Pressure stabilizing device and method for liquid air energy storage system and liquid air energy storage system

Abstract

The invention relates to a pressure stabilizing device and method for a liquid air energy storage system and the liquid air energy storage system. A discharging pressure stabilizing loop is used for conveying part of low-pressure liquid air in a liquid air storage tank to a cold storage heat exchange unit for gasification under the discharging working condition, and obtained gaseous air flows back to the liquid air storage tank; the ultra-cold energy recycled in the gasification process can be used for further cooling high-pressure cryogenic ambient air under the charging working condition, the cold energy recycling efficiency is improved, energy loss is reduced, the charging and discharging efficiency of the system is improved, and the system is suitable for large-scale energy storage and cold energy utilization scenes. The economic value is relatively high.

Description

Technical Field

[0001] The present disclosure relates to a voltage stabilizing device, a method and a liquid air energy storage system for a liquid air energy storage system. Background Art

[0002] Liquid Air Energy Storage (LAES) is a new type of energy storage method. Its working principle is to use low-cost off-peak electricity to compress, cool and expand ambient air to liquid air at normal or low pressure for storage; during peak electricity consumption, the liquid air is then boosted in pressure and heated to be re-vaporized and expanded to drive an expander to generate electricity, thereby realizing peak shaving and valley filling of electricity and playing an important role in power grid peak regulation.

[0003] However, during the discharging operation, during the process of liquid air being released from the storage tank and vaporized, especially when using low-pressure state to store liquid air, the pressure inside the tank will constantly change, and the operating parameters of the charge-discharge system equipment will also change accordingly, ultimately resulting in a reduction in charge-discharge efficiency, and even equipment shutdown and safety accidents. Therefore, how to achieve stable pressure control during the discharging operation to improve the overall energy efficiency of the system operation is one of the important challenges in the application of liquid air energy storage technology. Summary of the Invention

[0004] The purpose of the present disclosure is to provide a voltage stabilizing device, a method and a liquid air energy storage system for a liquid air energy storage system to achieve pressure stability of the liquid air storage tank during the discharging operation and improve the charge-discharge efficiency of the liquid air energy storage system.

[0005] To achieve the above purpose, in the first aspect of the present disclosure, a voltage stabilizing device for a liquid air energy storage system is provided. The device includes a cold storage and heat exchange unit and a liquid air storage tank; wherein, the liquid air storage tank is used to store low-pressure liquid air, and the cold storage and heat exchange unit is used to store the supercooling energy of the low-pressure liquid air from the liquid air storage tank during the discharging operation and use the supercooling energy to cool the high-pressure cryogenic ambient air during the charging operation. The voltage stabilizing device further includes a discharging voltage stabilizing loop, configured to, during the discharging operation, transport a part of the low-pressure liquid air in the liquid air storage tank to the cold storage and heat exchange unit for gasification and make the obtained gaseous air flow back to the liquid air storage tank.

[0006] Optionally, the cold storage and heat exchange unit has a high-temperature end and a low-temperature end. The high-temperature end of the cold storage and heat exchange unit is used to receive the high-pressure cryogenic ambient air, and the low-temperature end of the cold storage and heat exchange unit is connected to the liquid air storage tank through a low-temperature expander; The liquid air storage tank has a discharge reflux air output port and a discharge reflux air return port. The discharge reflux air output port is connected to the low-temperature end of the cold storage heat exchange unit through a cryogenic pump, and the discharge reflux air return port is connected to the high-temperature end of the cold storage heat exchange unit through a check valve.

[0007] Optionally, the discharge voltage stabilizing circuit is configured to, in response to the pressure signal in the liquid air storage tank, start the cryogenic pump when the pressure in the liquid air storage tank is lower than a first preset value, and close the cryogenic pump when the pressure in the liquid air storage tank is higher than a second preset value.

[0008] Optionally, the cold storage heat exchange unit includes a cold storage heat exchanger; Optionally, the cold storage heat exchanger is filled with a cold storage medium, and the material of the cold storage medium includes at least one of graphite, steel slag, basalt, brine, water, and organic solvents.

[0009] Optionally, the cold storage heat exchange unit includes a heat exchanger and a cold storage tank; Optionally, the heat exchange medium of the heat exchanger includes at least one of nitrogen, air, helium, brine, water, and organic solvents.

[0010] In a second aspect of the present disclosure, a voltage stabilizing method for a liquid air energy storage system is provided. The method includes: Under a discharge condition, part of the low-pressure liquid air in the liquid air storage tank is led out for gasification, and the obtained gaseous air is refluxed to the liquid air storage tank; Wherein, the ultra-low temperature energy generated by the gasification is recovered and used to cool the high-pressure cryogenic ambient air under a charging condition.

[0011] Optionally, the method further includes: Under a charging condition, the high-pressure cryogenic ambient air is cooled by using the ultra-low temperature energy to obtain cooled air; The cooled air is expanded and depressurized to obtain low-pressure liquid air; The low-pressure liquid air is stored in the liquid air storage tank.

