JP2006351346A - Redox flow battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a redox flow battery system capable of more accurately confirming whether or not an internal component of a cell such as a diaphragm is damaged, and an operation method of the system.
SOLUTION: A redox flow battery system comprising a main cell 1 in which positive and negative electrode electrolytes are circulated and charged / discharged with an external power system, and a monitor cell 2p connected to the main cell 1. . The main cell 1 is supplied with the positive electrode and the negative electrode electrolyte via the supply side transport paths 12 and 13, and the main cell 1 is discharged with the positive electrode and the negative electrode electrolyte via the discharge side transport paths 14 and 15. . The monitor cell 2p is supplied with the positive electrolyte supplied to the main cell 1 via the supply-side branch path 20 branched from the transport path 12, and the main cell via the discharge-side branch path 21 branched from the transport path 14. The positive electrode electrolyte discharged from 1 is supplied. The cell voltage of the monitor cell 2p is measured, and when the voltage drops, it is determined that the internal structural member is damaged.
[Selection] Figure 1

Description

  The present invention relates to a redox flow battery system in which an electrolytic solution is supplied to a cell to charge and discharge with an external power system, and an operation method of this system. In particular, the present invention relates to a redox flow battery system capable of more accurately confirming the presence or absence of breakage in internal structural members that are difficult to confirm from the exterior among the structural members constituting the cell, and an operating method of this system.

  Conventionally, it has been proposed to use a redox flow battery for load leveling applications, voltage sag and power failure countermeasure applications. A redox flow battery is a secondary battery that charges and discharges by supplying an electrolytic solution that causes a battery reaction to the cell, and a vanadium redox flow battery using a solution containing vanadium ions as the electrolytic solution is known. FIG. 4 is an explanatory view illustrating the operating principle of the vanadium redox flow battery system. The cell 100 includes a positive electrode cell 102 and a negative electrode cell 103 separated by a diaphragm 101, and each of the electrode cells 102 and 103 includes a positive electrode 104 and a negative electrode 105, respectively. The positive electrode electrolyte and negative electrode electrolyte stored in the tanks 106 and 107 are respectively supplied to the electrode cells 102 and 103 via the supply-side transport paths 108 and 109, and the positive electrode electrolyte and the negative electrode electrolyte discharged from the electrode cells 102 and 103 are respectively Then, they are returned to the tanks 106 and 107 via the discharge side transport paths 110 and 111. Pumps 112 and 113 are disposed in the supply side transport paths 108 and 109, respectively, and using the pumps 112 and 113, as described above, the electrolyte is circulated in the path of tank → supply side transport path → cell → discharge side transport path → tank. The cell 100 is connected to an external power system such as a power plant or a consumer via an AC / DC converter, and charges the power plant or the like as a charging power source and discharges the customer or the like as a discharge target.

  In the redox flow battery as described above, a configuration called a cell stack 200 in which a plurality of cells are stacked is usually used. FIG. 5 is a schematic configuration diagram of a cell stack. A configuration using a cell frame 120 as the cell is known. The cell frame 120 includes a bipolar plate 121 disposed so that the positive electrode 104 is in contact with one surface and the negative electrode 105 is in contact with the other surface, and a frame frame 122 formed on the outer periphery thereof. In the frame frame 122, there are formed liquid supply manifolds 123 and 124 for supplying each electrolyte solution to each electrode 104 and 105, and drainage manifolds 125 and 126 for discharging the electrolyte solution from each electrode 104 and 105. These manifolds 123, 124, 125 and 126 are Then, a plurality of cell frames 120 are stacked to constitute an electrolyte solution flow path, and are connected to a supply side transport path (see FIG. 4) and a discharge side transport path (same as above). In the frame frame 122, slits 127 and 128 through which the electrolyte flows are provided between the manifolds 123, 124, 125, and 126 and the bipolar plate 121, respectively. The cell stack 200 is configured by repeatedly stacking a cell frame 120, a positive electrode 104, a diaphragm 103, a negative electrode 105, a cell frame 120,.

  In addition, in a redox flow battery system, a voltmeter that measures the voltage of a cell, an ammeter that measures the current value during charge and discharge, a pressure gauge that measures the transport pressure of the electrolyte, a thermometer that measures the temperature of the electrolyte, etc. In many cases, the measuring instrument and a control device for controlling the measuring instrument are provided. The operator or the control device grasps the state of the system based on the measurement results of these measuring devices, and controls the voltage, current, pressure, temperature, and the like to be predetermined values and performs maintenance. In addition, some redox flow battery systems include a monitor cell in addition to a cell that charges and discharges with an external power system. The monitor cell detects voltage and uses this detection result for operation. And so on. Patent Document 1 discloses a redox flow battery system in which an auxiliary cell (monitor cell) that is not connected to an AC / DC converter is integrated with a main cell. In this system, a circuit voltage is measured in the auxiliary cell. The main cell output capacity is stabilized by determining whether to stop charging or discharging the main cell based on the circuit voltage. Patent Documents 2 and 3 disclose a redox flow battery system that includes a detection cell (monitor cell) that shares the main cell and an electrolyte solution separately from the main cell. In the system described in Patent Document 2, detection is performed. The battery cell is discharged at a low current for a certain period of time, and the battery capacity of the main cell is detected from the slope of this change in discharge voltage so that the cause of the decrease in battery capacity can be investigated. In the system described in Patent Document 3, the deterioration state of the electrode of the main cell can be grasped by analyzing the electrode of the monitor cell.

JP2003-317788 JP 2003-173812 A JP 2003-142141 A

  As described above, in the conventional redox flow battery system, voltage is measured by a cell or a monitor cell, and operation control or maintenance is performed based on the measurement result. However, in the conventional redox flow battery system, there is a problem that it is not possible to more reliably grasp whether or not the internal components of the cell such as the diaphragm and the bipolar plate are damaged.

