Water electrolysis system

Abstract

Provided is a water electrolysis system that can reduce the difference in current flowing through a plurality of water electrolysis stacks. The water electrolysis system includes: a power supply unit; a plurality of water electrolysis stacks connected in parallel with respect to the power supply unit; at least one temperature adjustment unit for adjusting the temperature of at least one of the plurality of water electrolysis stacks; and a control device that controls the operation of the at least one temperature adjustment unit. The control device controls the operation of the at least one temperature adjustment unit so that the difference in current flowing through the plurality of water electrolysis stacks is smaller than when the at least one temperature adjustment unit is not operating.

Description

Technical Field

[0001] This specification relates to a water electrolysis system. Background Technology

[0002] Patent Document 1 discloses a water electrolysis system comprising: a power supply unit; multiple water electrolysis stacks connected in parallel with respect to the power supply unit; and a control device.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2023-157554 Summary of the Invention

[0004] When multiple water electrolyzers are connected in parallel with respect to a power unit, the voltage of each water electrolyzer is equal. Furthermore, the voltage characteristics (IV) of each water electrolyzer vary depending on factors such as the degree of degradation of each electrolyzer. Therefore, when multiple water electrolyzers are connected in parallel with respect to a power unit, the current flowing through each water electrolyzer differs. It is desirable to reduce the difference in current flowing through each of the multiple water electrolyzers.

[0005] This specification provides a technique for reducing the difference in current flowing through multiple water electrolyzers.

[0006] In the first embodiment disclosed in this specification, the water electrolysis system includes: a power supply unit; a plurality of water electrolysis stacks connected in parallel with respect to the power supply unit; at least one temperature regulating unit for regulating the temperature of at least one of the plurality of water electrolysis stacks; and a control device for controlling the operation of the at least one temperature regulating unit. The control device can control the operation of the at least one temperature regulating unit so that the difference in current flowing through the plurality of water electrolysis stacks is smaller than when the at least one temperature regulating unit is not activated.

[0007] The IV characteristic of a water electrolysis reactor varies depending on its temperature. According to the aforementioned water electrolysis system, the control device can change the IV characteristic of the water electrolysis reactor corresponding to the temperature regulating unit by controlling its operation. Furthermore, by changing the IV characteristic of the water electrolysis reactor, the magnitude of the reactor current changes. Therefore, the control device can control the operation of at least one temperature regulating unit to adjust the magnitude of the reactor current in each water electrolysis reactor. Thus, the difference in current flowing through multiple water electrolysis reactors can be reduced.

[0008] In the second embodiment, in the first embodiment described above, the water electrolysis system may further include multiple reaction water supply pipes, each of which is connected to the oxygen electrode side of one of the multiple water electrolysis reactors. Each of the at least one temperature regulating unit may be disposed on the reaction water supply pipe connected to the water electrolysis reactor corresponding to that temperature regulating unit, and may include a flow regulating unit that regulates the amount of reaction water passing through the reaction water supply pipe on which the temperature regulating unit is disposed.

[0009] Based on the above structure, the control device can adjust the temperature of the water electrolysis reactor, i.e., the magnitude of the reactor current, by adjusting the amount of reaction water supplied to the water electrolysis reactor.

[0010] In the third embodiment, in the first or second embodiment described above, the water electrolysis system may further include multiple reaction water supply pipes, each of which is connected to the oxygen electrode side of one of the multiple water electrolysis reactors. Each of the at least one temperature regulating unit may be disposed on the reaction water supply pipe connected to the water electrolysis reactor corresponding to that temperature regulating unit, and may include a heat exchanger that regulates the temperature of the reaction water passing through the reaction water supply pipe on which the temperature regulating unit is disposed.

[0011] Based on the above structure, the control device can adjust the temperature of the water electrolysis reactor, i.e., the magnitude of the reactor current, by adjusting the temperature of the reaction water supplied to the water electrolysis reactor.

[0012] In the fourth embodiment, in any of the first to third embodiments described above, the water electrolysis system may further include multiple cooling water supply pipes, each of which is connected to a plurality of water electrolysis reactors. Each of the at least one temperature regulating unit may be disposed on the cooling water supply pipe connected to the water electrolysis reactor corresponding to that temperature regulating unit, and may include a flow regulating unit that regulates the amount of cooling water passing through the cooling water supply pipe on which the temperature regulating unit is disposed.

