A flow battery system architecture and a method for regulating electrolyte temperature thereof

Abstract

The application discloses a kind of liquid flow battery system architecture and the method for realizing electrolyte temperature regulation thereof, by increasing electrolyte small circulation loop in positive electrolyte loop and negative electrolyte loop respectively, meet the demand of various temperature conditions, quickly and economically control the electrolyte temperature entering the stack, improve reliability and economy, reduce the risk of various failures of liquid flow battery system.

Description

TECHNICAL FIELD

[0001] The present application relates to, but is not limited to, the technical field of electrochemical energy storage systems, and in particular to a flow battery system architecture and a method for regulating electrolyte temperature. BACKGROUND

[0002] A flow battery is an electrochemical energy storage device that stores and releases energy by dissolving active substances in electrolyte and circulating the electrolyte between the storage tank and the stack. Flow batteries have the characteristics of energy and power decoupling, long service life, and suitability for large-scale energy storage. Among the various technical routes of flow batteries, all-vanadium redox flow batteries use vanadium ions as active substances in both positive and negative electrodes, which can avoid electrolyte cross contamination and have a long cycle life. It is currently the most widely used and most mature flow battery.

[0003] All-vanadium redox flow batteries are a large-scale long-time energy storage technology with a narrow temperature window, generally between 20℃ and 40℃. When the temperature is too high, V2O5 solids are easily precipitated from the positive electrolyte, which may cause liquid channel blockage. When the temperature is too low, the battery polarization increases, which affects the charge and discharge power, efficiency and capacity. When the temperature is too low, VSO4 crystals are easily precipitated from the negative electrolyte, which may also cause liquid channel blockage.

[0004] Therefore, controlling the temperature of the positive and negative electrolytes is crucial for the stable operation of the energy storage system and the prevention of early failure of the stack. However, the electrolyte environment is strongly acidic, which poses a challenge to the selection of heat exchanger materials. SUMMARY

[0005] The present application provides a flow battery system architecture and a method for regulating electrolyte temperature, which can easily control the temperature of the electrolyte, avoid the risk of damage to the stack or system caused by temperature abnormalities in the stack, and thus meet the use requirements in complex application environments.

[0006] The present application provides a flow battery system architecture, comprising: a stack, and a positive electrolyte circuit and a negative electrolyte circuit connected to the positive side and the negative side of the stack, respectively; wherein,

[0007] The positive electrolyte circuit comprises a first positive electrolyte small circulation branch and a second positive electrolyte small circulation branch; wherein two ends of the first positive electrolyte small circulation branch are connected to the main circuit section between the positive liquid inlet valve and the positive liquid return valve, and a first positive small circulation branch valve is arranged on the first positive electrolyte small circulation branch for controlling opening, closing and opening degree adjustment of the first positive electrolyte small circulation branch; two ends of the second positive electrolyte small circulation branch are connected to the positive liquid inlet of the stack and the positive liquid outlet of the stack, and a second positive small circulation branch valve is arranged on the second positive electrolyte small circulation branch for controlling opening or closing of the second positive electrolyte small circulation branch.

[0008] The negative electrolyte circuit comprises a first negative electrolyte small circulation branch and a second negative electrolyte small circulation branch; wherein two ends of the first negative electrolyte small circulation branch are connected to the main circuit section between the negative liquid inlet valve and the negative liquid return valve, and a first negative small circulation branch valve is arranged on the first negative electrolyte small circulation branch for controlling opening, closing and opening degree adjustment of the first negative electrolyte small circulation branch; two ends of the second negative electrolyte small circulation branch are connected to the negative liquid inlet of the stack and the negative liquid outlet of the stack, and a second negative small circulation branch valve is arranged on the second negative electrolyte small circulation branch for controlling opening or closing of the second negative electrolyte small circulation branch.

[0009] In an exemplary example, the positive electrolyte circuit further comprises: a positive main circuit; the positive main circuit is a closed loop composed of a positive liquid tank, the positive liquid inlet valve, a positive heat exchanger, a positive liquid pump, the positive liquid inlet of the stack, the positive flow channel of the stack, the positive liquid outlet of the stack, and the positive liquid return valve connected in sequence.

[0010] The negative electrolyte circuit further comprises: a negative main circuit; the negative main circuit is a closed loop composed of a negative liquid tank, the negative liquid inlet valve, a negative heat exchanger, a negative liquid pump, the negative liquid inlet of the stack, the negative flow channel of the stack, the negative liquid outlet of the stack, and the negative liquid return valve connected in sequence.

[0011] In an exemplary example, further comprising:

[0012] A positive liquid injection / liquid discharge valve for liquid injection or liquid discharge is further arranged before the positive liquid pump;

[0013] A negative liquid injection / liquid discharge valve for liquid injection or liquid discharge is further arranged before the negative liquid pump.

[0014] In an exemplary example, further comprising:

[0015] A first temperature sensor is arranged on the positive liquid tank, and a fourth temperature sensor is arranged on the negative liquid tank; and / or,

[0016] a second temperature sensor is arranged on the positive electrode inlet pipeline of the stack, and a fifth temperature sensor is arranged on the negative electrode inlet pipeline of the stack; and / or,

[0017] a third temperature sensor is arranged on the positive electrode outlet pipeline of the stack, and a sixth temperature sensor is arranged on the negative electrode outlet pipeline of the stack.

[0018] In an exemplary example, the heat exchange pipe material of the positive electrode heat exchanger is titanium alloy or polytetrafluoroethylene pipe; and the material of the negative electrode heat exchanger is graphite or silicon carbide or polytetrafluoroethylene pipe.

[0019] In an exemplary example, when the first positive electrode small circulation branch valve and the second positive electrode small circulation branch valve are completely closed, and the positive electrode liquid inlet valve and the positive electrode liquid return valve are opened, the positive electrode electrolyte flows out from the positive electrode liquid tank, flows through the positive electrode heat exchanger, the positive electrode liquid pump, the stack, and flows back to the positive electrode liquid tank through the positive electrode liquid return valve, and the positive electrode electrolyte circuit constitutes a positive electrode large circulation loop.

[0020] When the first negative electrode small circulation branch valve and the second negative electrode small circulation branch valve are completely closed, and the negative electrode liquid inlet valve and the negative electrode liquid return valve are opened, the negative electrode electrolyte flows out from the negative electrode liquid tank, flows through the negative electrode heat exchanger, the negative electrode liquid pump, the stack, and flows back to the negative electrode liquid tank through the negative electrode liquid return valve, and the negative electrode electrolyte circuit constitutes a negative electrode large circulation loop.

[0021] In an exemplary example, when the first positive electrode small circulation branch valve and the second positive electrode small circulation branch valve are completely opened, and the positive electrode liquid inlet valve and the positive electrode liquid return valve are closed, the positive electrode electrolyte flows out from the positive electrode liquid pump, flows through the second positive electrode small circulation branch, the first positive electrode small circulation branch, the positive electrode heat exchanger, and flows back to the positive electrode liquid pump, and the positive electrode electrolyte circuit constitutes a positive electrode first small circulation loop.

[0022] When the first negative electrode small circulation branch valve and the second negative electrode small circulation branch valve are completely opened, and the negative electrode liquid inlet valve and the negative electrode liquid return valve are closed, the negative electrode electrolyte flows out from the negative electrode liquid pump, flows through the second negative electrode small circulation branch, the first negative electrode small circulation branch, the negative electrode heat exchanger, and flows back to the negative electrode liquid pump, and the negative electrode electrolyte circuit constitutes a negative electrode first small circulation loop.

[0023] In an exemplary example, when the second positive electrode small circulation branch valve is closed, the positive electrode electrolyte flows out from the positive electrode liquid pump, flows through the stack, the first positive electrode small circulation branch, the positive electrode heat exchanger, and flows back to the positive electrode liquid pump, and the positive electrode electrolyte circuit constitutes a positive electrode second small circulation loop.

[0024] When the second negative electrode small circulation branch valve is closed, the negative electrode electrolyte flows out from the negative electrode liquid pump, flows through the fuel cell stack, the first negative electrode small circulation branch, and the negative electrode heat exchanger, and flows back to the negative electrode liquid pump and the fuel cell stack. The negative electrode electrolyte circuit constitutes the second negative electrode small circulation circuit.

[0025] In one exemplary instance, when the positive electrode inlet valve and the positive electrode return valve are opened, and the opening degree of the first positive electrode small circulation branch valve is adjusted, a portion of the positive electrode electrolyte can be returned to the positive electrode tank.

[0026] When the negative electrode inlet valve and the negative electrode return valve are opened, and the opening degree of the first negative electrode small circulation branch valve is adjusted, a portion of the negative electrode electrolyte can be returned to the negative electrode tank.

[0027] In one exemplary instance, when the first positive electrode small circulation branch valve is completely closed and the second positive electrode small circulation branch valve, the positive electrode inlet valve, and the positive electrode return valve are completely open, the positive electrode electrolyte flows out of the positive electrode tank, flows through the positive electrode heat exchanger, the positive electrode pump, and the second positive electrode small circulation branch, and then flows back to the positive electrode tank. The positive electrode electrolyte circuit constitutes the third positive electrode small circulation circuit.

