Supercritical COphase change cooling heat prevention and control system and method for energy storage and power battery

Abstract

The invention discloses a supercritical CO2 phase change cooling heat prevention and control system and method for an energy storage and power battery. According to the invention, the thermophysical property change of supercritical CO2 near a critical point is utilized, so that the volume is greatly reduced, and extremely high heat dissipation efficiency is realized; a multi-stage energy recovery framework is adopted, and gradient utilization of energy is achieved through the synergistic effect of the heat exchanger and the heat regenerator; the phase change evaporation module effectively solves the problem of high-power-density heat dissipation; the modular design enables the thermal management system to occupy a very small area; the battery can stably operate in an environment temperature range of 0-100 DEG C, and is suitable for harsh working conditions such as variable-rate frequent charging and discharging; a thermal runaway emergency system is integrated, liquid direct injection can be completed within seconds, an inert gas barrier is formed, and a triple protection system of'active cooling-emergency inerting protection-environment moisture prevention 'is constructed in cooperation with a refrigeration main cycle and a condensation dehumidification module; the method is also applied to new energy electric vehicle power batteries, 5G base station standby power supplies, satellite and space station energy storage systems and other scenes.

Description

Technical Field

[0001] The present invention relates to battery thermal management technology, and particularly to a supercritical carbon dioxide phase change cooling thermal prevention and control system for energy storage and power batteries and its control method. Background Art

[0002] During the charging and discharging process of lithium iron phosphate batteries, a large amount of heat is generated. If the heat dissipation is not timely, it may lead to thermal runaway, affecting the battery performance and life. Traditional air-cooling or liquid-cooling systems have problems such as low heat dissipation efficiency, high energy consumption, and insufficient humidity control. Supercritical carbon dioxide (sCO2) has characteristics such as high thermal conductivity, low viscosity, and easy compressibility, which is suitable for efficient thermal management. The present invention combines sCO2 phase change heat dissipation and condensation dehumidification technologies to provide an efficient, energy-saving, and reliable battery heat dissipation solution.

[0003] Existing energy storage battery and power battery thermal management technologies generally have defects such as low heat dissipation efficiency, high energy consumption, and insufficient temperature control accuracy: The heat transfer coefficient of traditional air-cooling systems is low (only about 5 - 50 W / (m 2 ·K)), making it difficult to cope with high-rate charging and discharging conditions; Although the liquid-cooling system has improved the heat transfer efficiency (about 50 - 5000 W / (m 2 ·K)), it has problems such as large pump power loss, easy leakage of the coolant, and high system complexity; Phase change material cooling faces bottlenecks such as low thermal conductivity, limited phase change latent heat, and non-reusability; And the heat pipe technology is limited by the short heat transfer distance and the limitation of one-way heat transfer. In contrast, the present invention adopts supercritical carbon dioxide phase change cooling technology, whose heat transfer coefficient has been greatly improved compared with traditional methods; The system realizes the reuse of the working medium through a closed-loop cycle; The integrated emergency injection system can reduce the temperature of the thermal runaway area to the normal range within seconds, and at the same time, the formed inert gas environment can effectively block the spread of combustion; The waste heat recovery system further improves the waste heat utilization rate, achieving the coordinated optimization of heat dissipation efficiency, safety, and energy utilization rate.

[0004] As a natural working medium, carbon dioxide has a global warming potential (GWP) of only 1, which is much lower than that of commonly used HFC refrigerants. No ozone-depleting substances are generated during the operation of the system, and there is no risk of leakage of traditional refrigerants. The entire circulation process is completely closed, without any wastewater discharge, meeting the strictest environmental protection standards. And the transcritical carbon dioxide system has a relatively high energy efficiency ratio. Due to its excellent thermodynamic properties, it can complete the refrigeration process with 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 extend the life of the system; It has a relatively high heat exchange efficiency in the transcritical range and can maintain good refrigeration performance in high-temperature environments.

[0005] Existing battery thermal management systems directly discharge waste heat generated by the battery system without using it, resulting in significant energy waste. Furthermore, traditional heat dissipation methods (such as air cooling or liquid cooling) require additional circulating energy for forced convection or coolant pumping, further reducing overall system efficiency. Furthermore, in low-temperature environments, discharging waste heat can lead to insufficient preheating of the battery pack, increasing electrolyte viscosity and decreasing the lithium-ion diffusion coefficient, seriously impacting battery performance.

