Liquid compressed air combined cooling, heating and power system and method

Abstract

The application discloses a liquid compressed air cold, heat and electricity combined supply energy storage system and method, and belongs to the technical field of liquid compressed air energy storage. The system comprises a compressed air unit, a carbon dioxide precooling unit, a Claude cycle liquefaction unit, an expansion power generation unit, a heat supply output unit and a cold supply output unit. The application couples the closed transcritical carbon dioxide precooling unit with the traditional Claude liquefaction cycle, strengthens the high-pressure air precooling effect, improves the air liquefaction rate and reduces the liquefaction energy consumption; meanwhile, a compressed heat and low-temperature cold energy double closed loop recovery system is constructed, and the energy cascade utilization is realized. The system can store energy and liquefy in the off-peak period of the power grid, and simultaneously realizes the cold, heat and electricity combined supply in the peak power consumption period, and has the advantages of high energy storage density, small site selection limitation, high operation flexibility, good comprehensive energy efficiency and the like.

Description

Technical Field

[0001] This invention belongs to the field of liquid compressed air energy storage, specifically relating to a liquid compressed air combined cooling, heating and power (CCHP) energy storage system and method. Background Technology

[0002] With the increasing proportion of renewable energy generation, the demand for large-scale, long-term energy storage technology in the power grid is becoming increasingly urgent. Air has a critical temperature of 132.45 K and a critical pressure of 3.77 MPa. When the ambient temperature is below its critical temperature and the pressure is above its critical pressure, compressed air can undergo a gas-liquid phase change. Liquid compressed air energy storage technology utilizes this physical property, increasing energy density by several to more than ten times compared to traditional non-combustion compressed air energy storage. Simultaneously, liquid compressed air energy storage systems possess significant advantages such as less site constraint, long service life, and safety and environmental friendliness, making them highly valuable for engineering applications in long-term energy storage and integrated energy supply. Furthermore, in combined cooling, heating, and power (CCHP) scenarios, liquid compressed air energy storage systems can achieve stable and coordinated output of multiple energy types—electricity, cooling, and heating—making it one of the key research directions in compressed air energy storage technology.

[0003] Currently, Claude cycle-based liquid compressed air energy storage systems are the mainstream technology with the widest applicability in this field. However, existing traditional Claude cycle liquid compressed air energy storage systems still suffer from problems such as low air liquefaction rate and poor system cycle efficiency. These problems make it difficult for the system to simultaneously meet the grid-side energy storage and peak-shaving needs as well as the user-side demand for multiple energy types (cooling, heating, and power), greatly limiting the large-scale engineering application and technology promotion of traditional Claude cycle liquid compressed air energy storage systems. Therefore, developing a new type of liquid compressed air energy storage system that can improve liquefaction efficiency, achieve energy cascade utilization, and possess combined cooling, heating, and power (CCHP) capabilities has significant practical significance and market value. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned defects in the prior art and provide a liquid compressed air combined cooling, heating and power energy storage system and method, which solves the problems of low air liquefaction rate and system circulation efficiency in the existing traditional Claude cycle liquid compressed air energy storage system.

[0005] On one hand, this invention provides a liquid compressed air combined cooling, heating, and power (CCHP) energy storage system, comprising a compressed air unit, a carbon dioxide precooling unit, a Claude cycle liquefaction unit, a liquid air storage tank, a cooling output unit, an expansion power generation unit, and a heating output unit. The end of the compressed air unit is connected to the inlet of the carbon dioxide precooling unit, the outlet of the carbon dioxide precooling unit is connected to the inlet of the Claude cycle liquefaction unit, the liquid product outlet of the Claude cycle liquefaction unit is connected to the inlet of the liquid air storage tank, and the outlet of the liquid air storage tank is sequentially connected to the cooling output unit and the expansion power generation unit. The compressed air unit contains a high-temperature heat storage tank and a low-temperature heat storage tank, which are connected to the heating output unit and the expansion power generation unit respectively via heat storage medium pipelines.

[0006] Through the above integrated architecture, the system forms the main energy conversion and transfer path of air compression - carbon dioxide precooling - air liquefaction - liquid air storage - cold energy release - heat energy release - expansion power generation, realizing the orderly flow of energy storage medium among various functional units.

[0007] Furthermore, the compressed air unit includes an electric motor, at least one stage compressor, an intercooler corresponding to the compressor stage, and a radiator. The output shaft of the electric motor is coaxially connected to the rotating shaft of each stage compressor, providing power for the compression process. The outlet of each stage compressor is connected in series with the hot-side inlet of the corresponding stage intercooler and the hot-side inlet of the radiator, and the air inlet of the next stage compressor is connected to the hot-side outlet of the previous stage radiator. This series structure ensures that the air, after being compressed and cooled by the previous stage, can enter the next stage at a lower temperature, thereby reducing compression work. The cold-side channels of each stage intercooler are connected in parallel and form a closed compression heat recovery loop with the high-temperature heat storage tank and the low-temperature heat storage tank. This loop is responsible for absorbing and storing the heat generated during the compression process.