[0028] When the first negative electrode small circulation branch valve is completely closed, and the second negative electrode small circulation branch valve, the negative electrode inlet valve, and the negative electrode return valve are completely open, the negative electrode electrolyte flows out from the negative electrode tank, flows through the negative electrode heat exchanger, the negative electrode pump, and the second negative electrode small circulation branch, and then flows back to the negative electrode tank. The negative electrode electrolyte circuit constitutes the third negative electrode small circulation circuit.

[0029] In one exemplary instance, when it is necessary to inject liquid into the positive electrode tank, the pipe interface of the ton or tank truck is connected to the positive electrode injection / drain valve, the return valve of the positive electrode tank and the second positive electrode small circulation branch valve are opened, and the positive electrode inlet valve and the first positive electrode small circulation branch valve are closed. The positive electrode injection / drain valve is opened and the positive electrode liquid pump is started, and the electrolyte is directly pumped into the positive electrode tank through the positive electrode liquid pump.

[0030] When it is necessary to inject liquid into the negative electrode liquid tank, connect the ton container or liquid tanker to the pipeline interface of the negative electrode injection / drain valve, open the negative electrode liquid tank return valve and the second negative electrode small circulation branch valve, close the negative electrode inlet valve and the first negative electrode small circulation branch valve, open the negative electrode injection / drain valve and start the negative electrode liquid pump, and the electrolyte is directly pumped into the negative electrode liquid tank through the negative electrode liquid pump.

[0031] This application embodiment also provides a method for realizing electrolyte temperature regulation, based on the flow battery system architecture described in any of the above claims; including:

[0032] obtaining the temperature of electrolyte in the positive electrolyte tank, the temperature of electrolyte in the negative electrolyte tank, the temperature of electrolyte entering the stack, and the temperature of electrolyte flowing out of the stack;

[0033] According to the obtained temperature information, the positive electrolyte circuit and / or the negative electrolyte circuit are controlled to control the temperature of positive electrolyte entering the stack and / or the temperature of negative electrolyte entering the stack.

[0034] In an exemplary example, the temperature of electrolyte in the positive electrolyte tank and the temperature of electrolyte in the negative electrolyte tank are collected in real time by the positive electrolyte tank temperature sensor T1 and the negative electrolyte tank temperature sensor T4 in the flow battery system architecture.

[0035] The temperature of electrolyte entering the stack and the temperature of electrolyte flowing out of the stack are collected by the stack positive electrolyte inlet temperature sensor T2 and the electrolyte outlet temperature sensor T3, and the negative electrolyte inlet temperature sensor T5 and the electrolyte outlet temperature sensor T6 in the flow battery system architecture.

[0036] In an exemplary example, when the temperature of the positive electrolyte tank or the positive side of the stack is higher than the preset upper limit or lower than the preset lower limit, the first positive small circulation branch valve in the flow battery system architecture is controlled to be closed, the second positive small circulation branch valve in the flow battery system architecture is controlled to be opened, and the positive electrolyte pump is started to make the positive electrolyte circulate between the positive electrolyte tank, the positive heat exchanger and the second positive small circulation branch, forming a positive third small circulation loop, so as to restore the temperature of positive electrolyte to a normal range.

[0037] When the temperature of the negative electrolyte tank or the negative side of the stack is higher than the preset upper limit or lower than the preset lower limit, the first negative small circulation branch valve in the flow battery system architecture is controlled to be closed, the second negative small circulation branch valve in the flow battery system architecture is controlled to be opened, and the negative electrolyte pump is started to make the negative electrolyte circulate between the negative electrolyte tank, the negative heat exchanger and the second negative small circulation branch, forming a negative third small circulation loop, so as to restore the temperature of negative electrolyte to a normal range.

[0038] When the temperature of the positive electrolyte tank is normal, but the temperature of positive electrolyte entering / exiting the stack is higher than the preset upper limit or lower than the preset lower limit, the positive electrolyte inlet valve and the positive electrolyte outlet valve in the flow battery system architecture are closed, the first positive small circulation branch valve and the second positive small circulation branch valve are opened, the positive electrolyte pump and the heat management module are started, and the positive electrolyte only circulates in the positive first small circulation loop; when the temperature of positive electrolyte is in a normal range, the second positive small circulation branch valve is closed, the positive electrolyte circulates in the positive second small circulation loop, and when the temperature of the stack is in a normal range, the electrolyte circulation is stopped.

[0039] When the negative liquid tank temperature is normal, but the negative inlet / outlet liquid temperature of the stack is higher than the preset upper limit or lower than the preset lower limit, the negative inlet valve and the negative return valve in the liquid flow battery system architecture are closed, the first negative small circulation branch valve and the second negative small circulation branch valve are opened, the negative liquid pump and the heat management module are started, and the negative electrolyte is circulated only in the negative first small circulation loop; when the negative electrolyte temperature is in the normal range, the second negative small circulation branch valve is closed, the negative electrolyte is circulated in the negative second small circulation loop, and the stack temperature is in the normal range, the electrolyte circulation is stopped.

[0040] In an exemplary example, further comprising:

[0041] When the positive liquid tank temperature deviates from the target range by a large margin, the opening degree of the positive inlet valve and the first positive small circulation loop valve is controlled, so that the electrolyte in the positive liquid tank and the electrolyte in the small circulation loop are mixed in a certain proportion, then enter the positive heat exchanger, and then are sent to the stack;

[0042] When the negative liquid tank temperature deviates from the target range by a large margin, the opening degree of the negative inlet valve and the first negative small circulation loop valve is controlled, so that the electrolyte in the negative liquid tank and the electrolyte in the small circulation loop are mixed in a certain proportion, then enter the negative heat exchanger, and then are sent to the stack.

[0043] The liquid flow battery system architecture provided by the embodiment of the application meets the demand of various temperature conditions, quickly and economically controls the electrolyte temperature entering the stack, improves the reliability and economy, and reduces the risk of various failures of the liquid flow battery system.

[0044] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application can be achieved and obtained by the structure particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0045] The accompanying drawings are used to provide a further understanding of the technical scheme of the present application, and constitute a part of the specification, and are used to explain the technical scheme of the present application together with the embodiments of the present application, and do not constitute a limitation to the technical scheme of the present application.

[0046] Figure 1 It is a schematic diagram of the composition architecture of the liquid flow battery energy storage system with the positive and negative liquid tanks and the heat exchanger in the related art;

[0047] Figure 2 It is a schematic diagram of the composition architecture of the liquid flow battery energy storage system with the positive heat exchanger in the related art;

[0048] Figure 3 is a schematic diagram of a composition architecture of a flow battery energy storage system containing positive and negative heat exchangers in the related art;

[0049] Figure 4 is a schematic diagram of a flow battery system architecture in the embodiments of the present application;

[0050] Figure 5 is a flowchart of a method for regulating electrolyte temperature in the embodiments of the present application;

[0051] Figure 6 is a schematic diagram of a normal electrolyte flow loop of a flow battery system in the embodiments of the present application;

[0052] Figure 7 is a schematic diagram of a positive first small circulation loop and a negative first small circulation loop in the embodiments of the present application;

[0053] Figure 8 is a schematic diagram of a positive second small circulation loop and a negative second small circulation loop in the embodiments of the present application;

[0054] Figure 9 is a schematic diagram of a positive third small circulation loop and a negative third small circulation loop in the embodiments of the present application;

[0055] Figure 10 is a schematic diagram of pumping electrolyte from a ton barrel or a tank truck to positive and negative electrolyte tanks in the embodiments of the present application. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solutions and advantages of the present application clearer and more apparent, the embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other as long as there is no conflict.

[0057] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The embodiments of the present application are shown in the drawings. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0059] It can be understood that the terms "first", "second" used in the present application are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can be explicitly or implicitly included at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly specified.

[0060] It can be understood that "connection" in the following embodiments should be understood as "electrical connection", "communication connection" and the like if the connected circuits, modules, units and the like have transmission of electrical signals or data between each other.

[0061] As used herein, the singular forms "a", "an" and "the" can also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms "include", "contain" or "have" and the like specify the presence of stated features, integers, steps, operations, components, parts or combinations thereof, but do not exclude the presence or addition of one or more other features, integers, steps, operations, components, parts or combinations thereof. At the same time, the term "and / or" used in the present specification includes any and all combinations of the related listed items.

[0062] The steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions. Also, although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that here.

[0063] In early liquid flow batteries, a nylon tube heat exchanger is usually used, which directly immerses the heat exchanger in the positive and negative electrolyte tanks, passes cooling liquid in the nylon tube, and exchanges heat with the environment through the positive and negative thermal management system, as shown in Figure 1 This way has good corrosion resistance, so it is widely used in early round tank liquid flow battery energy storage systems. However, the thermal conductivity of nylon material is low, resulting in low heat exchange efficiency. At the same time, the round tank energy storage system often needs to be placed indoors, that is, when the project is implemented, a building must be built first, and then the energy storage system is put into it, which limits the application scenarios of the project. In addition, since there are usually tens of cubic meters of electrolyte in the liquid tank, it takes a long time for the thermal management system to heat or cool the electrolyte to the appropriate temperature range, which is inconvenient to use. Especially for square tanks, the flow of electrolyte is more complex, and the temperature distribution of electrolyte in the liquid tank is often uneven, and there may be a large difference between the values of the temperature sensor on the liquid tank and the inlet stack temperature sensor. This difference is easy to cause the stack to overheat.

