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

Abstract

The present disclosure relates to a pressure stabilizing device and method for a liquid air energy storage system, and a liquid air energy storage system. The pressure stabilizing device comprises a liquid air storage tank, a cold storage and heat exchange unit, and a discharge pressure stabilization circuit. Under a discharging working condition, part of low‑pressure liquid air in the liquid air storage tank is delivered to the cold storage and heat exchange unit for gasification, and the resulting gaseous air is returned to the liquid air storage tank, so as to stabilize the pressure of the storage tank. Cryogenic cold energy released during the gasification is recovered and used for cooling high‑pressure cryogenic ambient air under a charging working condition. The solution achieves both pressure stabilization during discharging and cold energy reuse during charging.

Description

Voltage stabilizing device, method, and liquid air energy storage system for liquid air energy storage systems

[0001] This application claims priority to Chinese patent application No. CN202510469376.5, filed on April 14, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to a voltage stabilization device, method, and liquid air energy storage system for use in a liquid air energy storage system. Background Technology

[0003] Liquid air energy storage (LAES) is a novel energy storage method. Its working principle is to use low-cost off-peak electricity to compress, cool, and expand ambient air to atmospheric or low-pressure liquid air for storage. During peak electricity demand, the liquid air is pressurized and heated, causing it to re-vaporize and expand, driving an expander to generate electricity. This achieves peak shaving and valley filling of electricity, playing an important role in grid peak regulation.

[0004] However, during discharge, the pressure inside the tank constantly changes as liquid air is released and vaporized, especially when storing liquid air at low pressure. This alters the operating parameters of the charging and discharging system, ultimately leading to reduced charging and discharging efficiency and even equipment shutdowns and safety accidents. Therefore, achieving stable pressure control during discharge to improve the overall energy efficiency of the system is one of the key challenges in the application of liquid air energy storage technology. Summary of the Invention

[0005] The purpose of this disclosure is to provide a pressure stabilizing device, method, and liquid air energy storage system for use in liquid air energy storage systems, so as to achieve pressure stabilization of the liquid air storage tank under discharge conditions and improve the charging and discharging efficiency of the liquid air energy storage system.

[0006] To achieve the above objectives, the first aspect of this disclosure provides a voltage stabilizing device for a liquid air energy storage system, the device comprising 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, the cold storage and heat exchange unit is used to store ultra-cold energy from the low-pressure liquid air in the liquid air storage tank under discharge conditions, and to use the ultra-cold energy to cool high-pressure cryogenic ambient air under charging conditions;

[0007] The voltage stabilizing device further includes a discharge voltage stabilizing circuit, which is configured to, under the discharge condition, transport a portion of the low-pressure liquid air in the liquid air storage tank to the cold storage and heat exchange unit for vaporization, and cause the resulting gaseous air to flow back to the liquid air storage tank.

[0008] Optionally, 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 cryogenic expander.

[0009] 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 one-way valve.

[0010] Optionally, the discharge voltage regulation circuit is configured to, in response to a 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 shut down the cryogenic pump when the pressure in the liquid air storage tank is higher than a second preset value.

[0011] Optionally, the cold storage heat exchange unit includes a cold storage heat exchanger;

[0012] Optionally, the cold storage heat exchanger is filled with a cold storage medium, the material of which includes at least one of graphite, steel slag, basalt, brine, water, and organic solvent.

[0013] Optionally, the cold storage and heat exchange unit includes a heat exchanger and a cold storage tank;

[0014] Optionally, the heat exchange medium of the heat exchanger includes at least one of nitrogen, air, helium, brine, water, and organic solvent.

[0015] A second aspect of this disclosure provides a voltage stabilization method for a liquid air energy storage system, the method comprising:

[0016] Under discharge conditions, a portion of the low-pressure liquid air in the liquid air storage tank is drawn out and vaporized, and the resulting gaseous air is returned to the liquid air storage tank.

