Redox flow battery system

Abstract

To provide a redox flow battery system capable of improving the efficiency thereof.SOLUTION: A redox flow battery system includes a charging section 2, a discharging section 3 and a storage section 4 storing an electrolyte. The charging section includes at least one charging cell stack and a charging side power conditioner. The discharging section includes: at least one discharging cell stack where at least two discharging cells of a plurality of discharging cells are electrically connected in series; and a discharging side power conditioner electrically connected to the at least one discharging cell stack. The charging side power conditioner has such characteristics that a conversion efficiency of the charging side power conditioner increases as a charging voltage increases, within an acceptable voltage range of the charging side power conditioner, and the discharging side power conditioner has such characteristics that a conversion efficiency of the discharging side power conditioner increases as a discharging voltage decreases, within an acceptable voltage range of the discharging side power conditioner.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to redox flow battery systems. [Background technology]

[0002] A redox flow battery is composed of a cell and a tank for storing the electrolyte that flows through the cell, and charging and discharging are performed by circulating the electrolyte between the cell and the tank using a pump. Redox flow batteries are suitable for storing high output and large amounts of power because the output and power storage capacity can be individually designed by changing the design of the cell and tank. Furthermore, by providing a charging cell and a discharging cell, as in the systems described in Patent Documents 1 and 2, charging and discharging can be performed simultaneously. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2014-505976 [Patent Document 2] Japanese Patent Application Publication No. 2023-50337 Summary of the Invention [Problem to be solved by the invention]

[0004] However, Patent Documents 1 and 2 do not describe any technical ideas for realizing a highly efficient system that takes into account large-scale systems (capable of storing electricity on a kWh or MWh scale).

[0005] In view of the above, an object of at least one embodiment of the present disclosure is to provide a redox flow battery system that can improve efficiency. [Means for solving the problem]

[0006] In order to achieve the above object, the redox flow battery system according to the present disclosure is a redox flow battery system comprising: a charging unit including a plurality of charge cells; a discharging unit including a plurality of discharge cells and discharging power charged by the charging unit; and a storage unit for storing an electrolyte flowing through the plurality of charge cells and the plurality of discharge cells, wherein the charging unit comprises at least one charge cell stack configured by electrically connecting at least two of the plurality of charge cells in series, and a charge-side power conditioner electrically connected to the at least one charge cell stack; and the discharging unit comprises a storage unit for storing an electrolyte flowing through the plurality of discharge cells. The charging system comprises at least one discharge cell stack formed by electrically connecting at least two of the cells in series, and a discharge-side power conditioner electrically connected to the at least one discharge cell stack, wherein the charge-side power conditioner has a characteristic that the conversion efficiency of the charge-side power conditioner increases as the charge voltage increases within the range of the acceptable voltage of the charge-side power conditioner, and the discharge-side power conditioner has a characteristic that the conversion efficiency of the discharge-side power conditioner increases as the discharge voltage decreases within the range of the acceptable voltage of the discharge-side power conditioner. [Effects of the Invention]

[0007] According to the redox flow battery system of the present disclosure, the efficiency of the charging operation is increased by using a charging-side power conditioner having a characteristic that the conversion efficiency of the charging-side power conditioner increases as the charging voltage increases within the range of the voltage accepted by the charging-side power conditioner, and the efficiency of the discharging operation is increased by using a discharging-side power conditioner having a characteristic that the conversion efficiency of the discharging-side power conditioner increases as the discharge voltage decreases within the range of the voltage accepted by the discharging-side power conditioner, thereby increasing the efficiency of the redox flow battery system. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating the configuration of a redox flow battery system according to a first embodiment of the present disclosure. [Figure 2] 1A and 1B are schematic diagrams illustrating the configurations of a charge cell stack and a discharge cell stack of a redox flow battery system according to a first embodiment of the present disclosure. [Figure 3] 4 is a schematic graph showing PCS characteristics of a charging-side PCS used in the redox flow battery system according to the first embodiment of the present disclosure. [Figure 4] 3 is a schematic graph showing PCS characteristics of a discharge-side PCS used in the redox flow battery system according to the first embodiment of the present disclosure. [Figure 5] FIG. 10 is a schematic diagram illustrating the configuration of a redox flow battery system according to a second embodiment of the present disclosure, showing paths through which a first electrolytic solution and a second electrolytic solution circulate. [Figure 6] FIG. 10 is a schematic diagram illustrating the configuration of a redox flow battery system according to a third embodiment of the present disclosure, showing paths through which a first electrolytic solution and a second electrolytic solution circulate. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a redox flow battery system according to an embodiment of the present disclosure will be described with reference to the drawings. The embodiment described below shows one aspect of the present disclosure, but does not limit the present disclosure and can be modified as desired within the scope of the technical concept of the present disclosure.