[0006] Traditional battery thermal management systems have a temperature regulation lag, and passive heat dissipation methods cannot be dynamically adjusted according to operating conditions. During sudden high-rate charging and discharging (above 2C), insufficient heat dissipation capacity may cause local temperature rise to exceed 10°C, accelerating battery aging.

[0007] Air-cooled air-conditioning thermal management systems can effectively control humidity but consume extremely high energy. Liquid-cooled and phase-change thermal management systems lack humidity control. The hot and humid air in the environment carries a large amount of moisture, which can easily form condensation in the battery compartment (especially when the relative humidity is >60%, the risk is very significant), causing electrode corrosion and insulation failure.

[0008] Traditional solutions suffer from low space efficiency. To meet heat dissipation requirements, the battery spacing often needs to be increased, resulting in a decrease in volumetric energy density. Furthermore, in the event of thermal runaway, an inert gas environment cannot be quickly established. Traditional fire extinguishing systems have a response time of >30 seconds, making it difficult to prevent the spread of heat. Summary of the Invention

[0009] In response to the above problems existing in the prior art, the present invention proposes a supercritical carbon dioxide phase change cooling heat prevention and control system for energy storage and power batteries and a control method thereof.

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

[0011] The energy storage and power battery supercritical carbon dioxide phase change cooling heat control system of the present invention includes: a refrigeration main cycle, a condensation and 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 and a flow control module; the condensation and dehumidification module includes 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 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, and the supercritical inlet of the regenerator is connected to the inside of the supercritical outlet through a supercritical pipe, and 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 ... through a flow control device. The control valve is connected to the inlet of the phase change evaporation module, and 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, and 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 and dehumidification module; the gas phase outlet of the second gas-liquid separator is connected to the inlet of the air-cooled condensation module of the condensation and 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 the gas phase inlet of the regenerator are connected internally through a gas phase pipeline, and the gas phase pipeline of the regenerator is not connected to the supercritical pipeline;

[0013] The flow control module is connected to the control end of the flow control valve and the compressor unit respectively;

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

[0015] Furthermore, the present invention also includes an oil separator, which is arranged between the high-pressure side of the compressor unit and the phase-less heat exchanger. After passing through the compressor unit, the supercritical CO2 that becomes high temperature and high pressure passes through the oil separator to separate the lubricating oil and CO2 in the compressor unit to avoid affecting the subsequent fluid flow and heat exchange process.

[0016] The compressor unit uses multiple compressors connected in parallel.

[0017] The non-phase-change heat exchanger adopts a heat recovery heat exchanger; the inlet and outlet of the heat-carrying working medium of the heat recovery heat exchanger are connected through a heat-carrying working medium pipeline, and the heat-carrying working medium flows inside the heat-carrying working medium pipeline. The heat-carrying working medium is water or air. The CO2 inlet and outlet are connected through a CO2 pipeline, and CO2 flows inside the CO2 pipeline. The heat-carrying working medium pipeline and the CO2 pipeline are not connected; inside the heat recovery heat exchanger, the positions of the CO2 inlet and outlet and the heat-carrying working medium inlet and outlet are reverse, and the flow direction of CO2 and the flow direction of the heat-carrying working medium are reverse inside the heat recovery heat exchanger. The heat exchange method between sCO2 and the heat-carrying working medium is a countercurrent heat exchange method, and the heat of the data center is properly utilized with the external heat-using end. The inlet and outlet of the heat-carrying working medium of the heat recovery heat exchanger 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 through pipelines. A first stop valve and a second stop valve are respectively 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 inlet of the heat-carrying working medium of the heat recovery heat exchanger through a pipeline. The outlet of the heat-carrying working medium of the heat recovery heat exchanger is connected to the first stop valve and the second stop valve connected in parallel through a pipeline. The first to third stop valves are respectively connected to a flow control module; 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 inside the battery pack is used for heating industrial water or drinking water; in a low-temperature environment in winter, the second and third stop valves are opened and the first stop valve is closed. The ion diffusion coefficients in the electrodes and electrolyte decrease sharply, which will cause a sudden increase in polarization resistance and a decrease in battery capacity. Therefore, the heat generated by the working battery pack during the working process is transported to the nearby energy storage battery module that is not in the working state to increase the battery operation start temperature and maintain the battery capacity and charge-discharge efficiency; the waste heat utilization rate is improved, and the synergetic optimization of the heat dissipation efficiency, safety, and energy utilization rate is realized.