[0012] Optionally, the pressure of the high-pressure cryogenic ambient air is greater than 3.8 MPa, and the temperature is -160°C to -138°C; The pressure of the cooled air is greater than 3.8 MPa, and the temperature is -166°C to -146°C; The pressure of the low-pressure liquid air is 1.0 - 3.8 MPa, and the temperature is -168°C to -141°C.

[0013] Optionally, the method further includes: Obtain the pressure signal inside the liquid air storage tank. When the pressure inside the liquid air storage tank is lower than the first preset value, start the extraction of low-pressure liquid air and the reflux of gaseous air. And when the pressure inside the liquid air storage tank is higher than the second preset value, stop the extraction of low-pressure liquid air and the reflux of gaseous air.

[0014] In the third aspect of the present disclosure, a liquid air energy storage system is provided, and this system includes the voltage stabilizing device described in the first aspect of the present disclosure.

[0015] Through the above technical solution, in the discharging condition, a part of the low-pressure liquid air in the liquid air storage tank is transported to the cold storage heat exchange unit for gasification by using the discharging voltage stabilizing loop, and the obtained gaseous air is refluxed to the liquid air storage tank cold storage heat exchange unit to achieve stable low pressure inside the liquid air storage tank. The ultra-low temperature energy recovered during the gasification process can be used to cool the high-pressure cryogenic ambient air during the charging condition, which is beneficial to improving the cold energy recovery efficiency, reducing energy loss, enhancing the charge and discharge efficiency of the system, being applicable to large-scale energy storage and cold energy utilization scenarios, and having high economic value.

[0016] Other features and advantages of the present disclosure will be described in detail in the subsequent specific implementation part. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings are used to provide a further understanding of the present disclosure, and constitute a part of the specification. Together with the following specific implementation, they are used to explain the present disclosure, but do not constitute a limitation to the present disclosure. In the drawings: Figure 1 is a schematic structural diagram of a liquid air energy storage system according to a specific implementation provided by the present disclosure; Figure 2 is Figure 1 a schematic diagram of the process logistics flow route of the liquid air energy storage system under the charging condition; Figure 3 is Figure 1 a schematic diagram of the process logistics flow route of the liquid air energy storage system under the discharging condition; Figure 4 is a schematic structural diagram of another liquid air energy storage system according to a specific implementation provided by the present disclosure; Figure 5 is Figure 4 a schematic diagram of the process logistics flow route of the liquid air energy storage system under the charging condition; Figure 6 is Figure 4 a schematic diagram of the process logistics flow route of the liquid air energy storage system under the discharging condition; Figure 7 is a schematic structural diagram of yet another liquid air energy storage system according to a specific implementation provided by the present disclosure; Figure 8 is Figure 7 a schematic diagram of the process fluid flow route of the liquid air energy storage system under the charging condition; Figure 9 is Figure 7 a schematic diagram of the process fluid flow route of the liquid air energy storage system under the discharging condition.

[0018] Description of the reference numerals A—voltage stabilizing device, 1—liquid air storage tank, 2—cold storage heat exchanger, 3—third heat exchanger, 4—fourth heat exchanger, 5—fifth heat exchanger, 6—sixth heat exchanger, 7—seventh heat exchanger, 8—eighth heat exchanger, 9—ninth heat exchanger, 10—first compressor, 11—second compressor, 12—low-temperature expander, 13—second expander, 14—third expander, 15—second check valve, 16—first check valve, 17—second cryogenic pump, 18—third cryogenic pump, 19—first cryogenic pump, 20—charging pressure control valve, 21—first heat exchanger, 22—second heat exchanger; 23—third compressor, 24—fourth compressor, 25—fifth compressor, 26—sixth compressor, 27—fourth expander, 28—fifth expander, 29—sixth expander, 30—seventh expander, 31—tenth heat exchanger, 32—eleventh heat exchanger, 33—twelfth heat exchanger, 34—thirteenth heat exchanger, 35—fourteenth heat exchanger, 36—fifteenth heat exchanger, 37—sixteenth heat exchanger, 38—seventeenth heat exchanger, 39—eighteenth heat exchanger, 40—nineteenth heat exchanger, 41—charging reflux heat exchanger, 42—air purifier; D1—second heat storage tank, D2—second cold storage tank, D3—third heat storage tank, D4—third cold storage tank, D5—first heat storage tank, D6—first cold storage tank, D7—seventh heat storage tank, D8—seventh cold storage tank, D9—eighth heat storage tank, D10—eighth cold storage tank, D11—fourth heat storage tank, D12—fourth cold storage tank, D13—fifth heat storage tank, D14—fifth cold storage tank, D15—sixth heat storage tank, D16—sixth cold storage tank. Detailed implementation manners

[0019] The following further elaborates on the detailed implementation manners of the present disclosure with reference to the accompanying drawings. It should be understood that the detailed implementation manners described herein are only for the purpose of illustration and explanation of the present disclosure, and are not intended to limit the present disclosure.

