A Compressed Air Energy Storage System and Method

Abstract

The present invention provides a compressed air energy storage system and method, relating to the technical field of compressed air energy storage. The compressed air energy storage system provided by the present invention includes an air energy storage unit, a pressure regulating device, an expansion device, a return bypass, and a controller. The air energy storage unit includes a compression device and a gas storage device, and the gas storage device is provided with a gas storage outlet; the pressure regulating device is provided with an inlet end, an outlet end, and a return end, and the inlet end is connected to the gas storage outlet; the total expansion inlet of the expansion device is connected to the pressure regulating device; one end of the return bypass is connected to the expansion return port, and the other end is connected to the return end; the controller is electrically connected to the pressure regulating device, and the controller is configured to detect the control target value of the pressure regulating device so as to automatically adjust the operating conditions of the pressure regulating device based on the control target value. The compressed air energy storage system and method of the present invention improve the work capacity of compressed air, reduce the heat loss of the system, and improve the system efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of compressed air energy storage, and in particular to a compressed air energy storage system and method. Background Art

[0002] The compressed air system draws electricity from the power grid, drives a compression system to compress atmospheric air into high-pressure gas and store it in a gas storage device, completing the conversion from electrical energy to compression energy and heat energy. A large amount of compression heat is generated during the compression process, and a heat storage and heat exchange system needs to be set up to recover the compression heat. The compressed air in the gas storage device enters the expansion system to do work through a throttle valve and a heat exchanger, adjusting the pressure and temperature of the compressed air, and driving a generator to generate electricity to complete the energy release process.

[0003] In order to reduce the volume of the gas storage device, the operating pressure range of the compressed air gas storage device is relatively wide, and a throttle valve needs to be set to adjust the gas pressure at the inlet of the expander to ensure the normal operation of the system. However, the throttle valve will cause throttling losses of high-pressure compressed air, reduce the temperature of the compressed air, resulting in a decrease in the work capacity of the compressed air, and increase the heat exchange loss of the heat exchange system, thereby reducing the efficiency of the compressed air energy storage system. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is the defect that the throttle valve in the prior art causes throttling losses of high-pressure compressed air, reduces the work capacity of the compressed air, and causes large heat losses in the compressed air system and low system efficiency. Thus, a compressed air energy storage system and method are provided to improve the work capacity of the compressed air, reduce system heat losses, and improve system efficiency.

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

[0006] An air energy storage unit, including a compression device and a gas storage device, the gas storage device is provided with a gas storage outlet;

[0007] A pressure regulating device, provided with an inlet end, an outlet end and a return end, the inlet end is connected to the gas storage outlet;

[0008] An expansion device, provided with an expansion inlet and an expansion return port, the expansion inlet is connected to the pressure regulating device;

[0009] A return bypass, one end is connected to the expansion return port, and the other end of the return bypass is connected to the return end;

[0010] A controller, the controller is electrically connected to the pressure regulating device, and the controller is configured to detect the control target value of the pressure regulating device to automatically adjust the operating condition of the pressure regulating device based on the control target value.

[0011] Preferably, the pressure regulating device includes a pressure regulating expander, a pressure regulating compressor, a pressure regulating motor, and a pressure regulating generator;

[0012] The pressure regulating expander and the pressure regulating compressor are connected by a shaft through a gearbox. The pressure regulating motor and the pressure regulating compressor are connected by a first coupling. The pressure regulating generator and the pressure regulating expander are connected by a second coupling. The pressure regulating motor and the pressure regulating generator are respectively connected to a controller.

[0013] Preferably, the control target values include the target outlet pressure of the pressure regulating device, the operating outlet pressure, and the return air pressure in the return bypass.

[0014] Preferably, the compressed air energy storage system further includes an energy storage device. The energy storage device includes a high-temperature heat storage unit and a low-temperature heat storage unit that exchange heat through the circulation of a heat transfer working medium and store heat.

[0015] The high-temperature heat storage unit is used to exchange heat of the high-temperature and high-pressure compressed air into high-pressure and low-temperature air and store the heat. The low-temperature heat storage unit is used to store the low-temperature heat transfer working medium after heat exchange of the heat transfer working medium.

