A high heat storage density liquid air energy storage system and method

Abstract

The present invention relates to the field of liquid air energy storage technology, and in particular to a high heat storage density liquid air energy storage system and method, comprising an air compression unit, an air liquefaction unit, a liquid air liquefaction unit, a cold storage unit, a heat storage unit, and an air expansion power generation unit; the first input end of the air compression unit is used to input ambient air, the second input end of the air compression unit is used to input electricity, the first output end of the air compression unit is connected to the first input end of the air liquefaction unit, the second output end of the air compression unit is connected to the first input end of the heat storage unit, and the third input end of the air compression unit is connected to the first output end of the heat storage unit. By optimizing the heat storage density and compression heat utilization, and combining cascade heat utilization with refrigeration technology, the present invention improves the cycle efficiency and power generation performance of the liquid air energy storage system, providing a more efficient solution for the practical application of liquid air energy storage technology.

Description

Technical Field

[0001] The present invention relates to the field of liquid air energy storage technology, and in particular to a high heat storage density liquid air energy storage system and method. Background Art

[0002] Liquid air energy storage (LAES) is considered one of the most promising large-scale energy storage technologies due to its unique advantages, including high energy density, unrestricted geographic location, long lifespan, and environmental friendliness. During periods of low electricity demand, electricity is stored as liquid air, while the high-temperature compression heat generated during the air compression process is stored to boost the performance of the air expander when needed. During peak periods, the liquid air, after being pressurized by a booster pump and low-temperature cold energy recovered and stored, drives the air expander to generate electricity.

[0003] At present, most of the research on liquid air energy storage systems focuses on optimizing the overall process of the system, and the recovery, storage and utilization of high-temperature air compression heat energy is one of the keys to improving the energy efficiency of the system. For example, the liquid air energy storage system with electric heat storage (ZL202011120983.4) drives the electric heater to heat the heat storage medium by coupling electric heating technology during energy storage, and stores the electrical energy in the form of high-temperature thermal energy, thereby achieving a significant increase in power generation. A method for operating a liquid air energy storage system that is thermoelectrically coupled with a thermal power unit (ZL202410924826.0) can achieve deep peak regulation, maintain the thermal power unit at rated operating conditions, and improve overall operating efficiency. In the existing technology, the low energy conversion efficiency of these two modes and the high price and cost of equipment are problems that need to be solved urgently. Summary of the Invention

[0004] The purpose of the present invention is to solve the shortcomings existing in the prior art, and to propose a high heat storage density liquid air energy storage system and method, which uses molten salt heat storage technology to efficiently recover and store the compression heat energy in the high temperature section above 150°C, significantly improving the heat storage density and fundamentally improving the power generation efficiency. In addition, the remaining compression heat of the system is output in the form of heating (85°C / 60°C) to improve the comprehensive energy utilization rate. At the same time, the medium and low temperature waste heat of 30 to 150°C is cascaded through the graded lithium bromide refrigeration unit for air pre-cooling, which greatly reduces the power consumption of traditional electric refrigeration systems. The above design not only improves the overall efficiency of the system, but also effectively controls the equipment cost, forming an efficient and economical liquid air energy storage solution, and providing a practical path to overcome the energy efficiency bottleneck in the prior art.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A high heat storage density liquid air energy storage system, comprising an air compression unit, an air liquefaction unit, a liquid air evaporation unit, a cold storage unit, a heat storage unit and an air expansion power generation unit;

[0007] The first input end of the air compression unit is used to input ambient air, the second input end of the air compression unit is used to input electricity, the first output end of the air compression unit is connected to the first input end of the air liquefaction unit, the second output end of the air compression unit is connected to the first input end of the heat storage unit, and the third input end of the air compression unit is connected to the first output end of the heat storage unit; the air liquefaction unit is connected to the liquid air liquefaction unit and the cold storage unit respectively, the liquid air liquefaction unit is connected to the air expansion power generation unit, and the air expansion power generation unit is connected to the heat storage unit;

[0008] The air compression unit is used to compress, purify and cool the ambient air, then expand and reduce the pressure to obtain liquid air, and the compression heat generated during the compression process is sequentially stored in the heat storage unit for subsequent use;

[0009] The air liquefaction unit cools and expands the compressed air to obtain low-temperature liquid air, which is stored in a liquid air storage tank;

[0010] The liquid gasification unit pressurizes the obtained low-temperature liquid air through a low-temperature pump and gasifies it through an evaporator, and the cold energy generated during the evaporation and gasification process is stored in a cold storage unit;

[0011] The cold storage unit stores the cold energy generated by gasification of liquid air in the cold storage packed bed, providing cold energy for the air liquefaction unit;

[0012] The heat storage unit receives the high-quality compression heat transmitted by the air compression unit, provides heat to the air expansion power generation unit, and the excess compression heat is used to provide heat to users;

[0013] The air expansion power generation unit is heated by the high-temperature molten salt of the heat storage unit and then expands to generate power.

[0014] By adopting the above technical solution: during the period of low electricity consumption, the ambient air is compressed, purified and cooled, expanded and depressurized to obtain liquid air, which is stored in the liquid air storage tank, and the stored air compression heat energy is recovered and stored in the heat storage unit; during the period of peak electricity consumption, the liquid air is pressurized, evaporated, gasified and preheated, and then expanded to generate electricity, and the evaporation and gasification cold energy is recovered; the air expansion unit absorbs the stored compression heat to generate electricity.

[0015] Preferably, the air compression unit comprises:

[0016] a first compressor, wherein the first input end and the second input end of the first compressor serve as the first input end and the second input end of the air compression unit respectively;

[0017] a first cooler, wherein a first input end of the first cooler is connected to an output end of the first compressor, and a second input end of the first cooler is connected to a heat storage unit;

[0018] a pre-cooling unit, wherein the input end of the pre-cooling unit is connected to the first output end of the first cooler;

[0019] an air purifier, wherein the input end of the air purifier is connected to the output end of the pre-cooling unit;

[0020] a second compressor, wherein an input end of the second compressor is connected to an output end of the air purifier;

[0021] a second cooler, wherein a first input end of the second cooler is connected to an output end of the second compressor;

[0022] a third compressor, wherein an input end of the third compressor is connected to the first output end of the second cooler;

[0023] a third cooler, wherein a first input end of the third cooler is connected to an output end of the third compressor;

[0024] A fourth cooler, wherein the first input end of the fourth cooler is connected to the first output end of the third cooler, and the second input end of the fourth cooler is connected to the heat storage unit; the second input end of the first cooler, the second input end of the second cooler, and the second input end of the third cooler are connected in parallel as the third input end of the air compression unit, and are connected to the first output end of the heat storage unit; the second output end of the first cooler, the second output end of the second cooler, and the second output end of the third cooler are connected in parallel as the second output end of the air compression unit and are connected to the first input end of the heat storage unit.

