Water electrolysis device, control method, and program

Abstract

This water electrolysis device comprises: a water electrolysis stack that has a water electrolysis cell having a solid polymer electrolyte membrane disposed between a pair of separators, and that electrolyzes an electrolytic solution by using the water electrolysis cell; a power supply unit that is electrically connected to the water electrolysis stack; an electrolytic solution path that circulates and supplies the electrolytic solution to the water electrolysis cell; a first temperature sensor that is capable of measuring an inlet temperature of the electrolytic solution flowing through an inlet of the water electrolysis stack; a second temperature sensor that is capable of measuring flow-path outlet temperatures of the electrolytic solution flowing through outlets of a plurality of flow paths formed in electrolysis units of the separators; and a control unit that performs, on the basis of the inlet temperature from the first temperature sensor and the flow-path outlet temperatures from the second temperature sensor, control on the electrolysis units to regulate at least one of the flow rate, temperature, and electric current of the electrolytic solution so as to lower a temperature that has increased in a portion of the electrolysis units of the separators.

Description

Water electrolysis device, control method and program

[0001] The present disclosure relates to a water electrolysis device, a control method, and a program.

[0002] A water electrolysis device electrolyzes water in water electrolysis cells to produce oxygen and hydrogen. Patent Literature 1 discloses a water electrolysis system that measures the temperature of water electrolysis stacks or the temperature of water discharged from the water electrolysis stacks, and adjusts the temperature of water supplied to multiple water electrolysis stacks using a cooler.

[0003] International Publication No. 2023 / 012944

[0004] In order to improve the electrolysis performance of a water electrolysis device, it is necessary to increase the temperature of the electrolyte circulating in the water electrolysis cell, but the water electrolysis device must suppress the temperature of the electrolyte to be equal to or lower than the heat-resistant temperature of the electrolyte membrane, such as an anion exchange membrane, used in the water electrolysis cell.

[0005] The present disclosure is devised to solve the above-described problems, and aims to provide a water electrolysis device, a control method, and a program that can prevent damage to an electrolyte membrane even when the temperature of the electrolytic solution is increased.

[0006] The water electrolysis device according to the present disclosure includes a water electrolysis stack having a water electrolysis cell with a solid polymer electrolyte membrane disposed between a pair of separators and electrolyzing an electrolyte solution using the water electrolysis cell; a power supply unit electrically connected to the water electrolysis stack; an electrolyte solution path for circulating and supplying the electrolyte solution to the water electrolysis cell; a first temperature sensor capable of measuring an inlet temperature of the electrolyte solution flowing through an inlet of the water electrolysis stack; a second temperature sensor capable of measuring flow path outlet temperatures of the electrolyte solution flowing through outlets of a plurality of flow paths formed in an electrolysis section of the separator; and a control unit configured to adjust at least one of the flow rate, temperature, and amount of current of the electrolyte solution to the electrolysis section, based on the inlet temperature measured by the first temperature sensor and the flow path outlet temperatures measured by the second temperature sensor, so as to reduce a temperature that has increased in a part of the electrolysis section of the separator.

[0007] The water electrolysis device according to the present disclosure includes a water electrolysis stack having a water electrolysis cell with a solid polymer electrolyte membrane disposed between a pair of separators and electrolyzing an electrolyte solution using the water electrolysis cell; a power supply unit electrically connected to the water electrolysis stack; an electrolyte solution path for circulating the electrolyte solution to the water electrolysis cell; a first temperature sensor capable of measuring an inlet temperature of the electrolyte solution flowing through an inlet of the water electrolysis stack; a third temperature sensor capable of measuring temperatures of external surfaces of the water electrolysis stack corresponding to outlets of a plurality of flow paths formed in an electrolysis section of the separator; and a control unit configured to adjust at least one of a flow rate, a temperature, and an amount of current of the electrolyte solution to the electrolysis section so as to reduce an elevated temperature in a part of the electrolysis section of the separator, based on flow path outlet temperatures of the electrolyte solution flowing through the outlets of the plurality of flow paths estimated from the inlet temperature and the temperature of the external surface.

[0008] A control method according to the present disclosure is a control method for a water electrolysis device including a water electrolysis stack having a water electrolysis cell with a solid polymer electrolyte membrane disposed between a pair of separators and electrolyzing an electrolyte solution using the water electrolysis cell, a power supply unit electrically connected to the water electrolysis stack, and an electrolyte solution path for circulatingly supplying the electrolyte solution to the water electrolysis cell, the control method including the steps of: measuring an inlet temperature of the electrolyte solution flowing through an inlet of the water electrolysis stack with a first temperature sensor; measuring flow path outlet temperatures of the electrolyte solution flowing through outlets of a plurality of flow paths formed in an electrolysis section of the separator with a second temperature sensor; and adjusting at least one of a flow rate, a temperature, and an amount of current of the electrolyte solution to the electrolysis section based on the inlet temperature and the flow path outlet temperature so as to reduce a temperature that has increased in a part of the electrolysis section of the separator.

[0009] A control method according to the present disclosure is a control method for a water electrolysis device comprising: a water electrolysis stack having a water electrolysis cell with a solid polymer electrolyte membrane disposed between a pair of separators and electrolyzing an electrolyte solution using the water electrolysis cell; a power supply unit electrically connected to the water electrolysis stack; and an electrolyte solution path for circulatingly supplying the electrolyte solution to the water electrolysis cell, the control method including the steps of: measuring an inlet temperature of the electrolyte solution flowing through an inlet of the water electrolysis stack with a first temperature sensor; measuring temperatures of external surfaces of the water electrolysis stack corresponding to outlets of a plurality of flow paths formed in an electrolysis section of the separator with a third temperature sensor; and adjusting at least one of a flow rate, a temperature, and an amount of current of the electrolyte solution to the electrolysis section, based on flow path outlet temperatures of the outlets of the plurality of flow paths estimated from the inlet temperature and the temperature of the external surface, so as to reduce a temperature that has increased in a part of the electrolysis section of the separator.

[0010] The program according to the present disclosure causes a water electrolysis device including a water electrolysis stack having a water electrolysis cell with a solid polymer electrolyte membrane disposed between a pair of separators and electrolyzing an electrolyte solution using the water electrolysis cell, a power supply unit electrically connected to the water electrolysis stack, and an electrolyte solution path for circulatingly supplying the electrolyte solution to the water electrolysis cell, to execute the following steps: measuring, with a first temperature sensor, an inlet temperature of the electrolyte solution flowing through an inlet of the water electrolysis stack; measuring, with a second temperature sensor, flow path outlet temperatures of the electrolyte solution flowing through outlets of a plurality of flow paths formed in an electrolysis section of the separator; and adjusting, based on the inlet temperature and the flow path outlet temperature, at least one of the flow rate, temperature, and amount of current of the electrolyte solution to the electrolysis section so as to reduce a temperature that has increased in a part of the electrolysis section of the separator.

[0011] The program according to the present disclosure causes a water electrolysis device including a water electrolysis stack having a water electrolysis cell with a solid polymer electrolyte membrane disposed between a pair of separators and electrolyzing an electrolyte solution using the water electrolysis cell, a power supply unit electrically connected to the water electrolysis stack, and an electrolyte solution path for circulating the electrolyte solution to the water electrolysis cell to carry out the following steps: measuring, with a first temperature sensor, an inlet temperature of the electrolyte solution flowing through an inlet of the water electrolysis stack; measuring, with a third temperature sensor, temperatures of external surfaces of the water electrolysis stack corresponding to outlets of a plurality of flow paths formed in an electrolysis section of the separator; and adjusting, based on flow path outlet temperatures of the outlets of the plurality of flow paths estimated from the inlet temperature and the temperature of the external surface, at least one of the flow rate, temperature, and amount of current of the electrolyte solution to the electrolysis section so as to reduce an elevated temperature in a part of the electrolysis section of the separator.

[0012] According to the present disclosure, even if the temperature of the electrolyte solution rises, damage to the electrolyte membrane can be prevented in advance.

[0013] FIG. 1 is a schematic diagram showing the general configuration of a water electrolysis device according to a first embodiment. FIG. 2 is an exploded view showing an example of the configuration of a water electrolysis cell. FIG. 3 is a diagram showing an example of the configuration of a separator. FIG. 4 is a diagram showing the configuration of a water electrolysis device according to a first embodiment. ２ 5 is a graph showing the relationship between the temperature difference between the flow path and the cell inlet when the current density of the electrolysis test conditions is 3 A / cm ２FIG. 6 is a graph showing the relationship between the temperature difference between the flow path and the cell inlet in the case of FIG. 6 . FIG. 6 is a partial perspective schematic diagram illustrating an example of the arrangement of temperature sensors in the water electrolysis apparatus. FIG. 7 is a diagram illustrating the functional configuration of the water electrolysis apparatus according to the first embodiment. FIG. 8 is a flowchart showing an example of the processing steps of a control method executed by the water electrolysis apparatus according to the first embodiment. FIG. 9 is a diagram illustrating the functional configuration of a water electrolysis apparatus according to a second embodiment. FIG. 10 is a graph showing the temperatures inside and on the outer surface of a water electrolysis stack. FIG. 11 is a schematic diagram showing an example of a water electrolysis stack in which multiple water electrolysis cells are stacked. FIG. 12 is a flowchart showing an example of the processing steps of a control method executed by the water electrolysis apparatus according to the second embodiment. FIG. 13 is a diagram illustrating the functional configuration of a water electrolysis apparatus according to a third embodiment. FIG. 14 is a graph showing the relationship between the elapsed time after the start of electrolysis and the measured temperature. FIG. 15 is a flowchart showing an example of the processing steps of a control method executed at the start of electrolysis by the water electrolysis apparatus according to the third embodiment.

[0014] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations in which the respective embodiments are combined.

[0015] First Embodiment Overall Configuration of Water Electrolysis Apparatus FIG. 1 is a schematic diagram illustrating the overall configuration of a water electrolysis apparatus according to a first embodiment. As illustrated in FIG. 1 , the water electrolysis apparatus 1 according to the first embodiment includes a water electrolysis cell 11, a power supply unit 12, a first electrolytic solution path 14, a first gas-liquid separation tank 15, an oxygen gas extraction path 16, a second electrolytic solution path 17, a second gas-liquid separation tank 18, a hydrogen gas extraction path 19, an adjustment unit 60, and a control unit 70. The water electrolysis apparatus 1 also includes a first water supply path 41 that pressurizes the electrolytic solution in the first electrolytic solution path 14, and a first water supply valve 42. The electrolytic solution includes an electrolytic solution to be circulated. Furthermore, the water electrolysis apparatus 1 also includes a second water supply path 43 that pressurizes the electrolytic solution in the second electrolytic solution path 17, and a second water supply valve 44.

[0016] The water electrolysis cell 11 is configured in a water electrolysis stack 21, with an anode disposed on one side of a hydrogen ion-permeable solid polymer electrolyte membrane 22 and a cathode disposed on the other side. The solid polymer electrolyte membrane 22 may be, for example, an ion exchange membrane such as an anion exchange membrane. One or more water electrolysis cells 11 are stacked to form the water electrolysis stack 21. The water electrolysis cell 11 electrolyzes the electrolyte solution using the solid polymer electrolyte membrane 22, thereby generating oxygen gas at the anode side 23 and hydrogen gas at the cathode side 24.

[0017] The power supply unit 12 supplies power (current) to the anode and cathode arranged on both sides of the solid polymer electrolyte membrane 22 in the water electrolysis cell 11. The power supply unit 12 may be, for example, a DC power supply or a power supply device that uses natural energy.