[0016] Preferably, a compression device is further included. A first heat exchanger is provided between the compression device and the gas storage device. The first heat exchanger is connected to the high-temperature heat storage unit. The high-pressure and high-temperature air is stored in the gas storage device after heat exchange through the first heat exchanger, and the released heat is stored in the high-temperature heat storage unit.

[0017] Preferably, a second heat exchanger is provided between the pressure regulating device and the expansion device. The second heat exchanger is connected to the high-temperature heat storage unit and the low-temperature heat storage unit. The high-pressure and low-temperature air enters the expansion device after heat exchange through the second heat exchanger, and the heat transfer working medium that releases heat returns to the low-temperature heat storage unit for storage.

[0018] Preferably, a preheating heat exchange device is further provided at the inlet end of the pressure regulating device. The preheating heat exchange device is connected to the high-temperature heat storage unit and the low-temperature heat storage unit.

[0019] Preferably, the expansion device includes at least two stages of expanders connected in series. A return bypass is provided in any stage or each stage of the expander. A third heat exchanger is provided between adjacent two stages of expanders. The third heat exchanger is connected to the high-temperature heat storage unit and the low-temperature heat storage unit.

[0020] Preferably, a bypass regulating valve and a flow meter are provided on the reflux bypass, and the bypass regulating valve and the flow meter are connected to the controller.

[0021] Another technical problem to be solved by the present invention lies in the defects of the prior art that a throttle valve is used to reduce the work capacity of compressed air, resulting in large heat loss in the compressed air system and low system efficiency. Therefore, a compressed air energy storage method for a compressed air energy storage system is provided, which can improve the work capacity of compressed air, reduce system heat loss, and improve system efficiency.

[0022] To solve the above problems, the present invention provides a compressed air energy storage method, including:

[0023] S1. In the energy storage state, atmospheric air is compressed by the compression device to become high-temperature and high-pressure air, and then exchanges heat with the heat exchange working medium through the first heat exchanger, and becomes high-pressure and low-temperature compressed air and enters the gas storage device for storage;

[0024] S2. In the energy release state, the high-pressure and low-temperature compressed air obtained in S1 flows out of the gas storage device, is heated by the preheating heat exchange device of the compressed air energy storage system, and then enters the pressure regulating device;

[0025] S3. The compressed air is depressurized and expanded by the pressure regulating expansion machine of the pressure regulating device, and the final pressure is 100 kPa lower than the pressure of the inter-stage reflux air;

[0026] S4. Open the bypass regulating valve, and the compressed air in the reflux bypass is mixed with the compressed air at the outlet of the pressure regulating expansion machine and enters the pressure regulating compressor;

[0027] S5. Adjust the power of the pressure regulating compressor so that the outlet pressure of the pressure regulating device reaches the control target value, and compare the power of the adjusted pressure regulating compressor with the power of the pressure regulating expansion machine;

[0028] S6. When the power of the pressure regulating expansion machine is greater than the power of the pressure regulating compressor, disconnect the first coupling on the side of the pressure regulating motor, and the pressure regulating device generates electricity externally through the pressure regulating generator; otherwise, disconnect the second coupling on the side of the pressure regulating generator, and the pressure regulating device draws power from the power grid to drive the pressure regulating compressor to do work;

[0029] S7. The compressed air flowing out of the pressure regulating device is heated and enters the expansion device to do work and generate electricity.

