Redox flow battery system and redox flow battery system operating method

Abstract

The present invention provides a redox flow battery system including: a main cell that performs charge and discharge through supply of a positive electrolyte and a negative electrolyte; a plurality of monitor cells selected from the group consisting of a bipolar monitor cell, a positive monitor cell, and a negative monitor cell; and a controller that controls charge and discharge of the main cell. The controller issues an operation command to an alarm device when a specific condition is satisfied.

Description

Redox flow battery system and method for operating the redox flow battery system

[0001] The present disclosure relates to a redox flow battery system and an operating method of the redox flow battery system. This application claims priority to Japanese Patent Application No. 2022-178361 filed on November 7, 2022, and incorporates by reference all of the contents of said Japanese application.

[0002] The redox flow battery system disclosed in Patent Document 1 includes a main cell and a monitor cell. The main cell is supplied with a positive electrode electrolyte and a negative electrode electrolyte and is charged and discharged. The monitor cells include a first monitor cell supplied with the same positive electrode electrolyte as the main cell and a second monitor cell supplied with the same negative electrode electrolyte as the main cell. Unlike the main cell, the first monitor cell and the second monitor cell do not charge or discharge. The open-circuit voltage of the first monitor cell is measured to determine the ionic valence of the positive electrode electrolyte corresponding to the measured open-circuit voltage. The state of charge of the positive electrode electrolyte corresponding to the determined ionic valence of the positive electrode electrolyte is determined. The open-circuit voltage of the second monitor cell is measured to determine the ionic valence of the negative electrode electrolyte corresponding to the measured open-circuit voltage. The state of charge of the negative electrode electrolyte corresponding to the determined ionic valence of the negative electrode electrolyte is determined. The redox flow battery system disclosed in Patent Document 1 stops operation when the determined state of charge reaches a predetermined value that predicts overcharge.

[0003] JP 2009-16217 A JP 2020-187939 A

[0004] The redox flow battery system of the present disclosure includes: a main cell that is charged and discharged by supplying a positive electrode electrolyte and a negative electrode electrolyte; a plurality of monitor cells selected from the group consisting of a bipolar monitor cell, a positive electrode monitor cell, and a negative electrode monitor cell; and a controller that controls charging and discharging of the main cell, wherein the bipolar monitor cells are supplied with the positive electrode electrolyte and the negative electrode electrolyte that are common to the main cell, the positive electrode monitor cell is supplied with the positive electrode electrolyte that is common to the main cell without being supplied with the negative electrode electrolyte that is common to the main cell, and the negative electrode monitor cell is supplied with the negative electrode electrolyte that is common to the main cell without being supplied with the positive electrode electrolyte that is common to the main cell, the controller issues an operation command to an alarm device when the calculated value of the amount of change in the charge molar concentration of the active material of the positive electrode electrolyte deviates by a predetermined value or more from the actual measured value of the amount of change in the charge molar concentration of the active material of the positive electrode electrolyte, or when the calculated value of the amount of change in the charge molar concentration of the active material of the negative electrode electrolyte deviates by a predetermined value or more from the actual measured value of the amount of change in the charge molar concentration of the active material of the negative electrode electrolyte, the actual measured value of the amount of change in the charge molar concentration of the active material of the positive electrode electrolyte is obtained by the positive electrode monitor cell or by both electrode monitor cells and the negative electrode monitor cell, the calculated value of the amount of change in the charge molar concentration of the active material of the positive electrode electrolyte is obtained from the actual measured value of the amount of change in the charge molar concentration of the active material of the negative electrode electrolyte and a set value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte, and the actual measured value of the amount of change in the charge molar concentration of the active material of the negative electrode electrolyte is obtained by the negative electrode monitor cell or by both electrode monitor cells and the positive electrode monitor cell, The calculated value of the amount of change in charge molar concentration of the active material in the negative electrode electrolyte is found from the actually measured value of the amount of change in charge molar concentration of the active material in the positive electrode electrolyte and a set value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte.

[0005] Fig. 1 is a schematic diagram showing the configuration of a redox flow battery system of Embodiment 1. Fig. 2 is a diagram showing a flowchart explaining a control procedure by a controller provided in the redox flow battery system of Embodiment 1. Fig. 3 is a schematic diagram showing the configuration of a redox flow battery system of Embodiment 2. Fig. 4 is a schematic diagram showing the configuration of a redox flow battery system of Embodiment 3. Fig. 5 is a schematic diagram showing the configuration of another example of the redox flow battery system of Embodiment 3. Fig. 6 is a diagram showing a flowchart explaining a control procedure by a controller provided in the redox flow battery system of Embodiment 3.

[0006] [Problem to be Solved by the Present Disclosure] The redox flow battery system of Patent Document 1 cannot predict that overcharging will occur during continued operation before the predetermined value is reached.

[0007] An object of the present disclosure is to provide a redox flow battery system that can predict the occurrence of overcharging regardless of the state of charge.

[0008] [Advantages of the Present Disclosure] The redox flow battery system of the present disclosure can predict the occurrence of overcharge regardless of the state of charge.

[0009] <Description of Embodiments of the Present Disclosure> The present inventors considered the history of the state of charge when overcharging occurs during operation of a redox flow battery system. As a result, the present inventors made the following findings regarding the following specific parameters that are correlated with the state of charge: Regardless of the state of charge, a deviation of a predetermined value or more between the actual measured value or set value and the calculated value of the following specific parameters indicates a high likelihood of overcharging occurring in the future. The specific parameters are the charge molar concentration of the active material in the electrolyte, the liquid volume ratio of the electrolyte, or the active material concentration ratio of the electrolyte. The present invention has been made based on these findings. First, embodiments of the present disclosure will be listed and described.

[0010] (1) A redox flow battery system according to one aspect of the present disclosure includes: a main cell that is charged and discharged by supplying a positive electrode electrolyte and a negative electrode electrolyte; a plurality of monitor cells selected from the group consisting of a bipolar monitor cell, a positive electrode monitor cell, and a negative electrode monitor cell; and a controller that controls charging and discharging of the main cell, wherein the bipolar monitor cells are supplied with the positive electrode electrolyte and the negative electrode electrolyte that are common to the main cell; the positive electrode monitor cell is supplied with the positive electrode electrolyte that is common to the main cell without being supplied with the negative electrode electrolyte that is common to the main cell; and the negative electrode monitor cell is supplied with the negative electrode electrolyte that is common to the main cell without being supplied with the positive electrode electrolyte that is common to the main cell. the controller issues an operation command to an alarm device when the calculated value of the amount of change in the charge molar concentration of the active material of the positive electrode electrolyte deviates by a predetermined value or more from the actual measured value of the amount of change in the charge molar concentration of the active material of the positive electrode electrolyte, or when the calculated value of the amount of change in the charge molar concentration of the active material of the negative electrode electrolyte deviates by a predetermined value or more from the actual measured value of the amount of change in the charge molar concentration of the active material of the negative electrode electrolyte, the actual measured value of the amount of change in the charge molar concentration of the active material of the positive electrode electrolyte is obtained by the positive electrode monitor cell or by both electrode monitor cells and the negative electrode monitor cell, the calculated value of the amount of change in the charge molar concentration of the active material of the positive electrode electrolyte is obtained from the actual measured value of the amount of change in the charge molar concentration of the active material of the negative electrode electrolyte and a set value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte, and the actual measured value of the amount of change in the charge molar concentration of the active material of the negative electrode electrolyte is obtained by the negative electrode monitor cell or by both electrode monitor cells and the positive electrode monitor cell, The calculated value of the amount of change in charge molar concentration of the active material in the negative electrode electrolyte is found from the actually measured value of the amount of change in charge molar concentration of the active material in the positive electrode electrolyte and a set value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte.

[0011] (2) A redox flow battery system according to an aspect of the present disclosure includes: a main cell that is charged and discharged by supplying a positive electrode electrolyte and a negative electrode electrolyte; a plurality of monitor cells selected from the group consisting of a bipolar monitor cell, a positive electrode monitor cell, and a negative electrode monitor cell; and a controller that controls charging and discharging of the main cell, wherein the bipolar monitor cells are supplied with the positive electrode electrolyte and the negative electrode electrolyte that are common to the main cell; the positive electrode monitor cell is supplied with the positive electrode electrolyte that is common to the main cell without being supplied with the negative electrode electrolyte that is common to the main cell; and the negative electrode monitor cell is supplied with the negative electrode electrolyte that is common to the main cell without being supplied with the positive electrode electrolyte that is common to the main cell. the controller issues an operation command to an alarm device when a calculated value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte deviates by a predetermined value or more from a set value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte, or when a calculated value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte deviates by a predetermined value or more from a set value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte, the calculated value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte and the calculated value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte are obtained from an actual measurement value of a change in charge molar concentration of an active material in the positive electrode electrolyte and an actual measurement value of a change in charge molar concentration of an active material in the negative electrode electrolyte, the actual measurement value of a change in charge molar concentration of an active material in the positive electrode electrolyte is obtained by the positive electrode monitor cell, or by both the electrode monitor cell and the negative electrode monitor cell, The actual measured value of the change in charge molar concentration of the active material in the negative electrode electrolyte is determined by the negative electrode monitor cell, or by both the positive electrode monitor cell and the negative electrode monitor cell.

[0012] (3) A redox flow battery system according to an aspect of the present disclosure includes: a main cell that is charged and discharged by supplying a positive electrode electrolyte and a negative electrode electrolyte; a plurality of monitor cells selected from the group consisting of a bipolar monitor cell, a positive electrode monitor cell, and a negative electrode monitor cell; and a controller that controls charging and discharging of the main cell, wherein the bipolar monitor cells are supplied with the positive electrode electrolyte and the negative electrode electrolyte that are common to the main cell; the positive electrode monitor cell is supplied with the positive electrode electrolyte that is common to the main cell without being supplied with the negative electrode electrolyte that is common to the main cell; and the negative electrode monitor cell is supplied with the negative electrode electrolyte that is common to the main cell without being supplied with the positive electrode electrolyte that is common to the main cell. the controller issues an operation command to an alarm device when a calculated value of an active material concentration ratio of the positive electrode electrolyte to the negative electrode electrolyte deviates by a predetermined value or more from a set value of an active material concentration ratio of the positive electrode electrolyte to the negative electrode electrolyte, or when a calculated value of an active material concentration ratio of the negative electrode electrolyte to the positive electrode electrolyte deviates by a predetermined value or more from a set value of an active material concentration ratio of the negative electrode electrolyte to the positive electrode electrolyte, the calculated value of the active material concentration ratio of the positive electrode electrolyte to the negative electrode electrolyte is obtained by a potential of the positive electrode electrolyte, a potential of the negative electrode electrolyte, and a set value of a liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte, The potential of the positive electrode electrolyte is determined by the positive electrode monitor cell or by both the electrode monitor cells and the negative electrode monitor cell, and the potential of the negative electrode electrolyte is determined by the negative electrode monitor cell or by both the electrode monitor cells and the positive electrode monitor cell.

