Photo-thermal coupling high-temperature compression supercritical liquid air energy storage system and method

Abstract

The invention discloses a photo-thermal coupling high-temperature compression supercritical liquid air energy storage system. The system comprises an air compression and purification unit, a liquefaction heat exchange unit, a supercritical liquid air storage unit, a cold storage unit, a heat storage unit, a solar heat collection unit and an air expansion power generation unit. During energy storage, air is liquefied after high-pressure-ratio high-temperature compression and is directly stored in a supercritical pressure state, compression heat is guided into the heat storage unit, and the heat energy grade is increased through the solar heat collection unit; during energy release, supercritical liquid air is directly output without a pump, high-grade heat energy is used for heating temperature rise and multi-stage rethermal expansion acting, and cold energy is recycled in a closed-loop mode. A traditional throttling valve and a traditional pressurizing pump are abandoned through supercritical high-pressure storage, throttling and pressurizing losses are eliminated, and the liquefaction rate is greatly increased; and the heat source grade is remarkably improved through deep coupling of photo-thermal and compression heat, and the generating capacity and the overall circulation efficiency of the system are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of liquid air energy storage technology, and particularly relates to a photothermal coupled high-temperature compression supercritical liquid air energy storage system and method. Background Technology

[0002] With the transformation of the global energy structure and the advancement of "dual-carbon" goals, large-scale, high-efficiency energy storage technologies have become crucial for supporting the large-scale integration of renewable energy. Liquid air energy storage (LAES), as an energy storage technology that is not dependent on specific geographical conditions, has high energy density, and low environmental impact, has attracted widespread attention. However, traditional LAES technology mainly suffers from the following technical bottlenecks:

[0003] (1) Low energy storage density and efficiency: Traditional LAES typically use atmospheric or near-atmospheric pressure (far below the critical pressure of air) to store liquid air. This low-pressure storage method not only results in low energy density of the storage medium, but also requires a liquid pump that consumes a lot of energy to pressurize the system when switching to high-pressure circulation, accompanied by significant throttling losses (energy losses), which seriously restricts the overall energy storage efficiency of the system. The circulation efficiency is usually only about 40%-50%.

[0004] (2) Low thermal energy utilization: In the traditional LAES energy release process, liquid air is throttled and depressurized before it absorbs heat, vaporizes, and expands to do work. At this time, the working fluid temperature is relatively low. Even if the low-grade waste heat generated during the air compression process is recovered, it is difficult to significantly increase the expansion work, resulting in insufficient power generation. Especially when using low-grade industrial waste heat or when sufficient high-temperature heat sources cannot be obtained, the system performance is limited.

[0005] These issues collectively make it difficult for traditional LAES technology to meet the needs of large-scale deployment in terms of both cost-effectiveness and competitiveness. Summary of the Invention

[0006] This invention aims to solve the key technical problems existing in current liquid air energy storage technology, such as low energy storage density, low circulation efficiency, insufficient energy recovery and utilization, especially high power consumption of booster pumps, serious throttling losses, and poor utilization of low-grade heat sources, in order to achieve a supercritical liquid air energy storage system with higher energy utilization efficiency and better economy.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a photothermal coupled high-temperature compressed supercritical liquid air energy storage system, comprising:

[0008] The air compression and purification unit is used to compress and purify outside air before outputting it to the liquefaction heat exchange unit.

[0009] A liquefaction heat exchange unit is used to cool compressed and purified air and output liquid air to a liquid air storage unit, wherein the liquefaction heat exchange unit includes a distributor and a cold box;

[0010] A liquid air storage unit is used to store liquid air at supercritical pressure and output liquid air to an air expansion power generation unit during the energy release phase.

[0011] The cold storage unit is connected to the liquefaction heat exchange unit and the air expansion power generation unit, and is used to receive the low-temperature working fluid cold energy generated during the energy release process of the air expansion power generation unit and send it back to the liquefaction heat exchange unit.

[0012] The heat storage unit is connected to the air compression and purification unit and the air expansion power generation unit, and is used to receive the heat generated during the compression process of the air compression and purification unit and supply heat to the air expansion power generation unit.

[0013] The solar collector unit is connected to the thermal storage unit and is used to heat the heat carrier from the thermal storage unit with solar energy before sending it back to the thermal storage unit.