[0017] The ultracold energy generated by the vaporization is recovered and used to cool the high-pressure cryogenic ambient air during charging.

[0018] Optionally, the method further includes:

[0019] During charging, the ultra-cold energy is used to cool the high-pressure cryogenic ambient air to obtain cooled air.

[0020] The cooled air is expanded and depressurized to obtain low-pressure liquid air.

[0021] The low-pressure liquid air is stored in the liquid air storage tank.

[0022] 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;

[0023] The cooled air has a pressure greater than 3.8 MPa and a temperature of -166°C to -146°C.

[0024] The pressure of the low-pressure liquid air is 1.0~3.8MPa, and the temperature is -168℃ to -141℃.

[0025] Optionally, the method further includes:

[0026] The pressure signal inside the liquid air storage tank is acquired. When the pressure inside the liquid air storage tank is lower than a first preset value, the extraction of low-pressure liquid air and the return of gaseous air are initiated. When the pressure inside the liquid air storage tank is higher than a second preset value, the extraction of low-pressure liquid air and the return of gaseous air are stopped.

[0027] A third aspect of this disclosure provides a liquid air energy storage system, which includes the voltage stabilizing device described in the first aspect of this disclosure.

[0028] The above technical solution utilizes a discharge voltage stabilization circuit to transport a portion of the low-pressure liquid air in the liquid air storage tank to the cold storage and heat exchange unit for vaporization during discharge. The resulting gaseous air is then returned to the cold storage and heat exchange unit of the liquid air storage tank, achieving stable low pressure within the liquid air storage tank. The ultra-cold energy recovered during the vaporization process can be used to cool the high-pressure cryogenic ambient air during charging, which is beneficial for improving cold energy recovery efficiency, reducing energy loss, and enhancing the charging and discharging efficiency of the system. It is suitable for large-scale energy storage and cold energy utilization scenarios and has high economic value.

[0029] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0030] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0031] Figure 1 is a schematic diagram of the structure of a liquid air energy storage system according to a specific embodiment of the present disclosure;

[0032] Figure 2 is a schematic diagram of the process flow path of the liquid air energy storage system in Figure 1 under charging conditions.

[0033] Figure 3 is a schematic diagram of the process flow path of the liquid air energy storage system in Figure 1 under discharge conditions.

[0034] Figure 4 is a schematic diagram of the structure of a liquid air energy storage system according to another specific embodiment of the present disclosure;

[0035] Figure 5 is a schematic diagram of the process flow path of the liquid air energy storage system in Figure 4 under charging conditions.

[0036] Figure 6 is a schematic diagram of the process flow path of the liquid air energy storage system in Figure 4 under discharge conditions.

[0037] Figure 7 is a structural schematic diagram of a liquid air energy storage system according to another specific embodiment of the present disclosure;

[0038] Figure 8 is a schematic diagram of the process flow path of the liquid air energy storage system in Figure 7 under charging conditions.

[0039] Figure 9 is a schematic diagram of the process flow path of the liquid air energy storage system in Figure 7 under discharge conditions.

[0040] Explanation of reference numerals in the attached figures:

[0041] A—Pressure 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—Cryogenic 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 exchangers; 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;

[0042] D1—Second thermal storage tank, D2—Second cold storage tank, D3—Third thermal storage tank, D4—Third cold storage tank, D5—First thermal storage tank, D6—First cold storage tank, D7—Seventh thermal storage tank, D8—Seventh cold storage tank, D9—Eighth thermal storage tank, D10—Eighth cold storage tank, D11—Fourth thermal storage tank, D12—Fourth cold storage tank, D13—Fifth thermal storage tank, D14—Fifth cold storage tank, D15—Sixth thermal storage tank, D16—Sixth cold storage tank. Detailed Implementation

[0043] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0044] In a first aspect, this disclosure provides a voltage stabilizing device for a liquid air energy storage system. Referring to Figures 1-9, the voltage stabilizing device A includes a cold storage and heat exchange unit and a liquid air storage tank 1. The liquid air storage tank 1 stores low-pressure liquid air, and the cold storage and heat exchange unit recovers ultracold energy from the low-pressure liquid air in the liquid air storage tank 1 during discharge, and uses this ultracold energy to cool high-pressure cryogenic ambient air during charging. The voltage stabilizing device also includes a discharge voltage stabilizing circuit configured to, during discharge, transport a portion of the low-pressure liquid air in the liquid air storage tank 1 to the cold storage and heat exchange unit for vaporization, and return the resulting gaseous air to the liquid air storage tank 1.