[0013] The redox flow battery systems (1), (2), and (3) can detect the above symptoms through the judgment of the controller. Therefore, the redox flow battery systems (1), (2), and (3) can predict the occurrence of overcharging regardless of the state of charge. The redox flow battery systems (1), (2), and (3) can issue an operation command to an alarm device, which then issues an alarm, thereby notifying the operator operating the redox flow battery system that the above symptoms have been observed. The operator can take measures to prevent malfunctions due to overcharging before overcharging actually occurs. Furthermore, the operator can maximize the charging or discharging time of the redox flow battery system. The operator can also stop charging or discharging. Stopping charging or discharging more reliably prevents overcharging from occurring.

[0014] (4) In the redox flow battery system of (1) or (2), the positive electrode monitor cell may determine an actual measurement of a change in charge molar concentration of an active material in the positive electrode electrolyte based on an absolute potential of the positive electrode electrolyte, and the negative electrode monitor cell may determine an actual measurement of a change in charge molar concentration of an active material in the negative electrode electrolyte based on an absolute potential of the negative electrode electrolyte.

[0015] The above-mentioned configuration (4) makes it easy to obtain the above-mentioned actual measured values.

[0016] (5) In the redox flow battery system of (3) or (4), the positive electrode monitor cell may measure a potential difference of the positive electrode electrolyte relative to a positive electrode reference electrode having a known potential, and the negative electrode monitor cell may measure a potential difference of the negative electrode electrolyte relative to a negative electrode reference electrode having a known potential.

[0017] The configuration of (5) above makes it easy to determine the calculated values ​​described above. The configurations of (4) and (5) above also make it easy to determine the measured values ​​described above. This is because the measured values ​​described above correspond to the potential differences described above, and the calculated values ​​described above can be determined using the measured values ​​described above.

[0018] (6) In the redox flow battery system of (3) or (4), the positive electrode monitor cell may measure a potential difference of the positive electrode electrolyte relative to a reference positive electrode electrolyte having a known change in charge molar concentration of the active material, and the negative electrode monitor cell may measure a potential difference of the negative electrode electrolyte relative to a reference negative electrode electrolyte having a known change in charge molar concentration of the active material.

[0019] The configuration of (6) above makes it easy to obtain the calculated values ​​described above. The configurations of (4) and (6) above also make it easy to obtain the measured values ​​described above.

[0020] (7) In the redox flow battery system according to any one of (1) to (6), the controller may stop charging or discharging the main cell after issuing an operation command to the alarm device.

[0021] In the configuration of (7) above, after the controller issues an operation command to the alarm device, charging or discharging can be automatically stopped without the operator having to take any action to stop charging or discharging, so the configuration of (7) above can automatically prevent overcharging.

[0022] (8) In the redox flow battery system according to any one of (1) to (7), the both electrode monitor cells may be provided in circulation paths for the positive electrode electrolyte and the negative electrode electrolyte, the positive electrode monitor cell may be provided in the circulation path for the positive electrode electrolyte, and the negative electrode monitor cell may be provided in the circulation path for the negative electrode electrolyte.

[0023] The configuration of (8) above makes it easy to obtain the above-mentioned measured values ​​or calculated values.

[0024] (9) A method for operating a redox flow battery system according to one aspect of the present disclosure, comprising the steps of: determining an actual measurement value of a change in charge molar concentration of an active material of the positive electrode electrolyte by a positive electrode monitor cell, or by both electrode monitor cells and the negative electrode monitor cell; determining an actual measurement value of a change in charge molar concentration of an active material of the negative electrode electrolyte by the negative electrode monitor cell, or by both electrode monitor cells and the positive electrode monitor cell; and determining a calculated value of a change in charge molar concentration of an active material of the positive electrode electrolyte from the actual measurement value of the change in charge molar concentration of an active material of the negative electrode electrolyte and a set value for a volume ratio of the positive electrode electrolyte to the negative electrode electrolyte, or determining a calculated value of a change in charge molar concentration of an active material of the negative electrode electrolyte from the actual measurement value of the change in charge molar concentration of an active material of the positive electrode electrolyte and a set value for a volume ratio of the negative electrode electrolyte to the positive electrode electrolyte; and issuing an operation command to an alarm device when a calculated value of the amount of change in the charging molar concentration of the active material in the positive electrode electrolyte deviates by a predetermined value or more from an actual measured value of the amount of change in the charging molar concentration of the active material in the negative electrode electrolyte, or when a calculated value of the amount of change in the charging molar concentration of the active material in the negative electrode electrolyte deviates by a predetermined value or more from an actual measured value of the amount of change in the charging molar concentration of the active material in the negative electrode electrolyte, wherein the positive electrode electrolyte and the negative electrode electrolyte common to the main cell are supplied to the both electrode monitor cells, the positive electrode monitor cell is supplied with the positive electrode electrolyte common to the main cell without being supplied with the negative electrode electrolyte common to the main cell, and the negative electrode monitor cell is supplied with the negative electrode electrolyte common to the main cell without being supplied with the positive electrode electrolyte common to the main cell.

[0025] (10) A method for operating a redox flow battery system according to one aspect of the present disclosure, comprising the steps of: determining an actual measurement value of a change in charge molar concentration of an active material of the positive electrode electrolyte by a positive electrode monitor cell, or by both electrode monitor cells and a negative electrode monitor cell; determining an actual measurement value of a change in charge molar concentration of an active material of the negative electrode electrolyte by the negative electrode monitor cell, or by both electrode monitor cells and the positive electrode monitor cell; and determining a liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte or a liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte, based on the actual measurement value of the change in charge molar concentration of the active material of the positive electrode electrolyte and the actual measurement value of the change in charge molar concentration of the active material of the negative electrode electrolyte. and issuing an operation command to an alarm device when a calculated value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte deviates by a predetermined value or more from a set value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte, or when a calculated value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte deviates by a predetermined value or more from a set value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte, wherein the positive electrode electrolyte and the negative electrode electrolyte common to the main cell are supplied to the bipolar monitor cell, the positive electrode electrolyte common to the main cell is supplied to the positive electrode monitor cell without being supplied with the negative electrode electrolyte common to the main cell, and the negative electrode electrolyte common to the main cell is supplied to the negative electrode monitor cell without being supplied with the positive electrode electrolyte common to the main cell.

[0026] (11) A method for operating a redox flow battery system according to one aspect of the present disclosure, comprising the steps of: supplying a positive electrode electrolyte and a negative electrode electrolyte to a main cell to perform charging and discharging; determining a potential of the positive electrode electrolyte by a positive electrode monitor cell, or by both electrode monitor cells and a negative electrode monitor cell; determining a potential of the negative electrode electrolyte by the negative electrode monitor cell, or by both electrode monitor cells and the positive electrode monitor cell; and calculating a value of an active material concentration ratio of the positive electrode electrolyte to the negative electrode electrolyte based on the potentials of the positive electrode electrolyte, the potentials of the negative electrode electrolyte, and a set value of a volume ratio of the positive electrode electrolyte to the negative electrode electrolyte, or calculating a value of an active material concentration ratio of the negative electrode electrolyte to the positive electrode electrolyte based on the potentials of the positive electrode electrolyte, the potentials of the negative electrode electrolyte, and a set value of a volume ratio of the negative electrode electrolyte to the positive electrode electrolyte; and issuing an operation command to an alarm device when a calculated value of the ratio of active material concentrations of the positive electrode electrolyte to the negative electrode electrolyte deviates by a predetermined value or more from a set value of the ratio of active material concentrations of the positive electrode electrolyte to the negative electrode electrolyte, or when a calculated value of the ratio of active material concentrations of the negative electrode electrolyte to the positive electrode electrolyte deviates by a predetermined value or more from a set value of the ratio of active material concentrations of the negative electrode electrolyte to the positive electrode electrolyte, wherein the positive electrode monitor cell is supplied with the positive electrode electrolyte and the negative electrode electrolyte common to the main cell, the positive electrode monitor cell is supplied with the positive electrode electrolyte common to the main cell without being supplied with the negative electrode electrolyte common to the main cell, and the negative electrode monitor cell is supplied with the negative electrode electrolyte common to the main cell without being supplied with the positive electrode electrolyte common to the main cell.

[0027] The redox flow battery system operation methods (9), (10), and (11) can detect the above symptoms. Therefore, the redox flow battery system operation methods (9), (10), and (11) can predict the occurrence of overcharging regardless of the state of charge. The redox flow battery system operation methods (9), (10), and (11) issue an operation command to an alarm device, causing the alarm device to issue an alarm, thereby notifying the operator operating the redox flow battery system that the above symptoms have been observed. The operator can take measures to prevent malfunctions due to overcharging before overcharging actually occurs. Furthermore, the operator can maximize the charge time or discharge time of the redox flow battery system. The operator can also stop charging or discharging. Stopping charging or discharging more reliably prevents overcharging.

[0028] (12) The method for operating a redox flow battery system according to any one of (9) to (11) above may further include a step of stopping charging or discharging of the main cell after the step of issuing an operation command to the alarm device.

[0029] The configuration of (12) above can automatically stop charging or discharging after issuing an operation command to the alarm device without the operator having to perform any work to stop charging or discharging, and therefore can automatically prevent overcharging.

[0030] Details of the embodiment of the present disclosure The redox flow battery system and the method of operating the redox flow battery system of the present disclosure will be described in detail below. The same reference numerals in the drawings indicate the same components.

[0031] <<Embodiment 1>> [Redox Flow Battery System] A redox flow battery system 1 of embodiment 1 will be described with reference to Fig. 1. The redox flow battery system 1 includes a main cell 10, a plurality of monitor cells, and a controller 3. The main cell 10 performs charging and discharging. A positive electrode electrolyte and a negative electrode electrolyte are supplied to the main cell 10. The controller 3 controls the charging and discharging of the main cell 10. One of the features of the redox flow battery system 1 is that the controller 3 issues an operation command to an alarm device 100 when specific conditions are met.

[0032] [Overview] The redox flow battery system 1 charges and stores power generated by a power generation unit 310, and discharges and supplies the stored power to a load 330. The redox flow battery system 1 is typically connected to an AC / DC converter 300. The AC / DC converter 300 is connected to a substation 320. The substation 320 is connected to the power generation unit 310 and a load 330. An example of the power generation unit 310 is a solar power generation system, a wind power generation system, or other general power plants. An example of the load 330 is a power consumer. A solid arrow extending from the substation 320 toward the AC / DC converter 300 indicates charging. A dashed arrow extending from the AC / DC converter 300 toward the substation 320 indicates discharging. The redox flow battery system 1 uses a positive electrode electrolyte and a negative electrode electrolyte. The positive electrode electrolyte and the negative electrode electrolyte contain, as active materials, ions whose valence changes through oxidation-reduction. The redox flow battery system 1 is charged or discharged by utilizing the difference between the redox potential of the ions contained in the positive electrode electrolyte and the redox potential of the ions contained in the negative electrode electrolyte. Examples of applications of the redox flow battery system 1 include load leveling, momentary sag compensation, emergency power supply, and smoothing of the output of natural energy. Natural energy is energy obtained by solar power generation or wind power generation.

