Redox flow battery and power supply system equipped with the redox flow battery

Abstract

To provide a redox flow cell which can perform electric discharge while reducing loss and a power supply system including the redox flow cell.SOLUTION: A redox flow cell includes: at least one cell which has a first chamber and a second chamber which are partitioned by a membrane; a first electrolyte circulation device which circulates first electrolyte to the first chamber; and a second electrolyte circulation device which circulates second electrolyte to the second chamber. At least one of the first electrolyte circulation device and the second electrolyte circulation device has a high order electrolyte tank provided at a higher position than the cell, an electrolyte circulation path communicating the high order electrolyte tank with the first chamber or the second chamber, and an electrolyte outflow path for flowing out the first electrolyte or the second electrolyte flowed into the first chamber or the second chamber from the high order electrolyte tank, from the first chamber or the second chamber, and is configured such that the first electrolyte or the second electrolyte flows into the first chamber or the second chamber from the high order electrolyte tank through the electrolyte circulation path by a water head difference between a liquid level of the first electrolyte or the second electrolyte within the high order electrolyte tank and the cell.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a redox flow battery and a power supply system including the redox flow battery. [Background technology]

[0002] A redox flow battery is a secondary battery that uses a pump to circulate an electrolyte between an electrolyte tank and a cell, and charges and discharges the cell through an oxidation-reduction reaction. A redox flow battery is a system that stores electrical energy in an electrolyte, and the range of charge that can be stored varies depending on the charge storage rate of the electrolyte and the flow rate of the electrolyte inside the cell. This is because the concentration overpotential of the electrolyte is strongly affected by factors such as the charge storage rate and flow rate, and energy loss increases when the battery is operated in a region where the concentration overpotential is high, i.e., in a region where resistance is high. Patent Document 1 describes a redox flow battery that allows control of the pump flow rate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6399361 Summary of the Invention [Problem to be solved by the invention]

[0004] However, increasing the electrolyte flow rate to increase the electrolyte flow rate inside the cell increases the pump's power consumption, resulting in a decrease in the overall output of the redox flow battery. Furthermore, as the charge / discharge output increases and the current increases, the required flow rate (electrolyte flow rate) also increases. In the future, if the proportion of solar-generated electricity used increases in order to reduce carbon dioxide emissions, a sudden drop in output at sunset is likely. To compensate for such output fluctuations with a redox flow battery, the electrolyte flow rate must be set to the value required for maximum discharge output. This means that when the redox flow battery's discharge output is low, the electrolyte flows at a rate greater than the rate required to suppress concentration overvoltage, resulting in unnecessary losses in the pump's power consumption. This leads to issues with compensating for the sudden drop in output at sunset, such as poor responsiveness.

[0005] In view of the above circumstances, an object of at least one embodiment of the present disclosure is to provide a redox flow battery that can discharge while reducing losses, and a power supply system including the redox flow battery. [Means for solving the problem]

[0006] In order to achieve the above object, the redox flow battery according to the present disclosure includes at least one cell having a first chamber and a second chamber separated by a diaphragm, a first electrolyte solution distribution device that distributes a first electrolyte solution through the first chamber, and a second electrolyte solution distribution device that distributes a second electrolyte solution through the second chamber, wherein at least one of the first electrolyte solution distribution device and the second electrolyte solution distribution device includes a high-level electrolyte tank provided at a position higher than the at least one cell, an electrolyte solution distribution path that connects the high-level electrolyte tank with an inlet of the first chamber or the second chamber, an electrolyte solution outflow path that is connected to an outlet of the first chamber or the second chamber, and an electrolyte solution outlet path that is connected to the high-level electrolyte tank. and a lower-level electrolyte tank connected to the electrolyte outflow path at a position lower than the electrolyte tank, wherein the first electrolytic solution or the second electrolytic solution flows from the higher-level electrolyte tank through the electrolyte flow path into the first chamber or the second chamber due to a head difference between a liquid level of the first electrolytic solution or the second electrolytic solution in the higher-level electrolyte tank and the at least one cell, and at least one of the first electrolytic solution flow device and the second electrolytic solution flow device comprises an electrolyte inflow path connecting the lower-level electrolyte tank and the inlet of the first chamber or the second chamber, and a circulation pump provided in the electrolyte inflow path. an electrolyte transfer path that connects the lower level electrolyte tank and the higher level electrolyte tank; and a booster pump provided in the electrolyte transfer path. Equipped with. [Effects of the Invention]

[0007] According to the redox flow battery of the present disclosure, the first electrolytic solution or the second electrolytic solution is supplied from the higher-level electrolyte tank to at least one of the first and second chambers of the cell by using the hydraulic head difference between the higher-level electrolyte tank and the cell. This eliminates loss due to the power consumption of the pump compared to when the first electrolytic solution or the second electrolytic solution is supplied to the first or second chamber using a pump, and therefore enables discharge while reducing loss. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating the configuration of a redox flow battery according to a first embodiment of the present disclosure. [Figure 2] FIG. 1 is a schematic diagram illustrating the configuration of a redox flow battery according to a second embodiment of the present disclosure. [Figure 3]FIG. 1 is a schematic diagram illustrating the configuration of a redox flow battery according to a third embodiment of the present disclosure. [Figure 4] FIG. 1 is a schematic diagram illustrating the configuration of a redox flow battery according to a fourth embodiment of the present disclosure. [Figure 5] FIG. 10 is a schematic diagram illustrating the configuration of a power supply system according to a fifth embodiment of the present disclosure. [Figure 6] FIG. 10 is a diagram schematically illustrating the transition of power that can be supplied from a solar power generation device according to a fifth embodiment of the present disclosure. [Figure 7] FIG. 10 is a schematic diagram illustrating a configuration of a modified example of a power supply system according to the fifth embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a redox flow battery 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 according to embodiment 1 of the present disclosure> As shown in FIG. 1 , a redox flow battery 1 according to a first embodiment of the present disclosure includes a cell 2 having a first chamber 3 and a second chamber 4 separated by a diaphragm 5, a first electrolyte solution flow device 21 that flows a first electrolyte solution 12 containing an active material into the first chamber 3, and a second electrolyte solution flow device 22 that flows a second electrolyte solution 13 containing an active material into the second chamber 4. A first electrode 14 is provided in the first chamber 3, and a second electrode 15 is provided in the second chamber 4. Although FIG. 1 illustrates only one cell 2, a cell stack in which two or more cells are stacked may also be used as the cell 2. In the following description, unless there is a clear reference to excluding a cell stack, the term "cell" will also include a cell stack.