[0045] In this disclosure, the charging condition refers to the system's operating mode during the energy storage phase, which typically includes air compression, precooling, deep cooling and liquefaction, and liquid air storage stages, converting electrical energy into low-temperature cold energy and storing it for use in subsequent discharge conditions. The discharge condition refers to the system's operating mode during the energy release phase, which typically includes liquid air extraction and pressurization, preheating and vaporization, cold energy recovery, and expansion power generation stages, converting low-temperature cold energy into electrical energy and / or mechanical energy for reuse. High-pressure cryogenic ambient air refers to ambient air that, after compression and cooling under the charging condition, is at a high pressure above the critical air pressure and close to or below the air liquefaction temperature at said high pressure. Low-pressure liquid air refers to air that is below or close to the critical air pressure and remains in a liquid state. In this disclosure, the pressure of the high-pressure cryogenic ambient air can be greater than 3.8 MPa, and the temperature can be from -160°C to -138°C; the pressure of the low-pressure liquid air can be from 1.0 to 3.8 MPa, and the temperature can be from -168°C to -141°C.

[0046] According to this disclosure, the cold storage and heat exchange unit can store and transfer ultra-cold energy under charging and discharging conditions, and achieve stable low pressure in the liquid air storage tank 1 under discharging conditions by constructing a discharge voltage stabilization circuit with the liquid air storage tank 1. Specifically, under discharging conditions, as the low-pressure liquid air in the liquid air storage tank 1 is drawn out, the gas phase space inside the tank increases, and the pressure inside the tank gradually decreases. At this time, part of the low-pressure liquid air in the liquid air storage tank 1 is drawn to the cold storage and heat exchange unit for vaporization. After the low-pressure liquid air is converted into gaseous air, it flows back to the liquid air storage tank 1, thereby increasing the amount of gaseous air in the liquid air storage tank 1, so that the pressure inside the tank is restored 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 ultra-cold energy of the low-pressure liquid air and store this part of the cold energy. Then, under charging conditions, the cold storage and heat exchange unit can act 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.

[0047] In one specific embodiment, the cold storage and heat exchange unit may have 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 1 to deliver the cooled air to the liquid air storage tank 1. Further, the low-temperature end of the cold storage and heat exchange unit can be connected to the liquid air storage tank 1 via a cryogenic expander 12. This cryogenic expander 12 is used to further cool the high-pressure cryogenic air using ultra-cold energy and then depressurize it to achieve low-pressure storage of the liquid air.

[0048] Furthermore, 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; wherein, 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 during charging; 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 vaporization; 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 vaporized gaseous air.

[0049] Furthermore, a first cryogenic pump 19 can be installed 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 return power; a first one-way valve 16 can be installed 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 unidirectional flow of return air. In addition, a second one-way valve 15 can also be installed 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 backflow of liquid air, ensure that the air flow direction meets the operating conditions, and improve the reliability and safety of system operation. This second one-way valve 15 can be installed between the cryogenic expander 12 and the liquid air storage tank 1.