[0064] With the development of the flow battery industry, containerized energy storage systems have gradually become popular. This kind of skid-mounted product can be used on site after debugging in the factory, without the need for building conditions, and is therefore popular in the market. In order to improve the energy density, the skid-mounted product usually uses a square electrolyte storage tank, which is no longer convenient to use a nylon tube heat exchanger. Currently, the industry generally uses a titanium tube heat exchanger in the positive electrolyte circuit, as shown in Figure 2 The titanium material can form a dense titanium oxide protective layer on the surface, which can resist corrosion of the positive electrolyte, and the heat exchanger can directly pass in the refrigerant, with high heat exchange efficiency. By controlling the positive heat exchanger and the positive thermal management system, the temperature of the positive electrolyte entering the stack can be adjusted. However, there is no suitable metal material to make a heat exchanger for the negative circuit, so the temperature of the negative electrolyte cannot be directly controlled. When the temperature of the negative electrolyte is too low, only the heating device outside the negative tank can be relied on to increase the temperature to avoid crystallization; when the temperature of the negative electrolyte is too high, the overall temperature of the stack can only be indirectly controlled by reducing the temperature of the positive electrolyte entering the stack. This control method is difficult and can easily cause the stack to overheat or cool down, increasing the risk of stack failure.

[0065] In order to further improve the thermal management performance, some systems set heat exchangers in both the positive and negative electrolyte circuits, as shown in Figure 3 The material of the negative heat exchanger can be graphite tube, silicon carbide tube or polytetrafluoroethylene tube, etc. These materials have their own shortcomings, such as poor air tightness, low strength or low thermal conductivity, but in the case of setting heat exchangers in both the positive and negative electrolyte circuits, the temperature of the electrolyte entering the stack can be better controlled. However, this architecture still has deficiencies under certain working conditions. For example, when the system is initially assembled and prepared for debugging, if it is in summer, the temperature of the electrolyte in the positive and negative tanks is often too high; if it is in winter, the electrolyte may be below zero. At this time, it takes a long time to circulate the electrolyte, or devices with larger heat exchange area and higher cooling and refrigeration power need to be configured, in order to adjust the temperature of the electrolyte to a range suitable for the operation of the stack. For another example, after the system is fully charged, if it cannot be discharged for a long time due to external device failure, in the summer case, the temperature of the electrolyte in the positive and negative tanks will gradually increase, and there is a risk of solid precipitation in the positive tank, the pipeline and the stack; in the winter case, the temperature of the electrolyte in the positive and negative tanks may drop to below zero, and crystals may precipitate in the negative tank, the pipeline and the stack, eventually leading to stack failure. At this time, although the positive and negative liquid pumps, heat exchangers and thermal management systems can be started to control the temperature of the electrolyte, the charged electrolyte will undergo significant self-discharge when flowing through the stack, resulting in energy loss and economic loss to the user.

[0066] In a flow battery, the electrolyte is not fixed inside the battery, but is stored in an external tank, and is constantly circulated into the stack through a pipeline and a pump to undergo electrochemical reaction with the electrode, thereby realizing charging and discharging. As shown in Figure 3As shown, the positive electrolyte circuit refers to a closed circulation path from the positive liquid tank, through the pipeline, valve, liquid pump, heat exchanger, into the positive flow channel of the stack, and then out of the stack, through the return liquid pipeline and return liquid valve, and back to the positive liquid tank. The negative electrolyte circuit refers to a closed circulation path from the negative liquid tank, through the pipeline, valve, liquid pump, heat exchanger, into the negative flow channel of the stack, and then out of the stack, through the return liquid pipeline and return liquid valve, and back to the negative liquid tank.

[0067] In summary, the existing vanadium flow battery thermal management system has the following problems: Figure 1 the in-tank nylon heat exchanger shown in the figure, Figure 2 the positive titanium tube heat exchanger shown in the figure, and Figure 3 the positive and negative double heat exchanger shown in the figure, and the like, although the ability to regulate the temperature of the electrolyte has been gradually improved, there are still problems such as low heat exchange efficiency, insufficient negative temperature control, difficulty in coping with extreme working conditions, and serious self-discharge loss, which are difficult to fully meet the use requirements in complex application environments.

[0068] Therefore, the embodiments of the present application provide a flow battery system architecture, as shown in Figure 4 at least comprising: a stack, and a positive electrolyte circuit and a negative electrolyte circuit connected to the positive and negative sides of the stack, respectively; wherein,

[0069] The positive electrolyte circuit includes a first positive electrolyte small circulation branch and a second positive electrolyte small circulation branch. The first positive electrolyte small circulation branch is a bypass branch, and its two ends are connected to the main circuit section between the positive liquid inlet valve and the positive liquid return valve. A first positive small circulation branch valve is provided on the first positive electrolyte small circulation branch for controlling the opening, closing and opening degree adjustment of the first positive electrolyte small circulation branch. The second positive electrolyte small circulation branch is a bypass branch, and its two ends are connected to the positive liquid inlet of the stack and the positive liquid outlet of the stack. A second positive small circulation branch valve is provided on the second positive electrolyte small circulation branch for controlling the opening or closing of the second positive electrolyte small circulation branch. That is, in the positive electrolyte circuit, the electrolyte of the positive liquid tank enters the positive electrolyte circuit through the positive liquid inlet valve, and before returning to the positive liquid tank from the positive liquid return valve, the first positive electrolyte small circulation branch is arranged, and the first positive small circulation branch valve is provided in the first positive electrolyte small circulation branch, as shown in Figure 4 for opening, closing and adjusting the opening degree of the first positive electrolyte small circulation branch, and by adjusting the valve opening degree, the electrolyte in the liquid tank and the electrolyte in the circulation are mixed in proportion, avoiding direct impact on the stack when the temperature difference is too large, and preventing local overcooling or overheating of the stack. Between the positive liquid inlet and the liquid return port of the stack, the second positive electrolyte small circulation branch is also arranged, and the second positive small circulation branch valve is provided in the second positive electrolyte small circulation branch, as shown in Figure 4The second positive electrode electrolyte small circulation branch valve is arranged in the second positive electrode electrolyte small circulation branch, and is used for opening or closing the second positive electrode electrolyte small circulation branch. In this way, when the electrolyte temperature is not suitable, only the local small circulation can be formed at the stack side to rapidly increase or decrease the temperature through the heat exchanger, and the electrolyte in the whole tank does not need to be adjusted to the suitable temperature.

[0070] In an exemplary example, as shown in Figure 4 The positive electrode electrolyte circuit further comprises: a positive electrode main circuit; and the positive electrode main circuit comprises a closed loop of a positive electrode tank, a positive electrode liquid inlet valve, a positive electrode heat exchanger, a positive electrode liquid pump, a positive electrode liquid inlet of the stack, a positive electrode flow channel of the stack, a positive electrode liquid outlet of the stack, and a positive electrode liquid return valve connected in sequence.

[0071] In an exemplary example, a positive electrode liquid injection / liquid discharge valve can be further arranged before the positive electrode liquid pump, and is used for system liquid injection or liquid discharge. The arrangement of the positive electrode liquid injection / liquid discharge valve facilitates the system to inject electrolyte at the user end (such as pumping the electrolyte from a ton barrel or a tank truck into the tank) or to discharge the electrolyte during maintenance. In this way, the electrolyte does not flow through the stack during the injection or liquid discharge process, and damage to the stack is avoided.

[0072] The negative electrode electrolyte circuit comprises a first negative electrode electrolyte small circulation branch and a second negative electrode electrolyte small circulation branch. The two ends of the first negative electrode electrolyte small circulation branch are respectively connected to a main circuit section between a negative electrode liquid inlet valve and a negative electrode liquid return valve. A first negative electrode small circulation branch valve is arranged in the first negative electrode electrolyte small circulation branch, and is used for controlling opening, closing and opening degree adjustment of the first negative electrode electrolyte small circulation branch. The two ends of the second negative electrode electrolyte small circulation branch are respectively connected to a negative electrode liquid inlet of the stack and a negative electrode liquid outlet of the stack. A second positive-negative small circulation branch valve is arranged in the second negative electrode electrolyte small circulation branch, and is used for controlling opening or closing of the second positive-negative electrolyte small circulation branch. That is, in the negative electrode electrolyte circuit, the structure is similar to that of the positive electrode electrolyte circuit. The first negative electrode electrolyte small circulation branch is arranged after the negative electrode liquid inlet valve and before the negative electrode liquid return valve. The first negative electrode small circulation branch valve is arranged in the first negative electrode electrolyte small circulation branch, and is used for opening, closing and adjusting the opening degree of the first negative electrode electrolyte small circulation branch. By adjusting the opening degree of the valve, the electrolyte in the tank and the electrolyte in the circulation are mixed in proportion, so that the electrolyte does not directly impact the stack when the temperature difference is too large, and the local overcooling or overheating of the stack is prevented. The second negative electrode electrolyte small circulation branch is arranged between the negative electrode liquid inlet and the liquid return port of the stack. The second negative electrode small circulation branch valve is arranged in the second negative electrode electrolyte small circulation branch, and can open or close the second negative electrode electrolyte small circulation branch. In this way, when the electrolyte temperature is not suitable, only the local small circulation can be formed at the stack side to rapidly increase or decrease the temperature through the heat exchanger, and the electrolyte in the whole tank does not need to be adjusted to the suitable temperature. Figure 4 Figure 4 The second negative electrode small circulation branch valve is arranged in the second negative electrode electrolyte small circulation branch, and is used for opening or closing the second negative electrode electrolyte small circulation branch. In this way, when the electrolyte temperature is not suitable, only the local small circulation can be formed at the stack side to rapidly increase or decrease the temperature through the heat exchanger, and the electrolyte in the whole tank does not need to be adjusted to the suitable temperature. ​

[0073] In an example, as shown in Figure 4 The negative electrolyte circuit further comprises: a negative main circuit; the negative main circuit is a closed circuit composed of a negative liquid tank, a negative liquid inlet valve, a negative heat exchanger, a negative liquid pump, a negative liquid inlet of the stack, a negative flow channel of the stack, a negative liquid outlet of the stack, and a negative liquid return valve connected in sequence.