[0010] (Embodiment 1) <Configuration of redox flow battery system according to embodiment 1> As shown in FIG. 1 , a redox flow battery system 1 according to a first embodiment of the present disclosure includes a charging unit 2, a discharging unit 3, and a storage unit 4. The charging unit 2 has a plurality of charging cells 20. Of the plurality of charging cells 20, at least two charging cells 20 are electrically connected in series to form a charging cell stack 21. The charging unit 2 includes at least one charging cell stack 21 and a charging-side power conditioner (PCS) 22 to which the charging cell stack 21 is electrically connected (connected by a dashed dotted line in FIG. 1 ). When the charging unit 2 includes a plurality of charging cell stacks 21, each charging cell stack 21 is connected in parallel to the charging-side PCS 22. The charging-side PCS 22 is electrically connected to a power source 5. The configuration of the power source 5 is not particularly limited, and may be, for example, a gas engine, a wind power generation facility, a solar cell, or the like.

[0011] The discharge unit 3 has a plurality of discharge cells 30. Of the plurality of discharge cells 30, at least two discharge cells 30 are electrically connected in series to form a discharge cell stack 31. The discharge unit 3 includes at least one discharge cell stack 31 and a discharge-side power conditioner (PCS) 32 to which the discharge cell stack 31 is electrically connected (connected by a dashed-dotted line in FIG. 1). When the discharge unit 3 has a plurality of discharge cell stacks 31, each discharge cell stack 31 is connected in parallel to the discharge-side PCS 32. The discharge-side PCS 32 is electrically connected to the load 6 (connected by a dashed-dotted line in FIG. 1).

[0012] The storage unit 4 includes a first electrolyte tank 40 for storing the first electrolyte, a second electrolyte tank 41 for storing the second electrolyte, a charge-side first electrolyte circulation line 42 through which the first electrolyte circulates between the first electrolyte tank 40 and each charge cell stack 21 of the charge unit 2, a discharge-side first electrolyte circulation line 43 through which the first electrolyte circulates between the first electrolyte tank 40 and each discharge cell stack 31 of the discharge unit 3, and a charge-side second electrolyte circulation line 44 through which the second electrolyte circulates between the second electrolyte tank 41 and each charge cell stack 21 of the charge unit 2. 44, a discharge-side second electrolyte circulation line 45 through which the second electrolyte circulates between the second electrolyte tank 41 and each discharge cell stack 31 of the discharge unit 3, a charge-side first electrolyte circulation pump 46 provided in the charge-side first electrolyte circulation line 42, a discharge-side first electrolyte circulation pump 47 provided in the discharge-side first electrolyte circulation line 43, a charge-side second electrolyte circulation pump 48 provided in the charge-side second electrolyte circulation line 44, and a discharge-side second electrolyte circulation pump 49 provided in the discharge-side second electrolyte circulation line 45.

[0013] Each of the first and second electrolytic solutions is prepared by dissolving an active material in an aqueous solution containing a supporting electrolyte. This aqueous solution can be an alkaline aqueous solution containing potassium hydroxide, sodium hydroxide, or the like as a supporting electrolyte, a neutral aqueous solution containing potassium chloride, sodium chloride, or the like as a supporting electrolyte, or an acidic aqueous solution containing hydrogen chloride or sulfuric acid as a supporting electrolyte. The active material dissolved in each of the first and second electrolytic solutions can be a metal ion such as vanadium, a metal complex, air, a halogen, or an organic molecule such as quinone or hydroquinone.

[0014] Because the configurations of the charge cell 20 and the discharge cell 30 are basically the same, the common configuration between them is shown in Figure 2, and the configurations of both will be described based on Figure 2. The charge cell 20 has a charge-side diaphragm 23, a first electrode 26 provided in a first chamber 24 that is one of the chambers separated by the charge-side diaphragm 23, and a second electrode 27 provided in a second chamber 25 that is the other of the chambers separated by the charge-side diaphragm 23. The discharge cell 30 has a discharge-side diaphragm 33, a positive electrode 36 provided in a positive chamber 34 that is one of the chambers separated by the discharge-side diaphragm 33, and a negative electrode 37 provided in a negative chamber 35 that is the other of the chambers separated by the discharge-side diaphragm 33.

[0015] The first electrodes 26 and second electrodes 27 provided in each charge cell 20 in the charge cell stack 21 are electrically connected in series (connected by dashed dotted lines in FIG. 2) and electrically connected to the charge side PCS 22 (connected by dashed dotted lines in FIG. 2), thereby electrically connecting the charge cell stack 21 to the charge side PCS 22. The positive electrodes 36 and negative electrodes 37 provided in each discharge cell 30 in the discharge cell stack 31 are electrically connected in series (connected by dashed dotted lines in FIG. 2) and electrically connected to the discharge side PCS 32 (connected by dashed dotted lines in FIG. 2), thereby electrically connecting the discharge cell stack 31 to the discharge side PCS 32.