[0050] In the above embodiment, the discharge voltage stabilization circuit can be further configured such that, under discharge conditions, in response to the pressure signal inside the liquid air storage tank 1, when the pressure inside the liquid air storage tank 1 is lower than a first preset value, the first cryogenic pump 19 is activated to transport a portion of the low-pressure liquid air to the cold storage heat exchange unit. The vaporized gaseous air is then reinjected into the liquefied air storage tank 1 via the opened first one-way valve 16. Furthermore, when the pressure inside the liquid air storage tank 1 is higher than a second preset value, the first cryogenic pump 19 is shut off, and the gas phase space inside the liquefied air storage tank 1 will continuously decrease as the liquid air flows out, thereby ensuring the pressure stability of the liquid air storage tank 1 under discharge conditions. The first and second preset values ​​can be adjusted according to actual process requirements. 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 inside the liquid air storage tank 1 to monitor the gas phase pressure inside the tank in real time and generate a pressure signal.

[0051] Preferably, the first check valve 16 can be a one-way flow regulating valve group or a functional valve combined with a flow regulating valve, achieving more precise pressure control through stepless adjustment of the return air flow. For example, when the pressure inside the liquid air storage tank 1 is lower than a first preset value, the first cryogenic pump 19 is started, and the pump speed and the opening of the first check valve 16 are adjusted according to the deviation between the measured pressure and the first preset value to control the flow rate of low-pressure liquid air entering the cold storage heat exchange unit, so that the return rate matches the tank pressure recovery rate; when the pressure inside the tank recovers to between the first and second preset values, partial return is maintained, and the return flow rate is gradually adjusted through the first check valve 16 to keep the pressure within a stable range, and the speed of the first cryogenic pump 19 is appropriately reduced to avoid excessive return causing the pressure to rise too quickly; when the pressure inside the tank is higher than the second preset value, the return flow rate can be gradually reduced to allow the tank pressure to naturally decrease to a stable value; if the tank pressure continues to rise, the return flow is completely stopped. The above implementation method enables continuous adjustment of the return air flow rate under discharge conditions, making the pressure in the liquid air storage tank 1 more stable and avoiding pressure fluctuations caused by frequent start-stop operations. It also better meets the requirements of liquid air vaporization, which is conducive to improving charging and discharging efficiency and cold energy recovery effect. In addition, the return air flow rate can be adjusted on demand according to external load requirements (such as grid fluctuations, power generation requirements, etc.), so that the system can adapt to different operating modes and improve overall flexibility.

[0052] The cold storage and heat exchange unit can be a device capable of realizing the cold storage and heat exchange functions described above. In one specific embodiment, referring to Figures 1-3, the cold storage and 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 material (air in this disclosure) and can also store or release 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 conducive to achieving efficient storage and release of cold energy and reducing cold energy loss. Under charging or discharging conditions, the temperature distribution of the cold storage medium can gradually change with 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 return port of the liquid air storage tank 1. The low-temperature end of the cold storage heat exchanger 2 is connected to the liquid air input port and the discharge return air output port of the liquid air storage tank 1, respectively. This disclosure does not impose any special restrictions on the specific form of the cold storage heat exchanger 2, such as it can be a packed bed, etc.

[0053] In another embodiment, the cold storage and heat exchange unit includes a heat exchanger and a cold storage tank. The heat exchanger is a device that regulates the temperature of the process stream by exchanging heat with a heat exchange medium at a temperature different from that of the process stream. Specifically, the heat exchange medium of the heat exchanger may include at least one of nitrogen, air, helium, brine, water, and an organic solvent (such as propane). The cold storage tank is used to store ultracold energy. For example, referring to Figures 4-6, the cold storage and 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. The first heat exchanger 21 and the second heat exchanger 22 each have a high-temperature end and a low-temperature end. 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, and the low-temperature end of the second heat exchanger 22 is connected to the input port of the cryogenic expander 12. The outlet end of the cryogenic 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 return 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 discharge conditions, 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. 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 charging conditions, 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. After the heat exchange medium is heated, it enters the first heat storage tank D5 for storage.

