A flow battery energy storage system and method coupled with phase change thermal storage

Abstract

This invention discloses a flow battery energy storage system and method with coupled phase change thermal storage. The system includes a cathode storage tank, an anode storage tank, a high-temperature phase change cavity, a low-temperature phase change cavity, a battery stack, and a control system. Under the control of the control system, the electrolyte selectively flows through the high-temperature and low-temperature phase change cavities. By absorbing the heat generated during battery operation and solar energy through the coupled phase change material, the system always operates within the optimal temperature range, thereby effectively improving the system's energy efficiency and thermal stability, and reducing the system's thermal management energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology of flow batteries, specifically relating to a flow battery energy storage system and method coupled with phase change thermal storage. Background Technology

[0002] Currently, the energy structure is transitioning towards a low-carbon model, making the development of renewable energy power generation technologies particularly important. However, the instability of renewable energy power generation, such as extreme heat and lack of wind, and darkness at night, leads to a continuous widening of the peak-valley difference in renewable energy power generation load, urgently requiring long-term energy storage technologies for regulation. Vanadium redox flow batteries (VRFBs) have secured a place in energy storage technologies due to their advantages such as long lifespan, high safety, and separation of output power and capacity. Nevertheless, VRFBs still face some challenges in practical applications:

[0003] (1) The stability of vanadium ions in the electrolyte is poor, which limits the operating temperature range of the battery (10℃~40℃). Vanadium ions are easily precipitated due to heat accumulation, which affects battery performance and lifespan.

[0004] (2) Due to the low operating temperature, the solubility of vanadium ions in the electrolyte is limited and the viscosity is high, resulting in low energy efficiency and poor charge and discharge performance.

[0005] (3) Vanadium redox flow battery energy storage systems require an active thermal management system, which consumes a high amount of energy.

[0006] (4) Compared with traditional flow battery energy storage systems, vanadium redox flow batteries have lower energy density and require a larger footprint and storage space. These technical bottlenecks limit the performance and application scope of vanadium redox flow battery energy storage systems and urgently need to be overcome through technological innovation. Summary of the Invention

[0007] To address the problems of low energy density, poor thermal stability, high energy consumption of thermal management systems, and low system energy efficiency in existing vanadium redox flow battery energy storage systems, the first objective of this invention is to provide a flow battery energy storage system coupled with phase change thermal storage. The second objective of this invention is to provide a flow battery energy storage method coupled with phase change thermal storage, which aims to combine the storage and utilization of solar thermal energy by phase change materials with the waste heat from the operation of the flow battery, so that the system always operates within the optimal temperature range, thereby effectively improving the system's energy efficiency and thermal stability, and reducing the system's thermal management energy consumption.

[0008] The present invention solves the above problems through the following technical means:

[0009] A flow battery energy storage system coupled with phase change thermal storage includes a cathode storage tank, an anode storage tank, a high-temperature phase change cavity, a low-temperature phase change cavity, a fuel cell stack, and a control system.

[0010] The high-temperature zone phase change cavity is equipped with a high-temperature zone cathode heat exchange tube and a high-temperature zone anode heat exchange tube, and is filled with a high-temperature zone phase change material. The low-temperature zone phase change cavity is equipped with a low-temperature zone cathode heat exchange tube and a low-temperature zone anode heat exchange tube, and is filled with a low-temperature zone phase change material.

[0011] The outlet pipe of the cathode storage tank is connected to one end of the low-temperature zone cathode heat exchange tube, and a cathode booster pump is installed on it. The other end of the low-temperature zone cathode heat exchange tube is connected to the cathode side inlet pipe of the fuel cell stack. The cathode side outlet pipe of the fuel cell stack is connected to the return pipe of the cathode storage tank and one end of the high-temperature zone cathode heat exchange tube through a cathode electromagnetic three-way valve. The other end of the high-temperature zone cathode heat exchange tube is connected to the cathode storage tank.

[0012] The outlet pipe of the anode storage tank is connected to one end of the low-temperature zone anode heat exchange tube, and an anode booster pump is installed on it. The other end of the low-temperature zone anode heat exchange tube is connected to the anode side inlet pipe of the fuel cell stack. The anode side outlet pipe of the fuel cell stack is connected to the return pipe of the anode storage tank and one end of the high-temperature zone anode heat exchange tube through an anode solenoid three-way valve. The other end of the high-temperature zone anode heat exchange tube is connected to the anode storage tank.

[0013] In the specific implementation process, heat exchange fins are added to the heat exchange tubes;

[0014] The control system is electrically connected to the cathode solenoid three-way valve, the anode solenoid three-way valve, the cathode booster pump, and the anode booster pump, respectively.

[0015] Furthermore, the control system includes:

[0016] A temperature sensor is used to detect the temperature of the electrolyte and generate an electrical signal.

[0017] An on-off controller receives electrical signals from a temperature sensor;

[0018] The DC contactor receives electrical signals from the on / off controller and reacts based on the control of the on / off controller to control the on / off of the circuit between the DC power supply and the solenoid three-way valve, thereby changing the outlet of the solenoid three-way valve and the direction of electrolyte flow.

[0019] The PID controller receives electrical signals from the temperature sensor and is used to control the speed of the booster pump.

[0020] Switching power supply, used to power PID controller and on-off controller;

[0021] The computer is connected to the PID controller and the on / off controller.

[0022] Furthermore, the control system has two control loops. The first control loop controls the opening of the solenoid three-way valve. When the temperature sensor detects that the electrolyte temperature exceeds the set value, the on / off controller controls the DC contactor to connect the circuit between the DC power supply and the solenoid three-way valve, energizing the valve and turning its opening to connect directly to the pipeline of the storage tank. Conversely, when the temperature sensor detects that the electrolyte temperature is below the set value, the on / off controller controls the DC contactor to disconnect the circuit between the DC power supply and the solenoid three-way valve, de-energizing the valve and turning its opening to connect to the heat exchange tube in the high-temperature zone. The electrolyte is fed through a solar-heated phase change material, raising its temperature. The second control loop controls the electrolyte flow rate. A PID controller in this loop compares the electrolyte temperature with a set temperature. When the difference is large, the PID controller increases the speed of the booster pump to enhance the heat transfer coefficient of the electrolyte, enabling rapid heat exchange between the electrolyte and the phase change material. Conversely, when the difference is small, the PID controller decreases the speed of the booster pump to better maintain the electrolyte temperature at the set value.