[0030] The technical solution of the present invention has the following advantages:

[0031] 1. The compressed air energy storage system provided by the present invention includes an air energy storage unit, a pressure regulating device, an expansion device, a reflux bypass, and a controller. The air energy storage unit includes a compression device and a gas storage device, and the gas storage device is provided with a gas storage air outlet; the pressure regulating device is provided with an inlet end, an outlet end, and a reflux end, and the inlet end is connected to the gas storage air outlet; the expansion device is provided with a total expansion air inlet and an expansion reflux port, and the total expansion air inlet is connected to the pressure regulating device; one end of the reflux bypass is connected to the expansion reflux port, and the other end is connected to the reflux end; the controller is electrically connected to the pressure regulating device, and the controller is configured to detect the control target value of the pressure regulating device to automatically adjust the operating condition of the pressure regulating device based on the control target value. By setting the pressure regulating device and setting an inter-stage reflux bypass for the expansion device, the throttling cooling phenomenon caused by using a throttle valve in the traditional technology is avoided, the temperature of the compressed air before the expander is indirectly increased, the waste of high-temperature heat exchange medium in the heat exchange system is avoided, the high-pressure air is mixed with the low-pressure exhaust gas at the inter-stage pressure of the expansion device, the total inlet pressure of the expansion device is reduced and the flow rate is increased, the throttling loss and the system heat loss are reduced, and the system efficiency is improved.

[0032] 2. The compressed air energy storage system provided by the present invention can stabilize the exhaust pressure of the gas storage device by setting a pressure regulating device, which includes a pressure regulating expander, a pressure regulating compressor, a pressure regulating motor, and a pressure regulating generator, and avoid the unstable operation of the expansion device caused by the fluctuation of the exhaust pressure of the gas storage device, thereby improving the system safety. At the same time, the pressure working range of the expansion device for doing work is expanded. When the exhaust pressure of the gas storage device is lower than the minimum working pressure, the pressure regulating compressor can also be started to increase the compressed air pressure to meet the system working requirements.

[0033] 3. The pressure regulating device of the compressed air energy storage system provided by the present invention further includes a compressed air mixer. By setting the compressed air mixer, the compressed air entering the pressure regulating device can be mixed with the reflux air in the reflux bypass, the high-pressure air is mixed with the low-pressure exhaust gas at the inter-stage pressure of the expansion device, the total inlet pressure of the expansion device is reduced and the flow rate is increased, the throttling loss is avoided, and the system efficiency is improved.

[0034] 4. The compressed air energy storage system provided by the present invention further includes an energy storage device. The heat storage device includes a high-temperature heat storage unit and a low-temperature heat storage unit. A first heat exchanger is arranged between the compression device and the gas storage device. The first heat exchanger is connected to the high-temperature heat storage unit. The high-pressure and high-temperature air exchanges heat through the first heat exchanger and is stored in the gas storage device, and at the same time, the released heat is stored in the high-temperature heat storage unit; a second heat exchanger is arranged between the pressure regulating device and the expansion device. The second heat exchanger is connected to the high-temperature heat storage unit and the low-temperature heat storage unit. The high-pressure and low-temperature air exchanges heat through the second heat exchanger and then enters the expansion device. At the same time, the low-temperature heat exchange medium after heat exchange of the heat exchange medium is stored in the low-temperature heat storage unit. By setting the energy storage device, the compression heat is utilized, thereby avoiding energy waste, improving the energy utilization efficiency, and greatly reducing the cost of compressed air energy storage.

[0035] 5. In the compressed air energy storage system provided by the present invention, a preheating heat exchange device is arranged at the inlet end of the pressure regulating device. The preheating heat exchange device is connected to the high-temperature heat storage unit and the low-temperature heat storage unit. By setting the preheating heat exchanger device, the heat generated during the compression of the compressed air is stored through the high-temperature heat storage unit, and then the compressed air coming out of the gas storage device is preheated, improving the energy utilization rate.

[0036] 6. Since the compressed air energy storage method provided by the present invention is the energy storage method of the above-mentioned compressed air energy storage system, the compressed air energy storage method has the beneficial effects of the compressed air energy storage system, which will not be elaborated here. Description of the Drawings

[0037] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0038] Figure 1 It is a schematic structural diagram of the compressed air energy storage system of the present invention;

[0039] Figure 2 It is a schematic structural diagram of the pressure regulating device of the compressed air energy storage system of the present invention.