[0054] A second aspect of this disclosure provides a voltage stabilization method for a liquid air energy storage system implemented using the voltage stabilization device described in the first aspect of this disclosure, the method comprising:

[0055] During discharge, a portion of the low-pressure liquid air in the liquid air storage tank is drawn out and vaporized, and the resulting gaseous air is returned to the liquid air storage tank; wherein, the ultracold energy generated by the vaporization is recovered and used to cool the high-pressure cryogenic ambient air during charging.

[0056] The vaporization of low-pressure liquid air and the recovery of ultracold energy are achieved through the cold storage and heat exchange unit in the pressure stabilizing device described in one aspect of this disclosure, and the specific implementation method is as described above.

[0057] Furthermore, the method may also include:

[0058] During charging, the ultra-cold energy is used to cool the high-pressure cryogenic ambient air to obtain cooled air; wherein, the pressure of the high-pressure cryogenic ambient air can be greater than 3.8MPa and the temperature can be from -160℃ to -138℃; the pressure of the cooled air can be greater than 3.8MPa and the temperature can be from -166℃ to -146℃.

[0059] The cooled air is expanded and depressurized to obtain low-pressure liquid air; wherein, the expansion and depressurization can be achieved by a low-temperature expander 12; wherein, the pressure of the low-pressure liquid air can be 1.0~3.8MPa, and the temperature can be -168℃ to -141℃.

[0060] The low-pressure liquid air is stored in the liquid air storage tank.

[0061] Furthermore, the method may further include: acquiring a pressure signal within the liquid air storage tank during discharge; initiating the extraction of low-pressure liquid air and the recirculation of gaseous air when the pressure within the liquid air storage tank is lower than a first preset value; and stopping the extraction of low-pressure liquid air and the recirculation of gaseous air when the pressure within the liquid air storage tank is higher than a second preset value. The extraction of low-pressure liquid air and the recirculation of gaseous air can be started or stopped by the first cryogenic pump 19, as described above for specific implementation details.

[0062] In a third aspect, this disclosure provides a liquid air energy storage system, which includes the voltage stabilizing device described in the first aspect of this disclosure. In addition, the system may also include other devices for liquid air energy storage, and this disclosure does not have any particular limitations in this regard.

[0063] In one embodiment, referring to Figures 1-3, the system includes a pressure 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.

[0064] 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 sequentially along the direction of ambient air inflow. The first compressor 10 has an ambient air inlet 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 sequentially along the direction of air flow. The third expander 14 has a regasified air outlet port. The cooling heat exchange unit includes a ninth heat exchanger 9 connected 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 the second heat storage tank D1 and the 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 the third heat storage tank D3 and the third cold storage tank D4.

[0065] 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 via the low-temperature expander 12 and the second one-way valve 15. 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 exchanger 2 via the first low-temperature pump 19, and the high-temperature end of the cold storage heat exchanger 2 is connected to the discharge return air return port of the liquid air storage tank 1 via the first one-way valve 16, forming a discharge pressure stabilization circuit. The liquid air output port of the liquid air storage tank 1 is connected to the sixth heat exchanger 6 of the discharge heat exchange unit via the second low-temperature pump 17, and LNG is connected to the seventh heat exchanger 9 via the third low-temperature pump 18. The charging return air output port of the liquid air storage tank 1 (which shares a port with the discharge return air return port) is connected to the air input port of the second compressor 11 via the charging pressure control valve 20.

[0066] Referring to Figure 2, under charging conditions, ambient air (pressure 0.1 MPa, temperature -20℃ to 40℃) enters the charging heat exchange unit for compression and cooling to obtain high-pressure cryogenic ambient air. LNG provides supplemental cooling energy to 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 before entering the liquid air storage tank 1 for storage. When the internal pressure of the liquid air storage tank 1 exceeds the upper limit threshold of the pressure stabilization, the charging pressure control valve 20 opens, allowing the air in the gas phase space inside the liquid air storage tank 1 to flow back as charging return air RA-C and merge into the low-pressure cryogenic air that is about to enter the second compressor 11, thereby reducing the internal pressure of the liquid air storage tank 1.