[0016] In each of the charge cell stack 21 and the discharge cell stack 31, the first chamber 24 of each charge cell 20 and the positive electrode chamber 34 of each discharge cell 30 are connected in series in the flow direction of the first electrolyte (connected by dashed lines in Figure 2), and the second chamber 25 of each charge cell 20 and the negative electrode chamber 35 of each discharge cell 30 are connected in series in the flow direction of the second electrolyte (connected by dashed lines in Figure 2). With this configuration, the charging cell stack 21 has a circulation path for the first electrolytic solution formed by connecting each of the multiple first chambers 24 in series, and a circulation path for the second electrolytic solution formed by connecting each of the multiple second chambers 25 in series, and the inlets through which the first electrolytic solution and the second electrolytic solution flow into each circulation path form the inlet 51 for the first electrolytic solution and the inlet 55 for the second electrolytic solution in the charging cell stack 21, and the outlets through which the first electrolytic solution and the second electrolytic solution flow out from each circulation path form the outlet 53 for the first electrolytic solution and the outlet 57 for the second electrolytic solution in the charging cell stack 21. Furthermore, the discharge cell stack 31 has a circulation path for the first electrolytic solution formed by connecting each of the multiple positive electrode chambers 34 in series, and a circulation path for the second electrolytic solution formed by connecting each of the multiple negative electrode chambers 35 in series, and the inlets through which the first electrolytic solution and the second electrolytic solution flow into each circulation path form the inlet 52 for the first electrolytic solution and the inlet 56 for the second electrolytic solution in the discharge cell stack 31, and the outlets through which the first electrolytic solution and the second electrolytic solution flow out from each circulation path form the outlet 54 for the first electrolytic solution and the outlet 58 for the second electrolytic solution in the discharge cell stack 31.

[0017] A charge-side first electrolyte circulation line 42 is connected to the inlet 51 and outlet 53 for the first electrolyte in the charge cell stack 21, respectively, and a charge-side second electrolyte circulation line 44 is connected to the inlet 55 and outlet 57 for the second electrolyte in the charge cell stack 21, respectively. Furthermore, a discharge-side first electrolyte circulation line 43 is connected to the inlet 52 and outlet 54 for the first electrolyte in the discharge cell stack 31, respectively, and a discharge-side second electrolyte circulation line 45 is connected to the inlet 56 and outlet 58 for the second electrolyte in the discharge cell stack 31, respectively.

[0018] The characteristics required for increasing the efficiency of the redox flow battery system 1, which performs charging and discharging operations, are different for the charging-side PCS 22 and the discharging-side PCS 32. Using PCS characteristics, which are expressed as the relationship between voltage and PCS conversion efficiency, as shown in FIG. 3, the charging-side PCS 22 has a characteristic in which the conversion efficiency of the charging-side PCS 22 increases as the charging voltage increases within the range of the voltage accepted by the charging-side PCS 22. The discharging-side PCS 32 has a characteristic in which the conversion efficiency of the discharging-side PCS 32 increases as the discharge voltage decreases within the range of the voltage accepted by the discharging-side PCS 32, as shown in FIG. 4. For example, the charging-side PCS 22 having such PCS characteristics may be SUNNY BOY 3300TL HC, and the discharging-side PCS 32 having such PCS characteristics may be SUNNY BOY 1100 / 1700. Both are available from SMA Solar Technology GmbH, Germany.

[0019] In the discharge cell stack 31, by electrically connecting in series the number of discharge cells 30 such that the discharge voltage of the discharge cell stack 31 falls within the range of the acceptable voltage of the discharge-side PCS 32, and in the charge cell stack 21, by electrically connecting in series the number of charge cells 20 such that the charge voltage of the charge cell stack 21 falls within the range of the acceptable voltage of the charge-side PCS 22, a DC-DC converter is not required in each of the charge-side PCS 22 and the discharge-side PCS 32. This reduces the cost of the redox flow battery system 1 and also increases the efficiency of the charge and discharge operations of the redox flow battery system 1.

[0020] <Operation of the redox flow battery system according to the first embodiment> Next, the operation of the redox flow battery system 1 according to the first embodiment of the present disclosure will be described. First, the discharge operation of the redox flow battery system 1 will be described. As shown in Fig. 1 , when the discharge-side first electrolyte circulation pump 47 is started, the first electrolyte circulates between the first electrolyte tank 40 and each discharge cell stack 31 of the discharge unit 3 via the discharge-side first electrolyte circulation line 43. When the discharge-side second electrolyte circulation pump 49 is started, the second electrolyte circulates between the second electrolyte tank 41 and each discharge cell stack 31 of the discharge unit 3 via the discharge-side second electrolyte circulation line 45.

[0021] 2, the first electrolyte flowing through the discharge-side first electrolyte circulation line 43 flows into the discharge cell stack 31 via the inlet 52, flows sequentially through each positive electrode chamber 34 of each discharge cell 30 constituting the discharge cell stack 31, and then flows out of the discharge cell stack 31 via the outlet 54. The second electrolyte flowing through the discharge-side second electrolyte circulation line 45 flows into the discharge cell stack 31 via the inlet 56, flows sequentially through each negative electrode chamber 35 of each discharge cell 30 constituting the discharge cell stack 31, and then flows out of the discharge cell stack 31 via the outlet 58.

[0022] When the first electrolytic solution flows through each positive electrode chamber 34, the active material contained in the first electrolytic solution is reduced. On the other hand, when the second electrolytic solution flows through each negative electrode chamber 35, the active material contained in the second electrolytic solution is oxidized. That is, the negative electrode 37 receives electrons released from the active material contained in the second electrolytic solution, and the active material contained in the first electrolytic solution receives electrons that have moved from the negative electrode 37 to the positive electrode 36, causing a direct current to flow from the positive electrode 36 to the negative electrode 37. This direct current is converted to an alternating current by the discharge-side PCS 32, and power is supplied to and consumed by the load 6 (see FIG. 1).