[0074] In an example, a negative liquid injection / liquid discharge valve can be arranged before the negative liquid pump, for system liquid injection or liquid discharge. The arrangement of the negative liquid injection / liquid discharge valve facilitates the system to inject electrolyte at the user end (such as pumping the liquid tank from a ton barrel or a tank truck), or to discharge electrolyte during maintenance. In this way, the electrolyte does not flow through the stack during the injection or discharge process, avoiding damage to the stack.

[0075] The liquid flow battery system architecture provided by the embodiment of the application facilitates the control of the electrolyte temperature by simultaneously introducing a tank-side small circulation branch (with an adjustable valve) and a stack-side small circulation branch (with a switch valve) in the positive and negative electrolyte circuits, and cooperating with the pre-pump liquid injection / liquid discharge valve, thereby avoiding the risk of damage to the stack or system caused by temperature abnormalities of the stack, and thus well meeting the use requirements in complex application environments. The liquid flow battery system architecture provided by the embodiment of the application realizes rapid regulation and control of the electrolyte temperature, energy consumption reduction, inhibition of self-discharge during shutdown, and facilitation of liquid injection and liquid discharge, thereby ensuring the safety of the stack and improving the system efficiency and environmental adaptability.

[0076] In an example, as shown by the black thick line path in Figure 6 When the first positive small circulation branch valve, the second positive small circulation branch valve, the first negative small circulation branch valve, and the second negative small circulation branch valve are all closed, and the positive liquid inlet valve, the positive liquid return valve, the negative liquid inlet valve, and the negative liquid return valve are all opened, the positive electrolyte flows out of the positive liquid tank, flows through the positive liquid inlet valve, the positive heat exchanger, and the positive liquid pump, and then enters the stack, and then flows out of the stack, flows back to the positive liquid tank through the positive liquid return valve, at this time, the positive electrolyte circuit constitutes a positive large circulation circuit, i.e., a positive main circuit; the negative electrolyte flows out of the negative liquid tank, flows through the negative liquid inlet valve, the negative heat exchanger, and the negative liquid pump, and then enters the stack, and then flows out of the stack, and then flows back to the negative liquid tank through the negative liquid return valve, at this time, the negative electrolyte circuit constitutes a negative large circulation circuit, i.e., a negative main circuit. The positive large circulation circuit and the negative large circulation circuit constitute the electrolyte flow path in the normal charging and discharging process of the liquid flow battery system, and are the normal electrolyte flow circuit of the liquid flow battery system.

[0077] In an example, as shown in Figure 4As shown, the first positive electrode small circulation branch valve is located on the first positive electrode electrolyte small circulation branch between the positive electrode inlet valve and the positive electrode return valve. When the first positive electrode small circulation branch valve is open, the positive electrode electrolyte can flow back through the first positive electrode electrolyte small circulation branch and no longer flow back to the positive electrode tank. The second positive electrode small circulation branch valve forms the second positive electrode small circulation branch between the positive electrode inlet and the positive electrode outlet of the fuel cell stack. When the second positive electrode small circulation branch valve is open, the positive electrode electrolyte can flow directly from the positive electrode inlet to the positive electrode outlet of the fuel cell stack without entering the fuel cell stack.

[0078] When both the first and second positive electrode small circulation branch valves are fully open, and the positive electrode inlet valve and return valve of the positive electrode liquid tank are closed simultaneously, the positive electrode liquid pump is started. The positive electrode electrolyte flows out of the positive electrode liquid pump, flows through the second and first positive electrode small circulation branches, returns to the positive electrode heat exchanger, and then enters the inlet of the positive electrode liquid pump. Figure 7 As shown by the thick black line on the left, the positive electrolyte circuit forms the first small circulation loop at this point. At this time, the positive electrolyte thermal management system can cool or heat the electrolyte in the positive electrode pipeline. When the flow battery system has not been charged or discharged for a long time in summer, the electrolyte temperature in the positive electrode pipeline may be high, posing a risk of solid material precipitation. However, due to the insulation layer in the positive electrode tank, the electrolyte temperature remains normal. The first small circulation loop can then be used to cool the electrolyte in the positive electrode pipeline, avoiding the risk of solid material precipitation. During this process, the electrolyte does not flow through the stack, reducing self-discharge losses.

[0079] In one exemplary embodiment, a first negative electrode small circulation branch valve is located on the first negative electrode electrolyte small circulation branch between the negative electrode inlet valve and the negative electrode return valve. When the first negative electrode small circulation branch valve is open, the negative electrode electrolyte can flow back through the first negative electrode electrolyte small circulation branch and no longer flow back to the negative electrode tank. A second negative electrode small circulation branch valve is located between the negative electrode inlet and the positive electrode outlet of the fuel cell stack, forming a second negative electrode small circulation branch. When the first negative electrode small circulation branch valve is open, the negative electrode electrolyte can flow directly from the negative electrode inlet to the negative electrode outlet of the fuel cell stack without entering the fuel cell stack. When both the first and second negative electrode small circulation branch valves are open, and the negative electrode inlet valve and negative electrode return valve of the negative electrode liquid tank are closed simultaneously, the negative electrode liquid pump is started. The negative electrode electrolyte flows out of the negative electrode liquid pump, flows through the second and first negative electrode small circulation branches, returns to the negative electrode heat exchanger, and then enters the inlet of the negative electrode liquid pump. Figure 7As shown by the thick black line on the right, the negative electrode electrolyte circuit forms the first small circulation loop at this point. At this time, the electrolyte in the negative electrode pipeline can be cooled or heated through the negative electrode electrolyte thermal management system. When the flow battery system has not been charged or discharged for a long time in winter, the electrolyte temperature in the negative electrode pipeline decreases, posing a risk of crystalline material precipitation. However, due to the insulation layer in the negative electrode tank, when the electrolyte temperature is normal, the electrolyte in the negative electrode pipeline can be heated through the first small circulation loop to avoid the risk of solid material precipitation. During this process, the electrolyte does not flow through the stack, reducing self-discharge losses.

[0080] When a flow battery system has not been charged or discharged for an extended period, and the tank insulation is good with normal electrolyte temperature, the electrolyte temperature may be higher in summer (higher ambient temperature) or lower in winter (lower ambient temperature). In such cases, there is a risk of solid precipitation in the positive or negative electrolyte of the piping system and the battery stack. In such situations, the following can be done: Figure 7 As shown in the example, the first small circulation loop of the positive electrode and the first small circulation loop of the negative electrode are opened. Through the positive and negative electrode thermal management systems, the temperatures of the positive and negative electrolytes in the pipelines are brought back to normal to avoid the risk of solid material precipitation. In one exemplary instance, after the electrolyte temperature in the pipelines is adjusted to the normal temperature range, the second small circulation branch valve of the positive electrode and the second small circulation branch valve of the negative electrode are closed, allowing both the positive and negative electrolytes to flow through the fuel cell stack. Figure 8 As shown by the thick black lines on the right and left, the positive and negative electrolyte circuits respectively constitute the second small circulation loop for the positive and negative electrodes. In this case, the stack temperature can be adjusted to normal, avoiding the risk of electrolyte solids precipitating out of the stack. In this process, by first activating the circulation and thermal management systems of the first and second small circulation loops of the positive and negative electrodes, and then activating the second and second small circulation loops, the time the electrolyte flows through the stack can be shortened to the greatest extent possible, reducing the energy loss from self-discharge. Figure 8 The diagram shows the positive electrode electrolyte and negative electrode electrolyte flowing through the heat exchanger, liquid pump, fuel cell stack, and the first small circulation branch, respectively, when the positive electrode inlet valve, positive electrode return valve, negative electrode inlet valve, and negative electrode return valve are closed, the positive electrode first small circulation branch valve and the negative electrode first small circulation branch valve are open, and the positive electrode second small circulation branch valve and the negative electrode second small circulation branch valve are closed.