[0025] By adopting the above technical solution: the compressors in the air compression unit here are all selected as high-temperature and high-pressure ratio compressors, taking into account the compression power consumption and the thermal energy grade of the heat exchange fluid to improve the heat storage density.

[0026] Preferably, the pre-cooling unit includes a graded lithium bromide refrigeration unit, a first pre-cooler and a second pre-cooler connected in sequence, and the graded lithium bromide refrigeration unit includes a double-effect absorption refrigerator, an evaporative absorption heat exchanger and a single-effect absorption refrigerator, and the double-effect absorption refrigerator, the evaporative absorption heat exchanger and the single-effect absorption refrigerator are connected in series in sequence.

[0027] By adopting the above technical solution: the pre-cooling unit here uses energy in a cascade manner, efficiently absorbing the high-temperature air waste heat (155°C) from the outlet of the first-stage compressor. When the lithium bromide refrigeration unit exchanges heat with the heat source, if the heat source is cooled too much, the heat exchange temperature difference will be reduced, thereby reducing the heat transfer efficiency and possibly affecting the regeneration capacity of the lithium bromide solution in the generator. Usually, the heat source cooling is usually designed to be no more than 20°C to ensure the heat exchange efficiency and heat source utilization of the system. The available temperature range of the heat source directly affects the effective heat that can be transferred. It is necessary to ensure that the heat source outlet temperature is within the effective working range (usually not less than 80°C). Taking 20°C as a temperature interval, the heat source is reduced from 155°C to 86°C. The lithium bromide unit is connected in series with a double-effect absorption chiller, an evaporative absorption heat exchanger, and a single-effect absorption chiller. The unit absorbs this part of the heat, and the total cooling capacity can be finally converted according to the corresponding refrigeration coefficient COP. In order to better match the cooling and heating amounts in the present invention, the air passes through the first precooler (cooled to 28°C) and the second precooler (cooled to 17°C) in sequence, and the mainstream air enters the molecular sieve after being cooled.

[0028] Preferably, the heat storage unit includes a molten salt cold tank, a first molten salt pump, a molten salt hot tank, a second molten salt pump, a first heater, a medium-temperature water storage tank, a first circulating water pump, a second heater, a low-temperature water storage tank and a second circulating water pump;

[0029] The output end of the molten salt cold tank is connected to the input end of the first molten salt pump, the output end of the first molten salt pump is connected to the third input end of the air compression unit, the input end of the molten salt hot tank is connected to the second output end of the air compression unit, the output end of the molten salt hot tank is connected to the input end of the second molten salt pump, the output end of the second molten salt pump is connected to the first input end of the air expansion power generation unit, and the input end of the molten salt cold tank is connected to the output end of the first heater;

[0030] The input end of the medium-temperature water storage tank is connected to the third output end of the air compression unit, the input end of the first circulating water pump is connected to the output end of the medium-temperature water storage tank, the input end of the low-temperature water storage tank is connected to the third output end of the air expansion power generation unit, and the input end of the second circulating water pump is connected to the output end of the low-temperature water storage tank;

[0031] The second input end of the air expansion power generation unit is connected to the second output end of the heat storage unit, the first output end of the air expansion power generation unit is connected to the second input end of the heat storage unit, and the second output end of the air expansion power generation unit is used to output electricity.

[0032] By adopting the above technical solution: the system adopts a high-pressure ratio air compressor and distributes the compression ratio in nearly equal proportion to comprehensively design the compressed air process, so that the outlet air temperature reaches about 270°C, so the compression heat storage temperature reaches above 250°C, thereby using low-cost molten salt as a heat storage medium and heat transfer medium, and the high-energy density compression heat is recovered and reheated to expand the generator inlet temperature. The higher the temperature, the higher the power generation, thereby fundamentally improving the system cycle efficiency.

[0033] Preferably, the air liquefaction unit includes an air separator, a liquefaction main heat exchanger, a cryogenic gas expander, a cryogenic liquid expander, a throttle valve and a gas-liquid separator;

[0034] The input end of the air separator is connected to the first output end of the air compression unit, the first input end of the liquefied main heat exchanger is connected to the first output end of the air separator, the second input end of the liquefied main heat exchanger is connected to the second output end of the air separator, the third input end of the liquefied main heat exchanger is connected to the first output end of the gas-liquid separator, and the fourth input end of the liquefied main heat exchanger is connected to the first output end of the cold storage unit; the first output end of the liquefied main heat exchanger is connected to the third input end of the low-temperature gas expander, the second output end of the liquefied main heat exchanger is connected to the input end of the low-temperature liquid expander, the third output end of the liquefied main heat exchanger is connected to the third input end of the air compression unit, and the fourth output end of the liquefied main heat exchanger is connected to the first input end of the cold storage unit;

[0035] The output end of the low-temperature gas expander is connected to the third input end of the liquefaction main heat exchanger, the output end of the low-temperature liquid expander is connected to the input end of the throttle valve, and the output end of the throttle valve is connected to the input end of the gas-liquid separator.

[0036] Preferably, the liquid air aeration unit includes a liquid air storage tank, a cryogenic pump and an evaporator; the input end of the liquid air storage tank is connected to the first output end of the gas-liquid separator, the output end of the liquid air storage tank is connected to the input end of the cryogenic pump, the output end of the cryogenic pump is connected to the first input end of the evaporator, the first output end of the evaporator is connected to the air expansion power generation unit, the second input end of the evaporator is connected to the second output end of the cold storage unit, and the first output end of the evaporator serves as the first output end of the liquid air aeration unit.

[0037] Preferably, the cold storage unit includes a cold storage packed bed, a first circulation fan, and a second circulation fan; the input end of the first circulation fan is connected to the second output end of the evaporator, the output end of the first circulation fan is connected to the fourth input end of the liquefaction main heat exchanger, the input end of the second circulation fan is connected to the fourth output end of the liquefaction main heat exchanger, and the output end of the second circulation fan is connected to the second input end of the evaporator;

[0038] The cold storage packed bed is used to store the cold energy released by the liquid-to-air liquefaction unit and transfer it to the air liquefaction unit.

[0039] Preferably, the air expansion power generation unit comprises:

[0040] An air preheater, wherein a first input end of the air preheater serves as a first input end of the air expansion power generation unit, and the first input end of the air preheater is connected to an output end of the liquid gasification unit;

[0041] a first heater, wherein a first input end of the first heater is connected to a first output end of the air preheater;

[0042] a first expander, wherein an input end of the first expander is connected to a first output end of the first heater;

[0043] a second heater, wherein a first input end of the second heater is connected to an output end of the first expander;

[0044] a second expander, wherein an input end of the second expander is connected to a first output end of the second heater;

[0045] a third heater, wherein a first input end of the third heater is connected to an output end of the second expander;

[0046] a third expander, wherein an input end of the third expander is connected to the first output end of the third heater;

[0047] a fourth heater, wherein a first input end of the fifth heater is connected to an output end of the third expander;

[0048] a fourth expander, wherein the input end of the fourth expander is connected to the first output end of the fourth heater; the first output end and the second output end of the fourth expander serve as the second output end and the third output end of the air expansion power generation unit, respectively;

[0049] The second input end of the first heater, the second input end of the second heater, the second input end of the third heater and the second input end of the fourth heater are connected in parallel as the second input end of the air expansion power generation unit and are connected to the second output end of the heat storage unit; the second output end of the first heater, the second output end of the second heater, the second output end of the third heater and the second output end of the fourth heater are connected in parallel as the first output end of the air expansion power generation unit and are connected to the second input end of the heat storage unit.