[0067] Referring to Figure 3, under discharge conditions, the low-pressure liquid air in the liquid air storage tank 1 enters the discharge heat exchange unit for heating and expansion, vaporizing into revaporized air (pressure 1.5~2.0MPa, temperature -168℃ to -140℃). When the internal pressure of the liquid air storage tank 1 is lower than the first preset value (e.g., 1.6MPa), the first cryogenic pump 19 is started, so that part of the low-pressure liquid air in the liquid air storage tank 1 is transported to the cold storage heat exchanger 2 as discharge return air RA-D for vaporization. The vaporized gaseous air is then returned to the liquefied 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 (e.g., 1.8MPa), the first cryogenic pump 19 is turned off. The pressure of the gas phase space in the liquefied air storage tank 1 will continue to decrease as the liquid air flows out to the discharge heat exchange unit, thereby ensuring the pressure stability of the liquid air storage tank 1 under discharge conditions.

[0068] In another embodiment, referring to 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 thermal 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 cooling heat exchange unit, which are the same as those in the first embodiment.

[0069] 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 via the low-temperature expander 12 and the second one-way valve 15. The discharge return air output port of the liquid air storage tank 1 is connected to the low-temperature end of the first heat exchanger 21 via the first low-temperature pump 19, and the high-temperature end of the first heat exchanger 21 is connected to the discharge return air return port of the liquid air storage tank 1 via the first one-way valve 16, forming a discharge voltage stabilization circuit.

[0070] Referring to Figure 5, during charging, 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 then enters the second heat exchanger 22 for further cooling before entering the cryogenic expander 12 for further cooling and depressurization, and finally enters the liquid air storage tank 1 for storage. Referring to Figure 6, during discharging, when the internal pressure of the liquid air storage tank 1 is lower than the first preset value (e.g., 1.6 MPa), the first cryogenic pump 19 is activated, causing a portion of the low-pressure liquid air in the liquid air storage tank 1 to be transported as discharge return air RA-D to the first heat exchanger 21 for vaporization. The vaporized air then flows back into the liquefied 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 (e.g., 1.8 MPa), the first cryogenic pump 19 is shut off. The pressure in the gas phase space of the liquefied air storage tank 1 will continue to decrease as the liquid air flows out to the discharge heat exchange unit, thereby ensuring the pressure stability of the liquid air storage tank 1 during discharging.

[0071] In another embodiment, referring to Figures 7-9, the system includes a pressure stabilizing device A, which includes a liquid air storage tank 1 and a cold storage heat exchanger 2, the same as in the first embodiment. In addition, the system also 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 those in the previous two embodiments, and there is no external cooling module.

[0072] 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 connected sequentially along the direction of ambient air inlet. The first compressor 23 has an ambient air inlet 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 connected sequentially along the direction of air flow. The seventh expander 30 has a regasified air outlet port. The heat exchange media of the tenth heat exchanger 31 and the fifteenth heat exchanger 36 share the fourth thermal 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 thermal 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 thermal 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 thermal 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 thermal storage tank D9 and the eighth cold storage tank D10. In addition, the charging heat exchange unit also includes a charging reflux heat exchanger 41, which is used to exchange heat with the charging reflux air RA-C to recover cold energy during the charging operation. The charging reflux heat exchanger 41 can be connected in parallel with the thirteenth heat exchanger 34 and / or the fourteenth heat exchanger 35. Specifically, the charging reflux heat exchanger 41 has a charging reflux air inlet port, a charging reflux air outlet port, a heat exchange medium inlet port, and a heat exchange medium outlet port. The charging reflux air inlet port is connected to the charging reflux air outlet port of the liquid air storage tank 1 through the charging pressure control valve 20. The charging reflux air outlet port is connected to the air inlet port of the fifth compressor 25. The heat exchange medium inlet port is connected to the pipeline between the sixth compressor 26 and the high temperature end of the thirteenth heat exchanger 34. The heat exchange medium outlet port is connected to the high temperature end of the ultra-cold storage heat exchanger 2.