[0081] In an exemplary instance, when the flow battery system has not been charged and discharged for a long time, the temperature of the electrolyte in the pipeline system and the tank gradually approaches the temperature of the environment. At this time, although the risk of solid material precipitation has not been reached, the temperature of the electrolyte in the system is low, for example, 5°C, and the performance of the battery is low when the system starts to charge and discharge. Directly performing constant power charging or discharging, it is easy to reach the cut-off condition of charging or discharging, and the system call efficiency is affected. If the electrolyte in the positive and negative electrolyte tanks is to be restored to a suitable temperature, for example, 30-35°C, a long time is needed, and a lot of auxiliary power is consumed to adjust the electrolyte temperature, reducing the system efficiency. At this time, the positive inlet valve, the positive return valve, the negative inlet valve and the negative return valve can be closed, the positive first small circulation branch valve and the second small circulation branch valve, the negative first small circulation branch valve and the second small circulation branch valve are opened, the positive first small circulation loop and the negative first small circulation loop are formed (as shown in Figure 7 ), the electrolyte is circulated in the pipeline system, and the positive and negative thermal management systems are started to adjust the temperature of the electrolyte in the pipeline to a higher temperature, for example, 35-38°C. Then, the positive and negative second small circulation branch valves are closed to form the positive second small circulation loop and the negative second small circulation loop (as shown in Figure 8 ), and the temperature of the stack is quickly adjusted to the normal working temperature, for example, 35°C. Then, the positive inlet valve, the positive return valve, the negative inlet valve and the negative return valve are opened, and the opening degree of the first positive small circulation branch valve and the first negative small circulation branch valve is adjusted, so that part of the electrolyte with a higher temperature (35°C) flows back to the positive tank and the negative tank, and another part of the electrolyte with a lower temperature (5°C) flows out of the tank. After mixing, the electrolyte flows through the positive heat exchanger and the negative heat exchanger, and the temperature of the electrolyte can be quickly adjusted to the normal working temperature (35°C) through the thermal management system. Through the control of the small circulation loop, the flow battery system can quickly start to charge and discharge, and since the temperature of the electrolyte is adjusted through the small circulation loop, the charging and discharging can be fully performed, and the influence of the environment temperature on the energy storage capacity and the working efficiency is small. When the temperature of the electrolyte in the positive tank and the negative tank reaches the normal working temperature, the first positive small circulation branch valve and the first negative small circulation branch valve are closed, and the electrolyte circulation is completely switched to the positive large circulation loop and the negative large circulation loop (as shown in Figure 6 ), and the system returns to the normal state.

[0082] When the flow battery system is not charged or discharged for a long time, although the positive and negative electrolyte tanks have insulation layers, the temperature of the electrolyte in the tanks gradually approaches the ambient temperature over time. If it is summer, the temperature of the positive electrolyte is too high, for example, more than 40°C, and there is a risk of V2O5 solid precipitation. If it is winter, the temperature of the negative electrolyte is too low, for example, less than -10°C, and there is a risk of VSO4 crystal precipitation. In the related art, the system in which heat exchangers are installed in the positive and negative electrolyte tanks (as shown in Figure 1 ) can start the positive and negative thermal management systems to adjust the temperature of the electrolyte in the tanks, but the positive and negative electrolyte pumps need to be started at the same time, otherwise the temperature distribution of the electrolyte in the tanks is uneven and the heat exchange efficiency is low, and the electrolyte flowing through the stack when the pumps are started will cause self-discharge loss. In the system in which the positive heat exchanger is installed and the negative heat exchanger is not installed (as shown in Figure 2 ), whether the temperature is too high or too low, the positive and negative electrolyte pumps need to be started to circulate the electrolyte, and the positive thermal management system needs to be started to adjust the temperature of the electrolyte in the positive tank; when the positive and negative electrolytes flow through the stack, the temperature adjustment of the negative electrolyte is realized through the heat transfer of the proton exchange membrane, and in this process, the stack will generate self-discharge. For the flow battery system in which heat exchangers are installed in the positive and negative pipelines, the temperature adjustment of the positive and negative electrolytes can be realized through the heat exchangers, but the electrolyte still needs to flow through the stack and cannot avoid the self-discharge of the stack.

[0083] In an example, in the flow battery system provided by the embodiments of the present application, when the temperature of the electrolyte in the positive tank is too high (for example, more than 40°C), the first positive small circulation branch valve can be closed and the second positive small circulation branch valve can be opened, as shown by the black thick line path on the right side of Figure 9 , to form a positive third small circulation loop, start the positive electrolyte pump, and start the positive thermal management system to cool the positive electrolyte in the positive tank. In this process, the negative electrolyte circulation loop can be controlled to be opened or not opened according to the situation. When the temperature of the electrolyte in the negative tank is too low (for example, less than -10°C), the first negative small circulation branch valve can be closed and the second negative small circulation branch valve can be opened, as shown by the black thick line path on the left side of Figure 9 , to form a negative third small circulation loop, start the negative electrolyte pump, and start the negative thermal management system to heat the negative electrolyte in the negative tank. In this process, the positive electrolyte circulation loop can be controlled to be opened or not opened according to the situation. In the whole process of adjusting the temperature of the positive and negative tanks, the electrolyte does not flow through the stack, and no additional energy loss caused by the self-discharge of the stack will be caused. Figure 9The diagram illustrates the positive electrode inlet valve, positive electrode return valve, negative electrode inlet valve, and negative electrode return valve being open, the positive electrode first small circulation branch valve and the negative electrode first small circulation branch valve being closed, and the positive electrode second small circulation branch valve and the negative electrode second small circulation branch valve being open. The diagram shows the positive electrode electrolyte and the negative electrode electrolyte flowing through the liquid tank, heat exchanger, liquid pump, and the second small circulation branch before returning to the liquid tank, forming the positive electrode third small circulation loop and the negative electrode third small circulation loop, respectively.

[0084] When the energy storage system is not used for an extended period, the electrolyte temperature in the positive and negative electrode tanks will gradually approach ambient temperature. Prolonged deviation from the normal temperature range may lead to the precipitation of solid substances. By activating the third small circulation loops in both the positive and negative electrodes, the electrolyte can be heated or cooled using the positive and negative heat exchangers, preventing abnormal electrolyte temperatures in the tanks. In these third small circulation loops, the electrolyte does not flow through the fuel cell stack, reducing auxiliary power consumption losses and self-discharge losses caused by electrolyte flowing through the stack. This circulation loop also plays a role in system electrolyte condition assessment and adjustment. Sufficient electrolyte reflux through the third small circulation loop ensures thorough mixing of the positive and negative electrolytes in both the positive and negative electrode tanks and pipelines. This allows for more accurate reflection of the system condition when electrolyte samples are taken from the positive and negative electrode tanks. Moreover, when the overall valence state of the electrolyte in the system rises, a reducing agent needs to be added to the positive electrode tank to lower the valence state of the positive electrode electrolyte. At this time, by starting the third small circulation loop of the positive electrode, the positive electrode electrolyte can flow fully in the small circulation loop to balance the valence state of the positive electrode electrolyte.

[0085] In one exemplary instance, a first temperature sensor (such as...) is also provided on the positive and negative electrode liquid tanks respectively. Figure 4 The positive electrode liquid tank temperature sensor T1) and the fourth temperature sensor (such as Figure 4 The negative electrode liquid tank temperature sensor T4). In an exemplary embodiment, a second temperature sensor (such as T4) is also installed on the positive and negative electrode feed lines of the fuel cell stack. Figure 4 The positive electrode liquid infeed temperature sensor T2) and the fifth temperature sensor (such as Figure 4 The negative electrode liquid inlet temperature sensor T5 in the reactor core). In an exemplary embodiment, a third temperature sensor (such as T5) is installed on the positive and negative electrode outlet pipes of the reactor core. Figure 4 The positive electrode liquid discharge temperature sensor T3) and the sixth temperature sensor (such as Figure 4 The negative electrode liquid discharge temperature sensor T6 in the middle.

[0086] Through the data of the temperature sensor, the BMS can also monitor the electrolyte temperature in real time, control the opening and closing of the valve and the liquid pump, and coordinate the operation of the thermal management system.

[0087] In an exemplary example, the heat exchange pipe material of the positive electrode heat exchanger is preferentially selected from titanium alloy or polytetrafluoroethylene pipe, and the negative electrode heat exchanger is preferentially selected from graphite or silicon carbide or polytetrafluoroethylene pipe.

[0088] Compared with the prior art, the liquid flow battery system architecture provided by the embodiment of the application increases the positive and negative electrode liquid tanks and the positive and negative electrode small loops of the stack, controls the opening and closing of the liquid tank liquid inlet valve and the liquid return valve and the small loop valve, realizes convenient control of the temperature of the positive and negative electrode electrolyte entering the stack when the electrolyte in the positive and negative electrode liquid tanks is in a relatively wide temperature range, avoids temperature abnormalities of the stack, and also avoids the need for the positive and negative electrode thermal management system to be configured with excessively high power, thereby causing additional waste. At the same time, when the liquid flow battery system cannot normally charge and discharge for a long time due to some unexpected reasons, when the temperature of the liquid path system, the stack or the positive and negative electrode liquid tanks exceeds the normal range, the small loop valve can be opened and closed, and the thermal management system can be used to regulate the temperature of the electrolyte, thereby avoiding the electrolyte exceeding the normal range, causing the positive and negative electrode electrolyte to precipitate solid substances, and thereby causing the risk of damage to the stack or the system.

