Thermal Management System for Lithium Iron Phosphate and Vanadium Redox Flow Coupled Energy Storage Unit

Abstract

This invention discloses a thermal management system for a lithium iron phosphate (LFP) and vanadium redox flow coupled energy storage unit, relating to the field of energy storage battery thermal management. The system includes a refrigerant storage tank, a compressor, a heating wire, a LFP battery, an electromagnetic four-way reversing valve, a first three-way reversing valve, a condenser, a first fan, a second three-way reversing valve, an expansion valve, a second fan, a third fan, an evaporator, a fourth fan, a positive electrode electrolyte storage tank, a negative electrode electrolyte storage tank, a first circulation pump, a second circulation pump, and a fuel cell stack. The refrigerant storage tank, compressor, electromagnetic four-way reversing valve, condenser, expansion valve, and evaporator form a refrigerant circulation loop through pipelines. This invention employs the aforementioned thermal management system for a LFP and vanadium redox flow coupled energy storage unit, achieving coupling between the LFP and vanadium redox flow thermal management systems. Simultaneously, the activation of the heating wire and the directional migration of waste heat from the LFP battery ensure efficient and stable operation of the coupled energy storage unit in cold environments.

Description

Technical Field

[0001] This invention relates to the field of thermal management technology for energy storage batteries, and in particular to a thermal management system for a lithium iron phosphate and vanadium redox flow coupled energy storage unit. Background Technology

[0002] With the large-scale integration of renewable energy, lithium iron phosphate batteries and vanadium redox flow batteries have gradually become hot topics in energy storage technology research due to their unique advantages in the field of electrical energy storage. However, the independent thermal management systems of these two types of batteries in existing technologies have significant defects, which limit their further development in hybrid energy storage systems.

[0003] Lithium iron phosphate (LFP) batteries are widely used due to their high safety, long cycle life, and environmental friendliness. They exhibit good thermal stability, are not prone to thermal runaway, and perform excellently in high-temperature environments. However, LFP batteries show poor charge-discharge performance at low temperatures, especially at -20°C, where battery capacity drops significantly, requiring an additional thermal management system to maintain performance. Furthermore, the waste heat generated by traditional liquid cooling systems during operation is not effectively utilized, leading to energy waste.

[0004] Vanadium redox flow batteries (VRBs) offer advantages such as high power, large capacity, high safety, and long lifespan. Their design is flexible, allowing for increased energy storage capacity through increased electrolyte volume, while also exhibiting good charge-discharge performance and environmental adaptability. However, the operating efficiency of VRBs decreases significantly at low temperatures. When the ambient temperature is below 25°C, the activity of the vanadium ion redox pair decreases, and the electrolyte viscosity increases, leading to an increase in the stack's internal resistance. Furthermore, at high temperatures (above 40°C), vanadium ions are prone to side reactions, and existing air-cooling systems are insufficient for heat dissipation at extreme temperatures, requiring additional high-power cooling equipment, further increasing system complexity.

[0005] Current hybrid energy storage systems mostly employ independent thermal management architectures, such as lithium iron phosphate batteries and vanadium redox flow batteries each having their own independent temperature control loops. This design leads to equipment redundancy and low energy efficiency. To address these issues, this invention proposes a thermal management system suitable for coupled lithium iron phosphate and vanadium redox flow batteries, achieving a technological breakthrough through the following innovations:

[0006] A thermal management system for the coupled energy storage unit (ESU) of lithium iron phosphate (LFP) and vanadium redox flow batteries is established by switching heating / cooling modes using an electromagnetic four-way reversing valve. When the ambient temperature is ≤-20℃, the heating wire is activated to heat the LFP battery. Simultaneously, utilizing the phase change characteristics of R410A, the system continuously absorbs heat generated by the LFP battery and converts this heat into a heat source for the vanadium redox flow battery during low-temperature operation, thus heating the coupled energy storage unit. When -20℃ < ambient temperature < 40℃, the heating wire is deactivated to stop heating the LFP battery. When the ambient temperature is ≥40℃, heating of the energy storage unit ceases, and a cooling cycle begins. The refrigerant R410A absorbs heat generated by the LFP battery, undergoes air cooling and pressure reduction expansion, and then vaporizes and absorbs heat in the evaporator, thus cooling the coupled energy storage unit. Ultimately, this achieves efficient heat reuse and overall energy efficiency improvement, ensuring stable operation of the energy storage unit under extreme temperatures and maximizing energy conversion efficiency.