[0014] The air expansion power generation unit is connected to the liquid air storage unit, the cold storage unit, and the heat storage unit, and is used to make the liquid air from the liquid air storage unit successively undergo heat absorption and vaporization, heating and staged expansion to do work.

[0015] The system forms a closed-loop energy management system by coupling a high-temperature compression heat recovery circuit and a solar thermal collection circuit with a low-temperature cold circuit.

[0016] Preferably, the output pressure of the liquid air storage unit is higher than the critical pressure of liquid air, so that the liquid air is kept in a supercritical pressure state after being output from the liquid air storage unit and before entering the air expansion power generation unit.

[0017] Preferably, the air compression and purification unit includes a multi-stage compressor arranged in series, a cooler disposed between each stage of the compressor, and an air purification device. The outlets of each stage of the compressor are respectively connected to the heat storage unit through pipelines to introduce the compression heat of different temperature levels into the heat storage unit for graded heat storage.

[0018] Preferably, the thermal storage unit includes a high-temperature thermal storage branch and a medium-temperature thermal storage branch. The high-temperature thermal storage branch is connected to the solar thermal collector unit, and the medium-temperature thermal storage branch is connected to the preheating stage in the air expansion power generation unit, so as to provide heat sources of different temperature levels for different expansion stages.

[0019] Preferably, the cold storage unit is located between the air expansion power generation unit and the liquefaction heat exchange unit. The low-temperature gaseous working fluid discharged from the air expansion power generation unit first enters the cold storage unit for cold storage, and then the cold storage unit releases the cold energy to the liquefaction heat exchange unit.

[0020] Preferably, the air expansion power generation unit includes an evaporator, a preheater, a multi-stage heater, and a multi-stage air turbine. Liquid air from the liquid air storage unit is vaporized by the evaporator and then passes through multiple heating stages and expansion stages arranged alternately to form a staged heating and staged expansion process.

[0021] Preferably, at least one stage of the multi-stage heater is connected to the high-temperature heat storage branch, and at least another stage is connected to the medium-temperature heat storage branch, so that heat sources of different temperature levels are connected to different expansion stages respectively.

[0022] Preferably, the solar thermal collector unit includes a trough solar collector and a heat carrier circulation loop, which is connected to the thermal storage unit for storing thermal energy.

[0023] The present invention also provides a method for energy storage and release using the system described in any one of the above claims, comprising:

[0024] During the energy storage phase, outside air is compressed, cooled, and purified before being sent to the liquefaction heat exchange unit for liquefaction, and the resulting liquid air is stored in the liquid air storage unit under supercritical pressure.

[0025] During the energy storage phase, the heat generated during air compression is introduced into the thermal storage unit, and the heat carrier in the thermal storage unit is heated by entering the solar collector unit.

[0026] During the energy release phase, the liquid air in the liquid air storage unit is output to the air expansion power generation unit, and mechanical energy is output after vaporization, preheating, multi-stage heating and multi-stage expansion;

[0027] During the energy release phase, the expanded cryogenic working fluid is introduced into the cold storage unit to store the cold energy, and the cold energy in the cold storage unit is sent back to the liquefaction heat exchange unit to participate in the subsequent liquefaction process.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. This invention utilizes supercritical pressure to liquefy and store liquid air, fundamentally solving the problems of high energy consumption and low efficiency associated with traditional low-pressure storage technologies. In the energy storage liquefaction stage, the traditional throttling and pressure-reducing valve is eliminated, avoiding severe cold loss caused by the throttling process, achieving an extremely high air liquefaction rate and significantly reducing the power consumption required for air liquefaction. In the energy release and power generation stage, since the working fluid output from the liquid air tank already possesses supercritical high-pressure potential energy, the system does not require a high-energy-consuming cryogenic liquid pressurization pump, directly eliminating the pressurization power consumption in traditional systems. This zero-pressurization pump power consumption and supercritical process design without throttling losses greatly simplifies the system structure and effectively overcomes the technical bottleneck of wasted energy in existing technologies.