[0023] Furthermore, it also includes a container, in which the cathode storage tank, anode storage tank, fuel cell stack and cryogenic phase change chamber are all located, and the high-temperature phase change chamber is located on the top of the container.

[0024] Furthermore, both the high-temperature zone cathode heat exchange tube and the high-temperature zone anode heat exchange tube are arranged in a serpentine manner in the high-temperature zone phase change cavity.

[0025] Furthermore, both the low-temperature zone cathode heat exchange tube and the low-temperature zone anode heat exchange tube are arranged in a serpentine manner in the low-temperature zone phase change cavity.

[0026] Furthermore, photothermal conversion materials are added to the phase change material in the high-temperature region to enhance the photothermal conversion capability, so as to make full use of solar photothermal energy and increase the temperature of the phase change material in the high-temperature region. Metal nanoparticles such as carbon black, copper oxide, and iron oxide, as well as carbon-based materials such as graphene, which have high light absorption rates, all have this effect.

[0027] Furthermore, the melting point of the phase change material in the high-temperature region is higher than the optimal operating temperature of the system, while the melting point of the phase change material in the low-temperature region is lower than the optimal operating temperature of the system.

[0028] An energy storage method for a flow battery energy storage system employing the aforementioned coupled phase change thermal storage involves the following steps: During system operation, a booster pump is energized and rotates to extract electrolyte from the electrolyte storage tank. Under the action of the booster pump, the electrolyte first flows through the low-temperature zone heat exchange tube, where it exchanges heat with the low-temperature zone phase change material. It then enters the battery stack, where it undergoes a redox reaction. Afterward, the electrolyte flows through a solenoid three-way valve, which is controlled by the control system. When the electrolyte temperature is lower than the set temperature, the solenoid three-way valve controls the electrolyte to flow through the high-temperature zone heat exchange tube, absorbing the light and heat stored in the high-temperature zone phase change material. Conversely, when the electrolyte temperature is higher than the set temperature, the solenoid three-way valve controls it to bypass the high-temperature zone phase change material and flow directly into the storage tank, thus completing one cycle.

[0029] The battery stack is where the electrochemical reaction of the flow battery occurs. The battery stack used in this system is a general vanadium redox flow battery stack. Multiple battery stacks are placed side by side on a support frame, and the battery stacks are charged / discharged in series.

[0030] In this operating mode, the system can flexibly switch the flow channels, allowing the electrolyte to selectively absorb and dissipate heat with the phase change material. This eliminates the need for additional thermal management equipment, reduces the complexity and operating costs of the energy storage system, enables low-cost passive temperature control of the energy storage system, and ensures the safe and efficient operation of the system.

[0031] Furthermore, to further enhance the safety of energy storage system operation and improve battery energy density and efficiency, this invention proposes a high-efficiency and stable operation technology for all-vanadium redox flow batteries. Regarding the electrolyte, this invention uses an electrolyte concentration ratio of 1.7M vanadium ions, 4M sulfate ions, and 1.5% (w / w) ammonium dihydrogen phosphate additive. Phosphate additives can form complexes with vanadium ions, effectively inhibiting vanadium ion precipitation and improving the electrolyte's thermal stability. For additive selection, hydrochloric acid or organic additives have similar effects on improving electrolyte thermal stability. The introduction of a thermally stable electrolyte effectively improves the safety of the energy storage system, providing a foundation for stable operation at high temperatures. The adoption of an intelligent integrated monitoring and control system allows the electrolyte to fully utilize the heat energy stored in the phase change material, providing the necessary temperature conditions for efficient battery operation at high temperatures, thereby effectively improving the system's energy density and efficiency.

[0032] This system, based on the structure of a flow battery energy storage container, adds a high-temperature phase change chamber and a low-temperature phase change chamber. The phase change material in the high-temperature chamber can be a commonly used phase change material with a phase change temperature between 50-60℃, such as polyethylene glycol 4000, polyethylene glycol 2000, or paraffin wax. Furthermore, an appropriate concentration of additives is introduced into the phase change material in the high-temperature chamber to enhance its photothermal conversion capability; these additives can be commonly used photothermal conversion materials such as carbon black, graphite, or graphene. The phase change material in the low-temperature chamber can be a commonly used phase change material with a phase change temperature between 40-50℃, such as lauric acid, sodium thiosulfate pentahydrate, or paraffin wax. Both the high-temperature and low-temperature phase change materials are internally lined with electrolyte pipes and heat exchange fins, allowing for sufficient convective heat exchange with the cathode and anolyte electrolytes.

[0033] Key points of this invention:

[0034] (1) Operation mode and device of flow battery for combined heat and power. This invention modifies the device structure and pipeline layout of a containerized flow battery energy storage system, enabling the system to passively adjust the flow pattern of the electrolyte under different temperature conditions. When the electrolyte temperature is low, the system controls its flow through the high-temperature phase change material to raise the temperature; when the electrolyte temperature is high, the system controls its flow through the low-temperature phase change material to lower the temperature. The pipe sections laid between the phase change materials adopt a serpentine pipe layout to improve their heat exchange effect. The selection of phase change materials needs to ensure that the optimal operating temperature of the system is between the melting point temperature of the phase change material in the high-temperature zone and the melting point temperature of the phase change material in the low-temperature zone.

[0035] (2) Low-cost passive temperature control technology for coupled phase change material (PCM) thermal storage. This system adds a recess for storing the high-temperature PCM and a container for storing the low-temperature PCM within the enclosure of an existing containerized flow battery energy storage system. A photothermal conversion material is added to the high-temperature PCM to enhance its light absorption, enabling it to absorb solar heat and heat up. Electrolyte pipelines are laid within the PCM, recovering and utilizing the heat generated during battery operation and solar heat through heat exchange, achieving co-storage of thermal and electrical energy and thus improving the system's energy density.

[0036] (3) High-Temperature Stabilization Technology of Vanadium Electrolyte Based on Inorganic Additives. This invention prepares a thermally stable electrolyte by introducing inorganic additives into the electrolyte. The electrolyte concentration ratio used in this invention is 1.7M vanadium ions, 4M sulfate ions, and 1.5% (w / w) ammonium dihydrogen phosphate additive. Phosphoric acid additives can form complexes with vanadium ions, thereby effectively inhibiting the precipitation of vanadium ions, enhancing the thermal stability of the electrolyte, and thus improving the suitable operating temperature range of the flow battery, providing a basic condition for the long-term, efficient, and stable operation of the system in a high-temperature environment.