[0008] Furthermore, the carbon dioxide precooling unit includes a precooling heat exchanger, a carbon dioxide compressor, a cooler, and a throttling expansion valve. The inlet of the carbon dioxide compressor is connected to the cold-side outlet of the precooling heat exchanger, the outlet of the carbon dioxide compressor is connected to the hot-side inlet of the cooler, the hot-side outlet of the cooler is connected to the inlet of the throttling expansion valve, and the outlet of the throttling expansion valve is connected to the cold-side inlet of the precooling heat exchanger, forming a closed-loop carbon dioxide circulation circuit. The hot-side inlet of the precooling heat exchanger is connected to the hot-side outlet of the last stage radiator in the compressed air unit. This unit utilizes the transcritical carbon dioxide cycle to generate low-temperature cooling capacity to precool the high-pressure air about to enter the liquefaction unit, reducing the inlet temperature of the liquefaction unit and thus improving liquefaction efficiency.

[0009] Further, the Claude cycle liquefaction unit includes a first-end heat exchanger, a distributor, an intermediate heat exchanger, a cryogenic expander, a drive motor, a mixer, a last-end heat exchanger, a throttle valve, and a gas-liquid separator. The hot-side inlet of the first-end heat exchanger is connected to the hot-side outlet of the pre-cooling heat exchanger in the carbon dioxide pre-cooling unit. The hot-side outlet of the first-end heat exchanger is connected to the inlet of the distributor, and the outlet of the distributor is divided into a first path and a second path. The first path is connected to the air inlet of the cryogenic expander, and the second path is connected to the hot-side inlet of the intermediate heat exchanger. The hot-side outlet of the intermediate heat exchanger is connected to the hot-side inlet of the last-end heat exchanger, and the hot-side outlet of the last-end heat exchanger is connected to the inlet of the throttle valve. The outlet of the throttle valve is connected to the inlet of the gas-liquid separator. The liquid product outlet of the gas-liquid separator is connected to the liquid air storage tank, and the gaseous product outlet of the gas-liquid separator is connected to the cold-side inlet of the last-end heat exchanger. The outlet of the cryogenic expander and the cold-side outlet of the terminal heat exchanger are connected to the mixer via a pipeline. The outlet of the mixer is connected to the cold-side inlet of the intermediate heat exchanger, and the cold-side outlet of the intermediate heat exchanger is connected to the cold-side inlet of the first-end heat exchanger. This liquefaction unit achieves efficient liquefaction of high-pressure air through diversion, expansion, throttling, and multi-stage reheating, and recovers the cold energy of the unliquefied air in stages for precooling the air to be liquefied.

[0010] Furthermore, the expansion power generation unit includes a liquid air pressurization pump, at least one stage heater, at least one stage expander, and a generator. The inlet of the liquid air pressurization pump is connected to the outlet of the liquid air storage tank, and the outlet of the liquid air pressurization pump is connected to the cold-side inlet of the cooling heat exchanger in the cooling output unit. The cold-side outlet of the cooling heat exchanger is connected to the cold-side inlets of each stage heater, and the cold-side outlet of each stage heater is connected to the inlet of the corresponding stage expander. The main shafts of each stage expander are rigidly connected coaxially in sequence and coaxially connected to the rotor of the generator. The hot-side channels of each stage heater are connected in parallel and form a heating circulation loop with the high-temperature heat storage tank and the low-temperature heat storage tank. This unit converts the cold energy (used for cooling) and compressed heat energy (used for heating) of liquid air back into mechanical energy and electrical energy, realizing energy release power generation.

[0011] Furthermore, the heating output unit includes a heating heat exchanger. The hot-side inlet of the heating heat exchanger is connected to the outlet of the high-temperature thermal storage tank via pipes and valves, and the hot-side outlet of the heating heat exchanger is connected to the inlet of the low-temperature thermal storage tank. The cold-side inlet and outlet of the heating heat exchanger are used to connect to an external heat load circuit. This unit independently draws heat from the high-temperature thermal storage tank, specifically to meet external heat demands.