[0040] Description of the Reference Numerals:

[0041] 1. Motor; 2. Compressor; 3. Gas storage device; 4. Pressure regulating device; 401. Pressure regulating expander; 402. Pressure regulating compressor; 403. Gearbox; 404. Pressure regulating motor; 405. First coupling; 406. Pressure regulating generator; 407. Second coupling; 408. Compressed air mixer; 5. First-stage expander; 6. Second-stage expander; 7. Heat storage tank; 8. First heat exchanger; 9. Cold storage tank; 10. Second heat exchanger; 11. Third heat exchanger; 12. Return bypass; 13. Bypass regulating valve; 14. Generator; 15. Preheating heat exchanger; 16. Controller; 17. Flowmeter. Detailed implementation mode

[0042] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work fall within the protection scope of the present invention.

[0043] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0044] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0045] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0046] Embodiment 1

[0047] Such as Figure 1 And Figure 2Shown is a specific implementation of a compressed air energy storage system. The compressed air energy storage system includes an air energy storage unit, a pressure regulating device 4, an expansion device, and a return bypass 12. The air energy storage unit includes a gas storage device 3, and the gas storage device 3 is provided with a gas storage outlet. The pressure regulating device 4 is provided with an inlet end, an outlet end, and a return end, and the inlet end is connected to the gas storage outlet. The expansion device is provided with a total expansion inlet and an expansion return port, and the total expansion inlet is connected to the pressure regulating device 4. One end of the return bypass 12 is connected to the expansion return port, and the other end is connected to the return end.

[0048] In the compressed air energy storage system of this embodiment, by setting the pressure regulating device 4 and setting the inter-stage return bypass 12 of the expansion device, the throttling cooling phenomenon caused by using a throttle valve in the traditional technology is avoided, the temperature of the compressed air before the expander is indirectly increased, the waste of high-temperature heat exchange medium in the heat exchange system is avoided, the high-pressure air is mixed with the low-pressure exhausted gas at the inter-stage pressure of the expansion device, the pressure at the total inlet of the expansion device is reduced and the flow rate is increased, the throttling loss and the system heat loss are reduced, and the system efficiency is improved.

[0049] Further, as Figure 1 and Figure 2 shown, the pressure regulating device 4 includes a pressure regulating expander 401, a pressure regulating compressor 402, a pressure regulating motor 404, and a pressure regulating generator 406. The pressure regulating expander 401 and the pressure regulating compressor 402 are connected by a gearbox 403 in a shaft connection. The pressure regulating motor 404 and the pressure regulating compressor 402 are connected by a first coupling 405. The pressure regulating generator 406 and the pressure regulating expander 401 are connected by a second coupling 407. The pressure regulating motor 404 and the pressure regulating generator 406 are respectively connected to the controller 16.

[0050] The above-mentioned pressure regulating device 4 is arranged between the gas storage device 3 and the expansion device. The gas storage device 3 may include one or more high-pressure gas storage tanks. The compression device is one or more compressors 2. The atmospheric air is compressed by the compressors 2 and stored in the gas storage tank. The gas storage tank can withstand a pressure of more than 10 MPa. By adding the pressure regulating device 4, the exhaust pressure of the gas storage device 3 can be stabilized, the unstable operation phenomenon of the expansion device caused by the exhaust pressure fluctuation of the gas storage device 3 can be avoided, and the system safety is improved. At the same time, the pressure working range of the expansion device for doing work is expanded. When the exhaust pressure of the gas storage device 3 is lower than the minimum working pressure, the pressure regulating compressor 402 of the pressure regulating device 4 can also be started to increase the pressure of the compressed air to meet the system working requirements.

[0051] The above-mentioned pressure regulating device 4 further includes a compressed air mixer 408, which is used to mix the compressed air entering the pressure regulating device 4 with the return air in the return bypass 12. In this embodiment, the compressed air mixer 408 is a Y-shaped compressed air mixer. The compressed air mixer 408 includes a first branch and a second branch. The inlet of the first branch is connected to the outlet of the return bypass 12, and the second branch is connected to the pressure regulating expander 401 and the pressure regulating compressor 402. The first branch communicates with the second branch. By providing the compressed air mixer 408, the compressed air entering the pressure regulating device 4 can be mixed with the return air in the return bypass 12, and the high-pressure air can be mixed with the low-pressure exhausted air at the intermediate stage of the expansion device, ensuring the stability of the output mixed air, reducing the total inlet pressure of the expansion device and increasing the flow rate, avoiding throttling losses, and improving the system efficiency.