[0033] [Main Cell] The main cell 10 performs charging and discharging. The main cell 10 is connected to an AC / DC converter 300. Although not shown, the main cell 10 is separated into a positive electrode cell and a negative electrode cell by a diaphragm. The diaphragm is an ion exchange membrane that is impermeable to electrons but permeable to, for example, hydrogen ions. A positive electrode is built into the positive electrode cell. A positive electrode circulation mechanism 4P, which will be described later, circulates a positive electrode electrolyte through the positive electrode cell. A negative electrode is built into the negative electrode cell. A negative electrode is built into the negative electrode cell. A negative electrode circulation mechanism 4N, which will be described later, circulates a negative electrode electrolyte through the negative electrode cell. The main cell 10 can have a known configuration. The main cell 10 is usually formed inside a structure called a cell stack.

[0034] The cell stack includes a substack, two end plates, and a clamping mechanism. The substack includes a laminate and two supply / discharge plates. The laminate is composed of multiple cell frames, positive electrodes, diaphragms, and negative electrodes stacked in this order. One main cell 10 is formed between adjacent cell frames. The supply / discharge plates are arranged at both ends of the laminate. The first supply pipe 5a and first discharge pipe 5b of the positive electrode circulation mechanism 4P and the second supply pipe 6a and second discharge pipe 6b of the negative electrode circulation mechanism 4N are connected to the supply / discharge plates. The number of substacks may be one or more. The two end plates sandwich the multiple substacks from the outside of the substacks on both ends. The clamping mechanism clamps both end plates. The cell stack may have a known configuration.

[0035] [Positive Electrode Circulation Mechanism / Negative Electrode Circulation Mechanism] The positive electrode circulation mechanism 4P includes a positive electrode electrolyte tank 41, a first supply pipe 5a, a first discharge pipe 5b, and a first pump 5g. The positive electrode electrolyte tank 41 stores positive electrode electrolyte. The positive electrode electrolyte flows through the first supply pipe 5a and the first discharge pipe 5b. The first supply pipe 5a connects the positive electrode electrolyte tank 41 to the positive electrode cell. The first discharge pipe 5b connects the positive electrode cell to the positive electrode electrolyte tank 41. The first pump 5g pressure-feeds the positive electrode electrolyte in the positive electrode electrolyte tank 41. The first pump 5g is provided midway through the first supply pipe 5a.

[0036] The anode circulation mechanism 4N includes an anode electrolyte tank 42, a second supply pipe 6a, a second discharge pipe 6b, and a second pump 6g. The anode electrolyte tank 42 stores the anode electrolyte. The anode electrolyte flows through the second supply pipe 6a and the second discharge pipe 6b. The second supply pipe 6a connects the anode electrolyte tank 42 and the anode cell. The second discharge pipe 6b connects the anode cell and the anode electrolyte tank 42. The second pump 6g pressure-feeds the anode electrolyte in the anode electrolyte tank 42. The second pump 6g is provided midway through the second supply pipe 6a.

[0037] [Electrolyte] The positive electrode active material contained in the positive electrode electrolyte, the solvent for the positive electrode electrolyte, the negative electrode active material contained in the negative electrode electrolyte, and the solvent for the negative electrode electrolyte are not particularly limited. The positive electrode active material is, for example, one or more selected from the group consisting of manganese ions, vanadium ions, iron ions, polyacids, quinone derivatives, and amines. The negative electrode active material is, for example, one or more selected from the group consisting of titanium ions, vanadium ions, chromium ions, polyacids, quinone derivatives, and amines. Specific examples include a case where both the positive electrode electrolyte and the negative electrode electrolyte contain vanadium ions. The solvent for the positive electrode electrolyte and the negative electrode electrolyte is, for example, an aqueous solution containing one or more acids or acid salts selected from the group consisting of sulfuric acid, phosphoric acid, nitric acid, and hydrochloric acid.

[0038] [Monitor Cell] The multiple monitor cells are selected from the group consisting of a bipolar monitor cell 2B, a positive electrode monitor cell 2P, and a negative electrode monitor cell 2N. Unlike the main cell 10, each monitor cell is not connected to the AC / DC converter 300 and does not charge or discharge. The redox flow battery system 1 only needs to have at least two of the three monitor cells, i.e., the bipolar monitor cell 2B, the positive electrode monitor cell 2P, and the negative electrode monitor cell 2N. FIG. 1 shows an example in which the redox flow battery system 1 includes all of the bipolar monitor cell 2B, the positive electrode monitor cell 2P, and the negative electrode monitor cell 2N. Although not shown, unlike FIG. 1 , for example, the redox flow battery system 1 may not include the positive electrode monitor cell 2P, but may include only the bipolar monitor cell 2B and the negative electrode monitor cell 2N.

[0039] (Bipolar Monitor Cell) The bipolar monitor cell 2B is supplied with a positive electrode electrolyte common to the positive electrode electrolyte supplied to the main cell 10, and a negative electrode electrolyte common to the negative electrode electrolyte supplied to the main cell 10. The configuration of the bipolar monitor cell 2B is the same as that of the main cell 10. The bipolar monitor cell 2B of this embodiment is provided independently of the main cell 10. Unlike this embodiment, the main cell 10 and the bipolar monitor cell 2B may be provided integrally in the cell stack. In this case, the bipolar monitor cell 2B is disposed at the end of the stack.

[0040] The bipolar monitor cell 2B of this embodiment is provided midway through the circulation paths of the positive electrode electrolyte and the negative electrode electrolyte. In this embodiment, the positive electrode electrolyte and the negative electrode electrolyte are supplied to and discharged from the bipolar monitor cell 2B via a third supply pipe 5c, a third discharge pipe 5d, a fourth supply pipe 6c, and a fourth discharge pipe 6d. The third supply pipe 5c connects the first supply pipe 5a to the positive electrode cell of the bipolar monitor cell 2B. The third discharge pipe 5d connects the positive electrode cell of the bipolar monitor cell 2B to the first discharge pipe 5b. The fourth supply pipe 6c connects the second supply pipe 6a to the negative electrode cell of the bipolar monitor cell 2B. The fourth discharge pipe 6d connects the negative electrode cell of the bipolar monitor cell 2B to the second discharge pipe 6b.

[0041] A first potential meter 7a is connected to both electrode monitor cells 2B. The first potential meter 7a measures the potential difference between the potential of the positive electrode electrolyte flowing in the positive electrode cell and the potential of the negative electrode electrolyte flowing in the negative electrode cell in both electrode monitor cells 2B. The measured potential difference corresponds to the open-circuit voltage VR of the redox flow battery system 1. An example of the first potential meter 7a is a voltmeter. The measurement results by the first potential meter 7a are transmitted to the controller 3. The measurement results are transmitted by wireless communication or wired communication. The first potential meter 7a is equipped with a wireless communication device, or is connected to a signal line that is connected to the controller 3.

[0042] (Positive Electrode Monitor Cell) The positive electrode monitor cell 2P is supplied with only the positive electrode electrolyte that is common to the positive electrode electrolyte supplied to the main cell 10. In other words, the positive electrode monitor cell 2P is not supplied with the negative electrode electrolyte that is common to the negative electrode electrolyte supplied to the main cell 10. The configuration of the positive electrode monitor cell 2P is the same as that of the main cell 10. The positive electrode monitor cell 2P of this embodiment is provided independently of the main cell 10. The positive electrode monitor cell 2P of this embodiment is also provided independently of the bipolar electrode monitor cell 2B.

[0043] The positive electrode monitor cell 2P in this embodiment is provided midway through the circulation path of the positive electrode electrolyte. The supply of the positive electrode electrolyte to and discharge of the positive electrode monitor cell 2P are performed via a fifth supply pipe 5e and a fifth discharge pipe 5f. The fifth supply pipe 5e connects the first supply pipe 5a to the positive electrode monitor cell 2P. The fifth supply pipe 5e is connected downstream of the connection point of the first supply pipe 5a between the first supply pipe 5a and the third supply pipe 5c. "Downstream of the connection point of the first supply pipe 5a and the third supply pipe 5c" refers to a position closer to the main cell 10 than the connection point of the first supply pipe 5a and the third supply pipe 5c. The fifth discharge pipe 5f connects the positive electrode monitor cell 2P to the first discharge pipe 5b. The fifth discharge pipe 5f is connected upstream of the connection point of the first discharge pipe 5b between the first discharge pipe 5b and the third discharge pipe 5d. "Upstream of the connection point between the first discharge pipe 5b and the third discharge pipe 5d" refers to a position closer to the main cell 10 than the connection point between the first discharge pipe 5b and the third discharge pipe 5d.

[0044] A positive electrode reference electrode 7P with a known potential is connected to the positive electrode monitor cell 2P. An example of the positive electrode reference electrode 7P is a silver-silver chloride electrode or a mercury-mercurous sulfate electrode. A second potential meter 7b is connected between the positive electrode monitor cell 2P and the positive electrode reference electrode 7P. The second potential meter 7b measures the potential difference between the potential of the positive electrode electrolyte flowing through the positive electrode monitor cell 2P and the potential of the positive electrode reference electrode 7P. The measured potential difference is used as the absolute potential VP of the positive electrode electrolyte itself supplied to the positive electrode monitor cell 2P. An example of the second potential meter 7b is a voltmeter. The measurement results by the second potential meter 7b are transmitted to the controller 3. The measurement results are transmitted via wireless communication or wired communication. The second potential meter 7b is equipped with a wireless communication device or is connected to a signal line connected to the controller 3.

[0045] (Negative Electrode Monitor Cell) The negative electrode monitor cell 2N is supplied with only the negative electrode electrolyte that is common to the negative electrode electrolyte supplied to the main cell 10. In other words, the negative electrode monitor cell 2N is not supplied with the positive electrode electrolyte that is common to the positive electrode electrolyte supplied to the main cell 10. The configuration of the negative electrode monitor cell 2N is the same as that of the main cell 10. The negative electrode monitor cell 2N of this embodiment is provided independently of the main cell 10. The negative electrode monitor cell 2N of this embodiment is also provided independently of the bipolar electrode monitor cell 2B.

[0046] The anode monitor cell 2N of this embodiment is provided midway through the circulation path of the anode electrolyte. The anode electrolyte is supplied to and discharged from the anode monitor cell 2N via a sixth supply pipe 6e and a sixth discharge pipe 6f. The sixth supply pipe 6e connects the second supply pipe 6a to the anode monitor cell 2N. The sixth supply pipe 6e is connected to the second supply pipe 6a downstream of the connection point between the second supply pipe 6a and the fourth supply pipe 6c. "Downstream of the connection point between the second supply pipe 6a and the fourth supply pipe 6c" refers to a position closer to the main cell 10 than the connection point between the second supply pipe 6a and the fourth supply pipe 6c. The sixth discharge pipe 6f connects the anode monitor cell 2N to the second discharge pipe 6b. The sixth discharge pipe 6f is connected to the second discharge pipe 6b upstream of the connection point between the second discharge pipe 6b and the fourth discharge pipe 6d. "Upstream of the connection point between the second discharge pipe 6b and the fourth discharge pipe 6d" refers to a position closer to the main cell 10 than the connection point between the second discharge pipe 6b and the fourth discharge pipe 6d.