[0037] (4) Intelligent integrated monitoring and control system. The control system built by this invention can monitor the battery's operating status in real time and collect key parameters such as electrolyte temperature and flow rate in real time. It can also automatically adjust the system's operating strategy and the flow distribution of the pipeline network using a PID controller and an on-off controller. In addition, the parameters of the PID controller in this invention are measured by the controller's built-in self-tuning function to improve the accuracy, speed and stability of the control system, ensuring that the energy storage system operates efficiently and stably under high temperature conditions.

[0038] The beneficial effects of this invention are:

[0039] During operation, the phase change material (PCM) in the high-temperature zone absorbs and stores solar thermal energy, maintaining a high temperature; the PCM in the low-temperature zone absorbs and stores the heat generated by the flow battery, maintaining a low temperature. When the flow battery temperature is too low, the electrolyte can exchange heat with the PCM in the high-temperature zone through convection, absorbing the solar thermal energy stored within it, causing the temperature to rise. Conversely, when the flow battery temperature is too high, the electrolyte can exchange heat with the PCM in the low-temperature zone through convection, transferring and storing the heat generated by the flow battery's operation to the low-temperature PCM, causing the temperature to drop. In this process, the system does not require active thermal management equipment to maintain the flow battery's operating temperature within an ideal range, achieving passive thermal management of the flow battery energy storage system. This reduces the operating energy consumption of the flow battery energy storage system and solves the problem of high energy consumption in thermal management of flow battery energy storage systems.

[0040] Furthermore, this system achieves a combined heat and power (CHP) mode for flow batteries that couples photothermal effects. By introducing phase change materials in both high-temperature and low-temperature regions, this system realizes a new CHP operation mode of "flow battery energy storage + phase change material thermal storage," which improves the energy density of the flow battery energy storage system through the joint storage of thermal and electrical energy, thus solving the problem of low energy density in flow battery energy storage systems.

[0041] In summary, the advantages of this invention are as follows:

[0042] 1. A novel flow battery system with coupled phase change thermal storage: By absorbing heat generated during battery operation and solar energy through coupled phase change materials, the flow battery system achieves passive thermal management and reduces energy consumption.

[0043] 2. The combined heat and power storage mode of flow battery with coupled photothermal effect improves energy density through the combined storage of thermal and electrical energy.

[0044] 3. The high-temperature operation mode of the flow battery based on high thermal stability electrolyte and intelligent temperature control strategy effectively improves the system's operating efficiency.

[0045] 4. A novel flow battery energy storage device coupled with phase change thermal storage has advantages such as high safety, high efficiency, and intelligence. Attached Figure Description

[0046] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0047] Figure 1 This is a schematic diagram of a preferred embodiment of the energy storage system of the present invention;

[0048] Figure 2 This is a schematic diagram of the three-dimensional structure of the phase change cavity in the high-temperature region;

[0049] Figure 3 This is a top view of the phase transition cavity in the high-temperature region;

[0050] Figure 4 This is a schematic diagram of the three-dimensional structure of the phase change cavity in the low-temperature region;

[0051] Figure 5 This is a top view of the phase transition cavity in the low-temperature region;

[0052] Figure 6 This is a schematic diagram of the control system;

[0053] Figure 7 Diagram of the thermal stability experimental setup;

[0054] Figure 8 This diagram shows the arrangement of reagent bottles and the precipitation inside the bottles during the thermal stability test.

[0055] Figure 9 The charge-discharge performance curve of the thermally stable electrolyte as a function of temperature;

[0056] Figure 10 This is a comparison chart of electrolyte energy efficiency at 55℃. Detailed Implementation

[0057] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0058] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0059] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0060] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0061] like Figures 1 to 6 As shown, this embodiment provides a flow battery energy storage system coupled with phase change thermal storage. The flow battery energy storage system coupled with phase change thermal storage includes a cathode storage tank 1, an anode storage tank 5, a high-temperature phase change cavity 7, a low-temperature phase change cavity 3, a fuel cell stack 14, and a control system.

[0062] The high-temperature zone phase change cavity is provided with a high-temperature zone cathode heat exchange tube 12 and a high-temperature zone anode heat exchange tube 13, and the high-temperature zone phase change cavity is filled with a high-temperature zone phase change material. The low-temperature zone phase change cavity is provided with a low-temperature zone cathode heat exchange tube 10 and a low-temperature zone anode heat exchange tube 11, and the low-temperature zone phase change cavity is filled with a low-temperature zone phase change material.

[0063] The outlet pipe of the cathode storage tank is connected to one end of the low-temperature zone cathode heat exchange tube, and a cathode booster pump 2 is installed on it. The other end of the low-temperature zone cathode heat exchange tube is connected to the cathode side inlet pipe of the fuel cell stack. The cathode side outlet pipe of the fuel cell stack is connected to the return pipe of the cathode storage tank and one end of the high-temperature zone cathode heat exchange tube through the cathode electromagnetic three-way valve 9. The other end of the high-temperature zone cathode heat exchange tube is connected to the cathode storage tank.

[0064] The outlet pipe of the anode storage tank is connected to one end of the low-temperature zone anode heat exchange tube, and an anode booster pump 4 is installed on it. The other end of the low-temperature zone anode heat exchange tube is connected to the anode side inlet pipe of the fuel cell stack. The anode side outlet pipe of the fuel cell stack is connected to the return pipe of the anode storage tank and one end of the high-temperature zone anode heat exchange tube through the anode electromagnetic three-way valve 8. The other end of the high-temperature zone anode heat exchange tube is connected to the anode storage tank.

[0065] It also includes container 6, in which the cathode storage tank, anode storage tank, fuel cell stack and low-temperature phase change chamber are all located, and the high-temperature phase change chamber is located on the top of the container.

[0066] The high-temperature phase change cavity, located at the top of the container, serves as the container for the high-temperature phase change material and the site for phase change. Its structure is as follows: Figure 2 and Figure 3 As shown, the high-temperature phase change cavity has a generally recessed structure. The high-temperature phase change material is stored within the recess, and the top surface of the recess is covered with transparent glass, which can effectively absorb solar heat and undergo a phase change. The interior of the high-temperature phase change material is uniformly equipped with high-temperature cathode heat exchange tubes, high-temperature anode heat exchange tubes, and corresponding heat exchange fins, allowing for sufficient heat exchange with the cathode and anode electrolytes. It is important to note that because the phase change material gradually transforms into a liquid state during the absorption of solar heat, the inlet and outlet sections of the pipes within the high-temperature phase change cavity should be sealed.