[0030] 2. This invention, by eliminating cold-end losses, deeply couples high-pressure-ratio, high-temperature compression with solar thermal collection technology, achieving a leap in heat source quality and overall system efficiency. The system first obtains high-grade, high-temperature compression heat through high-pressure-ratio compression for initial heat storage. Then, it utilizes solar thermal collection cycles to reheat the high-temperature molten salt, achieving a significant "grade enhancement" of the thermal energy. This greatly improves the quality of the heat source, providing ample multi-stage reheat energy for the room-temperature supercritical fluid during the energy release phase, significantly enhancing the work capacity of the air turbine and the system's total power generation. Through the efficient synergy of supercritical high-pressure lossless release and deep work by the high-grade heat source, this invention successfully overcomes the limitation of traditional systems being constrained by low-grade heat sources, resulting in insufficient power generation. This allows the overall energy storage system's cycle power generation efficiency to exceed 70%, achieving a comprehensive improvement in system energy density and economic efficiency. Attached Figure Description

[0031] Figure 1 A schematic diagram of a supercritical liquid air energy storage system coupled with high-temperature compression and solar thermal collection is provided in an embodiment of the present invention.

[0032] In the picture:

[0033] 100 Air compression and purification unit, 101 First compressor, 102 First cooler, 103 Second cooler, 104 Molecular sieve, 105 First three-way valve, 106 Second compressor, 107 Third cooler, 108 Fourth cooler, 109 Second three-way valve, 110 Third three-way valve, 111 Fourth three-way valve; 200 Flow divider, 300 Cold box, 301 Air cooler, 302 Refrigeration expander; 400 Liquid air tank, 500 Cold storage unit, 501 Cold storage packed bed, 502 Sixth three-way valve, 503 Seventh three-way valve Valve; 600 Air expansion power generation unit, 601 Evaporator, 602 Preheater, 603 First heater, 604 First air turbine, 605 Second heater, 606 Second air turbine, 607 Third heater, 608 Third air turbine, 609 Fourth heater, 610 Fourth air turbine; 700 Thermal storage unit, 701 Hot molten salt tank, 702 Cold molten salt tank, 703 Hot water tank, 704 Cold water tank; 800 Solar collector unit, 801 Parabolic trough solar collector, 802 Molten salt pump, 803 Fifth heater. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings, so that those skilled in the art can better understand the advantages and features of the present invention, thereby making a clearer definition of the scope of protection of the present invention. The embodiments described in this invention are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0036] This application provides a photothermal coupled high-temperature compressed supercritical liquid air energy storage system and method. Its core technical concept lies in:

[0037] On the one hand, by increasing the liquid air storage pressure to a supercritical state (about 100 bar), the booster pump that must be configured due to low-pressure storage in traditional technologies is avoided, as well as the additional power consumption and throttling losses caused by it. This achieves 100% liquefaction rate and significantly reduces the power consumption of the liquefaction process.

[0038] On the other hand, the high-pressure-ratio, high-temperature compression heat generated during air compression is combined with solar thermal collection technology to "elevate the grade" of the heat storage medium (such as molten salt), forming a high-temperature heat source of up to 350°C. This provides sufficient high-grade heat energy for air expansion power generation in the energy release stage, thereby supporting the system to achieve a cycle efficiency of up to 70.03%.

[0039] Through the synergistic effect of supercritical high-pressure storage at the "cold end," high-temperature coupling at the "hot end," and grade enhancement, this invention effectively overcomes the limitations of traditional LAES systems and significantly improves the system's energy density, cycle efficiency, and economy.

[0040] The following describes the structural composition, workflow, and core control logic of the present invention in detail through multiple embodiments.

[0041] Example 1

[0042] This invention provides a supercritical liquid air energy storage system coupled with high-temperature compression and solar thermal collection, such as... Figure 1As shown, the system mainly consists of eight core units: an air compression and purification unit 100, a liquid air tank 400, a cold storage unit 500, an air expansion power generation unit 600, a heat storage unit 700, and a solar thermal collector unit 800. The liquid heat exchange unit includes a distributor 200 and a cold box 300.

[0043] The structural connection is as follows: First, the air compression and purification unit 100 includes a first compressor 101, a first cooler 102, a second cooler 103, a molecular sieve 104, a first three-way valve 105, a second compressor 106, a third cooler 107, a fourth cooler 108, a second three-way valve 109, a third three-way valve 110, a fourth three-way valve 111, and a fifth three-way valve 112.