[0012] Furthermore, the cooling output unit includes a cooling heat exchanger. The cold-side inlet of the cooling heat exchanger is connected via a pipe to the outlet of the liquid air pressurization pump in the expansion power generation unit, and the cold-side outlet of the cooling heat exchanger is connected to the cold-side inlet of the primary heater in the expansion power generation unit. The hot-side inlet and outlet of the cooling heat exchanger are used to connect to an external cooling load circuit. This unit preferentially releases the low-temperature cold energy contained in the liquid air before heating and expanding to meet external cooling demands.

[0013] On the other hand, the present invention also provides a liquid compressed air combined cooling, heating and power energy storage method, which includes energy storage liquefaction mode and energy release power generation mode.

[0014] Under the described energy storage liquefaction conditions, off-peak electricity from the power grid drives the compressed air unit to perform multi-stage compression of air. The heat of compression is recovered through the intercooler and stored in the high-temperature heat storage tank. The compressed high-pressure air is then sent to the carbon dioxide precooling unit, where it exchanges heat with the closed-loop low-temperature carbon dioxide working fluid to achieve preliminary precooling. The precooled high-pressure air enters the Claude cycle liquefaction unit, where it undergoes stepped cooling and throttling expansion to form a gas-liquid mixture. The liquid air is then separated and stored in the liquid air storage tank, while the separated low-temperature gaseous air flows back to the Claude cycle liquefaction unit to cool the air to be liquefied.

[0015] Under the described energy release and power generation conditions, the liquid air in the liquid air storage tank is pressurized by the liquid air booster pump and first enters the cooling output unit to release cooling capacity to meet external cooling load demands. Subsequently, the low-temperature air after releasing cooling capacity enters the expansion power generation unit, where it is heated by the high-temperature heat storage medium in the high-temperature heat storage tank. The heated high-pressure air drives the expander to perform work, thereby driving the generator to generate electricity. Simultaneously, a portion of the heat storage medium in the high-temperature heat storage tank is introduced into the heating output unit to release heat to meet external heat load demands.

[0016] Furthermore, under the energy storage liquefaction condition, the low-temperature gaseous air separated by the gas-liquid separator in the Claude cycle liquefaction unit flows sequentially through the cold side of the terminal heat exchanger, mixes with the outlet air of the low-temperature expander in the mixer, and then flows sequentially through the cold side of the intermediate heat exchanger and the cold side of the first-end heat exchanger. After the high-pressure air entering the hot side of each heat exchanger is cooled in stages, it finally flows back to the inlet of the first-stage compressor of the compressed air unit. This closed-loop recirculation path maximizes the recovery of the cold energy of the unliquefied air and significantly reduces liquefaction energy consumption.

[0017] Furthermore, under the energy release and power generation condition, the heat storage medium in the high-temperature heat storage tank is divided into two paths: the first path flows into the heaters of each stage of the expansion power generation unit to heat the low-temperature air before expansion; the second path flows into the heat exchanger of the heat output unit for external heat supply. After releasing heat, both paths of heat storage medium flow back to the low-temperature heat storage tank. This parallel heating path enables flexible allocation of the heat storage medium between power generation and heating, meeting the combined heat and power (CHP) needs of the user side.

[0018] Compared with the prior art, the present invention has the following beneficial effects: I. This invention, by adding a closed-loop transcritical carbon dioxide precooling unit and deeply coupling it with the traditional Claude liquefaction cycle, utilizes the highly efficient cooling capacity of the transcritical carbon dioxide cycle to precool compressed high-pressure air, effectively reducing the inlet temperature of the liquefaction unit. This significantly improves the air liquefaction rate while reducing the energy consumption required for liquefaction, overcoming the shortcomings of the traditional Claude cycle, such as low air liquefaction rate and poor cycle efficiency.

[0019] II. This invention constructs a dual closed-loop recovery system for compression heat and cryogenic cold energy. On one hand, compression heat is recovered through an intercooler and stored in a high-temperature heat storage tank; on the other hand, the cryogenic cold energy of the unliquefied air is recovered in stages through the multi-stage regenerative structure inside the Claude cycle liquefaction unit for precooling the air to be liquefied. This end-to-end closed-loop energy management achieves efficient cascaded utilization of energy, significantly improving the overall operating energy efficiency of the system.

[0020] Third, this invention possesses the synergistic output capability of combined cooling, heating, and power generation. During the energy release phase, the high-grade cold energy contained within the liquid air is preferentially released after pressurization for cooling purposes; then, the stored heat of compression is used to heat the low-temperature air, driving the expander to generate electricity; simultaneously, some heat can be diverted from the high-temperature thermal storage tank for heating. This system can simultaneously address peak shaving and valley filling on the grid side and diversified energy needs on the user side, making it particularly suitable for distributed energy supply scenarios such as industrial parks and integrated energy stations. The system exhibits strong adaptability to various operating conditions and high operational flexibility, possessing extremely high engineering promotion value and promising prospects for industrial application. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a liquid compressed air combined cooling, heating and power (CCHP) energy storage system.