[0011] The first electrode 14 and the second electrode 15 are each electrically connected to an AC-DC converter 16. A power supply device 17 that supplies power to the redox flow battery 1 when the redox flow battery 1 is charged, and a load 18 that consumes power discharged from the redox flow battery 1 are electrically connected to the AC-DC converter 16. Note that if the current supplied from the power supply device 17 is DC and the load 18 operates on DC, the AC-DC converter 16 is not necessary.

[0012] The first electrolyte solution flow device 21 includes a high-level electrolyte solution tank 23 capable of storing the first electrolyte solution 12 and located at a higher position than the cell 2, an electrolyte solution flow path 24 connecting the high-level electrolyte solution tank 23 with the inlet 3a of the first chamber 3, and an electrolyte solution outflow path 25 having one end connected to the outlet 3b of the first chamber 3. Although not an essential component, a flow rate adjustment valve 26 may be provided in the electrolyte solution flow path 24.

[0013] The other end of the electrolyte outflow path 25 may be connected to a lower-level electrolyte tank 27 located at a lower position than the higher-level electrolyte tank 23. When the lower-level electrolyte tank 27 is provided, an electrolyte inflow path 28 may be provided that connects the lower-level electrolyte tank 27 to the inlet 3a of the first chamber 3, and a circulation pump 29 may be provided for the electrolyte inflow path 28. The downstream ends of the electrolyte flow path 24 and the electrolyte inflow path 28 may be connected separately to the inlet 3a of the first chamber 3, or, as shown in FIG. 1 , a confluence path 30 formed by converging the electrolyte flow path 24 and the electrolyte inflow path 28 may be connected to the inlet 3a of the first chamber 3. The electrolyte flow path 24 and the electrolyte inflow path 28 are provided with on-off valves 31 and 32, respectively.

[0014] Furthermore, an electrolyte transfer path 33 may be provided that connects the lower-level electrolyte tank 27 and the higher-level electrolyte tank 23. Because the electrolyte transfer path 33 is used to transfer the first electrolyte solution 12 from the lower-level electrolyte tank 27 to the higher-level electrolyte tank 23, a boost pump 34 for transferring the first electrolyte solution 12 must be provided in the electrolyte transfer path 33. The upstream ends of the electrolyte inflow path 28 and the electrolyte transfer path 33 may be connected separately to the lower-level electrolyte tank 27. In this case, the circulation pump 29 and the boost pump 34 are separate pumps. However, as shown in FIG. 1 , if the upstream end of the electrolyte transfer path 33 is connected to the electrolyte inflow path 28 downstream of the circulation pump 29, the circulation pump 29 and the boost pump 34 can be combined into a single pump. In this case, an on-off valve 35 is provided in the electrolyte transfer path 33.

[0015] The second electrolyte solution flow device 22 may have the same configuration as the first electrolyte solution flow device 21. FIG. 1 illustrates a case in which the first electrolyte solution flow device 21 and the second electrolyte solution flow device 22 have the same configuration. In this case, the first electrolyte solution flow device 21 and the second electrolyte solution flow device 22 differ in configuration only in that the electrolyte solution outflow path 25 and the merging path 30 of the second electrolyte solution flow device 22 are connected to the outlet 4b and the inlet 4a of the second chamber 4, respectively. Alternatively, only one of the first electrolyte solution flow device 21 and the second electrolyte solution flow device 22 may have the above-described configuration. In this case, the other device, which does not have the above-described configuration, may have a configuration similar to that of a general redox flow battery, including an electrolyte solution circulation path having one end connected to the inlet 3a or 4a and the other end connected to the outlet 3b or 4b, and an electrolyte solution tank and a circulation pump provided in the electrolyte solution circulation path.

[0016] Each of the first electrolytic solution 12 and the second electrolytic solution 13 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 electrolytic solution 12 and the second electrolytic solution 13 can be a metal ion such as vanadium, a metal complex, air, a halogen, or an organic molecule such as quinone or hydroquinone.

[0017] <Operation of the redox flow battery according to the first embodiment of the present disclosure> Next, the operation of the redox flow battery 1 according to the first embodiment of the present disclosure will be described. First, the discharge operation of the redox flow battery 1 will be described. It is assumed that the first electrolytic solution 12 and the second electrolytic solution 13 after charging are stored in the respective high-level electrolyte tanks 23 provided in the first electrolytic solution distribution device 21 and the second electrolytic solution distribution device 22. When the on-off valve 31 (and the flow rate control valve 26) is opened, the first electrolytic solution 12 and the second electrolytic solution 13 flow from the respective high-level electrolyte tanks 23 through the respective electrolyte distribution paths 24 into the first chamber 3 and the second chamber 4, respectively, due to the hydraulic head difference between the liquid level 12a of the first electrolytic solution 12 and the liquid level 13a of the second electrolytic solution 13 in each high-level electrolyte tank 23 and the first chamber 3 and the second chamber 4 (i.e., the cell 2). After the first chamber 3 and the second chamber 4 are filled with the first electrolytic solution 12 and the second electrolytic solution 13, respectively, the first electrolytic solution 12 and the second electrolytic solution 13 flow out of the first chamber 3 and the second chamber 4 through the respective electrolytic solution outflow paths 25. In this way, the first electrolytic solution 12 and the second electrolytic solution 13 flow through the first chamber 3 and the second chamber 4, respectively.