[0020] In the first aspect of the present disclosure, a voltage stabilizing device for a liquid air energy storage system is provided. Refer to Figures 1 - 9, the voltage stabilizing device A includes a cold storage and heat exchange unit and a liquid air storage tank 1; wherein, the liquid air storage tank 1 is used to store low-pressure liquid air, and the cold storage and heat exchange unit is used to recover the supercooling energy of the low-pressure liquid air from the liquid air storage tank 1 under the discharging condition, and use the supercooling energy to cool the high-pressure cryogenic ambient air under the charging condition; the voltage stabilizing device further includes a discharging voltage stabilizing circuit, which is configured to convey a part of the low-pressure liquid air in the liquid air storage tank 1 to the cold storage and heat exchange unit for gasification under the discharging condition, and return the obtained gaseous air to the liquid air storage tank 1.

[0021] In the present disclosure, the charging condition refers to the operation mode of the system during the energy storage stage, which generally may include air compression, precooling, deep cooling and liquefaction, and liquid air storage links, converting electrical energy into cryogenic cold energy and storing it for subsequent use in the discharging condition. The discharging condition refers to the operation mode of the system during the energy release stage, which generally may include liquid air extraction and pressurization, preheating and gasification, cold energy recovery, and expansion power generation links, converting cryogenic cold energy into electrical energy and / or mechanical energy for reuse. The high-pressure cryogenic ambient air refers to the ambient air that is higher than the critical pressure of air after compression and cooling under the charging condition, and is high-pressure and close to or lower than the air liquefaction temperature under the high pressure. The low-pressure liquid air refers to the air that is lower than or close to the critical pressure of air and remains in a liquid state; in the present disclosure, the pressure of the high-pressure cryogenic ambient air may be greater than 3.8 MPa, and the temperature may be -160°C to -138°C; the pressure of the low-pressure liquid air may be 1.0 - 3.8 MPa, and the temperature may be -168°C to -141°C.

[0022] According to the present disclosure, the cold storage and heat exchange unit can store and transfer the supercooling energy under the charging and discharging conditions, and realize the stable low pressure of the liquid air storage tank 1 under the discharging condition by constructing a discharging voltage stabilizing circuit with the liquid air storage tank 1. Specifically, under the discharging condition, as the low-pressure liquid air in the liquid air storage tank 1 is drawn out, the gas phase space in the tank increases and the pressure in the tank gradually decreases. At this time, a part of the low-pressure liquid air in the liquid air storage tank 1 is led to the cold storage and heat exchange unit for gasification. After the low-pressure liquid air is converted into gaseous air, it returns to the liquid air storage tank 1, thereby increasing the amount of gaseous air in the liquid air storage tank 1 and restoring the pressure in the tank to the set low pressure, avoiding the risks caused by pressure changes. During this stage, the cold storage and heat exchange unit can absorb the supercooling energy of the low-pressure liquid air and store this part of the cold quantity. Then, under the charging condition, the cold storage and heat exchange unit can be used as a cold energy carrier to further cool the high-pressure cryogenic ambient air, thereby realizing the recovery and utilization of cold energy and optimizing the charging and discharging efficiency of the system.

[0023] In a specific embodiment, the cold storage heat exchange unit may have opposite high-temperature and low-temperature ends. Among them, the high-temperature end of the cold storage heat exchange unit is used to receive the high-pressure cryogenic ambient air, and the low-temperature end of the cold storage heat exchange unit is connected to the liquid air storage tank 1 and is used to transport the cooled air to the liquid air storage tank 1. Further, the low-temperature end of the cold storage heat exchange unit may be connected to the liquid air storage tank 1 through a low-temperature expander 12, and the low-temperature expander 12 is used to further cool the high-pressure cryogenic air using ultra-cold energy and then reduce the pressure to achieve low-pressure storage of liquid air.

[0024] Further, the liquid air storage tank 1 may have a liquid air input port, a discharge return air (RA-D) output port, and a discharge return air return port; among them, the liquid air input port of the liquid air storage tank 1 is connected to the low-temperature end of the cold storage heat exchange unit and is used to receive liquid air from the cold storage heat exchange unit under the charging condition; the discharge return air output port of the liquid air storage tank 1 is connected to the low-temperature end of the cold storage heat exchange unit and is used to transport the low-pressure liquid air stored in the liquid air storage tank 1 to the cold storage heat exchange unit for gasification; the discharge return air return port of the liquid air storage tank 1 is connected to the high-temperature end of the cold storage heat exchange unit and is used to receive the gasified gaseous air.

[0025] Further, a first low-temperature pump 19 may be provided on the pipeline between the discharge return air output port of the liquid air storage tank 1 and the low-temperature end of the cold storage heat exchange unit to provide the return power; a first one-way valve 16 may be provided between the discharge return air return port of the liquid air storage tank 1 and the high-temperature end of the cold storage heat exchange unit to ensure the one-way flow of the return air. In addition, a second one-way valve 15 may also be provided on the pipeline between the low-temperature end of the cold storage heat exchange unit and the liquid air input port of the liquid air storage tank 1 to prevent the reverse flow of liquid air, ensure that the air flow direction meets the working condition requirements, improve the reliability and safety of the system operation, and the second one-way valve 15 may be provided between the low-temperature expander 12 and the liquid air storage tank 1.