[0044] The first input terminal of the air compression and purification unit 100, i.e. the input terminal of the first compressor 101, is used to input ambient air. The output terminal of the first compressor 101 is connected to the first input terminal of the first cooler 102. The first output terminal of the first cooler 102 is connected to the first input terminal of the second cooler 103. The first output terminal of the second cooler 103 is connected to the input terminal of the molecular sieve 104. The output terminal of the molecular sieve 104 is connected to the first port of the first three-way valve 105. The second port of the first three-way valve 105 serves as the fourth input terminal of the air compression and purification unit 100 and is connected to the first output terminal of the cold box 300. The third port of the first three-way valve 105 is connected to the input terminal of the second compressor 106. The output terminal of the second compressor 106 is connected to the first input terminal of the third cooler 107. The first output terminal of the third cooler 107 is connected to the first input terminal of the fourth cooler 108. The first output terminal of the fourth cooler 108 serves as the first output terminal of the air compression and purification unit 100 and is connected to the first input terminal of the distributor 200.

[0045] The second output end of the first cooler 102 is connected to the first port of the second three-way valve 109, the second port of the second three-way valve 109 is connected to the second output end of the third cooler 107, and the third port of the second three-way valve 109 is connected to the input end of the solar thermal collector unit 800 as the second output end of the air compression and purification unit 100.

[0046] The second input terminal of the first cooler 102 is connected to the first port of the third three-way valve 110, the third port of the third three-way valve 110 is connected to the second input terminal of the third cooler 107, and the second port of the third three-way valve 110 is connected to the second output terminal of the heat storage unit 700 as the second input terminal of the air compression and purification unit 100.

[0047] The second output terminal of the second cooler 103 is connected to the first port of the fourth three-way valve 111, the third port of the fourth three-way valve 111 is connected to the second output terminal of the fourth cooler 108, and the second port of the fourth three-way valve 111 is connected to the third input terminal of the heat storage unit 700 as the third output terminal of the air compression and purification unit 100.

[0048] The second input terminal of the fourth cooler 108 is connected to the third port of the fifth three-way valve 112, the second port of the fifth three-way valve 112 is connected to the second input terminal of the second cooler 103, and the first port of the fifth three-way valve 112 is connected to the fourth output terminal of the heat storage unit 700 as the third input terminal of the air compression and purification unit 100.

[0049] The cold box 300 includes an air cooler 301 and a refrigeration expander 302, with the specific connection relationship as follows:

[0050] The first input terminal of the air cooler 301 is connected to the first output terminal of the splitter 200 as the first input terminal of the cold box 300. The second input terminal of the air cooler 301 is connected to the second output terminal of the splitter 200 as the second input terminal of the cold box 300. The third input terminal of the air cooler 301 is connected to the first output terminal of the cold storage unit 500 as the third input terminal of the cold box 300. The second output terminal of the air cooler 301 is connected to the input terminal of the liquid air tank 400 as the second output terminal of the cold box 300. The third output terminal of the air cooler 301 is connected to the first input terminal of the cold storage unit 500 as the third output terminal of the cold box 300. The fourth output terminal of the air cooler 301 is connected to the fourth input terminal of the air compression and purification unit 100, which is the second port of the first three-way valve 105.

[0051] The input end of the refrigeration expander 302 is connected to the first output end of the air cooler 301, and the output end of the refrigeration expander 302 is connected to the fourth input end of the air cooler 301.

[0052] The cold storage unit 500 includes a cold storage packed bed 501, a sixth three-way valve 502, and a seventh three-way valve 503, with the specific connection relationships as follows:

[0053] The cold storage filling bed 501 has a left port and a right port. The left port of the cold storage filling bed 501 is connected to the second port of the sixth three-way valve 502, and the right port of the cold storage filling bed 501 is connected to the second port of the seventh three-way valve 503.

[0054] The first port of the sixth three-way valve 502 is connected to the third output port of the cold box 300, i.e. the third output port of the air cooler 301, as the first input port of the cold storage unit 500. The third port of the sixth three-way valve 502 is connected to the second input port of the air expansion power generation unit 600 as the second output port of the cold storage unit 500.

[0055] The first port of the seventh three-way valve 503 is connected to the first output of the air expansion power generation unit 600 as the second input of the cold storage unit 500, and the third port of the seventh three-way valve 503 is connected to the third input of the cold box 300 as the first output of the cold storage unit 500.