[0018] The control unit 70 receives power from the power supply unit 12 and controls the current and voltage of the power supplied to the anode and cathode arranged on both sides of the solid polymer electrolyte membrane 22 of the water electrolysis cell 11, thereby supplying power to the water electrolysis cell 11 to perform water electrolysis and generate oxygen gas and hydrogen gas.

[0019] The first electrolyte solution path 14 circulates the electrolyte through the water electrolysis stack 21 and supplies the electrolyte to the anode side 23 of the water electrolysis cell 11, thereby enabling electrolysis of the electrolyte (water). The first electrolyte solution path 14 is connected to a first gas-liquid separation tank 15. The first electrolyte solution path 14 has an inlet path 14a to the water electrolysis stack 21 and an outlet path 14b from the water electrolysis stack 21. A first circulation pump 31 is provided in the inlet path 14a of the first electrolyte solution path 14. In the present embodiment, the first electrolyte solution path 14 and the first gas-liquid separation tank 15 constitute the first electrolyte solution path.

[0020] The first gas-liquid separation tank 15 separates and extracts oxygen gas present as bubbles or dissolved in the circulating electrolytic solution (water), and is connected to an oxygen gas extraction path 16 for discharging the separated oxygen gas at its top. The first gas-liquid separation tank 15 has a built-in filter 15a, which removes impurities (e.g., eluted metals) generated by the electrolysis of water before supplying the water to the water electrolysis stack 21 again.

[0021] The second electrolytic solution path 17 circulates the electrolytic solution through the water electrolysis stack 21 and supplies the electrolytic solution to the cathode side 24 of the water electrolysis cell 11, thereby cooling the solid polymer electrolyte membrane 22 and extracting hydrogen gas. The second electrolytic solution path 17 is connected to a second gas-liquid separation tank 18. The second electrolytic solution path 17 has an inlet path 17a to the water electrolysis stack 21 and an outlet path 17b from the water electrolysis stack 21. A second circulation pump 32 is provided in the inlet path 17a of the second electrolytic solution path 17. In the present embodiment, the second electrolytic solution path 17 and the second gas-liquid separation tank 18 constitute the second electrolytic solution path.

[0022] The second gas-liquid separation tank 18 separates and extracts hydrogen gas present as bubbles or dissolved in the circulating electrolytic solution (water), and is connected to an upper portion thereof with a hydrogen gas extraction path 19 for discharging the separated hydrogen gas. The second gas-liquid separation tank 18 is provided with a hydrogen control valve 33 on the hydrogen gas extraction path 19. The second gas-liquid separation tank 18 has a built-in filter 18a, which removes impurities generated by the electrolysis of water before supplying the water to the water electrolysis stack 21 again.

[0023] The inlet path 17a of the second electrolyte path 17 is connected to a buffer tank 35 via an auxiliary path 34. The auxiliary path 34 is provided with a water discharge valve 36. The buffer tank 35 is used to temporarily hold the electrolyte depending on the amount of hydrogen gas in the second gas-liquid separation tank 18 in the second electrolyte path 17.

[0024] The first water supply path 41 supplies the electrolytic solution from the outside into the first gas-liquid separation tank 15, thereby controlling the pressure increase in the first electrolytic solution path 14 and the first gas-liquid separation tank 15 on the anode side 23 of the water electrolysis stack 21. The first water supply path 41 is provided with a first water supply valve 42 that adjusts the water supplied to the first gas-liquid separation tank 15. The first water supply path 41 is also provided with a water supply pump (not shown). The electrolytic solution supplied from the first water supply path 41 is a solution in which an ionic substance or the like is dissolved in pure water, but an electrolytic solution in which oxygen gas has been dissolved in advance may also be introduced.

[0025] The second water supply path 43 supplies water from the outside into the second gas-liquid separation tank 18, thereby controlling the pressure increase in the second electrolytic solution path 17 and the second gas-liquid separation tank 18 on the cathode side 24 of the water electrolysis stack 21. The second water supply path 43 is provided with a second water supply valve 44 that adjusts the water supplied to the second gas-liquid separation tank 18. The second water supply path 43 is also provided with a water supply pump (not shown). Although pure water is used as the water supplied from the second water supply path 43, an electrolytic solution in which hydrogen gas has been dissolved in advance may be introduced.

[0026] The adjustment unit 60 is provided near the electrolyte inlets on the anode side 23 and the cathode side 24 of the water electrolysis cell 11, and is configured to be able to adjust the temperature of the electrolyte supplied to the water electrolysis cell 11. The adjustment unit 60 includes, for example, an air-cooled or water-cooled chiller that is able to adjust the temperature of the electrolyte. In the present embodiment, the adjustment unit 60 is provided in the first electrolyte solution path 14 and the second electrolyte solution path 17, and is electrically connected to the control unit 70. The adjustment unit 60 adjusts the increase or decrease in the temperature of the electrolyte supplied to the water electrolysis cell 11 under the control of the control unit 70, thereby maintaining the electrolyte at a constant temperature.

[0027] The control unit 70 can control the current and voltage values ​​to the anode and cathode arranged on both sides of the solid polymer electrolyte membrane 22 of the water electrolysis cell 11, depending on the power of the power supply unit 12. The control unit 70 can adjust and control the discharge pressures (pump motor rotation speeds) of the first circulation pump 31 and the second circulation pump 32, and can adjust and control the apertures (0 to 100%) of the hydrogen control valve 33 and the water discharge valve 36. The control unit 70 can adjust and control the apertures (0 to 100%) of the first water supply valve 42 and the second water supply valve 44. The control unit 70 controls the adjustment unit 60 to adjust the temperature, flow rate, etc. of the electrolytic solution supplied to the water electrolysis cell 11.

[0028] Next, the operation of the water electrolysis apparatus 1 of the first embodiment at startup will be described.

[0029] When an operator turns on the start switch of the water electrolysis apparatus 1, the control unit 70 first opens the first water supply valve 42 and the second water supply valve 44 to supply the electrolyte to the first electrolyte solution path 14 and the second electrolyte solution path 17 of the anode and cathode of the water electrolysis cell 11 via the first water supply path 41 and the second water supply path 43. At the same time, the control unit 70 operates the first circulation pump 31 and the second circulation pump 32 to flow the electrolyte. The control unit 70 starts supplying power to the water electrolysis cell 11 to start the electrolysis reaction in the water electrolysis cell 11. At this time, the control unit 70 closes the hydrogen gas extraction path 19 with the hydrogen control valve 33 to seal the second electrolyte solution path 17. The control unit 70 controls the flow rate of the electrolyte by the first circulation pump 31 and the second circulation pump 32 depending on the current supplied to the water electrolysis cell 11.

[0030] The control unit 70 controls the current and voltage values ​​to the anode and cathode arranged on both sides of the solid polymer electrolyte membrane 22, so that the electrolytic solution in the anode side 23 is electrolyzed by the anode and cathode arranged on both sides of the solid polymer electrolyte membrane 22. That is, when the electrolytic solution is supplied to the anode and cathode arranged on both sides of the solid polymer electrolyte membrane 22 in the anode side 23 of the water electrolysis cell 11, a reaction occurs in the cathode side 24 of the solid polymer electrolyte membrane 22, and hydrogen gas and hydroxide ions (OH － ) is generated. This hydroxide ion (OH －) migrates from the cathode side 24 through the solid polymer electrolyte membrane 22 to the anode side 23, accompanied by water, due to the potential difference between the anode side 23 and the cathode side 24, and reacts in the anode side 23 to generate oxygen gas.

[0031] The control unit 70 monitors the pressure of the electrolyte in the first electrolyte solution path 14 and the second electrolyte solution path 17 of the anode and cathode, and closes the first electrolyte solution path 14 and the second electrolyte solution path 17 when the pressure of the electrolyte reaches a predetermined value. The pressure of the electrolyte in the first electrolyte solution path 14 and the second electrolyte solution path 17 is detected by a pressure sensor (not shown). In this case, in the water electrolysis device 1, the pressure of the electrolyte in the second electrolyte solution path 17 is higher than the steady-state pressure, and therefore hydrogen gas is likely to dissolve in the electrolyte. Therefore, in the water electrolysis device 1, hydrogen gas generated on the cathode side 24 circulates through the second electrolyte solution path 17 while remaining dissolved in the electrolyte.

[0032] In the water electrolysis apparatus 1, as the generated hydrogen gas dissolves in the electrolyte and the amount of dissolved hydrogen increases, the amount of dissolved hydrogen reaches a saturation state within a predetermined time, and no more hydrogen gas will dissolve in the water. Therefore, when the amount of dissolved hydrogen in the electrolyte in the second electrolyte path 17 exceeds the saturation state, the controller 70 opens the hydrogen control valve 33. This increases the pressure in the hydrogen gas extraction path 19 in the water electrolysis apparatus 1, and the amount of hydrogen obtained increases. Then, when the amount of obtained hydrogen exceeds a predetermined amount, the controller 70 maintains a constant aperture of the hydrogen control valve 33. This allows the water electrolysis apparatus 1 to stably obtain a predetermined amount of hydrogen at a predetermined pressure.

[0033] (Configuration of water electrolysis cell) Fig. 2 is an exploded view showing an example configuration of a water electrolysis cell. Fig. 3 is a view showing an example configuration of a separator. Note that, in the example shown in Fig. 2, a single water electrolysis cell 11 is shown for the sake of simplicity, but a configuration in which multiple cells are stacked may also be used.

[0034] 2 , the water electrolysis cell 11 includes a pair of separators 25, 26, a solid polymer electrolyte membrane 22 disposed between the pair of separators 25, 26, and power feeders 27, 28 disposed between the solid polymer electrolyte membrane 22 and the pair of separators 25, 26. The water electrolysis cell 11 further includes a catalyst layer 51 disposed between the power feeder 27 and the solid polymer electrolyte membrane 22 on the anode side 23, and a catalyst layer 52 disposed between the power feeder 28 and the solid polymer electrolyte membrane 22 on the cathode side 24. The catalyst layer 51 is an oxygen electrode catalyst layer for the separator 25 on the anode side 23 (anode side). The catalyst layer 52 is a hydrogen electrode catalyst layer for the separator 26 on the cathode side 24 (cathode side). The water electrolysis cell 11 has a multilayer stack structure in which a separator 25, a power supply 27, a catalyst layer 51, a solid polymer electrolyte membrane 22, a catalyst layer 52, a power supply 28, and a separator 25 are stacked in this order from the anode side 23 to the cathode side 24.

[0035] The pair of separators 25, 26 are formed into rectangular plates from metal members that are impermeable to oxygen and hydrogen produced by water electrolysis. The pair of separators 25, 26 each have an inlet pipe 29a serving as an inlet for the electrolytic solution and an outlet pipe 29b serving as an outlet for the electrolytic solution. The pair of inlet pipes 29a communicate with the inlet passage 14a of the first electrolytic solution path 14 and the inlet passage 17a of the second electrolytic solution path 17, respectively. The pair of outlet pipes 29b communicate with the outlet passage 14b of the first electrolytic solution path 14 and the outlet passage 17b of the second electrolytic solution path 17, respectively.

[0036] 3 , the pair of separators 25, 26 includes a main body 200, an electrolysis section 210 formed in the center of the main body 200, an electrolyte inlet 220 provided on one side of the electrolysis section 210, and an electrolyte outlet 230 provided on the other side of the electrolysis section 210. The pair of separators 25, 26 have the electrolyte inlet 220 and the electrolyte outlet 230 arranged diagonally across the main body 200, with the electrolysis section 210 provided therebetween. The main body 200 is formed with two opposing fixing sections 201, and is fixed in a stacked position by a fixing member penetrating the fixing sections 201.