[0026] In the above embodiment, the discharge voltage stabilizing circuit can be further configured to, under the discharge condition, in response to the pressure signal in the liquid air storage tank 1, when the pressure in the liquid air storage tank 1 is lower than the first preset value, start the first cryogenic pump 19 to convey a part of the low-pressure liquid air to the cold storage and heat exchange unit, and the gasified air flows back and is injected into the liquefied air storage tank 1 through the opened first one-way valve 16; and when the pressure in the liquid air storage tank 1 is higher than the second preset value, turn off the first cryogenic pump 19, and the gas phase space in the liquefied air storage tank 1 will continuously decrease as the liquid air flows out, so as to ensure the pressure stability of the liquid air storage tank 1 under the discharge condition. Among them, the first preset value and the second preset value can be adjusted according to actual process requirements respectively. For example, the first preset value can be 1.6 MPa or 1.75 MPa, and the second preset value can be 1.8 MPa or 1.95 MPa. At this time, a pressure detection element (such as a pressure sensor) can be correspondingly provided in the liquid air storage tank 1 to monitor the gas phase pressure in the tank in real time and generate a pressure signal.

[0027] Preferably, the first one-way valve 16 can be a one-way flow regulating valve group or a functional valve combined with a flow regulating valve, and more precise pressure regulation can be achieved through stepless regulation of the reflux air flow. For example, when the pressure in the liquid air storage tank 1 is lower than the first preset value, start the first cryogenic pump 19, and adjust the pump speed and the opening degree of the first one-way valve 16 according to the deviation between the measured pressure and the first preset value, and control the flow rate of the low-pressure liquid air entering the cold storage and heat exchange unit to make the reflux rate match the tank pressure recovery rate; when the tank pressure recovers to between the first preset value and the second preset value, maintain partial reflux, gradually adjust the reflux amount through the first one-way valve 16 to keep the pressure within a stable range, and appropriately reduce the rotation speed of the first cryogenic pump 19 to avoid excessive reflux causing the pressure to rise too fast; when the tank pressure is higher than the second preset value, the reflux amount can be gradually reduced to make the tank pressure naturally decrease to a stable value. If the tank pressure still continues to rise, the reflux is completely stopped. Through the above embodiment, continuous adjustment of the reflux air flow can be achieved under the discharge condition, making the pressure in the liquid air storage tank 1 more stable, avoiding pressure fluctuations caused by frequent start and stop, and at the same time being more in line with the gasification requirements of liquid air, which is beneficial to improving the charge and discharge efficiency and the cold energy recovery effect. In addition, the liquid air reflux amount can be adjusted on demand according to external load requirements (such as grid fluctuations, power generation requirements, etc.), enabling the system to adapt to different operating modes and improving the overall flexibility.

[0028] The cold storage and heat exchange unit can be a device capable of realizing the cold storage and heat exchange functions described above. In a specific embodiment, refer to Figures 1 - 3, the cold storage heat exchange unit includes a cold storage heat exchanger 2. The cold storage heat exchanger 2 is filled with a cold storage medium, which can be used for heat exchange with the process stream (air in this disclosure) and can also store or release the cold energy from the heat exchange. Further, the material of the cold storage medium can include at least one of graphite, steel slag, basalt, brine, water, and organic solvents (such as propane). The above materials are beneficial to realizing the efficient storage and release of cold energy and reducing cold energy loss. Under the charging or discharging conditions, the temperature distribution of the cold storage medium can show a gradually changing gradient with the progress of the heat exchange process, so that the cold storage heat exchanger 2 naturally forms a high-temperature end and a low-temperature end. The high-temperature end of the cold storage heat exchanger 2 is used to receive the high-pressure cryogenic ambient air and is connected to the discharge return air port of the liquid air storage tank 1. The low-temperature end of the cold storage heat exchanger 2 is respectively connected to the liquid air input port and the discharge return air output port of the liquid air storage tank 1. The present disclosure has no special restrictions on the specific form of the cold storage heat exchanger 2. For example, it can be a packed bed, etc.