[0073] Referring to Figure 8, during charging, ambient air enters the charging heat exchange unit for compression and cooling to obtain high-pressure cryogenic ambient air. This high-pressure cryogenic liquid air then enters the cold storage heat exchanger 2 for further cooling before entering the cryogenic expander 12 for further cooling and depressurization. Finally, it enters the liquid air storage tank 1 for storage. When the internal pressure of the liquid air storage tank 1 exceeds the upper limit of the pressure stabilization threshold, the charging pressure control valve 20 opens, allowing the air in the gas phase space within the liquid air storage tank 1 to act as charging return air (RA-C). After heat exchange in the charging return heat exchanger 41, the air returns and merges with the low-pressure cryogenic air that is about to enter the fifth compressor 25, thereby reducing the internal pressure of the liquid air storage tank 1.

[0074] Referring to Figure 9, under discharge conditions, the low-pressure liquid air in the liquid air storage tank 1 enters the discharge heat exchange unit to be heated and expanded into re-vaporized air. When the internal pressure of the liquid air storage tank 1 is lower than the first preset value (e.g., 1.6 MPa), the first cryogenic 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 discharge return air RA-D for vaporization. The vaporized air is then returned to the liquefied 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 (e.g., 1.8 MPa), the first cryogenic pump 19 is turned off. The pressure in the liquid air storage tank 1 will continue to decrease as the liquid air flows out to the discharge heat exchange unit, thereby ensuring the pressure stability of the liquid air storage tank 1 under discharge conditions.

[0075] This disclosure solves key problems in existing liquid air energy storage technologies, such as pressure fluctuations and limited energy efficiency within the liquid air storage tank under discharge conditions. It effectively improves the charging and discharging efficiency of the system and provides an efficient, economical, and reliable energy storage solution for renewable energy consumption and grid peak shaving, with broad application prospects.

[0076] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0077] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0078] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A voltage stabilizing device for a liquid air energy storage system, characterized in that, 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 ultra-cold energy of the low-pressure liquid air from the liquid air storage tank under discharge conditions, and to use the ultra-cold energy to cool the high-pressure cryogenic ambient air under charging conditions; The voltage stabilizing device further includes a discharge voltage stabilizing circuit, which is configured to, under the discharge condition, transport a portion of the low-pressure liquid air in the liquid air storage tank to the cold storage and heat exchange unit for vaporization, and cause the resulting gaseous air to flow back to the liquid air storage tank.

2. The voltage stabilizing device according to claim 1, characterized in that, 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 cryogenic 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 one-way valve.

3. The voltage stabilizing device according to claim 2, characterized in that, The discharge voltage regulation circuit is configured to respond to a pressure signal inside the liquid air tank by starting the cryogenic pump when the pressure inside the liquid air tank is lower than a first preset value, and shutting down the cryogenic pump when the pressure inside the liquid air tank is higher than a second preset value.

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

5. The voltage stabilizing device according to claim 1, characterized in that, The cold storage and 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 solvent.

6. A voltage stabilization method for a liquid air energy storage system, characterized in that, The method includes: Under discharge conditions, a portion of the low-pressure liquid air in the liquid air storage tank is drawn out and vaporized, and the resulting gaseous air is returned to the liquid air storage tank. The ultracold energy generated by the vaporization is recovered and used to cool the high-pressure cryogenic ambient air during charging.

7. The method according to claim 6, characterized in that, The method also includes: During charging, the ultra-cold energy is used to cool the high-pressure cryogenic ambient air 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.

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

9. The method according to claim 6, characterized in that, The method also includes: The pressure signal inside the liquid air storage tank is acquired. When the pressure inside the liquid air storage tank is lower than a first preset value, the extraction of low-pressure liquid air and the return of gaseous air are initiated. When the pressure inside the liquid air storage tank is higher than a second preset value, the extraction of low-pressure liquid air and the return of gaseous air are stopped.

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

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