[0037] The electrolysis unit 210 is a partial area on the plane of the main body 200, and is an area where the power supply elements 27, 28 are stacked (contacted). The electrolysis unit 210 has a plurality of flow paths 211 for flowing the electrolytic solution (pure water) to be electrolyzed outside the power supply elements 27, 28. The plurality of flow paths 211 are arranged at equal intervals along the width direction W of the separators 25, 26, and are formed as a plurality of grooves extending along the longitudinal direction F. The plurality of flow paths 211 are portions in the electrolysis unit 210 through which the electrolytic solution and gas flow. The longitudinal direction F is the direction in which the electrolytic solution flows in the electrolysis unit 210, and is perpendicular to the width direction W. In the plurality of flow paths 211, the flow rate of the electrolytic solution is faster the closer to the electrolyte solution inlet 220, and the slower the further away from the electrolyte solution inlet 220, the faster the flow rate of the electrolytic solution.

[0038] The electrolyte inlet 220 is a hole formed near one corner of the electrolysis unit 210 in an area 200A on one side of the area surrounding the electrolysis unit 210 of the main body 200, and is connected to the inlet pipe 29a of the separator 25 or the separator 26. The electrolyte inlet 220 supplies the electrolyte from the inlet pipe 29a to all of the multiple flow paths 211 of the electrolysis unit 210.

[0039] The electrolyte outlet 230 is a hole formed in the other region 200B of the main body 200 surrounding the electrolysis unit 210, near the other corner of the electrolysis unit 210, so as to face the electrolyte inlet 220, and is connected to the outlet pipe 29b of the separator 25 or the separator 26. The electrolyte outlet 230 discharges the electrolyte that has flowed through the multiple flow paths 211 of the electrolysis unit 210 and joined together, to the outlet pipe 29b.

[0040] The pair of separators 25, 26 surround the electrolysis unit 210, the electrolyte inlet 220, and the electrolyte outlet 230 with packing 240, thereby restricting the area through which the electrolyte flows. As a result, the pair of separators 25, 26 improve the efficiency of supplying the electrolyte from the electrolyte inlet 220 to the electrolysis unit 210 and discharging the electrolyte from the electrolysis unit 210 to the electrolyte outlet 230 through the packing 240.

[0041] The pair of separators 25, 26 are configured such that the electrolyte from the electrolyte inlet 220 flows in flow directions L1, L2, L3, etc., and then splits into multiple flow paths 211 of the electrolysis unit 210. The pair of separators 25, 26 allows the electrolyte to flow through each of the multiple flow paths 211, and the electrolyte that has passed through the outlets of the multiple flow paths 211 joins together again and flows into the electrolyte outlet 230. The electrolyte in the flow direction L1 flows faster than the electrolyte in the flow direction L2. The electrolyte in the flow direction L2 flows faster than the electrolyte in the flow direction L3.

[0042] The power feeders 27, 28 are made of a metal mesh and are formed so as to be stackable with the electrolysis section 210 of the separators 25, 26 and the catalyst layers 51, 52. The power feeders 27, 28 are configured to receive power from the power supply unit 12 via end plates arranged outside the water electrolysis cell 11.

[0043] (Water Electrolysis Reaction in Water Electrolysis Cell) As shown in FIG. 2 , the water electrolysis cell 11 is configured such that an electrolyte (H ２ O) is supplied to the water electrolysis cell 11, and a voltage is applied to the power feeders 27 and 28. In the cathode side 24 of the water electrolysis cell 11, the electrolyte (H ２ O) reacts in the catalyst layer 52, causing a reduction reaction of water, and the electrolyte (H ２ O) to hydrogen (H ２ ) and hydroxide ions (OH － ) is generated, and hydroxide ions (OH － ) moves through the solid polymer electrolyte membrane 22 toward the anode side 23. ２ O + 2e － → H ２ +2OH － ...(Formula 1)

[0044] The water electrolysis cell 11 converts hydroxide ions (OH ) that have migrated through the solid polymer electrolyte membrane 22 into hydrogen at the anode side 23, as shown in the anode reaction represented by the following formula (2): － ) in the catalyst layer 51. ２ ) and water (H ２ O) is generated. －→ 1 / 2O ２ +H ２ O + 2e － ...(Formula 2)

[0045] The overall reaction from (Equation 1) and (Equation 2) produces oxygen and hydrogen from water as shown in (Equation 3) below: H ２ O → H ２ +1 / 2O ２ ...(Formula 3)

[0046] The water electrolysis cell 11 has a separator 25 on the anode side 23 that is filled with an oxygen-containing electrolyte (O ２ +H ２ O) is discharged from the outlet pipe portion 29b, and the separator 26 on the cathode side 24 is filled with the hydrogen-containing electrolyte (H ２ +H ２ O) is discharged from the outlet pipe portion 29b.

[0047] In the water electrolysis device 1, the temperature of the electrolyte needs to be increased to improve the performance of the water electrolysis cell 11, but if the solid polymer electrolyte membrane 22 is an anion exchange membrane, the temperature needs to be kept below its heat-resistant temperature. In this embodiment, the water electrolysis device 1 realizes a technology for suppressing an increase in the temperature of the solid polymer electrolyte membrane 22 and improving the performance of the water electrolysis cell 11.

[0048] (Separator Flow Channels) Next, we will describe the results of an electrolysis test using model separators of the separators 25 and 26 that use the water electrolysis cell 11. The model separators differ from the actual separators 25 and 26 in the width and number of flow channels 211 (grooves).

[0049] FIG. 4 shows the electrolysis test conditions when the current density was 1 A / cm ２ 5 is a graph showing the relationship between the temperature difference between the flow path and the cell inlet when the current density of the electrolysis test conditions is 3 A / cm ２ 10 is a graph showing the relationship between the temperature difference between the flow path and the cell inlet in the case of the current density being the amount of electricity (charge) flowing per unit time in the direction perpendicular to the unit area in the current feeder 27 and the current feeder 28.

[0050] 4 and 5 show the results of measurements of the outlet temperatures of the multiple flow paths 211 in the separator 26 on the cathode side 24 of the water electrolysis cell 11 using a temperature sensor. The flow path outlet temperatures are temperatures measured near the outlets of the flow paths 211 through which the electrolyte flows. In FIGS. 4 and 5 , the vertical axis shows the temperature difference (°C) between the inlet temperature of the separator 26 and the outlet temperatures of the multiple flow paths 211. In FIGS. 4 and 5 , the horizontal axis shows the flow path numbers assigned to the multiple flow paths 211 in the width direction W of the electrolysis unit 210, from one side near the electrolyte inlet 220 to the other side away from the inlet 220. FIGS. 4 and 5 show the results of measurements at four measurement points on a model separator, corresponding to points P1 to P4 near the outlets of the flow paths 211 shown in FIG. 3 .

[0051] Graphs G11 and G13 shown in FIG. 4 show that the current density of the electrolysis test conditions is 1 A / cm ２ 4 shows the temperature difference between the inlet temperature of the separator 26 and the outlet temperatures of the flow paths 211 measured at four measurement points near the outlets of the flow paths 211 when the flow rate of the electrolyte solution to the water electrolysis cell 11 is changed to 0.8 kg / (min-cell) and 1.5 kg / (min-cell). That is, the flow rate of the electrolyte solution decreases in the order of graphs G13 and G11. The measurement results shown in FIG. 4 indicate that the influence of heat radiation from the electrolysis section 210 of the separator 26 is significant, resulting in a large temperature difference on the outside in the width direction W. The measurement results shown in FIG. 4 show that the outlet temperatures of the multiple flow paths 211 are lower than the inlet temperatures of the separator 26, resulting in a negative temperature difference.

[0052] Graphs G31 and G32 shown in FIG. 5 show the results when the current density of the electrolysis test conditions was 3 A / cm ２ 5 shows the temperature difference between the inlet temperature of the separator 26 and the outlet temperatures of the flow paths 211 measured at four measurement points near the outlets of the flow paths 211 when the flow rate of the electrolyte to the water electrolysis cell 11 is changed to 1.5 kg / (min-cell) and 3.0 kg / (min-cell). That is, the flow rate of the electrolyte decreases in the order of graphs G32 and G31. The measurement results shown in FIG. 5 show that the maximum temperature difference in the width direction W of the electrolysis section 210 of the separator 26 is 13°C, and the temperature difference increases as the flow rate of the electrolyte decreases.

[0053] As described above, the results of the electrolysis test revealed that the temperature distribution (temperature difference) in the width direction W of the separator 26 of the water electrolysis cell 11 tends to increase as the current density increases. Specifically, it was found that the electrolysis section 210 of the separators 25, 26 has a temperature distribution, and this temperature distribution changes depending on the current density. For example, if the separator temperature of the electrolysis section 210 of the separators 25, 26 increases locally, it may be impossible to detect an abnormality by simply measuring the electrolyte temperature at the stack outlet of the water electrolysis stack 21. As a result, the water electrolysis device 1 according to this embodiment suppresses an increase in the temperature of the solid polymer electrolyte membrane 22, thereby improving the performance of the water electrolysis cell 11 and preventing damage to the solid polymer electrolyte membrane 22. Specifically, the water electrolysis device 1 measures the temperature of the electrolyte near the outlet of the flow path 211 of the water electrolysis cell 11 at multiple locations, and, if a local temperature increase occurs, controls the temperature of the electrolyte to prevent damage to the solid polymer electrolyte membrane 22.

[0054] (Temperature Sensor of Water Electrolysis Apparatus) Fig. 6 is a partial perspective schematic diagram illustrating an example of the arrangement of a temperature sensor of the water electrolysis apparatus. Fig. 7 is a diagram illustrating the functional configuration of the water electrolysis apparatus according to the first embodiment. In Fig. 6, the flow direction of the electrolytic solution is the direction L indicated by the arrow.

[0055] 6 , the water electrolysis cell 11 is sandwiched between end plates 20 on both sides, and an inlet channel 14a and an outlet channel 14b are connected to the end plate 20 on the anode side 23, and an inlet channel 17a and an outlet channel 17b are connected to the end plate 20 on the cathode side 24. In this embodiment, when the solid polymer electrolyte membrane 22 of the water electrolysis cell 11 is an anion exchange membrane and the heat resistance temperature of the anion exchange membrane is, for example, 80°C, the water electrolysis apparatus 1 adjusts the temperature of the electrolytic solution so that the inlet temperature of the water electrolysis cell 11 is 75.5°C or lower.

[0056] The water electrolysis apparatus 1 further includes a first temperature sensor 81 that measures the inlet temperature of the electrolyte flowing into the inlet of the water electrolysis stack 21, and a second temperature sensor 82 that measures the outlet temperature of the electrolyte flowing through the outlets of the multiple flow paths 211 formed in the electrolysis unit 210 of the separators 25, 26. The first temperature sensor 81 is provided in the inlet paths 14a, 17a of the water electrolysis cell 11 to the water electrolysis stack 21, and is electrically connected to the controller 70. The second temperature sensor 82 is provided at the outlet of the flow path 211 of the separators 25, 26 of the water electrolysis cell 11, and is electrically connected to the controller 70. The first temperature sensor 81 and the second temperature sensor 82 may be, for example, a thermistor, a resistance temperature detector, or a thermocouple. The first temperature sensor 81 and the second temperature sensor 82 supply temperature information that enables the measured temperatures of the electrolyte to be identified to the controller 70.