  The diaphragm and the bipolar plate are often made of a softer material than the frame or the like, and may be torn. When these diaphragms and bipolar plates are damaged, positive and negative electrode electrolytes are mixed in the cell, causing problems such as self-discharge and excessive increase in the temperature in the cell. Therefore, it is desirable that the presence or absence of damage to the diaphragm or the bipolar plate can be detected as early as possible. However, since the diaphragm and bipolar plate are arranged between the frame frames and on the inner peripheral side of the outer peripheral edge of the frame frame, it is difficult to visually check the damage from the appearance of the cell (cell stack). is there.

  On the other hand, when the diaphragm or the bipolar plate is damaged as described above, changes such as an increase in temperature due to mixing of the electrolyte and a decrease in cell voltage due to self-discharge occur. Therefore, even in the conventional system, it is not possible to confirm the breakage of the diaphragm or the bipolar plate due to the temperature of the electrolyte or the cell voltage. However, since the rise in the temperature of the electrolyte and the decrease in the cell voltage are caused by causes other than the breakage of the diaphragm and the bipolar plate, it is difficult to accurately determine the presence or absence of breakage in these events.

  Further, when the conventional redox flow battery system includes a monitor cell separately from the main cell, both the positive electrode electrolyte and the negative electrode electrolyte that are the same as the main cell are supplied to the monitor cell. That is, the positive electrode electrolyte supplied to the main cell is also supplied as the positive electrode electrolyte in the monitor cell, and the negative electrode electrolyte supplied to the main cell is also supplied as the negative electrode electrolyte in the monitor cell. Therefore, in the monitor cell in which the positive electrode electrolyte and the negative electrode electrolyte are circulated and supplied in the same manner as the main cell, it is still difficult to accurately recognize the breakage of the diaphragm and the bipolar plate.

  Then, the main objective of this invention is to provide the redox flow battery system which can confirm the state of the internal structural member of a cell more exactly. Another object of the present invention is to provide a method for operating a redox flow battery system suitable for examining the presence / absence of breakage of internal components constituting the cell using the redox flow battery system.

  The present inventor has made various studies in order to more accurately confirm the state of internal structural members that are difficult to confirm from the appearance, such as a diaphragm and a bipolar plate, among the structural members of the cell, specifically, the presence or absence of breakage. As a result, when the positive and negative electrolytes are mixed or self-discharged in the cell due to damage to the diaphragm or the like, the charged or discharged electrolysis discharged from the cell after the battery reaction including self-discharge is performed It was noted that the ion concentration of the liquid changes from a predetermined concentration, in particular, the ion concentration in the charged state is lower than the predetermined concentration. In the redox flow battery system, the ion concentration of the charging electrolyte, the flow rate of the electrolyte supplied to the cell, and the charge / discharge current value of the electrolyte divided by the flow rate of the electrolyte (charge / discharge current value / flow rate), so-called conversion rate Are generally controlled so that the ion concentration, flow rate, and conversion rate fall within a set range. In a state where the components constituting the redox flow battery system are not abnormal or have not deteriorated over time (for example, at the initial stage of system construction), the above setting range can be sufficiently maintained and good. Charging / discharging can be performed in a state. Therefore, in the state where the above abnormality does not occur, the electrolyte supplied from the tank to the cell undergoes a battery reaction in the cell and changes to a charge / discharge ion concentration within a certain range based on the set conversion rate. In this state, it is discharged from the cell. That is, the difference between the ionic concentration of the electrolyte that is not performing the battery reaction supplied from the tank to the cell and the ionic concentration of the electrolytic solution that is discharged from the cell after the battery reaction is maintained in the cell is maintained within the set range. Is done. However, particularly when an abnormality such as breakage of the diaphragm or the bipolar plate occurs, the ion concentration of the electrolyte discharged from the cell changes due to self-discharge as described above. Therefore, the present inventor considered that the state of the diaphragm and the bipolar plate can be more accurately confirmed by examining the change in the ion concentration, and studied to detect the change in the ion concentration. And when the monitor cell to which the electrolyte solution before performing the battery reaction supplied to the cell and the electrolyte solution after performing the battery reaction discharged from the cell is constructed, the change in the ion concentration is It was found that the cell voltage was roughly proportional to the cell voltage.

Let us consider an electrolyte solution before the battery reaction is performed in the cell supplied to the cell and a monitor cell to which the electrolyte solution discharged from the cell after the battery reaction is performed in the cell.
Gas constant: R (J / K ・ mol) ≒ 8.3
Absolute temperature: T (K)
Faraday constant: F (c / mol) ≒ 9.6 × 10 ⁴
Total ion concentration (charge + discharge): n ₀ (mol / liter)
Ion concentration of the charging electrolyte before battery reaction takes place in the cell: n (mol / liter)
Difference between ion concentration of charging electrolyte before battery reaction in cell and ion concentration of charging electrolyte after battery reaction in cell: Δn (mol / liter)
And At this time, the ion concentration of the discharge electrolyte is expressed as n ₀ -n (mol / liter), and the ion concentration of the charge electrolyte after the battery reaction is expressed as n + Δn.
Ion concentration of the charging electrolyte: n (mol / liter) standard electromotive force E (n), Ion concentration of the charging electrolyte: n + Δn (mol / liter) standard electromotive force E (n + Δn), Assuming that the standard electromotive force when n = 0.5 × n ₀ is E ₀ , E (n) and E (n + Δn) are expressed by the following equations from the Nernst equation. The voltage ΔE of the monitor cell is expressed by ΔE = E (n + Δn) −E (n).

