An air-CO2 heat exchange system for coupling liquid air and dry ice CO2 energy storage

Abstract

The application belongs to the technical field of energy conversion and energy storage, and discloses an air-CO2 heat exchange system coupling liquid air and dry ice CO2 energy storage. The system is coupled through an air passage and a CO2 loop, and high-efficiency heat exchange of the two is realized in the energy storage / discharging process. Main components include air and CO2 energy storage modules, discharging modules, cold accumulators, CO2 condensers, dry ice sublimation beds and CO2-air heat exchangers. When discharging, high-pressure CO2 after discharging enters the CO2 condenser, countercurrently exchanges heat with sprayed liquid air, and is condensed into dry ice for storage; after the liquid air is heated and gasified, it enters the air discharging module through the cold accumulator to expand and generate power. When storing energy, the stored dry ice exchanges heat with CO2 gas in the sublimation bed to sublimate, and low-temperature CO2 gas is generated, which exchanges heat with compressed high-pressure air in the CO2-air heat exchanger, so that the air is cooled and liquefied for storage, and the CO2 gas is heated and compressed into high-pressure CO2 for storage.

Description

Technical Field

[0001] This invention belongs to the field of energy storage technology, and specifically proposes an air-CO2 heat exchange system for coupling liquid air and dry ice CO2 energy storage. Background Technology

[0002] With the rapid growth of renewable energy installed capacity, the demand for large-scale, long-duration energy storage technologies in the power grid is becoming increasingly urgent. Among various physical energy storage technologies, compressed air energy storage (CAES) and carbon dioxide (CO2) energy storage have attracted much attention due to their advantages such as large storage capacity and long lifespan. However, both technologies still face their own technical bottlenecks in practical applications, especially in terms of energy storage density and system footprint.

[0003] The core of CO2 energy storage technology lies in high-pressure and low-pressure CO2 storage devices. For high-pressure CO2 storage, a liquid state is typically used, where high-pressure CO2 is condensed below its critical point, resulting in a gas-liquid two-phase state within the storage tank. This utilizes the density difference between the gas and liquid phases to increase energy storage density. For low-pressure CO2 storage, a flexible, atmospheric-pressure gas storage shed can be used to maintain a constant low pressure. However, due to the low density of CO2 at atmospheric pressure, the gas storage shed is enormous. While storing low-pressure CO2 in a liquid state can increase energy density, it requires cooling the CO2 to below approximately -30°C and maintaining this cryogenic environment. Furthermore, the pressure of low-pressure liquid CO2 exceeds 1 MPa, resulting in a relatively low operating pressure ratio for the energy storage system and a significant reduction in the work done per unit mass of CO2. Therefore, for low-pressure CO2 storage, a crucial issue that urgently needs to be addressed is how to significantly increase the CO2 energy storage density and improve the pressure ratio between the high and low pressure sides of the energy storage system, thereby effectively reducing the footprint of the storage device and the amount of CO2 used.

[0004] Currently, liquid air energy storage has received widespread attention from academia and industry. Liquid air energy storage involves processes such as air cooling, liquefaction, and evaporation, and possesses good low-temperature cold energy. However, currently, liquid air energy storage and CO2 energy storage systems are mostly developed independently. Although some research has attempted to couple different energy storage methods, existing solutions often fail to achieve deep integration and synergistic optimization of the cold and hot energy flows during the working fluid phase change process. This isolation between systems means that the land use challenges faced by CO2 energy storage and the cold energy demand challenges faced by liquid air energy storage cannot be fundamentally solved through improvements to their respective systems.