[0022] The components include: 1. Electric motor; 2. Primary compressor; 3. Primary intercooler; 4. Primary radiator; 5. Secondary compressor; 6. Secondary intercooler; 7. Secondary radiator; 8. Tertiary compressor; 9. Tertiary intercooler; 10. Tertiary radiator; 11. High-temperature heat storage tank; 12. Heating heat exchanger; 13. Low-temperature heat storage tank; 14. Pre-cooling heat exchanger; 15. Carbon dioxide compressor; 16. Gas cooler; 17. Throttling expansion valve; 18. Initial heat exchanger. 19. Diverter; 20. Intermediate heat exchanger; 21. Cryogenic expander; 22. Drive motor; 23. Mixer; 24. Terminal heat exchanger; 25. Throttling valve; 26. Gas-liquid separator; 27. Liquid air storage tank; 28. Liquid air transfer pump; 29. ​​Cooling heat exchanger; 30. Primary heater; 31. Secondary heater; 32. Tertiary heater; 33. Primary expander; 34. Secondary expander; 35. Tertiary expander; 36. Generator. Detailed Implementation

[0023] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0024] Example 1: This example provides a liquid compressed air combined cooling, heating, and power (CCHP) energy storage system. The system comprises six functional units: a compressed air unit, a carbon dioxide pre-cooling unit, a Claude cycle liquefaction unit, an expansion power generation unit, a heating output unit, and a cooling output unit.

[0025] The compressed air unit is used to complete multi-stage air compression and waste heat recovery during the energy storage phase. Specifically, the unit includes a motor 1, a primary compressor 2, a primary intercooler 3, a primary radiator 4, a secondary compressor 5, a secondary intercooler 6, a secondary radiator 7, a tertiary compressor 8, a tertiary intercooler 9, a tertiary radiator 10, a high-temperature heat storage tank 11, and a low-temperature heat storage tank 13. The output shaft of the motor 1 is coaxially connected to the shafts of the primary compressor 2, the secondary compressor 5, and the tertiary compressor 8, providing them with driving force. The outlet of the primary compressor 2 is connected in series with the hot-side inlet of the primary intercooler 3 and the hot-side inlet of the primary radiator 4, and the hot-side outlet of the primary radiator 4 is connected to the inlet of the secondary compressor 5. The outlet of the secondary compressor 5 is connected in series with the hot-side inlet of the secondary intercooler 6 and the hot-side inlet of the secondary radiator 7, and the hot-side outlet of the secondary radiator 7 is connected to the inlet of the tertiary compressor 8. The outlet of the tertiary compressor 8 is connected in series with the hot-side inlet of the tertiary intercooler 9 and the hot-side inlet of the tertiary radiator 10. The cold-side channels of each stage of the intercooler (3, 6, 9) are connected in parallel through pipes, forming a closed compression heat recovery loop with the high-temperature heat storage tank 11, the low-temperature heat storage tank 13, and the corresponding circulating pump. The heat storage medium (such as heat transfer oil or pressurized water) circulates in this loop, absorbs the heat of compression, heats up, and is stored in the high-temperature heat storage tank 11.

[0026] The carbon dioxide precooling unit employs a closed-loop transcritical carbon dioxide cycle structure for preliminary precooling of high-pressure, ambient-temperature air from the compressed air unit. This unit includes a precooling heat exchanger 14, a carbon dioxide compressor 15, a gas cooler 16, and a throttling expansion valve 17. The inlet of the carbon dioxide compressor 15 is connected to the cold-side outlet of the precooling heat exchanger 14, and the outlet of the carbon dioxide compressor 15 is connected to the hot-side inlet of the gas cooler 16. The hot-side outlet of the gas cooler 16 is connected to the inlet of the throttling expansion valve 17, and the outlet of the throttling expansion valve 17 is connected to the cold-side inlet of the precooling heat exchanger 14, thus forming a complete closed-loop carbon dioxide cycle. The hot-side inlet of the precooling heat exchanger 14 is connected to the hot-side outlet of the three-stage radiator 10 of the compressed air unit.