[0089] In an exemplary example, as shown in Figure 4 The positive electrode electrolyte circuit includes a positive electrode liquid tank for storing positive electrode electrolyte, a positive electrode liquid inlet valve in communication with the outlet of the positive electrode liquid tank, a positive electrode liquid pump connected to the positive electrode liquid inlet valve, a positive electrode heat exchanger and a positive electrode thermal management system connected in sequence to the outlet of the positive electrode liquid pump, and a stack positive electrode liquid inlet connected to the outlet of the positive electrode heat exchanger; the positive electrode liquid outlet of the stack returns to the positive electrode liquid tank through a positive electrode liquid return valve. A positive electrode small circulation loop, i.e., a first positive electrode electrolyte small circulation branch, is provided between the positive electrode liquid inlet valve and the positive electrode liquid return valve, and a first positive electrode small circulation branch valve is provided on the first positive electrode electrolyte small circulation branch for opening, closing or adjusting the opening degree, so that the positive electrode electrolyte can form a small circulation flow on the positive electrode liquid tank side; another positive electrode small circulation branch, i.e., a second positive electrode electrolyte small circulation branch, is provided between the stack positive electrode liquid inlet and the positive electrode liquid outlet, and a stack second positive electrode small circulation branch valve is provided on the second positive electrode electrolyte small circulation branch for opening or closing, so that the positive electrode electrolyte can form a small circulation flow on the stack side.

[0090] A positive electrode liquid injection / liquid discharge valve is also provided on the inlet pipeline of the positive electrode liquid pump, which is in communication with the external pipeline, and is used to directly communicate with the positive electrode liquid tank when the system is filled with electrolyte or discharged, so that the electrolyte does not flow through the stack during the liquid filling or liquid discharging process, thereby avoiding damage to the stack.

[0091] In an exemplary instance, as shown in Figure 4 The negative electrolyte circuit is similar in structure to the positive electrolyte circuit, and includes a negative electrolyte tank for storing negative electrolyte, a negative electrolyte inlet valve in communication with the outlet of the negative electrolyte tank, a negative electrolyte pump connected to the negative electrolyte inlet valve, a negative heat exchanger and a negative thermal management system in sequence communication with the outlet of the negative electrolyte pump, and a stack negative electrolyte inlet connected to the outlet of the negative heat exchanger; the stack negative electrolyte outlet returns to the negative electrolyte tank through a negative electrolyte return valve. A negative small circulation branch, i.e., a first negative electrolyte small circulation branch, is provided between the negative electrolyte inlet valve and the negative electrolyte return valve, and a first negative small circulation branch valve is provided on the first negative electrolyte small circulation branch for opening, closing or adjusting the opening degree, so that the negative electrolyte can form a small circulation flow at the negative electrolyte tank side; another negative small circulation branch, i.e., a second negative electrolyte small circulation branch, is provided between the stack negative electrolyte inlet and the negative electrolyte outlet, and a stack second negative small circulation branch valve is provided on the second negative electrolyte small circulation branch for opening or closing, so that the negative electrolyte can form a small circulation flow at the stack side.

[0092] A negative electrolyte filling / drainage valve is further provided on the inlet pipeline of the negative electrolyte pump, which is in communication with an external pipeline for directly communicating with the negative electrolyte tank when the system is filled with electrolyte or drained, so that the electrolyte does not flow through the stack during the filling or draining process to avoid damage to the stack.

[0093] The liquid flow battery system architecture of the embodiments of the present application meets the requirements of various temperature conditions, quickly and economically controls the temperature of the electrolyte entering the stack, improves the reliability and economy, and reduces the risk of various failures of the liquid flow battery system.

[0094] The working principle of the liquid flow battery system architecture of the present application is as follows:

[0095] After the liquid flow battery system is installed at the user end, the ton barrel or tank truck pipeline for transporting electrolyte can be connected to the interface of the positive electrolyte filling / drainage valve and the negative electrolyte filling / drainage valve. At this time, when it is necessary to fill the positive electrolyte tank and / or the negative electrolyte tank, the ton barrel or tank truck is connected to the pipeline interface of the positive electrolyte filling / drainage valve, the positive tank return valve and / or the negative tank return valve are opened, the positive electrolyte inlet valve and / or the negative electrolyte inlet valve are closed, the first positive small circulation branch valve and / or the first negative small circulation branch valve are closed, the second positive small circulation branch valve and / or the second negative small circulation branch valve are opened, and the positive electrolyte filling / drainage valve and / or the negative electrolyte filling / drainage valve are opened and the positive and negative electrolyte pumps are started. In this way, as shown in Figure 10As shown by the thick black line path on the right side and the thick black line path on the left side, the electrolyte can be pumped from the ton barrel or tank truck into the positive and negative electrolyte tanks by the liquid pump without flowing through the stack, thereby avoiding affecting the stack. When the electrolyte in the liquid tank reaches the preset liquid level, the positive and negative liquid pumps and the liquid injection / liquid discharge valve are closed, and the flow battery system can enter the charging and discharging debugging state.

[0096] After the electrolyte is filled, the temperature of the electrolyte in the liquid tank may be too high or too low due to uncertain ambient temperature in the user site, exceeding the normal working range of the stack. For example, after the electrolyte is filled, the charging and discharging test cannot be performed for several days due to other reasons, and if it is in the cold winter, the temperature of the electrolyte in the stack, pipeline system and liquid tank may drop to below zero. At this time, the positive and negative liquid tank inlet valves and the liquid return valves are closed, the first positive small circulation branch valve and the first negative small circulation branch valve are opened, the second positive small circulation branch valve and the second negative small circulation branch valve are closed, and the positive and negative liquid pumps are started, so that the electrolyte flows in the stack small circulation loop. At the same time, the positive and negative thermal management systems are started, and heat is supplied to the positive and negative heat exchangers by the refrigerant, so that heat is transferred to the electrolyte. Due to the large specific heat capacity of the stack and the pipeline system itself, combined with the heating effect of the thermal management system, the temperature of the electrolyte can be quickly raised to the appropriate range. At this time, the stack can be controlled to start charging. In order to further avoid the electrolyte in the low-temperature liquid tank directly entering the stack to cause a sudden temperature drop, taking the positive side as an example, the opening degree of the positive liquid inlet valve and the first positive small circulation branch valve can also be adjusted, so that the electrolyte in the liquid tank and the electrolyte in the small circulation are mixed in proportion, and then heated by the positive heat exchanger before entering the stack. Part of the electrolyte flowing out of the stack flows back to the positive heat exchanger through the small circulation loop, and the other part flows back to the liquid tank. The electrolyte on the negative side is the same, which is not described here. In this way, even if the temperature of the electrolyte in the liquid tank is as low as zero, the system can be put into operation in a short time without relying on the high-power thermal management system to heat the entire liquid tank for a long time.

[0097] In the normal use process, the flow battery system may be out of use for a long time due to failure of other equipment, at which time the temperature of the positive and negative liquid tanks, the stack and the pipeline system will gradually approach the ambient temperature. If the ambient temperature is too high or too low, the positive and negative electrolyte may precipitate solid substances. At this time, according to the data collected by the positive tank temperature sensor T1 and the negative tank temperature sensor T4, the BMS can control the positive and negative liquid inlet valves and the liquid return valves to be opened, the first positive small circulation branch valve and the first negative small circulation branch valve to be closed, the second positive small circulation branch valve and the second negative small circulation branch valve to be opened, and the positive and negative liquid pumps and the thermal management system to be started, so that the electrolyte in the liquid tank flows through the heat exchanger for temperature adjustment, thereby avoiding the precipitation of solid substances caused by the over-limit temperature of the electrolyte.

[0098] When the liquid stack temperature sensors, i.e., the positive electrolyte inlet stack temperature sensor T2, the positive electrolyte outlet stack temperature sensor T3, the negative electrolyte inlet stack temperature sensor T5, and the negative electrolyte outlet stack temperature sensor T6, detect that the electrolyte temperature entering and exiting the stack is out of the alarm range, indicating that there is a risk of crystallization in the stack or the pipeline system, but the positive electrolyte tank temperature sensor T1 and the negative electrolyte tank temperature sensor T4 show that the electrolyte temperature in the tank is still in the normal range, then the electrolyte temperature in the tank does not need to be adjusted. At this time, the inlet valve and the return valve can be closed, the first positive electrolyte small circulation branch valve and the first negative electrolyte small circulation branch valve can be opened, the second positive electrolyte small circulation branch valve and the second negative electrolyte small circulation branch valve can be closed, and the positive and negative electrolyte pumps and the heat management module can be started, so that the electrolyte only circulates in the stack and the pipeline system, and the temperature is quickly adjusted. In this way, the risk of crystallization is avoided, and the charged electrolyte is not circulated in the stack for a long time, preventing self-discharge and energy loss.

[0099] The liquid flow battery system architecture provided by the embodiments of the present application introduces positive and negative electrolyte small circulation loops, and sets controllable valves at the electrolyte inlet and return positions of the tank and the inlet and outlet positions of the stack. By controlling the opening and closing of these valves, the flow path between the tank and the stack can be flexibly selected, and the electrolyte temperature can be accurately adjusted under different working conditions. Compared with the prior art, the present application can quickly control the electrolyte temperature entering the stack when the electrolyte temperature in the tank is in a wide range, avoiding temperature abnormalities in the stack without the need for a heat management system with excessively high power. Even in extreme cases such as system shutdown, excessively high or low ambient temperature, the electrolyte temperature can be adjusted by the small circulation loop and the heat management system, avoiding the precipitation of solid substances in the electrolyte, reducing the risk of damage to the stack and the pipeline, and avoiding energy loss caused by self-discharge of the stack.

