates electricity by expanding the high-pressure compressed air through the first-stage expander 7 and the generator 10 connected to it, the second-stage expander 8 and the generator 10 connected to it, and the third-stage expander 9 and the generator 10 connected to it. The third heat exchanger... 13 heats the compressed air entering through the first stage expander 7, and the fourth heat exchanger 14 heats the compressed air entering through the second stage expander 8. After the system stabilizes, the bypass regulating valve 19 is opened so that the compressed air at the outlet of the first stage expander 7 and the ejector 6 regulate the outlet pressure of the main gas storage device 2. The pressure regulating ejector 6 ejects the exhaust gas discharged from the outlet of each stage expander, thereby regulating the compressed air pressure. This avoids the throttling loss caused by the throttling valve in traditional technology and improves the efficiency of the compressed air energy storage system.

[0057] During the low-load expansion and energy release process, the air flow is regulated by the inlet regulating valves of the first stage expander 7, the second stage expander 8, and the third stage expander 9. This simultaneously regulates the air flow entering the first stage expander 7, the second stage expander 8, and the third stage expander 9, reducing the air flow into all three stages. Consequently, the output power of the series-connected first stage expander 7, the second stage expander 8, and the third stage expander 9 is reduced, leading to a decrease in the power generation of the generators 10 connected to each of them. This low-load expansion and energy release process, by adjusting the air flow at the inlet of each stage expander, reduces the operating condition of the compressed air energy storage system from 100% to 30%.

[0058] In the ultra-low load expansion energy release process, by decoupling the multi-stage expansion devices, each stage expander can operate independently. Specifically, the secondary gas storage discharge valve 25 is opened, and the first-stage inter-pipeline valve 20 and the second-stage inter-pipeline valve 21 are closed. After the compressed air generates electricity by passing through the first-stage expander 7 and the second-stage expander 8, it is stored in the second-stage gas storage device 4. To further reduce the power generation load, the primary gas storage discharge valve 24 is opened, and the secondary gas storage discharge valve 25, the first-stage inter-pipeline valve 20, and the second-stage inter-pipeline valve 21 are closed. After the compressed air generates electricity by passing through the first-stage expander 7 alone, it is stored in the first-stage gas storage device 3. This ultra-low load expansion and energy release process can switch between the first stage expander 7 and the second stage expander 8 working simultaneously to generate electricity or only through the first stage expander 7. This allows the system's operating condition to continue to decrease from 30% to 10% or below, increasing the operating range of the expanders and the adjustable operating range of the system during energy release. The operating range is increased from 30% to 100% to 10% or below to 100%, expanding the system's energy release operating boundary and avoiding the problem of reduced expander efficiency caused by low-load operation of multi-stage expanders, thus achieving efficient and stable system operation.

[0059] During the venting process of the staged gas storage tank in the energy release process, the first outlet of the main gas storage device (2) is closed, the isolation valve (26) is closed, the second stage gas storage device (4) vents and drives the third stage expander (9) to do work until the second stage gas storage device (4) is reduced to the minimum pressure and then the secondary gas storage discharge valve (25) is closed; then the isolation valve (26) is opened, the first stage gas storage device (7) vents and directly drives the third stage expander (9) to do work until the first stage gas storage device (7) is reduced to the minimum pressure and then the venting process is completed.

[0060] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A compressed air energy storage method for a compressed air energy storage system, characterized in that, The compressed air energy storage system includes: Compression device (1); The multi-stage gas storage device includes a main gas storage device (2) and several graded gas storage devices. The inlet of the main gas storage device (2) is connected to the outlet of the compression device (1), and the first outlet of the main gas storage device (2) is connected to the inlet of the graded gas storage device. The multi-stage expansion device includes several stage expanders connected in series. The air inlet of the multi-stage expansion device is connected to the second air outlet of the main gas storage device (2). The air inlet of each stage expander is connected to the air outlet of the corresponding stage gas storage device. The device also includes a pressure regulating device, which is installed on the pipeline between the second air outlet and the air inlet of the multi-stage expansion device. Each stage expander is connected to the pressure regulating device through a bypass pipeline (18). The bypass pipeline (18) is equipped with an isolation valve (26). The compressed air energy storage system includes a multi-stage gas storage device (2), a first-stage gas storage device (3), and a second-stage gas storage device (4). The compressed air energy storage system also includes a multi-stage expansion device (7), a first-stage expansion device (8), and a third-stage expansion device (9). The compressed air energy storage method includes an energy storage process and an energy release process. The energy release process includes the following steps: S21, Expansion and Energy Release: The main gas storage device (2) generates electricity by expanding high-pressure compressed air through the first stage expander (7), the second stage expander (8) and the third stage expander (9); after the system stabilizes, the pressure at the outlet of the main gas storage device (2) is adjusted by the compressed air at the outlet of the first stage expander (7) and the pressure regulating device. S22, Low-load expansion and energy release: Adjust the airflow at the inlet of each stage expander; S23, Ultra-low load expansion and energy release: After compressed air generates electricity by doing work through the first stage expander (7) and the second stage expander (8), it is stored in the second stage gas storage device (4); If the power generation load is further reduced, the compressed air generates electricity only by doing work through the first stage expander (7) and is stored in the first stage gas storage device (3). S24. Exhausting gas from the graded gas storage tank: Close the first outlet of the main gas storage device (2), close the isolation valve (26), exhaust the gas from the second graded gas storage device (4) to drive the third graded expander (9) to do work until the second graded gas storage device (4) is reduced to the minimum pressure, then close the gas discharge switch component at the outlet of the second graded gas storage device (4); then open the isolation valve (26), exhaust the gas from the first graded gas storage device (3) to directly drive the third graded expander (9) to do work until the first graded gas storage device (3) is reduced to the minimum pressure, then exhaust is completed.

2. The compressed air energy storage method of the compressed air energy storage system according to claim 1, characterized in that, The pressure regulating device includes an ejector (6).

3. The compressed air energy storage method of the compressed air energy storage system according to claim 1, characterized in that, It also includes a heat exchange device, which includes a first heat exchanger (11), a second heat exchanger (12) and an interstage heat exchanger. The first heat exchanger (11) is installed on the pipeline between the outlet of the compression device (1) and the inlet of the main gas storage device (2). The second heat exchanger (12) is installed between the pressure regulating device and the inlet of the multi-stage expansion device. The interstage heat exchanger is installed on the pipeline between the inlets of two adjacent stages of the stage expander.

4. The compressed air energy storage method of the compressed air energy storage system according to claim 1, characterized in that, A bypass regulating valve (19) is installed on the bypass pipeline (18).

5. The compressed air energy storage method of the compressed air energy storage system according to claim 3, characterized in that, It also includes an energy storage device, and the first heat exchanger (11), the second heat exchanger (12) and the interstage heat exchanger are all connected to the energy storage device.

6. The compressed air energy storage method of the compressed air energy storage system according to claim 5, characterized in that, The energy storage device includes a high-temperature thermal storage unit and a low-temperature thermal storage unit, which are connected to each other.

7. The compressed air energy storage method of the compressed air energy storage system according to any one of claims 1 to 2, characterized in that, Each stage of the graded gas storage device is equipped with a gas storage inlet switch at the air inlet and a gas storage outlet switch at the air outlet.

Images