[0050] By adopting the above technical solution: the power generation power of the air expansion power generation unit here can be adjusted according to the heat storage temperature of the heat storage unit, and the stored heat comes from the compression heat of the system itself.

[0051] The present invention also provides a high heat storage density liquid air energy storage method, which is implemented based on the above-mentioned high heat storage density liquid air energy storage system, and the method includes:

[0052] Air compression liquefaction storage mode: Ambient air is initially compressed by the first compressor. The compressed air is cooled by the first cooler and pre-cooling unit before entering the air purifier. In the air purifier, the adsorbent removes moisture and carbon dioxide from the air. The air is then further compressed to high pressure by the second and third compressors. The high-grade compression heat generated during the air compression process is recovered by molten salt and stored in the heat storage unit. After the compressed high-temperature air is cooled, the graded lithium bromide refrigeration unit provides cooling capacity. The air is further cooled to a low temperature by the liquefaction main heat exchanger, and then enters the low-temperature gas expander and low-temperature liquid expander for expansion and pressure reduction, and part of the air is liquefied. The liquefied air is separated into liquid air by a throttle valve and a gas-liquid separator, and the liquid air is stored in a liquid air storage tank.

[0053] Air expansion power generation mode: The liquid air output from the liquid air storage tank is pressurized to high pressure by a cryogenic pump and then enters the evaporator for a liquid-to-gas phase change process. The cold energy generated by the vaporization is stored in the cold storage unit through the pressurized fluid. The vaporized high-pressure air enters the air expansion power generation unit and expands through the multi-stage expander to perform work. During the air expansion power generation process, the heat storage unit releases heat energy to heat the air before entering each stage of the expander to maintain the operation of the expansion power generation unit.

[0054] Waste heat heating mode: open the bypass pipeline of the first heater, turn on the second molten salt pump, the hot molten salt in the molten salt hot tank flows to the first heater through the pipeline, the residual compression heat stored in the heat storage unit uses molten salt as the heat carrier to exchange heat with the heating water, thereby providing heat energy to the user through the heater, and the molten salt eventually returns to the molten salt cold tank; open the bypass pipeline of the second heater, turn on the second circulating water pump, the pressurized hot water in the medium-temperature water storage tank flows to the second heater through the pipeline, the residual compression heat stored in the heat storage unit uses pressurized water as the heat carrier to exchange heat with the heating water, thereby providing heat energy to the user through the heater, and the pressurized water eventually returns to the low-temperature water storage tank; ultimately, the waste heat is recycled and utilized, and the overall energy utilization efficiency of the system is improved.

[0055] By adopting the above technical solution: The present invention efficiently distributes and utilizes the heat energy generated during the air compression process, and adopts a molten salt heat storage solution in the high temperature section above 150°C, which significantly improves the heat storage density and power generation power. The heat from room temperature to 150°C is used to preheat the air intake of the air expansion power generation unit, further improving the power generation efficiency of the system. In addition, a lithium bromide refrigeration unit is integrated in the system, which absorbs the waste heat at the compressor outlet through cascade refrigeration technology, pre-cools the air entering the air purifier, reduces the power consumption of traditional electric refrigeration, and thus improves the overall energy efficiency. The present invention improves the cycle efficiency and power generation performance of the liquid air energy storage system by optimizing the heat storage density and compression heat utilization, combining cascade heat utilization with refrigeration technology, and provides a more efficient solution for the practical application of liquid air energy storage technology.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] 1. This invention proposes a high-temperature molten salt heat storage technology for liquid air energy storage, which can store higher-grade compression heat and achieve a heat storage density of up to 64.32MJ / m 3 above.

[0058] 2. This invention utilizes an integrated lithium bromide refrigeration unit operation strategy. Based on actual demand, when the air temperature at the first compressor outlet is high, the lithium bromide unit absorbs heat to generate corresponding cooling capacity, which is used to pre-cool the air entering the air-to-liquid power generation unit, achieving multi-stage and circular energy utilization. The units are connected in series, and temperature zones are used to achieve cascaded energy utilization.

[0059] 3. The present invention rationally designs the air compression unit and the heat storage unit so that the obtained high-quality compression heat can be used to increase the power generation capacity of liquid air.

[0060] 4. The present invention provides a feasible method and solution for realizing the coupling of a high heat storage density liquid air energy storage system with a lithium bromide unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is a structural schematic diagram of the present invention;

[0062] Figure 2 This is a structural diagram of a pre-cooling unit in an embodiment of the present invention;

[0063] Figure 3 1 is a performance comparison chart of independent LAES systems with different cold and heat storage materials in an embodiment of the present invention.

[0064] Among them, the air compression unit 100, the first compressor 101, the first cooler 102, the pre-cooling unit 103, the air purifier 104, the second compressor 105, the second cooler 106, the third compressor 107, the third cooler 108, and the fourth cooler 109; the air liquefaction unit 200, the air separator 201, the liquefaction main heat exchanger 202, the low-temperature gas expander 203, the low-temperature liquid expander 204, the throttle valve 205, and the gas-liquid separator 206; the liquid gas liquefaction unit 300, the liquid air storage tank 301, the cryogenic pump 302, and the evaporator 303; the cold storage unit 400, the cold storage packed bed 401, First circulating fan 402, second circulating fan 403; air expansion power generation unit 500, air preheater 501, first heater 502, first expander 503, second heater 504, second expander 505, third heater 506, third expander 507, fourth heater 508, fourth expander 509; heat storage unit 600, molten salt cold tank 601, first molten salt pump 602, molten salt hot tank 603, second molten salt pump 604, first heater 605, medium-temperature water storage tank 606, first circulating water pump 607, second heater 608, low-temperature water storage tank 609, second circulating water pump 610. DETAILED DESCRIPTION

[0065] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present invention.