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

[0019] The phase change evaporation module includes multiple groups of cooling solid type evaporators connected in parallel, and each evaporator is mounted on the outer wall of the battery pack.

[0020] In the condensation and dehumidification module, the air-cooled condensation module uses a heat exchanger with air-to-air heat exchange function and the ability to discharge condensed water. Specifically, it is a plate heat exchanger, plate-fin heat exchanger, shell and tube heat exchanger, or fin-tube bundle heat exchanger. It 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 evaporator. Through the secondary phase change condensation method, the liquid phase CO2 that was not fully vaporized in the previous link is vaporized, absorbs heat, and heats up to a higher temperature state consistent with the outside air temperature. While cooling the CO2, it removes water vapor from the environment to prevent the battery system from getting damp. It is then directly transported to the compressor to start the next cycle. The present invention achieves efficient heat dissipation through the compression-expansion phase change cycle of supercritical carbon dioxide, while using the condensation and dehumidification module to accurately control the ambient humidity, ensuring that the battery system operates safely and stably under optimal working conditions.

[0021] Furthermore, the present invention also includes a thermal runaway emergency injection system including a temperature sensor, a second isolation valve and a CO2 nozzle; 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 nozzles through the second isolation valve; the plurality of parallel CO2 nozzles are aimed at the outer wall of the battery pack; the temperature sensor and the second isolation valve are respectively connected to a flow control module; the temperature sensor is used as an emergency monitoring, and when an abnormal thermal runaway condition occurs in the battery pack, 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 liquid CO2 is directly injected through the CO2 nozzle onto the surface of the thermal runaway battery pack for emergency cooling. The refrigerant absorbs a large amount of heat and vaporizes, and forms a gaseous CO2 atmosphere to prevent further deterioration of the thermal runaway.

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

[0023] The control method of the energy storage and power battery supercritical carbon dioxide phase change cooling heat prevention and control system of the present invention 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 unit, where it is pressurized and heated to become high-temperature and high-pressure supercritical carbon dioxide (sCO2). This supercritical carbon dioxide has high density and high heat capacity, and the temperature and pressure on the high-pressure side of the compressor unit increase.

[0025] 2) The CO2 is transferred to the phase-less heat exchanger, which transfers the heat extracted by the thermal management system to the outside for preliminary cooling, reducing the sCO2 temperature while maintaining a supercritical state, thereby improving energy efficiency;

[0026] 3) The sCO2 after heat exchange enters the supercritical pipeline of the recuperator and exchanges heat with the gaseous CO2 returning in the gaseous pipeline, further cooling down while still remaining in the supercritical state and at a lower temperature; the non-phase change heat exchanger and the recuperator work together to achieve cascaded utilization of energy;

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

[0028] 5) The gas-liquid two-phase CO2 after passing through the throttling device enters the first gas-liquid separator. The liquid-phase CO2 is separated and settled and then transmitted to the phase change evaporation module through the flow control valve. The gaseous CO2 rises and is transmitted to the second gas-liquid separator, separating the liquid phase and the gaseous phase of CO2; Under normal operating conditions, the flow control module opens the first isolation valve, 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 filling amount in the cycle;

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

[0030] 7) The phase change evaporation module absorbs heat by evaporating the liquid-phase CO2 to cool the battery pack and turns it into gaseous CO2. The gaseous CO2 after refrigeration mixed 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 air-cooled condensation module of the condensation and dehumidification module;

[0032] 9) The secondary phase change condensation module exchanges heat between the low-temperature gaseous CO2 and the wet air to condense the moisture in the wet air and transmits the gaseous CO2 to the gaseous pipeline of the recuperator; the air-cooled condensation module vaporizes and absorbs heat from the liquid-phase CO2 that was not completely vaporized in the previous stage and raises its temperature to a higher temperature state consistent with the outside air temperature, and then directly conveys it to the compressor;

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

[0034] Among them, in step 1), the compressor compresses the carbon dioxide working medium to the supercritical state: pressure > 7.38 MPa, temperature > 31.1 °C.