[0057] In the example shown in FIG. 7, the water electrolysis apparatus 1 includes a controller 70, a first temperature sensor 81, and a second temperature sensor 82; other components are omitted.

[0058] The second temperature sensors 82 include second temperature sensors 82a, 82b, and 82c. The second temperature sensor 82a measures the temperature at the flow path outlet in the flow direction L1 in the electrolysis section 210 of the separators 25, 26. The second temperature sensor 82b measures the temperature at the flow path outlet in the flow direction L2 in the electrolysis section 210 of the separators 25, 26. The second temperature sensor 82c measures the temperature at the flow path outlet in the flow direction L3 in the electrolysis section 210 of the separators 25, 26. In the following description, when it is not necessary to distinguish between the second temperature sensors 82a, 82b, and 82c, they will be simply referred to as the second temperature sensor 82.

[0059] The control unit 70 is a computing device, i.e., a CPU (Central Processing Unit). The control unit 70 realizes various functions and executes the processes by reading and executing programs (software) from the storage unit 72. The control unit 70 may execute processes using a single CPU, or may be provided with multiple CPUs and execute processes using the multiple CPUs. In this embodiment, the control unit 70 is electrically connected to the storage unit 72, but the control unit 70 may also be configured to include the storage unit 72 built in.

[0060] The storage unit 72 is a memory that stores various information such as the calculation contents and programs of the control unit 70, and includes, for example, at least one of a RAM, a main storage device such as a ROM, and an external storage device such as an HDD. The storage unit 72 can store a program 721, temperature information 722, etc. The program 721 includes a program for implementing control of water electrolysis in the water electrolysis device 1. The temperature information 722 includes information that can identify the inlet temperature of the first temperature sensor 81 and the flow path outlet temperatures T1, T2, T3, etc. of the multiple second temperature sensors 82. The flow path outlet temperature T1 is the temperature measured by the second temperature sensor 82a. The flow path outlet temperature T2 is the temperature measured by the second temperature sensor 82b. The flow path outlet temperature T3 is the temperature measured by the second temperature sensor 82c. The storage unit 72 stores the multiple pieces of temperature information 722 in chronological order. The chronological temperature information 722 can identify changes in temperature distribution, high temperature regions, etc. in the electrolysis section 210 of the separators 25 and 26 based on the flow path outlet temperatures of the multiple second temperature sensors 82.

[0061] The control unit 70 adjusts the temperature of the electrolysis unit 210 of the separators 25, 26 based on the inlet temperature of the first temperature sensor 81 and the flow path outlet temperature of the second temperature sensor 82 so as to reduce a temperature rise in the electrolysis unit 210. The control unit 70 estimates the temperature distribution of the electrolysis unit 210 of the separators 25, 26 based on the inlet temperature of the first temperature sensor 81 and the flow path outlet temperature of the second temperature sensor 82, and extracts regions in the electrolysis unit 210 where the temperature is locally rising. The control unit 70 controls the temperature of the electrolyte so that the temperature of the electrolysis unit 210 of the separators 25, 26 is equal to or lower than the heat resistance temperature of the solid polymer electrolyte membrane 22. The control unit 70 controls the adjustment unit 60 based on the inlet temperature of the first temperature sensor 81 and the flow path outlet temperature of the second temperature sensor 82 so that the temperature of the electrolysis unit 210 of the separators 25, 26 is equal to or lower than the heat resistance temperature of the solid polymer electrolyte membrane 22.

[0062] (Control method of water electrolysis apparatus according to first embodiment) Fig. 8 is a flowchart showing an example of the processing steps of the control method executed by the water electrolysis apparatus according to first embodiment. The processing steps shown in Fig. 8 are realized by the control unit 70 of the water electrolysis apparatus 1 executing the program 721.

[0063] 8 , the control unit 70 of the water electrolysis apparatus 1 measures flow path outlet temperatures T1, T2, and T3 in the electrolysis unit 210 of the separators 25 and 26 (step S101). For example, the control unit 70 obtains the flow path outlet temperatures T1, T2, and T3 measured by the second temperature sensor 82 and stores them in the storage unit 72 as temperature information 722. After completing step S101, the control unit 70 proceeds to step S102.

[0064] The control unit 70 determines whether the flow channel outlet temperatures T1, T2, and T3 are equal to or higher than the first heat resistance temperature (step S102). For example, if the first heat resistance temperature of the solid polymer electrolyte membrane 22 is 80° C., the control unit 70 determines that the flow channel outlet temperatures T1, T2, and T3 are equal to or higher than the first heat resistance temperature if all of the flow channel outlet temperatures T1, T2, and T3 are equal to or higher than 80° C. If the control unit 70 determines that the flow channel outlet temperatures T1, T2, and T3 are equal to or higher than the first heat resistance temperature (Yes in step S102), the control unit 70 proceeds to step S103.

[0065] The control unit 70 reduces the amount of current or stops the electrolysis operation (step S103). For example, the control unit 70 reduces the amount of current (current density) because the flow path outlet temperatures T1, T2, and T3 are equal to or higher than the first heat-resistant temperature. Alternatively, the control unit 70 stops the electrolysis operation of the water electrolysis device 1. As a result, the water electrolysis device 1 reduces the amount of current or stops the electrolysis operation because the temperature of the electrolysis unit 210 as a whole is equal to or higher than the first heat-resistant temperature. When the process of step S103 is completed, the control unit 70 proceeds to step S109, which will be described later.

[0066] Furthermore, if the control unit 70 determines that the flow channel outlet temperatures T1, T2, and T3 are not equal to or higher than the first heat resistance temperature (No in step S102), the control unit 70 proceeds to step S104. The control unit 70 then determines whether the flow channel outlet temperatures T1, T2, and T3 are equal to or higher than the second heat resistance temperature (step S104). For example, if the second heat resistance temperature of the solid polymer electrolyte membrane 22 is 75°C, which is lower than the first heat resistance temperature, the control unit 70 determines that the flow channel outlet temperatures T1, T2, and T3 are equal to or higher than the second heat resistance temperature if all of the flow channel outlet temperatures T1, T2, and T3 are equal to or higher than 75°C. If the control unit 70 determines that the flow channel outlet temperatures T1, T2, and T3 are not equal to or higher than the second heat resistance temperature (No in step S104), the flow channel outlet temperatures T1, T2, and T3 are normal, and the control unit 70 proceeds to step S110, which will be described later. Furthermore, when the control unit 70 determines that the flow path outlet temperatures T1, T2, and T3 are equal to or higher than the second heat resistance temperature (Yes in step S104), the control unit 70 proceeds to step S105.

[0067] The control unit 70 determines whether the flow path outlet temperature T2 is equal to or greater than the flow path outlet temperature T1 or whether the flow path outlet temperature T3 is equal to or greater than the flow path outlet temperatures T1, T2 (step S105). For example, if the flow path outlet temperature T2 is equal to or greater than the flow path outlet temperature T1 or whether the flow path outlet temperature T3 is equal to or greater than the flow path outlet temperatures T1, T2, there is a possibility that a plurality of flow paths 211 are partially blocked in the electrolysis unit 210 of the separators 25, 26. Thus, the control unit 70 can determine whether the flow path outlet temperature T2 is equal to or greater than the flow path outlet temperature T1 or whether the flow path outlet temperature T3 is equal to or greater than the flow path outlet temperatures T1, T2, thereby determining whether the flow paths 211 are blocked in the electrolysis unit 210 of the separators 25, 26.

[0068] If the control unit 70 determines that the flow path outlet temperature T2 is equal to or greater than the flow path outlet temperature T1 or the flow path outlet temperature T3 is equal to or greater than the flow path outlet temperatures T1, T2 (Yes in step S105), the control unit 70 proceeds to step S106. That is, if the flow path 211 is blocked, the electrolyte solution does not easily flow through the blocked flow path 211 even if the flow rate of the electrolyte solution is increased. Therefore, the control unit 70 proceeds to step S106. The control unit 70 lowers the temperature of the electrolyte solution (step S106). For example, the control unit 70 controls the adjustment unit 60 to lower the temperature of the electrolyte solution to a desired temperature based on the inlet temperature of the separator 26 measured by the first temperature sensor 81 and the flow path outlet temperatures of the multiple flow paths 211 measured by the second temperature sensor 82. As a result, the water electrolysis device 1 lowers the temperature of the electrolysis unit 210 by lowering the temperature of the electrolyte solution, since the temperature of the electrolysis unit 210 is locally high. When the process of step S106 ends, the control unit 70 advances the process to step S109, which will be described later.

[0069] Furthermore, if the control unit 70 determines that the flow path outlet temperature T2 is not equal to or greater than the flow path outlet temperature T1 or the flow path outlet temperature T3 is not equal to or greater than the flow path outlet temperatures T1 and T2 (No in step S105), the control unit 70 proceeds to step S107. The control unit 70 determines whether the flow rate of the electrolytic solution has reached its upper limit (step S107). For example, if many of the water electrolysis stacks 21 have high temperatures due to aging of the solid polymer electrolyte membrane 22 or the like, the water electrolysis device 1 needs to lower the temperatures of the water electrolysis stacks 21. For this reason, the water electrolysis device 1 determines whether the flow rate of the electrolytic solution has reached its upper limit.

[0070] If the control unit 70 determines that the flow rate of the electrolyte solution flowing through the water electrolysis cell 11 has reached the upper limit (Yes in step S107), the control unit 70 proceeds to step S106, which has already been described. The control unit 70 then reduces the temperature of the electrolyte solution (step S106). After step S106 is completed, the control unit 70 proceeds to step S109, which will be described later.

[0071] Furthermore, if the control unit 70 determines that the flow rate of the electrolyte solution flowing through the water electrolysis cell 11 has not reached the upper limit (No in step S107), the control unit 70 proceeds to step S108. The control unit 70 increases the flow rate of the electrolyte solution (step S108). For example, the control unit 70 opens the first water supply valve 42 and the second water supply valve 44 to increase the flow rate of the electrolyte solution supplied to the water electrolysis stack 21 via the first water supply path 41 and the second water supply path 43, so as to lower the temperature of the water electrolysis stack 21. As a result, since the temperature of the electrolysis unit 210 is locally high, the water electrolysis device 1 increases the flow rate of the electrolyte solution to lower the temperature of the electrolysis unit 210. When step S108 is completed, the control unit 70 proceeds to step S109.

[0072] The control unit 70 confirms a decrease in the temperature of the electrolyte (step S109). For example, the control unit 70 confirms that the temperature of the electrolyte has decreased to a desired temperature based on the inlet temperature of the separator 26 measured by the first temperature sensor 81 and the flow path outlet temperatures of the multiple flow paths 211 measured by the second temperature sensor 82. When the control unit 70 confirms a decrease in the temperature of the electrolyte, the process proceeds to step S110.

[0073] The control unit 70 determines whether or not to terminate the process (step S110). For example, the control unit 70 determines to terminate the process when a termination condition, such as the termination of water electrolysis or an external termination instruction, is met. If the control unit 70 determines not to terminate the process (No in step S110), the process continues by returning to step S101, which has already been described. If the control unit 70 determines to terminate the process (Yes in step S110), the control unit 70 terminates the processing procedure shown in FIG. 8.