[0029] In another embodiment, the cold storage heat exchange unit includes a heat exchanger and a cold storage tank. Among them, the heat exchanger is a device that adjusts the temperature of the process stream by heat exchange with a heat exchange medium having a different temperature from the process stream. Specifically, the heat exchange medium of the heat exchanger can include at least one of nitrogen, air, helium, brine, water, and organic solvents (such as propane); the cold storage tank is used to store ultra-cold energy. By way of example, refer to Figures 4 - 6 , the cold storage heat exchange unit includes a first heat exchanger 21, a second heat exchanger 22, a first heat storage tank D5, and a first cold storage tank D6. Among them, the first heat exchanger 21 and the second heat exchanger 22 respectively have opposite high-temperature ends and low-temperature ends. The high-temperature ends of the first heat exchanger 21 and the second heat exchanger 22 are connected to the first heat storage tank D5, and the low-temperature ends of the first heat exchanger 21 and the second heat exchanger 22 are connected to the first cold storage tank D6. Further, the high-temperature end of the second heat exchanger 22 is used to receive the high-pressure cryogenic ambient air, the low-temperature end of the second heat exchanger 22 is connected to the input port of the low-temperature expander 12, and the outlet end of the low-temperature expander 12 is then connected to the liquid air input port of the liquid air storage tank 1. The high-temperature end of the first heat exchanger 21 is connected to the discharge return air port of the liquid air storage tank 1, and the low-temperature end of the first heat exchanger 21 is connected to the discharge return air output port of the liquid air storage tank 1. Under the discharging condition, the heat exchange medium in the first heat storage tank D5 enters the first heat exchanger 21 to exchange heat with the low-pressure liquid air from the liquid air storage tank 1, and the heat exchange medium carries the ultra-cold energy of the low-pressure liquid air into the first cold storage tank D6 for storage; under the charging condition, the heat exchange medium in the first cold storage tank D6 enters the second heat exchanger 22 to cool the high-pressure cryogenic ambient air, and the heat exchange medium enters the first heat storage tank D5 for storage after heating up.

[0030] In a second aspect of the present disclosure, there is provided a voltage stabilization method for a liquid air energy storage system implemented by the voltage stabilization device described in the first aspect of the present disclosure. The method includes: Under a discharging condition, a part of the low-pressure liquid air in the liquid air storage tank is led out for gasification, and the obtained gaseous air is returned to the liquid air storage tank; wherein, the ultra-low temperature energy generated by the gasification is recovered and used to cool the high-pressure cryogenic ambient air under a charging condition.

[0031] Wherein, the gasification of the low-pressure liquid air and the recovery of the ultra-low temperature energy are realized by the cold storage and heat exchange unit in the voltage stabilization device described in one aspect of the present disclosure, and the specific implementation manner refers to the foregoing description.

[0032] Further, the method may further include: Under a charging condition, the high-pressure cryogenic ambient air is cooled by using the ultra-low temperature energy to obtain the cooled air; wherein, the pressure of the high-pressure cryogenic ambient air may be greater than 3.8 MPa, and the temperature may be -160°C to -138°C; the pressure of the cooled air may be greater than 3.8 MPa, and the temperature may be -166°C to -146°C; The cooled air is expanded and depressurized to obtain low-pressure liquid air; wherein, the expansion and depressurization may be realized by a cryogenic expander 12; wherein, the pressure of the low-pressure liquid air may be 1.0 to 3.8 MPa, and the temperature may be -168°C to -141°C; The low-pressure liquid air is stored in the liquid air storage tank.

[0033] Further, the method may further include: under a discharging condition, obtaining a pressure signal in the liquid air storage tank, starting the extraction of the low-pressure liquid air and the return of the gaseous air when the pressure in the liquid air storage tank is lower than a first preset value, and stopping the extraction of the low-pressure liquid air and the return of the gaseous air when the pressure in the liquid air storage tank is higher than a second preset value. Wherein, the extraction of the low-pressure liquid air and the return of the gaseous air may be started or stopped by a first cryogenic pump 19, and the specific implementation manner refers to the foregoing description.

[0034] In a third aspect of the present disclosure, there is provided a liquid air energy storage system, which includes the voltage stabilization device described in the first aspect of the present disclosure. In addition, the system may further include other devices for liquid air energy storage, and the present disclosure has no special limitation on this.

[0035] In one implementation manner, referring to Figures 1 - 3, the system includes a voltage stabilizing device A, which includes a liquid air storage tank 1 and a cold storage heat exchanger 2. The cold storage heat exchanger 2 is a packed bed. In addition, the system also includes a charging heat exchange unit, a discharging heat exchange unit, and a supplementary cooling heat exchange unit. The charging heat exchange unit is connected to the high-temperature end of the cold storage heat exchanger 2, the discharging heat exchange unit is connected to the liquid air storage tank 1, and the supplementary cooling heat exchange unit is connected to an external cooling module. The cold source of the cooling module is liquefied natural gas.

[0036] Among them, the charging heat exchange unit includes a first compressor 10, a third heat exchanger 3, a fourth heat exchanger 4, a second compressor 11, and a fifth heat exchanger 5 connected in sequence along the entering direction of ambient air. The first compressor 10 has an ambient air input port, and the fifth heat exchanger 5 is connected to the high-temperature end of the cold storage heat exchanger 2. The discharging heat exchange unit includes a sixth heat exchanger 6, a seventh heat exchanger 7, a second expander 13, an eighth heat exchanger 8, and a third expander 14 connected in sequence along the air flow direction. The third expander 14 has a regasified air output port. The supplementary cooling heat exchange unit includes a ninth heat exchanger 9 arranged in parallel with the fourth heat exchanger 4, the fifth heat exchanger 5, and the sixth heat exchanger 6. The heat exchange media of the third heat exchanger 3, the seventh heat exchanger 7, and the eighth heat exchanger 8 share a second heat storage tank D1 and a second cold storage tank D2; the fourth heat exchanger 4, the fifth heat exchanger 5, the sixth heat exchanger 6, and the ninth heat exchanger 9 share a third heat storage tank D3 and a third cold storage tank D4.