[0005] Therefore, there is an urgent need in this field for an innovative system coupling scheme that can efficiently and directly couple and exchange the huge latent heat and high-quality cold energy generated during the CO2 phase change (especially gas-solid sublimation / sublimation) process with the liquefaction / vaporization process of air, so as to realize the storage of low-pressure CO2 dry ice and fundamentally solve the industry pain points of low CO2 energy density and large footprint on the low-pressure side. Summary of the Invention

[0006] To address the industry pain points of low CO2 energy storage density and large footprint on the low-pressure side, this invention couples low-pressure CO2 with liquid air energy storage, providing an air-CO2 heat exchange system to significantly increase CO2 storage density. This system enables the cascaded, complementary, and efficient utilization of thermal energy during the phase change of the two working fluids (liquid / vaporization of air, gas / solid sublimation / sublimation of CO2), breaking through the efficiency bottleneck of single energy storage systems and improving the overall energy conversion efficiency and energy storage economy of the composite system.

[0007] The air-CO2 heat exchange system of the present invention includes an air passage and a CO2 loop.

[0008] The air passage includes an air energy storage module 23. The inlet of the air energy storage module 23 is connected to the atmosphere. The outlet of the air energy storage module 23 is connected to the hot side inlet of the CO2-air heat exchanger 14. The cold side outlet of the CO2-air heat exchanger 14 is connected to the hot side inlet of the cold accumulator 3. The cold side outlet of the cold accumulator 3 is connected to the inlet of the gas-liquid separator 7 via a throttle valve 6. The gas phase outlet of the gas-liquid separator 7 is connected to the return port of the cold accumulator 3. The liquid phase outlet of the gas-liquid separator 7 is connected to the inlet of the liquid air storage tank 9 via a valve 8. The outlet of the liquid air storage tank 9 is connected to the inlet of the cryogenic liquid air pump 11 via a valve 10. The outlet of the cryogenic liquid air pump 11 is connected to the upper inlet of the CO2 condenser 1. The gas phase outlet of the CO2 condenser 1 is connected to the inlet of the air compressor 4. The outlet of the air compressor 4 is connected to the inlet of the air release module 5. The liquid outlet of the CO2 condenser 1 is connected to the inlet of the liquid air pump 2. The outlet of the liquid air pump 2 is connected to the cold side inlet of the cold accumulator 3. The hot side outlet of the cold accumulator 3 is connected to the inlet of the air release module 5. The outlet of the air release module 5 is open to the atmosphere.

[0009] The CO2 loop includes a CO2 sublimator 1. The solid outlet of the CO2 sublimator 1 is connected to the inlet of the dry ice storage chamber 12. The outlet of the dry ice storage chamber 12 is connected to the dry ice sublimation bed 13 via a spiral conveyor. The gas outlet of the dry ice sublimation bed 13 is connected to the cold side inlet of the CO2-air heat exchanger 14. The hot side outlet of the CO2-air heat exchanger 14 is connected to the inlet of the CO2 buffer tank 16 via valve 15. The return outlet of the CO2 buffer tank 16 is connected to the inlet of the compressor 25 via valve 24. The outlet of the compressor 25 is connected to the return inlet of the dry ice sublimation bed 13. The outlet of the CO2 buffer tank 16 is connected to the inlet of the CO2 energy storage module 18 via valve 17. The outlet of the CO2 energy storage module 18 is connected to the inlet of the high-pressure CO2 storage tank 20 via valve 19. The outlet of the high-pressure CO2 storage tank 20 is connected to the inlet of the CO2 energy release module 22 via valve 21. The outlet of the CO2 energy release module 22 is connected to the gas inlet of the CO2 sublimator 1, forming a closed loop.

[0010] The devices connected by single arrows in the above circuits are connected by pipes, and each valve is connected to the corresponding pipe.