[0074] In this way, the water electrolysis device 1 measures the flow path outlet temperatures at different locations using the second temperature sensor 82, and adjusts the inlet temperatures of the pair of separators 25, 26 to control the temperature of the electrolysis unit 210 to be equal to or lower than the heat resistance temperature of the solid polymer electrolyte membrane 22. In this way, when a local temperature rise occurs in the electrolysis unit 210 of the pair of separators 25, 26, the water electrolysis device 1 can adjust the temperature of the electrolyte to prevent damage to the solid polymer electrolyte membrane 22 due to a rise in temperature. As a result, the water electrolysis device 1 can increase the temperature of the electrolyte, thereby improving water electrolysis performance.

[0075] Furthermore, in the water electrolysis device 1, even if the temperature rises locally in the electrolysis section 210 of the pair of separators 25, 26, the temperature of the electrolysis section 210 can be kept below the heat resistance temperature of the solid polymer electrolyte membrane 22, thereby reliably preventing damage to the solid polymer electrolyte membrane 22.

[0076] Second Embodiment Next, a second embodiment will be described. In the second embodiment, the water electrolysis apparatus 1 has the same basic configuration as the first embodiment, but the temperature measurement locations are different from those in the first embodiment. In the second embodiment, descriptions of parts that are common to the first embodiment will be omitted. The water electrolysis apparatus 1 according to the second embodiment includes a water electrolysis cell 11, a power supply unit 12, a first electrolytic solution path 14, a first gas-liquid separation tank 15, an oxygen gas extraction path 16, a second electrolytic solution path 17, a second gas-liquid separation tank 18, a hydrogen gas extraction path 19, an adjustment unit 60, and a control unit 70.

[0077] Fig. 9 is a diagram illustrating the functional configuration of a water electrolysis apparatus according to the second embodiment. As shown in Fig. 9, the water electrolysis apparatus 1 according to the second embodiment further includes a first temperature sensor 81 and a third temperature sensor 83 for measuring the temperature distribution near the outlet of the flow path 211 in the electrolysis unit 210 of the separators 25, 26, and the other components described above are omitted.

[0078] The third temperature sensor 83 is a temperature sensor capable of measuring the temperature of the outer surface of the water electrolysis stack 21 corresponding to the outlets of the multiple flow paths 211 formed in the electrolysis unit 210 of the separators 25, 26. The water electrolysis stack 21 is formed of a thermally conductive material, and heat is transferred from the electrolysis unit 210 of the separators 25, 26 to the third temperature sensor 83. The third temperature sensor 83 is provided on the outer surface of the water electrolysis stack 21 corresponding to the vicinity of the outlets of the flow paths 211 of the electrolysis unit 210 of the separators 25, 26, and is electrically connected to the controller 70. The third temperature sensor 83 may be, for example, a thermistor, a resistance temperature detector, or a thermocouple. The third temperature sensor 83 supplies the controller 70 with temperature information 722 that identifies the measured temperature of the outer surface of the water electrolysis stack 21.

[0079] Fig. 10 is a graph showing the temperatures inside and on the outer surface of the water electrolysis stack 21. In Fig. 10, the vertical axis represents the temperature inside the water electrolysis stack 21, and the horizontal axis represents the temperature on the outer surface of the water electrolysis stack 21.

[0080] 10 shows the relationship between the internal temperature of the water electrolysis stack 21 measured by the second temperature sensor 82a and the external surface temperature measured by the third temperature sensor 83. As shown in graph G41, the maximum temperature difference between the temperature near the outlet of the flow path 211 on the outside of the water electrolysis stack 21 and the temperature near the outlet of the flow path 211 of the separators 25, 26 inside the water electrolysis stack 21 is 7°C. In other words, graph G41 shows that there is a proportional relationship between the external surface temperature measured by the third temperature sensor 83 and the internal temperature of the water electrolysis stack 21.

[0081] By storing estimation information 723 corresponding to graph G41 in the storage unit 72, the water electrolysis apparatus 1 can estimate the temperatures near the outlets of the flow paths 211 in the electrolysis unit 210 of the separators 25, 26 from the external surface temperatures measured by the third temperature sensor 83. The estimation information 723 includes information for estimating the flow path outlet temperatures of the plurality of flow paths 211, the temperature distribution near the outlets, etc. from the external surface temperatures of the water electrolysis stack 21. For example, the estimation information 723 includes a lookup table for estimating the flow path outlet temperatures of the plurality of flow paths 211, the temperature distribution near the outlets, etc. from the external surface temperatures of the water electrolysis stack 21. For example, the estimation information 723 includes information on a machine learning model that outputs the flow path outlet temperatures of the plurality of flow paths 211, the temperature distribution near the outlets, etc. in response to input of the external surface temperatures of the water electrolysis stack 21.

[0082] Fig. 11 is a schematic diagram illustrating an example of a water electrolysis stack 21 in which multiple water electrolysis cells 11 are stacked. As shown in Fig. 11 , the water electrolysis stack 21 includes multiple (e.g., 30) water electrolysis cells 11 stacked in a stacking direction H, with end plates 20 sandwiching each cell on both sides. In the example illustrated in Fig. 11 , the water electrolysis stack 21 has a high electrolyte flow rate in the water electrolysis cells 11 near the center in the stacking direction H and a low electrolyte flow rate in the water electrolysis cells 11 near the end plates 20. For this reason, the water electrolysis device 1 includes third temperature sensors 83 at three locations in the stacking direction H of the water electrolysis cells 11: near the end plates 20 and at the center. However, the number of third temperature sensors 83 can be determined based on, for example, the number of water electrolysis cells 11, the temperature and flow rate characteristics, etc.

[0083] The water electrolysis apparatus 1 stores in the storage unit 72 estimation information 723 corresponding to the water electrolysis cells 11 provided with the plurality of third temperature sensors 83. This enables the water electrolysis apparatus 1 to estimate the temperature distribution near the outlets of the flow paths 211 in the electrolysis units 210 of the water electrolysis cells 11 at different locations in the stacking direction H of the water electrolysis stack 21, from the external surface temperatures measured by the plurality of third temperature sensors 83.

[0084] (Control method of water electrolysis apparatus according to second embodiment) Fig. 12 is a flowchart showing an example of the processing steps of the control method executed by the water electrolysis apparatus according to the second embodiment. The processing steps shown in Fig. 12 are realized by the control unit 70 of the water electrolysis apparatus 1 executing a program 721. In the processing steps shown in Fig. 12, steps S102 to S110 are the same as steps S102 to S110 shown in Fig. 8.

[0085] 12 , the control unit 70 of the water electrolysis apparatus 1 measures the temperature of the outer surface of the water electrolysis stack 21 using the third temperature sensor 83 (step S121). For example, the control unit 70 obtains the outer surface temperature measured by the third temperature sensor 83 and stores it as temperature information 722 in the storage unit 72. After completing the process of step S121, the control unit 70 proceeds to step S122.

[0086] The control unit 70 estimates flow path outlet temperatures T1, T2, and T3 in the electrolysis unit 210 of the separators 25 and 26 based on the temperatures of the outer surfaces (step S122). For example, the control unit 70 estimates flow path outlet temperatures T1, T2, and T3 in the electrolysis unit 210 based on the temperatures of the outer surfaces measured in step S121 and the estimated information 723 in the storage unit 72, and stores the estimated temperatures T1, T2, and T3 in the storage unit 72 as temperature information 722. When the control unit 70 completes the process of step S122, it proceeds to step S102, which has already been described.

[0087] The control unit 70 determines whether the flow path outlet temperatures T1, T2, and T3 are equal to or higher than the first heat resistance temperature (step S102). If the control unit 70 determines that the flow path outlet temperatures T1, T2, and T3 are equal to or higher than the first heat resistance temperature (Yes in step S102), the process proceeds to step S103.

[0088] The control unit 70 reduces the amount of current or stops the electrolysis operation (step S103). After completing the process of step S103, the control unit 70 advances the process to step S109, which will be described later.

[0089] If the control unit 70 determines that the flow path outlet temperatures T1, T2, and T3 are not equal to or higher than the first heat-resistant temperature (No in step S102), the process proceeds to step S104. The control unit 70 determines whether the flow path outlet temperatures T1, T2, and T3 are equal to or higher than the second heat-resistant temperature (step S104). If the control unit 70 determines that the flow path outlet temperatures T1, T2, and T3 are not equal to or higher than the second heat-resistant temperature (No in step S104), the flow path outlet temperatures T1, T2, and T3 are normal, and the process proceeds to step S110, which will be described later. If the control unit 70 determines that the flow path outlet temperatures T1, T2, and T3 are equal to or higher than the second heat-resistant temperature (Yes in step S104), the process proceeds to step S105.

[0090] The control unit 70 determines whether the flow path outlet temperature T2 is equal to or greater than the flow path outlet temperature T1 or whether the flow path outlet temperature T3 is equal to or greater than the flow path outlet temperatures T1 and T2 (step S105). If the control unit 70 determines that the flow path outlet temperature T2 is equal to or greater than the flow path outlet temperature T1 or whether the flow path outlet temperature T3 is equal to or greater than the flow path outlet temperatures T1 and T2 (Yes in step S105), the control unit 70 proceeds to step S106. That is, if the flow path 211 is blocked, even if the flow rate of the electrolyte solution is increased, the electrolyte solution does not flow easily through the blocked flow path 211, so the control unit 70 proceeds to step S106. The control unit 70 reduces the temperature of the electrolyte solution (step S106). After completing step S106, the control unit 70 proceeds to step S109, which will be described later.

[0091] Furthermore, if the control unit 70 determines that the flow path outlet temperature T2 is not equal to or greater than the flow path outlet temperature T1 or the flow path outlet temperature T3 is not equal to or greater than the flow path outlet temperatures T1 and T2 (No in step S105), the control unit 70 proceeds to step S107. The control unit 70 determines whether the flow rate of the electrolyte has reached its upper limit (step S107). If the control unit 70 determines that the flow rate of the electrolyte flowing through the water electrolysis cell 11 has reached its upper limit (Yes in step S107), the control unit 70 proceeds to step S106, which has already been described. The control unit 70 then reduces the temperature of the electrolyte (step S106). After step S106 is completed, the control unit 70 proceeds to step S109, which will be described later.

[0092] If the control unit 70 determines that the flow rate of the electrolyte solution passed through the water electrolysis cell 11 has not reached the upper limit (No in step S107), the control unit 70 proceeds to step S108. The control unit 70 increases the flow rate of the electrolyte solution (step S108). After step S108 is completed, the control unit 70 proceeds to step S109.

[0093] The control unit 70 checks whether the temperature of the electrolytic solution has decreased (step S109). When the control unit 70 checks whether the temperature of the electrolytic solution has decreased, the process proceeds to step S110.

[0094] The control unit 70 determines whether to terminate the process (step S110). If the control unit 70 determines not to terminate the process (No in step S110), the process returns to step S121, which has already been described, to continue the process. If the control unit 70 determines to terminate the process (Yes in step S110), the control unit 70 terminates the process procedure shown in FIG. 12.

[0095] As described above, the water electrolysis apparatus 1 according to the second embodiment uses the third temperature sensor 83 to measure the temperature of the external surface of the water electrolysis stack 21 corresponding to the vicinity of the outlets of the flow paths 211 of the electrolysis units 210 of the separators 25, 26, and estimates the flow path outlet temperatures at multiple locations of the electrolysis units 210 of the separators 25, 26 from the external surface temperature. The water electrolysis apparatus 1 can adjust the temperature of the electrolysis units 210 based on the flow path outlet temperatures at multiple locations to reduce a temperature rise in the electrolysis units of the separators. This allows the water electrolysis apparatus 1 to prevent damage to the solid polymer electrolyte membrane 22 due to a temperature rise by controlling the temperature of the electrolyte when a local temperature rise occurs in the electrolysis units 210 of the pair of separators 25, 26. As a result, the water electrolysis apparatus 1 can increase the temperature of the electrolyte, thereby improving water electrolysis performance. Furthermore, since the water electrolysis device 1 only needs to measure the temperature of the outer surface of the water electrolysis stack 21, there is no need to provide the third temperature sensor 83 in the electrolysis section 210 of the separators 25, 26, which allows for simplification of the device configuration.