[0100] Figure 5 The flowchart of the method for adjusting and controlling the electrolyte temperature in the embodiments of the present application is applied to the liquid flow battery system architecture provided by the embodiments of the present application, as shown in Figure 5 , which includes:

[0101] Step 500: obtaining the electrolyte temperature of the positive electrolyte tank, the electrolyte temperature of the negative electrolyte tank, the electrolyte temperature entering the stack, and the electrolyte temperature flowing out of the stack.

[0102] In an exemplary example, the electrolyte temperatures of the positive and negative electrolyte tanks are collected in real time by the positive electrolyte tank temperature sensor T1 and the negative electrolyte tank temperature sensor T4 in the liquid flow battery system architecture; the electrolyte temperatures entering and flowing out of the stack are collected by the positive electrolyte inlet stack temperature sensor T2 and the outlet stack temperature sensor T3, and the negative electrolyte inlet stack temperature sensor T5 and the outlet stack temperature sensor T6 in the liquid flow battery system architecture. In this way, the BMS can determine whether the electrolyte temperature is in the normal range according to the data of each temperature sensor.

[0103] Step 501: According to the obtained temperature information, the positive electrolyte circuit and / or the negative electrolyte circuit are controlled to control the temperature of the positive electrolyte and / or the negative electrolyte entering the stack.

[0104] In an exemplary example, step 501 can include:

[0105] When the temperature of the positive liquid tank or the positive side of the stack is higher than the preset upper limit or lower than the preset lower limit, the BMS controls to close the first positive small circulation branch valve, open the second positive small circulation branch valve, and start the positive liquid pump, so that the positive electrolyte circulates between the positive liquid tank, the positive heat exchanger, and the second positive small circulation branch, and exchanges heat with the environment through the positive thermal management system, thereby reducing or increasing the electrolyte temperature to restore the positive electrolyte temperature to the normal range, and prevent vanadium pentoxide (V2O5) from precipitating in the positive liquid tank.

[0106] When the temperature of the negative liquid tank or the negative side of the stack is higher than the preset upper limit or lower than the preset lower limit, the BMS controls to close the first negative small circulation branch valve, open the second negative small circulation branch valve, and start the negative liquid pump, so that the negative electrolyte circulates between the negative liquid tank, the negative heat exchanger, and the second negative small circulation branch, and exchanges heat with the environment through the negative thermal management system, thereby reducing or increasing the electrolyte temperature to restore the negative electrolyte temperature to the normal range, and prevent vanadium sulfate (VSO4) from crystallizing in the negative liquid tank.

[0107] When the temperature of the positive liquid tank is normal, but the positive inlet / outlet liquid temperature of the stack exceeds the alarm range (including higher than the preset upper limit or lower than the preset lower limit), the BMS controls to close the positive inlet valve and the positive return valve, open the first positive small circulation branch valve and the second positive small circulation branch valve, and start the positive liquid pump and the thermal management module, so that the positive electrolyte only circulates in the positive first small circulation loop, and when the positive electrolyte temperature is in the normal range, the second positive small circulation branch valve is closed, the positive electrolyte circulates in the positive second small circulation loop, and when the stack temperature is in the normal range, the electrolyte circulation is stopped.

[0108] When the temperature of the negative liquid tank is normal, but the negative inlet / outlet liquid temperature of the stack exceeds the alarm range (including higher than the preset upper limit or lower than the preset lower limit), the BMS controls to close the negative inlet valve and the negative return valve, open the first negative small circulation branch valve and the second negative small circulation branch valve, and start the negative liquid pump and the thermal management module, so that the negative electrolyte only circulates in the negative first small circulation loop, and when the negative electrolyte temperature is in the normal range, the second negative small circulation branch valve is closed, the negative electrolyte circulates in the negative second small circulation loop, and when the stack temperature is in the normal range, the electrolyte circulation is stopped.

[0109] When the positive liquid tank temperature deviates from the target range by a large margin, the BMS can also control the opening degree of the positive electrolyte inlet valve and the first positive small circulation branch valve, so that the electrolyte in the positive liquid tank and the electrolyte in the small circulation loop are mixed in a certain proportion and then enter the positive heat exchanger, and then are sent to the stack, thereby avoiding the direct impact of low-temperature or high-temperature electrolyte on the stack, and ensuring the smooth transition of the stack temperature.

[0110] When the negative liquid tank temperature deviates from the target range by a large margin, the BMS can also control the opening degree of the negative electrolyte inlet valve and the first negative small circulation branch valve, so that the electrolyte in the negative liquid tank and the electrolyte in the small circulation loop are mixed in a certain proportion and then enter the negative heat exchanger, and then are sent to the stack, thereby avoiding the direct impact of low-temperature or high-temperature electrolyte on the stack, and ensuring the smooth transition of the stack temperature.

[0111] The application also provides a computer readable storage medium, which stores computer executable instructions for executing the method for realizing electrolyte temperature regulation and control.

[0112] The application further provides a BMS, which comprises a memory and a processor, wherein the memory stores instructions executable by the processor, and the instructions are used for executing the steps of the method for realizing electrolyte temperature regulation and control.

[0113] The method for realizing electrolyte temperature regulation and control of the application embodiment meets the demand of various temperature conditions, quickly and economically controls the electrolyte temperature entering the stack, improves the reliability and economy, and reduces the risk of various failures of the flow battery system.

[0114] Although the embodiments disclosed in the application are as above, the content described is only the embodiments adopted for the purpose of facilitating the understanding of the application, and is not intended to limit the application. Any person skilled in the art of the application can make any modification and change in the implementation form and details without departing from the spirit and scope of the application disclosed, but the patent protection scope of the application shall be subject to the scope defined by the appended claims.

Claims

1. A flow battery system architecture, characterized in that, include: The fuel cell stack, and positive and negative electrolyte circuits respectively connected to the positive and negative sides of the fuel cell stack; wherein, The positive electrode electrolyte circuit includes: a positive electrode main circuit; the positive electrode main circuit is a closed circuit consisting of a positive electrode liquid tank, a positive electrode inlet valve, a positive electrode heat exchanger, a positive electrode liquid pump, a positive electrode inlet of the fuel cell stack, a positive electrode flow channel of the fuel cell stack, a positive electrode outlet of the fuel cell stack, and a positive electrode return valve connected in sequence. The positive electrode electrolyte circuit also includes: a first positive electrode electrolyte small circulation branch and a second positive electrode electrolyte small circulation branch; wherein, the two ends of the first positive electrode electrolyte small circulation branch are respectively connected to the main circuit section between the positive electrode inlet valve and the positive electrode return valve, and a first positive electrode small circulation branch valve is provided on the first positive electrode electrolyte small circulation branch for controlling the opening, closing and opening degree adjustment of the first positive electrode electrolyte small circulation branch; the two ends of the second positive electrode electrolyte small circulation branch are respectively connected between the positive electrode inlet and the positive electrode outlet of the fuel cell stack, and a second positive electrode small circulation branch valve is provided on the second positive electrode electrolyte small circulation branch for controlling the opening or closing of the second positive electrode electrolyte small circulation branch; The negative electrode electrolyte circuit includes: a negative electrode main circuit; the negative electrode main circuit is a closed circuit consisting of a negative electrode liquid tank, a negative electrode inlet valve, a negative electrode heat exchanger, a negative electrode liquid pump, the negative electrode inlet of the fuel cell stack, the negative electrode flow channel of the fuel cell stack, the negative electrode outlet of the fuel cell stack, and a negative electrode return valve connected in sequence. The negative electrode electrolyte circuit also includes: a first negative electrode electrolyte small circulation branch and a second negative electrode electrolyte small circulation branch; wherein, the two ends of the first negative electrode electrolyte small circulation branch are respectively connected to the main circuit section between the negative electrode inlet valve and the negative electrode return valve, and a first negative electrode small circulation branch valve is provided on the first negative electrode electrolyte small circulation branch for controlling the opening, closing and opening degree adjustment of the first negative electrode electrolyte small circulation branch; the two ends of the second negative electrode electrolyte small circulation branch are respectively connected between the negative electrode inlet and the negative electrode outlet of the fuel cell stack, and a second negative electrode small circulation branch valve is provided on the second negative electrode electrolyte small circulation branch for controlling the opening or closing of the second negative electrode electrolyte small circulation branch.

2. The flow battery system architecture according to claim 1 further includes: A positive electrode injection / drainage valve for adding or draining liquid is also provided before the positive electrode liquid pump; A negative electrode injection / drainage valve for adding or draining liquid is also provided before the negative electrode liquid pump.

3. The flow battery system architecture according to claim 2 further includes: A first temperature sensor is installed on the positive electrode liquid tank, and a fourth temperature sensor is installed on the negative electrode liquid tank; And / or, A second temperature sensor is installed on the positive electrode feed line of the fuel cell stack, and a fifth temperature sensor is installed on the negative electrode feed line of the fuel cell stack; and / or, A third temperature sensor is installed on the positive terminal outlet pipe of the fuel cell stack, and a sixth temperature sensor is installed on the negative terminal outlet pipe of the fuel cell stack.

4. The flow battery system architecture according to any one of claims 1-3, wherein, The heat exchange tube material of the positive electrode heat exchanger is titanium alloy or polytetrafluoroethylene (PTFE) tube; the material of the negative electrode heat exchanger is graphite, silicon carbide, or PTFE tube.