In the above equation, (R · T) / F is a constant (about 0.258 when T = 300K). From this approximation, it can be said that the cell voltage ΔE is substantially proportional to the difference Δn in ion concentration. Therefore, the present inventor uses the electrolyte before the battery reaction to be supplied to the main cell as the electrolyte of one electrode, and the electrolyte discharged from the main cell after the battery reaction as the other electrode. The monitor cell supplied as the electrolyte solution, that is, the monitor cell in which these electrolyte solutions function as the positive and negative electrolyte solutions, the cell voltage of this monitor cell is measured, and the ions of the charged electrolyte solution supplied to the main cell Δn (= I ₀ / (F · q), charging current value: I ₀ (A), electrolyte flow rate: q (liter / sec)) between the concentration and the ionic concentration of the charging electrolyte discharged from the cell) And the measured cell voltage ΔE were examined. Here, the conversion rate (χ = Δn / n) was obtained from the ion concentration (n) of the charging electrolyte supplied to the main cell and the difference Δn, and the relationship between the cell voltage and the conversion rate was examined. As a result, as shown in the graph of FIG. 3, it was confirmed that the cell voltage ΔE and the conversion rate χ are substantially proportional, that is, the cell voltage ΔE and the difference Δn are substantially proportional. Therefore, by constructing the monitor cell and confirming the change (increase / decrease) in the cell voltage of the monitor cell, it is possible to determine the change in the ion concentration, and from this result, more accurately determine the state of the diaphragm and the bipolar plate be able to. More specifically, when the diaphragm or the bipolar plate is damaged, the ion concentration is lowered, so that the cell voltage is lowered. Therefore, when the cell voltage decreases, it can be determined that the diaphragm or the bipolar plate is damaged. Based on this knowledge, the present invention provides that a monitor cell is provided that can more directly grasp the state of the internal components of the cell. Specifically, the present invention is a redox flow battery system including a main cell that is circulated and supplied with an electrolytic solution and charges and discharges with an external power system, and a monitor cell connected to the main cell. The most characteristic feature of the present invention is that, as an electrolytic solution that is circulated and supplied to the monitor cell, a supply-side electrolytic solution before the battery reaction is performed in the main cell and a battery reaction that is performed in the main cell The discharge side electrolyte solution is used. Hereinafter, the present invention will be described in more detail.

  As a typical configuration of the redox flow battery system, a cell, a tank for storing an electrolyte supplied to the cell or discharged from the cell, an electrolyte transportation path connecting between the cell and the tank, The structure provided with the pump provided in a conveyance path in order to circulate electrolyte solution to a cell is mentioned. An AC / DC converter is connected to the cell, and an external power system is connected via the AC / DC converter. Examples of the external power system include a power generation facility such as a power plant that serves as a charging power source that supplies power to the cell during charging, and an external load such as a consumer that is subject to discharge of the cell during discharge. Such a configuration may be used as a basic configuration of the redox flow battery system of the present invention. In addition, the electrolytic solution used in the system of the present invention is 1. Electromotive force is high, 2. Energy density is large, 3. Since the electrolytic solution is a single element system, the positive electrode electrolyte and the negative electrode electrolyte are mixed. A vanadium ion solution having many advantages such that it can be regenerated by charging is also preferred.

  The cell typically includes a positive electrode cell and a negative electrode cell separated by a diaphragm through which ions can pass. Each of the positive electrode cell and the negative electrode cell incorporates a positive electrode and a negative electrode. Such a cell can be configured by using a cell frame including a bipolar plate having a positive electrode on one surface and a negative electrode on the other surface and a frame frame provided on the outer periphery of the bipolar plate. Specifically, a cell is configured by sequentially stacking a cell frame, a positive electrode, a diaphragm, a negative electrode, and a cell frame. At this time, a positive electrode cell is composed of one surface of the cell frame (bipolar plate), the positive electrode and one surface of the diaphragm, and a negative electrode cell is composed of the other surface of the diaphragm, the negative electrode and the other surface of the cell frame (bipolar plate). The

  The diaphragm may be an ion exchange membrane that can transmit ions. Examples of each electrode include those made of carbon felt. Examples of the bipolar plate include those made of plastic carbon. The frame frame is made of an insulating material, for example, a resin such as vinyl chloride so that an accident such as a short circuit does not occur even when the electrolytic solution contacts. The frame frame passes through a supply manifold for supplying each electrode electrolyte from a tank for storing each electrode electrolyte to each electrode, a discharge manifold for discharging each electrode electrolyte from each electrode, and a supply manifold. In order to facilitate the transportation of the electrolytic solution to the electrode and to facilitate the transportation of the electrolytic solution from the electrode to the discharge manifold, there may be mentioned one provided with a slit provided between the manifold and the bipolar plate. The electrolytic solution transport path should be formed using a pipe (pipe) made of an insulating material, for example, a resin such as vinyl chloride, so that an accident such as a short circuit does not occur even when the electrolytic solution contacts. .

  The redox flow battery system of the present invention includes two types of cells having different purposes of use, specifically, a main cell and a monitor cell. The main cell is a cell that constitutes a battery body that is connected to a power plant that is a charging power source and a consumer that is a discharge target through an AC / DC converter, and is used for charging and discharging. Such a main cell may have a single cell structure including one cell having the above-described configuration, or may be used by constructing a stacked body (cell stack) in which a plurality of cells having the above-described configuration are stacked. Usually, the main cell is often used in a cell stack.

  On the other hand, the monitor cell is composed of cells having the above-described configuration, similar to the main cell, and is a test cell used to check the state of the main cell. Like the main cell, the monitor cell is connected to an AC / DC converter and connected to external power. It is not used to charge and discharge the system. In particular, in the present invention, the electrolyte supplied to the monitor cell is different from that of the main cell in order to more accurately confirm the soundness of the internal components of the main cell such as the diaphragm and the bipolar plate in the monitor cell.

Specifically, when a vanadium ion solution is used as the electrolytic solution, a commonly used positive electrode electrolyte and negative electrode electrolyte are supplied to the main cell. As a positive electrode electrolyte using a vanadium ion solution, a pentavalent vanadium ion solution having a high ion concentration of pentavalent vanadium ions (V ⁵⁺ ), and as a negative electrode electrolyte, divalent vanadium ions (V ²⁺ ) Generally, a divalent vanadium ion solution having a high ion concentration is used. Therefore, a pentavalent vanadium ion solution is supplied to the main cell as a positive electrode electrolyte, and a divalent vanadium ion solution is supplied as a negative electrode electrolyte.