[0052] Further, as Figure 1 shown, the compressed air energy storage system further includes an energy storage device. The energy storage device includes a high-temperature heat storage unit and a low-temperature heat storage unit that exchange heat through the circulation of a heat transfer working medium and store heat; the high-temperature heat storage unit is used to exchange heat the high-temperature and high-pressure compressed air into high-pressure and low-temperature air and store the heat, and the low-temperature heat storage unit is used to store the low-temperature heat transfer working medium after the heat transfer working medium exchanges heat.

[0053] Specifically, the high-temperature heat storage unit includes a heat storage tank 7, and the low-temperature heat storage unit includes a cold storage tank 9. A first heat exchanger 8 is provided between the compressor 2 and the gas storage tank. The first heat exchanger 8 is connected to the heat storage tank 7. The high-pressure and high-temperature air exchanges heat through the first heat exchanger 8 and is stored in the gas storage tank, and the released heat is stored in the heat storage tank 7. At the same time, the low-temperature heat transfer working medium after the heat transfer working medium exchanges heat is stored in the cold storage tank 9. A second heat exchanger 10 is provided between the pressure regulating device 4 and the expansion device. The second heat exchanger 10 is connected to the heat storage tank 7 and the cold storage tank 9. The high-pressure and low-temperature air exchanges heat through the second heat exchanger 10 and then enters the expansion device. At the same time, the low-temperature heat transfer working medium after the heat transfer working medium exchanges heat is stored in the cold storage tank 9. The first heat exchanger 8 and the second heat exchanger 10 adopt direct contact heat exchangers, such as gas condensers, where the hot and cold fluids directly contact for heat exchange. The first heat exchanger 8 and the second heat exchanger 10 transfer and store the heat released during the gas compression process in the heat storage tank 7, and this heat is used for gas heating during the expansion process. By providing the energy storage device, the compressed heat is utilized, and the cold storage tank 9 stores the low-temperature heat transfer working medium after heat exchange, enabling the heat transfer working medium to be recycled, thus avoiding energy waste, improving the energy utilization efficiency, and greatly reducing the cost of compressed air energy storage.

[0054] Further, as Figure 1As shown, a preheating heat exchange device is further provided at the inlet end of the pressure regulating device 4, and the preheating heat exchange device is connected to the high-temperature heat storage unit and the low-temperature heat storage unit. Specifically, the preheating heat exchange device includes a preheating heat exchanger 15. The preheating heat exchanger 15 adopts a direct contact heat exchanger, such as a gas condenser, where the hot and cold fluids directly contact for heat exchange. The preheating heat exchanger 15 uses the heat stored in the heat storage tank 7 during the process of using compressed air to preheat the compressed air coming out of the gas storage tank, improving the energy utilization rate.

[0055] Furthermore, as Figure 1 shown, the expansion device includes at least two stages of expanders connected in series. A reflux bypass 12 is provided in any stage or each stage of the expander. A third heat exchanger 11 is provided between adjacent two stages of expanders, and the third heat exchanger 11 is connected to the high-temperature heat storage unit and the low-temperature heat storage unit.

[0056] Specifically, in this embodiment, the expansion device includes a first-stage expander 5 and a second-stage expander 6 connected in series. The third heat exchanger 11 is provided between the first-stage expander 5 and the second-stage expander 6. A reflux bypass 12 is provided between the first-stage expander 5 and the second-stage expander 6 and the pressure regulating device 4. By setting the expander inter-stage reflux bypass 12, the work flow rate of the high-pressure stage expander is increased, the system expansion compressed air flow rate and the low-pressure stage expander flow rate are reduced, and the volume of the low-pressure stage expander and the system cost are lowered.