[0047] A negative electrode reference electrode 7N with a known potential is connected to the negative electrode monitor cell 2N. An example of the negative electrode reference electrode 7N is a silver-silver chloride electrode or a mercury-mercurous sulfate electrode. A third potential meter 7c is connected between the negative electrode monitor cell 2N and the negative electrode reference electrode 7N. The third potential meter 7c measures the potential difference between the potential of the negative electrode electrolyte flowing through the negative electrode monitor cell 2N and the potential of the negative electrode reference electrode 7N. The measured potential difference is used as the absolute potential VN of the negative electrode electrolyte itself supplied to the negative electrode monitor cell 2N. An example of the third potential meter 7c is a voltmeter. The measurement results by the third potential meter 7c are transmitted to the controller 3. The measurement results are transmitted via wireless communication or wired communication. The third potential meter 7c is equipped with a wireless communication device or is connected to a signal line connected to the controller 3.

[0048] During charging or discharging operation of the main cell 10, a pump controller 34 (described later) drives the first pump 5g and the second pump 6g. Driving the first pump 5g causes the positive electrode electrolyte in the positive electrode electrolyte tank 41 to flow to the first supply pipe 5a. A portion of the positive electrode electrolyte flowing through the first supply pipe 5a flows, in this order, through the positive electrode cell of the main cell 10, the first discharge pipe 5b, and the positive electrode electrolyte tank 41. Another portion of the positive electrode electrolyte flowing through the first supply pipe 5a flows, in this order, through the third supply pipe 5c, the positive electrode cell of the bipolar monitor cell 2B, the third discharge pipe 5d, the first discharge pipe 5b, and the positive electrode electrolyte tank 41. Yet another portion of the positive electrode electrolyte flowing through the first supply pipe 5a flows, in this order, through the fifth supply pipe 5e, the positive electrode monitor cell 2P, the fifth discharge pipe 5f, the first discharge pipe 5b, and the positive electrode electrolyte tank 41. When the second pump 6g is driven, the anode electrolyte in the anode electrolyte tank 42 flows into the second supply pipe 6a. A portion of the anode electrolyte flowing through the second supply pipe 6a flows, in this order, through the anode cell of the main cell 10, the second discharge pipe 6b, and the anode electrolyte tank 42. Another portion of the anode electrolyte flowing through the second supply pipe 6a flows, in this order, through the fourth supply pipe 6c, the anode cell of the bipolar monitor cell 2B, the fourth discharge pipe 6d, the second discharge pipe 6b, and the anode electrolyte tank 42. Another portion of the anode electrolyte flowing through the second supply pipe 6a flows, in this order, through the sixth supply pipe 6e, the anode monitor cell 2N, the sixth discharge pipe 6f, the second discharge pipe 6b, and the anode electrolyte tank 42. During standby, when neither charging nor discharging is performed, the first pump 5g and the second pump 6g are stopped. That is, the cathode electrolyte and the anode electrolyte are not circulated.

[0049] [Controller] The controller 3 controls each part necessary for the operation of the redox flow battery system 1. The controller 3 controls the charging and discharging of the main cell 10. Each process performed by the controller 3 is realized by a processing circuitry including one or more processors.

[0050] The processing circuit may be configured with an integrated circuit or the like that combines one or more memories, various analog circuits, and various digital circuits in addition to the one or more processors, and may also include an input / output I / F (Interface). The one or more memories store programs (instructions) that cause the one or more processors to execute each of the processes. The one or more memories are typically ROM (Read-Only Memory) or RAM (Random Access Memory).

[0051] The one or more processors may execute the processes according to the programs read from the one or more memories, or may execute the processes according to logic circuits pre-designed to execute the processes. The processors may be various processors suitable for computer control, such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or an ASIC (Application Specific Integrated Circuit). Note that the physically separated processors may cooperate with each other to execute the processes. For example, the processors mounted on each of a plurality of physically separated computers may cooperate with each other via a network such as a LAN (Local Area Network), a WAN (Wide Area Network), or the Internet to execute the above processes.

[0052] The program may be installed into the memory from an external server device or the like via the network, or may be distributed in a state stored on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a semiconductor memory, and then installed into the memory from the recording medium.

[0053] The controller 3 of this embodiment has an arithmetic device 31, a storage device 32, a determiner 33, a pump controller 34, and an alarm controller 36. The program includes program codes relating to a procedure in which the arithmetic device 31 performs a specific calculation, a process in which the determiner 33 determines whether or not a specific condition is satisfied based on the calculation result, a process in which the alarm controller 36 issues an operation command to the alarm device 100 based on the determination, and a process in which the pump controller 34 drives or stops the first pump 5g and the second pump 6g based on the operation command being issued to the alarm device 100.

[0054] The determiner 33 determines whether a specific condition is satisfied. The specific condition is any one of the following first to fourth conditions. That is, the determiner 33 determines whether any one of the first to fourth conditions is satisfied.

[0055] The first condition is that a calculated value A2 of the change in the charge molar concentration of the active material in the positive electrode electrolyte deviates by a predetermined value or more from a measured value A1 of the change in the charge molar concentration of the active material in the positive electrode electrolyte. The second condition is that a calculated value A4 of the change in the charge molar concentration of the active material in the negative electrode electrolyte deviates by a predetermined value or more from a measured value A3 of the change in the charge molar concentration of the active material in the negative electrode electrolyte. The third condition is that a calculated value A6 of the volume ratio of the positive electrode electrolyte to the negative electrode electrolyte deviates by a predetermined value or more from a set value A5 of the volume ratio of the positive electrode electrolyte to the negative electrode electrolyte. The fourth condition is that a calculated value A8 of the volume ratio of the negative electrode electrolyte to the positive electrode electrolyte deviates by a predetermined value or more from a set value A7 of the volume ratio of the negative electrode electrolyte to the positive electrode electrolyte.

[0056] Satisfying any one of the first to fourth conditions regardless of the state of charge is an indication that there is a high possibility of overcharging occurring in the future if the redox flow battery system 1 continues to operate. "Irrespective of the state of charge" does not only mean that the state of charge is high, such as 80%, but also that it is low, such as 70% or less, 60% or less, or 50% or less. The redox flow battery system 1 can detect the above indication by determining, by the controller 3, that any one of the first to fourth conditions is satisfied. Therefore, the redox flow battery system 1 can predict that overcharging will occur regardless of the state of charge. The redox flow battery system 1 that can predict the occurrence of overcharging can prevent overcharging from occurring.

[0057] The memory device 32 has a first memory device, a second memory device, a third memory device, and a fourth memory device. The first memory device stores a charge molar concentration of the active material of the positive electrode electrolyte corresponding to the potential VP of the positive electrode electrolyte itself. The charge molar concentration of the active material of the positive electrode electrolyte corresponding to the potential VP of the positive electrode electrolyte itself is a predetermined value. The second memory device stores a charge molar concentration of the active material of the negative electrode electrolyte corresponding to the potential VN of the negative electrode electrolyte itself. The charge molar concentration of the active material of the negative electrode electrolyte corresponding to the potential VN of the negative electrode electrolyte itself is a predetermined value. The third memory device stores a set value A5 of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte. The set value A5 is a predetermined value. The fourth memory device stores a set value A7 of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte. The set value A7 is a predetermined value.

[0058] The arithmetic unit 31 includes a first arithmetic unit, a second arithmetic unit, a third arithmetic unit, a fourth arithmetic unit, a fifth arithmetic unit, and a sixth arithmetic unit.

[0059] The first calculation device determines a measured value A1 of the amount of change in the charge molar concentration of the active material in the positive electrode electrolyte. The measured value A1 is the difference between the measured value CP1 of the charge molar concentration of the active material in the positive electrode electrolyte at a first time point and the measured value CP2 of the charge molar concentration of the active material in the positive electrode electrolyte at a second time point, i.e., "CP2 - CP1."

[0060] The measured value CPn of the charge molar concentration of the active material in the positive electrode electrolyte at a certain time point is the charge molar concentration of the active material in the positive electrode electrolyte corresponding to the potential VP of the positive electrode electrolyte itself at a certain time point. The charge molar concentration of the active material in the positive electrode electrolyte corresponding to the potential VP of the positive electrode electrolyte itself is stored in the first storage device. When the positive electrode monitor cell 2P is provided, the potential VP of the positive electrode electrolyte itself is determined by the positive electrode monitor cell 2P. When the positive electrode monitor cell 2P is not provided, the potential VP of the positive electrode electrolyte itself is determined by the sum of the open-circuit voltage VR of the redox flow battery system 1 determined by the bipolar electrode monitor cell 2B and the potential VN of the negative electrode electrolyte itself determined by the negative electrode monitor cell 2N, i.e., "VR + VN."

[0061] The second calculation device calculates a calculated value A2 of the amount of change in the charge molar concentration of the active material in the positive electrode electrolyte. The calculated value A2 is the product of the measured value A3 of the amount of change in the charge molar concentration of the active material in the negative electrode electrolyte and a set value A5 of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte, i.e., "A3 x A5." The set value A5 is calculated by "set value of the liquid volume of the positive electrode electrolyte / set value of the liquid volume of the negative electrode electrolyte." The set value A5 is stored in the third storage device.

[0062] The measured value A3 is calculated by the third calculation device. The measured value A3 is the difference between the measured value CN1 of the charge molar concentration of the active material in the negative electrode electrolyte at the first time point and the measured value CN2 of the charge molar concentration of the active material in the negative electrode electrolyte at the second time point, i.e., "CN2 - CN1."

[0063] The measured value CNn of the charge molar concentration of the active material in the anode electrolyte at a certain point in time is the charge molar concentration of the active material in the anode electrolyte corresponding to the potential VN of the anode electrolyte itself at a certain point in time. The charge molar concentration of the active material in the anode electrolyte corresponding to the potential VN of the anode electrolyte itself is stored in the second storage device. When the anode monitor cell 2N is provided, the potential VN of the anode electrolyte itself is determined by the anode monitor cell 2N. When the anode monitor cell 2N is not provided, the potential VN of the anode electrolyte itself is determined by the difference between the potential VP of the positive electrode electrolyte itself determined by the positive electrode monitor cell 2P and the open-circuit voltage VR of the redox flow battery system 1 determined by the bipolar electrode monitor cell 2B, i.e., "VP - VR."

[0064] The fourth calculation device calculates a calculated value A4 of the amount of change in the charge molar concentration of the active material in the negative electrode electrolyte. The calculated value A4 is the product of the measured value A1 of the amount of change in the charge molar concentration of the active material in the positive electrode electrolyte and a set value A7 of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte, i.e., "A1 x A7." The set value A7 is calculated by "set value of the liquid volume of the negative electrode electrolyte / set value of the liquid volume of the positive electrode electrolyte." The set value A7 is stored in the fourth storage device.