[0027] The Claude circulating liquefaction unit is used to perform staged cooling and liquefaction of pre-cooled high-pressure air. This unit includes a first-end heat exchanger 18, a distributor 19, an intermediate heat exchanger 20, a cryogenic expander 21, a drive motor 22, a mixer 23, a last-end heat exchanger 24, a throttle valve 25, and a gas-liquid separator 26. The hot-side inlet of the first-end heat exchanger 18 is connected to the hot-side outlet of the pre-cooling heat exchanger 14. The hot-side outlet of the first-end heat exchanger 18 is connected to the inlet of the distributor 19, and the outlet of the distributor 19 is divided into a first path and a second path. The first path is connected to the inlet of the cryogenic expander 21, and the second path is connected to the hot-side inlet of the intermediate heat exchanger 20. The hot-side outlet of the intermediate heat exchanger 20 is connected to the hot-side inlet of the last-end heat exchanger 24, and the hot-side outlet of the last-end heat exchanger 24 is connected to the inlet of the throttle valve 25. The outlet of the throttle valve 25 is connected to the inlet of the gas-liquid separator 26. The liquid product outlet of the gas-liquid separator 26 is connected to a liquid air storage tank 27. The gaseous product outlet of the gas-liquid separator 26 is connected to the cold-side inlet of the terminal heat exchanger 24. The outlet of the cryogenic expander 21 and the cold-side outlet of the terminal heat exchanger 24 are connected to the mixer 23 via a pipeline. The outlet of the mixer 23 is connected to the cold-side inlet of the intermediate heat exchanger 20, and the cold-side outlet of the intermediate heat exchanger 20 is connected to the cold-side inlet of the first-end heat exchanger 18. The cold-side outlet of the first-end heat exchanger 18 is connected back to the inlet of the first-stage compressor 2 via a pipeline. The output shaft of the drive motor 22 is coaxially connected to the main shaft of the cryogenic expander 21 to provide power or recover expansion work during startup or when needed.

[0028] The expansion power generation unit is used to efficiently release the energy stored in liquid air as electrical energy during the energy release phase. This unit includes a liquid air delivery pump 28, a primary heater 30, a secondary heater 31, a tertiary heater 32, a primary expander 33, a secondary expander 34, a tertiary expander 35, and a generator 36. The inlet of the liquid air delivery pump 28 is connected to the outlet of the liquid air storage tank 27. The outlet of the liquid air delivery pump 28 is connected to the cold-side inlet of the cooling heat exchanger 29 of the cooling output unit. The cold-side outlet of the cooling heat exchanger 29 is sequentially connected to the cold-side inlets of the primary heater 30, the secondary heater 31, and the tertiary heater 32. The cold-side outlet of the primary heater 30 is connected to the inlet of the primary expander 33, the cold-side outlet of the secondary heater 31 is connected to the inlet of the secondary expander 34, and the cold-side outlet of the tertiary heater 32 is connected to the inlet of the tertiary expander 35. The main shafts of the primary expander 33, the secondary expander 34, and the tertiary expander 35 are rigidly connected coaxially in sequence and are also coaxially connected to the rotor of the generator 36. The hot-side channels of the primary heater 30, the secondary heater 31, and the tertiary heater 32 are connected in parallel and form a closed heating circulation loop with the high-temperature heat storage tank 11 and the low-temperature heat storage tank 13 through pipelines and a circulating pump.

[0029] The heating output unit is used to realize flexible combined supply of heat energy and mainly includes a heating heat exchanger 12. The hot-side inlet of the heating heat exchanger 12 is connected to the outlet of the high-temperature heat storage tank 11 through pipes and control valves, and the hot-side outlet of the heating heat exchanger 12 is connected to the inlet of the low-temperature heat storage tank 13. The cold-side inlet and outlet of the heating heat exchanger 12 are used to connect to external heat user circuits.

[0030] The cooling output unit is used to directly utilize cold energy and mainly includes a cooling heat exchanger 29. The cold-side inlet of the cooling heat exchanger 29 is connected to the outlet of the liquid air delivery pump 28 via a pipe, and the cold-side outlet of the cooling heat exchanger 29 is connected to the cold-side inlet of the primary heater 30. The hot-side inlet and outlet of the cooling heat exchanger 29 are used to connect to external cold user circuits.

[0031] Example 2: This example provides a liquid compressed air combined cooling, heating and power energy storage method based on the above system, including two operating conditions: energy storage liquefaction and energy release for power generation.

[0032] Energy Storage Liquefaction Mode: During off-peak electricity pricing periods at night or periods of abundant renewable energy curtailment, the system activates its energy storage mode. Motor 1 drives primary compressor 2, secondary compressor 5, and tertiary compressor 8 to progressively pressurize air to a high-pressure state (e.g., 8-15 MPa). The high-temperature, high-pressure air generated after each stage of compression sequentially enters the corresponding primary intercooler 3, secondary intercooler 6, tertiary intercooler 9, and primary radiators 4, secondary radiators 7, and tertiary radiators 10. In these intercoolers, the heat of compression is absorbed by the heat storage medium from the low-temperature heat storage tank 13. The increased temperature of the heat storage medium then flows into the high-temperature heat storage tank 11, completing the storage of the heat of compression. After further cooling by multiple radiators, the high-pressure, ambient-temperature air (approximately 25-40°C) leaves the compressed air unit.