On the other hand, a vanadium ion solution is used for the monitor cell in the system of the present invention as in the main cell, but only one of the electrolytes is used, and this electrolyte functions as a positive electrode and a negative electrode. When the monitor cell is provided in the conventional redox flow battery system, the electrolyte used as the positive electrode electrolyte and the negative electrode electrolyte in the main cell is also supplied as it is in the monitor cell. In other words, the monitor cell in the conventional system has the same configuration as the main cell in the flow mode of the electrolyte solution, and supplies the electrolyte solution used as the cathode electrolyte solution in the main cell to the monitor cell as the cathode electrolyte solution. The electrolyte used as the negative electrode electrolyte in the main cell is also supplied to the monitor cell as the negative electrode electrolyte. On the other hand, the monitor cell in the system of the present invention is configured to supply any one electrolyte solution in the main cell as the positive electrode side electrolyte solution and the negative electrode side electrolyte solution. Specifically, the monitor cell in the system of the present invention is a unipolar electrolyte supplied from the tank to the main cell, and the supply-side electrolyte before the battery reaction is performed in the main cell and the battery reaction in the main cell. The discharge-side electrolyte discharged from the main cell after the above is supplied as a positive-electrode-side electrolyte and a negative-electrode-side electrolyte. For example, a vanadium ion solution is used as a bipolar electrolyte supplied to the main cell, and a so-called general positive electrode electrolyte (pentavalent vanadium ion solution) is used as an electrolyte supplied to the monitor cell in the system of the present invention. A battery can be formed in the monitor cell by the liquid. In this case, the supply-side electrolyte solution in which the battery reaction is not performed by the main cell has a high ion concentration of pentavalent vanadium ions (V ⁵⁺ ), and thus functions as a positive electrode electrolyte in the monitor cell. After the reaction is performed, the discharge side electrolyte discharged from the main cell has a lower concentration of pentavalent vanadium ions (V ⁵⁺ ) than before being supplied to the main cell. Functions as a negative electrode electrolyte. In addition, a vanadium ion solution is used as a bipolar electrolyte supplied to the main cell, of which a so-called general negative electrode electrolyte (a divalent vanadium ion solution) is used as an electrolyte supplied to the monitor cell in the system of the present invention. It is also possible to form a battery in the monitor cell with the liquid. In this case, the supply-side electrolyte in which the battery reaction is not performed by the main cell has a high ion concentration of divalent vanadium ions (V ²⁺ ), and thus functions as a negative electrode electrolyte in the monitor cell. After the reaction is performed, the electrolyte on the discharge side discharged from the main cell has an electrolyte concentration of the positive electrode in the monitor cell because the ion concentration of divalent vanadium ions (V ²⁺ ) is lower than before supply. Function as.

  As described above, the present invention has a configuration in which an electrolytic solution that functions as a positive electrode and an electrolytic solution that functions as a negative electrode are prepared and supplied to a monitor cell by using an electrolytic solution that is used as a monopolar electrolytic solution in a main cell. In order to supply the supply-side electrolyte to the monitor cell, the supply-side transport path arranged between the tank and the main cell is branched, and some of the electrolyte supplied to the main cell is supplied to the monitor cell. It is mentioned that it is configured as described above. To supply the discharge-side electrolyte to the monitor cell, branch the discharge-side transport path arranged between the tank and the main cell, and some of the electrolyte discharged from the main cell will enter the monitor cell. It is mentioned that it is configured to be supplied. A separate pump may be provided in the electrolyte transport branch connected to the monitor cell to assist the circulation of the electrolyte in the monitor cell. Further, a valve may be provided in the transport branch path to adjust the transport pressure of the electrolytic solution. Specifically, the transportation pressure is reduced by increasing the amount of closing the valve or increasing the transportation pressure or increasing the amount of opening the valve. By opening and closing such a valve, the transport pressure before passing through the cell and the transport pressure after passing through the cell can be adjusted to be equal.

  Such a monitor cell may have a single cell structure or a cell stack. When the monitor cell has a single cell structure, the cell voltage (electromotive force) of the monitor cell described later may be too small to measure. At this time, the monitor cell is preferably a cell stack. The monitor cell only needs to be able to measure the cell voltage. When the monitor cell is a cell stack, the number of stacked cells may be less than that of the main cell, the same number of cells, or the single cell structure. It may be smaller than the main cell.

  In the present invention, one monitor cell or two monitor cells may be provided for one main cell. When one monitor cell is provided, any of the positive electrode electrolyte and the negative electrode electrolyte supplied to the main cell may be used as the electrolyte used for the supply side electrolyte solution and the discharge side electrolyte solution. When two monitor cells are provided, the positive electrolyte supplied to the main cell and the positive electrolyte discharged from the main cell are used as the supply-side electrolyte and the discharge-side electrolyte used in one monitor cell (first monitor cell), respectively. The negative electrode electrolyte supplied to the main cell and the negative electrode electrolyte discharged from the main cell may be used as the supply side electrolyte and the discharge side electrolyte used for the other monitor cell (second monitor cell), respectively.

  By constructing the system of the present invention comprising at least one monitor cell as described above, and further comprising a voltage measuring means for measuring the cell voltage of the monitor cell to measure the cell voltage, the measurement results indicate that the main cell diaphragm and The presence or absence of damage to the bipolar plate can be determined more accurately. Further, when the present invention system including two monitor cells is constructed, information on the positive electrode electrolyte and the negative electrode electrolyte supplied to the main cell, for example, the degree of increase in potential at each electrode can be obtained separately. This information can be used, for example, for adjusting the flow rate balance between the positive electrode electrolyte and the negative electrode electrolyte supplied to the main cell.

In the system of the present invention including the monitor cell, when checking the soundness of the internal components of the main cell such as the diaphragm and the bipolar plate, it can be easily confirmed by using a computer. Specifically, a computer capable of performing various processes such as storage, calculation, determination, signal transmission (reception and transmission), and a program having the following steps are input in advance to the computer. The following steps may be performed. In addition to a computer, a processing control device such as a sequencer (programmable logic controller) that can perform various processing means such as storage means, computing means, determination means, signal reception means, signal transmission means such as a computer may be used. Good.
1. Step of measuring the voltage of the monitor cell with the voltage measurement means attached to the monitor cell
2. A step of comparing the measured voltage with a preset value by means of comparison provided in the computer
3. A step of determining an abnormality of the internal component based on a comparison result between the measured voltage and the set value by a determination means included in the computer

  In performing the first step, a voltage measuring means is attached to the monitor cell. The measuring means and the computer are connected via a wiring for transmitting a measurement result (electric signal). Further, the computer is configured so that an electrical signal from the measuring means is input to the signal receiving means.