[0056] The air expansion power generation unit 600 includes an evaporator 601, a preheater 602, a first heater 603, a first air turbine 604, a second heater 605, a second air turbine 606, a third heater 607, a third air turbine 608, a fourth heater 609, and a fourth air turbine 610.

[0057] The first input terminal of the evaporator 601 is connected to the second output terminal of the cold storage unit 500 as the second input terminal of the air expansion power generation unit 600, the first output terminal of the evaporator 601 is connected to the second input terminal of the cold storage unit 500 as the first output terminal of the air expansion power generation unit 600, and the second input terminal of the evaporator 601 is connected to the output terminal of the liquid air tank 400 as the first input terminal of the air expansion power generation unit 600.

[0058] The second input terminal of preheater 602 is connected to the second output terminal of evaporator 601. The first input terminal of preheater 602 serves as the third input terminal of air expansion power generation unit 600 and is connected to the third output terminal of heat storage unit 700. The first output terminal of preheater 602 serves as the second output terminal of air expansion power generation unit 600 and is connected to the fourth input terminal of heat storage unit 700. The second output terminal of preheater 602 is connected to the second input terminal of first heater 603. The second output terminal of first heater 603 is connected to the input terminal of first air turbine 604. The output terminal of first air turbine 604 is connected to the second input terminal of second heater 605. The second output terminal of second heater 605 is connected to the input terminal of second air turbine 606. The output terminal of second air turbine 606 is connected to the second input terminal of third heater 607. The second output terminal of the device 607 is connected to the input terminal of the third air turbine 608. The output terminal of the third air turbine 608 is connected to the second input terminal of the fourth heater 609. The second output terminal of the fourth heater 609 is connected to the input terminal of the fourth air turbine 610. The first input terminals of the first heater 603, the second heater 605, the third heater 607, and the fourth heater 609 are connected in parallel as the fourth input terminal of the air expansion power generation unit 600 and connected to the first output terminal of the heat storage unit 700. The first output terminals of the first heater 603, the second heater 605, the third heater 607, and the fourth heater 609 are connected in parallel as the third output terminal of the air expansion power generation unit 600 and connected to the second input terminal of the heat storage unit 700.

[0059] The thermal storage unit 700 includes a hot molten salt tank 701, a cold molten salt tank 702, a hot water tank 703, and a cold water tank 704, with the following specific structure:

[0060] The input end of the hot molten salt tank 701 is connected to the output end of the solar thermal collector unit 800 as the first input end of the thermal storage unit 700, and the first output end of the hot molten salt tank 701 is connected to the fourth input end of the air expansion power generation unit 600 as the first output end of the thermal storage unit 700.

[0061] The input end of the cold molten salt tank 702 is connected to the third output end of the air expansion power generation unit 600 as the second input end of the heat storage unit 700, and the output end of the cold molten salt tank 702 is connected to the second input end of the air compression purification unit 100 as the second output end of the heat storage unit 700.

[0062] Hot water tank 703, the input end of hot water tank 703 is connected to the third input end of heat storage unit 700 and the third output end of air compression and purification unit 100, and the output end of hot water tank 703 is connected to the third input end of air expansion power generation unit 600 as the third output end of heat storage unit 700.

[0063] The cold water tank 704 has its input end connected to the second output end of the air expansion power generation unit 600 as the fourth input end of the heat storage unit 700, and its output end connected to the third input end of the air compression and purification unit 100 as the fourth output end of the heat storage unit 700.

[0064] The solar thermal collector unit 800 includes a parabolic trough solar collector 801, a fifth heater 803, and a molten salt pump 802, with the following specific structure:

[0065] The first input terminal of the fifth heater 803 serves as the input terminal of the solar collector unit 800 and is connected to the second output terminal of the air compression and purification unit 100. The first output terminal of the fifth heater 803 serves as the output terminal of the solar collector unit 800 and is connected to the first input terminal of the heat storage unit 700 (i.e., the input terminal of the molten salt tank 701). The second output terminal of the fifth heater 803 is connected to the input terminal of the molten salt pump 802, the output terminal of the molten salt pump 802 is connected to the input terminal of the trough solar collector 801, and the output terminal of the trough solar collector 801 is connected to the second input terminal of the fifth heater 803.