[0067] The low-temperature phase change cavity is the container and phase change site for the low-temperature phase change material, and its structure is as follows: Figure 4 and Figure 5 As shown, the low-temperature phase change chamber is a closed shell containing the low-temperature phase change material. The low-temperature cathode heat exchange tubes, low-temperature anode heat exchange tubes, and corresponding heat exchange fins are embedded in the low-temperature phase change material, allowing for thorough heat exchange. Similar to the high-temperature phase change chamber, the inlet and outlet pipes of the low-temperature phase change chamber also require sealed structures to prevent leakage of the liquid phase change material. It should be noted that the low-temperature phase change chamber can be installed inside a container or within a surrounding enclosure, offering a wide range of placement options and flexible installation.

[0068] The phase change chambers in the high-temperature and low-temperature zones require phase change materials with different melting points to ensure that the optimal operating temperature of the system falls within the melting point range of these materials. Taking this invention as an example, experiments showed that the optimal operating temperature of the battery in the system is 45°C. Therefore, the phase change temperature of the phase change material in the high-temperature zone must be higher than 45°C; polyethylene glycol 4000 (melting point 50–60°C) and polyethylene glycol 2000 (melting point 64–66°C) both meet this requirement. The phase change temperature of the phase change material in the low-temperature zone must be lower than 45°C; lauric acid (melting point 43–44°C) and low-melting-point paraffin both meet this requirement. Furthermore, to fully utilize solar thermal energy and increase the temperature of the phase change material at the top of the high-temperature zone, this invention requires the addition of photothermal fillers. High-absorbency metal nanoparticles such as carbon black, copper oxide, and iron oxide, as well as carbon-based materials such as graphene, all have this effect.

[0069] To achieve more precise electrolyte temperature control, the system is equipped with a programmable solenoid three-way valve. One port of the valve is connected to the fuel cell stack via a pipe, another port is connected to the heat exchange tube section in the high-temperature zone, and the third port is connected to a tube section that does not pass through the phase change material. The control system can select the opening position of the three-way valve. Specifically, for example... Figure 6 As shown, the control system includes: a temperature sensor for detecting the electrolyte temperature and generating an electrical signal;

[0070] The on / off controller receives electrical signals from the temperature sensor; the DC contactor receives electrical signals from the on / off controller and reacts based on the control of the on / off controller, controlling the on / off circuit between the DC power supply and the solenoid three-way valve, thereby changing the outlet of the solenoid three-way valve and the direction of electrolyte flow; the PID controller receives electrical signals from the temperature sensor and is used to control the speed of the booster pump; the switching power supply supplies power to the PID controller and the on / off controller; and the computer is connected to the PID controller and the on / off controller.

[0071] The control system has two control loops. The first control loop controls the opening of the solenoid three-way valve. When the temperature sensor detects that the electrolyte temperature exceeds the set value, the on / off controller controls the DC contactor to connect the DC power supply to the solenoid three-way valve, energizing the valve and turning its opening to connect directly to the pipeline of the storage tank. Conversely, when the temperature sensor detects that the electrolyte temperature is below the set value, the on / off controller controls the DC contactor to disconnect the DC power supply from the solenoid three-way valve, de-energizing the valve and turning its opening to connect to the heat exchange tube in the high-temperature zone. The electrolyte is heated by solar energy as it flows through a phase change material. The second control loop controls the electrolyte flow rate. The PID controller in this loop compares the electrolyte temperature with the set temperature. When the difference is large, the PID controller increases the speed of the booster pump to enhance the heat transfer coefficient of the electrolyte and achieve rapid heat exchange between the electrolyte and the phase change material. Conversely, when the difference is small, the PID controller decreases the speed of the booster pump to better maintain the electrolyte temperature at the set value.

[0072] The high-temperature zone cathode heat exchange tubes and high-temperature zone anode heat exchange tubes are arranged in a serpentine pattern in the high-temperature zone phase change cavity. The low-temperature zone cathode heat exchange tubes and low-temperature zone anode heat exchange tubes are also arranged in a serpentine pattern in the low-temperature zone phase change cavity.

[0073] Adding photothermal conversion materials to phase change materials in the high-temperature region can enhance their photothermal conversion capabilities, thereby fully utilizing solar energy and increasing the temperature of the phase change material in the high-temperature region. High-absorbency metal nanoparticles such as carbon black, copper oxide, and iron oxide, as well as carbon-based materials such as graphene, all have this effect.

[0074] The melting point of the phase change material in the high-temperature zone is higher than the system's optimal operating temperature, while the melting point of the phase change material in the low-temperature zone is lower than the system's optimal operating temperature. The phase change material in the high-temperature zone can be a commonly used phase change material with a phase change temperature between 50-60℃, such as polyethylene glycol 4000, polyethylene glycol 2000, or paraffin wax. Furthermore, an appropriate concentration of additives is introduced into the phase change material in the high-temperature zone to enhance its photothermal conversion capability. These additives can be commonly used photothermal conversion materials, such as carbon black, graphite, or graphene. The phase change material in the low-temperature zone can be a commonly used phase change material with a phase change temperature between 40-50℃, such as lauric acid, sodium thiosulfate pentahydrate, or paraffin wax. Both the high-temperature and low-temperature phase change materials are internally lined with electrolyte pipes and heat exchange fins, allowing for sufficient convective heat exchange with the cathode and anolyte electrolytes.

[0075] Another aspect of this embodiment provides an energy storage method for a flow battery energy storage system employing the aforementioned coupled phase change thermal storage. During system operation, a booster pump is energized and rotates, drawing electrolyte from the electrolyte storage tank. Under the action of the booster pump, the electrolyte first flows through the low-temperature zone heat exchange tube, exchanging heat with the low-temperature zone phase change material, and then enters the battery stack. After undergoing a redox reaction in the battery stack, the electrolyte flows through a solenoid three-way valve. This solenoid three-way valve is controlled by the control system. When the electrolyte temperature is lower than the set temperature, the solenoid three-way valve controls the electrolyte to flow through the high-temperature zone heat exchange tube, absorbing the light and heat stored in the high-temperature zone phase change material. Conversely, when the electrolyte temperature is higher than the set temperature, the solenoid three-way valve controls it to bypass the high-temperature zone phase change material and flow directly into the storage tank, thus completing one cycle.