  In performing the second step, a setting value is input in advance to the storage means of the computer, and the comparison means of the computer uses the setting value called from the storage means and the signal (measurement voltage) acquired by the signal receiving means. Compare them.

  In performing the third step, the determination means determines that there is an abnormality in the internal component when the measurement voltage is smaller than the set value, and there is no abnormality in the internal component when the measurement voltage is equal to or greater than the set value. Make a decision. The determination result is displayed on, for example, a display means (monitor) included in the computer, and the operator can confirm the state of the internal component by confirming the determination result. It may be. In addition, if it is determined that there is an abnormality in the internal component, the computer will work out the abnormality of the internal component by making a warning sound or displaying a warning on the display means (monitor) included in the computer. You may make it tell to a person. By giving such a warning, the operator can surely grasp the abnormality of the internal component member earlier. When there is an abnormality in the internal components, charging / discharging of the main cell may be stopped, or the diaphragm or cell frame constituting the main cell may be replaced while the main cell is not charging / discharging.

  In the case of the system of the present invention having two monitor cells, it is preferable to make a determination based on two cell voltages obtained from both monitor cells. For example, when both cell voltages are equal to or higher than a set value, it may be determined that there is no abnormality in the internal components. If any one of the cell voltages is smaller than the set value, there may be an abnormality in the internal component, but the flow rate of the electrolyte solution supplied to the main cell is the same as that of the electrolyte solution of the other electrode. It is also conceivable that the flow rate is larger than the flow rate, that is, the flow rate of the electrolyte supplied to the main cell is unbalanced. When the flow rate of the electrolytic solution is too large, a sufficient battery reaction cannot be performed in the cell, and as a result, the cell voltage of the monitor cell may not be within a predetermined range. Therefore, in order to check whether the internal component member is abnormal or the flow rate is unbalanced, if any one of the cell voltages is smaller than the set value, the flow rate is adjusted after the determination, and then the cell voltage is measured, It is preferable to perform the determination again. As a result of the determination performed again, if both cell voltages are equal to or higher than the set value, it is determined that there is no abnormality in the internal component, and if any one of the cell voltages is smaller than the set value, it is determined that the internal component is abnormal. Good.

  When both cell voltages are smaller than the set value, it is considered that an abnormality has occurred in the internal component. Therefore, it may be determined that there is an abnormality, but it is also conceivable that the cell voltage of the monitor cell does not fall within a predetermined range because the flow rates of the electrolytes in both electrodes supplied to the main cell are both too large. Therefore, it is preferable to adjust the flow rate after the determination, and then perform the determination again after the determination, even when both the cell voltages are smaller than the set value as described above. As a result of the determination performed again, if both cell voltages are equal to or higher than the set value, it is determined that there is no abnormality in the internal component member, and if both cell voltages are smaller than the set value, it is preferable to determine that the internal component member is abnormal.

  The redox flow battery system of the present invention having the above configuration can more accurately confirm the state of internal components of the main cell such as a diaphragm and a bipolar plate that are difficult to visually confirm from the outside without disassembling the main cell. . Further, by applying the operation method of the present invention to such a redox flow battery system, it is possible to easily and more surely confirm whether or not the internal structural member is damaged.

Embodiments of the present invention will be described below.
FIG. 1 is a schematic configuration diagram of a redox flow battery system of the present invention. This redox flow battery system includes a main cell 1, a positive electrode electrolyte tank 10 for storing a positive electrode electrolyte supplied / discharged to the main cell 1, and a negative electrode for storing a negative electrode electrolyte supplied / discharged to / from the main cell 1. Electrolyte solution 11 is circulated and supplied to the main cell 1 and the supply side transport paths 12 and 13 and the discharge side transport paths 14 and 15 for connecting the main cell and the tanks 10 and 11 to transport the electrolyte solution. In order to do so, it comprises pumps 16 and 17 arranged in the supply side transport paths 12 and 13.

In this example, the main cell 1 is a stacked body (cell stack) in which a plurality of cells for redox flow batteries are stacked. The specific structure of the cell is the same as that shown in FIGS. 4 and 5, and a cell frame comprising a plastic carbon bipolar plate and a vinyl chloride frame frame provided on the outer periphery of the bipolar plate, made of carbon felt. A positive electrode, a diaphragm made of an ion exchange membrane, a negative electrode made of carbon felt, and a cell frame similar to the above are laminated in this order. The frame frame includes a supply manifold for supplying the electrolyte to the electrode, a discharge manifold for discharging the electrolyte from the electrode, and a slit provided between the bipolar plate and the manifold. The transport paths 12 to 15 are formed of vinyl chloride pipes. In this example, a pentavalent vanadium ion (V ⁵⁺ ) solution was used as the positive electrode electrolyte, and a divalent vanadium ion (V ²⁺ ) solution was used as the negative electrode electrolyte. The main cell 1 is connected to an AC / DC converter (see Fig. 4), and an external power system such as a charging power source such as a power plant or a discharge target such as a consumer is connected via the AC / DC converter. The external power system is charged / discharged.