[0037] The low-temperature end of the cold storage heat exchanger 2 is connected to the liquid air input port of the liquid air storage tank 1 through a low-temperature expander 12 and a second one-way valve 15. The discharging return air output port of the liquid air storage tank 1 is connected to the low-temperature end of the cold storage heat exchanger 2 through a first cryogenic pump 19. The high-temperature end of the cold storage heat exchanger 2 is connected to the discharging return air return port of the liquid air storage tank 1 through a first one-way valve 16 to form a discharging voltage stabilizing loop. The liquid air output port of the liquid air storage tank 1 is connected to the sixth heat exchanger 6 of the discharging heat exchange unit through a second cryogenic pump 17. LNG is connected to the seventh heat exchanger 9 through a third cryogenic pump 18. The charging return air output port of the liquid air storage tank 1 (which is the same port as the discharging return air return port) is connected to the air input port of the second compressor 11 through a charging pressure control valve 20.

[0038] Reference Figure 2, under the charging condition, ambient air (with a pressure of 0.1 MPa and a temperature ranging from -20°C to 40°C) enters the charging heat exchange unit for compression and cooling to obtain high-pressure cryogenic ambient air. LNG provides supplementary cold energy for the fourth heat exchanger 4, the fifth heat exchanger 5, and the sixth heat exchanger 6 through the seventh heat exchanger 9. The high-pressure cryogenic liquid air enters the cold storage heat exchanger 2 for further cooling and then enters the liquid air storage tank 1 for storage. When the internal pressure of the liquid air storage tank 1 exceeds the steady pressure upper limit threshold, the charging pressure control valve 20 opens, allowing the air in the gas phase space of the liquid air storage tank 1 to flow back as charging return air RA-C and merge into the low-pressure cryogenic air about to enter the second compressor 11, thereby reducing the internal pressure of the liquid air storage tank 1.

[0039] Reference Figure 3 , under the discharging condition, the low-pressure liquid air in the liquid air storage tank 1 enters the discharging heat exchange unit for heating up and expanding into regasified air (with a pressure of 1.5 - 2.0 MPa and a temperature ranging from -168°C to -140°C). When the internal pressure of the liquid air storage tank 1 is lower than the first preset value (such as 1.6 MPa), the first cryogenic pump 19 is started, and part of the low-pressure liquid air in the liquid air storage tank 1 is transported as discharging return air RA-D to the cold storage heat exchanger 2 for gasification. The gasified gaseous air flows back into the liquid air storage tank 1 through the first one-way valve 16. When the pressure in the liquid air storage tank 1 is higher than the second preset value (such as 1.8 MPa), the first cryogenic pump 19 is closed, and the pressure in the gas phase space of the liquid air storage tank 1 will continuously decrease as the liquid air flows out to the discharging heat exchange unit, thereby ensuring the pressure stability of the liquid air storage tank 1 under the discharging condition.

[0040] In another embodiment, reference Figures 4 - 6 , the system includes a pressure stabilizing device A, which includes a liquid air storage tank 1, a first heat exchanger 21, a second heat exchanger 22, a first heat storage tank D5, and a first cold storage tank D6. In addition, the system also includes a charging heat exchange unit, a discharging heat exchange unit, and a supplementary cold heat exchange unit that are the same as those in the first embodiment.

[0041] Among them, the low-temperature end of the second heat exchanger 22 is connected to the liquid air input port of the liquid air storage tank 1 through a low-temperature expander 12 and a second one-way valve 15. The discharging return air output port of the liquid air storage tank 1 is connected to the low-temperature end of the first heat exchanger 21 through the first cryogenic pump 19, and the high-temperature end of the first heat exchanger 21 is connected to the discharging return air return port of the liquid air storage tank 1 through the first one-way valve 16, forming a discharging pressure stabilizing loop.

[0042] Reference Figure 5, under the charging condition, ambient air enters the charging heat exchange unit for compression and cooling to obtain high-pressure cryogenic ambient air. The high-pressure cryogenic liquid air enters the second heat exchanger 22 for further cooling and then enters the low-temperature expander 12 for temperature reduction and pressure reduction, and finally enters the liquid air storage tank 1 for storage. Refer to Figure 6 , under the discharging condition, when the internal pressure of the liquid air storage tank 1 is lower than the first preset value (such as 1.6 MPa), the first low-temperature pump 19 is started, and part of the low-pressure liquid air in the liquid air storage tank 1 is transported as the discharging return air RA-D to the first heat exchanger 21 for gasification. The gasified air flows back into the liquid air storage tank 1 through the first one-way valve 16. When the pressure in the liquid air storage tank 1 is higher than the second preset value (such as 1.8 MPa), the first low-temperature pump 19 is closed, and the pressure in the gas phase space of the liquid air storage tank 1 will continuously decrease as the liquid air flows out to the discharging heat exchange unit, so as to ensure the pressure stability of the liquid air storage tank 1 under the discharging condition.