[0018] When the redox flow battery 1 discharges, the first chamber 3 serves as the positive electrode and the second chamber 4 serves as the negative electrode. When the first electrolytic solution 12 flows through the first chamber 3, the active material contained in the first electrolytic solution 12 is reduced. On the other hand, when the second electrolytic solution 13 flows through the second chamber 4, the active material contained in the second electrolytic solution 13 is oxidized. That is, the second electrode 15 receives electrons released from the active material contained in the second electrolytic solution 13, and the active material contained in the first electrolytic solution 12 receives electrons that have moved from the second electrode 15 to the first electrode 14, causing a direct current to flow from the first electrode 14 to the second electrode 15. This direct current is converted to an alternating current by the AC-DC converter 16, and power is supplied to and consumed by the load 18.

[0019] In this way, by supplying the first electrolytic solution 12 and the second electrolytic solution 13 from each higher-level electrolyte tank 23 to the first chamber 3 and the second chamber 4 of the cell, respectively, by using the hydraulic head difference between the higher-level electrolyte tank 23 and the cell 2, it is possible to eliminate loss due to pump power consumption compared to when using a pump to supply the first electrolytic solution 12 and the second electrolytic solution 13 to the first chamber 3 and the second chamber 4, and it is therefore possible to increase the discharge output while reducing loss. Furthermore, even when either the first electrolytic solution 12 or the second electrolytic solution 13 is supplied from the higher-level electrolyte tank 23 to either the first chamber 3 or the second chamber 4, it is possible to reduce loss due to pump power consumption compared to when both electrolytic solutions are supplied by pump, and it is therefore possible to discharge while reducing loss.

[0020] The flow rates of the first and second electrolyte solutions 12 and 13 supplied from each high-level electrolyte tank 23 to the first and second chambers 3 and 4 are determined by the hydraulic head difference between each high-level electrolyte tank 23 and the cell 2. Therefore, unless these flow rates can be adjusted, the flow rate of the electrolyte supplied to the redox flow battery 1 will be excessive when the power required by the load 18 is low. In such a case, if a flow rate adjustment valve 26 is provided in each electrolyte flow path 24, the flow rate of the first and second electrolyte solutions 12 and 13 supplied from each high-level electrolyte tank 23 to the first and second chambers 3 and 4 can be reduced by controlling the aperture of each flow rate adjustment valve 26. This reduces the flow rate to an appropriate level for the power supplied to the load 18, enabling efficient discharge from the redox flow battery 1.

[0021] In the first embodiment, if a low-level electrolyte tank 27 is provided to connect to the other end of the electrolyte outflow path 25, the first electrolyte solution 12 and the second electrolyte solution 13 supplied from each high-level electrolyte tank 23 to the first chamber 3 and the second chamber 4 can be recovered in each low-level electrolyte tank 27. Furthermore, if an electrolyte transfer path 33, a boost pump 34, and an on-off valve 35 are provided, the first electrolyte solution 12 and the second electrolyte solution 13 recovered in each low-level electrolyte tank 27 can be transferred to each high-level electrolyte tank 23 by opening the on-off valve 35 and starting the boost pump 34. If the charge rates of the first electrolyte solution 12 and the second electrolyte solution 13 in each low-level electrolyte tank 27 are sufficient, the first electrolyte solution 12 and the second electrolyte solution 13 transferred to each high-level electrolyte tank 23 can be supplied again to the first chamber 3 and the second chamber 4 by the above-mentioned operation, thereby allowing the discharge operation of the redox flow battery 1 to continue.

[0022] In the first embodiment, the redox flow battery 1 can be charged as long as the electrolyte inflow path 28, the circulation pump 29, and the on-off valve 32 are provided. Charging is performed as follows: When the on-off valve 32 is opened and the circulation pump 29 is started, the first electrolyte solution 12 and the second electrolyte solution 13 flow out of each lower electrolyte tank 27, pass through each electrolyte inflow path 28, and flow into the first chamber 3 and the second chamber 4. The first electrolyte solution 12 and the second electrolyte solution 13 flow out of the first chamber 3 and the second chamber 4, and flow back into each lower electrolyte tank 27 via each electrolyte outflow path 25.

[0023] In this way, while the first electrolytic solution 12 and the second electrolytic solution 13 circulate between the cell 2 and each lower-level electrolyte tank 27, the AC current from the power supply device 17 is converted to DC current by the AC-DC converter 16, and a current flows between the first electrode 14 and the second electrode 15. When the first electrolytic solution 12 flows through the first chamber 3, the active material contained in the first electrolytic solution 12 is oxidized. On the other hand, when the second electrolytic solution 13 flows through the second chamber 4, the active material contained in the second electrolytic solution 13 is reduced. As a result, the active materials contained in the first electrolytic solution 12 and the second electrolytic solution 13 become usable for the discharge operation of the redox flow battery 1.

[0024] By providing the electrolyte transfer path 33, the boost pump 34, and the on-off valve 35, the first electrolyte solution 12 and the second electrolyte solution 13 after charging can be transferred to the respective higher electrolyte tanks 23, and the first electrolyte solution 12 and the second electrolyte solution 13 transferred to the respective higher electrolyte tanks 23 can be supplied to the first chamber 3 and the second chamber 4, thereby enabling the redox flow battery 1 to perform a discharge operation.

[0025] (Embodiment 2) Next, a redox flow battery according to embodiment 2 will be described. The redox flow battery according to embodiment 2 is a modification of embodiment 1 in that multiple cells are arranged in parallel. 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.

[0026] <Configuration of redox flow battery according to embodiment 2 of the present disclosure> As shown in Fig. 2, in the redox flow battery 1 according to the second embodiment of the present disclosure, the cell 2 includes a plurality of cells arranged in parallel with the direction in which the first electrolytic solution 12 and the second electrolytic solution 13 flow from each of the higher electrolyte tanks 23 toward the first chamber 3 and the second chamber 4. While Fig. 2 illustrates four cells 2a, 2b, 2c, and 2d as an example, the number of cells is not limited to four, and any number of cells equal to or greater than two may be provided.