  The redox flow battery system includes monitor cells 2p and 2n in addition to the main cell 1. These monitor cells 2p and 2n are different from conventional systems in that the pentavalent vanadium ion solution used as the positive electrode electrolyte in the main cell 1 and the divalent vanadium used as the negative electrode electrolyte in the main cell 1. Similarly to the main cell 1, the ionic solution is not used as a positive electrode electrolyte or a negative electrode electrolyte. The monitor cell 2p is supplied with only the electrolyte used as the positive electrode electrolyte in the main cell 1 to form a battery, and the monitor cell 2n is supplied only with the electrolyte used as the negative electrode electrolyte in the main cell 1. Form a battery. More specifically, the monitor cell 2p (first monitor cell) is a positive electrode electrolyte (supply-side electrolyte) before the battery reaction is performed in the main cell 1, and after the battery reaction is performed in the main cell 1. The positive electrode electrolyte discharged from the main cell 1 (discharge-side electrolyte) is supplied. The monitor cell 2n (second monitor cell) is discharged from the main cell 1 after the battery reaction is performed in the main cell 1 and the negative electrode electrolyte (supply-side electrolyte) before the battery reaction is performed in the main cell 1. The negative electrode electrolyte solution (discharge side electrolyte solution) is supplied. As described above, each of the monitor cells 2p and 2n is configured to be supplied with only one of the electrolytes supplied to the main cell 1. In the monitor cell 2p, the positive electrode electrolyte supplied from the tank 10 and before the battery reaction is performed in the main cell 1 is used as the positive electrode side electrolyte, and the positive electrode electrolyte after the battery reaction is performed in the main cell 1 is the negative electrode. A battery is formed as the side electrolyte. In the monitor cell 2n, the negative electrode electrolyte supplied from the tank 11 and before the battery reaction is performed in the main cell 1 is used as the negative electrode side electrolyte, and the negative electrode electrolyte after the battery reaction is performed in the main cell 1 is used as the positive electrode. A battery is formed as the side electrolyte.

  The basic configuration of the monitor cells 2p and 2n is the same as that of the main cell 1, and only the number of stacked layers of the main cell 1 and the cells is different. In this example, the number of stacked monitor cells 2p and 2n is made smaller than the number of stacked main cells 1. Further, the positive electrode electrolyte supplied from the tank 10 to the main cell 1 via the supply-side transport path 12, that is, the positive electrode electrolyte not performing the battery reaction in the main cell 1 is supplied to the positive electrode side of the monitor cell 2p. A branch path (supply side branch path 20) is provided in the supply side transport path 12. The cathode electrolyte discharged from the main cell 1 to the tank 10 through the discharge side transport path 14, that is, the cathode electrolyte that has undergone the battery reaction in the main cell 1 is supplied to the anode side of the monitor cell 2p. A branch path (discharge side branch path 21) is provided in the transport path 14. In addition, a discharge path 22 is connected to the discharge-side transport path 14 so that the electrolyte discharged from the monitor cell 2p is returned to the tank 10. Similarly, the negative electrode electrolyte supplied from the tank 11 to the main cell 1 via the supply side transport path 13, that is, the negative electrode electrolyte not performing the battery reaction in the main cell 1 is supplied to the negative electrode side of the monitor cell 2n. The supply side transport path 13 is provided with a branch path (supply side branch path 23). The negative electrode electrolyte discharged from the main cell 1 through the discharge side transport path 15 to the tank 11, that is, the negative electrode electrolyte subjected to the battery reaction in the main cell 1 is supplied to the positive electrode side of the monitor cell 2n. A branch path (discharge side branch path 24) is provided in the transport path 15. Further, a discharge path 25 is connected to the discharge side transport path 15 so that the electrolyte discharged from the monitor cell 2n is returned to the tank 11. The supply side branch paths 20 and 23, the discharge side branch paths 21 and 24, and the discharge paths 22 and 25 were formed by pipes made of vinyl chloride. In this example, the pumps 26 and 27 are provided in the discharge side branch passages 21 and 24 so that the electrolytic solution can be circulated and supplied more reliably to the monitor cells 2n and 2p. However, this pump may not be arranged. Instead of this pump, a valve may be provided so that the transport pressure can be adjusted by the opening / closing amount of the valve. Further, a pump may be provided in the supply side branch paths 20 and 23, or a valve may be provided instead of the pump.

  These monitor cells 2n, 2p are connected to voltage measuring means 30, 31 so that the cell voltage can be measured. A computer 40 capable of various processes such as storage, calculation, determination, and signal transmission is connected to the voltage measurement means 30 and 31 by wiring, and measurement results (electrical signals) from the voltage measurement means 30 and 31 are connected. Is transmitted to the computer 40. The computer 40 determines the soundness of the internal components using the transmitted cell voltage (measurement result) based on a program described later. In this example, as the computer 40, a commercially available computer including storage means, calculation means, determination means, signal reception means, signal transmission means, and display means (monitor) 41 is used. In this example, the pumps 16, 17, 26, and 27 are also connected to the computer 40, and the control (flow rate adjustment) of the pumps 16, 17, 26, and 27 is performed by the computer 40. Therefore, in addition to the above, the computer 40 used was provided with control means, timer means, and command means.

  As described above, the redox flow battery system of the present invention including the monitor cell to which the electrolytic solution before the battery reaction is performed in the main cell and the electrolytic solution after the battery reaction is performed in the main cell is the monitor cell. The cell voltage can be measured, and the state of the internal components of the cell such as the diaphragm and the bipolar plate can be confirmed more accurately by this cell voltage. That is, in the system of the present invention, it is possible to confirm the soundness of the internal components of the main cell that are difficult to confirm from the appearance without disassembling the main cell. In particular, by using a computer, it is possible to easily check whether or not the internal structural member is damaged.

  In the redox flow battery system of the present invention, the procedure for determining the presence or absence of damage to the internal components will be specifically described. FIG. 2 is a flowchart showing an operation procedure of the operation method of the redox flow battery system of the present invention. In this example, the cell voltage of the monitor cell is constantly measured during normal operation in which the main cell charges and discharges and is input to the computer.

In the operation method of the present invention, first, the cell voltage V _{p of} the monitor cell 2p (see FIG. 1) to which the positive electrode electrolyte is supplied and the monitor cell 2n to which the negative electrode electrolyte is supplied (see FIG. 1) by the voltage measuring means provided in each monitor cell. the cell voltage V _n of the reference) was measured, the measurement result (electric signal) to be inputted to the signal receiving means of the computer (step S1). The storage means of the computer temporarily stores the acquired cell voltages V _p and V _n . Further, the set value X of the cell voltage of the monitor cell is input in advance to the storage means. The set value X may be appropriately determined based on the ion concentration of the charging electrolyte set in the main cell, the charging current value, the flow rate of the electrolyte, the conversion rate, and the like.

Next, the comparison means of the computer calls the set value X stored in the storage means, and compares the magnitude relationship between the cell voltages V _p and V _n and the set value X (step S2). Specifically, the comparison unit checks whether the cell voltages V _p and V _n are smaller than the set value X, that is, whether V _p <X and V _n <X.