[0057] Furthermore, as Figure 1 shown, a bypass regulating valve 13 and a flowmeter 17 are provided on the reflux bypass 12, and the bypass regulating valve 13 and the flowmeter 17 are connected to the controller 16.

[0058] Specifically, the controller 16 is connected to the pressure regulating motor 404, the pressure regulating generator 406, the bypass regulating valve 13, and the flowmeter 17. The flowmeter 17 measures the air flow rate in the return bypass 12 and feeds it back to the controller 16. The controller 16 adjusts the flow rate of the return bypass 12 by controlling the bypass regulating valve 13, thereby regulating the inter-stage return air pressure of the expansion device. The pressure regulating device 4 controls the outlet pressure through the controller 16. The controller detects the control target value of the pressure regulating device 4 to automatically adjust the operating condition of the pressure regulating device 4 based on the control target value. The control target value is the target outlet pressure, the operating outlet pressure, and the inter-stage return air pressure of the pressure regulating device 4. Among them, the target outlet pressure is 7-8 MPa. Adjusting the operating condition of the pressure regulating device 4 is as follows: when the work done by the pressure regulating expander 401 is greater than that of the pressure regulating compressor 402, the controller 16 disconnects the first coupling 405 on the side of the pressure regulating motor 404, and the pressure regulating device 4 generates electricity externally through the pressure regulating motor 404; when the work done by the pressure regulating expander 401 is less than that of the pressure regulating compressor 402, the controller 16 disconnects the second coupling 407 on the side of the pressure regulating generator 406, and the pressure regulating device 4 draws power from the power grid to drive the pressure regulating compressor 402 to do work, realizing the automatic adjustment of the outlet pressure value, reducing the resource waste caused by excessive pressure value, improving the control accuracy at the same time, and improving the pressure stability of the output compressed air.

[0059] Embodiment 2

[0060] This embodiment discloses a compressed air energy storage method, which includes the following steps:

[0061] S1. The atmospheric air is compressed by the compression device to become high-temperature and high-pressure air, and then exchanges heat with the heat exchange working medium through the first heat exchanger 8, becomes high-pressure and low-temperature compressed air, and then enters the gas storage device 3 for storage; S2. The high-pressure and low-temperature compressed air obtained in S1 flows out of the gas storage device 3, is heated by the preheating heat exchange device of the compressed air energy storage system, and then enters the pressure regulating device 4; S3. The compressed air is depressurized and expanded by the pressure regulating expander 401 of the pressure regulating device 4, and the final pressure is 100 kPa lower than the inter-stage reflux air pressure; S4. The bypass regulating valve 13 is opened, and the compressed air in the reflux bypass 12 is mixed with the compressed air at the outlet of the pressure regulating expander 401 and enters the pressure regulating compressor 402; S5. The power of the pressure regulating compressor 402 is adjusted to make the outlet pressure of the pressure regulating device 4 reach the control target value, and the power of the pressure regulating compressor 402 is compared with the power of the pressure regulating expander 401; S6. When the power of the pressure regulating expander 401 is greater than the power of the pressure regulating compressor 402, the first coupling 405 on one side of the pressure regulating motor 404 is disconnected, and the pressure regulating device 4 generates electricity externally through the pressure regulating generator 406; otherwise, the second coupling 407 on one side of the pressure regulating generator 406 is disconnected, and the pressure regulating device 4 draws power from the power grid to drive the pressure regulating compressor 402 to do work; S7. The compressed air flowing out of the pressure regulating device 4 is heated and then enters the expansion device to do work and generate electricity.

[0062] Specifically, during energy storage, the atmospheric air is compressed by the compressor 2 driven by the motor 1, and after compression, it is transformed into high-temperature and high-pressure air. Then, it exchanges heat with the heat exchange working medium through the first heat exchanger 8, transforms the high-temperature and high-pressure air into high-pressure and low-temperature compressed air and stores it in the gas storage tank, and at the same time, the released heat is stored in the heat storage tank 7.