[0011] When the above system is implemented, the operating modes can be divided into energy release mode and energy storage mode:

[0012] In the energy release mode, CO2 in the high-pressure CO2 storage tank 20 enters the CO2 energy release module 22 for multi-stage heating and expansion to generate electricity; the expanded gaseous CO2 enters the CO2 sublimator 1 from below; simultaneously, liquid air in the liquid air storage tank is pumped to the top of the sublimator for spraying via a cryogenic pump; in the CO2 sublimator 1, the gaseous CO2 and the liquid air sprayed from top to bottom exchange heat countercurrently, the CO2 sublimates into dry ice particles and settles, and after continuous collection and filtration, it is sent to the dry ice storage chamber 12 for storage; part of the liquid air vaporizes, the gas phase is collected and pressurized by the air compressor 4; the liquid phase is collected and filtered and sent to the cold storage unit 3 by the liquid air pump 2, where it absorbs heat and vaporizes using the heat stored in the cold storage unit, and the released cold energy is used to recharge the cold storage unit. The vaporized air merges with the air outlet of the compressor 4 and enters the air energy release module 5 for full heating and expansion to do work, and finally the low-pressure air is discharged into the atmosphere.

[0013] In the energy storage mode, the spiral conveyor at the bottom of the dry ice storage chamber 12 is activated to send dry ice from above into the dry ice sublimation bed 13; gaseous CO2 in the CO2 buffer tank 16 is blown into the dry ice sublimation bed 13 from below by the compressor 25, which blows up and heats the dry ice particles to sublimate them, and the resulting gaseous CO2 is sent to the CO2-air heat exchanger 14; the air energy storage module 23 draws air from the atmosphere, compresses and cools it through multiple stages, and then sends it to the CO2-air heat exchanger 14 to exchange heat with the gaseous CO2 from the dry ice sublimation bed 13 in a countercurrent manner; the cooled compressed air enters the cold storage unit 3, utilizing the stored energy... The cold energy is further cooled, and then throttled and depressurized by the expansion valve 6 to form a gas-liquid two-phase flow. The two-phase flow is separated in the gas-liquid separator 7. The liquid phase is stored in the liquid air storage tank 9, and the gas phase is returned to the cold accumulator 3 for re-condensation. At the same time, the gaseous CO2 heated in the heat exchanger enters the CO2 buffer tank 16. Part of it is sent back to the sublimation bed by the compressor to participate in the circulation, and the other part enters the CO2 energy storage module 18 for multi-stage compression and cooling to form high-pressure CO2, which is stored in the high-pressure CO2 storage tank 20. Finally, the air side completes the storage from atmospheric pressure air to liquid air, and the CO2 side achieves the storage from dry ice to high-pressure CO2.

[0014] Specifically, the air-CO2 heat exchange system includes a dry ice sublimation bed 13, which includes an air distribution plate 13-1, a sublimation chamber 13-2, and a filter plate 13-3. The air distribution plate 13-1 is located at the lower gas inlet of the sublimation chamber 13-2, and the filter plate 13-3 is located at the upper part of the sublimation chamber 13-2. During operation, the spiral conveyor at the lower part of the dry ice storage chamber 12 is activated, gradually feeding the stored dry ice into the dry ice sublimation bed 13 from above. Then, gaseous CO2 in the CO2 buffer tank is blown into the dry ice sublimation bed 13 from below by the compressor 25, passing through the air distribution plate 13-1 at the lower part of the dry ice sublimation bed 13 to form a dense and uniform airflow. In the sublimation chamber 13-2, the CO2 exchanges heat with the dry ice particles, causing the dry ice particles to sublimate and generate gaseous CO2. The gas-solid mixture is filtered by the filter plate 13-3 to remove large dry ice particles before being sent to the CO2-air heat exchanger 14.