If V _p <X and V _n <X, that is, if both cell voltages are lower than the set value, it may be determined that there is an abnormality, but the cause of both cell voltages being lower than the set value The following two can be considered. One is that the bipolar plate and the diaphragm are damaged, and the positive and negative electrolytes supplied to the main cell are mixed with each other or self-discharge occurs, resulting in a low conversion rate and cell voltage. Is thought to have declined. The other is considered to be that the cell voltage was lowered because the flow rates of both the positive and negative electrode electrolytes supplied to the main cell were large, and sufficient battery reaction was not performed in the main cell. Therefore, in this example, the flow rate of the electrolyte solution in both electrodes is adjusted in order to determine whether the cause of the decrease in the cell voltage is due to damage to the internal components or the flow rate of the electrolyte solution (step S3). Specifically, the control means of the computer issues an adjustment command to both pumps used to circulate the positive and negative electrolytes supplied to the main cell, and reduces the flow rates of both electrolytes supplied to the main cell. Like that. Then, after a predetermined time has elapsed, the cell voltages V _p ′ and V _n ′ of the monitor cells 2p and 2n are measured, and the measurement results (electric signals) are input to the signal receiving means of the computer (step S4). Note that the degree of decreasing the flow rate and the time until the cell voltage is measured again after adjusting the flow rate are set in advance and input to the computer. The computer calls the degree of flow rate adjustment from the storage means and instructs the pump. Further, the computer counts the time after the flow rate adjustment by the built-in timer means, and obtains the cell voltage after a predetermined time. The same applies to steps S11 to S13, which will be described later, with regard to the adjustment degree and time of these flow rates.

Next, the comparison means of the computer calls the set value X stored in the storage means, and compares the magnitude relationship between the obtained cell voltages V _p ′, V _n ′ and the set value X (step S5). Specifically, the comparison means checks whether V _p ′ ≧ X and V _n ′ ≧ X. From this result, the determination means determines the cause of the cell voltage becoming lower than the set value. When V _p ′ ≧ X and V _n ′ ≧ X, that is, when the cell voltage reaches a predetermined range by improving the electrolyte flow rate, both cell voltages acquired in step S1 become smaller than the set value. This is presumably because the flow rate of the electrolyte in the main cell was not appropriate. That is, it is presumed that there is no problem such as damage to the internal components of the main cell. Therefore, in this case, the determination unit determines that there is no abnormality (step S6). After the determination, the computer repeats the procedure from the voltage acquisition to the determination. On the other hand, when V _p '≧ X and V _n ' ≧ X, V _p '<X and V _n '<X, V _p '<X and V _n ' ≧ X, V _p '≧ X and V _n '< One of X. At this time, even if the flow rate of the electrolyte is improved with respect to the main cell, the cell voltage of at least one of the monitor cells is smaller than the set value. Presumed to have occurred. Therefore, in this case, the determination unit determines that there is an abnormality (step S7). In this example, the determination result is displayed on the monitor of the computer, and the operator can easily confirm the determination result by viewing the monitor. In addition, when it is determined that there is an abnormality, it is desirable to replace the diaphragm or the bipolar plate. Therefore, it is preferable to disassemble the main cell and replace the diaphragm and the bipolar plate while waiting for the main cell not to charge / discharge, or by stopping the charge / discharge of the main cell.

On the other hand, if V _p <X and V _n <X, it is determined that there is no abnormality, and the procedure from voltage acquisition to determination may be repeated, but in this example, V _p <X and V _n <Not X, 1. V _p <X and V _n ≧ X, 2. V _p ≧ X and V _n <X, 3. V _p ≧ X and V _n ≧ X It was. Therefore, when V _p <X and V _n <X, V _p <X and V _n ≧ X, V _p ≧ X and V _n <X, V _p ≧ X and V _n ≧ X are determined. Determine which case applies. Specifically, the determination unit determines whether V _p ≧ X and V _n ≧ X (step S8).

When V _p ≧ X and V _n ≧ X, there is no abnormality such as mixing of the positive electrode electrolyte and negative electrode electrolyte supplied to the main cell or occurrence of self-discharge, and the main cell is good. It is considered to be in a state. That is, it is considered that the bipolar plate and the diaphragm are not damaged. Further, it is considered that both the positive electrode electrolyte and the negative electrode electrolyte supplied to the main cell have an appropriate flow rate. Therefore, the determination means determines that there is no abnormality (step S9). In this case, the computer repeats the procedure from voltage acquisition to determination.

On the other hand, when V _p ≧ X and V _n ≧ X, either V _p <X and V _n ≧ X, or V _p ≧ X and V _n <X. Therefore, the determination means of the computer determines whether V _p <X or V _n <X. In this example, the determination unit determines whether V _p <X (step S10). When V _p <X (and V _n ≧ X), there are two possible causes for the cell voltage V _p of the monitor cell 2p being decreased. One is that the negative electrode electrolyte supplied to the main cell is mixed with the positive electrode electrolyte because the bipolar plate and the diaphragm are damaged, that is, the electrolyte is mixed from the negative electrode side to the positive electrode side, It is considered that the cell voltage has decreased. The other is that the flow rate of the positive electrode electrolyte supplied to the main cell is large and the battery voltage of the monitor cell 2p to which the positive electrode electrolyte is supplied in the main cell due to insufficient battery reaction in the main cell. Is thought to have declined. Therefore, in this example, the flow rate adjustment of the positive electrode electrolyte supplied to the main cell is determined in order to determine whether the cause of the decrease in the cell voltage is due to the damage of the internal components or the flow rate of the positive electrode electrolyte in the main cell. Is performed (step S11). Specifically, the control means of the computer issues an adjustment command to a pump used for circulation of the positive electrode electrolyte supplied to the main cell so as to reduce the flow rate of the positive electrode electrolyte supplied to the main cell.