[0065] The fifth calculation device calculates a calculated value A6 of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte. Calculated value A6 is calculated by the ratio of measured value A1 of the amount of change in the charge molar concentration of the active material in the positive electrode electrolyte to measured value A3 of the amount of change in the charge molar concentration of the active material in the negative electrode electrolyte, i.e., "(CP2-CP1) / (CN2-CN1)."

[0066] The sixth calculation device calculates a calculated value A8 of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte. Calculated value A8 is calculated from the ratio of measured value A3 of the amount of change in the charge molar concentration of the active material in the negative electrode electrolyte to measured value A1 of the amount of change in the charge molar concentration of the active material in the positive electrode electrolyte, i.e., "(CN2-CN1) / (CP2-CP1)."

[0067] The pump controller 34 activates and stops the first pump 5g and the second pump 6g.

[0068] The alarm controller 36 issues an operation command to the alarm device 100. That is, the alarm controller 36 activates and deactivates the alarm device 100.

[0069] [Alarm Device] The alarm device 100 is a device that issues an alarm. The alarm device 100 can notify the operator operating the redox flow battery system 1 that the above-described specific conditions are met. That is, the alarm device 100 can notify the operator that the above-described symptoms are observed. The operator can take measures to prevent overcharging-related problems before overcharging occurs. Furthermore, the operator can maximize the charging or discharging time of the redox flow battery system 1. The operator can also stop charging or discharging. Stopping charging or discharging more reliably prevents overcharging. The alarm device 100 is, for example, at least one of a device that allows visual confirmation and a device that allows auditory confirmation. Examples of devices that allow visual confirmation include a lighting device such as a lamp and a display device such as a monitor that displays letters or symbols. Examples of devices that allow auditory confirmation include an audio output device such as a buzzer or speaker.

[0070] [Method for Operating a Redox Flow Battery System] The method for operating a redox flow battery system of this embodiment uses the redox flow battery system 1 of this embodiment, and supplies a positive electrode electrolyte and a negative electrode electrolyte to the main cell 10 to perform charging and discharging. The method for operating a redox flow battery system of this embodiment includes a first method or a second method. The first method includes steps P1, P2, P3, and P4A. The first method may further include step P4B. Step P4B is performed after step P4A. The second method includes steps P1, P2, P5, and P6A. The second method may further include step P6B. Step P6B is performed after step P6A.

[0071] In step P1, an actual measurement value A1 of the change in charge molar concentration of the active material in the positive electrode electrolyte is obtained. In step P2, an actual measurement value A3 of the change in charge molar concentration of the active material in the negative electrode electrolyte is obtained.

[0072] In process P3, a calculated value A2 of the change in the charge molar concentration of the active material in the positive electrode electrolyte is obtained. Alternatively, in process P3, a calculated value A4 of the change in the charge molar concentration of the active material in the negative electrode electrolyte is obtained. In process P4A, if the calculated value A2 deviates from the actual measured value A1 by a predetermined value or more, an operation command is issued to the alarm device 100. Alternatively, in process P4A, if the calculated value A4 deviates from the actual measured value A3 by a predetermined value or more, an operation command is issued to the alarm device 100. Upon receiving the operation command, the alarm device 100 issues an alarm to the operator. In process P4B, charging or discharging of the main cell 10 is stopped. When charging or discharging of the main cell 10 is stopped, the first pump 5g and the second pump 6g are stopped by the pump controller 34.

[0073] In process P5, a calculated value A6 of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte is calculated. Alternatively, in process P5, a calculated value A8 of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte is calculated. In process P6A, if the calculated value A6 deviates from the set value A5 by a predetermined value or more, an operation command is issued to the alarm device 100. Alternatively, in process P6A, if the calculated value A8 deviates from the set value A7 by a predetermined value or more, an operation command is issued to the alarm device 100. Upon receiving the operation command, the alarm device 100 issues an alarm to the operator. In process P6B, charging or discharging of the main cell 10 is stopped. When charging or discharging of the main cell 10 is stopped, the first pump 5g and the second pump 6g are stopped by the pump controller 34.

[0074] [Control Procedure] The control procedure performed by the controller 3 during operation will be described. The controller 3 performs steps S1 to S5 shown in Fig. 2. The controller 3 may terminate the control after performing step S5, or may perform step S5 and then further perform step S6 without terminating the control, and then terminate the control.

[0075] Step S1 calculates the actual measurement value A1. Step S1 corresponds to the above-described process P1. Step S2 calculates the actual measurement value A3. Step S2 corresponds to the above-described process P2. Steps S1 and S2 are processed in parallel. Step S3 calculates the calculated value A2. Step S3 corresponds to the above-described process P3. Step S4 determines whether the calculated value A2 deviates from the actual measurement value A1 by a predetermined value X or more. Step S5 issues an operation command to the alarm device 100 if the condition of step S4 is met. The alarm device 100, having received the operation command, issues an alarm to the operator. Steps S4 and S5 correspond to the above-described process P4A. Step S6 stops charging or discharging. Step S6 corresponds to the above-described process P4B. If the condition of step S4 is not met, the alarm device 100 is not driven and continues charging or discharging without issuing an alarm. Unlike the present embodiment, steps S1 and S2 may be processed temporally before or after step S3, as long as they are processed before step S3.

[0076] In step S3, calculated value A4 may be calculated instead of calculated value A2. This step S3 corresponds to step P3 described above. In this case, in step S4, it is determined whether calculated value A4 deviates from actual measurement value A3 by a predetermined value or more. This step S4 corresponds to step P4A described above.

[0077] In step S3, calculated value A6 may be calculated instead of calculated value A2. This step S3 corresponds to step P5 described above. In this case, in step S4, it is determined whether calculated value A6 deviates from set value A5 by a predetermined value or more. This step S4 corresponds to step P6A described above.

[0078] In step S3, calculated value A8 may be calculated instead of calculated value A2. This step S3 corresponds to step P5 described above. In this case, in step S4, it is determined whether calculated value A8 deviates from set value A7 by a predetermined value or more. This step S4 corresponds to step P6A described above.

[0079] By performing steps S1 to S5, the redox flow battery system 1 and the method for operating a redox flow battery system can detect signs that overcharging is likely to occur in the future regardless of the state of charge if the redox flow battery system 1 continues to operate. Therefore, the redox flow battery system 1 and the method for operating a redox flow battery system can predict the occurrence of overcharging regardless of the state of charge. The redox flow battery system 1 and the method for operating a redox flow battery system issue an operation command to the alarm device 100, which then issues an alarm, thereby notifying the operator operating the redox flow battery system 1 that the above signs have been observed. The operator can prepare measures to prevent malfunctions due to overcharging before overcharging actually occurs. Furthermore, the operator can maximize the use time of the redox flow battery system 1. The operator can also stop charging or discharging. Stopping charging or discharging more reliably prevents overcharging from occurring. By performing step S6 after step S5, the redox flow battery system 1 and the method for operating a redox flow battery system can automatically stop charging or discharging without the operator having to perform any work to stop charging or discharging. Therefore, the redox flow battery system 1 and the method for operating a redox flow battery system can automatically prevent overcharging.

[0080] Second Embodiment Redox Flow Battery System A redox flow battery system 1 of the second embodiment will be described with reference to FIG. 3 . The redox flow battery system 1 of the second embodiment differs from the redox flow battery system 1 of the first embodiment in that it does not include a positive reference electrode and a negative reference electrode, but includes a reference cathode electrolyte 8a and a reference anode electrolyte 8b. FIG. 3 shows an example in which both the reference cathode electrolyte 8a and the reference anode electrolyte 8b are included. Although not shown, unlike FIG. 3 , it is sufficient to include either the reference cathode electrolyte 8a or the reference anode electrolyte 8b. For example, the redox flow battery system 1 may not include a positive electrode monitor cell 2P and a reference cathode electrolyte 8a, but may include a bipolar electrode monitor cell 2B, an anode monitor cell 2N, and a reference anode electrolyte 8b. The following description will focus on the differences from the first embodiment. Descriptions of configurations and effects similar to those of the first embodiment may be omitted.

[0081] (Positive Electrode Monitor Cell) Although not shown, the positive electrode monitor cell 2P is separated into a positive electrode cell and a reference cell by a diaphragm. Reference positive electrode electrolyte 8a flows through the reference cell of the positive electrode monitor cell 2P. The reference positive electrode electrolyte 8a is stored in a first tank 8c. The reference positive electrode electrolyte 8a circulates between the positive electrode monitor cell 2P and the first tank 8c via a seventh supply pipe 8e, a seventh discharge pipe 8f, and a third pump 8i. The seventh supply pipe 8e connects the first tank 8c to the reference cell of the positive electrode monitor cell 2P. The seventh discharge pipe 8f connects the reference cell of the positive electrode monitor cell 2P to the first tank 8c. The third pump 8i pumps out the reference positive electrode electrolyte 8a from the first tank 8c. The third pump 8i is provided midway through the seventh supply pipe 8e. The operation or stop of the third pump 8i is controlled by a pump controller 34. The second potential measuring device 7b measures the potential difference between the potential of the positive electrode electrolyte flowing in the positive electrode cell of the positive electrode monitoring cell 2P and the potential of the reference positive electrode electrolyte 8a flowing in the reference cell of the positive electrode monitoring cell 2P. The measured potential difference is used as the absolute potential VP of the positive electrode electrolyte itself supplied to the positive electrode monitoring cell 2P.

[0082] (Negative Electrode Monitor Cell) Although not shown, the negative electrode monitor cell 2N is separated into an anode cell and a reference cell by a diaphragm. The reference cell of the negative electrode monitor cell 2N is supplied with reference anode electrolyte 8b. The reference anode electrolyte 8b is stored in the second tank 8d. The reference anode electrolyte 8b circulates between the negative electrode monitor cell 2N and the second tank 8d via an eighth supply pipe 8g, an eighth discharge pipe 8h, and a fourth pump 8j. The eighth supply pipe 8g connects the second tank 8d to the reference cell of the negative electrode monitor cell 2N. The eighth discharge pipe 8h connects the reference cell of the negative electrode monitor cell 2N to the second tank 8d. The fourth pump 8j pumps out the reference anode electrolyte 8b from the second tank 8d. The fourth pump 8j is provided midway through the eighth supply pipe 8g. The driving or stopping of the fourth pump 8j is controlled by the pump controller 34. The third potential measuring device 7c measures the potential difference between the potential of the anode electrolyte flowing in the anode cell of the anode monitor cell 2N and the potential of the reference anode electrolyte 8b flowing in the reference cell of the anode monitor cell 2N. The measured potential difference is used as the absolute potential VN of the anode electrolyte itself supplied to the anode monitor cell 2N.

[0083] There are no particular limitations on the reference positive electrode electrolyte 8a and the reference negative electrode electrolyte 8b, as long as the charge molar concentrations of the active materials are clearly known.

