Supercritical co2 phase change cooling thermal prevention and control system and method for energy storage and power battery

Abstract

The application discloses a supercritical CO2 phase change cooling heat prevention and control system and method for energy storage and power batteries. The application utilizes the thermal physical property change of supercritical CO2 near the critical point, and the volume of supercritical CO2 is greatly reduced, so that the heat dissipation efficiency is extremely high. A multi-stage energy recovery framework is adopted, and through the synergistic effect of a heat exchanger and a regenerator, the step-by-step utilization of energy is realized. A phase change evaporation module effectively solves the heat dissipation problem of high power density. Modular design makes the land occupation area of the heat management system very low. The application can stably operate in the range of 0-100 DEG C of ambient temperature, and is suitable for severe working conditions such as variable rate frequent charging and discharging. An emergency system for thermal runaway is integrated, and liquid direct injection can be completed in a few seconds to form an inert gas barrier. In combination with a refrigeration main cycle and a condensation and dehumidification module, a triple protection system of 'active cooling-emergency inertization protection-environmental moisture prevention' is constructed. The application is also applied to new energy electric vehicle power batteries, 5G base station standby power supplies, satellite and space station energy storage systems and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to battery thermal management technology, in particular to a supercritical carbon dioxide phase change cooling thermal prevention and control system for energy storage and power batteries and a control method thereof. BACKGROUND

[0002] A large amount of heat is generated in the charging and discharging process of lithium iron phosphate batteries. If the heat is not dissipated in time, it may lead to thermal runaway, affecting the performance and life of the battery. The traditional air-cooled or liquid-cooled system has low heat dissipation efficiency, high energy consumption, and insufficient humidity control. Supercritical carbon dioxide (sCO2) has high thermal conductivity, low viscosity, and easy compression, making it suitable for efficient thermal management. The present application combines sCO2 phase change cooling and condensation dehumidification technology to provide an efficient, energy-saving, and reliable battery cooling solution.

[0003] The existing energy storage battery and power battery thermal management technology generally has low heat dissipation efficiency, high energy consumption, and insufficient temperature control accuracy: the traditional air-cooled system has a low heat exchange coefficient (about only 5-50 W / (m 2 ·K), which is difficult to cope with high-rate charging and discharging conditions; the liquid-cooled system improves the heat exchange efficiency (about 50-5000 W / (m 2 ·K), but has the problems of high pump power loss, easy leakage of cooling liquid, and high system complexity; phase change material cooling faces the bottleneck of low thermal conductivity, limited phase change latent heat, and non-reusable; and heat pipe technology is limited by short heat transfer distance and one-way heat transfer. In contrast, the present application uses supercritical carbon dioxide phase change cooling technology, which has a much higher heat exchange coefficient than traditional methods; the system realizes the reuse of working medium through closed-loop circulation; the integrated emergency injection system can reduce the temperature of the thermal runaway area to the normal range within a few seconds, and the inert gas environment formed can effectively block the spread of combustion; the heat recovery system further improves the waste heat utilization rate, achieving the coordinated optimization of heat dissipation efficiency, safety, and energy utilization rate.

[0004] Carbon dioxide as a natural working medium has a global warming potential (GWP) of only 1, much lower than commonly used HFC refrigerants. The system does not produce any ozone-depleting substances during operation, and there is no risk of traditional refrigerant leakage. The entire cycle is completely closed, with no wastewater discharge, meeting the most stringent environmental protection standards. The transcritical carbon dioxide system has a high energy efficiency ratio, and due to its superior thermodynamic properties, it can complete the refrigeration process at a lower energy input. Compared with traditional refrigerants, the working pressure of the carbon dioxide system is relatively low, which can reduce equipment wear and tear and improve the service life of the system; it has high heat exchange efficiency in the transcritical region and can maintain good refrigeration efficiency in high-temperature environments.

[0005] The existing battery thermal management system directly discharges the waste heat generated by the battery system without utilization, causing huge energy waste. And the traditional heat dissipation method (such as air cooling / liquid cooling) needs to consume part of the circulating energy for forced convection or pumping coolant, further reducing the overall energy efficiency of the system. And in low temperature environment, the discharge of waste heat will cause the battery pack to be insufficiently preheated, causing the increase of electrolyte viscosity and the decrease of lithium ion diffusion coefficient, which seriously affects the battery performance.

[0006] The temperature regulation of the traditional battery thermal management system lags behind, and the passive heat dissipation method cannot dynamically adjust according to the working conditions. When sudden large-rate charging and discharging occurs (more than 2C), the insufficient heat dissipation capacity may cause the local temperature to rise by more than 10℃, accelerating the aging of the battery.

[0007] The air-cooled air conditioning type thermal management system can effectively control humidity but has great energy consumption, and the liquid cooling type and phase change type thermal management system lack humidity control. The humid air in the environment carries a large amount of water, which is easy to form condensation in the battery cabin (especially when the relative humidity is >60%, the risk is very significant), causing electrode corrosion and insulation failure.

[0008] The space utilization of the traditional scheme is low. In order to meet the heat dissipation demand, the battery spacing often needs to be increased, resulting in the decrease of volume energy density. On the other hand, when thermal runaway occurs, it is difficult to quickly establish an inert gas protection environment. The response time of the traditional fire extinguishing system is >30 seconds, which is difficult to stop the spread of heat. SUMMARY

[0009] In view of the problems existing in the prior art, the present application provides a supercritical carbon dioxide phase change cooling thermal prevention and control system for energy storage and power batteries and a control method thereof.