[0027] Each electrolyte solution flow path 24 of the first electrolyte solution flow device 21 and the second electrolyte solution flow device 22 branches into four branch portions 24a, 24b, 24c, and 24d on the downstream side, which are connected to the inlets 3a of the first chambers 3 and the inlets 4a of the second chambers 4 of the cells 2a to 2d, respectively. Each electrolyte solution outflow path 25 of the first electrolyte solution flow device 21 and the second electrolyte solution flow device 22 branches into four branch portions 25a, 25b, 25c, and 25d on the upstream side, which are connected to the outlets 3b of the first chambers 3 and the outlets 4b of the second chambers 4 of the cells 2a to 2d, respectively. The other configurations are the same as those of the first embodiment.

[0028] <Operation of the redox flow battery according to the second embodiment of the present disclosure> Next, the operation of the redox flow battery 1 according to the second embodiment of the present disclosure will be described. When the redox flow battery 1 is discharged, the operation is the same as in the first embodiment. Due to the hydraulic head difference between the liquid level 12a of the first electrolytic solution 12 and the liquid level 13a of the second electrolytic solution 13 in each high-level electrolyte tank 23 and the first chamber 3 and the second chamber 4 of each of the cells 2a to 2d, the first electrolytic solution 12 and the second electrolytic solution 13 flow from each high-level electrolyte tank 23 through each electrolyte flow path 24 into each of the first chamber 3 and the second chamber 4, respectively, and flow out of each of the first chamber 3 and the second chamber 4 through each electrolyte outflow path 25. That is, the first electrolytic solution 12 and the second electrolytic solution 13 flow through each of the first chamber 3 and the second chamber 4, respectively. At this time, the principle of the flow of direct current between the first electrode 14 (see FIG. 1 ) and the second electrode 15 (see FIG. 1 ) in each of the cells 2a to 2d is the same as in the first embodiment.

[0029] The flow rates of the first electrolytic solution 12 and the second electrolytic solution 13 flowing through each of the first chambers 3 and each of the second chambers 4 are determined by the hydraulic head difference described above. Therefore, unless each of the high-level electrolyte tanks 23 can be installed at a sufficiently high position relative to the cell 2, the redox flow battery 1 will not be able to provide the desired discharge output. When a sufficient hydraulic head difference cannot be ensured, reducing the electrode area within the cell 2 to shorten the length of the flow path within the cell 2 through which the first electrolytic solution 12 and the second electrolytic solution 13 flow reduces the flow path resistance, making it possible to ensure the flow rates of the first electrolytic solution 12 and the second electrolytic solution 13. However, the output of the cell will decrease in proportion to the reduced electrode area. In contrast, in the second embodiment, the output of the entire cell 2 can be ensured by arranging multiple cells 2a to 2d in parallel.

[0030] For example, if the flow rates of the first electrolytic solution 12 and the second electrolytic solution 13 are half of the desired flow rate because a sufficient head difference cannot be ensured, the desired discharge output can be obtained by halving the electrode area of ​​each cell and doubling the number of installed cells. This allows for a flexible design to accommodate a variety of discharge output specifications and location conditions (particularly the difference in height between the upper electrolyte tank 23 and the cells 2) for the redox flow battery 1.

[0031] The charging operation in the cells 2a to 2d and the operation of transferring the first electrolytic solution 12 and the second electrolytic solution 13 from each lower-level electrolytic solution tank 27 to each higher-level electrolytic solution tank 23 are the same as those in the first embodiment.

[0032] (Embodiment 3) Next, a redox flow battery according to Embodiment 3 will be described. The redox flow battery according to Embodiment 3 is a modification of Embodiment 1 or 2, in that the gas phase of the higher-level electrolyte tank 23 and the gas phase of the lower-level electrolyte tank 27 are connected to each other. Hereinafter, a configuration in which this modification is made to Embodiment 1 will be described as Embodiment 3, but a configuration in which this modification is made to Embodiment 2 can also be referred to as Embodiment 3. In Embodiment 3, the same components as those in Embodiment 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0033] <Configuration of redox flow battery according to embodiment 3 of the present disclosure> As shown in Fig. 3, in the redox flow battery 1 according to the third embodiment of the present disclosure, a communication pipe 40 is provided that communicates the gas phase of each upper electrolyte tank 23 with the gas phase of each lower electrolyte tank 27. Each communication pipe 40 is connected to a cylinder 41 that stores an inert gas such as nitrogen or a rare gas. The cylinder 41 may be connected to either the upper electrolyte tank 23 or the lower electrolyte tank 27. The other configurations are the same as those of the first embodiment.

[0034] <Operation of the redox flow battery according to the third embodiment of the present disclosure> Because the first electrolyte solution 12 and the second electrolyte solution 13 react with oxygen in the air and oxidize, it is necessary to seal the upper electrolyte solution tank 23 and the lower electrolyte solution tank 27 with inert gas. When the electrolyte solution flows out of each tank, the volume of the internal gas phase increases, so the tanks must be replenished with inert gas. If a separate device for supplying inert gas to each tank is provided, inert gas will be supplied every time the electrolyte solution flows out of each tank, resulting in continuous consumption of inert gas.

[0035] When the higher-level electrolyte tank 23 and the lower-level electrolyte tank 27 are provided, when the first electrolytic solution 12 or the second electrolytic solution 13 moves from one tank to the other, the volume of the gas phase in each tank changes, but the total volume of the gas phase in both tanks remains constant. Therefore, if the gas phase in the higher-level electrolyte tank 23 and the gas phase in the lower-level electrolyte tank 27 are connected by the connecting pipe 40 as in the third embodiment, the inert gas supplied to both tanks from the cylinder 41 via the connecting pipe 40 flows back and forth via the connecting pipe 40. This makes it possible to seal both tanks without refilling them with inert gas, thereby reducing consumption of the inert gas and improving the operating cost of the redox flow battery 1.

[0036] The discharge operation and charge operation of the redox flow battery 1 in the third embodiment are the same as those in the first embodiment.

[0037] (Embodiment 4) Next, a redox flow battery according to Embodiment 4 will be described. The redox flow battery according to Embodiment 4 is a battery obtained by modifying each of Embodiments 1 to 3 in order to suppress a temperature rise in the first electrolytic solution 12 and the second electrolytic solution 13. Hereinafter, a configuration obtained by modifying Embodiment 1 in this way will be described as Embodiment 4, but a configuration obtained by modifying Embodiment 2 or 3 in this way can also be referred to as Embodiment 4. In Embodiment 4, the same components as those in Embodiment 1 will be denoted by the same reference numerals, and detailed description thereof will be omitted.