5. The flow battery system architecture according to claim 1, wherein, When the first positive electrode small circulation branch valve and the second positive electrode small circulation branch valve are completely closed, and the positive electrode inlet valve and the positive electrode return valve are open, the positive electrode electrolyte flows out from the positive electrode tank, flows through the positive electrode heat exchanger, the positive electrode pump, and the fuel cell stack, and flows back to the positive electrode tank through the positive electrode return valve. The positive electrode electrolyte circuit constitutes the positive electrode large circulation circuit. When the first negative electrode small circulation branch valve and the second negative electrode small circulation branch valve are completely closed, and the negative electrode inlet valve and the negative electrode return valve are open, the negative electrode electrolyte flows out from the negative electrode tank, flows through the negative electrode heat exchanger, the negative electrode pump, and the fuel cell stack, and flows back to the negative electrode tank through the negative electrode return valve. The negative electrode electrolyte circuit constitutes a negative electrode large circulation circuit.

6. The flow battery system architecture according to claim 1, wherein, When the first positive electrode small circulation branch valve and the second positive electrode small circulation branch valve are fully open, and the positive electrode inlet valve and the positive electrode return valve are closed, the positive electrode electrolyte flows out from the positive electrode liquid pump, flows through the second positive electrode small circulation branch, the first positive electrode small circulation branch, and the positive electrode heat exchanger, and flows back to the positive electrode liquid pump. The positive electrode electrolyte circuit constitutes the first positive electrode small circulation circuit. When the first negative electrode small circulation branch valve and the second negative electrode small circulation branch valve are fully open, and the negative electrode inlet valve and the negative electrode return valve are closed, the negative electrode electrolyte flows out from the negative electrode liquid pump, flows through the second negative electrode small circulation branch, the first negative electrode small circulation branch, and the negative electrode heat exchanger, and flows back to the negative electrode liquid pump. The negative electrode electrolyte circuit constitutes the first negative electrode small circulation circuit.

7. The flow battery system architecture according to claim 6, wherein, When the second positive electrode small circulation branch valve is closed, the positive electrode electrolyte flows out from the positive electrode liquid pump, flows through the fuel cell stack, the first positive electrode small circulation branch, the positive electrode heat exchanger, and flows back to the positive electrode liquid pump. The positive electrode electrolyte circuit constitutes the second positive electrode small circulation circuit. When the second negative electrode small circulation branch valve is closed, the negative electrode electrolyte flows out from the negative electrode liquid pump, flows through the fuel cell stack, the first negative electrode small circulation branch, and the negative electrode heat exchanger, and flows back to the negative electrode liquid pump and the fuel cell stack. The negative electrode electrolyte circuit constitutes the second negative electrode small circulation circuit.

8. The flow battery system architecture according to claim 7, wherein, When the positive electrode inlet valve and the positive electrode return valve are opened, and the opening degree of the first positive electrode small circulation branch valve is adjusted, a portion of the positive electrode electrolyte can be returned to the positive electrode tank. When the negative electrode inlet valve and the negative electrode return valve are opened, and the opening degree of the first negative electrode small circulation branch valve is adjusted, a portion of the negative electrode electrolyte can be returned to the negative electrode tank.

9. The flow battery system architecture according to claim 1, wherein, When the first positive electrode small circulation branch valve is completely closed, and the second positive electrode small circulation branch valve, the positive electrode inlet valve, and the positive electrode return valve are completely open, the positive electrode electrolyte flows out of the positive electrode tank, flows through the positive electrode heat exchanger, the positive electrode pump, and the second positive electrode small circulation branch, and then flows back to the positive electrode tank. The positive electrode electrolyte circuit constitutes the third positive electrode small circulation circuit. When the first negative electrode small circulation branch valve is completely closed, and the second negative electrode small circulation branch valve, the negative electrode inlet valve, and the negative electrode return valve are completely open, the negative electrode electrolyte flows out from the negative electrode tank, flows through the negative electrode heat exchanger, the negative electrode pump, and the second negative electrode small circulation branch, and then flows back to the negative electrode tank. The negative electrode electrolyte circuit constitutes the third negative electrode small circulation circuit.

10. The flow battery system architecture according to claim 2, wherein, When it is necessary to inject liquid into the positive electrode tank, connect the ton container or tank truck to the pipe interface of the positive electrode injection / drain valve, open the positive electrode return valve and the second positive electrode small circulation branch valve, close the positive electrode inlet valve and the first positive electrode small circulation branch valve, open the positive electrode injection / drain valve and start the positive electrode liquid pump, and the electrolyte is directly pumped into the positive electrode tank through the positive electrode liquid pump; When it is necessary to inject liquid into the negative electrode liquid tank, connect the ton container or liquid tanker to the pipeline interface of the negative electrode injection / drain valve, open the negative electrode liquid tank return valve and the second negative electrode small circulation branch valve, close the negative electrode inlet valve and the first negative electrode small circulation branch valve, open the negative electrode injection / drain valve and start the negative electrode liquid pump, and the electrolyte is directly pumped into the negative electrode liquid tank through the negative electrode liquid pump.

11. A method for controlling the temperature of an electrolyte, characterized in that, Based on the flow battery system architecture according to any one of claims 1-10; comprising: The electrolyte temperature of the positive electrode tank, the electrolyte temperature of the negative electrode tank, the electrolyte temperature entering the stack, and the electrolyte temperature exiting the stack are obtained. Based on the obtained temperature information, the positive electrolyte circuit and / or negative electrolyte circuit are controlled to control the temperature of the positive electrolyte and / or negative electrolyte entering the stack.

12. The method according to claim 11, wherein, The electrolyte temperature of the positive electrode tank and the electrolyte temperature of the negative electrode tank are collected in real time through the positive electrode tank temperature sensor T1 and the negative electrode tank temperature sensor T4 in the flow battery system architecture. The electrolyte temperature entering the stack and the electrolyte temperature flowing out of the stack are collected using the positive electrode inlet temperature sensor T2 and the outlet temperature sensor T3, as well as the negative electrode inlet temperature sensor T5 and the outlet temperature sensor T6 in the flow battery system architecture.

13. The method according to claim 11, wherein, When the temperature of the positive electrode liquid tank or the positive electrode side of the stack is higher than a preset upper limit or lower than a preset lower limit, the first positive electrode small circulation branch valve in the flow battery system architecture is closed, the second positive electrode small circulation branch valve in the flow battery system architecture is opened, and the positive electrode liquid pump is started, so that the positive electrode electrolyte circulates between the positive electrode liquid tank, the positive electrode heat exchanger and the second positive electrode small circulation branch, forming the third positive electrode small circulation loop, so that the temperature of the positive electrode electrolyte returns to the normal range; When the temperature of the negative electrode liquid tank or the negative electrode side of the stack is higher than a preset upper limit or lower than a preset lower limit, the first negative electrode small circulation branch valve in the flow battery system architecture is closed, the second negative electrode small circulation branch valve in the flow battery system architecture is opened, and the negative electrode liquid pump is started, so that the negative electrode electrolyte circulates between the negative electrode liquid tank, the negative electrode heat exchanger and the second negative electrode small circulation branch, forming the third negative electrode small circulation loop, so that the temperature of the negative electrode electrolyte returns to the normal range; When the temperature of the positive electrode liquid tank is normal, but the positive electrode inlet / outlet temperature of the stack is higher than a preset upper limit or lower than a preset lower limit, the positive electrode inlet valve and positive electrode return valve in the flow battery system architecture are closed, the first positive electrode small circulation branch valve and the second positive electrode small circulation branch valve are opened, and the positive electrode liquid pump and thermal management module are started, so that the positive electrode electrolyte circulates only in the first positive electrode small circulation loop; when the temperature of the positive electrode electrolyte is within the normal range, the second positive electrode small circulation branch valve is closed, so that the positive electrode electrolyte circulates in the second positive electrode small circulation loop, and the electrolyte circulation stops when the stack temperature is within the normal range; When the temperature of the negative electrode liquid tank is normal, but the temperature of the negative electrode inlet / outlet of the stack is higher than the preset upper limit or lower than the preset lower limit, the negative electrode inlet valve and negative electrode return valve in the flow battery system architecture are closed, the first negative electrode small circulation branch valve and the second negative electrode small circulation branch valve are opened, and the negative electrode liquid pump and thermal management module are started, so that the negative electrode electrolyte circulates only in the first negative electrode small circulation loop. When the temperature of the negative electrode electrolyte is within the normal range, the second negative electrode small circulation branch valve is closed, so that the negative electrode electrolyte circulates in the second negative electrode small circulation loop. When the stack temperature is within the normal range, the electrolyte circulation stops.

14. The method of claim 13, further comprising: When the temperature of the positive electrode liquid tank deviates significantly from the target range, the opening of the positive electrode inlet valve and the first positive electrode small circulation branch valve is controlled so that the electrolyte in the positive electrode liquid tank and the electrolyte in the small circulation loop are mixed in a certain proportion and then enter the positive electrode heat exchanger, and then sent to the fuel cell stack. When the temperature of the negative electrode liquid tank deviates significantly from the target range, the opening of the negative electrode inlet valve and the first negative electrode small circulation branch valve is controlled so that the electrolyte in the negative electrode liquid tank and the electrolyte in the small circulation loop are mixed in a certain proportion before entering the negative electrode heat exchanger and then sent to the fuel cell stack.

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