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

[0036] In step 2), a heat recovery heat exchanger is adopted for the non-phase change heat exchanger. The heat-carrying working medium inlet and outlet of the heat recovery heat exchanger are respectively connected to an external heat recovery system. The high-efficiency countercurrent 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, and is used to precool the CO2 about to enter the throttling device. When the ambient temperature is relatively high in summer, the first and third stop valves are opened and the second stop valve is closed, and the heat generated inside the battery pack is used for heating industrial water or drinking water. In the low-temperature environment in winter, the second and third stop valves are opened and the first stop valve is closed. The ion diffusion coefficients in the electrodes and electrolyte decrease sharply, which will cause a sudden increase in the polarization resistance and a decrease in the battery capacity. Therefore, the heat generated by the working battery pack is transported to the nearby energy storage battery modules that are not in the working state to increase the battery operation start-up temperature and maintain the battery capacity and charge-discharge efficiency. The waste heat utilization rate is improved, and the synergetic optimization of the heat dissipation efficiency, safety and energy utilization rate is realized.

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

[0038] In step 6), the flow control module adjusts the flow rate of CO2 on a second-by-second basis according to the charge-discharge rate of the battery pack. When the charge-discharge rate increases, or the temperature rises due to changes in the seasonal environment, etc., the flow control module immediately increases the CO2 flow rate to ensure that there is sufficient liquid-phase CO2 participating in the phase change endotherm. When the charge-discharge rate decreases, or the temperature decreases due to changes in the seasonal environment, etc., the CO2 flow rate will be automatically reduced to reduce energy consumption. This intelligent adjustment mechanism not only avoids the common overcooling or overheating problems of traditional cooling systems, but also enables the thermal management system to always work at the optimal efficiency point, while controlling the temperature fluctuation within ±2°C. Further, a first temperature threshold and a second temperature threshold are set, and the second temperature threshold is greater than the first temperature threshold. The temperature sensor continuously monitors the temperature of the battery pack. 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 the liquid-phase CO2. When the battery pack has a thermal runaway abnormal condition and the flow control module detects through the temperature sensor that the temperature is higher than the second temperature threshold, the first isolation valve is closed and the second isolation valve is opened, and the liquid-phase 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, and forms a gaseous CO2 atmosphere to prevent the further deterioration of the thermal runaway. The first threshold is 70 - 90°C, and the second temperature threshold is 90 - 140°C. Advantages of the present invention:

[0039] (1) Make full use of the special thermal property changes of supercritical carbon dioxide near the critical point (31.1 °C, 7.38 MPa). It exhibits extremely high heat transfer coefficients (up to 3 - 5 times that of water) and significant heat capacity change characteristics in the near-critical region. The volume of the required heat exchanger is greatly reduced, only about 1 / 3 of that of a 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 a multi-stage energy recovery architecture. Through the synergistic effect of the heat exchanger and the regenerator, achieve the cascaded utilization of energy; The phase change evaporation module effectively solves the problem of high-power density heat dissipation;

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

[0042] (4) Use natural working fluid CO2 (GWP = 1, ODP = 0), which is completely free of harmful substances such as Freon. The fully enclosed circulation design of the thermal management system achieves zero wastewater discharge, and the operating noise is extremely low, ensuring the stability of the cooling effect and maximizing the energy utilization efficiency of the system; Compared with traditional refrigerants, the carbon emissions are reduced by more than 60%, fully meeting the requirements of the strictest environmental protection regulations;

[0043] (5) The modular design makes the footprint of the thermal management system very small, and the power density of each battery cluster is high; All mechanical components involved in the installation and cooperation of each module are standard parts, and the standardized interface design is convenient for installation and maintenance, supporting flexible plugging and replacement of components; It can operate stably in the environmental temperature range of 0 - 100 °C, and is especially suitable for harsh working conditions such as frequent charging and discharging at variable rates;

[0044] (6) Integrate a thermal runaway emergency system, which can complete the direct injection of liquid CO2 and form an inert gas barrier within seconds. Then, combined with the main refrigeration cycle and the condensation and dehumidification module, build a triple protection system of "active cooling - emergency inerting protection - environmental moisture protection";

[0045] (7) In addition to large-scale lithium iron phosphate battery energy storage stations, the thermal management system can also be integrated into the integrated design of the battery chassis from the battery box to the chassis (CTC, Cell to Chassis) for heat dissipation of power batteries for new energy electric vehicles, as well as scenarios such as 5G base station backup power supplies, satellite and space station energy storage systems. Description of the Drawings

[0046] Figure 1 It is a schematic diagram of an embodiment of the supercritical carbon dioxide phase change cooling thermal prevention and control system for energy storage and power batteries of the present invention. Detailed Embodiment

[0047] The present invention will be further described below through specific embodiments in conjunction with the accompanying drawings.