[0015] This invention provides an air-CO2 heat exchange process for coupling liquid air and dry ice CO2 energy storage, which has the following effects: Through process design, liquid air energy storage and CO2 energy storage are combined. By utilizing the energy complementarity between gaseous CO2 sublimation and liquid air vaporization during energy release, and CO2 dry ice sublimation and air liquefaction during energy storage, the dry ice storage of CO2 on the low-pressure side is cleverly realized, the capacity of the air accumulator is reduced, and the energy conversion efficiency and energy storage density of the system are improved. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0017] Figure 2 Schematic diagram of the dry ice sublimation bed 13

[0018] In the diagram: 1-CO2 condenser; 2-liquid air pump; 3-cold accumulator; 4-air compressor; 5-air energy release module; 6-throttle valve; 7-gas-liquid separator; 8-valve; 9-liquid air storage tank; 10-valve; 11-low temperature liquid air pump; 12-dry ice storage chamber; 13-dry ice sublimation bed; 14-CO2-air heat exchanger; 15-valve; 16-CO2 buffer tank; 17-valve; 18-CO2 energy storage module; 19-valve; 20-high pressure CO2 storage tank; 21-valve; 22-CO2 energy release module; 23-air energy storage module; 24-valve; 25-compressor; 13-1-air distribution plate; 13-2-sublimation chamber; 13-3-filter plate. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the flow shown in the figures. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0020] The aforementioned air-CO2 heat exchange system for coupling liquid air and dry ice CO2 energy storage includes an air passage and a CO2 loop:

[0021] The air passage includes an air energy storage module 23. The inlet of the air energy storage module 23 is connected to the atmosphere. The outlet of the air energy storage module 23 is connected to the hot side inlet of the CO2-air heat exchanger 14. The cold side outlet of the CO2-air heat exchanger 14 is connected to the hot side inlet of the cold accumulator 3. The cold side outlet of the cold accumulator 3 is connected to the inlet of the gas-liquid separator 7 via a throttle valve 6. The gas phase outlet of the gas-liquid separator 7 is connected to the return port of the cold accumulator 3. The liquid phase outlet of the gas-liquid separator 7 is connected to the inlet of the liquid air storage tank 9 via a valve 8. The outlet of the liquid air storage tank 9 is connected to the inlet of the cryogenic liquid air pump 11 via a valve 10. The outlet of the cryogenic liquid air pump 11 is connected to the upper inlet of the CO2 condenser 1. The gas phase outlet of the CO2 condenser 1 is connected to the inlet of the air compressor 4. The outlet of the air compressor 4 is connected to the inlet of the air release module 5. The liquid outlet of the CO2 condenser 1 is connected to the inlet of the liquid air pump 2. The outlet of the liquid air pump 2 is connected to the cold side inlet of the cold accumulator 3. The hot side outlet of the cold accumulator 3 is connected to the inlet of the air release module 5. The outlet of the air release module 5 is open to the atmosphere.

[0022] The CO2 loop includes a CO2 sublimator 1. The solid outlet of the CO2 sublimator 1 is connected to the inlet of the dry ice storage chamber 12. The outlet of the dry ice storage chamber 12 is connected to the dry ice sublimation bed 13 via a spiral conveyor. The gas outlet of the dry ice sublimation bed 13 is connected to the cold side inlet of the CO2-air heat exchanger 14. The hot side outlet of the CO2-air heat exchanger 14 is connected to the inlet of the CO2 buffer tank 16 via valve 15. The return outlet of the CO2 buffer tank 16 is connected to the inlet of the compressor 25 via valve 24. The outlet of the compressor 25 is connected to the return inlet of the dry ice sublimation bed 13. The outlet of the CO2 buffer tank 16 is connected to the inlet of the CO2 energy storage module 18 via valve 17. The outlet of the CO2 energy storage module 18 is connected to the inlet of the high-pressure CO2 storage tank 20 via valve 19. The outlet of the high-pressure CO2 storage tank 20 is connected to the inlet of the CO2 energy release module 22 via valve 21. The outlet of the CO2 energy release module 22 is connected to the gas inlet of the CO2 sublimator 1, forming a closed loop. The dry ice sublimation bed 13 includes a sublimation chamber 13-2, an air distribution plate 13-1 at the lower entrance of the sublimation chamber 13-2, and a filter plate 13-3 in the upper part of the sublimation chamber 13-2.