[0076] More specifically, taking the cathode side as an example, when the system is running, the cathode booster pump is energized and rotates, drawing electrolyte from the cathode storage tank. Under the action of the cathode booster pump, the electrolyte first flows through the low-temperature zone cathode heat exchange tube, where it exchanges heat with the low-temperature zone phase change material, and then enters the fuel cell stack. After undergoing a redox reaction in the fuel cell stack, the electrolyte flows through the cathode solenoid three-way valve. The cathode solenoid three-way valve is controlled by the control system. When the electrolyte temperature is lower than the set temperature, the cathode solenoid three-way valve controls the electrolyte to flow through the high-temperature zone cathode heat exchange tube, absorbing the photothermal energy stored in the high-temperature zone phase change material. Conversely, when the electrolyte temperature is higher than the set temperature, the cathode solenoid three-way valve controls it to bypass the high-temperature zone phase change material and flow directly into the anode storage tank, thus completing one cycle.

[0077] The battery stack is where the electrochemical reaction of the flow battery occurs. The battery stack used in this system is a general vanadium redox flow battery stack. Multiple battery stacks are placed side by side on a support frame, and the battery stacks are charged / discharged in series.

[0078] In this operating mode, the system can flexibly switch the flow channels, allowing the electrolyte to selectively absorb and dissipate heat with the phase change material. This eliminates the need for additional thermal management equipment, reduces the complexity and operating costs of the energy storage system, enables low-cost passive temperature control of the energy storage system, and ensures the safe and efficient operation of the system.

[0079] To further enhance the safety of energy storage system operation and improve battery energy density and efficiency, this invention proposes a high-efficiency and stable operation technology for all-vanadium redox flow batteries. Regarding the electrolyte, this invention uses an electrolyte concentration ratio of 1.7M vanadium ions, 4M sulfate ions, and 1.5% (w / w) ammonium dihydrogen phosphate additive. Phosphate additives can form complexes with vanadium ions, effectively inhibiting vanadium ion precipitation and improving the electrolyte's thermal stability. For additive selection, hydrochloric acid or organic additives have similar effects on improving electrolyte thermal stability. The introduction of a thermally stable electrolyte effectively improves the safety of the energy storage system, providing a foundation for stable operation at high temperatures. The adoption of an intelligent integrated monitoring and control system allows the electrolyte to fully utilize the heat energy stored in the phase change material, providing the necessary temperature conditions for efficient battery operation at high temperatures, thereby effectively improving the system's energy density and efficiency.

[0080] Thermal stability effect

[0081] Phosphate ions can form complexes with pentavalent vanadium ions, inhibiting the high-temperature precipitation and deposition of vanadium pentoxide. Based on this characteristic, the team conducted experimental comparative analysis of the effects of different phosphate additives on the thermal stability of the electrolyte under high-temperature conditions. Ammonium dihydrogen phosphate and diammonium hydrogen phosphate were selected as additives in the experiment, and the experimental setup was as follows: Figure 7 and Figure 8 As shown.

[0082] By observing the bottom of the reagent bottles, the team obtained the time when precipitation was first observed in each group of electrolytes, as shown in Table 1.

[0083] Table 1. Timeline of electrolyte precipitation

[0084]

[0085]

[0086] After precipitation occurred in the sample, the effect of the additive on the high-temperature stability of vanadium ions was further observed. Based on the results in Table 1, the introduction of 1.5% ammonium dihydrogen phosphate additive increased the time for the first precipitation of the electrolyte at 55 and 50 °C from 4 h and 8 h to 35 h and 62 h, respectively, an increase of approximately 8 times, demonstrating excellent thermal stability.

[0087] Running effect

[0088] Based on the results of thermal stability experiments, a test system was designed to evaluate the charge-discharge performance of individual flow battery cells under different temperature conditions. The charge-discharge test system consists of individual battery cells, a storage tank, a peristaltic pump, a battery testing system, and a water bath.

[0089] The thermally stable electrolyte for the flow battery uses a concentration ratio of 1.7 MV + 4 M H2SO4 + 0.15% NH4H2PO4, with 30 mL each for the cathode and anode, and a pumping rate of 40 r / min. The battery's cutoff voltage limits are 1.7 V and 0.7 V, respectively, the charge / discharge current density is constant at 100 mA / cm2, and the operating temperature is controlled by a water bath.

[0090] The charge-discharge characteristics of the thermally stable electrolyte and the conventional electrolyte (without additives) were tested at room temperature, 45, 50, and 55°C, respectively. The coulombic efficiency CE, voltage efficiency VE, and energy efficiency EE of the battery at different temperatures were calculated using equations (1)-(3). The specific results are as follows: Figure 9 and Figure 10 As shown.

[0091]

[0092] comprehensive Figure 9 and Figure 10 It was found that after introducing 1.5% ammonium dihydrogen phosphate, the flow battery could operate stably at 55℃, and compared with the control group, the energy efficiency increased from 61.90% to 65.54%, an increase of 5.88%, demonstrating good cycle performance. Furthermore, the team observed that the operating performance of the thermally stable electrolyte changed with temperature, reaching a peak at 45℃, at which the cycle coulombic efficiency, voltage efficiency, and energy efficiency were 95.03%, 74.00%, and 68.22%, respectively.

[0093] After the phase change material is coupled for thermal storage, the increase in the system's energy density can be calculated according to equation (4).

[0094]

[0095] The original system stored chemical energy from flow batteries, while the current system stores energy that includes waste heat absorbed and stored by phase change materials and solar thermal energy, in addition to the energy stored in the original system.

[0096] The results show that, compared with commercial containerized flow battery energy storage systems, the energy density of this system is increased by 0.35 Wh / L, an improvement rate of 5.96%, which alleviates the problem of low energy density in flow battery energy storage.