[0048] like Figure 1 As shown, the energy storage and power supercritical carbon dioxide phase change cooling thermal prevention and control system of this embodiment includes: a refrigeration main cycle, a condensation and dehumidification module, a liquid storage tank, a thermal runaway emergency injection 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 and 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 condensing 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-less heat exchanger through an oil separator; the CO2 outlet of the phase-less heat exchanger is connected to the supercritical inlet of the regenerator, and the supercritical inlet and the supercritical outlet of the regenerator are connected through a supercritical pipeline, and 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 gas-liquid two-phase inlet of the second gas-liquid separator; The flow control valve is connected to the inlet of the phase change evaporation module, and 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, and 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 and dehumidification module; the gas phase outlet of the second gas-liquid separator is connected to the inlet of the air-cooled condensation module of the condensation and 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 the gas phase inlet of the regenerator are connected internally through a gas phase pipeline, and the gas phase pipeline of the regenerator is not connected to the supercritical pipeline;

[0050] The flow control module is connected to the control end of the flow control valve and the compressor unit respectively;

[0051] The outlet of the liquid storage tank is connected to the gas-liquid two-phase inlet of the first gas-liquid separator through 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 a CO2 nozzle. The temperature sensor is installed near the electrode terminals of 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 aimed at 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 non-phase-change heat exchanger is a heat recovery heat exchanger; the inlet and outlet of the heat-carrying working medium of the heat recovery heat exchanger are connected through a heat-carrying working medium pipeline, and the heat-carrying working medium flows inside the heat-carrying working medium pipeline. The heat-carrying working medium is water or air. The CO2 inlet and outlet are connected through a CO2 pipeline, and CO2 flows inside the CO2 pipeline. The heat-carrying working medium pipeline and the CO2 pipeline are not connected; inside the heat recovery heat exchanger, the positions of the CO2 inlet and outlet and the heat-carrying working medium inlet and outlet are reversed, and the flow direction of CO2 and the flow direction of the heat-carrying working medium are reversed inside the heat recovery heat exchanger. The heat exchange mode between sCO2 and the heat-carrying working medium is a countercurrent heat exchange mode, and the heat of the data center is properly utilized with the external heat-using end; the inlet and outlet of the heat-carrying working medium of the heat recovery heat exchanger 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 through pipelines. A first stop valve and a second stop valve are respectively 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 inlet of the heat-carrying working medium of the heat recovery heat exchanger through a pipeline. The outlet of the heat-carrying working medium of the heat recovery heat exchanger is connected to the first stop valve and the second stop valve connected in parallel through a pipeline. The first to third stop valves are respectively connected to a flow control module.

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

[0055] 1) The gaseous CO2 from the gas pipeline of the regenerator and the secondary phase change condensation module of the condensation and dehumidification module enters the compressor unit, is pressurized and heated in the compressor unit, and becomes high-temperature and high-pressure supercritical carbon dioxide sCO2, with a pressure >

[0056] 7.38 MPa, and the temperature is 55 - 85 °C, with high density and high heat capacity. The temperature and pressure on the high-pressure side of the compressor unit increase; after passing through the compressor unit, the high-temperature and high-pressure supercritical CO2 passes through an oil separator to separate the lubricating oil in the compressor unit from the CO2, avoiding affecting the subsequent fluid flow and heat exchange process;

[0057] 2) The carbon dioxide is transported to the heat recovery heat exchanger, and the heat recovery heat exchanger gives the heat extracted by the heat management system to the outside for preliminary cooling, reducing the temperature of sCO2 (generally reduced to 35 - 50 °C) but still remaining in the supercritical state, improving energy efficiency;

[0058] When the ambient temperature is relatively high in summer, the first and third shut-off valves are opened and the second shut-off valve is closed, and the heat generated inside the battery pack is used for heating industrial water or drinking water; in the low-temperature environment in winter, the second and third shut-off valves are opened and the first shut-off valve is closed. The ion diffusion coefficients in the electrodes and electrolyte decrease sharply, which will lead to a sudden increase in polarization resistance and a decrease in battery capacity. Therefore, the heat generated by the working battery pack is transported to the nearby energy storage battery modules that are not in the working state to increase the battery operating start-up temperature and maintain the battery capacity and charge-discharge efficiency; the utilization rate of waste heat is improved, and the synergistic optimization of heat dissipation efficiency, safety and energy utilization rate is achieved;