[0023] The devices connected by single arrows in the above circuits are connected by pipes, and each valve is connected to the corresponding pipe.

[0024] The above system includes the following two operating modes: energy release mode and energy storage mode:

[0025] In the energy release mode, the CO2 gas exiting the CO2 energy release module exchanges heat with liquid air in the sublimator. The gaseous CO2 is converted into dry ice for storage. The remaining liquid air after heat exchange transfers its cooling capacity to the cold storage unit. After completing the energy transfer, it releases energy with the gaseous air to do work and is discharged into the atmosphere.

[0026] The operation process of the energy release mode is as follows: valve 8 is closed, valve 10 is opened, valve 15 is closed, valve 17 is closed, valve 19 is closed, valve 21 is opened, and valve 24 is closed. CO2 in the high-pressure CO2 storage tank 20 flows into the CO2 energy release module 22, undergoes multi-stage heating and expansion to generate electricity, and the expanded gaseous CO2 flows into the CO2 sublimator 1 from below. At the same time, liquid air in the liquid air storage tank 9 is pumped to the top of the CO2 sublimator 1 by the cryogenic liquid air pump 11 and sprayed into it. In CO2 sublimator 1, gaseous CO2 and sprayed liquid air exchange heat counter-currently, causing CO2 to sublimate into dry ice particles and settle. After continuous collection and filtration, the particles are sent to dry ice storage chamber 12 for storage. Simultaneously, some liquid air vaporizes. The gas phase is collected and pressurized by air compressor 4. The liquid phase falls, is filtered and collected, and then pumped into cold accumulator 3 by liquid air pump 2. It absorbs heat and vaporizes using the heat stored in the cold accumulator. The released low-temperature cold energy is used to recharge and cool the cold accumulator 3. The vaporized air merges with the air outlet air of air compressor 4 and flows into air energy release module 5 to fully release energy and do work. The expanded low-pressure air is discharged into the atmosphere. Thus, the air side completes the process of releasing energy and doing work from liquid air to gas, while the CO2 side completes the process of releasing energy and doing work from high-pressure CO2, and then exchanging heat to condense into dry ice for storage in the storage tank.

[0027] In the energy storage mode, the CO2 at the inlet of the CO2 energy storage module comes from the gaseous CO2 in the buffer tank. The gaseous CO2 in the buffer tank enters the sublimation bed, where it directly exchanges heat with dry ice and turns into gaseous CO2. The low-temperature gaseous CO2 then exchanges heat with high-pressure air, and after being heated, it enters the CO2 buffer tank. The cooled air continues to enter the cold storage unit to finally obtain liquid air.

[0028] The operation of the energy storage mode is as follows: valve 8 opens, valve 10 closes, valve 15 opens, valve 17 opens, valve 19 opens, valve 21 closes, and valve 24 opens. The spiral conveyor at the bottom of the dry ice storage chamber 12 is activated, gradually feeding the stored dry ice from above into the dry ice sublimation bed 13. Then, gaseous CO2 from the CO2 buffer tank is blown from below into the dry ice sublimation bed 13 by compressor 25, passing through the air distribution plate 13-1 at the bottom of the dry ice sublimation bed 13 to form a dense and uniform airflow. This airflow exchanges heat with the dry ice particles in the sublimation chamber 13-2, causing the dry ice particles to sublimate and produce gaseous CO2. The gas-solid mixture is filtered through filter plate 13-3 to remove large dry ice particles before being sent to the CO2-air heat exchanger 14. The air energy storage module 23 draws low-pressure air from the outside atmosphere, performs multi-stage compression and cooling, and then sends it to the CO2-air heat exchanger 14 for counter-current heat exchange with the gaseous CO2 generated in the sublimation bed. The cooled air is introduced into the cold accumulator 3, where it is further cooled using the stored cold energy. It then passes through a throttling valve 6 for further cooling and depressurization, forming a gas-liquid two-phase mixture. This mixture flows into the gas-liquid separator 7 for separation; the liquid phase is stored in the liquid air storage tank 9, while the gas phase flows back to the cold accumulator for re-condensation. Simultaneously, the heated gaseous CO2 flows into the CO2 buffer tank 16. A portion is sent to the sublimation bed via the compressor 25 for further heat exchange, while another portion is sent to the CO2 energy storage module 18 for multi-stage compression and cooling, transforming it into high-pressure CO2, which is then stored in the high-pressure CO2 storage tank 20. This process is repeated until the air is completely liquefied and stored entirely in the liquid air storage tank 9, and the dry ice is completely sublimated and converted into high-pressure CO2 stored in the high-pressure CO2 storage tank 20. Thus, the air side completes the storage process from ambient temperature air to high-pressure air, and then to liquid air, while the CO2 side completes the sublimation of dry ice and compression into the high-pressure storage tank.