[0096] Third Embodiment Next, a third embodiment will be described. In the third embodiment, the water electrolysis apparatus 1 has the same basic configuration as the first embodiment, but differs from the first embodiment in the temperature measurement locations. In the third embodiment, descriptions of parts that are common to the first embodiment will be omitted. The water electrolysis apparatus 1 according to the third embodiment includes a water electrolysis cell 11, a power supply unit 12, a first electrolytic solution path 14, a first gas-liquid separation tank 15, an oxygen gas extraction path 16, a second electrolytic solution path 17, a second gas-liquid separation tank 18, a hydrogen gas extraction path 19, an adjustment unit 60, and a control unit 70.

[0097] Fig. 13 is a diagram illustrating the functional configuration of a water electrolysis apparatus according to a third embodiment. As shown in Fig. 13, the water electrolysis apparatus 1 according to the third embodiment further includes a first temperature sensor 81 and a second temperature sensor 82 for measuring the temperature distribution near the outlet of the flow path 211 in the electrolysis unit 210 of the separators 25, 26; other components are omitted. The second temperature sensor 82 includes a second temperature sensor 82a, a second temperature sensor 82b, and a second temperature sensor 82c.

[0098] FIG. 14 is a graph showing the relationship between the elapsed time after the start of electrolysis and the measured temperature. In FIG. 14, the vertical axis represents the measured temperature (°C), and the horizontal axis represents the elapsed time (min) from the start of electrolysis. FIG. 14 shows the temperature changes of the flow path outlet temperatures T1 and T2 among the flow path outlet temperatures T1, T2, and T3 of the electrolysis unit 210 of the separators 25 and 26. Graph G51a shows the temperature change of the flow path outlet temperature T1 from the start of electrolysis under normal conditions. Graph G51b shows the temperature change of the flow path outlet temperature T1 from the start of electrolysis under abnormal conditions in which the flow path 211 is partially blocked. Graph G52a shows the temperature change of the flow path outlet temperature T2 from the start of electrolysis under normal conditions. Graph G52b shows the temperature change of the flow path outlet temperature T1 from the start of electrolysis under abnormal conditions in which the flow path 211 is partially blocked. 14 , the temperature measured by the second temperature sensor 82 changes differently from the start of electrolysis when the electrolysis unit 210 of the separators 25, 26 is normal and when it is abnormal. Therefore, the water electrolysis device 1 according to the third embodiment can control the water electrolysis operation based on the rate of change over time of the flow path outlet temperature measured at the flow paths 211 of the electrolysis unit 210 of the separators 25, 26.

[0099] 13 , the water electrolysis apparatus 1 stores temperature change information 724, which enables identification of temperature changes from the start of electrolysis in the flow channel outlet temperatures T1, T2, and T3 under normal conditions, in the storage unit 72. The temperature change information 724 includes information that enables identification of temperature changes from the start of electrolysis to the steady-state temperatures in the flow channel outlet temperatures T1, T2, and T3. The temperature change information 724 may also include information that enables identification of temperature changes in the flow channel outlet temperatures T1, T2, and T3 under abnormal conditions.

[0100] (Control method at the start of operation of a water electrolysis apparatus according to the third embodiment) Fig. 15 is a flowchart showing an example of the procedure of a control method at the start of electrolysis executed by a water electrolysis apparatus according to the third embodiment. The procedure shown in Fig. 15 is realized by the control unit 70 of the water electrolysis apparatus 1 executing a program 721.

[0101] 15 , the control unit 70 of the water electrolysis apparatus 1 starts the electrolysis operation (step S200). For example, the control unit 70 opens the first water supply valve 42 and the second water supply valve 44 to supply the electrolyte to the first electrolyte solution path 14 and the second electrolyte solution path 17 of the anode and cathode of the water electrolysis cell 11 via the first water supply path 41 and the second water supply path 43. At the same time, the control unit 70 operates the first circulation pump 31 and the second circulation pump 32 to flow the electrolyte. The control unit 70 starts supplying power to the water electrolysis cell 11 to start the electrolysis reaction in the water electrolysis cell 11. The control unit 70 controls the flow rate of the electrolyte by the first circulation pump 31 and the second circulation pump 32 depending on the current supplied to the water electrolysis cell 11. After step S200 is completed, the control unit 70 proceeds to step S201.

[0102] The control unit 70 continuously measures the flow path outlet temperatures T1, T2, and T3 from the start of electrolysis in the electrolysis unit 210 of the separators 25 and 26 (step S201). For example, the control unit 70 continuously acquires the flow path outlet temperatures T1, T2, and T3 measured by the second temperature sensor 82 and stores them in the storage unit 72 as temperature information 722 until a constant temperature is reached. The control unit 70 calculates the rate of temperature change per time until the constant temperature is reached and sets the rate of temperature change per time in association with the flow path outlet temperatures T1, T2, and T3 in the temperature information 722. When the control unit 70 completes the process of step S201, the process proceeds to step S202.

[0103] The control unit 70 determines whether the temperature change per unit time is abnormal (step S202). For example, the control unit 70 compares the temperature change per unit time of the flow path outlet temperatures T1, T2, and T3 indicated by the temperature information 722 with the temperature change per unit time of the flow path outlet temperatures T1, T2, and T3 indicated by the temperature change information 724 from the start of electrolysis to the steady-state temperature, and if there is a match or dissimilar temperature change, the control unit 70 determines that the temperature change per unit time is abnormal. If the control unit 70 determines that the temperature change per unit time is abnormal (Yes in step S202), the process proceeds to step S203.

[0104] The control unit 70 controls the flow rate of the electrolyte (step S203). For example, the control unit 70 controls the flow rate of the electrolyte by the first circulation pump 31 and the second circulation pump 32 in accordance with the current supplied to the water electrolysis cell 11, thereby controlling the flow rate of the electrolyte based on a predetermined countermeasure. In this way, since the temperature change in the electrolysis unit 210 is abnormal, the water electrolysis device 1 can resolve the abnormality in the electrolysis unit 210 by controlling the flow rate of the electrolyte. After completing the process of step S203, the control unit 70 proceeds to step S208, which will be described later.

[0105] Furthermore, if the control unit 70 determines that the temperature change per unit time is not abnormal (No in step S202), the control unit 70 proceeds to step S204. The control unit 70 determines whether the temperature change in the flow path outlet temperature T1 is abnormal (step S204). For example, if the flow path outlet temperature T1 in the temperature information 722 reaches a steady temperature earlier than normal, the control unit 70 determines that the temperature change in the flow path outlet temperature T1 is abnormal because there is a possibility that the multiple flow paths 211 in the electrolysis unit 210 of the separators 25, 26 are entirely blocked.

[0106] If the control unit 70 determines that the temperature change in the flow path outlet temperature T1 is abnormal (Yes in step S204), the control unit 70 proceeds to step S205. The control unit 70 increases the flow rate of the electrolytic solution to a first flow rate (step S205). The first flow rate is a flow rate determined to resolve overall blockage of the multiple flow paths 211. For example, the control unit 70 increases the flow rate of the electrolytic solution to the first flow rate by controlling the first circulation pump 31 and the second circulation pump 32 to increase the flow rate of the electrolytic solution in accordance with the current supplied to the water electrolysis cell 11. As a result, since the temperature change in the flow path outlet temperature T1 is abnormal, the water electrolysis device 1 can resolve the abnormality related to the flow path outlet temperature T1 by setting the flow rate of the electrolytic solution to the first flow rate. After completing step S205, the control unit 70 proceeds to step S208, which will be described later.

[0107] Furthermore, if the control unit 70 determines that the temperature change in the flow path outlet temperature T1 is not abnormal (No in step S204), the control unit 70 proceeds to step S206. The control unit 70 determines whether the flow path outlet temperature T2 has reached a steady temperature earlier than the flow path outlet temperature T1 (step S206). For example, if the flow path outlet temperature T2 in the temperature information 722 has reached a steady temperature earlier than the flow path outlet temperature T1 in the temperature information 722, the control unit 70 determines that the flow path outlet temperature T2 has reached a steady temperature earlier than the flow path outlet temperature T1. If the control unit 70 determines that the flow path outlet temperature T2 has not reached a steady temperature earlier than the flow path outlet temperature T1 (No in step S206), there is no abnormality in the multiple flow paths 211 in the electrolysis unit 210, and the control unit 70 proceeds to step S208, which will be described later.

[0108] Furthermore, if the control unit 70 determines that the flow path outlet temperature T2 has reached the steady-state temperature earlier than the flow path outlet temperature T1 (Yes in step S206), the control unit 70 proceeds to step S207 because there is a possibility that the plurality of flow paths 211 in the electrolysis unit 210 of the separators 25, 26 are partially blocked. The control unit 70 increases the flow rate of the electrolyte to a second flow rate (step S207). The second flow rate is a flow rate determined to resolve the partial blockage of the plurality of flow paths 211. For example, the control unit 70 increases the flow rate of the electrolyte to the second flow rate by controlling the first circulation pump 31 and the second circulation pump 32 to increase the flow rate of the electrolyte in accordance with the current supplied to the water electrolysis cell 11. In this way, the water electrolysis device 1 can resolve the partial blockage of the flow paths 211 in the electrolysis unit 210 by setting the flow rate of the electrolyte to the second flow rate. After completing step S207, the control unit 70 proceeds to step S208.

[0109] The control unit 70 determines whether or not to terminate the process (step S208). For example, the control unit 70 determines that the process is to terminate when a predetermined time has elapsed since the start of electrolysis. If the control unit 70 determines that the process is not to terminate (No in step S208), the control unit 70 continues the process by returning the process to step S201, which has already been described. If the control unit 70 determines that the process is to terminate (Yes in step S208), the control unit 70 terminates the process procedure shown in FIG. 15. When the process procedure shown in FIG. 15 is terminated, the control unit 70 controls the outlet temperatures of the electrolysis unit 210 of the pair of separators 25, 26 using the control method described in the first embodiment.

[0110] As described above, the water electrolysis device 1 according to the third embodiment measures the flow path outlet temperatures at a plurality of different locations using the second temperature sensor 82, and controls the flow rate of the electrolytic solution flowing through the electrolysis unit 210 based on the time change indicated by the measurement results of the flow path outlet temperatures. In this way, the water electrolysis device 1 is able to determine the state of the electrolysis unit 210 of the pair of separators 25, 26 from the temperature change since the start of electrolysis, and thereby change the flow rate of the electrolytic solution in accordance with the state of the electrolysis unit 210. As a result, the water electrolysis device 1 can contribute to eliminating abnormal conditions of the electrolysis unit 210 of the pair of separators 25, 26 at the start of electrolysis in the device, and can also suppress deterioration of the state of the electrolysis unit 210, thereby maintaining water electrolysis performance.

[0111] The water electrolysis apparatus 1 according to the third embodiment may be configured to control the flow rate of the electrolyte solution flowing through the electrolysis unit 210 based on temperature changes on the outer surface of the water electrolysis cell 11 measured by the third temperature sensor 83 shown in the second embodiment when the external environmental temperature is constant. The water electrolysis apparatus 1 according to the third embodiment may further include the third temperature sensor 83, and may be configured to control the flow rate of the electrolyte solution flowing through the electrolysis unit 210 based on temperature changes measured by the second temperature sensor 84 and the third temperature sensor 83.