[0023] Next, a description will be given of the charging operation of the redox flow battery system 1. As shown in Fig. 1, when the charging-side first electrolyte circulation pump 46 is started, the first electrolyte circulates between the first electrolyte tank 40 and each charging cell stack 21 of the charging unit 2 via the charging-side first electrolyte circulation line 42. When the charging-side second electrolyte circulation pump 48 is started, the second electrolyte circulates between the second electrolyte tank 41 and each charging cell stack 21 of the charging unit 2 via the charging-side second electrolyte circulation line 44.

[0024] 2, the first electrolyte flowing through the charge-side first electrolyte circulation line 42 flows into the charge cell stack 21 via inlet 51, flows sequentially through each of the first chambers 24 of each of the charge cells 20 that make up the charge cell stack 21, and then flows out of the charge cell stack 21 via outlet 53. The second electrolyte flowing through the charge-side second electrolyte circulation line 44 flows into the charge cell stack 21 via inlet 55, flows sequentially through each of the second chambers 25 of each of the charge cells 20 that make up the charge cell stack 21, and then flows out of the charge cell stack 21 via outlet 57.

[0025] An AC current from the power source 5 (see FIG. 1 ) is converted to a DC current in the charge-side PCS 22, and a current flows between the first electrode 26 and the second electrode 27. When the first electrolytic solution flows through each of the first chambers 24, the active material contained in the first electrolytic solution is oxidized. On the other hand, when the second electrolytic solution flows through each of the second chambers 25, the active material contained in the second electrolytic solution is reduced. As a result, the active materials contained in the first electrolytic solution and the second electrolytic solution become usable in the discharge operation of the redox flow battery system 1.

[0026] The redox flow battery system 1 can perform discharging and charging operations separately, but can also simultaneously circulate the first and second electrolytic solutions between the first and second electrolytic solution tanks 40 and 41, respectively, and each charging cell stack 21 in the charging unit 2 using the charging-side first electrolytic solution circulation pump 46 and the charging-side second electrolytic solution circulation pump 48, and circulate the first and second electrolytic solutions between the first and second electrolytic solution tanks 40 and 41, respectively, and each discharging cell stack 31 in the discharging unit 3 using the discharging-side first electrolytic solution circulation pump 47 and the discharging-side second electrolytic solution circulation pump 49. This allows for discharging operations to be performed while charging operations are being performed.

[0027] According to the redox flow battery system 1 of the first embodiment of the present disclosure, by using a charge-side PCS22 having a characteristic that the conversion efficiency of the charge-side PCS22 increases as the charging voltage increases within the range of the voltage accepted by the charge-side PCS22, the efficiency of the charging operation is increased, and by using a discharge-side PCS32 having a characteristic that the conversion efficiency of the discharge-side PCS32 increases as the discharge voltage decreases within the range of the voltage accepted by the discharge-side PCS32, the efficiency of the discharging operation is increased, and the efficiency of the redox flow battery system 1 can be increased.

[0028] (Embodiment 2) Next, a redox flow battery system according to embodiment 2 will be described. The redox flow battery system according to embodiment 2 has fewer circulation pumps for the first electrolytic solution and fewer circulation pumps for the second electrolytic solution than embodiment 1. In embodiment 2, the same components as those in embodiment 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0029] <Configuration of redox flow battery system according to embodiment 2> Fig. 5 shows paths through which the first electrolytic solution and the second electrolytic solution circulate in a redox flow battery system 1 according to Embodiment 2 of the present disclosure. While Fig. 5 illustrates a configuration in which the charge cell stack 21 and the discharge cell stack 31 are configured by one charge cell 20 and one discharge cell 30, respectively, the present disclosure is not limited to this configuration. As in Embodiment 1, the charge cell stack 21 may be configured by electrically connecting a plurality of charge cells 20 in series, and the discharge cell stack 31 may be configured by electrically connecting a plurality of discharge cells 30 in series. In the former configuration, Embodiment 2 is a configuration that does not assume the configuration of Embodiment 1, and in the latter configuration, Embodiment 2 is a configuration that assumes the configuration of Embodiment 1.

[0030] In the storage unit 4, a first outlet side line 70 and a second outlet side line 73 are connected to the first electrolyte tank 40 and the second electrolyte tank 41, respectively, through which the first electrolyte solution and the second electrolyte solution flowing out from the first electrolyte tank 40 and the second electrolyte tank 41, respectively. A first charge side branch line 71 and a first discharge side branch line 72 branch out from the downstream end of the first outlet side line, and are connected to the inlet 51 for the first electrolyte solution in the charge cell stack 21 and the inlet 55 for the first electrolyte solution in the discharge cell stack 31, respectively. A second charge side branch line 74 and a second discharge side branch line 75 branch out from the downstream end of the second outlet side line 73, and are connected to the inlet 52 for the second electrolyte solution in the charge cell stack 21 and the inlet 56 for the second electrolyte solution in the discharge cell stack 31, respectively.