[0043] In another embodiment, refer to Figures 7 - 9 , the system includes a voltage stabilizing device A. The voltage stabilizing device A includes the same liquid air storage tank 1 and cold storage heat exchanger 2 as in the first embodiment. In addition, the system further includes a charging heat exchange unit and a discharging heat exchange unit. The charging heat exchange unit is connected to the high-temperature end of the cold storage heat exchanger 2, and the discharging heat exchange unit is connected to the liquid air storage tank 1. The charging heat exchange unit and the discharging heat exchange unit in this embodiment are different from the previous two embodiments, and there is no external cooling module.

[0044] Among them, the charging heat exchange unit includes a third compressor 23, a tenth heat exchanger 31, a fourth compressor 24, an eleventh heat exchanger 32, a fifth compressor 25, a twelfth heat exchanger 33, a sixth compressor 26, a thirteenth heat exchanger 34, and a fourteenth heat exchanger 35, which are connected in sequence along the entering direction of the ambient air. The first compressor 23 has an ambient air input port, and the fourteenth heat exchanger 35 is connected to the high-temperature end of the cold storage heat exchanger 2. In addition, an air purifier 42 is optionally connected between the eleventh heat exchanger 32 and the fifth compressor 25. The discharging heat exchange unit includes a nineteenth heat exchanger 40, an eighteenth heat exchanger 39, a fourth expander 27, a seventeenth heat exchanger 38, a fifth expander 28, a sixteenth heat exchanger 37, a sixth expander 29, a fifteenth heat exchanger 36, and a seventh expander 30, which are connected in sequence along the flowing direction of the air. The seventh expander 30 has a regasified air output port. The heat exchange media of the tenth heat exchanger 31 and the fifteenth heat exchanger 36 share the fourth heat storage tank D11 and the fourth cold storage tank D12; the heat exchange media of the eleventh heat exchanger 32 and the sixteenth heat exchanger 37 share the fifth heat storage tank D13 and the fifth cold storage tank D14; the heat exchange media of the twelfth heat exchanger 33 and the seventeenth heat exchanger 38 share the sixth heat storage tank D15 and the sixth cold storage tank D16; the heat exchange media of the thirteenth heat exchanger 34 and the eighteenth heat exchanger 39 share the seventh heat storage tank D7 and the seventh cold storage tank D8; the heat exchange media of the fourteenth heat exchanger 35 and the nineteenth heat exchanger 40 share the eighth heat storage tank D9 and the eighth cold storage tank D10. In addition, the charging heat exchange unit further includes a charging return heat exchanger 41 for exchanging heat with the charging return air RA-C under the charging condition to recover cold energy. The charging return heat exchanger 41 can be arranged in parallel with the thirteenth heat exchanger 34 and / or the fourteenth heat exchanger 35. Specifically, the charging return heat exchanger 41 has a charging return air input port, a charging return air output port, a heat exchange medium input port, and a heat exchange medium output port. The charging return air input port is connected to the charging return air output port of the liquid air storage tank 1 through a charging pressure control valve 20, the charging return air output port is connected to the air input port of the fifth compressor 25, the heat exchange medium input port is connected to the pipeline between the sixth compressor 26 and the high-temperature end of the thirteenth heat exchanger 34, and the heat exchange medium output port is connected to the high-temperature end of the ultra-cold cold storage heat exchanger 2.

[0045] Reference Figure 8, under the charging condition, ambient air enters the charging heat exchange unit for compression and cooling to obtain high-pressure cryogenic ambient air. The high-pressure cryogenic liquid air enters the cold storage heat exchanger 2 for further cooling and then enters the low-temperature expander 12 for cooling and pressure reduction, and finally enters the liquid air storage tank 1 for storage. When the internal pressure of the liquid air storage tank 1 exceeds the steady pressure upper limit threshold, the charging pressure control valve 20 opens, so that the air in the gas phase space of the liquid air storage tank 1 flows back as the charging return air RA-C. After heat exchange in the charging return heat exchanger 41, it flows back and merges into the low-pressure cryogenic air about to enter the fifth compressor 25, thereby reducing the internal pressure of the liquid air storage tank 1.