[0059] 3) The heat-exchanged sCO2 enters the supercritical pipeline of the recuperator and exchanges heat with the gaseous CO2 returning in the gaseous pipeline, further cooling down, still remaining in the supercritical state and at a lower temperature (but not lower than 32 °C); the synergistic effect of the heat recovery heat exchanger and the recuperator realizes the cascade utilization of energy;

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

[0061] 5) The gas-liquid two-phase CO2 after passing through the throttling device enters the first gas-liquid separator. The liquid-phase CO2 is separated and settled and transmitted to the phase change evaporation module through the flow control valve. The gas-phase CO2 rises and is transmitted to the second gas-liquid separator, and the liquid phase and gas phase of CO2 are separated; under normal operating conditions, the flow control module opens the first isolation valve, 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 filling amount in the cycle; the CO2 filling amount is detected by a flow sensor, and the flow sensor is connected to the flow control module, or the CO2 filling amount is detected manually;

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

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

[0064] 8) The second gas-liquid separator separates gaseous CO2 from 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 air-cooled condensation module of the condensation and dehumidification module;

[0065] 9) The secondary phase change condensation module exchanges heat between the low-temperature gaseous CO2 and the wet air to condense the moisture in the wet air, and transports the gaseous CO2 to the gaseous phase pipeline of the regenerator; the air-cooled condensation module vaporizes the liquid CO2 that was not completely vaporized in the previous stage and absorbs heat to raise the temperature to a higher temperature state consistent with the ambient air temperature, and then directly transports it to the compressor;

[0066] 10) The gaseous CO2 exchanges heat with sCO2 in the gaseous phase pipeline and the supercritical pipeline of the regenerator, is preheated and then returns 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 °C, the flow control module controls the flow control valve to increase the flow rate of liquid CO2; when the battery pack has a thermal runaway abnormal condition, and the flow control module detects through the temperature sensor that the temperature is higher than the second temperature threshold of 100 °C, the first isolation valve is closed and the second isolation valve is opened. The 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, and forms a gaseous CO2 atmosphere to prevent the 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 invention. However, those skilled in the art can understand that: without departing from the spirit and scope of the present invention and the appended claims, various substitutions and modifications are possible. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the scope of protection claimed by the present invention is subject to the scope defined by the claims.

Claims

1. A supercritical carbon dioxide phase change cooling thermal prevention and control system for energy storage and power batteries, characterized in that, The heat prevention and control system includes: a main refrigeration cycle, a condensation and dehumidification module and a liquid storage tank; wherein the main refrigeration 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 and a flow control module; the condensation and 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 condensing 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, and the supercritical inlet of the regenerator is connected to the inside of the supercritical outlet through a supercritical pipe, and 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 ... through a flow control device. The control valve is connected to the inlet of the phase change evaporation module, and 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, and 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 and dehumidification module; the gas phase outlet of the second gas-liquid separator is connected to the inlet of the air-cooled condensation module of the condensation and 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 the gas phase inlet of the regenerator are connected internally through a gas phase pipeline, and the gas phase pipeline of the regenerator is not connected to the supercritical pipeline; The flow control module is connected to the control end of the flow control valve and the compressor unit respectively; The outlet of the liquid storage tank is connected to the gas-liquid two-phase inlet of the first gas-liquid separator through a first isolation valve, and the first isolation valve is connected to the flow control module.

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

3. The thermal prevention and control system according to claim 1, characterized in that, The non-phase change heat exchanger adopts a heat recovery heat exchanger; the inlet and outlet of the heat-carrying working medium of the heat recovery heat exchanger are connected through a heat-carrying working medium pipeline, and the heat-carrying working medium flows inside the heat-carrying working medium pipeline. The heat-carrying working medium is water or air. The CO2 inlet and outlet are connected through a CO2 pipeline, and CO2 flows inside the CO2 pipeline. The heat-carrying working medium pipeline and the CO2 pipeline are not connected; inside the heat recovery heat exchanger, the positions of the CO2 inlet and outlet and the heat-carrying working medium inlet and outlet are reversed, and the flow direction of CO2 and the flow direction of the heat-carrying working medium are reversed inside the heat recovery heat exchanger. The heat exchange method between sCO2 and the heat-carrying working medium is a countercurrent heat exchange method; the inlet and outlet of the heat-carrying working medium of the heat recovery heat exchanger 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 through pipelines. A first stop valve and a second stop valve are respectively 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 inlet of the heat-carrying working medium of the heat recovery heat exchanger through a pipeline. The outlet of the heat-carrying working medium of the heat recovery heat exchanger is connected to the first stop valve and the second stop valve connected in parallel through a pipeline. The first to third stop valves are respectively connected to a flow control module.