[0010] One object of the present application is to provide a supercritical carbon dioxide phase change cooling thermal prevention and control system for energy storage and power batteries.

[0011] The supercritical carbon dioxide phase change cooling thermal prevention and control system for energy storage and power batteries comprises a refrigeration main cycle, a condensation and dehumidification module and a liquid storage tank. The refrigeration main cycle comprises a compressor unit, a non-phase change heat exchanger, a regenerator, a throttling device, first and second gas-liquid separators, flow control valves, a phase change evaporation module and a flow control module. The condensation and dehumidification module comprises an air-cooled condensation module and a secondary phase change condensation module.

[0012] The gas phase outlet of the regenerator and the outlet of the secondary phase change condensing module are connected to the low pressure side of the compressor set, the high pressure side of the compressor set is connected to the CO2 inlet of the non-phase change heat exchanger; the CO2 outlet of the non-phase change heat exchanger is connected to the supercritical inlet of the regenerator, the supercritical inlet and the supercritical outlet of the regenerator are communicated by a supercritical pipeline, the supercritical outlet of the regenerator is connected to the gas-liquid two-phase inlet of the first gas-liquid separator by a throttling device; the gas phase outlet of the first gas-liquid separator is connected to the gas-liquid two-phase inlet of the second gas-liquid separator; the liquid phase outlet of the first gas-liquid separator is connected to the inlet of the phase change evaporation module by a flow control valve, the phase change evaporation module is close to the outer wall of the battery pack; the outlet of the phase change evaporation module is connected to the gas-liquid two-phase inlet of the second gas-liquid separator, the liquid phase outlet of the second gas-liquid separator is connected to the inlet of the secondary phase change condensing module of the condensing and dehumidifying module; the gas phase outlet of the second gas-liquid separator is connected to the inlet of the air-cooled condensing module of the condensing and dehumidifying module; the outlet of the air-cooled condensing module is connected to the gas phase inlet of the regenerator; the gas phase outlet and the gas phase inlet of the regenerator are communicated by a gas phase pipeline, and the gas phase pipeline of the regenerator is not communicated with the supercritical pipeline.

[0013] The flow control module is connected to the control end of the flow control valve and the compressor set, respectively.

[0014] The outlet of the liquid storage tank is connected to the gas-liquid two-phase inlet of the first gas-liquid separator by a first isolation valve, and the first isolation valve is connected to the flow control module.

[0015] Further, the application further comprises an oil separator arranged between the high pressure side of the compressor set and the non-phase change heat exchanger, the supercritical CO2 after passing through the compressor set becomes high-temperature and high-pressure, and the oil separator separates the lubricating oil in the compressor set from the CO2, so as to avoid affecting the subsequent fluid flow and heat exchange process.

[0016] The compressor set adopts a plurality of parallel compressors.

[0017] The phase-change heat exchanger adopts a heat recovery heat exchanger; the heat recovery heat exchanger is in communication with the inlet and outlet of the heat carrier through a heat carrier pipeline, the heat carrier flows in the heat carrier pipeline, the heat carrier is water or air, the CO2 inlet and outlet are in communication through a CO2 pipeline, the CO2 flows in the CO2 pipeline, and the heat carrier pipeline and the CO2 pipeline are not in communication; in the heat recovery heat exchanger, the positions of the CO2 inlet and outlet and the heat carrier inlet and outlet are reversed, the flow directions of the CO2 and the heat carrier are reversed in the heat recovery heat exchanger, and the sCO2 and the heat carrier exchange heat in a counter-flow heat exchange mode, so that the heat of the data center is properly utilized by the external heat-consuming end. The heat recovery heat exchanger is connected to an external heat recovery system through the heat carrier inlet and outlet; the heat recovery system includes a summer water heating system and a winter low-temperature heating module connected in parallel through a pipeline, a first stop valve and a second stop valve are arranged on the inlet pipelines of the summer water heating system and the winter low-temperature heating module, a third stop valve is arranged on the pipeline after the outlets of the summer water heating system and the winter low-temperature heating module are connected in parallel, the third stop valve is connected to the heat carrier inlet of the heat recovery heat exchanger through a pipeline, the heat carrier outlet of the heat recovery heat exchanger is connected to the first stop valve and the second stop valve in parallel through a pipeline, and the first to third stop valves are connected to a flow control module; when the summer ambient temperature is high, the first and third stop valves are opened and the second stop valve is closed, and the heat generated from the battery pack is used for heating industrial water or drinking water; in a winter low-temperature environment, the second and third stop valves are opened and the first stop valve is closed, the ion diffusion coefficient in the electrode and the electrolyte sharply decreases, which causes a sudden increase in polarization resistance and a decrease in battery capacity, so the heat generated by the battery pack during operation is transported to the nearby energy storage battery module in a non-operating state, the battery operation start temperature is improved, and the battery capacity and the charge-discharge efficiency are maintained; the waste heat utilization rate is improved, and the heat dissipation efficiency, safety and energy utilization rate are synergistically optimized.