[0066] Working Principle: In the airflow direction: The first input terminal of the air compression and purification unit 100 (i.e., the input terminal of the first compressor 101) is used to input ambient air. The air passes through the first compressor 101, the first cooler 102, and the second cooler 103 in sequence for cooling, and then enters the molecular sieve 104 to remove impurities. The output terminal of the molecular sieve 104 is connected to the first port of the first three-way valve 105. Specifically, the second port of the first three-way valve 105 serves as the "fourth input terminal" of the unit 100 and is connected to the first output terminal of the cold box 300 (for receiving the return low-pressure cold air after the cold box has expanded and cooled). After the fresh air and the return cold air merge at the first three-way valve 105, they enter the second compressor 106 from the third port for high-pressure ratio compression, and then pass through the third cooler 107 and the fourth cooler 108 in sequence. The first output terminal of the fourth cooler 108 serves as the "first output terminal" of the unit 100 and is connected to the first input terminal of the distributor 200 to output high-pressure air. In the heat recovery flow direction: The fluid is distributed to the first cooler 102 and the third cooler 107 to absorb the heat of compression through the third three-way valve 110 (which connects to the cold medium of the heat storage unit 700); the high-temperature fluid after absorbing heat is collected through the second three-way valve 109 and directly output to the input end of the solar collector unit 800 through its third port (which serves as the "second output end" of the unit 100). At the same time, another cooling circuit is constructed through the fifth three-way valve 112 and the fourth three-way valve 111, connecting the second cooler 103, the fourth cooler 108 and the heat storage unit 700 to complete the heat exchange between waste heat and the ambient temperature water circuit.

[0067] Energy Storage Phase Operation (Mixed Compression, Heat Recovery, and Supercritical Liquefaction): During periods of low electricity demand, the system initiates the energy storage process. The specific thermodynamic process is as follows: Ambient air is initially compressed by the first compressor 101, and the resulting intermediate-temperature heat of compression is recovered by the first cooler 102. It is then cooled to ambient temperature by the second cooler 103 and purified by the molecular sieve 104 (to prevent subsequent cryogenic freezing). Reflux Mixing and High-Pressure-Ratio Compression: The purified air is combined with extremely low-temperature, low-pressure reflux cold air from the first output end of the cold box 300 at the first three-way valve 105. The mixed airflow enters the second compressor 106 for high-pressure-ratio compression. Due to the extremely high pressure ratio, the air is compressed to approximately 100 bar (as shown in node 7 of Table 1), while simultaneously generating extremely high-grade heat of compression (approximately 300°C or higher). The extremely high-temperature compressed air enters the third cooler 107, where it transfers its high-temperature heat to the heat transfer fluid. The heated fluid is then sent directly to the solar collector unit 800 via the second three-way valve 109. Subsequently, the high-pressure air is further cooled to room temperature via the fourth cooler 108 (as shown in node 9 of Table 1, 25°C, 99.8 bar).

[0068] Supercritical liquefaction cycle: High-pressure, room-temperature air from the first output of the compression and purification unit 100 is divided into two streams by the splitter 200. One stream acts as an expansion refrigerant in the cold box 300 to perform work and cool the air (the resulting low-pressure cold air is eventually discharged from the first output of the cold box 300 and flows back to the aforementioned valve 105 to achieve circulation); the other main stream is deeply cooled to -143°C (node ​​15) within the cold box 300 while maintaining an ultra-high pressure close to 100 bar (e.g., 99.6 bar). Technical breakthrough: At approximately 100 bar, air far exceeds its critical pressure (approximately 37.9 bar). Therefore, when the air is cooled in the cold box, it no longer undergoes a gas-liquid two-phase transition zone but directly transforms into a high-density, high-flow-rate "supercritical fluid." This supercritical fluid is directly stored in the liquid air tank 400. This design completely eliminates the throttling and pressure-reducing valves of traditional low-pressure systems, achieving highly efficient liquefaction energy storage without throttling cooling loss.

[0069] Thermal Energy Grade Enhancement (Deep Solar Coupling): During the daytime, the solar collector unit 800, composed of equipment such as a parabolic trough solar collector, receives medium-to-high temperature fluid from the compression and purification unit 100 (i.e., the output of the second three-way valve 109). The influx of solar energy further "grades" the fluid (e.g., heats it to 350°C), and then stores it in the high-temperature molten salt tank of the thermal storage unit 700. This process seamlessly integrates compressed waste heat with solar thermal energy, reserving a sufficient high-quality heat source for the energy release phase.