[0066] It should be noted that the terms used herein are only for describing specific embodiments and should not be understood as indicating or implying relative importance. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0067] A high heat storage density liquid air energy storage system includes an air compression unit 100, an air liquefaction unit 200, a liquid air liquefaction unit 300, a cold storage unit 400, a heat storage unit 600 and an air expansion power generation unit 500;

[0068] The first input end of the air compression unit 100 is used to input ambient air, the second input end of the air compression unit 100 is used to input electricity, the first output end of the air compression unit 100 is connected to the first input end of the air liquefaction unit 200, the second output end of the air compression unit 100 is connected to the first input end of the heat storage unit 600, and the third input end of the air compression unit 100 is connected to the first output end of the heat storage unit 600; the air liquefaction unit 200 is respectively connected to the liquid air liquefaction unit 300 and the cold storage unit 400, the liquid air liquefaction unit 300 is connected to the air expansion power generation unit 500, and the air expansion power generation unit 500 is connected to the heat storage unit 600;

[0069] The air compression unit 100 is used to compress, purify and cool ambient air, then expand and reduce the pressure to obtain liquid air. The compression heat generated during the compression process is sequentially stored in the heat storage unit 600 for subsequent use;

[0070] The air liquefaction unit 200 cools and expands the compressed air to obtain low-temperature liquid air, which is then stored in a liquid air storage tank.

[0071] The liquid gasification unit 300 pressurizes the obtained low-temperature liquid air through a low-temperature pump and a gasification process of an evaporator, and stores the cold energy generated during the evaporation and gasification process in a cold storage unit;

[0072] The cold storage unit 400 stores the cold energy generated by gasification of liquid air in the cold storage packed bed, providing cold energy for the air liquefaction unit;

[0073] The air expansion power generation unit 500 is heated by the high-temperature molten salt of the heat storage unit and then expands to generate power;

[0074] The heat storage unit 600 receives the high-quality compression heat transmitted by the air compression unit 100, provides heat for the air expansion power generation unit, and the excess compression heat is used to provide heat for users.

[0075] In this embodiment, the energy storage system integrates high-efficiency cold energy, high-density heat storage and waste heat recovery and utilization, which can achieve high-grade heat utilization and effectively improve the system's power generation power and cycle efficiency. In the energy storage stage, the ambient air is further compressed to high pressure after preliminary compression and air purification, and then liquid air is obtained by cooling the pressurized air and expanding and reducing the pressure, while recovering high-density compressed heat energy. In the energy release stage, the liquid air is pressurized to high pressure by a low-temperature pump, evaporates and vaporizes to release cold energy to the pressurized air and stores it, and then enters the air expansion unit to expand and generate electricity. In addition to being used to heat the air for expansion and power generation, the excess air compression heat energy can also be used to supply municipal heat users. The present invention improves the recovery and storage efficiency of evaporation and vaporization cold energy through pressurized air, and efficiently distributes and utilizes air compression heat energy.

[0076] Among them, such as Figure 1 As shown, the air compression unit is used to compress and purify the ambient air, the air liquefaction unit expands and reduces the pressure to obtain liquid air and stores it in a liquid air storage tank, the liquid air atomization unit pumps the liquid air to high pressure and then vaporizes it through an evaporator, and stores the cold energy generated during the evaporation and vaporization process in the cold storage unit, the liquid air is transmitted to the air expansion power generation system, and the air compression heat generated during the compression process is stored in the heat storage unit;

[0077] In the above embodiments, the cold storage unit utilizes one or a combination of sensible heat storage or solid-liquid phase change storage. Heat exchange is performed using a pressurized fluid, such as propane, air, or carbon dioxide. The storage medium can be sealed ice balls, sand, concrete, phase change materials, or pressurized fluids (which serve as both the heat exchange and storage media).

[0078] In the above embodiments, the heat storage unit stores heat in the form of one or more of sensible heat, latent heat, or chemical reaction heat. The heat storage medium used can be water, paraffin, inorganic crystalline hydrated salt, molten salt, or stone. The heat storage medium is stored in an insulated container; the fluid conveying equipment is a pump, a compressor, or a fan.

[0079] Specifically, the air compression unit 100 can adopt single-stage compression or multi-stage compression. When multi-stage compression is adopted, the air compression unit 100 includes:

[0080] A first compressor 101, wherein a first input end and a second input end of the first compressor 101 serve as a first input end and a second input end of the air compression unit 100 respectively;

[0081] A first cooler 102, wherein a first input end of the first cooler 102 is connected to an output end of the first compressor 101, and a first output end of the first cooler 102 serves as a second output end of the air compression unit 100;

[0082] A pre-cooling unit 103, wherein the input end of the pre-cooling unit 103 is connected to the first output end of the first cooler 102;

[0083] An air purifier 104, wherein the input end of the air purifier 104 is connected to the output end of the pre-cooling unit 103;

[0084] A second compressor 105 , wherein an input end of the second compressor 105 is connected to an output end of the air purifier 104 ;

[0085] A second cooler 106 , wherein a first input end of the second cooler 106 is connected to an output end of the second compressor 105 ;

[0086] a third compressor 107 , wherein an input end of the third compressor 107 is connected to a first output end of the second cooler 106 ;

[0087] A third cooler 108 , wherein a first input end of the third cooler 108 is connected to an output end of the third compressor 107 ;

[0088] a fourth cooler 109 , wherein a first input end of the fourth cooler 109 is connected to a first output end of the third cooler 108 , and a second input end of the fourth cooler 109 is connected to the heat storage unit 600 ;

[0089] The second input end of the first cooler 102, the second input end of the second cooler 106, and the second input end of the third cooler 108 are connected in parallel as the second input end of the air compression unit 100 and connected to the first output end of the heat storage unit 600; the second output end of the first cooler 102, the second output end of the second cooler 106, and the second output end of the third cooler 108 are connected in parallel as the second output end of the air compression unit 100 and connected to the first input end of the heat storage unit 600.

[0090] Specifically, the precooling unit 103 includes a staged lithium bromide refrigeration unit 1031, a first precooler 1032, and a second precooler 1033 connected in sequence. The staged lithium bromide refrigeration unit 1031 includes a double-effect absorption refrigerator, an evaporative absorption heat exchanger and a single-effect absorption refrigerator. The double-effect absorption refrigerator, the evaporative absorption heat exchanger and the single-effect absorption refrigerator are connected in series in sequence.

[0091] In this embodiment, the pre-cooling unit here utilizes energy in a cascade manner, efficiently absorbing the waste heat of the high-temperature air from the outlet of the first-stage compressor, and then converting it into cold energy for pre-cooling the gas about to enter the air purifier, thereby achieving effective energy utilization and improving process efficiency.

[0092] In this embodiment, the air compression unit: the ambient air is initially compressed by the first compressor unit 101, cooled by the first cooler 102 and the pre-cooling unit 103, and then passed through the air purifier 104 to remove water and carbon dioxide in the air, and further compressed to high pressure by the second compressor 105 and the third compressor 107, and cooled by the second cooler 106 and the third cooler 108 in turn. The compression heat obtained during the whole process is stored in the heat storage unit, and then the air is cooled by the fourth cooler, and the heat is stored to facilitate preheating for the subsequent expansion stage.