[0018] The throttling device adopts a fixed throttling device, an adjustable throttling device, an electronic throttling device, an intelligent throttling device, a porous plug throttling device or a labyrinth throttling device.

[0019] The phase-change evaporation module includes a plurality of groups of parallel cooling solid-type evaporators, and each evaporator is attached to the outer side wall of the battery pack.

[0020] In the condensation and dehumidification module, the air-cooled condensation module uses a heat exchanger with air-gas heat exchange function and capable of discharging condensed water, specifically a plate heat exchanger, a plate-fin heat exchanger, a tube-shell heat exchanger or a finned tube bundle heat exchanger, and uses low-temperature gaseous CO2 to exchange heat with humid air to condense the moisture in the humid air; the secondary phase change condensation module uses a cooling air type evaporator to heat and vaporize the liquid phase CO2 that is not completely vaporized in the previous link through the secondary phase change condensation mode, and to heat the liquid phase CO2 to a high temperature state consistent with the temperature of the external air, thereby removing the water vapor in the environment while cooling the CO2 to prevent the battery system from being damp, and then directly delivering the CO2 to the compressor to start the next cycle. The supercritical carbon dioxide compression-expansion phase change cycle is used to achieve efficient heat dissipation, and the condensation and dehumidification module is used to accurately control the environmental humidity, thereby ensuring the safe and stable operation of the battery system under the best working condition.

[0021] Further, the application also includes a thermal runaway emergency injection system including a temperature sensor, a second isolation valve and a CO2 injection port; wherein the temperature sensor is installed near the electrode terminal of the battery pack; the outlet of the liquid storage tank is connected to a plurality of parallel CO2 injection ports through the second isolation valve; the plurality of parallel CO2 injection ports are aligned with the outer wall of the battery pack; the temperature sensor and the second isolation valve are respectively connected to the flow control module; the temperature sensor serves as an emergency monitoring device, and when the battery pack has a thermal runaway abnormal condition, the flow control module detects that the temperature is too high through the temperature sensor, closes the first isolation valve, opens the second isolation valve, and the liquid phase CO2 is directly injected to the surface of the thermal runaway battery pack through the CO2 injection port for emergency cooling, the refrigerant absorbs a large amount of heat to vaporize, and forms a gaseous CO2 atmosphere to prevent further deterioration of the thermal runaway.

[0022] Another object of the application is to provide a control method of the supercritical carbon dioxide phase change cooling thermal prevention and control system for energy storage and power battery.

[0023] The control method of the supercritical carbon dioxide phase change cooling thermal prevention and control system for energy storage and power battery of the application comprises the following steps:

[0024] 1) The gaseous CO2 from the gas phase pipeline of the regenerator and the secondary phase change condensation module of the condensation and dehumidification module enters the compressor set, is pressurized and heated in the compressor set, becomes high-temperature and high-pressure supercritical carbon dioxide sCO2, has high density and high heat capacity, and the temperature and pressure of the high-pressure side of the compressor set are increased;

[0025] 2) The carbon dioxide is transmitted to the non-phase change heat exchanger, the non-phase change heat exchanger gives the heat extracted by the thermal management system to the outside, performs preliminary cooling, reduces the temperature of the sCO2 but still maintains the supercritical state, and improves the energy efficiency;

[0026] 3) The sCO2 after heat exchange enters the supercritical pipeline of the regenerator and exchanges heat with the returned gaseous CO2 in the gaseous pipeline, further reducing the temperature while still maintaining the supercritical state and lower temperature; the phase-change heat exchanger and the regenerator work together to realize energy cascade utilization;

[0027] 4) The low-temperature sCO2 flows through the throttling device, and the sCO2 is depressurized to the subcritical region, part of the CO2 is liquefied, and a gas-liquid two-phase state is formed;

[0028] 5) The gas-liquid two-phase CO2 after the throttling device enters the first gas-liquid separator, the liquid-phase CO2 is transmitted to the phase-change evaporation module through the flow control valve by separation and sedimentation, the gaseous CO2 rises and is transmitted to the second gas-liquid separator, and the liquid phase and the gas phase of CO2 are separated; under normal working conditions, the first isolation valve of the flow control module is opened, and the flow control module dynamically supplements the dissipated CO2 from the liquid tank to the first gas-liquid separator according to the CO2 charging amount in the cycle;

[0029] 6) The flow control module accurately controls the flow control valve to dynamically adjust the flow of the liquid-phase CO2 according to the charging and discharging rate of the battery pack, to ensure the evaporation efficiency and transmit to the phase-change evaporation module;

[0030] 7) The phase-change evaporation module absorbs heat by evaporation of the liquid-phase CO2 to cool the battery pack, and becomes gaseous CO2, and the gaseous CO2 after refrigeration with a small amount of liquid-phase CO2 is transmitted to the second gas-liquid separator;

[0031] 8) The second gas-liquid separator separates the gaseous CO2 and the liquid-phase CO2, and then transmits the gaseous CO2 to the secondary phase-change condensation module of the condensation and dehumidification module, and transmits the liquid-phase CO2 to the gas-cooling condensation module of the condensation and dehumidification module;

[0032] 9) The secondary phase-change condensation module exchanges heat with the wet air to condense the water in the wet air, and transmits the gaseous CO2 to the gaseous pipeline of the regenerator; the gas-cooling condensation module gasifies the liquid-phase CO2 that is not completely gasified in the previous link to absorb heat and raise the temperature to a higher temperature state consistent with the temperature of the external air, and then directly delivers to the compressor;

[0033] 10) The gaseous CO2 exchanges heat with the sCO2 in the gaseous pipeline and the supercritical pipeline of the regenerator, is preheated and returned to the compressor to complete the closed-loop cycle.