[0084] Third Embodiment Redox Flow Battery System A redox flow battery system 1 of a third embodiment will be described with reference to Figures 4 and 5. The redox flow battery system 1 of the third embodiment differs from the redox flow battery system 1 of the first embodiment in the specific conditions under which the controller 3 issues an operation command to the alarm device 100. The following description will focus on the differences from the first embodiment. Descriptions of configurations and effects similar to those of the first embodiment may be omitted.

[0085] [Monitor Cell] The redox flow battery system 1 of this embodiment may include at least two monitor cells selected from the two electrode monitor cells 2B, the positive electrode monitor cell 2P, and the negative electrode monitor cell 2N. Figures 4 and 5 show an example in which the redox flow battery system 1 includes all of the two electrode monitor cells 2B, the positive electrode monitor cell 2P, and the negative electrode monitor cell 2N. Although not shown, unlike Figures 4 and 5, for example, the redox flow battery system 1 may not include the positive electrode monitor cell 2P, but may include only the two electrode monitor cells 2B and the negative electrode monitor cell 2N.

[0086] The redox flow battery system 1 of Embodiment 3 has a mixing section 9 that mixes the positive electrode electrolyte and the negative electrode electrolyte. The mixing section 9 shown in Fig. 4 includes a first pipe 9a, a second pipe 9b, a first valve section 9d, a second valve section 9e, a third valve section 9f, and a fourth valve section 9g.

[0087] The positive electrode electrolyte flows through the first pipe 9a. The first pipe 9a connects the first discharge pipe 5b and the second discharge pipe 6b. The first pipe 9a is connected to the first discharge pipe 5b upstream of the connection point between the first discharge pipe 5b and the fifth discharge pipe 5f, and to the second discharge pipe 6b between the connection point between the second discharge pipe 6b and the fourth discharge pipe 6d and the fourth valve unit 9g. "Upstream of the connection point between the first discharge pipe 5b and the fifth discharge pipe 5f" refers to a position closer to the main cell 10 than the connection point between the first discharge pipe 5b and the fifth discharge pipe 5f.

[0088] The second pipe 9b allows the negative electrode electrolyte to flow through. The second pipe 9b connects the second discharge pipe 6b and the first discharge pipe 5b. The second pipe 9b is connected to a location upstream of the connection point of the second discharge pipe 6b and the sixth discharge pipe 6f in the second discharge pipe 6b, and to a location upstream of the connection point of the first discharge pipe 5b and the third discharge pipe 5d in the first discharge pipe 5b, between the third valve unit 9f and the connection point of the first discharge pipe 5b and the third discharge pipe 5d in the first discharge pipe 5b. "Upstream of the connection point of the second discharge pipe 6b and the sixth discharge pipe 6f" refers to a position closer to the main cell 10 than the connection point of the second discharge pipe 6b and the sixth discharge pipe 6f.

[0089] The first valve unit 9d opens and closes the first pipe 9a. The first valve unit 9d is provided on the first pipe 9a. The second valve unit 9e opens and closes the second pipe 9b. The second valve unit 9e is provided on the second pipe 9b. The third valve unit 9f opens and closes the first discharge pipe 5b. The third valve unit 9f is provided on the first discharge pipe 5b, between a connection point between the first discharge pipe 5b and the fifth discharge pipe 5f and a connection point between the first discharge pipe 5b and the second pipe 9b. The fourth valve unit 9g opens and closes the second discharge pipe 6b. The fourth valve unit 9g is provided on the second discharge pipe 6b, between a connection point between the second discharge pipe 6b and the sixth discharge pipe 6f and a connection point between the second discharge pipe 6b and the first pipe 9a. The first valve unit 9d to the fourth valve unit 9g are all solenoid valves. The first valve unit 9d to the fourth valve unit 9g are all equipped with wireless communication devices or are connected to a signal line connected to the controller 3.

[0090] Unlike the example shown in Fig. 4, although not shown, the system may not include the first to fourth valve units, but may instead include a first three-way valve provided at a connection point of the first discharge pipe 5b between the first discharge pipe 5b and the first pipe 9a, and a second three-way valve provided at a connection point of the second discharge pipe 6b between the second discharge pipe 6b and the second pipe 9b. The first three-way valve selectively opens the first discharge pipe 5b and closes the first pipe 9a, or closes the first discharge pipe 5b and opens the first pipe 9a. The second three-way valve selectively opens the second discharge pipe 6b and closes the second pipe 9b, or closes the second discharge pipe 6b and opens the second pipe 9b.

[0091] The mixing unit 9 shown in Fig. 5 includes a third pipe 9c and a fifth valve unit 9h. The third pipe 9c connects the positive electrode electrolyte tank 41 and the negative electrode electrolyte tank 42. The third pipe 9c is connected to, for example, the lower part of the positive electrode electrolyte tank 41 and the lower part of the negative electrode electrolyte tank 42. The fifth valve unit 9h opens and closes the third pipe 9c. The fifth valve unit 9h is provided in the third pipe 9c. The fifth valve unit 9h is an electromagnetic valve. The fifth valve unit 9h includes a wireless communication device, or is connected to a signal line connected to the controller 3.

[0092] [Controller] The determiner 33 included in the controller 3 of this embodiment determines whether a specific condition is satisfied. The specific condition is the following fifth or sixth condition. That is, the determiner 33 determines whether the fifth or sixth condition is satisfied.

[0093] The fifth condition is that a calculated value A10 of the ratio of the active material concentration of the positive electrode electrolyte to the active material concentration of the negative electrode electrolyte deviates by a predetermined value or more from a set value A9 of the ratio of the active material concentration of the positive electrode electrolyte to the active material concentration of the negative electrode electrolyte. The sixth condition is that a calculated value A12 of the ratio of the active material concentration of the negative electrode electrolyte to the active material concentration of the positive electrode electrolyte deviates by a predetermined value or more from a set value A11 of the ratio of the active material concentration of the negative electrode electrolyte to the active material concentration of the positive electrode electrolyte.

[0094] Satisfying the fifth or sixth condition regardless of the state of charge is an indication that there is a high possibility of overcharging occurring in the future if the redox flow battery system 1 continues to operate. The redox flow battery system 1 can detect the indication by the controller 3 determining that the fifth or sixth condition is satisfied. Therefore, the redox flow battery system 1 can predict that overcharging will occur regardless of the state of charge. The redox flow battery system 1 that can predict that overcharging will occur can prevent overcharging from occurring.

[0095] The memory device 32 included in the controller 3 of this embodiment includes a fifth memory device and a sixth memory device. The fifth memory device stores a set value A9 for the active material concentration ratio of the positive electrode electrolyte to the negative electrode electrolyte. The set value A9 is a value determined in advance. The sixth memory device stores a set value A11 for the active material concentration ratio of the negative electrode electrolyte to the positive electrode electrolyte. The set value A11 is a value determined in advance.

[0096] The arithmetic device 31 included in the controller 3 of this embodiment includes a seventh arithmetic device and an eighth arithmetic device. The seventh arithmetic device calculates a calculated value A10 of the active material concentration ratio of the positive electrode electrolyte to the negative electrode electrolyte. The eighth arithmetic device calculates a calculated value A12 of the active material concentration ratio of the negative electrode electrolyte to the positive electrode electrolyte. The calculated value A10 is calculated from the potential of the positive electrode electrolyte itself, the potential of the negative electrode electrolyte itself, and a set value A13 of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte. The calculated value A12 is calculated from the potential of the positive electrode electrolyte itself, the potential of the negative electrode electrolyte itself, and a set value A14 of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte. The set values ​​A13 and A14 are calculated by equalizing the liquid volumes of the positive electrode electrolyte and the negative electrode electrolyte. The liquid volumes of the positive electrode electrolyte and the negative electrode electrolyte are equalized by the mixer 9, as will be described in detail later.

[0097] The calculated value A10 is obtained by "VL x (KN / KP)". The calculated value A12 is obtained by "(1 / VL) x (KP / KN)". VL: Set value A13 of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte 1 / VL: Set value A14 of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte KN = e α２ / (1+e α２ )-e α１ / (1+e α１ ) KP = e β２ / (1+e β２ )-e β１ / (1+e β１ ) α1=(VN1-EN0)×{(n×F) / (R×T)} α2=(VN2-EN0)×{(n×F) / (R×T)} β1=(VP1-EP0)×{(n×F) / (R×T)} β2=(VP2-EP0)×{(n×F) / (R×T)}

[0098] VN1: potential of the negative electrode electrolyte itself at the first time point VN2: potential of the negative electrode electrolyte itself at the second time point EN0: redox standard potential of the negative electrode VP1: potential of the positive electrode electrolyte itself at the first time point VP2: potential of the positive electrode electrolyte itself at the second time point EP0: redox standard potential of the positive electrode n: number of electrons F: Faraday constant R: gas constant T: temperature

[0099] "KN" and "KP" can be derived using the Nernst equation. When the negative electrode monitor cell 2N is provided, the potentials VN1 and VN2 of the negative electrode electrolyte itself are determined by the negative electrode monitor cell 2N. When the negative electrode monitor cell 2N is not provided, the potential VN1 of the negative electrode electrolyte itself is determined by the difference between the potential VP1 of the positive electrode electrolyte itself determined by the positive electrode monitor cell 2P and the open-circuit voltage VR1 of the redox flow battery system 1 determined by the bipolar electrode monitor cell 2B, i.e., "VP1 - VR1." When the negative electrode monitor cell 2N is not provided, the potential VN2 of the negative electrode electrolyte itself is determined by "VP2 - VR2." When the positive electrode monitor cell 2P is provided, the potential VP1 of the positive electrode electrolyte itself is determined by the positive electrode monitor cell 2P. When the positive electrode monitor cell 2P is not provided, the potential VP1 of the positive electrode electrolyte itself is calculated as the sum of the potential VN1 of the negative electrode electrolyte itself calculated by the negative electrode monitor cell 2N and the open-circuit voltage VR1 of the redox flow battery system 1 calculated by the bipolar electrode monitor cell 2B, i.e., "VR1 + VN1." When the positive electrode monitor cell 2P is not provided, the potential VP2 of the positive electrode electrolyte itself is calculated as "VR2 + VN2."

[0100] The controller 3 of this embodiment further includes a valve controller 35. The valve controller 35 shown in Fig. 4 controls the opening and closing of the first valve unit 9d to the fourth valve unit 9g. The valve controller 35 shown in Fig. 5 controls the opening and closing of the fifth valve unit 9h. The program stored in the memory of the controller 3 includes program code related to the process of opening and closing the first valve unit 9d to the fourth valve unit 9g or the process of opening and closing the fifth valve unit 9h.

[0101] 4, when the main cell 10 is operated to charge or discharge, the valve controller 35 closes the first valve 9d and the second valve 9e and opens the third valve 9f and the fourth valve 9g. The pump controller 34 drives the first pump 5g and the second pump 6g. The flow paths of the positive electrode electrolyte and the negative electrode electrolyte are the same as those in the first embodiment.