[0070] Energy Release Phase (Pump-Free Energy Release and Multi-Stage Reheat Expansion): During peak electricity consumption, the system discharges to perform work: pump-free release and cold energy recovery: Supercritical high-pressure air stored in liquid air tank 400 flows out and enters the evaporator of expansion power generation unit 600. During this process, the supercritical fluid absorbs heat and returns to its normal temperature gas state. Its extremely low cold energy (-140℃ level) is transferred and sealed in cold storage unit 500 for use in the next energy storage cycle. Technical breakthrough: Traditional liquid air energy storage and release must rely on a power-consuming liquid pump to pressurize the normal pressure liquid to high pressure; however, this system uses supercritical high-pressure direct storage, and the fluid itself has the potential energy to do work at hundreds of atmospheres, which can be directly released to perform work, achieving "zero booster pump power consumption".

[0071] Multi-stage expansion power generation: High-pressure gas restored to room temperature is first preheated using recycled medium-temperature water, and then undergoes deep heat exchange with high-temperature molten salt in the thermal storage unit 700 (heated to approximately 340°C) after being elevated by solar energy. The extremely high temperature and pressure air then enters the multi-stage air turbine unit to expand and generate electricity. Because a sufficient high-grade heat source supports the multi-stage "reheat" expansion, the turbine's work capacity is greatly enhanced, resulting in a qualitative leap in the system's overall cycle efficiency (RTE).

[0072] In this embodiment, the system compresses air to approximately 100 bar using a high pressure ratio and stores it in a liquid air tank at an ultra-high pressure of approximately 99.6 bar. Simultaneously, it recovers the heat of compression to heat the molten salt to 295.4°C, which is then further heated to 350°C by solar thermal collectors. The node parameters of the supercritical liquid air energy storage system coupled with high-temperature compression and solar thermal collection in this embodiment are shown in Table 1. The performance comparison with the traditional stand-alone liquid air energy storage system is shown in Table 2. The system's cycle efficiency can reach 70%, compared to 45.2% for the traditional stand-alone liquid air energy storage system, representing an improvement of 24.8%.

[0073] Table 1 System Node Parameter Table

[0074]

[0075]

[0076]

[0077] Table 2 System Performance Comparison Table

[0078] In summary, this invention, during off-peak electricity demand periods, compresses air to a supercritical state using a high pressure ratio, then cools it to produce liquid air. Electrical energy is stored in the form of supercritical liquid air, while molten salt is used to recover the high-temperature heat of compression generated during the compression process. Solar thermal collectors are used to further heat the molten salt, increasing the power generation from air expansion. During peak electricity demand periods, the supercritical liquid air releases cold energy through a liquid-gas phase change, is then heated by the molten salt, and finally enters an air turbine for power generation. This invention, by storing liquid air under high pressure, can significantly improve the air liquefaction rate and avoid the throttling and pressurization losses caused by traditional low-pressure storage. Furthermore, this invention obtains high-temperature heat of compression through high-pressure compression and further improves the heat energy quality through solar energy, significantly increasing the power generation from air expansion. By combining supercritical storage and high-temperature heat energy, this invention can significantly improve the system's power generation efficiency.

[0079] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

[0080] The descriptions and practices disclosed in this invention are readily apparent and understandable to those skilled in the art, and various modifications and refinements can be made without departing from the principles of this invention. Therefore, any modifications or improvements made without departing from the spirit of this invention should also be considered within the scope of protection of this invention.