[0034] In step 1), the compressor compresses the carbon dioxide working medium to a supercritical state: pressure > 7.38 MPa, temperature > 31.1℃.

[0035] Before entering the phase-change heat exchanger, the high-temperature and high-pressure supercritical CO2 after the compressor set passes through the oil separator to separate the lubricating oil in the compressor set from the CO2, to avoid affecting the subsequent fluid flow and heat exchange process.

[0036] In step 2), the phase-change heat exchanger adopts a heat recovery heat exchanger, the heat carrier inlet and outlet of the heat recovery heat exchanger are connected to an external heat recovery system, a high-efficiency counter-flow heat exchange method is adopted, the residual cold energy of the low-temperature gas-phase CO2 returned from the phase-change heat dissipation module is recovered for pre-cooling the CO2 about to enter the throttling device; when the ambient temperature is high in summer, the first and third stop valves are opened and the second stop valve is closed, the heat generated from the battery pack is used for heating industrial water or drinking water; in winter, the second and third stop valves are opened and the first stop valve is closed, the ion diffusion coefficient in the electrode and electrolyte sharply decreases, which will cause the polarization resistance to suddenly increase and the battery capacity to decrease, so the heat generated from the battery pack in the working process is transported to the nearby energy storage battery module in a non-working state to improve the battery operation starting temperature and maintain the battery capacity and charge-discharge efficiency; the waste heat utilization rate is improved, and the heat dissipation efficiency, safety and energy utilization rate are synergistically optimized.

[0037] In step 4), the throttling device reduces the sCO2 pressure by 3-5 MPa.

[0038] In step 6), the flow control module adjusts the CO2 flow in seconds according to the charge-discharge rate of the battery pack; when the charge-discharge rate increases or the temperature rises due to changes in seasonal environment, etc., the flow control module immediately increases the CO2 flow to ensure that there is enough liquid-phase CO2 to participate in phase-change heat absorption; when the charge-discharge rate decreases or the temperature decreases due to changes in seasonal environment, etc., the CO2 flow is automatically reduced to reduce energy consumption; this intelligent adjustment mechanism not only avoids the common problem of overcooling or overheating in traditional cooling systems, but also enables the thermal management system to always work at the best efficiency point, while controlling the temperature fluctuation within ±2℃. Further, a first temperature threshold and a second temperature threshold are set, the second temperature threshold is greater than the first temperature threshold, and the temperature sensor monitors the temperature of the battery pack in real time; when the temperature of the battery pack is higher than the first temperature threshold, the flow control module controls the flow control valve to increase the flow of liquid-phase CO2; when the battery pack has an abnormal condition of thermal runaway, the flow control module detects that the temperature is higher than the second temperature threshold through the temperature sensor, closes the first isolation valve and opens the second isolation valve, and the liquid-phase CO2 is directly sprayed to the surface of the battery pack in thermal runaway for emergency cooling, the refrigerant absorbs a large amount of heat to vaporize and form a gas-phase CO2 atmosphere to prevent further deterioration of the thermal runaway. The first threshold is 70-90℃, and the second temperature threshold is 90-140℃. The advantages of the present application are:

[0039] (1) Make full use of the special thermal property change of supercritical carbon dioxide near the critical point (31.1℃, 7.38MPa), which exhibits extremely high heat transfer coefficient (up to 3-5 times of water) and significant heat capacity change characteristics in the near-critical region. The required heat exchanger volume is greatly reduced, only about 1 / 3 of the traditional water cooling system, but the heat dissipation capacity is increased by 50%. This unique physical property enables the thermal management system to achieve extremely high heat dissipation efficiency;

[0040] (2) Adopt multi-stage energy recovery architecture to realize gradient utilization of energy through the synergistic effect of heat exchangers and regenerators. The phase change evaporation module effectively solves the high power density heat dissipation problem;

[0041] (3) The thermal management system is equipped with a flow control module to match the charging and discharging power in real time, and cooperates with the multi-stage phase change design to dynamically adjust the heat dissipation power, with short response time, completely solving the problem of undercooling or insufficient heat dissipation of traditional systems;

[0042] (4) Use natural working medium CO2 (GWP = 1, ODP = 0), which is completely free of harmful substances such as freon. The thermal management system is designed to be completely closed and circulating, achieving zero wastewater discharge, with extremely low operating noise, ensuring the stability of cooling effect, and maximizing the energy utilization efficiency of the system. Compared with traditional refrigerants, carbon emissions are reduced by more than 60%, fully meeting the most stringent environmental protection regulations;

[0043] (5) Modular design makes the thermal management system occupy very low area, with high power density per battery cluster. The mechanical components involved in the installation and cooperation of each module are standard components, and the standardized interface design facilitates installation and maintenance, supporting flexible plugging and replacement of components. It can operate stably in the temperature range of 0-100℃, especially suitable for severe conditions such as variable rate and frequent charging and discharging;