[0112] The water electrolysis apparatus 1 according to the first to third embodiments described above may be further provided with a function of determining the state of the electrolysis unit 210 of the pair of separators 25, 26 based on the measured flow path outlet temperature and notifying an external device of the determination result.

[0113] (Effects) The water electrolysis device 1 according to the first aspect of the present disclosure includes a water electrolysis stack 21 having a water electrolysis cell 11 including a solid polymer electrolyte membrane 22 disposed between a pair of separators 25, 26 and electrolyzing an electrolytic solution using the water electrolysis cell 11; a power supply unit 12 electrically connected to the water electrolysis stack 21; a first electrolytic solution path 14 and a second electrolytic solution path 17 (electrolyte solution paths) for circulating the electrolytic solution to the water electrolysis cell 11; a first temperature sensor 81 capable of measuring an inlet temperature of the electrolytic solution flowing through an inlet of the water electrolysis stack 21; a second temperature sensor 82 capable of measuring flow path outlet temperatures of the electrolytic solution flowing through outlets of a plurality of flow paths 211 formed in an electrolysis unit 210 of the separators 25, 26; and a control unit 70 configured to adjust at least one of the flow rate, temperature, and amount of current of the electrolytic solution for the electrolysis unit 210 based on the inlet temperature measured by the first temperature sensor 81 and the flow path outlet temperatures measured by the second temperature sensor 82, so as to reduce an elevated temperature in a part of the electrolysis unit 210 of the separators 25, 26. Thus, when a local temperature rise occurs in the electrolysis section 210 of the pair of separators 25, 26, the water electrolysis device 1 can adjust the temperature of the electrolyte to prevent damage to the solid polymer electrolyte membrane 22 due to a rise in temperature. As a result, the water electrolysis device 1 can increase the temperature of the electrolyte, thereby improving the water electrolysis performance.

[0114] In the water electrolysis device 1 according to the second aspect of the present disclosure, the controller 70 controls to adjust at least one of the flow rate of the electrolytic solution, the temperature, and the amount of current to the electrolysis unit 210 so that the temperature rise in a part of the electrolysis unit 210 of the separators 25, 26 is equal to or lower than the heat resistance temperature of the solid polymer electrolyte membrane 22. In this way, even if the temperature rises locally in the electrolysis unit 210 of the pair of separators 25, 26, the water electrolysis device 1 can keep the temperature of the electrolysis unit 210 equal to or lower than the heat resistance temperature of the solid polymer electrolyte membrane 22, thereby reliably preventing damage to the solid polymer electrolyte membrane 22.

[0115] In the water electrolysis device 1 according to the third aspect of the present disclosure, the second temperature sensor 82 measures the flow path outlet temperatures in the separators 25, 26 at a plurality of different measurement positions in the width direction of the electrolysis unit 210, which includes an array of a plurality of flow paths 211. This allows the water electrolysis device 1 to determine the temperature distribution in the electrolysis unit 210 from the flow path outlet temperatures measured by the second temperature sensor 82, thereby enabling appropriate adjustment of the temperature of the electrolyte solution and further contributing to preventing damage to the solid polymer electrolyte membrane 22.

[0116] The water electrolysis device 1 according to the fourth aspect of the present disclosure further includes an adjustment unit 60 that adjusts the temperature of the electrolyte solution supplied to the inlet of the water electrolysis stack 21, and the controller 70 controls the adjustment unit 60 to reduce the temperature of the electrolyte solution supplied to the electrolysis unit 210, so as to reduce the temperature that has increased in a part of the electrolysis unit 210 of the separators 25, 26, based on the inlet temperature measured by the first temperature sensor 81 and the flow path outlet temperature measured by the second temperature sensor 82. Thus, by providing the adjustment unit 60 at the inlet of the water electrolysis stack 21, the water electrolysis device 1 can quickly reduce the temperature of the electrolyte solution supplied to the electrolysis unit 210, thereby further contributing to preventing damage to the solid polymer electrolyte membrane 22.

[0117] In the water electrolysis device 1 according to the fifth aspect of the present disclosure, the controller 70 controls the flow rate of the electrolytic solution flowing through the electrolysis unit 210, based on the temperature change from the start of electrolysis measured by the second temperature sensor 82. This allows the water electrolysis device 1 to contribute to eliminating abnormal conditions in the electrolysis unit 210 of the pair of separators 25, 26 at the start of electrolysis in the device, and to suppress deterioration of the condition of the electrolysis unit 210, thereby maintaining water electrolysis performance.

[0118] In the water electrolysis device 1 according to the sixth aspect of the present disclosure, when a temperature change from the start of electrolysis measured by the second temperature sensor 82 indicates blockage of the electrolysis unit 210, the controller 70 increases the flow rate of the electrolytic solution flowing through the electrolysis unit 210. This enables the water electrolysis device 1 to quickly resolve the abnormal state of the electrolysis unit 210 of the pair of separators 25, 26 at the start of electrolysis in the device, thereby maintaining water electrolysis performance.

[0119] A water electrolysis device (1) according to a seventh aspect of the present disclosure includes a water electrolysis stack (21) having a water electrolysis cell (11) including a solid polymer electrolyte membrane (22) disposed between a pair of separators (25, 26) and electrolyzing an electrolytic solution using the water electrolysis cell (11); a power supply unit (12) electrically connected to the water electrolysis stack (21); a first electrolytic solution path (14) and a second electrolytic solution path (17) (electrolyte solution paths) for circulating the electrolytic solution to the water electrolysis cell (11); a first temperature sensor (81) capable of measuring an inlet temperature of the electrolytic solution flowing through an inlet of the water electrolysis stack (21); a third temperature sensor (83) capable of measuring temperatures of external surfaces of the water electrolysis stack (21) corresponding to outlets of a plurality of flow paths (211) formed in an electrolysis unit (210) of the separators (25, 26); and a control unit (70) configured to adjust at least one of a flow rate, a temperature, and an amount of current of the electrolytic solution for the electrolysis unit (210) so as to reduce an elevated temperature in a part of the electrolysis unit (210) of the separators (25, 26) based on flow path outlet temperatures of the outlets of the plurality of flow paths (211) estimated from the inlet temperature and the temperature of the external surface. As a result, when a local temperature rise occurs in the electrolysis section 210 of the pair of separators 25, 26, the water electrolysis device 1 can prevent damage to the solid polymer electrolyte membrane 22 due to a rise in temperature by controlling the temperature of the electrolyte. As a result, the water electrolysis device 1 can increase the temperature of the electrolyte, thereby improving water electrolysis performance. Furthermore, since the water electrolysis device 1 only needs to measure the temperature of the outer surface of the water electrolysis stack 21, it is not necessary to provide the third temperature sensor 83 in the electrolysis section 210 of the separators 25, 26, thereby simplifying the device configuration.

[0120] In the water electrolysis device 1 according to the eighth aspect of the present disclosure, the water electrolysis stack 21 includes a plurality of water electrolysis cells 11 stacked in the stacking direction, and the third temperature sensors 83 are provided on the outer surface of the water electrolysis stack 21 at measurement positions including the center and end portions in the stacking direction. As a result, when a plurality of water electrolysis cells 11 are stacked in the water electrolysis device 1, it is not necessary to provide a third temperature sensor 83 for each of the plurality of water electrolysis cells 11, which prevents an increase in the number of third temperature sensors 83 and reduces the cost of the device.

[0121] A method for controlling a water electrolysis device (1) according to a ninth aspect of the present disclosure is a method for controlling a water electrolysis device (1) including a water electrolysis stack (21) having a water electrolysis cell (11) including a solid polymer electrolyte membrane (22) disposed between a pair of separators (25, 26) and electrolyzing an electrolytic solution using the water electrolysis cell (11); a power supply unit (12) electrically connected to the water electrolysis stack (21); and a first electrolytic solution path (14) and a second electrolytic solution path (17) for circulating and supplying the electrolytic solution to the water electrolysis cell (11), the method comprising the steps of: measuring, with a first temperature sensor (81), an inlet temperature of the electrolytic solution flowing through an inlet of the water electrolysis stack (21); measuring, with a second temperature sensor (82), flow path outlet temperatures of the electrolytic solution flowing through outlets of a plurality of flow paths (211) formed in an electrolysis unit (210) of the separators (25, 26); and adjusting, based on the inlet temperature and the flow path outlet temperature, at least one of a flow rate, a temperature, and an amount of current of the electrolytic solution for the electrolysis unit (210) so as to reduce a temperature that has increased in a part of the electrolysis unit (210) of the separators (25, 26). Thus, when a local temperature rise occurs in the electrolysis section 210 of the pair of separators 25, 26, the control method can adjust the temperature of the electrolyte, thereby preventing damage to the solid polymer electrolyte membrane 22 due to a rise in temperature. As a result, the control method can increase the temperature of the electrolyte, thereby improving the performance of water electrolysis.

[0122] A method for controlling a water electrolysis device (1) according to a tenth aspect of the present disclosure is a method for controlling a water electrolysis device (1) including a water electrolysis stack (21) having a water electrolysis cell (11) with a solid polymer electrolyte membrane (22) disposed between a pair of separators (25, 26) and electrolyzing an electrolyte solution using the water electrolysis cell (11), a power supply unit (12) electrically connected to the water electrolysis stack (21), and a first electrolyte solution path (14) and a second electrolyte solution path (17) (electrolyte solution paths) for circulating and supplying the electrolyte solution to the water electrolysis cell (11), the method comprising: measuring, with a third temperature sensor 83, temperatures of the external surfaces of the water electrolysis stack 21 corresponding to the outlets of the plurality of flow paths 211 formed in the electrolysis unit 210 of the separators 25, 26; and adjusting at least one of the flow rate, temperature, and current of the electrolyte solution for the electrolysis unit 210 based on flow path outlet temperatures of the outlets of the plurality of flow paths 211 estimated from the inlet temperatures and the external surface temperatures, so as to reduce a temperature increase in a part of the electrolysis unit 210 of the separators 25, 26. Thus, when a local temperature increase occurs in the electrolysis unit 210 of the pair of separators 25, 26, the control method controls the temperature of the electrolyte solution, thereby preventing damage to the solid polymer electrolyte membrane 22 due to a temperature increase. As a result, the control method can increase the temperature of the electrolyte solution, thereby improving the performance of water electrolysis. Furthermore, since the control method only requires measuring the temperature of the outer surface of the water electrolysis stack 21, there is no need to provide the third temperature sensor 83 in the electrolysis section 210 of the separators 25, 26, which simplifies the device configuration.