[0038] 4, in the redox flow battery 1 according to the fourth embodiment of the present disclosure, the lower electrolyte tank 27 is buried in the ground. Here, "buried in the ground" means that the lower electrolyte tank 27 is buried in the underground UG, which is a region below the ground surface G, so that at least a part of the outer surface, and preferably the entire outer surface, of the lower electrolyte tank 27 is in contact with the soil that constitutes the underground UG.

[0039] Generally, when the temperature of the electrolyte rises, the active material dissolved in the electrolyte may precipitate (hereinafter referred to as "deterioration of the electrolyte"). For example, in the case of a vanadium-based active material, deterioration may occur if the electrolyte temperature exceeds 45°C. The possibility of electrolyte deterioration is particularly high during the hot summer months. It is known that even if the outside air temperature changes throughout the day, the temperature change of the underground UG is generally smaller than the change in the outside air temperature. Therefore, heat exchange between the soil constituting the ground and the first electrolytic solution 12 or the second electrolytic solution 13 in the low electrolyte tank 27 can keep the temperature of the first electrolytic solution 12 or the second electrolytic solution 13 almost constant even when the outside air temperature rises, thereby reducing the risk of deterioration of the first electrolytic solution 12 or the second electrolytic solution 13.

[0040] Furthermore, in addition to or independently of the lower electrolyte tank 27 being buried underground, the higher electrolyte tank 23 may be installed above ground AG, and the lower electrolyte tank 27 may be installed in a basement 50 formed in the underground UG. Here, the above ground AG includes the area above ground G and an area above ground G. By installing both tanks in this manner, it is possible to reliably ensure a head difference between the liquid level 12a of the first electrolyte 12 or the liquid level 13a of the second electrolyte 13 in the higher electrolyte tank 23 and the cells 2. Furthermore, by appropriately adjusting the temperature in the basement 50, the redox flow battery 1 can be installed without problems even in areas with high temperatures.

[0041] When the high-level electrolyte tank 23 is installed outdoors on the ground AG, for example, when the high-level electrolyte tank 23 is installed on the roof of a building 52 such as a building, a canopy 51 (shielding member) may be provided between the sun S and the high-level electrolyte tank 23. Even when direct sunlight from the sun S is irradiated onto the high-level electrolyte tank 23, the canopy 51 blocks the direct sunlight, thereby suppressing an increase in the temperature of the first electrolyte solution 12 or the second electrolyte solution 13 inside the high-level electrolyte tank 23, thereby reducing the risk of deterioration of the first electrolyte solution 12 and the second electrolyte solution 13.

[0042] (Embodiment 5) Next, a fifth embodiment will be described. The fifth embodiment relates to a power supply system including any one of the redox flow batteries 1 according to the first to fourth embodiments and another device capable of supplying power to a load 18. In the fifth embodiment, the same components as those in the first to fourth embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0043] <Power supply system configuration> As shown in Fig. 5, a power supply system 100 according to a fifth embodiment of the present disclosure includes a redox flow battery 1 and a power generation device 60. The configuration of the power generation device 60 is not particularly limited, and may be a solar power generation device or a tidal power generation device that generates power in accordance with the tidal cycle (approximately 12 hours). The following description will be given taking as an example a case where the power generation device 60 is a solar power generation device 60a.

[0044] The power supply system 100 is electrically connected to a load 18 via an AC-DC converter 16. In the fifth embodiment as well, if the load 18 operates on DC current, the AC-DC converter 16 is not necessary. The power supply system 100 may include a changeover switch 61 that can switch between electrically connecting either the redox flow battery 1 or the solar power generation device 60a to the AC-DC converter 16 and turning on and off the electrical connection between the redox flow battery 1 and the solar power generation device 60a.

[0045] <Power supply system operation> Next, the operation of the power supply system 100 will be described. As shown schematically in Fig. 6, the amount of power generated by a solar power generation device generally changes so that it starts generating power after sunrise (morning), increases toward noon, and then decreases toward sunset (night). Of course, depending on the weather of the day, there may be a temporary or long-term deviation from this change, but if the weather is suitable for generating power all day, this power generation trend is considered to be observed. Note that the vertical axis of the graph in Fig. 6 represents the power that can be supplied from the solar power generation device, which is correlated with the amount of power generated by the solar power generation device.

[0046] In FIG. 6, the lower limit of the power demand of the load 18 is indicated by a dashed horizontal line. After the start of power generation at time T0, the amount of power generated is low for a while, so the supplyable power does not reach the lower limit of the power demand of the load 18. However, at a certain time T1, the supplyable power reaches the lower limit of the power demand of the load 18. At this time, the selector switch 61 electrically connects the solar power generation device 60a to the AC-DC converter 16, thereby supplying power from the solar power generation device 60a to the load 18. That is, the lower limit of the power demand of the load 18 is set as a threshold for starting power supply from the solar power generation device 60a. When the power that can be supplied from the solar power generation device 60a reaches this threshold (in other words, when the power that can be supplied from the solar power generation device 60a reaches the threshold), the solar power generation device 60a starts supplying power to the load 18. After that, the amount of power generated reaches a maximum, and then the amount of power generated decreases. At a certain time T4, the supplyable power reaches the lower limit of the power demand of the load 18. When this occurs, the changeover switch 61 switches to electrically connect the pre-charged redox flow battery 1 and the AC-DC converter 16, thereby allowing power to be supplied from the redox flow battery 1 to the load 18, and power supply to the load 18 is continued. That is, the lower limit of the power demand of the load 18 is set as a threshold value for terminating power supply from the solar power generation device 60a, and when the power that can be supplied from the solar power generation device 60a reaches this threshold value (in other words, when the power that can be supplied from the solar power generation device 60a reaches the threshold value), power supply is switched from the redox flow battery 1 to the load 18.