[0031] A charge-side first electrolyte outflow line 80 and a discharge-side first electrolyte outflow line 81, through which the first electrolyte flowing out from the charge cell stack 21 and the discharge cell stack 31, respectively, are connected to outlets 53 and 54, respectively. A charge-side second electrolyte outflow line 82 and a discharge-side second electrolyte outflow line 83, through which the second electrolyte flowing out from the charge cell stack 21 and the discharge cell stack 31, respectively, are connected to outlets 57 and 58, respectively. The downstream end of the charge-side first electrolyte outflow line 80 and the downstream end of the discharge-side first electrolyte outflow line 81 join, and a first electrolyte return line 84 is provided connecting this junction to the first electrolyte tank 40. The downstream end of the charge-side second electrolyte outflow line 82 and the downstream end of the discharge-side second electrolyte outflow line 83 join, and a second electrolyte return line 85 is provided connecting this junction to the second electrolyte tank 41.

[0032] A first pump 60 is provided in the first outlet side line 70. A second pump 61 is provided in the second outlet side line 73. A first switching device 62 is provided to switch the first outlet side line 70 so that it communicates with either the first charge side branch line 71 or the first discharge side branch line 72. A second switching device 63 is provided to switch the second outlet side line 73 so that it communicates with either the second charge side branch line 74 or the second discharge side branch line 75. The configurations of the first switching device 62 and the second switching device 63 are not particularly limited. For example, the first switching device 62 may be a three-way valve 62a provided at a branch point where the first charge side branch line 71 and the first discharge side branch line 72 branch from the downstream end of the first outlet side line 70, and the second switching device 63 may be a three-way valve 63a provided at a branch point where the second charge side branch line 74 and the second discharge side branch line 75 branch from the downstream end of the second outlet side line 73. When the first switching device 62 and the second switching device 63 are equipped with three-way valves 62a and 63a, respectively, the first switching device 62 preferably further comprises a three-way valve 62b provided at the junction of the downstream end of the charge-side first electrolyte solution outflow line 80 and the downstream end of the discharge-side first electrolyte solution outflow line 81, and the second switching device 63 preferably further comprises a three-way valve 63b provided at the junction of the downstream end of the charge-side second electrolyte solution outflow line 82 and the downstream end of the discharge-side second electrolyte solution outflow line 83. The other configurations are the same as those in the first embodiment.

[0033] <Operation of the redox flow battery system according to the second embodiment> Since the operation of Embodiment 2 differs from that of Embodiment 1 in some respects with respect to the flow of the electrolytes (first electrolyte solution and second electrolyte solution), only those differences will be described in detail below. In the discharge operation of the redox flow battery system 1, the three-way valve 62a communicates between the first outlet-side line 70 and the first discharge-side branch line 72, the three-way valve 62b communicates between the discharge-side first electrolyte solution outflow line 81 and the first electrolyte solution return line 84, the three-way valve 63a communicates between the second outlet-side line 73 and the second discharge-side branch line 75, and the three-way valve 63b communicates between the discharge-side second electrolyte solution outflow line 83 and the second electrolyte solution return line 85.

[0034] When the first pump 60 is started in this state, the first electrolyte solution flowing out of the first electrolyte solution tank 40 flows sequentially through the first outlet side line 70 and the first discharge side branch line 72, and then flows into the discharge cell stack 31 via the inlet 52. Within the discharge cell stack 31, the first electrolyte solution flows through each positive electrode chamber 34 in each discharge cell 30, then flows out of the discharge cell stack 31 via the outlet 54, and then flows sequentially through the discharge side first electrolyte solution outflow line 81 and the first electrolyte solution return line 84, and then flows into the first electrolyte solution tank 40. In this way, the first electrolyte solution circulates between the first electrolyte solution tank 40 and the discharge cell stack 31.

[0035] Furthermore, when the second pump 61 is started in this state, the second electrolyte solution flowing out of the second electrolyte solution tank 41 flows sequentially through the second outlet side line 73 and the second discharge side branch line 75, and then flows into the discharge cell stack 31 via the inlet 56. Within the discharge cell stack 31, the second electrolyte solution flows through each negative electrode chamber 35 in each discharge cell 30, then flows out of the discharge cell stack 31 via the outlet 58, and then flows sequentially through the discharge side second electrolyte solution outflow line 83 and the second electrolyte solution return line 85, and then flows into the second electrolyte solution tank 41. In this way, the second electrolyte solution circulates between the second electrolyte solution tank 41 and the discharge cell stack 31.

[0036] As in the first embodiment, when the first electrolytic solution flows through each positive electrode chamber 34, the active material contained in the first electrolytic solution is reduced, and when the second electrolytic solution flows through each negative electrode chamber 35, the active material contained in the second electrolytic solution is oxidized, thereby causing a direct current to flow from the positive electrode 36 to the negative electrode 37.

[0037] In the charging operation of the redox flow battery system 1, the three-way valve 62a connects the first outlet side line 70 to the first charging side branch line 71, the three-way valve 62b connects the charging side first electrolyte outflow line 80 to the first electrolyte return line 84, the three-way valve 63a connects the second outlet side line 73 to the second charging side branch line 74, and the three-way valve 63b connects the charging side second electrolyte outflow line 82 to the second electrolyte return line 85.