[0007] It fundamentally solves the problems of high thermal management energy consumption, slow response, and poor environmental adaptability of hybrid energy storage systems, and provides key technical support for the next generation of high-density energy storage power stations. Summary of the Invention

[0008] The purpose of this invention is to provide a thermal management system for a lithium iron phosphate and vanadium redox flow coupled energy storage unit. By dynamically switching the heating / cooling mode, the coupling of the lithium iron phosphate and vanadium redox flow thermal management system is achieved. At the same time, the activation of the heating wire and the directional migration of waste heat from the lithium iron phosphate battery ensure the efficient and stable operation of the coupled energy storage unit in cold environments.

[0009] This invention provides a thermal management system for a lithium iron phosphate and vanadium redox flow coupled energy storage unit, comprising a refrigerant storage tank, a compressor, a heating wire, a lithium iron phosphate battery, an electromagnetic four-way reversing valve, a first three-way reversing valve, a condenser, a first fan, a second three-way reversing valve, an expansion valve, a second fan, a third fan, an evaporator, a fourth fan, a vanadium redox flow battery thermal management system, a positive electrode electrolyte storage tank, a negative electrode electrolyte storage tank, a first circulation pump, a second circulation pump, and a battery stack. The refrigerant storage tank, compressor, electromagnetic four-way reversing valve, condenser, expansion valve, and evaporator form a refrigerant circulation loop through pipelines. The heating wire is disposed on the pipeline between the lithium iron phosphate battery and the compressor. The first circulation pump circulates between the positive electrode electrolyte storage tank and the battery stack, and the second circulation pump circulates between the negative electrode electrolyte storage tank and the battery stack.

[0010] Preferably, the AB port and CD port of the electromagnetic four-way reversing valve are connected by a pipeline, and the AD port and BC port of the electromagnetic four-way reversing valve are connected by a pipeline; the first three-way reversing valve is installed on the pipeline between the B port of the electromagnetic four-way reversing valve and the condenser; the second three-way reversing valve is installed on the pipeline between the expansion valve and the evaporator.

[0011] Preferably, the first fan is located on the air outlet side of the condenser; the fourth fan is located on the air inlet side of the evaporator; the second fan is located on the pipeline between the expansion valve and the D port of the electromagnetic four-way reversing valve; and the third fan is located on the pipeline between the C port of the electromagnetic four-way reversing valve and the refrigerant storage tank.

[0012] Preferably, the refrigerant in the refrigerant receiver tank is R410A.

[0013] Preferably, the control cable of the electromagnetic four-way reversing valve is connected to the temperature sensor; the power supply circuit of the heating wire is connected in series with the temperature relay; and the stepper motor of the expansion valve is electrically connected to the CAN bus of the battery management system.

[0014] Preferably, the condenser and the fuel cell stack are connected by heat exchange, and the evaporator and the fuel cell stack are connected by heat exchange.

[0015] Therefore, the present invention adopts the above-mentioned thermal management system of lithium iron phosphate and vanadium redox flow coupled energy storage unit. By dynamically switching the heating / cooling mode, the coupling of lithium iron phosphate and vanadium redox flow thermal management system is realized. At the same time, the start-up of the heating wire and the directional migration of waste heat from the lithium iron phosphate battery ensure the efficient and stable operation of the coupled energy storage unit in cold environments.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a system schematic diagram of the heating mode of a lithium iron phosphate and vanadium redox flow coupled energy storage unit according to the present invention;

[0018] Figure 2 This is a system schematic diagram of the cooling mode of a lithium iron phosphate and vanadium redox flow coupled energy storage unit according to the present invention.