[0047] Even between times T1 and T4, the amount of power generated may decrease due to a sudden change in weather or a malfunction of the solar power generation device 60a, and the amount of power that can be supplied may fall below the lower limit of the power demand of the load 18. Even in such a case, power supply to the load 18 can be continued by switching to supply power from the redox flow battery 1 to the load 18. In the above explanation, the threshold for starting power supply from the solar power generation device 60a and the threshold for ending power supply from the solar power generation device 60a are each set to the lower limit of the power demand of the load 18, but each threshold may be set to a different value.

[0048] In this way, when the amount of power generated by the solar power generation device 60a decreases and the amount of power supplied from the solar power generation device 60a decreases, the redox flow battery 1 discharges power, making it possible to continue supplying power.

[0049] Although there are no particular limitations on when and how the redox flow battery 1 is charged, charging according to the operation described below can improve the operating efficiency of the entire power supply system 100. The amount of power generated continues to increase for a while after time T1. As a result, for example, after time T2, which is later than time T1, sufficient surplus power is generated to charge the redox flow battery 1. If this surplus power is used to charge the redox flow battery 1, the power generated by the solar power generation device 60a can be effectively utilized. Specifically, a set value (equivalent to the power that can be supplied at time T2) for the power that can be supplied from the solar power generation device 60a is set in advance. When the power that can be supplied from the solar power generation device 60a reaches this set value, the selector switch 61 turns on the electrical connection between the redox flow battery 1 and the solar power generation device 60a. Then, power is supplied from the solar power generation device 60a not only to the AC-DC converter 16 but also to the redox flow battery 1. By driving the circulation pump 29 (see FIG. 1, etc.) of the redox flow battery 1 with this power, the redox flow battery 1 can be charged by the charging operation described in the first embodiment, etc.

[0050] At time T3, which is before time T4, when the redox flow battery 1 is fully charged, or when it is not fully charged but is charged to a certain extent, the charging operation of the redox flow battery 1 is terminated, and as described in embodiment 1 and the like, the boost pump 34 (see FIG. 1 and the like) is driven to transfer the first electrolyte solution 12 (see FIG. 1 and the like) or the second electrolyte solution 13 (see FIG. 1 and the like) in the low-level electrolyte tank 27 (see FIG. 1 and the like) to the high-level electrolyte tank 23 (see FIG. 1 and the like). As a result, the redox flow battery 1 becomes dischargeable by time T4, when the power that can be supplied from the solar power generation device 60a reaches the lower limit of the power demand of the load 18. Therefore, power can be supplied from the redox flow battery 1 to the load 18 after time T4.

[0051] In this way, by using the surplus power generated by the solar power generation device 60a to charge the redox flow battery 1, the operating efficiency of the entire power supply system 100 can be improved.

[0052] <Modification of power supply system> In the fifth embodiment, a power generation device has been described as an example of another device capable of supplying power to the load 18, but the present invention is not limited to a power generation device. For example, as shown in FIG. 7 , a power supply system 110 according to a modification of the fifth embodiment includes a redox flow battery 1 and a power supply device 70. The configuration of the power supply device 70 is not particularly limited, and it may be any device that does not have a power generation function but is capable of supplying power. For example, the power supply device 70 may be a secondary battery other than a redox flow battery, such as a battery, or an AC power source used in homes, factories, stores, etc.

[0053] The power supply system 110 is electrically connected to the load 18 via an AC-DC converter 16. The power supply system 110 may include a changeover switch 71 that can be switched to electrically connect either the redox flow battery 1 or the power supply device 70 to the AC-DC converter 16. In the power supply system 110, too, if the load 18 operates on DC current, the AC-DC converter 16 is not necessary. Furthermore, if the power supply device 70 is an AC power source, the power supply device 70 can be directly connected to the changeover switch 71 without going through the AC-DC converter 16.

[0054] In the power supply system 110, power is supplied to the load 18 from either the power supply device 70 or the redox flow battery 1 by switching operation of a selector switch 71. The power supply device 70 and the redox flow battery 1 may be used alternately as power sources, or one may be used as the main power source and the other as an auxiliary power source. In the latter case, for example, if the AC power source used in a factory is the power supply device 70, when the power supply device stops and power is lost, such as during a power outage, the selector switch 71 switches to connect the redox flow battery 1 and the AC-DC converter 16, and the on-off valve 31 (and the flow rate control valve 26) (see FIG. 1, etc.) in the redox flow battery 1 is opened. This allows the first electrolytic solution 12 (see FIG. 1, etc.) and the second electrolytic solution 13 (see FIG. 1, etc.) to be supplied to each chamber of the cell 2 (see FIG. 1, etc.) and discharge of the redox flow battery 1 to begin, thereby allowing the supply of power to the load 18 to continue and preventing shutdown of the factory.

[0055] The contents described in each of the above embodiments can be understood, for example, as follows.

[0056] [1] A redox flow battery according to one embodiment includes: At least one cell (2) having a first chamber (3) and a second chamber (4) separated by a diaphragm (5); a first electrolytic solution flow device (21) for flowing a first electrolytic solution (12) through the first chamber (3); a second electrolytic solution flow device (22) for flowing a second electrolytic solution (13) through the second chamber (4); Equipped with At least one of the first electrolytic solution distribution device (21) and the second electrolytic solution distribution device (22) a high-level electrolyte tank (23) provided at a position higher than the at least one cell (2); an electrolyte flow path (24) communicating the higher electrolyte tank (23) with the first chamber (3) or the second chamber (4); an electrolyte outflow path (25) through which the first electrolyte (12) or the second electrolyte (13) flowing from the higher electrolyte tank (23) into the first chamber (3) or the second chamber (4) flows out of the first chamber (3) or the second chamber (4); Equipped with The first electrolytic solution (12) or the second electrolytic solution (13) is configured to flow from the higher-level electrolyte tank (23) through the electrolyte flow path (24) into the first chamber (3) or the second chamber (4) due to a head difference between the liquid level (12a, 13a) of the first electrolytic solution (12) or the second electrolytic solution (13) in the higher-level electrolyte tank (23) and the at least one cell (2).