[0046] Reference Figure 9 , under the discharging condition, the low-pressure liquid air in the liquid air storage tank 1 enters the discharging heat exchange unit for heating and expands into regasified air. When the internal pressure of the liquid air storage tank 1 is lower than the first preset value (such as 1.6 MPa), the first low-temperature pump 19 is started, so that part of the low-pressure liquid air in the liquid air storage tank 1 is sent to the cold storage heat exchanger 2 as the discharging return air RA-D for gasification. The gasified air flows back into the liquid air storage tank 1 through the first one-way valve 16; when the pressure in the liquid air storage tank 1 is higher than the second preset value (such as 1.8 MPa), the first low-temperature pump 19 is closed, and the pressure in the liquid air storage tank 1 will continue to decrease as the liquid air flows out to the discharging heat exchange unit, thereby ensuring the pressure stability of the liquid air storage tank 1 under the discharging condition.

[0047] The present disclosure solves the key problems such as pressure fluctuation and limited energy efficiency in the liquid air storage tank under the discharging condition in the existing liquid air energy storage technology, effectively improves the charge-discharge efficiency of the system, provides an efficient, economical and reliable energy storage solution for the consumption of renewable energy and the peak shaving of the power grid, and has broad application prospects.

[0048] The preferred embodiments of the present disclosure have been described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0049] In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, they can be combined in any suitable manner without conflict. To avoid unnecessary repetition, the present disclosure will not separately describe various possible combination manners.

[0050] In addition, any combination can be made between various different embodiments of the present disclosure, as long as it does not violate the idea of the present disclosure, and it should also be regarded as the content disclosed by the present disclosure.

Claims

1. A voltage stabilizing device for a liquid air energy storage system, characterized in that, The device includes a cold storage heat exchange unit and a liquid air storage tank; wherein, the liquid air storage tank is used to store low-pressure liquid air, and the cold storage heat exchange unit is used to store the ultra-cold energy of the low-pressure liquid air from the liquid air storage tank under the discharging condition, and use the ultra-cold energy to cool the high-pressure cryogenic ambient air under the charging condition; The voltage stabilizing device further includes a discharging voltage stabilizing circuit, which is configured to convey a part of the low-pressure liquid air in the liquid air storage tank to the cold storage heat exchange unit for gasification under the discharging condition, and return the obtained gaseous air to the liquid air storage tank.

2. The voltage stabilizing device according to claim 1, wherein The cold storage heat exchange unit has a high-temperature end and a low-temperature end. The high-temperature end of the cold storage heat exchange unit is used to receive the high-pressure cryogenic ambient air, and the low-temperature end of the cold storage heat exchange unit is connected to the liquid air storage tank through a low-temperature expander; The liquid air storage tank has a discharging return air output port and a discharging return air return port. The discharging return air output port is connected to the low-temperature end of the cold storage heat exchange unit through a low-temperature pump, and the discharging return air return port is connected to the high-temperature end of the cold storage heat exchange unit through a one-way valve.

3. The voltage stabilizing device according to claim 2, characterized in that, The discharging voltage stabilizing circuit is configured to, in response to the pressure signal in the liquid air storage tank, start the low-temperature pump when the pressure in the liquid air storage tank is lower than a first preset value, and close the low-temperature pump when the pressure in the liquid air storage tank is higher than a second preset value.

4. The voltage stabilizing device according to claim 1, wherein, The cold storage heat exchange unit includes a cold storage heat exchanger; Optionally, the cold storage heat exchanger is filled with a cold storage medium, and the material of the cold storage medium includes at least one of graphite, steel slag, basalt, brine, water and organic solvents.

5. The voltage stabilizing device according to claim 1, characterized in that, The cold storage heat exchange unit includes a heat exchanger and a cold storage tank; Optionally, the heat exchange medium of the heat exchanger includes at least one of nitrogen, air, helium, brine, water and organic solvents.

6. A voltage stabilization method for a liquid air energy storage system, characterized in that, The method includes: Under the discharging condition, draw out a part of the low-pressure liquid air in the liquid air storage tank for gasification, and return the obtained gaseous air to the liquid air storage tank; Wherein, the ultra-cold energy generated by the gasification is recovered and used to cool the high-pressure cryogenic ambient air under the charging condition.

7. The method according to claim 6, wherein The method further includes: Under the charging condition, use the ultra-cold energy to cool the high-pressure cryogenic ambient air to obtain cooled air; Expand and depressurize the cooled air to obtain low-pressure liquid air; Store the low-pressure liquid air in the liquid air storage tank.

8. The method according to claim 7, wherein The pressure of the high-pressure cryogenic ambient air is greater than 3.8 MPa, and the temperature is -160°C to -138°C; The pressure of the cooled air is greater than 3.8 MPa, and the temperature is -166°C to -146°C; The pressure of the low-pressure liquid air is 1.0~3.8 MPa, and the temperature is -168°C to -141°C.

9. The method according to claim 6, wherein The method further includes: Obtain the pressure signal inside the liquid air storage tank. When the pressure inside the liquid air storage tank is lower than the first preset value, start the extraction of the low-pressure liquid air and the reflux of the gaseous air, and when the pressure inside the liquid air storage tank is higher than the second preset value, stop the extraction of the low-pressure liquid air and the reflux of the gaseous air.

10. A liquid air energy storage system, characterized in that, This system includes the voltage stabilizing device described in any one of claims 1 to 5.

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