On the other hand, in the case of V _n <X (and V _p ≧ X), there are two possible causes for the cell voltage V _n of the monitor cell 2n being reduced as described above. That is, one is that the positive electrode electrolyte supplied to the main cell is mixed with the negative electrode electrolyte because the bipolar plate and the diaphragm are damaged, that is, the electrolyte is mixed from the positive electrode side to the negative electrode side. The other is that the flow rate of the negative electrode electrolyte supplied to the main cell is large and sufficient battery reaction is not performed in the main cell, so that the cell of the monitor cell 2n to which the negative electrode electrolyte in the main cell is supplied The voltage is thought to have dropped. Therefore, in this example, in the same manner as described above, in order to determine whether the cause of the decrease in the cell voltage is due to damage to internal components or due to the flow rate of the negative electrode electrolyte in the main cell, the negative electrode electrolysis supplied to the main cell is determined. The liquid flow rate is adjusted (step S12). Specifically, the control means of the computer issues an adjustment command to a pump used for circulation of the negative electrode electrolyte supplied to the main cell so as to reduce the flow rate of the negative electrode electrolyte supplied to the main cell.

Adjust the positive electrode electrolyte flow rate or negative electrode electrolyte flow rate, measure the cell voltages V _p ", V _n " of the monitor cells 2p, 2n after a predetermined time, and receive the measurement results (electrical signals) as computer signals It is made to input into a means (step S13). Next, the comparison means of the computer calls the set value X stored in the storage means, and compares the obtained cell voltages V _p ″, V _n ″ with the set value X (Step S14). Specifically, the comparison means checks whether V _p "≧ X and V _n " ≧ X. From this result, the determination means determines the cause of the cell voltage of the monitor cell 2p or the monitor cell 2n being smaller than the set value. When V _p "≧ X and V _n " ≧ X, that is, when the cell voltage reaches a predetermined range by improving the electrolyte flow rate, the cell voltage V _p or V _n acquired in step S1 is the set value. It is presumed that the flow rate of the positive electrode electrolyte or the negative electrode electrolyte was not appropriate in the main cell. That is, it is presumed that there is no problem such as damage to the internal components of the main cell. Therefore, in this case, the determination unit determines that there is no abnormality (step S15). After the determination, the computer repeats the procedure from the voltage acquisition to the determination. On the other hand, when V _p ″ ≧ X and V _n ″ ≧ X, V _p ″ <X and V _n ″ ≧ X or V _p ″ ≧ X and V _n ″ <X. That is, even if the flow rate of the cathode electrolyte or anode electrolyte is improved with respect to the main cell, the cell voltage of the monitor cell is smaller than the set value, so that the internal components of the main cell are damaged. Is presumed to have occurred. Therefore, in this case, the determination unit determines that there is an abnormality (step S16). At this time, it is advisable to disassemble the main cell and replace the diaphragm and the bipolar plate in the same manner as described above.

  By providing two monitor cells in this way, not only the state of the internal components of the cell is grasped, but also the unbalance between the flow rate of the positive electrode electrolyte supplied to the main cell and the flow rate of the negative electrode electrolyte is reduced, The main cell can be controlled to a better state. In addition, such control can make it difficult to cause problems such as breakage of cell constituent members.

  In addition, in this example, although it was set as the structure provided with two monitor cells, the state of the internal structural member of a cell can fully be grasped | ascertained only by one.

  The redox flow battery system of the present invention can be suitably used in load leveling applications and voltage sag / blackout applications. In addition, the operation method of the redox flow battery system of the present invention is suitable for the operation of the above system, and by applying the operation method of the present invention, the state of the internal components of the cell can be grasped more accurately.

It is a schematic block diagram of this invention redox flow battery system. It is a flowchart which shows the operation procedure of the operating method of this invention redox flow battery system. It is a graph which shows the relationship between the cell voltage of the monitor cell to which the supply side electrolyte solution supplied to a main cell and the discharge side electrolyte solution discharged | emitted from the main cell are circulated and the conversion rate of the main cell. It is explanatory drawing which shows the operating principle of a vanadium redox flow battery system. It is a schematic block diagram of the cell stack utilized for a redox flow battery system.

Explanation of symbols

1 Main cell 2p, 2n Monitor cell
10 Cathode electrolyte tank 11 Anode electrolyte tank 12,13 Supply-side transport path
14,15 Discharge side transport path 16,17,26,27 Pump
20,23 Supply side branch path 21,24 Discharge side branch path 22,25 Discharge path
30,31 Voltage measurement means 40 Computer 41 Monitor
100 cells 101 Diaphragm 102 Positive electrode cell 103 Negative electrode cell 104 Positive electrode
105 Negative electrode 106 Positive electrode electrolyte tank 107 Negative electrode electrolyte tank
108,109 Supply side transport path 110,111 Discharge side transport path 112,113 Pump
120 cell frame 121 bipolar plate 122 frame frame
123,124 Supply manifold 125,126 Drain manifold
127,128 slit 200 cell stack

Claims (4)

A main cell in which electrolyte is circulated and charged / discharged with an external power system;
A monitor cell connected to the main cell;
The monitor cell is circulated and supplied with a supply-side electrolyte before the battery reaction is performed in the main cell and a discharge-side electrolyte after the battery reaction is performed in the main cell. Flow battery system. The main cell is circulated and supplied with a positive electrode electrolyte and a negative electrode electrolyte,
A first monitor cell in which a supply side electrolyte solution and a discharge side electrolyte solution made of a positive electrode electrolyte used for the main cell are circulated and supplied;
2. The redox flow battery system according to claim 1, comprising a supply-side electrolyte solution made of a negative electrode electrolyte used for the main cell and a second monitor cell to which the discharge-side electrolyte solution is circulated and supplied.   3. The redox flow battery system according to claim 2, wherein the cathode electrolyte is a pentavalent vanadium ion solution, and the anode electrolyte is a divalent vanadium ion solution. A method of operating the redox flow battery system according to claim 1,
A method for operating a redox flow battery system, comprising: causing a computer to perform the following steps to check whether or not an internal component member constituting a main cell is damaged.
1. Step of measuring the voltage of the monitor cell with the voltage measurement means attached to the monitor cell
2. A step of comparing the measured voltage with a preset value by means of comparison means provided in the computer
3. A step of determining an abnormality of the internal component based on a comparison result between the measured voltage and the set value by a determination means included in the computer

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