[0057] According to the redox flow battery of the present disclosure, the first electrolytic solution or the second electrolytic solution is supplied from the higher-level electrolyte tank to at least one of the first and second chambers of the cell by using the hydraulic head difference between the higher-level electrolyte tank and the cell. This eliminates loss due to the power consumption of the pump compared to when the first electrolytic solution or the second electrolytic solution is supplied to the first or second chamber using a pump, and therefore enables discharge while reducing loss.

[0058] [2] A redox flow battery according to another embodiment is the redox flow battery according to [1], At least one of the first electrolyte solution distribution device (21) and the second electrolyte solution distribution device (22) includes a low-level electrolyte solution tank (27) connected to the electrolyte solution outflow path (25) at a position lower than the high-level electrolyte solution tank (23).

[0059] According to this configuration, the first or second electrolytic solution that flows from the higher-level electrolyte tank into the first or second chamber is recovered in the lower-level electrolyte tank. By returning the recovered first or second electrolytic solution directly to the higher-level electrolyte tank, or by returning the first or second electrolytic solution after charging to the higher-level electrolyte tank, the first or second electrolytic solution can be introduced into the first or second chamber without loss due to pump power consumption, thereby enabling discharge with reduced loss.

[0060] [3] A redox flow battery according to yet another embodiment is the redox flow battery according to [2], At least one of the first electrolytic solution distribution device (21) and the second electrolytic solution distribution device (22) an electrolyte inlet path (28) communicating the lower electrolyte tank (27) with the inlet (3a, 4a) of the first chamber (3) or the second chamber (4); a circulation pump (29) provided in the electrolyte inlet path (28); Equipped with.

[0061] According to this configuration, the first or second electrolytic solution that flows from the higher-level electrolyte tank into the first or second chamber is recovered in the lower-level electrolyte tank, and the recovered first or second electrolytic solution is circulated between the lower-level electrolyte tank and the first or second chamber to charge the redox flow battery. By returning the first or second electrolytic solution after charging to the higher-level electrolyte tank, the first or second electrolytic solution can be flowed into the first or second chamber without loss due to power consumption by the pump, thereby enabling discharge with reduced loss.

[0062] [4] A redox flow battery according to yet another embodiment is the redox flow battery according to [2] or [3], At least one of the first electrolytic solution distribution device (21) and the second electrolytic solution distribution device (22) an electrolyte transfer path (33) communicating between the lower level electrolyte tank (27) and the higher level electrolyte tank (23); a booster pump (34) provided in the electrolyte supply path (33); Equipped with.

[0063] According to this configuration, the first or second electrolytic solution that flows from the higher-level electrolyte tank into the first or second chamber is recovered in the lower-level electrolyte tank. By returning the recovered first or second electrolytic solution directly to the higher-level electrolyte tank, or by returning the first or second electrolytic solution after charging to the higher-level electrolyte tank, the first or second electrolytic solution can be introduced into the first or second chamber without loss due to pump power consumption, thereby enabling discharge with reduced loss.

[0064] [5] A redox flow battery according to yet another embodiment is the redox flow battery according to any one of [2] to [4], A communication pipe (40) is provided to communicate the gas phase of the higher-level electrolyte tank (23) with the gas phase of the lower-level electrolyte tank (27).

[0065] Because the first and second electrolyte solutions react with oxygen in the air and oxidize, the tanks storing the first and second electrolyte solutions must be sealed with an inert gas such as nitrogen or a rare gas. When a high-level electrolyte tank and a low-level electrolyte tank are provided in the first or second electrolyte solution distribution device, the volume of the gas phase in each tank changes when the first and second electrolyte solutions move from one tank to the other, but the total volume of the gas phase in both tanks remains constant. Therefore, if the gas phases of the high-level electrolyte tank and the low-level electrolyte tank are connected by a connecting pipe, the inert gas in both tanks can flow back and forth through the connecting pipe, allowing both tanks to be sealed without refilling them with inert gas. This reduces inert gas consumption and improves the operating costs of the redox flow battery.

[0066] [6] A redox flow battery according to yet another embodiment is the redox flow battery according to any one of [2] to [5], The low level electrolyte tank (27) is buried underground.

[0067] With this configuration, heat exchange occurs between the underground soil and the first or second electrolytic solution in the low-electrolyte tank, so that the temperature of the first or second electrolytic solution can be kept almost constant even when the outside air temperature is high, thereby reducing the risk of deterioration of the first or second electrolytic solution.

[0068] [7] A redox flow battery according to yet another embodiment is the redox flow battery according to any one of [1] to [6], The upper electrolyte tank (23) is provided above ground (AG), and the at least one cell (2) is provided in a basement (50).

[0069] With this configuration, it is possible to reliably ensure a hydraulic head difference between the liquid level of the first electrolytic solution or the second electrolytic solution in the higher-level electrolytic solution tank and the cell.

[0070] [8] A redox flow battery according to yet another embodiment is the redox flow battery according to any one of [1] to [7], The high-level electrolyte tank (23) is provided on the ground (AG), and is provided with a shielding member (eaves 51) for blocking direct sunlight from hitting the high-level electrolyte tank.

[0071] With this configuration, even if direct sunlight from the sun is irradiated onto the high-level electrolyte tank, the shielding member blocks the direct sunlight, thereby preventing the temperature of the first electrolyte solution or the second electrolyte solution in the high-level electrolyte tank from rising, thereby reducing the risk of electrolyte degradation.

[0072] [9] A redox flow battery according to yet another embodiment is the redox flow battery according to any one of [1] to [8], The at least one cell (2) includes a plurality of cells (2a, 2b, 2c, 2d) arranged in parallel with respect to the flow direction of the first electrolytic solution (12) or the second electrolytic solution (13) from the higher-level electrolytic solution tank (23).

[0073] If it is not possible to ensure a sufficient head difference between the liquid level of the first or second electrolytic solution in the high-level electrolyte tank and the cell, reducing the electrode area in the cell and shortening the length of the flow path through which the first or second electrolytic solution flows will reduce the flow path resistance and make it possible to ensure the flow rate of the first or second electrolytic solution, but this will reduce the cell output.Therefore, by arranging multiple cells in parallel, the output of the entire cell can be ensured.