[0044] (6) Integrated thermal runaway emergency system can complete liquid CO2 direct injection and form inert gas barrier in seconds, and cooperate with refrigeration main cycle and condensation dehumidification module to build a "active cooling-emergency inertization protection-environmental moisture protection" triple protection system;

[0045] (7) In addition to large-scale lithium iron phosphate battery energy storage stations, the thermal management system can also be integrated into battery box to chassis (CTC, Cell to Chassis) battery chassis integrated design for new energy electric vehicle power battery cooling, as well as 5G base station backup power, satellite and space station energy storage system, etc. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a schematic diagram of an embodiment of the supercritical carbon dioxide phase change cooling thermal control system for energy storage and power battery of the present application. DETAILED DESCRIPTION

[0047] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0048] like Figure 1 As shown, the energy storage and power supercritical carbon dioxide phase change cooling thermal control system of this embodiment includes: a refrigeration main cycle, a condensation dehumidification module, a liquid storage tank, a thermal runaway emergency injection system, and a heat recovery system; wherein, the refrigeration main cycle includes a compressor unit, an oil separator, a phase change heat exchanger, a regenerator, a throttling device, first and second gas-liquid separators, a flow control valve, a phase change evaporation module, and a flow control module; the condensation dehumidification module includes an air-cooled condensation module and a secondary phase change condensation module;

[0049] The gas phase outlet of the regenerator and the outlet of the secondary phase change condensation module are connected to the low-pressure side of the compressor unit. The high-pressure side of the compressor unit is connected to the CO2 inlet of the phaseless heat exchanger via an oil separator. The CO2 outlet of the phaseless heat exchanger is connected to the supercritical inlet of the regenerator. The supercritical inlet and supercritical outlet of the regenerator are internally connected via a supercritical pipe. The supercritical outlet of the regenerator is connected to the gas-liquid two-phase inlet of the first gas-liquid separator via a throttling device. The gas phase outlet of the first gas-liquid separator is connected to the gas-liquid two-phase inlet of the second gas-liquid separator. The liquid phase outlet of the first gas-liquid separator is connected via... The flow control valve is connected to the inlet of the phase change evaporation module, which is in close contact with the outer wall of the battery pack. The outlet of the phase change evaporation module is connected to the gas-liquid two-phase inlet of the second gas-liquid separator. The liquid phase outlet of the second gas-liquid separator is connected to the inlet of the secondary phase change condensation module of the condensation dehumidification module. The gas phase outlet of the second gas-liquid separator is connected to the inlet of the gas-cooled condensation module of the condensation dehumidification module. The outlet of the gas-cooled condensation module is connected to the gas phase inlet of the regenerator. The gas phase outlet and gas phase inlet of the regenerator are connected internally through a gas phase pipe, but the gas phase pipe of the regenerator is not connected to the supercritical pipe.

[0050] The flow control module is connected to the control terminals of the flow control valve and the compressor unit, respectively.

[0051] The outlet of the storage tank is connected to the gas-liquid two-phase inlet of the first gas-liquid separator via a first isolation valve, and the first isolation valve is connected to the flow control module;

[0052] The thermal runaway emergency injection system includes a temperature sensor, a second isolation valve, and CO2 nozzles; wherein, the temperature sensor is installed near the electrode terminals of the battery pack; the outlet of the reservoir is connected to multiple parallel CO2 nozzles through the second isolation valve; the multiple parallel CO2 nozzles are aligned with the outer wall of the battery pack; the temperature sensor and the second isolation valve are respectively connected to the flow control module;

[0053] The phase-change heat exchanger is a heat recovery heat exchanger. The inlet and outlet of the heat transfer medium are connected via a heat transfer medium pipe, and the heat transfer medium flows inside the pipe. The heat transfer medium can be water or air. The inlet and outlet of CO2 are connected via a CO2 pipe, and CO2 flows inside the CO2 pipe. The heat transfer medium pipe and the CO2 pipe are not connected. Inside the heat recovery heat exchanger, the CO2 inlet and outlet are in the opposite direction to the heat transfer medium inlet and outlet, and the flow direction of CO2 is opposite to the flow direction of the heat transfer medium. The heat exchange between CO2 and the heat transfer medium is a counter-current heat exchange method, and the data is transferred to the external heat-using end. The heat in the center is properly utilized; the inlet and outlet of the heat recovery heat exchanger are respectively connected to the external heat recovery system; the heat recovery system includes a summer water heating system and a winter low-temperature heating module connected in parallel through pipes, with a first shut-off valve and a second shut-off valve on the inlet pipes of the summer water heating system and the winter low-temperature heating module, respectively, and a third shut-off valve is installed on the pipe after the outlets of the summer water heating system and the winter low-temperature heating module are connected in parallel through pipes. The third shut-off valve is connected to the heat transfer medium inlet of the heat recovery heat exchanger through pipes, and the heat transfer medium outlet of the heat recovery heat exchanger is connected to the first and second shut-off valves connected in parallel through pipes. The first to third shut-off valves are respectively connected to the flow control module.