[0093] Specifically, the air liquefaction unit 200 includes an air separator 201, a liquefaction main heat exchanger 202, a cryogenic gas expander 203, a cryogenic liquid expander 204, a throttle valve 205 and a gas-liquid separator 206;

[0094] The input end of the air separator 201 is connected to the first output end of the air compression unit 100, the first input end of the liquefied main heat exchanger 202 is connected to the first output end of the air separator 201, the second input end of the liquefied main heat exchanger 202 is connected to the second output end of the air separator 201, the third input end of the liquefied main heat exchanger 202 is connected to the first output end of the gas-liquid separator 206, and the fourth input end of the liquefied main heat exchanger 202 is connected to the first output end of the cold storage unit 400; the first output end of the liquefied main heat exchanger 202 is connected to the third input end of the low-temperature gas expander 203, the second output end of the liquefied main heat exchanger 202 is connected to the input end of the low-temperature liquid expander 204, the third output end of the liquefied main heat exchanger 202 is connected to the third input end of the air compression unit 100, and the fourth output end of the liquefied main heat exchanger 202 is connected to the first input end of the cold storage unit 400;

[0095] The output end of the low-temperature gas expander 203 is connected to the third input end of the liquefaction main heat exchanger 202, the output end of the low-temperature liquid expander 204 is connected to the input end of the throttle valve 205, and the output end of the throttle valve 205 is connected to the input end of the gas-liquid separator 206.

[0096] In this embodiment, the air liquefaction unit: the compressed air is divided into two parts by the air separator 201 and enters the liquefaction main heat exchanger 202, one part of which is cooled and reduced in pressure by the low-temperature gas expander 203, and the other part enters the low-temperature liquid expander 204 to perform work, and then passes through the throttle valve 205 to obtain a gas-liquid mixture to the gas-liquid separator 206. The separated gas and the gas that has passed through the low-temperature gas expander return to the liquefaction main heat exchanger together, and finally merge into the air compression unit.

[0097] Specifically, the liquid air aeration unit 300 includes a liquid air storage tank 301, a cryogenic pump 302 and an evaporator 303; the input end of the liquid air storage tank 301 is connected to the first output end of the gas-liquid separator 206, the output end of the liquid air storage tank 301 is connected to the input end of the cryogenic pump 302, the output end of the cryogenic pump 302 is connected to the first input end of the evaporator 303, the first output end of the evaporator 303 is connected to the expansion power generation unit 500, the second input end of the evaporator 303 is connected to the second output end of the cold storage unit 400, and the first output end of the evaporator 303 serves as the first output end of the liquid air aeration unit 300.

[0098] The evaporator 303 includes but is not limited to the following three evaporative cooling structures: direct evaporative cooling, indirect evaporative cooling or dew point evaporative cooling.

[0099] In this embodiment, the liquid air liquefaction unit: the liquid air separated in the air liquefaction unit is stored in the liquid air storage tank 301, pressurized to high pressure by the low-temperature pump 302, and the high-pressure liquid air enters the evaporator 303 to evaporate and gasify, releasing cold energy to the cold storage packed bed and storing it.

[0100] Specifically, the cold storage unit 400 includes a cold storage filled bed 401, a first circulation fan 402 and a second circulation fan 403;

[0101] The input end of the first circulation fan 402 is connected to the second output end of the evaporator 303, the output end of the first circulation fan 402 is connected to the fourth input end of the liquefaction main heat exchanger 202, the input end of the second circulation fan 403 is connected to the fourth output end of the liquefaction main heat exchanger 202, and the output end of the second circulation fan 403 is connected to the second input end of the expander 303.

[0102] The cold storage packed bed 401 is used to store the cold energy released by the liquid-to-air liquefaction unit and transfer it to the air liquefaction unit.

[0103] In this embodiment, the cold storage unit: the cold energy released by the evaporation and gasification of liquid air is stored in the cold storage packed bed 401, and the first circulation fan 402 and the second circulation fan 403 serve as the driving force for the air in the packed bed.

[0104] Specifically, the air expansion power generation unit 500 can adopt single-stage expansion or multi-stage expansion. When multi-stage expansion is adopted, the air expansion power generation unit 500 includes:

[0105] An air preheater 501, wherein a first input end of the air preheater 501 serves as a first input end of the air expansion power generation unit 500 and is connected to a first output end of the liquid gasification unit expander 303;

[0106] A first heater 502, wherein an input end of the first heater 502 is connected to a first output end of the air preheater 501;

[0107] a first expander 503 , wherein an input end of the first expander 503 is connected to a first output end of the second heater 502 ;

[0108] a second heater 504 , wherein a first input end of the second heater 504 is connected to an output end of the second expander 503 ;

[0109] a second expander 505 , wherein an input end of the second expander 505 is connected to a first output end of the second heater 504 ;

[0110] a third heater 506 , wherein a first input end of the third heater 506 is connected to an output end of the second expander 505 ;

[0111] a third expander 507 , wherein an input end of the third expander 507 is connected to a first output end of the third heater 506 ;

[0112] a fourth heater 508 , wherein a first input end of the fourth heater 508 is connected to an output end of the third expander 507 ;

[0113] a fourth expander 509 , wherein an input end of the fourth expander 509 is connected to a first output end of the fourth heater 508 ;

[0114] The second input end of the first heater 502, the second input end of the second heater 504, the second input end of the third heater 506 and the second input end of the fourth heater 508 are connected in parallel as the second input end of the air expansion power generation unit 500 and are connected to the second output end of the heat storage unit 600; the second output end of the first heater 502, the second output end of the second heater 504, the second output end of the third heater 506 and the second output end of the fourth heater 508 are connected in parallel as the first output end of the air expansion power generation unit 500 and are connected to the second input end of the heat storage unit 600.

[0115] In this embodiment, the air expansion power generation unit: the air is expanded and generates electricity by passing through the first expander 503, the second expander 505, the third expander 507, and the fourth expander 509 in sequence, and is heated by the air preheater 501, the first heater 503, the second heater 504, the third heater 506 and the fourth heater 508 in sequence, and the heater medium is molten salt.

[0116] Specifically, the heat storage unit 600 includes a molten salt cold tank 601, a first molten salt pump 602, a molten salt hot tank 603, a second molten salt pump 604, a first heater 605, a medium-temperature water storage tank 606, a first circulating water pump 607, a second heater 608, a low-temperature water storage tank 609, and a second circulating water pump 610;

[0117] The output end of the molten salt cold tank 601 is connected to the input end of the first molten salt pump 602, the output end of the first molten salt pump 602 is connected to the third input end of the air compression unit 100, the input end of the molten salt hot tank 603 is connected to the second output end of the air compression unit 100, the output end of the molten salt hot tank 603 is connected to the input end of the second molten salt pump 604, the output end of the second molten salt pump 604 is connected to the first input end of the air expansion power generation unit 500, and the input end of the molten salt cold tank 601 is connected to the output end of the first heater 605;

[0118] The input end of the medium-temperature water storage tank 606 is connected to the third output end of the air compression unit 100, the input end of the first circulating water pump 607 is connected to the output end of the medium-temperature water storage tank 606, the input end of the low-temperature water storage tank 609 is connected to the third output end of the air expansion power generation unit 500, and the input end of the second circulating water pump 610 is connected to the output end of the low-temperature water storage tank 609;

[0119] The second input end of the air expansion power generation unit 500 is connected to the second output end of the heat storage unit 600, the first output end of the air expansion power generation unit 500 is connected to the second input end of the heat storage unit 600, and the second output end of the air expansion power generation unit 500 is used to output electricity.