[0033] The high-pressure, ambient-temperature air enters the hot side of the precooling heat exchanger 14 in the carbon dioxide precooling unit. In the precooling heat exchanger 14, the air undergoes countercurrent heat exchange with the low-temperature, low-pressure carbon dioxide working fluid (approximately -10°C to 5°C) from the throttling expansion valve 17, and is initially precooled to 5-15°C. After absorbing heat, the carbon dioxide working fluid is pressurized by the carbon dioxide compressor 15, cooled by the gas cooler 16, and then cooled again by the throttling expansion valve 17, forming a transcritical cycle that continuously provides precooling capacity.

[0034] Pre-cooled high-pressure cryogenic air enters the Claude circulation liquefaction unit. First, it undergoes preliminary reheating and cooling with returning cryogenic non-condensable gas in the initial heat exchanger 18. Then, it enters the distributor 19, splitting into two streams: the first stream (approximately 20%-40%) enters the cryogenic expander 21 for expansion and cooling to approximately -100°C to -140°C; the second stream (approximately 60%-80%) sequentially enters the intermediate heat exchanger 20 and the final heat exchanger 24, where it is cooled to near its liquefaction temperature by the counter-flowing cryogenic non-condensable gas. Finally, it passes through the throttling valve 25, reducing its pressure and temperature to below the air liquefaction temperature (approximately -150°C to -190°C), forming a gas-liquid mixture. This mixture enters the gas-liquid separator 26, where the separated liquid air (approximately -150°C to -190°C) is sent to the liquid air storage tank 27 for storage. The separated low-temperature non-condensable gas (approximately -150°C to -190°C) first flows through the cold side of the terminal heat exchanger 24, pre-cooling the second stream of high-pressure air entering the heat exchanger. Then, it mixes with the low-temperature air discharged from the low-temperature expander 21 in the mixer 23, raising its temperature to approximately -100°C to -140°C. The mixed airflow then flows sequentially through the cold sides of the intermediate heat exchanger 20 and the first-end heat exchanger 18, subjecting the high-pressure air entering the hot sides of these heat exchangers to staged recooling. After its own temperature rises to near ambient temperature, it finally flows back to the inlet of the first-stage compressor 2, completing one closed-loop cycle. Thus, the energy storage process efficiently converts off-peak electricity into the low-temperature potential energy of liquid air and the thermal energy of the high-temperature heat storage medium.

[0035] Energy release and combined heat and power (CHP) operation: During peak electricity consumption periods on the power grid, the system activates the energy release mode. The cryogenic liquid air (approximately -150°C to -190°C) in the liquid air storage tank 27 is first pressurized to 5-10 MPa by the liquid air delivery pump 28. The pressurized, high-pressure cryogenic liquid air first enters the cold side of the cooling heat exchanger 29, where it exchanges heat with the heat medium from the external cooling load circuit, releasing its high-grade cold energy to provide users with cooling loads such as air conditioning and process cooling. After releasing the cold energy, the liquid air vaporizes and heats up to a cryogenic gaseous state of approximately -50°C to -20°C. This cryogenic, high-pressure gaseous air then enters the expansion power generation unit. During its sequential flow through the primary heater 30, secondary heater 31, and tertiary heater 32, the air exchanges heat with the high-temperature heat storage medium (e.g., 100°C-300°C) extracted from the high-temperature heat storage tank 11, and is progressively heated to near or above ambient temperature (e.g., 20°C-50°C). The heated high-pressure air enters the first-stage expander 33, the second-stage expander 34, and the third-stage expander 35 in sequence to expand and do work, driving the rotor of the coaxially connected generator 36 to rotate, realizing grid-connected power generation and meeting the peak power load of the power grid.

[0036] Meanwhile, the high-temperature thermal storage medium drawn from the high-temperature thermal storage tank 11 is divided into two paths: the first path enters the primary heater 30, secondary heater 31, and tertiary heater 32 of the expansion power generation unit to heat the air. After releasing heat, the temperature decreases and it flows back to the low-temperature thermal storage tank 13; the second path enters the hot side of the heat exchanger 12 of the heat supply output unit to exchange heat with the medium from the external heat load circuit, providing heat loads such as heating and domestic hot water to the outside. After releasing heat, it also flows back to the low-temperature thermal storage tank 13.