[0102] 4 , if there is a difference between the liquid level in the positive electrode electrolyte tank 41 and the liquid level in the negative electrode electrolyte tank 42, the valve controller 35 closes the third valve unit 9 f and the fourth valve unit 9 g and opens the first valve unit 9 d and the second valve unit 9 e. If the amount of positive electrode electrolyte in the positive electrode electrolyte tank 41 is greater than the amount of negative electrode electrolyte in the negative electrode electrolyte tank 42, the pump controller 34 drives the first pump 5 g and stops the second pump 6 g. In this case, the positive electrode electrolyte discharged from the main cell 10 flows sequentially through the first discharge pipe 5 b, the first pipe 9 a, the second discharge pipe 6 b, and the negative electrode electrolyte tank 42. If the amount of negative electrode electrolyte in the negative electrode electrolyte tank 42 is greater than the amount of positive electrode electrolyte in the positive electrode electrolyte tank 41, the pump controller 34 stops the first pump 5 g and drives the second pump 6 g. In this case, the anode electrolyte discharged from the main cell 10 flows in this order through the second discharge pipe 6b, the second pipe 9b, the first discharge pipe 5b, and the cathode electrolyte tank 41. In either case, when the liquid level in the cathode electrolyte tank 41 and the liquid level in the anode electrolyte tank 42 become equal, the valve controller 35 closes the first valve unit 9d and the second valve unit 9e and opens the third valve unit 9f and the fourth valve unit 9g.

[0103] 5, when the main cell 10 is charged or discharged, the valve controller 35 closes the fifth valve unit 9h. The pump controller 34 drives the first pump 5g and the second pump 6g. The flow paths of the positive electrode electrolyte and the negative electrode electrolyte are the same as those in the first embodiment.

[0104] 5 , if there is a difference in the liquid level in the positive electrode electrolyte tank 41 and the negative electrode electrolyte tank 42, the valve controller 35 opens the fifth valve unit 9h. The pressure difference between the electrolyte in the positive electrode electrolyte tank 41 and the electrolyte in the negative electrode electrolyte tank 42 causes the electrolyte to flow through the third pipe 9c from the tank with the higher liquid level to the tank with the lower liquid level. When the liquid level in the positive electrode electrolyte tank 41 and the liquid level in the negative electrode electrolyte tank 42 become equal, the flow of the electrolyte through the third pipe 9c stops. The valve controller 35 closes the fifth valve unit 9h.

[0105] [Method for operating a redox flow battery system] The method for operating a redox flow battery system of this embodiment uses the redox flow battery system 1 of this embodiment. The method for operating a redox flow battery system of this embodiment includes steps P7, P8, P9, and P10A. The method for operating a redox flow battery system of this embodiment may further include step P10B. Step P10B is performed after step 10A.

[0106] In process P7, the potentials VP1 and VP2 of the positive electrode electrolyte itself are determined using the positive electrode monitor cell 2P. Alternatively, in process P7, the potentials VP1 and VP2 of the positive electrode electrolyte itself are determined using the bipolar electrode monitor cell 2B and the negative electrode monitor cell 2N. In process P8, the potentials VN1 and VN2 of the negative electrode electrolyte itself are determined using the negative electrode monitor cell 2N. Alternatively, in process P8, the potentials VN1 and VN2 of the negative electrode electrolyte itself are determined using the bipolar electrode monitor cell 2B and the positive electrode monitor cell 2P.

[0107] In process P9, a calculated value A10 of the active material concentration ratio of the positive electrolyte to the negative electrolyte is determined based on the potentials VP1 and VP2 of the positive electrolyte itself, the potentials VN1 and VN2 of the negative electrolyte itself, and a set value A13 of the volume ratio of the positive electrolyte to the negative electrolyte. Alternatively, in process P9, a calculated value A12 of the active material concentration ratio of the negative electrolyte to the positive electrolyte is determined based on the potentials VP1 and VP2 of the positive electrolyte itself, the potentials VN1 and VN2 of the negative electrolyte, and a set value A14 of the volume ratio of the negative electrolyte to the positive electrolyte.

[0108] In process P10A, when a calculated value A10 of the active material concentration ratio of the positive electrode electrolyte to the negative electrode electrolyte deviates by a predetermined value or more from a set value A9 of the active material concentration ratio of the positive electrode electrolyte to the negative electrode electrolyte, process P10A issues an operation command to alarm device 100. Alternatively, when a calculated value A12 of the active material concentration ratio of the negative electrode electrolyte to the positive electrode electrolyte deviates by a predetermined value or more from a set value A11 of the active material concentration ratio of the negative electrode electrolyte to the positive electrode electrolyte, process P10A issues an operation command to alarm device 100. In process P10B, charging or discharging of main cell 10 is stopped.

[0109] [Control Procedure] The control procedure performed by the controller 3 during operation will be described. The controller 3 performs steps S11 to S15 shown in Fig. 6. The controller 3 may terminate the control after performing step S15, or may further perform step S16 after performing step S15 without terminating the control.

[0110] Step S11 determines the potentials VP1 and VP2 of the positive electrode electrolyte itself. Step S11 corresponds to step P7 described above. Step S12 determines the potentials VN1 and VN2 of the negative electrode electrolyte itself. Step S12 corresponds to step P8 described above. Steps S11 and S12 are processed in parallel. Step S13 calculates a calculated value A10. Step S13 corresponds to step P9 described above. Step S14 determines whether the calculated value A10 deviates from the set value A9 by a predetermined value X or more. Step S15 issues an operation command to the alarm device 100 if the condition of step S14 is met. Steps S14 and S15 correspond to step P10A described above. Step S16 stops charging or discharging. Step S16 corresponds to step P10B described above. If the condition of step S14 is not met, charging or discharging is maintained.

[0111] In step S13, calculated value A12 may be calculated instead of calculated value A10. This step S13 corresponds to the above-mentioned process P9. In that case, in step S14, it is determined whether calculated value A12 deviates from set value A11 by a predetermined value X or more. This step S14 corresponds to the above-mentioned process P10A.

[0112] Fourth Embodiment Redox Flow Battery System The redox flow battery system of Embodiment 4 can include the reference positive electrode electrolyte 8a and the reference negative electrode electrolyte 8b described in Embodiment 2 with reference to Fig. 3, without including the positive and negative reference electrodes in the redox flow battery system 1 of Embodiment 3. Both the reference positive electrode electrolyte 8a and the reference negative electrode electrolyte 8b may be included, or either the reference positive electrode electrolyte 8a or the reference negative electrode electrolyte 8b may be included. For example, the redox flow battery system may not include the positive electrode monitor cell 2P and the reference positive electrode electrolyte 8a, but may include both the positive electrode monitor cell 2B, the negative electrode monitor cell 2N, and the reference negative electrode electrolyte 8b.

[0113] The present invention is not limited to these examples, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0114] For example, in the second embodiment, an example in which the reference positive electrode electrolyte and the reference negative electrode electrolyte are circulated has been described, but the reference positive electrode electrolyte and the reference negative electrode electrolyte may simply be filled in the reference cell without being circulated, in which case the first tank, the second tank, the seventh supply pipe, the seventh discharge pipe, the eighth supply pipe, the eighth discharge pipe, the third pump, and the fourth pump may not be used.

[0115] In the redox flow battery system, when the above-described specific conditions are met, the controller may stop charging or discharging the main cell without activating the alarm device. That is, in the redox flow battery system, the controller may stop charging or discharging the main cell without the alarm device issuing an alarm.

[0116] REFERENCE SIGNS LIST 1 Redox flow battery system, 10 Main cell 2B Both electrode monitor cells, 2P Positive electrode monitor cell, 2N Negative electrode monitor cell 3 Controller, 31 Arithmetic unit, 32 Storage device, 33 Determinator 34 Pump controller, 35 Valve controller, 36 Alarm controller 4P Positive electrode circulation mechanism, 4N Negative electrode circulation mechanism 41 Positive electrode electrolyte tank, 42 ​​Negative electrode electrolyte tank 5a First supply pipe, 5b First discharge pipe, 5c Third supply pipe, 5d Third discharge pipe 5e Fifth supply pipe, 5f Fifth discharge pipe, 5g First pump 6a Second supply pipe, 6b Second discharge pipe, 6c Fourth supply pipe, 6d Fourth discharge pipe 6e Sixth supply pipe, 6f Sixth discharge pipe, 6g Second pump 7P Positive electrode reference electrode, 7N Negative electrode reference electrode 7a First potential meter, 7b Second potential meter, 7c Third potential measuring device 8a Reference positive electrode electrolyte, 8b Reference negative electrode electrolyte 8c First tank, 8d Second tank, 8e Seventh supply pipe, 8f Seventh discharge pipe 8g Eighth supply pipe, 8h Eighth discharge pipe, 8i Third pump, 8j Fourth pump 9 Mixing part, 9a First pipe, 9b Second pipe, 9c Third pipe 9d First valve part, 9e Second valve part, 9f Third valve section, 9g Fourth valve section, 9h Fifth valve section 100 Alarm device 300 AC / DC converter, 310 Power generation section, 320 Substation equipment, 330 Load

Claims

1. A main cell that performs charging and discharging by supplying a positive electrode electrolyte and a negative electrode electrolyte, A plurality of monitor cells selected from the group consisting of a bipolar monitor cell, a positive electrode monitor cell, and a negative electrode monitor cell, A controller that controls charging and discharging of the main cell, and is provided with, In the bipolar monitor cell, the positive electrode electrolyte and the negative electrode electrolyte common to the main cell are supplied, In the positive electrode monitor cell, the positive electrode electrolyte common to the main cell is supplied without supplying the negative electrode electrolyte common to the main cell, In the negative electrode monitor cell, the negative electrode electrolyte common to the main cell is supplied without supplying the positive electrode electrolyte common to the main cell, When the calculated value of the change amount of the charged molar concentration of the active material of the positive electrode electrolyte deviates from the measured value of the change amount of the charged molar concentration of the active material of the positive electrode electrolyte by a predetermined value or more, or when the calculated value of the change amount of the charged molar concentration of the active material of the negative electrode electrolyte deviates from the measured value of the change amount of the charged molar concentration of the active material of the negative electrode electrolyte by a predetermined value or more, the controller issues an operation command to an alarm device, The measured value of the change amount of the charged molar concentration of the active material of the positive electrode electrolyte is obtained by the positive electrode monitor cell, or by the bipolar monitor cell and the negative electrode monitor cell, The calculated value of the change amount of the charged molar concentration of the active material of the positive electrode electrolyte is obtained by the measured value of the change amount of the charged molar concentration of the active material of the negative electrode electrolyte and the set value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte, The measured value of the change amount of the charged molar concentration of the active material of the negative electrode electrolyte is obtained by the negative electrode monitor cell, or by the bipolar monitor cell and the positive electrode monitor cell, The calculated value of the change amount of the charged molar concentration of the active material of the negative electrode electrolyte is obtained by the measured value of the change amount of the charged molar concentration of the active material of the positive electrode electrolyte and the set value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte, A redox flow battery system.