[0063] During power generation, according to the pressure required at the inlet of the first-stage expander 5, the high-pressure and low-temperature compressed air is heated by the preheating heat exchanger 15, and then enters the pressure-regulating expander 401 of the pressure-regulating device 4 for pressure reduction and expansion. The final pressure is lower than the inter-stage reflux pressure of 100 kPa. The bypass regulating valve 13 is opened, so that the compressed air after pressure reduction and expansion, that is, the compressed air at the outlet of the pressure-regulating expander 401, is mixed with the compressed air flowing back to the pressure-regulating device 4 in the reflux bypass 12 through the compressed air mixer 408, and enters the pressure-regulating compressor 402 to be pressurized to the inlet pressure of the first-stage expander 5. Then, the compressed air passing through the pressure-regulating device 4 is heated by the second heat exchanger 10, and then enters the first-stage expander 5 to do work and generate electricity. The compressed air at the outlet of the first-stage expander 5 enters the third heat exchanger 11 for heating and then enters the second-stage expander 6 to do work and generate electricity, and finally is discharged to the atmosphere. The controller detects the target outlet pressure, the operating outlet pressure of the pressure-regulating device 4, and the reflux air pressure in the reflux bypass 12, and automatically adjusts the operating conditions of the pressure-regulating device 4 to switch the operating conditions: when the work done by the pressure-regulating expander 401 is greater than that of the pressure-regulating compressor 402, the first coupling 405 on one side of the pressure-regulating motor 404 is disconnected, and the pressure-regulating device 4 generates electricity externally through the pressure-regulating generator 406; when the work done by the pressure-regulating expander 401 is less than that of the pressure-regulating compressor 402, the second coupling 407 on one side of the pressure-regulating generator 406 is disconnected, and power is taken from the power grid to drive the pressure-regulating compressor 402 to do work, realizing the automatic adjustment of the outlet pressure value, reducing the waste of resources caused by too high pressure value, improving the control accuracy at the same time, and improving the pressure stability of the output compressed air.

[0064] Before optimization, the gas flowing into the second-stage expander 6 is the exhausted gas flowing out of the first-stage expander 5, and the work done by the expander is extremely low. In the compressed air energy storage method of this embodiment, by using the pressure-regulating device 4 to replace the throttle valve, and at the same time setting up a multi-stage expander inter-stage reflux bypass 12, high-pressure air is mixed with the exhausted gas with lower pressure that has done work, reducing the inlet pressure of the first-stage expander 5, greatly increasing the work done and power generation of the second-stage expander 6, avoiding the throttling loss brought by the throttle valve in the traditional technology, and improving the efficiency of the compressed air energy storage system.

[0065] Obviously, the above embodiments are only examples clearly described and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A compressed air energy storage system, characterized in that, Comprising: An air energy storage unit, including an air storage device (3), and the air storage device (3) is provided with an air storage outlet; A pressure regulating device (4), having an inlet end, an outlet end, and a reflux end, and the inlet end is connected to the air storage outlet; An expansion device, having an expansion inlet and an expansion reflux port, and the expansion inlet is connected to the outlet end of the pressure regulating device (4); A reflux bypass (12), one end of the reflux bypass (12) is connected to the expansion reflux port, and the other end is connected to the reflux end; A controller (16), the controller (16) is connected to the pressure regulating device (4), and the controller (16) is configured to detect a control target value of the pressure regulating device (4) to automatically adjust an operating condition of the pressure regulating device (4) based on the control target value; The pressure regulating device (4) includes a pressure regulating expander (401), a pressure regulating compressor (402), a pressure regulating motor (404), and a pressure regulating generator (406); The pressure regulating expander (401) and the pressure regulating compressor (402) are shaft-connected through a gearbox (403), the pressure regulating motor (404) and the pressure regulating compressor (402) are connected through a first coupling (405), the pressure regulating generator (406) and the pressure regulating expander (401) are connected through a second coupling (407), and the pressure regulating motor (404) and the pressure regulating generator (406) are respectively connected to the controller.

2. The compressed air energy storage system according to claim 1, wherein The control target value includes a target outlet end pressure, an operating outlet end pressure of the pressure regulating device (4), and a reflux air pressure in the reflux bypass (12).