[0037] Through the above process, this system simultaneously completes the coordinated output of three energy categories—power supply, cooling supply, and heating supply—during the energy release phase, realizing a true combined cooling, heating, and power (CCHP) function.

[0038] In summary, the liquid compressed air combined cooling, heating and power energy storage system and method provided by this invention effectively solves the problems of low liquefaction efficiency and serious energy waste in traditional technologies by introducing a transcritical carbon dioxide precooling unit and constructing a complete energy closed-loop recovery system.

Claims

1. A liquid compressed air combined cooling, heating, and power (CCHP) energy storage system, characterized in that, It includes a compressed air unit, a carbon dioxide precooling unit, a Claude circulation liquefaction unit, a liquid air storage tank (27), a cooling output unit, an expansion power generation unit, and a heating output unit; the end of the compressed air unit is connected to the inlet of the carbon dioxide precooling unit, the outlet of the carbon dioxide precooling unit is connected to the inlet of the Claude circulation liquefaction unit, the liquid product outlet of the Claude circulation liquefaction unit is connected to the inlet of the liquid air storage tank (27), and the outlet of the liquid air storage tank (27) is connected in sequence to the cooling output unit and the expansion power generation unit; the compressed air unit has a built-in high-temperature heat storage tank (11) and a low-temperature heat storage tank (13), and the high-temperature heat storage tank (11) and the low-temperature heat storage tank (13) are respectively connected to the heating output unit and the expansion power generation unit through heat storage medium pipelines.

2. The liquid compressed air combined cooling, heating, and power (CCHP) energy storage system according to claim 1, characterized in that, The compressed air unit includes an electric motor (1), at least one stage compressor, an intercooler corresponding to the compressor stage, and a radiator; the output shaft of the electric motor (1) is coaxially connected to the rotating shaft of each stage compressor; the outlet of each stage compressor is connected in series with the hot side inlet of the corresponding stage intercooler and the hot side inlet of the radiator, and the air inlet of the next stage compressor is connected to the hot side outlet of the previous stage radiator; the cold side channels of each stage intercooler are connected in parallel and form a closed compression heat recovery loop with the high temperature heat storage tank (11) and the low temperature heat storage tank (13).

3. The liquid compressed air combined cooling, heating, and power (CCHP) energy storage system according to claim 2, characterized in that, The carbon dioxide precooling unit includes a precooling heat exchanger (14), a carbon dioxide compressor (15), a cooler (16), and a throttling expansion valve (17). The inlet of the carbon dioxide compressor (15) is connected to the cold side outlet of the precooling heat exchanger (14), the outlet of the carbon dioxide compressor (15) is connected to the hot side inlet of the cooler (16), the hot side outlet of the cooler (16) is connected to the inlet of the throttling expansion valve (17), and the outlet of the throttling expansion valve (17) is connected to the cold side inlet of the precooling heat exchanger (14), forming a closed carbon dioxide circulation loop. The hot side inlet of the precooling heat exchanger (14) is connected to the hot side outlet of the last stage radiator in the compressed air unit.

4. The liquid compressed air combined cooling, heating, and power (CCHP) energy storage system according to claim 1, characterized in that, The Claude circulating liquefaction unit includes a first-end heat exchanger (18), a distributor (19), an intermediate heat exchanger (20), a cryogenic expander (21), a drive motor (22), a mixer (23), a last-end heat exchanger (24), a throttle valve (25), and a gas-liquid separator (26). The hot-side inlet of the first-end heat exchanger (18) is connected to the hot-side outlet of the precooling heat exchanger (14) in the carbon dioxide precooling unit. The hot-side outlet of the first-end heat exchanger (18) is connected to the inlet of the distributor (19), and the outlet of the distributor (19) is divided into a first path and a second path. The first path is connected to the inlet of the cryogenic expander (21), and the second path is connected to the hot-side inlet of the intermediate heat exchanger (20). The hot-side outlet of the intermediate heat exchanger (20) is connected to the... The hot-side inlet of the terminal heat exchanger (24) is connected to the inlet of the throttle valve (25), and the outlet of the throttle valve (25) is connected to the inlet of the gas-liquid separator (26). The liquid product outlet of the gas-liquid separator (26) is connected to the liquid air storage tank (27), and the gaseous product outlet of the gas-liquid separator (26) is connected to the cold-side inlet of the terminal heat exchanger (24). The outlet of the cryogenic expander (21) and the cold-side outlet of the terminal heat exchanger (24) are connected to the mixer (23) through a pipeline. The outlet of the mixer (23) is connected to the cold-side inlet of the intermediate heat exchanger (20), and the cold-side outlet of the intermediate heat exchanger (20) is connected to the cold-side inlet of the first-end heat exchanger (18).