2. A main cell that performs charging and discharging by supplying a positive electrode electrolyte and a negative electrode electrolyte, A plurality of monitor cells selected from the group consisting of a bipolar monitor cell, a positive electrode monitor cell, and a negative electrode monitor cell, A controller that controls charging and discharging of the main cell, and is provided with, In the bipolar monitor cell, the positive electrode electrolyte and the negative electrode electrolyte common to the main cell are supplied, The positive electrode monitor cell is supplied with the positive electrode electrolyte common to the main cell without being supplied with the negative electrode electrolyte common to the main cell. The negative electrode monitor cell is supplied with the negative electrode electrolyte common to the main cell without being supplied with the positive electrode electrolyte common to the main cell. When the calculated value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte deviates from the set value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte by a predetermined value or more, or when the calculated value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte deviates from the set value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte by a predetermined value or more, the controller issues an operation command to the alarm device. The calculated value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte and the calculated value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte are obtained from the measured value of the change in the charged molar concentration of the active material in the positive electrode electrolyte and the measured value of the change in the charged molar concentration of the active material in the negative electrode electrolyte. The measured value of the change in the charged molar concentration of the active material in the positive electrode electrolyte is obtained by the positive electrode monitor cell or by the bipolar monitor cell and the negative electrode monitor cell. The measured value of the change in the charged molar concentration of the active material in the negative electrode electrolyte is obtained by the negative electrode monitor cell or by the bipolar monitor cell and the positive electrode monitor cell. Redox flow battery system.

3. A main cell that performs charging and discharging by supplying a positive electrode electrolyte and a negative electrode electrolyte, A plurality of monitor cells selected from the group consisting of a bipolar monitor cell, a positive electrode monitor cell, and a negative electrode monitor cell, A controller that controls charging and discharging of the main cell, The bipolar monitor cell is supplied with the positive electrode electrolyte and the negative electrode electrolyte common to the main cell, The positive electrode monitor cell is supplied with the positive electrode electrolyte common to the main cell without being supplied with the negative electrode electrolyte common to the main cell. The negative electrode monitor cell is supplied with the negative electrode electrolyte common to the main cell without being supplied with the positive electrode electrolyte common to the main cell. When the calculated value of the active material concentration ratio of the positive electrode electrolyte to the negative electrode electrolyte deviates from the set value by a predetermined value or more with respect to the set value of the active material concentration ratio of the positive electrode electrolyte to the negative electrode electrolyte, or when the calculated value of the active material concentration ratio of the negative electrode electrolyte to the positive electrode electrolyte deviates from the set value by a predetermined value or more with respect to the set value of the active material concentration ratio of the negative electrode electrolyte to the positive electrode electrolyte, the controller issues an operation command to the alarm device. The calculated value of the active material concentration ratio of the positive electrode electrolyte to the negative electrode electrolyte is obtained from the potential of the positive electrode electrolyte, the potential of the negative electrode electrolyte, and the set value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte. The calculated value of the active material concentration ratio of the negative electrode electrolyte to the positive electrode electrolyte is obtained from the potential of the positive electrode electrolyte, the potential of the negative electrode electrolyte, and the set value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte. The potential of the positive electrode electrolyte is obtained by the positive electrode monitor cell or by the bipolar monitor cell and the negative electrode monitor cell. The potential of the negative electrode electrolyte is obtained by the negative electrode monitor cell or by the bipolar monitor cell and the positive electrode monitor cell. Redox flow battery system.

4. The positive electrode monitor cell obtains a measured value of the change amount of the charged molar concentration of the active material of the positive electrode electrolyte based on the absolute potential of the positive electrode electrolyte. The negative electrode monitor cell obtains a measured value of the change amount of the charged molar concentration of the active material of the negative electrode electrolyte based on the absolute potential of the negative electrode electrolyte. The redox flow battery system according to claim 1.

5. The positive electrode monitor cell obtains a measured value of the change amount of the charged molar concentration of the active material of the positive electrode electrolyte based on the absolute potential of the positive electrode electrolyte. The negative electrode monitor cell obtains a measured value of the change amount of the charged molar concentration of the active material of the negative electrode electrolyte based on the absolute potential of the negative electrode electrolyte. The redox flow battery system according to claim 2.

6. The positive electrode monitor cell measures the potential difference of the positive electrode electrolyte with respect to a positive electrode reference electrode with a known potential. The negative electrode monitor cell measures the potential difference of the negative electrode electrolyte with respect to a negative electrode reference electrode with a known potential. The redox flow battery system according to any one of claims 3 to 5.

7. The positive electrode monitor cell measures the potential difference of the positive electrode electrolyte with respect to a reference positive electrode electrolyte with a known change amount of the charged molar concentration of the active material. The negative electrode monitor cell measures the potential difference between the negative electrode electrolyte and a reference negative electrode electrolyte with a known change in the charging molar concentration of the active material, for the redox flow battery system according to any one of claims 3 to 5.

8. After the controller issues an operation command to the alarm device, the controller stops charging or discharging of the main cell, for the redox flow battery system according to claim 6.

9. After the controller issues an operation command to the alarm device, the controller stops charging or discharging of the main cell, for the redox flow battery system according to claim 7.

10. The bipolar monitor cell is provided in the circulation paths of the positive electrode electrolyte and the negative electrode electrolyte, The positive electrode monitor cell is provided in the circulation path of the positive electrode electrolyte, The negative electrode monitor cell is provided in the circulation path of the negative electrode electrolyte, for the redox flow battery system according to any one of claims 1 to 5.

11. An operation method of a redox flow battery system that supplies a positive electrode electrolyte and a negative electrode electrolyte to a main cell to perform charging and discharging, A step of obtaining a measured value of the change amount of the charging molar concentration of the active material of the positive electrode electrolyte by the positive electrode monitor cell or by the bipolar monitor cell and the negative electrode monitor cell; A step of obtaining a measured value of the change amount of the charging molar concentration of the active material of the negative electrode electrolyte by the negative electrode monitor cell or by the bipolar monitor cell and the positive electrode monitor cell; A step of obtaining a calculated value of the change amount of the charging molar concentration of the active material of the positive electrode electrolyte from the measured value of the change amount of the charging molar concentration of the active material of the negative electrode electrolyte and the set value of the liquid volume ratio of the positive electrode electrolyte with respect to the negative electrode electrolyte, or obtaining a calculated value of the change amount of the charging molar concentration of the active material of the negative electrode electrolyte from the measured value of the change amount of the charging molar concentration of the active material of the positive electrode electrolyte and the set value of the liquid volume ratio of the negative electrode electrolyte with respect to the positive electrode electrolyte; A step of issuing an operation command to an alarm device when the calculated value of the change amount of the charging molar concentration of the active material of the positive electrode electrolyte deviates from the measured value of the change amount of the charging molar concentration of the active material of the positive electrode electrolyte by a predetermined value or more, or when the calculated value of the change amount of the charging molar concentration of the active material of the negative electrode electrolyte deviates from the measured value of the change amount of the charging molar concentration of the active material of the negative electrode electrolyte by a predetermined value or more; and is provided, The same positive electrode electrolyte and negative electrode electrolyte as those of the main cell are supplied to the bipolar monitor cell, The positive electrode monitor cell is supplied with the positive electrode electrolyte common to the main cell without being supplied with the negative electrode electrolyte common to the main cell, The negative electrode monitor cell is supplied with the negative electrode electrolyte common to the main cell without being supplied with the positive electrode electrolyte common to the main cell, A method for operating a redox flow battery system.

12. A method for operating a redox flow battery system that supplies a positive electrode electrolyte and a negative electrode electrolyte to a main cell for charging and discharging, A step of obtaining a measured value of the change amount of the charged molar concentration of the active material of the positive electrode electrolyte by the positive electrode monitor cell or by the bipolar monitor cell and the negative electrode monitor cell; A step of obtaining a measured value of the change amount of the charged molar concentration of the active material of the negative electrode electrolyte by the negative electrode monitor cell or by the bipolar monitor cell and the positive electrode monitor cell; A step of obtaining a calculated value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte or a calculated value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte based on the measured value of the change amount of the charged molar concentration of the active material of the positive electrode electrolyte and the measured value of the change amount of the charged molar concentration of the active material of the negative electrode electrolyte; When the calculated value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte deviates from the set value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte by a predetermined value or more, or when the calculated value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte deviates from the set value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte by a predetermined value or more, a step of issuing an operation command to an alarm device, The bipolar monitor cell is supplied with the positive electrode electrolyte and the negative electrode electrolyte common to the main cell, The positive electrode monitor cell is supplied with the positive electrode electrolyte common to the main cell without being supplied with the negative electrode electrolyte common to the main cell, The negative electrode monitor cell is supplied with the negative electrode electrolyte common to the main cell without being supplied with the positive electrode electrolyte common to the main cell, A method for operating a redox flow battery system.

13. A method for operating a redox flow battery system that supplies a positive electrode electrolyte and a negative electrode electrolyte to a main cell for charging and discharging, A step of obtaining the potential of the positive electrode electrolyte by the positive electrode monitor cell or by the bipolar monitor cell and the negative electrode monitor cell; A step of obtaining the potential of the negative electrode electrolyte by the negative electrode monitor cell or by the bipolar monitor cell and the positive electrode monitor cell; A step of obtaining a calculated value of the active material concentration ratio of the positive electrode electrolyte to the negative electrode electrolyte based on the potential of the positive electrode electrolyte, the potential of the negative electrode electrolyte, and a set value of the liquid volume ratio of the positive electrode electrolyte to the negative electrode electrolyte, or a calculated value of the active material concentration ratio of the negative electrode electrolyte to the positive electrode electrolyte based on the potential of the positive electrode electrolyte, the potential of the negative electrode electrolyte, and a set value of the liquid volume ratio of the negative electrode electrolyte to the positive electrode electrolyte; A step of issuing an operation command to an alarm device when the calculated value of the active material concentration ratio of the positive electrode electrolyte to the negative electrode electrolyte deviates from a set value of the active material concentration ratio of the positive electrode electrolyte to the negative electrode electrolyte by a predetermined value or more, or when the calculated value of the active material concentration ratio of the negative electrode electrolyte to the positive electrode electrolyte deviates from a set value of the active material concentration ratio of the negative electrode electrolyte to the positive electrode electrolyte by a predetermined value or more; The bipolar monitor cell is supplied with the positive electrode electrolyte and the negative electrode electrolyte common to the main cell; The positive electrode monitor cell is supplied with the positive electrode electrolyte common to the main cell without being supplied with the negative electrode electrolyte common to the main cell; The negative electrode monitor cell is supplied with the negative electrode electrolyte common to the main cell without being supplied with the positive electrode electrolyte common to the main cell; An operating method of a redox flow battery system.

14. The operating method of the redox flow battery system according to any one of claims 11 to 13, further comprising a step of stopping charging or discharging of the main cell after the step of issuing an operation command to the alarm device.