[0019] Figure Labels

[0020] 1. Refrigerant receiver tank; 2. Compressor; 3. Heating wire; 4. Lithium iron phosphate battery; 5. Electromagnetic four-way reversing valve; 6. First three-way reversing valve; 7. Condenser; 8. First fan; 9. Second three-way reversing valve; 10. Expansion valve; 11. Second fan; 12. Third fan; 13. Evaporator; 14. Fourth fan; 15. Positive electrolyte storage tank; 16. Negative electrolyte storage tank; 17. First circulation pump; 18. Second circulation pump; 19. Battery stack. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0023] The terms "first," "second," and similar words used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0024] Example 1

[0025] like Figures 1-2 As shown, the present invention discloses a thermal management system for a lithium iron phosphate and vanadium redox flow coupled energy storage unit, comprising a refrigerant storage tank 1, a compressor 2, a heating wire 3, a lithium iron phosphate battery 4, an electromagnetic four-way reversing valve 5, a first three-way reversing valve 6, a condenser 7, a first fan 8, a second three-way reversing valve 9, an expansion valve 10, a second fan 11, a third fan 12, an evaporator 13, a fourth fan 14, a positive electrode electrolyte storage tank 15, a negative electrode electrolyte storage tank 16, a first circulation pump 17, a second circulation pump 18, and a battery stack 19.

[0026] The refrigerant receiver tank 1, compressor 2, electromagnetic four-way reversing valve 5, condenser 7, expansion valve 10, and evaporator 13 form a refrigerant circulation loop through pipelines. Heating wire 3 is installed on the pipeline between the lithium iron phosphate battery 4 and compressor 2. The condenser 7 and evaporator 13 are connected to the battery stack 19 for heat exchange. A first circulation pump 17 circulates between the positive electrolyte storage tank 15 and the battery stack 19, and a second circulation pump 18 circulates between the negative electrolyte storage tank 16 and the battery stack 19.

[0027] The AB port and CD port of the electromagnetic four-way reversing valve 5 are connected by a pipeline, and the AD port and BC port of the electromagnetic four-way reversing valve 5 are connected by a pipeline. The first three-way reversing valve 6 is installed on the pipeline between the B port of the electromagnetic four-way reversing valve 5 and the condenser 7; the second three-way reversing valve 9 is installed on the pipeline between the expansion valve 10 and the evaporator 13.

[0028] The first fan 8 is located on the air outlet side of the condenser 7; the fourth fan 14 is located on the air inlet side of the evaporator 13. The second fan 11 is located on the pipeline between the expansion valve 10 and the D port of the electromagnetic four-way reversing valve 5; the third fan 12 is located on the pipeline between the C port of the electromagnetic four-way reversing valve 5 and the refrigerant storage tank 1.

[0029] The refrigerant in the refrigerant receiver 1 is R410A. The control cable of the electromagnetic four-way reversing valve 5 is connected to the temperature sensor; the power supply circuit of the heating wire 3 is connected in series with the temperature relay; the stepper motor of the expansion valve 10 is electrically connected to the CAN bus of the battery management system.

[0030] The condenser 7 and the fuel cell stack 19 are connected via heat exchange, as are the evaporator 13 and the fuel cell stack 19. Through a refrigerant circulation loop consisting of the refrigerant storage tank 1, compressor 2, electromagnetic four-way reversing valve 5, condenser 7, and evaporator 13, combined with the synergistic action of the heating wire 3, first circulation pump 17, second circulation pump 18, and fan, temperature control of the lithium iron phosphate and vanadium redox flow coupled energy storage unit is achieved. The specific working process is as follows:

[0031] When the ambient temperature is low, the coupled energy storage unit needs to be heated to ensure reaction efficiency.

[0032] At this time, refrigerant R410A flows from the refrigerant receiver tank 1 to the compressor 2, making the refrigerant a high-pressure gas and increasing the refrigerant's saturation temperature.

[0033] The heat generated by the lithium iron phosphate battery 4 is absorbed and then vaporized, providing sufficient heat for the thermal management system of the vanadium redox flow battery.

[0034] When the ambient temperature is ≤-20℃, a heating cycle is performed. The R410A refrigerant in the refrigerant storage tank 1 flows through the compressor 2, where it is compressed into a high-pressure gas, increasing its saturation temperature. The high-pressure refrigerant flows through the heating wire 3 on the pipeline between the lithium iron phosphate battery 4 and the compressor 2. The heating wire 3 activates, heating the refrigerant, which then vaporizes and absorbs heat from the lithium iron phosphate battery 4. The vaporized refrigerant then passes through the electromagnetic four-way reversing valve 5. At this point, the AB port and CD port of the electromagnetic four-way reversing valve 5 are connected. The AB port of the electromagnetic four-way reversing valve 5 flows to the first three-way reversing valve 6, and then into the condenser 7. In the condenser 7, the refrigerant liquefies and releases heat. This heat is blown by the first fan 8 to the vanadium redox flow battery stack 19, improving the reaction efficiency of the stack 19. The liquefied refrigerant then passes through the second three-way reversing valve 9 and the expansion valve 10 to reduce its pressure, and then through the second fan 11, the CD port of the electromagnetic four-way reversing valve 5, and the third fan 12, finally returning to the refrigerant storage tank 1.