[0120] In this embodiment, the heat storage unit: the molten salt cold tank 601 recovers the compression heat obtained by the air compression unit through the first molten salt pump 602 and stores it in the molten salt hot tank 603, and then transmits it to the air expansion power generation unit 500 through the second molten salt pump; the low-temperature water storage tank 609 is pumped to the air compression unit through the second circulating water pump 610 and obtains the waste heat of the compressed air, which is then stored in the medium-temperature water storage tank 606, and then preheated through the first circulating water pump 607 to the air about to enter the expansion power generation unit 500, and the excess heat is provided to the user through the first heater 605 and the second heater 608.

[0121] In the above-mentioned embodiments, the present invention cleverly utilizes pressurization technology to effectively broaden the liquid-phase temperature range of the heat exchange fluid, thereby enabling the recovery, storage, and efficient utilization of a single fluid within different temperature ranges, particularly for the cold energy released during the evaporation and vaporization of liquid air. This innovation not only significantly enhances heat exchange and storage efficiency but also greatly simplifies the system structure, effectively reducing the initial investment cost of the equipment, demonstrating extremely high practical value and economic benefits.

[0122] In the above-mentioned embodiment, the integrated lithium bromide refrigeration system operation strategy provided by the present invention can be adapted to actual needs. When the air temperature at the outlet of the first compressor is high, a cascade refrigeration process efficiently absorbs excess heat from the compressor outlet and uses it to pre-cool the air entering the air purifier. This approach effectively reduces the power consumption of electric refrigeration in traditional systems and optimizes the overall energy efficiency of the system.

[0123] In the above embodiments, the present invention rationally designs the air compression unit and the heat storage unit so that the obtained high-quality compression heat can be used to improve the power generation power and cycle power efficiency of liquid air.

[0124] In the above embodiment, the heat storage unit is combined with molten salt heat storage technology, and the system adopts a molten salt heat storage solution in the high temperature range above 150°C, which significantly improves the heat storage density and increases the power generation capacity of the liquid air energy storage system.

[0125] A high heat storage density liquid air energy storage method is implemented based on the above-mentioned high heat storage density liquid air energy storage system, and the method comprises:

[0126] Air compression liquefaction storage mode: Ambient air is initially compressed by the first compressor 101, and the compressed air is cooled by the first cooler 102 and the pre-cooling unit 103 before entering the air purifier 104. In the air purifier 104, the adsorbent removes moisture and carbon dioxide from the air, and then the air is further compressed to high pressure by the second compressor 105 and the third compressor 107; the high-grade compression heat generated during the air compression process is recovered by molten salt and stored in the heat storage unit 600; after the compressed high-temperature air is cooled, the graded lithium bromide refrigeration unit provides cooling capacity, and the air is further cooled to a low temperature by the liquefaction main heat exchanger 202, and then enters the low-temperature gas expander 203 and the low-temperature liquid expander 204 for expansion and pressure reduction, and part of the air is liquefied; the liquefied air is separated into liquid air by the throttle valve 205 and the gas-liquid separator 206, and the liquid air is stored in the liquid air storage tank 301.

[0127] Air expansion power generation mode: The liquid air output from the liquid air storage tank 301 is pressurized to high pressure by the cryogenic pump 302, and then enters the evaporator 303 for a liquid-to-gas phase change process. The cold energy generated by vaporization is stored in the cold storage unit 400 through the pressurized fluid; the vaporized high-pressure air enters the air expansion power generation unit 500, and expands and performs work through the multi-stage expander; during the air expansion power generation process, the heat storage unit 600 releases heat energy to heat the air before entering the expanders at each stage, which is used to maintain the operation of the expansion power generation unit.

[0128] Waste heat heating mode: open the bypass pipeline of the first heater 605, turn on the second molten salt pump 604, the hot molten salt in the molten salt hot tank 603 flows to the first heater 605 through the pipeline, the remaining compression heat stored in the heat storage unit 600 uses molten salt as a heat carrier to exchange heat with the heating water, thereby providing heat energy to the user through the heater, and the molten salt finally returns to the molten salt cold tank 601; open the bypass pipeline of the second heater 608, turn on the second circulating water pump 610, the pressurized hot water in the medium-temperature water storage tank 606 flows to the second heater 608 through the pipeline, the remaining compression heat stored in the heat storage unit 600 uses pressurized water as a heat carrier to exchange heat with the heating water, thereby providing heat energy to the user through the heater, and the pressurized water finally returns to the low-temperature water storage tank 609; ultimately, the waste heat is recycled and utilized, and the overall energy utilization efficiency of the system is improved.

[0129] To further illustrate the embodiments of the present invention, Figure 1 The system structure of liquid air energy storage coupled with lithium bromide unit is shown. Figure 2 This is the structural diagram of the pre-cooling unit. Figure 3 The figure is a comparison chart of the cycle efficiency and cogeneration efficiency of the three structures when other conditions are the same. It is not difficult to see that the present invention can effectively improve the efficiency of both.

[0130] Figure 1 The intermediate heat storage fluid uses atmospheric pressure molten salt as the heat exchange fluid, and the temperature reaches 253°C after three-stage compression. The heat recovery fluid is pressurized water. The cold storage filling bed uses solid stone as the heat storage and cold storage medium, and the heat transfer fluid is pressurized air (0.8MPa). This system structure has the advantages of high safety and low cost.

[0131] like Figure 2 The figure shows a schematic diagram of the pre-cooling unit structure, which includes a staged lithium bromide refrigeration unit 1031, a first pre-cooler 1032, and a second pre-cooler 1033. Heat from the first pre-cooler 1032 is absorbed by the lithium bromide refrigeration unit 1031, resulting in a hot air inlet temperature of 155°C. Based on the cooling characteristics of lithium bromide refrigeration units, a gradient of 20°C is used. Three different unit types are selected to maximize the cooling effect: double-effect absorption refrigeration, evaporative absorption heat exchange, and single-effect absorption refrigeration. After matching the cooling and heat, the cooling capacity generated by the units is just enough to reduce the air temperature to 28°C via the second pre-cooler, the same as the temperature entering the air liquefaction unit.