[0054] The control method of the supercritical carbon dioxide phase change cooling thermal control system for energy storage and power batteries in this embodiment, specifically for lithium iron phosphate batteries, includes the following steps:

[0055] 1) Gas-phase CO2 from the gas-phase pipes of the regenerator and the secondary phase-change condensation module of the condensation dehumidification module enters the compressor unit, where it is pressurized and heated, becoming high-temperature, high-pressure supercritical carbon dioxide (sCO2), with a pressure >

[0056] At 7.38 MPa and a temperature of 55–85°C, it possesses high density and high heat capacity, increasing the high-pressure side temperature and pressure of the compressor unit. After passing through the compressor unit, it becomes high-temperature and high-pressure supercritical CO2. The oil separator separates the lubricating oil in the compressor unit from the CO2, avoiding affecting the subsequent fluid flow and heat exchange process.

[0057] 2) Carbon dioxide is transferred to the heat recovery heat exchanger, which transfers the heat extracted by the thermal management system to the outside for preliminary cooling, reducing the CO2 temperature (generally to 35-50℃) while still maintaining the supercritical state, thus improving energy efficiency.

[0058] When the ambient temperature is high in summer, the first and third stop valves are opened and the second stop valve is closed, and the heat generated from the battery pack is used for heating industrial water or drinking water; in winter, the second and third stop valves are opened and the first stop valve is closed, and the ion diffusion coefficient in the electrode and electrolyte decreases sharply, which will cause the polarization resistance to increase sharply and the battery capacity to decrease, so the heat generated by the battery pack during operation is transported to the nearby energy storage battery module which is not in operation, to improve the battery operation starting temperature and maintain the battery capacity and charge-discharge efficiency; the waste heat utilization rate is improved, and the heat dissipation efficiency, safety and energy utilization rate are synergistically optimized;

[0059] 3) The heat-exchanged sCO2 enters the supercritical pipeline of the regenerator and exchanges heat with the returned gaseous CO2 in the pipeline, further reducing the temperature and still maintaining the supercritical state and a lower temperature (but not lower than 32℃); the synergistic effect of the heat recovery heat exchanger and the regenerator realizes energy cascade utilization;

[0060] 4) The low-temperature sCO2 flows through the throttling device, and the sCO2 is depressurized to the subcritical region of 4 MPa, part of the CO2 is liquefied, and a gas-liquid two-phase state is formed;

[0061] 5) The gas-liquid two-phase CO2 after the throttling device enters the first gas-liquid separator, the liquid phase CO2 is transmitted to the phase change evaporation module through the flow control valve by separation and sedimentation, and the gaseous CO2 rises and is transmitted to the second gas-liquid separator, and the liquid phase and the gaseous phase of CO2 are separated; under normal working conditions, the first isolation valve of the flow control module is opened, and the flow control module dynamically supplements the dissipated CO2 from the liquid storage tank to the first gas-liquid separator according to the CO2 charging amount; the CO2 charging amount is detected by a flow sensor connected to the flow control module, or by manual detection;

[0062] 6) The set charge-discharge rate is transmitted to the flow control module in real time, and the flow control module accurately controls the flow control valve to dynamically adjust the flow of the liquid phase CO2 according to the charge-discharge rate of the battery pack, and the flow of CO2 is adjusted in seconds and transmitted to the phase change evaporation module; when the charge-discharge rate increases, or the temperature rises due to changes in seasonal environment, etc., the flow control module immediately increases the CO2 flow to ensure that there is enough liquid phase CO2 to participate in the phase change heat absorption; when the charge-discharge rate decreases, or the temperature decreases due to changes in seasonal environment, etc., the CO2 flow will be automatically reduced to reduce energy consumption; this intelligent adjustment mechanism not only avoids the common problems of overcooling or overheating in traditional cooling systems, but also enables the thermal management system to always work at the best efficiency point, and at the same time, the temperature of the battery pack (the battery pack temperature control interval is selected to be 25-38℃) is controlled within ±2℃ to ensure the evaporation efficiency;

[0063] 7) The phase change evaporation module absorbs heat by evaporating liquid CO2, cools the battery pack, and becomes gaseous CO2. After cooling, the gaseous CO2 containing a small amount of liquid CO2 is transported to the second gas-liquid separator;

[0064] 8) The second gas-liquid separator separates the gaseous CO2 from the liquid CO2, and then transports the gaseous CO2 to the secondary phase change condensation module of the condensation and dehumidification module, and transports the liquid CO2 to the gas cooling condensation module of the condensation and dehumidification module;

[0065] 9) The secondary phase change condensation module exchanges heat with the humid air to condense the water in the humid air, and the gaseous CO2 is transported to the gas phase pipeline of the heat regenerator. The gas cooling condensation module vaporizes the liquid CO2 that is not completely vaporized in the previous step, absorbs heat, and warms up to a higher temperature state consistent with the temperature of the outside air, and is then directly transported to the compressor;

[0066] 10) The gaseous CO2 exchanges heat with the sCO2 in the supercritical pipeline in the gas phase pipeline of the heat regenerator, is preheated, and is returned to the compressor to complete the closed loop cycle;

[0067] 11) The temperature sensor monitors the temperature of the battery pack in real time. When the temperature of the battery pack is higher than the first temperature threshold of 80℃, the flow control module controls the flow control valve to increase the flow of liquid CO2. When the battery pack has a thermal runaway abnormal condition, the flow control module detects that the temperature is higher than the second temperature threshold of 100℃ through the temperature sensor, closes the first isolation valve, opens the second isolation valve, and the liquid CO2 is directly sprayed onto the surface of the thermal runaway battery pack through the CO2 spray port for emergency cooling. The refrigerant absorbs a large amount of heat and vaporizes to form a gaseous CO2 atmosphere, preventing further deterioration of the thermal runaway.