[0074]

[10] A redox flow battery according to yet another embodiment is the redox flow battery according to any one of [1] to [9], The electrolyte flow path (24) is provided with a flow rate control valve (26).

[0075] According to this configuration, when the flow rate of the electrolyte supplied to the redox flow battery becomes excessive, the flow rate of the first electrolyte solution or the second electrolyte solution supplied from the high-level electrolyte tank to the first chamber or the second chamber can be reduced, thereby reducing the flow rate to an appropriate level for the required power, and enabling efficient discharge from the redox flow battery.

[0076]

[11] A power supply system according to one aspect includes: [3] Redox flow battery (1) and A power generating device (60) and Equipped with When the power that can be supplied from the power generation device (60) reaches a preset value, the circulation pump (29) is started to circulate the first electrolytic solution (12) or the second electrolytic solution (13) between the lower-level electrolyte tank (27) and the first chamber (3) or the second chamber (4), thereby charging the redox flow battery (1).

[0077] According to the power supply system of the present disclosure, the redox flow battery is charged using surplus power generated by the power generation device, thereby improving the operating efficiency of the entire power supply system.

[0078]

[12] A power supply system according to one aspect includes: A redox flow battery (1) according to any one of [1] to

[10] ; A power generating device (60) and Equipped with When the power that can be supplied from the power generation device (60) reaches a preset threshold, the first electrolytic solution (12) or the second electrolytic solution (13) is supplied from the higher level electrolytic solution (23) to the first chamber (3) or the second chamber (4), thereby discharging the redox flow battery (1).

[0079] According to the power supply system of the present disclosure, when the amount of power generated by the power generation device decreases and the amount of power supplied from the power generation device decreases, power supply can be continued by discharging from the redox flow battery.

[0080]

[13] A power supply system according to one aspect includes: A redox flow battery (1) according to any one of [1] to

[10] ; A power supply device (70) Equipped with When the power supply from the power supply device (70) is stopped, the first electrolytic solution (12) or the second electrolytic solution (13) is supplied from the higher level electrolytic solution (23) to the first chamber (3) or the second chamber (4), thereby discharging the redox flow battery (1).

[0081] According to the power supply system of the present disclosure, when the power supply from the power supply device is stopped due to a malfunction of the power supply device or the like, the power supply can be continued by discharging from the redox flow battery. [Explanation of symbols]

[0082] 1. Redox flow battery 2, 2a, 2b, 2c, 2d cells 3 Room 1 3a (Room 1) Entrance 3b (Exit from Room 1) 4 Room 2 4a (2nd room) entrance 4b (Exit from Room 2) 5 Diaphragm 12 First electrolyte 12a (First electrolyte) liquid level 13 Second electrolyte 13a (Second electrolyte) liquid level 21 1st electrolyte distribution device 22 Second electrolyte distribution device 23 High-level electrolyte tank 24 Electrolyte distribution channel 25 Electrolyte leakage path 26 Flow control valve 27 Low level electrolyte tank 28 Electrolyte inflow path 29 Circulation Pump 33 Electrolyte transport path 34 Booster pump 40 Communication pipe 50 Basement 51 Eaves (shielding member) 60 Power Generation Equipment 70 Power Supply Device 100 Power Supply System 110 Power Supply System

Claims

1. At least one cell having a first chamber and a second chamber separated by a diaphragm; a first electrolytic solution flow device for flowing a first electrolytic solution through the first chamber; a second electrolytic solution flow device for flowing a second electrolytic solution through the second chamber; Equipped with At least one of the first electrolytic solution distribution device and the second electrolytic solution distribution device is a high-level electrolyte tank provided at a position higher than the at least one cell; an electrolyte flow path communicating the higher-level electrolyte tank with an inlet of the first chamber or the second chamber; an electrolyte outflow path connected to an outlet of the first chamber or the second chamber; a low-level electrolyte tank connected to the electrolyte outflow path at a position lower than that of the high-level electrolyte tank; Equipped with a head difference between a liquid level of the first electrolytic solution or the second electrolytic solution in the higher-level electrolyte tank and the at least one cell causes the first electrolytic solution or the second electrolytic solution to flow from the higher-level electrolyte tank through the electrolyte flow path into the first chamber or the second chamber, At least one of the first electrolytic solution distribution device and the second electrolytic solution distribution device is an electrolyte inlet path communicating the lower level electrolyte tank with the inlet of the first chamber or the second chamber; a circulation pump provided in the electrolyte inflow path; an electrolyte transfer path that communicates the lower level electrolyte tank and the higher level electrolyte tank; a booster pump provided in the electrolyte transfer path; A redox flow battery comprising:

2. 2. The redox flow battery according to claim 1, further comprising a communication pipe that communicates the gas phase of the upper electrolyte tank with the gas phase of the lower electrolyte tank.

3. 3. The redox flow battery according to claim 1, wherein the lower electrolyte tank is buried underground.

4. 4. The redox flow battery according to claim 1, wherein the upper electrolyte tank is provided above ground, and the at least one cell is provided in a basement.

5. 5. The redox flow battery according to claim 1, wherein the high-level electrolyte tank is provided on the ground and is provided with a shielding member that blocks direct sunlight from hitting the high-level electrolyte tank.

6. 6. The redox flow battery according to claim 1, wherein the at least one cell includes a plurality of cells arranged in parallel with respect to a flow direction of the first electrolytic solution or the second electrolytic solution from the higher-level electrolyte tank.

7. The redox flow battery according to any one of claims 1 to 6, wherein a flow rate control valve is provided in the electrolyte flow path.

8. The redox flow battery according to any one of claims 1 to 7; Power generation equipment and Equipped with When the power that can be supplied from the power generation device reaches a preset threshold, the power supply system supplies the first electrolytic solution or the second electrolytic solution from the high-level electrolyte tank to the first chamber or the second chamber, thereby discharging the redox flow battery.

9. The redox flow battery according to any one of claims 1 to 7; Power supply device and Equipped with a power supply system that, when power supply from the power supply device is stopped, supplies the first electrolytic solution or the second electrolytic solution from the high-level electrolyte tank to the first chamber or the second chamber to discharge the redox flow battery.

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