[0035] The first circulation pump 17 transports the positive electrode electrolyte from the positive electrode electrolyte storage tank 15 to the fuel cell stack 19, and the second circulation pump 18 transports the negative electrode electrolyte from the negative electrode electrolyte storage tank 16 to the fuel cell stack. After the reaction, the electrolyte flows back to the corresponding storage tank, and the refrigerant continuously heats the fuel cell stack through the condenser 7.

[0036] -20℃ < ambient temperature < 40℃, continuous heating: heating wire 3 stops working, and the refrigerant circulation path is the same as in the low-temperature environment; the AB port of the electromagnetic four-way reversing valve 5 is connected to the CD port of the electromagnetic four-way reversing valve 5, and the refrigerant flows to the first three-way reversing valve 6, and then enters the condenser 7. In the condenser 7, the refrigerant liquefies and releases heat, and the heat is blown to the vanadium redox flow battery stack 19 by the first fan 8, improving the reaction efficiency of the stack 19. The liquefied refrigerant is depressurized by the second three-way reversing valve 9 and the expansion valve 10, and then returns to the refrigerant storage tank 1 by the second fan 11, the CD port of the electromagnetic four-way reversing valve 5 and the third fan 12.

[0037] The first circulation pump 17 transports the positive electrode electrolyte from the positive electrode electrolyte storage tank 15 to the fuel cell stack, and the second circulation pump 18 transports the negative electrode electrolyte from the negative electrode electrolyte storage tank 16 to the fuel cell stack 19. After the reaction, the electrolyte flows back to the corresponding storage tank, and the refrigerant continuously heats the fuel cell stack 19 through the condenser.

[0038] When the ambient temperature is ≥40℃, the refrigeration cycle is as follows: The electromagnetic four-way reversing valve 5 is de-energized, its AD ports are connected, and its BC ports are connected, switching to the refrigeration circuit. After being pressurized by the compressor 2, the refrigerant flows through the lithium iron phosphate battery 4, absorbs heat, and vaporizes. It then enters the D port of the electromagnetic four-way reversing valve 5, passes through the second fan 11, and reaches the expansion valve 10, where its pressure is reduced to a low-pressure liquid state. The low-pressure refrigerant enters the evaporator 13 through the second three-way reversing valve 9, vaporizes, and absorbs heat generated by the reaction in the fuel cell stack 19. The fourth fan 14 accelerates heat dissipation, preventing the fuel cell stack 19 from overheating and causing vanadium ion side reactions. The vaporized refrigerant then flows through the B port of the electromagnetic four-way reversing valve 5 and the third fan 12 to the refrigerant storage tank 1, completing the cycle.

[0039] Evaporator 13 is connected to fuel cell stack 19 via finned heat exchanger. The refrigerant absorbs heat in evaporator 13, reducing the temperature of fuel cell stack 19. First circulation pump 17 and second circulation pump 18 continuously drive electrolyte circulation to ensure uniform temperature.

[0040] When the ambient temperature is <40℃, the circuit is powered on, and ports AB and CD are connected for heating cycle. When the ambient temperature is ≥40℃, the circuit is powered off, and ports AD and BC of the electromagnetic four-way reversing valve 5 are connected for cooling cycle (controlled by a temperature sensor signal). The expansion valve 10 receives CAN bus signals from the battery management system (BMS) via a stepper motor and adjusts the valve opening based on the battery state of charge (SOC) and the flow battery temperature rise rate to control the refrigerant flow. Fan layout: First fan 8 accelerates the condenser 7 to dissipate heat to the fuel cell stack 19. Fourth fan 14 accelerates the evaporator 13 to absorb heat from the fuel cell stack. Second fan 11 and third fan 12 assist in cooling the refrigerant.