5. A liquid compressed air combined cooling, heating, and power (CCHP) energy storage system according to claim 1, characterized in that, The expansion power generation unit includes a liquid air pressurization pump (28), at least one stage heater, at least one stage expander, and a generator (36). The inlet of the liquid air pressurization pump (28) is connected to the outlet of the liquid air storage tank (27), and the outlet of the liquid air pressurization pump (28) is connected to the cold side inlet of the cooling heat exchanger (29) in the cooling output unit. The cold side outlet of the cooling heat exchanger (29) is connected to the cold side inlet of each stage heater, and the cold side outlet of each stage heater is connected to the inlet of the corresponding stage expander. The main shafts of each stage expander are coaxially rigidly connected in sequence and coaxially connected to the rotor of the generator (36). The hot side channels of each stage heater are connected in parallel and form a heating circulation loop with the high temperature heat storage tank (11) and the low temperature heat storage tank (13).

6. The liquid compressed air combined cooling, heating, and power (CCHP) energy storage system according to claim 1, characterized in that, The heating output unit includes a heating heat exchanger (12); the hot side inlet of the heating heat exchanger (12) is connected to the outlet of the high-temperature heat storage tank (11) through pipes and valves, and the hot side outlet of the heating heat exchanger (12) is connected to the inlet of the low-temperature heat storage tank (13); the cold side inlet and outlet of the heating heat exchanger (12) are used to connect to an external heat load circuit.

7. A liquid compressed air combined cooling, heating, and power (CCHP) energy storage system according to claim 1, characterized in that, The cooling output unit includes a cooling heat exchanger (29); the cold side inlet of the cooling heat exchanger (29) is connected to the outlet of the liquid air pressurization pump (28) in the expansion power generation unit through a pipe, and the cold side outlet of the cooling heat exchanger (29) is connected to the cold side inlet of the primary heater in the expansion power generation unit; the hot side inlet and outlet of the cooling heat exchanger (29) are used to connect to the external cooling load circuit.

8. A liquid compressed air combined cooling, heating, and power (CCHP) energy storage method based on the system described in any one of claims 1 to 7, characterized in that, This includes energy storage liquefaction mode and energy release power generation mode; Under the energy storage liquefaction condition, the compressed air unit is driven by off-peak electricity from the power grid to perform multi-stage compression of air. The compression heat is recovered through the intercooler and stored in the high-temperature heat storage tank (11). The compressed high-pressure air is sent to the carbon dioxide precooling unit and exchanged heat with the closed-loop low-temperature carbon dioxide working fluid to achieve preliminary precooling. The precooled high-pressure air enters the Claude cycle liquefaction unit and forms a gas-liquid mixture after step cooling and throttling expansion. The liquid air is stored in the liquid air storage tank (27) through gas-liquid separation. The separated low-temperature gaseous air flows back to the Claude cycle liquefaction unit to cool the air to be liquefied. Under the energy release and power generation conditions, the liquid air in the liquid air storage tank (27) is pressurized by the liquid air pressurization pump (28) and first enters the cooling output unit to release cold energy to meet the external cooling load demand. Subsequently, the low-temperature air after releasing cold energy enters the expansion power generation unit and is heated by the high-temperature heat storage medium in the high-temperature heat storage tank (11). The heated high-pressure air drives the expander to do work and drives the generator (36) to generate electricity. At the same time, part of the heat storage medium in the high-temperature heat storage tank (11) is introduced into the heating output unit to release heat to meet the external heat load demand.

9. The liquid compressed air combined cooling, heating, and power energy storage method according to claim 8, characterized in that, Under the energy storage liquefaction condition, the low-temperature gaseous air separated by the gas-liquid separator (26) in the Claude cycle liquefaction unit flows sequentially through the cold side of the terminal heat exchanger (24), mixes with the outlet air of the low-temperature expander (21) in the mixer (23), and then flows sequentially through the cold side of the intermediate heat exchanger (20) and the cold side of the first end heat exchanger (18). After the high-pressure air entering the hot side of each heat exchanger is cooled in stages, it finally flows back to the inlet of the first stage compressor of the compressed air unit.

10. The liquid compressed air combined cooling, heating, and power energy storage method according to claim 8, characterized in that, Under the energy release and power generation conditions, the heat storage medium in the high-temperature heat storage tank (11) is divided into two paths: the first path of heat storage medium flows into the heaters of each stage of the expansion power generation unit to heat the low-temperature air before expansion; the second path of heat storage medium flows into the heat exchanger (12) of the heat supply output unit to supply heat to the outside; after the heat storage medium releases heat, it flows back to the low-temperature heat storage tank (13).

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