[0097] Invention Examples

[0098] Example 1 of cyclic charge-discharge test:

[0099] Use a pipette to measure 60 ml of V 3.5+ The solution, with 1.5% ammonium dihydrogen phosphate additive added, was placed into the anode and cathode storage tanks of the cyclic charge-discharge test device at a 1:1 ratio. The peristaltic pump was started and set to a speed of 40 r / min. After the flow stabilized, nitrogen gas was introduced into the cathode storage tank to create a protective atmosphere, and the magnetic stirrer was started. The electrochemical workstation was started, and the operation step was set to 1) constant current charging with a current of 40 mA / cm². 2 1) Cut-off voltage is 1.7V; 2) Constant current discharge, current magnitude is 40mA / cm 2 3) Constant current charging, with a current of 100mA / cm². The cutoff voltage is 0.7V; 2 4) Constant current discharge, with a current of 100mA / cm. 2 The cutoff voltage is 0.7V; 5) Steps 3 and 4 are executed repeatedly for 10 cycles. The average energy efficiency, coulombic efficiency, and voltage efficiency obtained are 67.63%, 94.92%, and 73.29%, respectively.

[0100] Example 2 of cyclic charge-discharge test:

[0101] Compared to Example 1, only the temperature and the number of cycles were changed.

[0102] Use a pipette to measure 60 ml of V 3.5+ The solution, with 1.5% ammonium dihydrogen phosphate additive added, was placed into the anode and cathode storage tanks of the cyclic charge-discharge test device at a 1:1 ratio. The peristaltic pump was started and set to a speed of 40 r / min. After the flow stabilized, nitrogen gas was introduced into the cathode storage tank to create a protective atmosphere, and the magnetic stirrer was started. The water bath heating device was started and the temperature was set to 45℃. The electrochemical workstation was started, and the operation step was set to 1) constant current charging with a current of 40 mA / cm². 2 1) Cut-off voltage is 1.7V; 2) Constant current discharge, current magnitude is 40mA / cm 2 3) Constant current charging, with a current of 100mA / cm². The cutoff voltage is 0.7V; 2 4) Constant current discharge, with a current of 100mA / cm. 2 The cutoff voltage was 0.7V; 5) Steps 3 and 4 were executed repeatedly for 5 cycles. The average cycle energy efficiency, coulombic efficiency, and voltage efficiency were 68.22%, 95.03%, and 74.00%, respectively. This indicates that high temperature promotes the battery's charge and discharge performance.

[0103] Example 3 of cyclic charge-discharge test:

[0104] Compared to Example 1, only the temperature and the number of cycles were changed.

[0105] Use a pipette to measure 60 ml of V 3.5+ The solution, with 1.5% ammonium dihydrogen phosphate additive added, was placed into the anode and cathode storage tanks of the cyclic charge-discharge test device at a 1:1 ratio. The peristaltic pump was started and set to a speed of 40 r / min. After the flow stabilized, nitrogen gas was introduced into the cathode storage tank to create a protective atmosphere, and the magnetic stirrer was started. The water bath heating device was started and the temperature was set to 50℃. The electrochemical workstation was started, and the operation step was set to 1) constant current charging with a current of 40 mA / cm². 2 1) Cut-off voltage is 1.7V; 2) Constant current discharge, current magnitude is 40mA / cm 2 3) Constant current charging, with a current of 100mA / cm². The cutoff voltage is 0.7V; 2 4) Constant current discharge, with a current of 100mA / cm. 2 The cutoff voltage is 0.7V; 5) Execute steps 3 and 4 repeatedly for 5 cycles. The average cycle energy efficiency, coulombic efficiency, and voltage efficiency are 66.87%, 93.26%, and 73.84%, respectively. This indicates that the battery performance is slightly lower at 50℃ compared to room temperature.

[0106] Example 4 of cyclic charge-discharge test:

[0107] Compared to Example 1, only the temperature and the number of cycles were changed.

[0108] Use a pipette to measure 60 ml of V 3.5+ The solution, with 1.5% ammonium dihydrogen phosphate additive added, was placed into the anode and cathode storage tanks of the cyclic charge-discharge test device at a 1:1 ratio. The peristaltic pump was started and set to a speed of 40 r / min. After the flow stabilized, nitrogen gas was introduced into the cathode storage tank to create a protective atmosphere, and the magnetic stirrer was started. The water bath heating device was started and the temperature was set to 55℃. The electrochemical workstation was started, and the operation step was set to 1) constant current charging with a current of 40 mA / cm². 2 1) Cut-off voltage is 1.7V; 2) Constant current discharge, current magnitude is 40mA / cm 2 3) Constant current charging, with a current of 100mA / cm². The cutoff voltage is 0.7V; 2 4) Constant current discharge, with a current of 100mA / cm. 2The cutoff voltage is 0.7V; 5) Steps 3 and 4 are executed repeatedly for 5 cycles. The average cycle energy efficiency, coulombic efficiency, and voltage efficiency are 65.54%, 93.62%, and 72.24%, respectively. This indicates that the battery performance decreases slightly at 55°C compared to room temperature. Combined with Examples 1-4, the optimal operating temperature for the battery is approximately 45°C.

[0109] Cyclic charge-discharge test comparison example 1:

[0110] Compared to Example 4, the only difference is whether or not the electrolyte contains additives.

[0111] Use a pipette to measure 60 ml of V 3.5+ The solutions were placed into the anode and cathode storage tanks of the cyclic charge-discharge test device at a 1:1 ratio. The peristaltic pump was started and the speed was set to 40 r / min. After the flow stabilized, nitrogen gas was introduced into the cathode storage tank to create a protective atmosphere, and the magnetic stirrer was started. The water bath heating device was started and the temperature was set to 55℃. The electrochemical workstation was started and the operation step was set to 1) constant current charging with a current of 40 mA / cm². 2 1) Cut-off voltage is 1.7V; 2) Constant current discharge, current magnitude is 40mA / cm 2 3) Constant current charging, with a current of 100mA / cm². The cutoff voltage is 0.7V; 2 The cutoff voltage was 1.7V; 4) Constant current discharge, with a current of 100mA / cm² and a cutoff voltage of 0.7V; 5) Steps 3 and 4 were executed cyclically for 5 cycles. The average cycle energy efficiency, coulombic efficiency, and voltage efficiency were 61.90%, 90.73%, and 70.35%, respectively. This indicates that the vanadium electrolyte containing additives has better charge-discharge performance at high temperatures. Specific results are still available. Figure 9 and Figure 10 .