[0041] The thermal management unit of the lithium iron phosphate battery and the thermal management unit of the vanadium redox flow battery share the same refrigerant circulation loop. They form a bidirectional heat transfer coupling channel through components such as the electromagnetic four-way reversing valve 5, the three-way reversing valve, the condenser 7, the evaporator 13, the circulation pump, and the fan. This allows the waste heat between different types of batteries to migrate and reuse in a single cycle, thereby maintaining efficient collaborative temperature control performance under multiple operating conditions.

[0042] The coupled thermal management system can switch the heat flow direction and operating mode based on the ambient temperature and battery operating status. In both heating and cooling states, it relies on the same refrigerant cycle to complete the heat release and heat absorption process, realizing heat energy sharing and regulation, significantly improving energy utilization and reducing the energy consumption of independent systems.

[0043] When the ambient temperature is low, the refrigerant absorbs the waste heat generated by the lithium iron phosphate battery during its operation and transfers this heat to the vanadium redox flow battery stack, providing a heat source for its low-temperature operation. The heating wire is only activated for auxiliary heating in extremely low temperatures. When the ambient temperature is high, the refrigerant first absorbs heat in the lithium iron phosphate battery, and then, after cooling and depressurization, further absorbs heat in the vanadium redox flow battery and releases it into the environment, thereby ensuring that the entire coupled system maintains a stable and efficient operating state in different temperature zones.

[0044] Therefore, the present invention adopts the above-mentioned thermal management system of lithium iron phosphate and vanadium redox flow coupled energy storage unit. By dynamically switching the heating / cooling mode, the coupling of lithium iron phosphate and vanadium redox flow thermal management system is realized. At the same time, the start-up of the heating wire and the directional migration of waste heat from the lithium iron phosphate battery ensure the efficient and stable operation of the coupled energy storage unit in cold environments.

[0045] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A thermal management system for a lithium iron phosphate and vanadium redox flow coupled energy storage unit, characterized in that, The system includes a refrigerant reservoir, compressor, heating wire, lithium iron phosphate battery, electromagnetic four-way reversing valve, first three-way reversing valve, condenser, first fan, second three-way reversing valve, expansion valve, second fan, third fan, evaporator, fourth fan, positive electrolyte reservoir, negative electrolyte reservoir, first circulation pump, second circulation pump, and fuel cell stack. The refrigerant reservoir, compressor, electromagnetic four-way reversing valve, condenser, expansion valve, and evaporator form a refrigerant circulation loop through pipelines. The heating wire is installed in the pipeline between the lithium iron phosphate battery and the compressor. The first circulation pump circulates between the positive electrolyte reservoir and the fuel cell stack, and the second circulation pump circulates between the negative electrolyte reservoir and the fuel cell stack. The AB port and CD port of the electromagnetic four-way reversing valve are connected by a pipeline, and the AD port and BC port of the electromagnetic four-way reversing valve are connected by a pipeline; the first three-way reversing valve is installed on the pipeline between the B port of the electromagnetic four-way reversing valve and the condenser; the second three-way reversing valve is installed on the pipeline between the expansion valve and the evaporator. The first fan is located on the air outlet side of the condenser; the fourth fan is located on the air inlet side of the evaporator; the second fan is located on the pipeline between the expansion valve and port D of the solenoid four-way reversing valve; and the third fan is located on the pipeline between port C of the solenoid four-way reversing valve and the refrigerant receiver tank.

2. The thermal management system for a lithium iron phosphate and vanadium redox flow coupled energy storage unit according to claim 1, characterized in that, The refrigerant in the refrigerant receiver tank is R410A.

3. The thermal management system for a lithium iron phosphate and vanadium redox flow coupled energy storage unit according to claim 1, characterized in that, The control cable of the electromagnetic four-way reversing valve is connected to the temperature sensor; the power supply circuit of the heating wire is connected in series with the temperature relay; the stepper motor of the expansion valve is electrically connected to the CAN bus of the battery management system.

4. The thermal management system for a lithium iron phosphate and vanadium redox flow coupled energy storage unit according to claim 1, characterized in that, The condenser and the fuel cell stack are connected by heat exchange, and the evaporator and the fuel cell stack are also connected by heat exchange.

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