Claims

1. An air-CO2 heat exchange system for coupling liquid air and dry ice CO2 energy storage, characterized in that, The system includes an air passage and a CO2 loop: The air passage includes an air energy storage module (23). The inlet of the air energy storage module (23) is connected to the atmosphere. The outlet of the air energy storage module (23) is connected to the hot side inlet of the CO2-air heat exchanger (14). The cold side outlet of the CO2-air heat exchanger (14) is connected to the hot side inlet of the cold accumulator (3). The cold side outlet of the cold accumulator (3) is connected to the inlet of the gas-liquid separator (7) via a throttle valve (6). The gas phase outlet of the gas-liquid separator (7) is connected to the return port of the cold accumulator (3). The liquid phase outlet of the gas-liquid separator (7) is connected to the inlet of the liquid air storage tank (9) via a valve (8). The liquid air storage tank (9) The outlet is connected to the inlet of the cryogenic liquid air pump (11) via valve (10), the outlet of the cryogenic liquid air pump (11) is connected to the upper inlet of the CO2 condenser (1), the gaseous outlet of the CO2 condenser (1) is connected to the inlet of the air compressor (4), the outlet of the air compressor (4) is connected to the inlet of the air release module (5), the liquid outlet of the CO2 condenser (1) is connected to the inlet of the liquid air pump (2), the outlet of the liquid air pump (2) is connected to the cold side inlet of the cold accumulator (3), the hot side outlet of the cold accumulator (3) is connected to the inlet of the air release module (5), and the outlet of the air release module (5) is connected to the atmosphere. The CO2 circuit includes a CO2 sublimator (1), the solid outlet of which is connected to the inlet of a dry ice storage chamber (12), the outlet of which is connected to a dry ice sublimation bed (13) via a spiral conveyor, the gas outlet of which is connected to the cold side inlet of a CO2-air heat exchanger (14), the hot side outlet of which is connected to the inlet of a CO2 buffer tank (16) via a valve (15), and the reflux outlet of which is connected to a compressor via a valve (24). (25) Inlet, compressor (25) outlet is connected to dry ice sublimation bed (13) reflux inlet, CO2 buffer tank (16) outlet is connected to CO2 energy storage module (18) inlet via valve (17), CO2 energy storage module (18) outlet is connected to high pressure CO2 storage tank (20) inlet via valve (19), high pressure CO2 storage tank (20) outlet is connected to CO2 energy release module (22) inlet via valve (21), CO2 energy release module (22) outlet is connected to CO2 condenser (1) gas inlet, forming a closed loop.

2. The air-CO2 heat exchange system for coupling liquid air and dry ice CO2 energy storage according to claim 1, characterized in that, The dry ice sublimation bed (13) includes an air distribution plate (13-1), a sublimation chamber (13-2), and a filter plate (13-3); the air distribution plate (13-1) is provided at the lower gas inlet of the sublimation chamber (13-2), and the filter plate (13-3) is provided at the upper part of the sublimation chamber (13-2).