[0112] Thermal stability test example 1:

[0113] Measure 13.5 ml of V using a pipette. 5+ Solution and 1.5ml V 4+ The solution was thoroughly mixed and divided into three equal portions of 5 ml each, placed in storage bottles. Ammonium dihydrogen phosphate additives with mass fractions of 0.5%, 1%, and 1.5% were added to the three portions, respectively. The storage bottles were then ultrasonically treated for 10 minutes. The bottles were removed and placed in a 50°C water bath. The time to first precipitation of vanadium solutions containing 0.5%, 1%, and 1.5% ammonium dihydrogen phosphate additives was observed to be 25, 50, and 62 hours, respectively. This indicates that at 50°C, the high-temperature resistance of the vanadium electrolyte increases with increasing ammonium dihydrogen phosphate concentration.

[0114] Thermal stability test example 2:

[0115] Compared to Example 1, only the type of additive was changed.

[0116] Measure 13.5 ml of V using a pipette. 5+ Solution and 1.5ml V 4+ The solution was thoroughly mixed and divided into three equal portions of 5 ml each, placed in storage bottles. Diammonium hydrogen phosphate additives with mass fractions of 0.5%, 1%, and 1.5% were added to the three portions, respectively. The storage bottles were then ultrasonically treated for 10 minutes. The bottles were removed and placed in a 50°C water bath. The time to first precipitation of vanadium solutions containing 0.5%, 1%, and 1.5% diammonium hydrogen phosphate additives was observed to be 25, 47, and 56 hours, respectively. This indicates that at 50°C, the high-temperature resistance of the vanadium electrolyte increases with increasing diammonium hydrogen phosphate concentration, but the effect is not as good as with diammonium dihydrogen phosphate.

[0117] Thermal stability test example 3:

[0118] Compared to Example 1, only the test temperature was changed.

[0119] Measure 13.5 ml of V using a pipette. 5+ Solution and 1.5ml V 4+ The solution was thoroughly mixed and divided into three equal portions of 5 ml each, placed in storage bottles. Ammonium dihydrogen phosphate additives with mass fractions of 0.5%, 1%, and 1.5% were added to the three portions, respectively. The storage bottles were then ultrasonically treated for 10 minutes. The bottles were removed and placed in a 55°C water bath. The time to first precipitation of vanadium solutions containing 0.5%, 1%, and 1.5% ammonium dihydrogen phosphate additives was observed to be 10, 22, and 35 hours, respectively. This indicates that at 55°C, the high-temperature resistance of the vanadium electrolyte increases with increasing ammonium dihydrogen phosphate concentration.

[0120] Thermal stability test example 4:

[0121] Compared to Example 2, only the test temperature was changed.

[0122] Measure 13.5 ml of V using a pipette. 5+ Solution and 1.5ml V 4+The solution was thoroughly mixed and divided into three equal portions of 5 ml each, placed in storage bottles. Diammonium hydrogen phosphate additives with mass fractions of 0.5%, 1%, and 1.5% were added to the three portions, respectively. The storage bottles were then ultrasonically treated for 10 minutes. The bottles were removed and placed in a 55°C water bath. The time to first precipitation of vanadium solutions containing 0.5%, 1%, and 1.5% diammonium hydrogen phosphate additives was observed to be 8, 9, and 22 hours, respectively. This indicates that at 55°C, the high-temperature resistance of the vanadium electrolyte increases with increasing diammonium hydrogen phosphate concentration, but the effect is not as good as with diammonium hydrogen phosphate.

[0123] Thermal stability test comparison example 1:

[0124] Compared to Example 1, the only difference is whether or not additives are included.

[0125] Measure 4.5 ml of V using a pipette. 5+ Solution and 0.5ml V 4+ The solution was placed in a storage bottle. The storage bottle was ultrasonically treated in an ultrasonic cleaning device for 10 minutes. The storage bottle was then removed and placed in a 50°C water bath. The time for the first precipitation of vanadium solution was observed to be 8 hours. Comparing Example 1 and Example 2, it is shown that the additive effectively promotes the high-temperature resistance of the vanadium electrolyte.

[0126] Thermal stability test comparison example 2:

[0127] Compared to Example 3, the only difference is whether or not additives are included.

[0128] Measure 4.5 ml of V using a pipette. 5+ Solution and 0.5ml V 4+ The solution was placed in a storage bottle. The storage bottle was ultrasonically treated in an ultrasonic cleaning device for 10 minutes. The storage bottle was then removed and placed in a 55°C water bath. The time for the first precipitation of vanadium solution was observed to be 4 hours. Comparing Examples 3 and 4, it is shown that the additive effectively promotes the high-temperature resistance of the vanadium electrolyte.

[0129] Based on the above thermal stability test results, using 1.5% ammonium dihydrogen phosphate additive can maximize the high-temperature resistance of vanadium electrolyte.

[0130] High-Temperature Operation Simulation Experiment of Energy Storage System

[0131] Take V 4+ V 3+ The solutions were mixed in a 1:1 ratio to obtain 0.85 mol / L VO. 2++ 0.85 mol / LV 3++ 4 mol / L H2SO4 solution, abbreviated as V 3.5+ Solution.

[0132] To the V 3.5+ Add 0-1.5% of any commonly used electrolyte additive, such as dihydrogen phosphate, to the solution and sonicate it in an ultrasonic cleaning device for 10-15 minutes to obtain V containing the additive. 3.5+ Solution.

[0133] The V containing additives 3.5+ The solution was placed in the anode and cathode storage tanks of the cyclic charge-discharge test device at a 1:1 ratio.

[0134] The cyclic charge-discharge testing device includes the cyclic electrolysis device and the water bath device. Both the anode and cathode storage tanks in the cyclic electrolysis device are placed in the water bath.

[0135] Start the peristaltic pump and set the speed to 40-60 r / min. Pour nitrogen gas into the cathode storage tank to create a protective atmosphere. After the flow stabilizes, start the water bath heating device and set the temperature to 25-55℃.