[0068] Finally, it should be noted that the purpose of publishing the embodiments is to help further understand the present application, but those skilled in the art can understand that various replacements and modifications are possible without departing from the spirit and scope of the present application and the appended claims. Therefore, the present application should not be limited to the disclosed content of the embodiments, and the scope of protection claimed by the present application is defined by the scope defined by the claims.

Claims

1. A supercritical carbon dioxide phase change cooling thermal control system for energy storage and power batteries, characterized in that, The thermal control system includes: a refrigeration main cycle, a condensation dehumidification module, and a liquid storage tank; wherein, the refrigeration main cycle includes a compressor unit, a phase change heat exchanger, a regenerator, a throttling device, first and second gas-liquid separators, a flow control valve, a phase change evaporation module, a condensation dehumidification module, and a flow control module; the condensation dehumidification module includes an air-cooled condensation module and a secondary phase change condensation module; The gas phase outlet of the regenerator and the outlet of the secondary phase change condensation module are connected to the low-pressure side of the compressor unit, and the high-pressure side of the compressor unit is connected to the CO2 inlet of the phase-free heat exchanger. The CO2 outlet of the phase-free heat exchanger is connected to the supercritical inlet of the regenerator. The supercritical inlet and supercritical outlet of the regenerator are internally connected through a supercritical pipe. The supercritical outlet of the regenerator is connected to the gas-liquid two-phase inlet of the first gas-liquid separator through a throttling device. The gas phase outlet of the first gas-liquid separator is connected to the gas-liquid two-phase inlet of the second gas-liquid separator. The liquid phase outlet of the first gas-liquid separator is connected to the inlet of the phase change evaporation module through a flow control valve. The phase change evaporation module is in close contact with the outer wall of the battery pack. The phase change evaporation module absorbs heat through the evaporation of liquid CO2, cools the battery pack, and turns into gas phase. CO2, after cooling, is transported in a gaseous phase mixed with a small amount of liquid CO2 to the second gas-liquid separator. The outlet of the phase change evaporation module is connected to the gas-liquid two-phase inlet of the second gas-liquid separator. The liquid phase outlet of the second gas-liquid separator is connected to the inlet of the secondary phase change condensation module of the condensation dehumidification module. The secondary phase change condensation module vaporizes the incompletely vaporized liquid CO2 from the previous stage, absorbs heat, and raises its temperature to a higher level consistent with the ambient air temperature. The gas phase outlet of the second gas-liquid separator is connected to the inlet of the air-cooled condensation module of the condensation dehumidification module. The outlet of the air-cooled condensation module is connected to the gas phase inlet of the regenerator. The gas phase outlet and gas phase inlet of the regenerator are connected internally through a gas phase pipe, but the gas phase pipe of the regenerator is not connected to the supercritical pipe. The flow control module is connected to the control terminals of the flow control valve and the compressor unit, respectively. The outlet of the storage tank is connected to the gas-liquid two-phase inlet of the first gas-liquid separator via the first isolation valve, and the first isolation valve is connected to the flow control module.

2. The thermal control system as described in claim 1, characterized in that, It also includes an oil separator, which is located between the high-pressure side of the compressor unit and the phase-change heat exchanger. After passing through the compressor unit, the supercritical CO2, which becomes high temperature and high pressure, passes through the oil separator to separate the lubricating oil in the compressor unit from the CO2.

3. The thermal control system as described in claim 1, characterized in that, The phase-change heat exchanger employs a heat recovery heat exchanger. The inlet and outlet of the heat transfer medium are connected via a heat transfer medium pipe, through which the heat transfer medium flows. The heat transfer medium can be water or air. The inlet and outlet of CO2 are connected via a CO2 pipe, through which CO2 flows. The heat transfer medium pipe and the CO2 pipe are not connected. Within the heat recovery heat exchanger, the positions of the CO2 inlet and outlet are opposite to those of the heat transfer medium inlet and outlet, and the flow direction of CO2 is opposite to that of the heat transfer medium. The heat exchange between CO2 and the heat transfer medium is a counter-current heat exchange method. The heat recovery heat exchanger's heat transfer medium inlet and outlet are respectively connected to an external heat recovery system. The heat recovery system includes a summer water heating system and a winter low-temperature heating module connected in parallel via pipes. A first shut-off valve and a second shut-off valve are respectively installed on the inlet pipes of the summer water heating system and the winter low-temperature heating module. A third shut-off valve is installed on the pipe after the summer water heating system and the winter low-temperature heating module are connected in parallel via pipes. The third shut-off valve is connected to the heat transfer medium inlet of the heat recovery heat exchanger via pipes. The heat transfer medium outlet of the heat recovery heat exchanger is connected to the first and second shut-off valves connected in parallel via pipes. The first to third shut-off valves are respectively connected to a flow control module.

4. The thermal control system as described in claim 1, characterized in that, The throttling device can be a fixed throttling device, an adjustable throttling device, an electronic throttling device, an intelligent throttling device, a multi-hole plug-type throttling device, or a labyrinth-type throttling device.