Claims

1. A photothermal coupled high-temperature compression supercritical liquid air energy storage system, characterized in that, include: An air compression and purification unit (100) is used to compress and purify outside air before outputting it to a liquefaction heat exchange unit. A liquefaction heat exchange unit is used to cool compressed and purified air and output liquid air to a liquid air storage unit (400), wherein the liquefaction heat exchange unit includes a distributor (200) and a cold box (300). A liquid air storage unit (400) is used to store liquid air in a supercritical pressure state and output liquid air to an air expansion power generation unit (600) during the energy release phase. The cold storage unit (500) is connected to the liquefaction heat exchange unit and the air expansion power generation unit (600) to receive the low-temperature working fluid cold energy generated during the energy release process of the air expansion power generation unit (600) and send it back to the liquefaction heat exchange unit. The heat storage unit (700) is connected to the air compression and purification unit (100) and the air expansion power generation unit (600) to receive the heat generated during the compression process of the air compression and purification unit (100) and to supply heat to the air expansion power generation unit (600); The solar collector unit (800) is connected to the thermal storage unit (700) and is used to heat the heat carrier from the thermal storage unit with solar energy and then send it back to the thermal storage unit (700). The air expansion power generation unit (600) is connected to the liquid air storage unit (400), the cold storage unit (500) and the heat storage unit (700) to enable the liquid air from the liquid air storage unit (400) to perform work by absorbing heat and vaporizing, being heated and expanding in stages. The system forms a closed-loop energy management system by coupling a high-temperature compression heat recovery circuit and a solar thermal collection circuit with a low-temperature cold circuit.

2. The supercritical liquid air energy storage system as described in claim 1, characterized in that, The output pressure of the liquid air storage unit (400) is higher than the critical pressure of liquid air, so that the liquid air is kept in a supercritical pressure state after being output from the liquid air storage unit (400) and before entering the air expansion power generation unit (600).

3. The supercritical liquid air energy storage system as described in claim 1, characterized in that, The air compression and purification unit (100) includes a multi-stage compressor arranged in series, a cooler and an air purification device arranged between each stage of the compressor. The outlets of each stage of the compressor are connected to the heat storage unit (700) through pipelines to introduce the heat of compression at different temperature levels into the heat storage unit (700) for graded heat storage.

4. The supercritical liquid air energy storage system as described in claim 1, characterized in that, The thermal storage unit (700) includes a high-temperature thermal storage branch and a medium-temperature thermal storage branch. The high-temperature thermal storage branch is connected to the solar thermal collector unit, and the medium-temperature thermal storage branch is connected to the preheating stage in the air expansion power generation unit (600) to provide heat sources of different temperature levels for different expansion stages.

5. The supercritical liquid air energy storage system as described in claim 1, characterized in that, The cold storage unit (500) is located between the air expansion power generation unit (600) and the liquefaction heat exchange unit. The low-temperature gaseous working fluid discharged by the air expansion power generation unit (600) first enters the cold storage unit (500) for cold storage, and then the cold storage unit (500) releases the cold energy to the liquefaction heat exchange unit.

6. The supercritical liquid air energy storage system as described in claim 1, characterized in that, The air expansion power generation unit (600) includes an evaporator, a preheater, a multi-stage heater, and a multi-stage air turbine. Liquid air from the liquid air storage unit (400) is vaporized by the evaporator and then passes through multiple heating stages and expansion stages arranged alternately to form a staged heating and staged expansion process.

7. The supercritical liquid air energy storage system as described in claim 6, characterized in that, At least one stage of the multi-stage heater is connected to the high-temperature heat storage branch, and at least another stage is connected to the medium-temperature heat storage branch, so that heat sources of different temperature levels are connected to different expansion stages respectively.

8. The supercritical liquid air energy storage system as described in claim 1, characterized in that, The solar thermal collector unit (800) includes a trough solar collector (801) and a heat carrier circulation loop, which is connected to the thermal storage unit (700) for storing thermal energy.

9. A method for energy storage and release using the system according to any one of claims 1 to 8, characterized in that, include: During the energy storage phase, outside air is compressed, cooled and purified and then sent to the liquefaction heat exchange unit for liquefaction, and the resulting liquid air is stored in the liquid air storage unit (400) under supercritical pressure. During the energy storage stage, the heat generated during air compression is introduced into the thermal storage unit, and the heat carrier in the thermal storage unit is introduced into the solar collector unit (800) for heating. During the energy release phase, the liquid air in the liquid air storage unit (400) is output to the air expansion power generation unit (600), and mechanical energy is output after vaporization, preheating, multi-stage heating and multi-stage expansion; During the energy release phase, the expanded low-temperature working fluid is introduced into the cold storage unit (500) to store the cold energy, and the cold energy in the cold storage unit (500) is sent back to the liquefaction heat exchange unit to participate in the subsequent liquefaction process.

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