[0038] When the first pump 60 is started in this state, the first electrolyte solution flowing out of the first electrolyte solution tank 40 flows sequentially through the first outlet line 70 and the first charge-side branch line 71, and enters the charge cell stack 21 via the inlet 51. Within the charge cell stack 21, it flows through each first chamber 24 in each charge cell 20, then flows out of the charge cell stack 21 via the outlet 53, flows sequentially through the charge-side first electrolyte solution outflow line 80 and the first electrolyte solution return line 84, and enters the first electrolyte solution tank 40. In this way, the first electrolyte solution circulates between the first electrolyte solution tank 40 and the charge cell stack 21.

[0039] Furthermore, when the second pump 61 is started in this state, the second electrolyte solution flowing out of the second electrolyte solution tank 41 flows sequentially through the second outlet side line 73 and the second charge side branch line 74, and enters the charge cell stack 21 via the inlet 55. Within the charge cell stack 21, it flows through each second chamber 25 in each charge cell 20, then flows out of the charge cell stack 21 via the outlet 57, flows sequentially through the charge side second electrolyte solution outflow line 82 and the second electrolyte solution return line 85, and enters the second electrolyte solution tank 41. In this way, the second electrolyte solution circulates between the second electrolyte solution tank 41 and the charge cell stack 21.

[0040] As in the first embodiment, when the first electrolytic solution flows through each first chamber 24, the active material contained in the first electrolytic solution is oxidized, and when the second electrolytic solution flows through each second chamber 25, the active material contained in the second electrolytic solution is reduced, so that the active materials contained in the first electrolytic solution and the second electrolytic solution become usable for the discharge operation of the redox flow battery system 1.

[0041] In the second embodiment, compared to the first embodiment in which four pumps were required for circulating the first electrolytic solution and the second electrolytic solution, the number can be reduced to two, the first pump 60 and the second pump 61, thereby reducing the cost of the redox flow battery system 1.

[0042] (Embodiment 3) Next, a redox flow battery system according to embodiment 3 will be described. The redox flow battery system according to embodiment 3 is different from embodiment 2 in that it is capable of simultaneously performing charging and discharging operations. In embodiment 3, the same components as those in embodiment 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0043] <Configuration of redox flow battery system according to embodiment 3> 6 , the redox flow battery system 1 according to the third embodiment of the present disclosure is provided with a first circulation line 90 through which the first electrolyte solution circulates between the first chamber 24 and the positive electrode chamber 34, and a second circulation line 91 through which the second electrolyte solution circulates between the second chamber 25 and the negative electrode chamber 35. The first circulation line 90 includes a line 90a connecting an outlet 53 for the first electrolyte solution in the charge cell stack 21 and an inlet 52 for the first electrolyte solution in the discharge cell stack 31, and a line 90b connecting an outlet 54 for the first electrolyte solution in the discharge cell stack 31 and an inlet 51 for the first electrolyte solution in the charge cell stack 21. The second circulation line 91 includes a line 91a connecting the outlet 57 for the second electrolyte in the charging cell stack 21 and the inlet 56 for the second electrolyte in the discharging cell stack 31, and a line 91b connecting the outlet 58 for the second electrolyte in the discharging cell stack 31 and the inlet 55 for the second electrolyte in the charging cell stack 21.

[0044] A first circulation pump 92 and a first on-off valve 93 are provided in a line 90a of the first circulation line 90. A second circulation pump 94 and a second on-off valve 95 are provided in a line 91a of the second circulation line 91. A third on-off valve 96, a fourth on-off valve 97, a fifth on-off valve 98, and a sixth on-off valve 99 may be provided in the first charge-side branch line 71, the first discharge-side branch line 72, the first electrolyte solution outflow line 80, and the discharge-side first electrolyte solution outflow line 81, respectively. The other configurations are the same as those in the second embodiment.

[0045] <Operation of the redox flow battery system according to the third embodiment> Insofar as the discharging operation and the charging operation are performed separately in Embodiment 3, the operation of Embodiment 3 is the same as that of Embodiment 2. The difference between the operation of Embodiment 3 and that of Embodiment 2 is that the charging operation and the discharging operation can be performed simultaneously in Embodiment 3, and therefore, only the operation when the charging operation and the discharging operation are performed simultaneously will be described in detail below. Such an operation is, for example, an emergency evacuation operation when the state of charge of the redox flow battery system 1 decreases during the discharging operation, making charging necessary, but it is still necessary to supply power to the load 6 (see FIG. 1) for even a relatively short time.

[0046] In such a case, the first circulation pump 92 and the second circulation pump 94 are started, and the first on-off valve 93 and the second on-off valve 95 are opened. Thereafter, the first pump 60 and the second pump 61 are stopped. After this, preferably, the third on-off valve 96, the fourth on-off valve 97, the fifth on-off valve 98, and the sixth on-off valve 99 are closed. As a result, the first electrolytic solution circulates between the first chamber 24 and the positive electrode chamber 34 via the first circulation line 90, and the second electrolytic solution circulates between the second chamber 25 and the negative electrode chamber 35 via the second circulation line 91.