[0132] Table 1 shows the parameters of each key point of system operation, and Table 2 shows the overall performance of the system operation.

[0133] Table 1 Parameters of each operating point

[0134]

[0135]

[0136] Table 2 Overall system performance

[0137] parameter Numerical Power generation scale 50MW / 400MWh Net power input 316.41MW Net power output 50.07MW Liquefaction rate 59.92％ Cycle efficiency 63.30％

[0138] In summary, the present invention can simultaneously achieve heat supply and increase air power generation by rationally distributing the heat of air compression. Unlike traditional systems, the present invention efficiently distributes and utilizes the heat energy of air compression, and directly selects molten salt as the working fluid of the heat storage unit, which can obtain a wider heat storage temperature range and a higher heat storage density; the present invention integrates a lithium bromide refrigeration unit in the air compression unit, and uses the energy cascade by selecting a series connection form, efficiently absorbing the high-temperature air waste heat from the outlet of the first-stage compressor, and then converting it into cold energy for pre-cooling the gas about to enter the air purifier, thereby achieving effective energy utilization and improved process efficiency. Ultimately, the present invention can achieve efficiency improvement of the coupled lithium bromide unit of the high heat storage density liquid air energy storage system.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A high heat storage density liquid air energy storage system, characterized in that: It comprises an air compression unit (100), an air liquefaction unit (200), a liquid gasification unit (300), a cold storage unit (400), a heat storage unit (600), and an air expansion power generation unit (500); The first input end of the air compression unit (100) is used to input ambient air, the second input end of the air compression unit (100) is used to input electricity, the first output end of the air compression unit (100) is connected to the first input end of the air liquefaction unit (200), the second output end of the air compression unit (100) is connected to the first input end of the heat storage unit (600), and the third input end of the air compression unit (100) is connected to the first output end of the heat storage unit (600); the air liquefaction unit (200) is respectively connected to the liquid air liquefaction unit (300) and the cold storage unit (400), the liquid air liquefaction unit (300) is connected to the air expansion power generation unit (500), and the air expansion power generation unit (500) is connected to the heat storage unit (600); The air compression unit (100) is used to compress, purify and cool ambient air, and then expand and reduce the pressure to obtain liquid air, and the compression heat generated during the compression process is sequentially stored in the heat storage unit (600) for subsequent use; The air liquefaction unit (200) cools and expands the compressed air to obtain low-temperature liquid air, which is then stored in a liquid air storage tank; The liquid gasification unit (300) processes the obtained low-temperature liquid air through a low-temperature pump pressurization and an evaporator gasification process, and stores the cold energy generated in the evaporation gasification process in a cold storage unit; The cold storage unit (400) stores cold energy generated by gasification of liquid air in a cold storage packed bed, thereby providing cold energy for the air liquefaction unit; The heat storage unit (600) receives the high-quality compression heat transmitted by the air compression unit (100) to provide heat to the air expansion power generation unit, and the excess compression heat is used to provide heat to users; The air expansion power generation unit (500) is heated by the high-temperature molten salt of the heat storage unit and then expands to generate power; The air compression unit (100) comprises: a first compressor (101), wherein a first input end and a second input end of the first compressor (101) serve as a first input end and a second input end of the air compression unit (100), respectively; a first cooler (102), wherein a first input end of the first cooler (102) is connected to the output end of the first compressor (101), and a second input end of the first cooler (102) is connected to the heat storage unit (600); a pre-cooling unit (103), wherein the input end of the pre-cooling unit (103) is connected to the first output end of the first cooler (102); An air purifier (104), wherein an input end of the air purifier (104) is connected to an output end of the pre-cooling unit (103); a second compressor (105), wherein an input end of the second compressor (105) is connected to an output end of the air purifier (104); a second cooler (106), wherein a first input end of the second cooler (106) is connected to an output end of the second compressor (105); a third compressor (107), wherein an input end of the third compressor (107) is connected to a first output end of the second cooler (106); a third cooler (108), wherein a first input end of the third cooler (108) is connected to an output end of the third compressor (107); a fourth cooler (109), wherein a first input end of the fourth cooler (109) is connected to a first output end of the third cooler (108), and a second input end of the fourth cooler (109) is connected to a second output end of the heat storage unit (600); the second input end of the first cooler (102), the second input end of the second cooler (106), and the second input end of the third cooler (108) are connected in parallel to serve as a third input end of the air compression unit (100), and are connected to a first output end of the heat storage unit (600); the second output end of the first cooler (102), the second output end of the second cooler (106), and the second output end of the third cooler (108) are connected in parallel to serve as a second output end of the air compression unit (100), and are connected to a first input end of the heat storage unit (600); The precooling unit (103) comprises a staged lithium bromide refrigeration unit (1031), a first precooler (1032) and a second precooler (1033) connected in sequence, the staged lithium bromide refrigeration unit (1031) comprises a double-effect absorption refrigeration unit, an evaporative absorption heat exchanger and a single-effect absorption refrigeration unit, and the double-effect absorption refrigeration unit, the evaporative absorption heat exchanger and the single-effect absorption refrigeration unit are connected in series in sequence.

2. A high heat storage density liquid air energy storage system according to claim 1, characterized in that: The heat storage unit (600) comprises a molten salt cold tank (601), a first molten salt pump (602), a molten salt hot tank (603), a second molten salt pump (604), a first heater (605), a medium-temperature water storage tank (606), a first circulating water pump (607), a second heater (608), a low-temperature water storage tank (609) and a second circulating water pump (610); The output end of the molten salt cold tank (601) is connected to the input end of the first molten salt pump (602), the output end of the first molten salt pump (602) is connected to the third input end of the air compression unit (100), the input end of the molten salt hot tank (603) is connected to the second output end of the air compression unit (100), the output end of the molten salt hot tank (603) is connected to the input end of the second molten salt pump (604), the output end of the second molten salt pump (604) is connected to the first input end of the air expansion power generation unit (500), and the input end of the molten salt cold tank (601) is connected to the output end of the first heater (605); The input end of the medium-temperature water storage tank (606) is connected to the third output end of the air compression unit (100), the input end of the first circulating water pump (607) is connected to the output end of the medium-temperature water storage tank (606), the input end of the low-temperature water storage tank (609) is connected to the third output end of the air expansion power generation unit (500), the input end of the second circulating water pump (610) is connected to the output end of the low-temperature water storage tank (609); the input end of the low-temperature water storage tank (609) is connected to the output end of the second heater (608); The second input end of the air expansion power generation unit (500) is connected to the second output end of the heat storage unit (600), the first output end of the air expansion power generation unit (500) is connected to the second input end of the heat storage unit (600), and the second output end of the air expansion power generation unit (500) is used to output electricity.