4. The thermal prevention and control system according to claim 1, wherein 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.

5. The thermal prevention and control system according to claim 1, characterized in that, The air-cooled condensation module adopts a heat exchanger with air-air heat exchange function and capable of discharging condensed water.

6. The thermal prevention and control system according to claim 1, characterized in that, The secondary phase change condensation module adopts a cooling air type evaporator.

7. The thermal prevention and control system according to claim 1, wherein, It further includes a thermal runaway emergency injection system, and the thermal runaway emergency injection system includes a temperature sensor, a second isolation valve and a CO2 nozzle; wherein, the temperature sensor is installed on the battery pack; the outlet of the liquid storage tank is connected to a plurality of parallel CO2 nozzles through the second isolation valve; the plurality of 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 a flow control module.

8. A control method for a supercritical carbon dioxide phase change cooling heat prevention and 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 pipeline of the regenerator and the secondary phase change condensation module of the condensation and dehumidification module enters the compressor unit, is pressurized and heated in the compressor unit, and becomes high-temperature and high-pressure supercritical carbon dioxide sCO2, which has high density and high heat capacity. The temperature and pressure on the high-pressure side of the compressor unit increase; 2) The carbon dioxide is transmitted to the non-phase change heat exchanger, and the non-phase change heat exchanger gives the heat extracted by the thermal management system to the outside for preliminary cooling, reducing the temperature of sCO2 but still maintaining the supercritical state, and improving the energy efficiency; 3) The heat-exchanged sCO2 enters the supercritical pipeline of the regenerator and exchanges heat with the gaseous CO2 returning in the gas phase pipeline, further cooling down, still maintaining the supercritical state and at a lower temperature; the non-phase change heat exchanger and the regenerator work together, realizing cascaded utilization of energy; 4) The low-temperature sCO2 flows through the throttling device, and the sCO2 is depressurized to the subcritical region, and part of the CO2 is liquefied to form a gas-liquid two-phase state; 5) After passing through the throttling device, the gas-liquid two-phase CO2 enters the first gas-liquid separator. The liquid phase CO2 is separated and settled and transferred to the phase change evaporation module through the flow control valve. The gas phase CO2 rises and is transferred to the second gas-liquid separator, where the liquid phase and gas phase of CO2 are separated. 6) The flow control module accurately controls the flow control valve to dynamically adjust the flow of liquid CO2 according to the charge and discharge rate of the battery pack and transmits it 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 the liquid CO2 turns into gaseous CO2. After refrigeration, the gaseous CO2 A small amount of liquid CO2 is transported to the second gas-liquid separator; 8) The second gas-liquid separator separates the gaseous CO2 from the liquid CO2, and then transmits the gaseous CO2 to the secondary phase change condensation module of the condensation and dehumidification module, and transmits 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 moist air, condensing the moisture in the moist air and transferring the gaseous CO2 to the gas phase pipeline of the regenerator; the air-cooled condensation module vaporizes the liquid CO2 that has not been fully vaporized in the previous link, absorbs heat, and heats it to a higher temperature consistent with the outside air temperature, and then directly transfers it to the compressor; 10) The gaseous CO2 exchanges heat with the sCO2 in the supercritical pipe in the gas phase pipe of the regenerator, is preheated and then returns to the compressor, completing the closed-loop cycle.

9. The control method according to claim 8, wherein In step 2), a heat recovery heat exchanger is used without a phase change heat exchanger. The heat carrier inlet and outlet of the heat recovery heat exchanger are respectively connected to an external heat recovery system. A high-efficiency countercurrent heat exchange method is used to recover the residual cold energy of the low-temperature gas-phase CO2 returned from the phase change heat dissipation module, which is used to pre-cool the CO2 that is 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, and the heat generated from the inside of the battery pack is used to heat industrial water or drinking water; in winter, under low temperature conditions, the second and third stop valves are opened and the first stop valve is closed, and the heat generated by the battery pack in operation is transferred to the nearby battery modules that are not in the working state.

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

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