[0047] When the first electrolytic solution and the second electrolytic solution flow through the first chamber 24 and the second chamber 25, respectively, the first electrolytic solution and the second electrolytic solution become usable for the discharge operation of the redox flow battery system 1, based on the principle described in the first embodiment. The first electrolytic solution and the second electrolytic solution flowing out of the first chamber 24 and the second chamber 25 flow into the positive electrode chamber 34 and the negative electrode chamber 35, respectively, via the lines 90a and 91a. When the first electrolytic solution and the second electrolytic solution flowing through the positive electrode chamber 34 and the negative electrode chamber 35, respectively, a direct current flows from the positive electrode 36 to the negative electrode 37, based on the principle described in the first embodiment. The first electrolytic solution and the second electrolytic solution flowing out of the positive electrode chamber 34 and the negative electrode chamber 35 again flow into the first chamber 24 and the second chamber 25 via the lines 90b and 91b, respectively. By repeating this operation, charging and discharging operations can be performed simultaneously in an emergency.

[0048] The contents described in each of the above embodiments can be understood, for example, as follows.

[0049] [1] A redox flow battery system according to one embodiment includes: a charging section (2) including a plurality of charging cells (20); a discharge unit (3) including a plurality of discharge cells (30) for discharging the power charged by the charge unit (2); a reservoir (4) for storing an electrolyte flowing through each of the plurality of charge cells (20) and the plurality of discharge cells (30); A redox flow battery system (1) comprising: The charging section (2) At least one charge cell stack (21) configured by electrically connecting at least two of the plurality of charge cells (20) in series; a charging-side power conditioner (22) electrically connected to the at least one charging cell stack (21); Equipped with The discharge section (3) is At least one discharge cell stack (31) configured by electrically connecting at least two of the plurality of discharge cells (30) in series; a discharge-side power conditioner (32) electrically connected to the at least one discharge cell stack (31); Equipped with The charging side power conditioner (22) has a characteristic that the conversion efficiency of the charging side power conditioner (22) increases as the charging voltage increases within a range of the acceptable voltage of the charging side power conditioner (22), and the discharging side power conditioner (32) has a characteristic that the conversion efficiency of the discharging side power conditioner (32) increases as the discharging voltage decreases within a range of the acceptable voltage of the discharging side power conditioner (32).

[0050] According to the redox flow battery system of the present disclosure, the efficiency of the charging operation is increased by using a charging-side power conditioner having a characteristic that the conversion efficiency of the charging-side power conditioner increases as the charging voltage increases within the range of the voltage accepted by the charging-side power conditioner, and the efficiency of the discharging operation is increased by using a discharging-side power conditioner having a characteristic that the conversion efficiency of the discharging-side power conditioner decreases as the discharge voltage increases within the range of the voltage accepted by the discharging-side power conditioner, thereby increasing the efficiency of the discharging operation, thereby making it possible to increase the efficiency of the redox flow battery system.

[0051] [2] A redox flow battery system according to another embodiment is the redox flow battery system according to [1], The at least one discharge cell stack (31) is configured by electrically connecting in series the number of discharge cells (30) such that the discharge voltage of the at least one discharge cell stack (31) is within the range of the accepted voltage of the discharge side power conditioner (32), and the at least one charge cell stack (21) is configured by electrically connecting in series the number of charge cells (20) such that the charge voltage of the at least one charge cell stack (21) is within the range of the accepted voltage of the charge side power conditioner (22).

[0052] With this configuration, a DC-DC converter is not required in either the charging side power conditioner or the discharging side power conditioner, which reduces the cost of the redox flow battery system and increases the efficiency of the charging and discharging operations of the redox flow battery system.

[0053] [3] A redox flow battery system according to yet another embodiment is the redox flow battery system according to [1] or [2], the electrolytic solution includes a first electrolytic solution and a second electrolytic solution, The charging section (2) a first electrolyte tank (40) configured to store the first electrolyte flowing through each of the first chambers (24) that are one of the chambers separated by a charge-side diaphragm (23) in each of the plurality of charge cells (20) and each of the positive electrode chambers (34) that are one of the chambers separated by a discharge-side diaphragm (33) in each of the plurality of discharge cells (30); a second electrolyte tank (41) configured to store the second electrolyte flowing through each of the second chambers (25) that are the other chambers separated by the charge-side diaphragm (23) in each of the plurality of charge cells (20) and each of the negative electrode chambers (35) that are the other chambers separated by the discharge-side diaphragm (33) in each of the plurality of discharge cells (30); a first outlet line (70) through which the first electrolytic solution flowing out of the first electrolytic solution tank (40) flows; a first charge-side branch line (71) and a first discharge-side branch line (72) branching from a downstream end of the first outlet-side line (70) and connected to the first chamber (24) and the positive electrode chamber (34), respectively; a first pump (60) provided in the first outlet line (70); a first switching device (62) that switches the first outlet side line (70) so that the first outlet side line (70) is connected to either the first charge side branch line (71) or the first discharge side branch line (72); a second outlet line (73) through which the second electrolytic solution flowing out of the second electrolytic solution tank (41) flows; a second charge side branch line (74) and a second discharge side branch line (75) branching from a downstream end of the second outlet side line (73) and connected to the second chamber (25) and the negative electrode chamber (35), respectively; a second pump (61) provided in the second outlet line (73); a second switching device (63) that switches the second outlet side line (73) so that the second outlet side line (73) communicates with either the second charge side branch line (74) or the second discharge side branch line (75); Equipped with.