5. The thermal control system as described in claim 1, characterized in that, The air-cooled condensing module is a heat exchanger that uses air-to-air heat exchange and can discharge condensate.

6. The thermal control system as described in claim 1, characterized in that, The secondary phase change condensation module uses a cooled air-type evaporator.

7. The thermal control system as described in claim 1, characterized in that, It also includes a thermal runaway emergency injection system, which includes a temperature sensor, a second isolation valve, and CO2 nozzles; wherein, the temperature sensor is installed on the battery pack; the outlet of the liquid storage tank is connected to multiple parallel CO2 nozzles through the second isolation valve; the multiple parallel CO2 nozzles are aligned with the outer wall of the battery pack; the temperature sensor and the second isolation valve are respectively connected to the flow control module.

8. A control method for a supercritical carbon dioxide phase change cooling thermal control system for energy storage and power batteries as described in claim 1, characterized in that, The control method includes the following steps: 1) The gaseous CO2 from the gas phase pipe of the regenerator and the secondary phase change condensation module of the condensation dehumidification module enters the compressor unit. In the compressor unit, it is pressurized and heated to become high-temperature and high-pressure supercritical carbon dioxide sCO2, which has high density and high heat capacity, and the high-pressure side temperature and pressure of the compressor unit are increased. 2) Carbon dioxide is transferred to the phaseless heat exchanger, which then transfers the heat extracted by the thermal management system to the outside for initial cooling, reducing the CO2 temperature but still maintaining it in a supercritical state, thereby improving energy efficiency. 3) After heat exchange, the sCO2 enters the supercritical pipe of the regenerator and exchanges heat with the gas phase CO2 returning from the gas phase pipe, further cooling down while still maintaining the supercritical state and at an even lower temperature; without the synergistic effect of the phase change heat exchanger and the regenerator, energy is utilized in a cascade manner. 4) Low-temperature sCO2 flows through the throttling device, where the sCO2 pressure is reduced to the subcritical region, and some of the CO2 liquefies, forming a gas-liquid two-phase state. 5) After passing through the throttling device, the two-phase CO2 enters the first gas-liquid separator. The liquid phase CO2 is separated and settled and then transferred to the phase change evaporation module via the flow control valve. The gas phase CO2 rises and is transferred to the second gas-liquid separator, where the liquid and gas phases of CO2 are separated. 6) The flow control module precisely controls the flow control valve to dynamically adjust the flow rate of liquid CO2 according to the charging and discharging rate of the battery pack, and transmits the data to the phase change evaporation module. 7) The phase change evaporation module absorbs heat through the evaporation of liquid CO2 to cool the battery pack and turns into gaseous CO2. After cooling, the gaseous CO2 mixed with a small amount of liquid CO2 is transported to the second gas-liquid separator. 8) The second gas-liquid separator separates gaseous CO2 and liquid CO2, and then transfers the gaseous CO2 to the secondary phase change condensation module of the condensation and dehumidification module, and transfers the liquid CO2 to the air-cooled condensation module of the condensation and dehumidification module. 9) The secondary phase change condensation module uses low-temperature gaseous CO2 to exchange heat with humid air, causing the moisture in the humid air to condense, and then transfers the gaseous CO2 to the gaseous pipe of the regenerator; the air-cooled condensation module vaporizes the liquid CO2 that is not completely vaporized in the previous stage, absorbs heat, and raises the temperature to a higher temperature state that is consistent with the outside air temperature, and then directly delivers it to the compressor. 10) The gaseous CO2 in the gas phase pipe of the regenerator exchanges heat with the sCO2 in the supercritical pipe. After being preheated, it returns to the compressor to complete the closed-loop cycle.

9. The control method as described in claim 8, characterized in that, In step 2), the phase-change heat exchanger uses a heat recovery heat exchanger. The inlet and outlet of the heat recovery heat exchanger are connected to an external heat recovery system. A high-efficiency counter-current heat exchange method is used to recover the residual cold energy of the low-temperature gaseous CO2 returned from the phase-change heat dissipation module for pre-cooling the CO2 that is about to enter the throttling device. When the ambient temperature is high in summer, the first and third shut-off valves are opened and the second shut-off valve is closed. The heat generated inside the battery pack is used to heat industrial water or drinking water. In the low-temperature environment of winter, the second and third shut-off valves are opened and the first shut-off valve is closed. The heat generated by the battery pack during operation is transported to the nearby battery modules that are not in operation.

10. The control method as described in claim 8, characterized in that, In step 6), the flow control module adjusts the CO2 flow rate in seconds according to the charge and discharge rate of the battery pack; a first temperature threshold and a second temperature threshold are set, the second temperature threshold being greater than the first temperature threshold, and the temperature sensor monitors the temperature of the battery pack in real time; when the temperature of the battery pack is higher than the first temperature threshold, the flow control module controls the flow control valve to increase the flow rate of liquid CO2. When the battery pack experiences thermal runaway, the flow control module detects that the temperature is higher than the second temperature threshold through the temperature sensor. It then closes the first isolation valve and opens the second isolation valve. Liquid CO2 is directly sprayed onto the surface of the thermally runaway battery pack through the CO2 nozzle for emergency cooling. The refrigerant absorbs a large amount of heat and vaporizes, forming a gaseous CO2 atmosphere.

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