3. An air-CO2 heat exchange system for coupling liquid air and dry ice CO2 energy storage according to claim 1 or 2, characterized in that, Its operating mode is as follows: Energy release mode: CO2 in the high-pressure CO2 storage tank (20) flows into the CO2 energy release module (22), undergoes multi-stage heating and expansion to generate electricity, and the expanded gaseous CO2 flows into the CO2 sublimator (1) from below; at the same time, liquid air in the liquid air storage tank (9) is pumped to the top of the CO2 sublimator (1) by the low-temperature liquid air pump (11) and sprayed into it. In the CO2 sublimator (1), the gaseous CO2 and the sprayed liquid air exchange heat in a countercurrent manner, causing the CO2 to condense into dry ice particles and settle. After continuous collection and filtration, it is sent to the dry ice storage chamber (12) for storage; at the same time, part of the liquid air is vaporized, and the gas phase is collected and pressurized by the air compressor (4); After the liquid phase falls and is collected by filtration, it is pumped into the cold storage unit (3) by the liquid air pump (2). The heat stored in the cold storage unit is used to absorb heat and vaporize. The released low-temperature cold energy is used to recharge the cold storage unit (3). The vaporized air merges with the air outlet air of the air compressor (4) and flows into the air energy release module (5) to fully release energy and do work. The expanded low-pressure air is discharged into the atmosphere. Thus, the air side completes the process of releasing energy and doing work from liquid air to gas, while the CO2 side completes the process of releasing energy and doing work from high-pressure CO2, and then heat exchange and condense into dry ice for storage in the tank. Energy storage mode: The spiral conveyor at the bottom of the dry ice storage chamber (12) is started to gradually send the stored dry ice into the dry ice sublimation bed (13) from the top. Then, the gaseous CO2 in the CO2 buffer tank is blown into the dry ice sublimation bed (13) from the bottom by the compressor (25). After exchanging heat with the dry ice particles, the generated gaseous CO2 flows into the CO2-air heat exchanger (14). The air energy storage module (23) draws low-pressure air from the outside atmosphere, performs multi-stage compression and cooling, and sends it into the CO2-air heat exchanger (14) to exchange heat with the gaseous CO2 generated in the sublimation bed in a countercurrent manner. The cooled air is fed into the cold storage unit (3), where it is further cooled using the stored cold energy. It is then further cooled and depressurized by the throttle valve (6) to form a gas-liquid two-phase mixed flow. The mixed flow flows into the gas-liquid separator (7) for separation. The liquid phase is stored in the liquid air storage tank (9), and the gas phase flows back to the cold storage unit for re-condensation. At the same time, the heated gaseous CO2 flows into the CO2 buffer tank (16). Part of it is sent to the sublimation bed via the compressor (25) for further heat exchange, and part of it is sent to the CO2 energy storage module (18) for multi-stage compression and cooling to transform it into high-pressure CO2, which is then stored in the high-pressure CO2 storage tank (20). The above process is repeated until the air is completely liquefied and stored entirely in the liquid air storage tank (9), and the dry ice is completely sublimated and converted into storage in the high-pressure CO2 storage tank (20). Thus, the air side completes the storage process from room temperature air to high-pressure air and then to liquid air, while the CO2 side completes the sublimation of dry ice and compression into the high-pressure storage tank.

4. An air-CO2 heat exchange system for coupling liquid air and dry ice CO2 energy storage according to claim 2 or 3, characterized in that, Gaseous CO2 is blown into the dry ice sublimation bed (13) from below by the compressor (25), passes through the air distribution plate (13-1) at the bottom of the dry ice sublimation bed (13), and forms a dense and uniform airflow. It exchanges heat with the dry ice particles in the sublimation chamber (13-2), causing the dry ice particles to sublimate and generate gaseous CO2. The gas-solid mixture is filtered through the filter plate (13-3) to remove large dry ice particles and then sent to the CO2-air heat exchanger (14).

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