[0054] According to this configuration, compared to the redox flow battery system [1] or [2], the number of pumps for circulating the first electrolytic solution and the second electrolytic solution can be reduced to two, the first pump and the second pump, thereby reducing the cost of the redox flow battery system.

[0055] [4] A redox flow battery system according to yet another embodiment is the redox flow battery system according to [3], a first circulation line (90) through which the first electrolytic solution circulates between the first chamber (24) and the positive electrode chamber (34); a first circulation pump (92) provided in the first circulation line (90); a first on-off valve (93) provided in the first circulation line (90); a second circulation line (91) through which the second electrolytic solution circulates between the second chamber (25) and the negative electrode chamber (35); a second circulation pump (94) provided in the second circulation line (91); a second on-off valve (95) provided in the second circulation line (91); Equipped with.

[0056] According to this configuration, the redox flow battery system [3] can simultaneously perform charging and discharging operations. [Explanation of symbols]

[0057] 1. Redox flow battery system 2 Live parts 3 Discharge section 4. Storage section 20 charging cells 21 Charging cell stack 22 Charging side PCS 23 Charging side diaphragm 24 Room 1 25 Room 2 30 discharge cells 31 Discharge cell stack 32 Discharge side PCS 33 Discharge side diaphragm 34 Positive electrode chamber 35 Anode chamber 40 First electrolyte tank 41 Second electrolyte tank 60 First Pump 61 Second Pump 62 First Switching Device 63 Second switching device 70 Exit 1 Line 71 First charging side branch line 72 First discharge side branch line 73 Second Exit Line 74 Second charging side branch line 75 Second discharge side branch line 90 First Circulation Line 91 Second Circulation Line 92 First circulation pump 93 First shut-off valve 94 Second circulation pump 95 Second shut-off valve

Claims

1. a charging unit including a plurality of charging cells; a discharge unit including a plurality of discharge cells and discharging the power charged by the charge unit; a reservoir that stores an electrolyte that flows through each of the plurality of charge cells and the plurality of discharge cells; A redox flow battery system comprising: The charging unit is At least one charge cell stack configured by electrically connecting at least two of the plurality of charge cells in series; a charging-side power conditioner electrically connected to the at least one charging cell stack; Equipped with The discharge unit is At least one discharge cell stack configured by electrically connecting at least two of the plurality of discharge cells in series; a discharge-side power conditioner electrically connected to the at least one discharge cell stack; Equipped with the charging side power conditioner has a characteristic that its conversion efficiency increases as the charging voltage increases within a range of a voltage accepted by the charging side power conditioner, and the discharging side power conditioner has a characteristic that its conversion efficiency increases as the discharging voltage decreases within a range of a voltage accepted by the discharging side power conditioner.

2. 2. The redox flow battery system according to claim 1, wherein the at least one discharge cell stack is configured by electrically connecting in series a number of the discharge cells such that the discharge voltage of the at least one discharge cell stack is within the range of the acceptable voltage of the discharge-side power conditioner, and the at least one charge cell stack is configured by electrically connecting in series a number of the charge cells such that the charge voltage of the at least one charge cell stack is within the range of the acceptable voltage of the charge-side power conditioner.

3. the electrolytic solution includes a first electrolytic solution and a second electrolytic solution, The charging unit is a first electrolyte tank configured to store the first electrolyte that flows through each of the first chambers that are one of the chambers separated by a charge-side diaphragm in each of the plurality of charge cells and each of the positive electrode chambers that are one of the chambers separated by a discharge-side diaphragm in each of the plurality of discharge cells; a second electrolyte tank configured to store the second electrolyte that flows through each of the second chambers that are the other chambers separated by the charge-side diaphragm in each of the plurality of charge cells and each of the negative electrode chambers that are the other chambers separated by the discharge-side diaphragm in each of the plurality of discharge cells; a first outlet line through which the first electrolytic solution flowing out of the first electrolytic solution tank flows; a first charge-side branch line and a first discharge-side branch line branching from a downstream end of the first outlet-side line and connected to the first chamber and the positive electrode chamber, respectively; a first pump provided in the first outlet side line; a first switching device that switches the first outlet side line so that the first outlet side line communicates with either the first charge side branch line or the first discharge side branch line; a second outlet line through which the second electrolytic solution flowing out of the second electrolytic solution tank flows; a second charge side branch line and a second discharge side branch line branching from a downstream end of the second outlet side line and connected to the second chamber and the negative electrode chamber, respectively; a second pump provided in the second outlet side line; a second switching device that switches the second outlet side line so that the second outlet side line communicates with either the second charge side branch line or the second discharge side branch line; The redox flow battery system according to claim 1 or 2, comprising:

4. a first circulation line through which the first electrolytic solution circulates between the first chamber and the positive electrode chamber; a first circulation pump provided in the first circulation line; a first on-off valve provided in the first circulation line; a second circulation line through which the second electrolytic solution circulates between the second chamber and the negative electrode chamber; a second circulation pump provided in the second circulation line; a second on-off valve provided in the second circulation line; The redox flow battery system of claim 3 , comprising:

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