[0136] After the water bath temperature stabilizes, start the electrochemical workstation and set the operation step to 1) constant current charging, with a current of 40-60 mA / cm. 2 1) Cut-off voltage is 1.7-1.9V; 2) Constant current discharge, with a current of 40-60mA / cm. 2 3) Constant current charging, with a current of 80-100mA / cm. The cutoff voltage is 0.6-0.7V; 2 4) Constant current discharge, with a current of 80-100 mA / cm². The cutoff voltage is 1.7-1.9V; 2 The cutoff voltage is 0.6-0.7V; 5) Repeat steps 3 and 4 5-10 times. Record the voltage-time curves during the cyclic charge-discharge process, and calculate the charge-discharge energy efficiency, voltage efficiency, and coulombic efficiency. Experiments show that the present invention has good cycle performance. Under operating conditions of 55℃, compared with the original, the energy density of the battery is increased by 5.96%, and the energy efficiency is increased by 5.88%.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. 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 be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A flow battery energy storage system coupled with phase change thermal storage, characterized in that: Includes cathode storage tank, anode storage tank, high-temperature phase change cavity, low-temperature phase change cavity, fuel cell stack and control system; The high-temperature zone phase change cavity is equipped with a high-temperature zone cathode heat exchange tube and a high-temperature zone anode heat exchange tube, and is filled with a high-temperature zone phase change material. The low-temperature zone phase change cavity is equipped with a low-temperature zone cathode heat exchange tube and a low-temperature zone anode heat exchange tube, and is filled with a low-temperature zone phase change material. The melting point of the phase change material in the high-temperature region is higher than the optimal operating temperature of the system, and the melting point of the phase change material in the low-temperature region is lower than the optimal operating temperature of the system. The outlet pipe of the cathode storage tank is connected to one end of the low-temperature zone cathode heat exchange tube, and a cathode booster pump is installed on it. The other end of the low-temperature zone cathode heat exchange tube is connected to the cathode side inlet pipe of the fuel cell stack. The cathode side outlet pipe of the fuel cell stack is connected to the return pipe of the cathode storage tank and one end of the high-temperature zone cathode heat exchange tube through a cathode electromagnetic three-way valve. The other end of the high-temperature zone cathode heat exchange tube is connected to the cathode storage tank. The outlet pipe of the anode storage tank is connected to one end of the low-temperature zone anode heat exchange tube, and an anode booster pump is installed on it. The other end of the low-temperature zone anode heat exchange tube is connected to the anode side inlet pipe of the fuel cell stack. The anode side outlet pipe of the fuel cell stack is connected to the return pipe of the anode storage tank and one end of the high-temperature zone anode heat exchange tube through an anode solenoid three-way valve. The other end of the high-temperature zone anode heat exchange tube is connected to the anode storage tank. The control system is electrically connected to the cathode solenoid three-way valve, the anode solenoid three-way valve, the cathode booster pump, and the anode booster pump, respectively.

2. The flow battery energy storage system coupled with phase change thermal storage according to claim 1, characterized in that: The control system includes: A temperature sensor is used to detect the temperature of the electrolyte and generate an electrical signal. An on-off controller receives electrical signals from a temperature sensor; The DC contactor receives electrical signals from the on / off controller and reacts based on the control of the on / off controller to control the on / off of the circuit between the DC power supply and the solenoid three-way valve, thereby changing the outlet of the solenoid three-way valve and the direction of electrolyte flow. The PID controller receives electrical signals from the temperature sensor and is used to control the speed of the booster pump. Switching power supply, used to power PID controller and on-off controller; The computer is connected to the PID controller and the on / off controller.

3. The flow battery energy storage system coupled with phase change thermal storage according to claim 2, characterized in that: The control system has two control loops. The first control loop controls the opening of the solenoid three-way valve. When the temperature sensor detects that the electrolyte temperature exceeds the set value, the on / off controller controls the DC contactor to connect the DC power supply to the solenoid three-way valve, energizing the valve and turning its opening to connect directly to the pipeline of the storage tank. Conversely, when the temperature sensor detects that the electrolyte temperature is below the set value, the on / off controller controls the DC contactor to disconnect the DC power supply from the solenoid three-way valve, de-energizing the valve and turning its opening to connect to the heat exchange tube in the high-temperature zone, thus allowing the valve to open. The electrolyte flows through a phase change material heated by solar energy, raising its temperature. The second control loop controls the electrolyte flow rate. The PID controller in this second control loop compares the electrolyte temperature with the set temperature in the PID controller. When the difference between the two is large, the PID controller increases the speed of the booster pump to enhance the heat transfer coefficient of the electrolyte and achieve rapid heat exchange between the electrolyte and the phase change material. Conversely, when the difference between the two is small, the PID controller decreases the speed of the booster pump to better maintain the electrolyte temperature at the set value.

4. The flow battery energy storage system coupled with phase change thermal storage according to claim 3, characterized in that: It also includes a container, in which the cathode storage tank, anode storage tank, fuel cell stack and cryogenic phase change chamber are all located, and the high-temperature phase change chamber is located on the top of the container.

5. The flow battery energy storage system coupled with phase change thermal storage according to claim 4, characterized in that: Both the high-temperature zone cathode heat exchange tube and the high-temperature zone anode heat exchange tube are arranged in a serpentine manner in the high-temperature zone phase change cavity.

6. The flow battery energy storage system coupled with phase change thermal storage according to claim 5, characterized in that: Both the low-temperature zone cathode heat exchange tube and the low-temperature zone anode heat exchange tube are arranged in a serpentine manner in the low-temperature zone phase change cavity.

7. The flow battery energy storage system coupled with phase change thermal storage according to claim 6, characterized in that: Photothermal conversion materials are added to phase change materials in the high-temperature region to enhance their photothermal conversion capabilities.

8. An energy storage method employing a flow battery energy storage system coupled with phase change thermal storage as described in claim 1, characterized in that: When the system is running, the booster pump is energized and rotates, drawing electrolyte from the electrolyte storage tank. Under the action of the booster pump, the electrolyte first flows through the low-temperature zone heat exchange tube, where it exchanges heat with the low-temperature zone phase change material. Then it enters the fuel cell stack. After undergoing a redox reaction in the fuel cell stack, the electrolyte flows through the solenoid three-way valve, which is controlled by the control system. When the electrolyte temperature is lower than the set temperature, the solenoid three-way valve controls the electrolyte to flow through the high-temperature zone heat exchange tube, absorbing the light and heat stored in the high-temperature zone phase change material. Conversely, when the electrolyte temperature is higher than the set temperature, the solenoid three-way valve controls it to bypass the high-temperature zone phase change material and flow directly into the storage tank, thus completing one cycle.

9. The energy storage method according to claim 8, characterized in that: The electrolyte concentration ratio is 1.7M vanadium ions, 4M sulfate ions, and 1.5% ammonium dihydrogen phosphate additive.

Images