3. The compressed air energy storage system according to claim 1, characterized in that, The compressed air energy storage system further includes an energy storage device, and the energy storage device includes a high-temperature heat storage unit and a low-temperature heat storage unit that exchange heat through the circulation of a heat transfer working medium and store heat; The high-temperature heat storage unit is used to exchange heat of high-temperature and high-pressure compressed air into high-pressure and low-temperature air and store the heat, and the low-temperature heat storage unit is used to store the low-temperature heat transfer working medium after heat exchange of the heat transfer working medium.

4. The compressed air energy storage system according to claim 3, wherein, It further includes a compression device, and a first heat exchanger (8) is provided between the compression device and the air storage device (3), the first heat exchanger (8) is connected to the high-temperature heat storage unit, and the high-pressure and high-temperature compressed air is stored in the air storage device (3) after heat exchange through the first heat exchanger (8), and at the same time, the released heat is stored in the high-temperature heat storage unit.

5. The compressed air energy storage system according to claim 3, wherein A second heat exchanger (10) is provided between the pressure regulating device (4) and the expansion device, the second heat exchanger (10) is connected to the high-temperature heat storage unit and the low-temperature heat storage unit, and the high-pressure and low-temperature air enters the expansion device after heat exchange through the second heat exchanger (10), and at the same time, the heat transfer working medium that releases heat returns to the low-temperature heat storage unit for storage.

6. The compressed air energy storage system according to claim 5, wherein A preheating heat exchange device is further provided at the inlet end of the pressure regulating device (4), and the preheating heat exchange device is connected to the high-temperature heat storage unit and the low-temperature heat storage unit.

7. The compressed air energy storage system according to claim 5, wherein The expansion device includes at least two stages of expanders connected in series, and a reflux bypass (12) is provided in any stage or each stage of the expander. A third heat exchanger (11) is provided between two adjacent stages of the expander, and the third heat exchanger (11) is connected to the high-temperature heat storage unit and the low-temperature heat storage unit.

8. The compressed air energy storage system according to claim 7, wherein, A bypass regulating valve (13) and a flowmeter (17) are provided on the reflux bypass (12), and the bypass regulating valve (13) and the flowmeter (17) are connected to the controller (16).

9. A method for energy storage in a compressed air energy storage system, applicable to the compressed air energy storage system according to any one of claims 1-8, characterized in that, It includes the following steps: S1. Energy storage state: Atmospheric air is compressed by a compression device to become high-temperature and high-pressure air, and then exchanges heat with a heat transfer medium through a first heat exchanger (8) to become high-pressure and low-temperature compressed air, which then enters a gas storage device (3) for storage. S2. Energy release state: The high-pressure and low-temperature compressed air obtained in S1 flows out of the gas storage device (3), is heated by a preheating heat exchange device of the compressed air energy storage system, and then enters a pressure regulating device (4). S3. The compressed air undergoes pressure-reducing expansion through a pressure regulating expander (401) of the pressure regulating device (4), and the final pressure is 100 kPa lower than the inter-stage reflux air pressure. S4. Open the bypass regulating valve (13), and the compressed air in the reflux bypass (12) is mixed with the compressed air at the outlet of the pressure regulating expander (401) and enters a pressure regulating compressor (402). S5. Adjust the power of the pressure regulating compressor (402) to make the outlet pressure of the pressure regulating device (4) reach the control target value, and compare the power of the pressure regulating compressor (402) with the power of the pressure regulating expander (401). S6. When the power of the pressure regulating expander (401) is greater than the power of the pressure regulating compressor (402), disconnect the first coupling (405) on the side of the pressure regulating motor (404), and the pressure regulating device (4) generates electricity externally through a pressure regulating generator (406); otherwise, disconnect the second coupling (407) on the side of the pressure regulating generator (406), and the pressure regulating device (4) draws power from the power grid to drive the pressure regulating compressor (402) to do work. S7. The compressed air flowing out of the pressure regulating device (4) is heated and then enters the expansion device to do work and generate electricity.

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