[0123] The program according to an eleventh aspect of the present disclosure causes a water electrolysis device (1) including a water electrolysis stack (21) having a water electrolysis cell (11) with a solid polymer electrolyte membrane (22) disposed between a pair of separators (25, 26) and electrolyzing an electrolyte solution using the water electrolysis cell (11), a power supply unit (12) electrically connected to the water electrolysis stack (21), and a first electrolyte solution path (14) and a second electrolyte solution path (17) (electrolyte solution paths) for circulating and supplying the electrolyte solution to the water electrolysis cell (11), to execute the following steps: measuring, with a first temperature sensor (81), an inlet temperature of the electrolyte solution flowing through an inlet of the water electrolysis stack (21); measuring, with a second temperature sensor (82), flow path outlet temperatures of the electrolyte solution flowing through outlets of a plurality of flow paths (211) formed in an electrolysis unit (210) of the separators (25, 26); and adjusting, based on the inlet temperature and the flow path outlet temperature, at least one of the flow rate, temperature, and amount of current of the electrolyte solution for the electrolysis unit (210) so as to reduce an increased temperature in a part of the electrolysis unit (210) of the separators (25, 26). Thus, when a local temperature rise occurs in the electrolysis unit 210 of the pair of separators 25, 26, the program can prevent damage to the solid polymer electrolyte membrane 22 due to a rise in temperature by adjusting the temperature of the electrolyte using the water electrolysis device 1. As a result, the control method can increase the temperature of the electrolyte, thereby improving the water electrolysis performance of the water electrolysis device 1.

[0124] The program according to a twelfth aspect of the present disclosure includes a water electrolysis device (1) including a water electrolysis stack (21) having a water electrolysis cell (11) with a solid polymer electrolyte membrane (22) disposed between a pair of separators (25, 26) and electrolyzing an electrolyte solution using the water electrolysis cell (11), a power supply unit (12) electrically connected to the water electrolysis stack (21), and a first electrolyte solution path (14) and a second electrolyte solution path (17) (electrolyte solution paths) for circulating and supplying the electrolyte solution to the water electrolysis cell (11). The program includes a step of measuring an inlet temperature of the electrolyte solution flowing through an inlet of the water electrolysis stack (21) using a first temperature sensor (81). measuring temperatures of the external surfaces of the water electrolysis stack 21 corresponding to the outlets of the plurality of flow paths 211 formed in the electrolysis unit 210 of the separators 25, 26 with a third temperature sensor 83; and adjusting at least one of the flow rate, temperature, and amount of current of the electrolyte solution for the electrolysis unit 210 so as to reduce a temperature rise in a part of the electrolysis unit 210 of the separators 25, 26, based on the flow path outlet temperatures of the outlets of the plurality of flow paths 211 estimated from the inlet temperature and the temperature of the external surface. Thus, when a local temperature rise occurs in the electrolysis unit 210 of the pair of separators 25, 26, the program controls the temperature of the electrolyte solution using the water electrolysis device 1, thereby preventing damage to the solid polymer electrolyte membrane 22 due to a temperature rise. As a result, the program can increase the temperature of the electrolyte solution, thereby improving the performance of water electrolysis in the water electrolysis device 1. Furthermore, since the program only needs to measure the temperature of the outer surface of the water electrolysis stack 21 in the water electrolysis device 1, there is no need to provide the third temperature sensor 83 in the electrolysis section 210 of the separators 25, 26, and the configuration of the water electrolysis device 1 can be simplified.

[0125] Although the embodiments of the present disclosure have been described above, the embodiments are not limited to the contents of these embodiments. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the above-described components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-described embodiments.

[0126] REFERENCE SIGNS LIST 1 Water electrolysis device 11 Water electrolysis cell 12 Power supply unit 14 First electrolyte path 14a, 17a Inlet path 14b, 17b Outlet path 15 First gas-liquid separation tank 15a, 18a Filter 16 Oxygen gas extraction path 17 Second electrolyte path 18 Second gas-liquid separation tank 19 Hydrogen gas extraction path 20 End plate 21 Water electrolysis stack 22 Solid polymer electrolyte membrane 23 Anode side 24 Cathode side 25, 26 Separator 27, 28 Power supply body 29a Inlet pipe section 29b Outlet pipe section 31 First circulation pump 32 Second circulation pump 33 Hydrogen control valve 34 Auxiliary path 35 Buffer tank 36 Water discharge valve 41 First water supply path 42 First water supply valve 43 Second water supply path 44 Second water supply valve 51, 52 Catalyst layer 60 Adjustment unit 70 Control unit 72 Memory unit 81 First temperature sensor 82, 82a, 82b, 82c Second temperature sensor 83 Third temperature sensor 200 Main body 200A, 200B Region 201 Fixing unit 210 Electrolysis unit 211 Flow path 220 Electrolyte inlet 230 Electrolyte outlet 240 Packing 721 Program 722 Temperature information 723 Estimation information 724 Temperature change information F Longitudinal direction H Stacking direction L Direction L1, L2, L3 Flow direction P1, P2, P3, P4 Points T1, T2, T3 Flow path outlet temperature W Width direction

Claims

1. A water electrolysis device comprising: a water electrolysis stack having a water electrolysis cell with a solid polymer electrolyte membrane disposed between a pair of separators, the water electrolysis stack electrolyzing an electrolyte solution using the water electrolysis cell; a power supply unit electrically connected to the water electrolysis stack; an electrolyte solution path for circulating the electrolyte solution to the water electrolysis cell; a first temperature sensor capable of measuring an inlet temperature of the electrolyte solution flowing through an inlet of the water electrolysis stack; a second temperature sensor capable of measuring flow path outlet temperatures of the electrolyte solution flowing through outlets of a plurality of flow paths formed in an electrolysis section of the separator; and a control unit configured to adjust at least one of the flow rate, temperature, and amount of current of the electrolyte solution to the electrolysis section, based on the inlet temperature measured by the first temperature sensor and the flow path outlet temperatures measured by the second temperature sensor, so as to reduce a temperature that has increased in a part of the electrolysis section of the separator.

2. The water electrolysis device according to claim 1, wherein the control unit adjusts at least one of the flow rate, temperature, and current of the electrolytic solution to the electrolytic section so that the temperature rise in a portion of the electrolytic section of the separator is equal to or lower than the heat resistance temperature of the solid polymer electrolyte membrane.

3. The water electrolysis device according to claim 2, wherein the second temperature sensor measures the temperature at the outlet of the flow path in the separator at a plurality of different measurement positions in the width direction of the electrolysis section in which a plurality of flow paths are arranged.

4. The water electrolysis device according to claim 3, further comprising an adjustment unit that adjusts the temperature of the electrolyte supplied to the inlet of the water electrolysis stack, wherein the control unit uses the adjustment unit to lower the temperature of the electrolyte relative to the electrolysis unit so as to lower the temperature that has risen in a part of the electrolysis unit of the separator based on the inlet temperature of the first temperature sensor and the flow path outlet temperature of the second temperature sensor.

5. The water electrolysis device according to claim 1, wherein the control unit controls the flow rate of the electrolytic solution flowing through the electrolysis unit based on the temperature change measured by the second temperature sensor from the start of electrolysis.

6. The water electrolysis device according to claim 5, wherein the control unit increases the flow rate of the electrolyte flowing through the electrolysis unit when the temperature change from the start of electrolysis measured by the second temperature sensor indicates blockage of the electrolysis unit.

7. A water electrolysis device comprising: a water electrolysis stack having a water electrolysis cell with a solid polymer electrolyte membrane disposed between a pair of separators, the water electrolysis stack electrolyzing an electrolyte using the water electrolysis cell; a power supply unit electrically connected to the water electrolysis stack; an electrolyte path circulating the electrolyte to the water electrolysis cell; a first temperature sensor capable of measuring an inlet temperature of the electrolyte flowing through an inlet of the water electrolysis stack; a third temperature sensor capable of measuring temperatures of external surfaces of the water electrolysis stack corresponding to outlets of a plurality of flow paths formed in an electrolysis section of the separator; and a control unit performing control to adjust at least one of the flow rate, temperature, and current of the electrolyte to the electrolysis section so as to reduce an elevated temperature in a part of the electrolysis section of the separator, based on flow path outlet temperatures of the outlets of the plurality of flow paths estimated from the inlet temperature and the temperature of the external surface.

8. The water electrolysis device according to claim 7, wherein the water electrolysis stack has a plurality of the water electrolysis cells stacked in a stacking direction, and the third temperature sensor is provided on the outer surface of the water electrolysis stack at a measurement position including the center and end in the stacking direction.

9. A method for controlling a water electrolysis device comprising a water electrolysis stack having a water electrolysis cell with a solid polymer electrolyte membrane disposed between a pair of separators and electrolyzing an electrolyte solution using the water electrolysis cell, a power supply unit electrically connected to the water electrolysis stack, and an electrolyte solution path for circulating and supplying the electrolyte solution to the water electrolysis cell, the method comprising the steps of: measuring, with a first temperature sensor, the inlet temperature of the electrolyte solution flowing through an inlet of the water electrolysis stack; measuring, with a second temperature sensor, the flow path outlet temperatures of the electrolyte solution flowing through outlets of a plurality of flow paths formed in an electrolysis section of the separator; and adjusting, based on the inlet temperature and the flow path outlet temperature, at least one of the flow rate, temperature, and current amount of the electrolyte solution to the electrolysis section so as to reduce a temperature that has increased in a part of the electrolysis section of the separator.

10. A method for controlling a water electrolysis device comprising a water electrolysis stack having a water electrolysis cell with a solid polymer electrolyte membrane disposed between a pair of separators and electrolyzing an electrolyte solution using the water electrolysis cell, a power supply unit electrically connected to the water electrolysis stack, and an electrolyte solution path for circulating and supplying the electrolyte solution to the water electrolysis cell, the method comprising the steps of: measuring, with a first temperature sensor, the inlet temperature of the electrolyte solution flowing through an inlet of the water electrolysis stack; measuring, with a third temperature sensor, the temperatures of the external surfaces of the water electrolysis stack corresponding to the outlets of a plurality of flow paths formed in an electrolysis section of the separator; and adjusting at least one of the flow rate, temperature, and current of the electrolyte solution to the electrolysis section, based on the flow path outlet temperatures of the outlets of the plurality of flow paths estimated from the inlet temperature and the temperature of the external surface, so as to reduce the temperature that has increased in a part of the electrolysis section of the separator.

11. A program for causing a water electrolysis device comprising a water electrolysis stack having a water electrolysis cell with a solid polymer electrolyte membrane disposed between a pair of separators and electrolyzing an electrolyte solution using the water electrolysis cell, a power supply unit electrically connected to the water electrolysis stack, and an electrolyte solution path for circulating and supplying the electrolyte solution to the water electrolysis cell, to execute the following steps: measuring the inlet temperature of the electrolyte solution flowing through the inlet of the water electrolysis stack with a first temperature sensor; measuring the flow path outlet temperatures of the electrolyte solution flowing through the outlets of a plurality of flow paths formed in an electrolysis section of the separator with a second temperature sensor; and adjusting at least one of the flow rate, temperature, and current of the electrolyte solution to the electrolysis section based on the inlet temperature and the flow path outlet temperature so as to reduce a temperature that has risen in a part of the electrolysis section of the separator.

12. A program for causing a water electrolysis device comprising a water electrolysis stack having a water electrolysis cell with a solid polymer electrolyte membrane disposed between a pair of separators and electrolyzing an electrolyte solution using the water electrolysis cell, a power supply unit electrically connected to the water electrolysis stack, and an electrolyte solution path for circulating and supplying the electrolyte solution to the water electrolysis cell, to execute the following steps: measuring the inlet temperature of the electrolyte solution flowing through the inlet of the water electrolysis stack with a first temperature sensor; measuring the temperatures of the external surfaces of the water electrolysis stack corresponding to the outlets of multiple flow paths formed in the electrolysis section of the separator with a third temperature sensor; and adjusting at least one of the flow rate, temperature, and current of the electrolyte solution to the electrolysis section based on the flow path outlet temperatures of the outlets of the multiple flow paths estimated from the inlet temperature and the temperature of the external surface, so as to reduce the temperature that has increased in a part of the electrolysis section of the separator.

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