3. The high heat storage density liquid air energy storage system according to claim 1, characterized in that: The air liquefaction unit (200) comprises an air separator (201), a liquefaction main heat exchanger (202), a low-temperature gas expander (203), a low-temperature liquid expander (204), a throttle valve (205), and a gas-liquid separator (206); The input end of the air separator (201) is connected to the first output end of the air compression unit (100), the first input end of the liquefied main heat exchanger (202) is connected to the first output end of the air separator (201), the second input end of the liquefied main heat exchanger (202) is connected to the second output end of the air separator (201), the third input end of the liquefied main heat exchanger (202) is connected to the second output end of the gas-liquid separator (206), and the fourth input end of the liquefied main heat exchanger (202) is connected to the cold storage unit (206). The first output end of the liquefaction main heat exchanger (202) is connected to the third input end of the low-temperature gas expander (203), the second output end of the liquefaction main heat exchanger (202) is connected to the input end of the low-temperature liquid expander (204), the third output end of the liquefaction main heat exchanger (202) is connected to the third input end of the air compression unit (100), and the fourth output end of the liquefaction main heat exchanger (202) is connected to the first input end of the cold storage unit (400); The output end of the low-temperature gas expander (203) is connected to the third input end of the liquefaction main heat exchanger (202), the output end of the low-temperature liquid expander (204) is connected to the input end of the throttle valve (205), and the output end of the throttle valve (205) is connected to the input end of the gas-liquid separator (206).

4. A high heat storage density liquid air energy storage system according to claim 3, characterized in that: The liquid air aeration unit (300) comprises a liquid air storage tank (301), a cryogenic pump (302) and an evaporator (303); the input end of the liquid air storage tank (301) is connected to the first output end of the gas-liquid separator (206), the output end of the liquid air storage tank (301) is connected to the input end of the cryogenic pump (302), the output end of the cryogenic pump (302) is connected to the first input end of the evaporator (303), the first output end of the evaporator (303) is connected to the air expansion power generation unit (500), the second input end of the evaporator (303) is connected to the second output end of the cold storage unit (400), and the first output end of the evaporator (303) serves as the first output end of the liquid air aeration unit (300).

5. A high heat storage density liquid air energy storage system according to claim 4, characterized in that: The cold storage unit (400) comprises a cold storage filled bed (401), a first circulation fan (402) and a second circulation fan (403); the input end of the first circulation fan (402) is connected to the second output end of the evaporator (303), the output end of the first circulation fan (402) is connected to the fourth input end of the liquefaction main heat exchanger (202), the input end of the second circulation fan (403) is connected to the fourth output end of the liquefaction main heat exchanger (202), and the output end of the second circulation fan (403) is connected to the second input end of the evaporator (303); The cold storage packed bed (401) is used to store the cold energy released by the liquid-to-air liquefaction unit (300) and transfer it to the air liquefaction unit (200).

6. The high heat storage density liquid air energy storage system according to claim 1, characterized in that: The air expansion power generation unit (500) comprises: An air preheater (501), wherein a first input end of the air preheater (501) serves as a first input end of the air expansion power generation unit (500), and the first input end of the air preheater (501) is connected to an output end of the liquid gasification unit (300); a first heater (502), wherein a first input end of the first heater (502) is connected to a first output end of the air preheater (501); a first expander (503), wherein an input end of the first expander (503) is connected to a first output end of the first heater (502); a second heater (504), wherein a first input end of the second heater (504) is connected to an output end of the first expander (503); a second expander (505), wherein an input end of the second expander (505) is connected to a first output end of the second heater (504); a third heater (506), wherein a first input end of the third heater (506) is connected to an output end of the second expander (505); a third expander (507), wherein an input end of the third expander (507) is connected to a first output end of the third heater (506); a fourth heater (508), wherein a first input end of the fourth heater (508) is connected to an output end of the third expander (507); a fourth expander (509), wherein the input end of the fourth expander (509) is connected to the first output end of the fourth heater (508); the first output end and the second output end of the fourth expander (509) serve as the second output end and the third output end of the air expansion power generation unit (500), respectively; The second input end of the first heater (502), the second input end of the second heater (504), the second input end of the third heater (506), and the second input end of the fourth heater (508) are connected in parallel as the second input end of the air expansion power generation unit (500) and connected to the second output end of the heat storage unit (600); the second output end of the first heater (502), the second output end of the second heater (504), the second output end of the third heater (506), and the second output end of the fourth heater (508) are connected in parallel as the first output end of the air expansion power generation unit (500) and connected to the second input end of the heat storage unit (600).

7. A high heat storage density liquid air energy storage method, the method is implemented based on the high heat storage density liquid air energy storage system according to any one of claims 1 to 6, characterized in that: The method comprises: Air compression liquefaction storage mode: ambient air is initially compressed by the first compressor (101), and the compressed air is cooled by the first cooler (102) and the pre-cooling unit (103) and then enters the air purifier (104). In the air purifier (104), the adsorbent removes moisture and carbon dioxide in the air, and then the air is further compressed to high pressure by the second compressor (105) and the third compressor (107); the high-grade compression heat generated during the air compression process is recovered by molten salt and stored in the heat storage unit (600); after the compressed high-temperature air is cooled, the graded lithium bromide refrigeration unit provides cooling capacity, and the air is further cooled to a low temperature by the liquefaction main heat exchanger (202), and then enters the low-temperature gas expander (203) and the low-temperature liquid expander (204) for expansion and pressure reduction, and part of the air is liquefied; the liquefied air is separated into liquid air by the throttle valve (205) and the gas-liquid separator (206), and the liquid air is stored in the liquid air storage tank (301); Air expansion power generation mode: the liquid air output from the liquid air storage tank (301) is pressurized to a high pressure by a cryogenic pump (302), and then enters the evaporator (303) to undergo a liquid-gas phase change process. The cold energy generated by the gasification is stored in the cold storage unit (400) through the pressurized fluid; the gasified high-pressure air enters the air expansion power generation unit (500), and is expanded and performs work through the multi-stage expander; during the air expansion power generation process, the heat storage unit (600) releases heat energy to heat the air before entering the expanders at each stage, which is used to maintain the operation of the expansion power generation unit; Waste heat heating mode: open the bypass pipeline of the first heater (605), open the second molten salt pump (604), the hot molten salt in the molten salt hot tank (603) flows to the first heater (605) through the pipeline, the remaining compression heat stored in the heat storage unit (600) uses the molten salt as a heat carrier to exchange heat with the heating water, thereby providing heat energy to the user through the heater, and the molten salt finally returns to the molten salt cold tank (601); open the bypass pipeline of the second heater (608), open the second circulating water pump (610), the pressurized hot water in the medium-temperature water storage tank (606) flows to the second heater (608) through the pipeline, the remaining compression heat stored in the heat storage unit (600) uses the pressurized water as a heat carrier to exchange heat with the heating water, thereby providing heat energy to the user through the heater, and the pressurized water finally returns to the low-temperature water storage tank (609); finally, the waste heat is recycled and utilized, and the overall energy utilization efficiency of the system is improved.

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