[0013] According to the above structure, the control device can adjust the temperature of the water electrolysis reactor, i.e. the magnitude of the reactor current, by adjusting the amount of cooling water supplied to the water electrolysis reactor.

[0014] In the fifth method, in any of the methods 1 to 4 above, the at least one temperature regulating unit may include a plurality of temperature regulating units, and the plurality of temperature regulating units are respectively connected to the plurality of water electrolysis reactors.

[0015] Based on the above structure, the control device can adjust the IV characteristics of all water electrolyzers. Therefore, it is possible to make the current flowing through multiple water electrolyzers consistent or approximately the same. Attached Figure Description

[0016] Figure 1 This is a diagram showing the electrical structure of water electrolysis system 2.

[0017] Figure 2 This is a diagram showing the flow path structure of water electrolysis system 2.

[0018] Figure 3 This is a flowchart of the adjustment process performed by the control device 100.

[0019] Figure 4 This is a diagram illustrating an example of the IV characteristics of various water electrolyzers.

[0020] Figure 5 It means Figure 3 A figure illustrating an example of the IV characteristics of each water electrolyzer after S14.

[0021] Figure 6 This is a diagram showing the structure of the flow path in the water electrolysis system 202.

[0022] Figure 7 This is a diagram showing the flow path structure of the water electrolysis system 302. Detailed Implementation

[0023] (First embodiment)

[0024] like Figure 1 As shown, the water electrolysis system 2 includes a power supply unit 10, a rectifier 12, multiple parallel circuits 14A-14C, multiple water electrolysis stacks 16A-16C, multiple current sensors 18A-18C, multiple voltage sensors 20A-20C, and a control device 100. The water electrolysis system 2 is a system for producing hydrogen by electrolyzing reaction water.

[0025] Power supply unit 10 supplies AC power. As an example, power supply unit 10 is a device that converts commercial power or renewable energy into AC power.

[0026] One end of the rectifier 12 is connected to the power supply unit 10. The other end of the rectifier 12 is connected to a plurality of parallel circuits 14A to 14C. The rectifier 12 converts the AC power supplied from the power supply unit 10 into DC power. Furthermore, the rectifier 12 regulates the power supplied to the plurality of parallel circuits 14A to 14C.

[0027] Multiple parallel circuits 14A to 14C are connected in parallel with respect to rectifier 12.

[0028] Multiple water electrolysis reactors 16A to 16C are respectively configured in multiple parallel circuits 14A to 14C. For example... Figure 2 As shown, multiple water electrolysis reactors 16A to 16C include those along a specific direction (in Figure 2Multiple units C are stacked (in the left-right direction). Multiple water electrolyzers 16A to 16C electrolyze the reacting water to produce hydrogen.

[0029] like Figure 1 As shown, multiple current sensors 18A to 18C are respectively configured in multiple parallel circuits 14A to 14C. Furthermore, multiple voltage sensors 20A to 20C are respectively configured in multiple parallel circuits 14A to 14C.

[0030] like Figure 2 As shown, the water electrolysis system 2 also includes an oxygen-side unit 30 and a hydrogen-side unit 80.

[0031] The oxygen electrode side unit 30 includes a tank 32, a pump 34, a first heat exchanger 36, an ion exchanger 38, a first gas-liquid separator 40, and valves 42A to 42C. Reaction water is stored in the tank 32. The ion exchanger 38 removes impurities from the reaction water.

[0032] The oxygen electrode side unit 30 also includes a first supply pipe 50, multiple second supply pipes 52A-52C, multiple first discharge pipes 54A-54C, a second discharge pipe 56, a third discharge pipe 58, a fourth discharge pipe 60, and a bypass pipe 62. The upstream end of the first supply pipe 50 is connected to the tank 32. In the first supply pipe 50, a pump 34, a first heat exchanger 36, an ion exchanger 38, and a valve 42A are sequentially arranged from the upstream side. The valve 42A regulates the amount of reaction water passing through the first supply pipe 50.

[0033] Multiple second supply pipes 52A-52C are connected in parallel with respect to the first supply pipe 50. The downstream ends of the multiple second supply pipes 52A-52C are respectively connected to the oxygen electrode side of multiple water electrolysis reactors 16A-16C. A first flow regulating valve 70A and a temperature sensor 72A are installed on the second supply pipe 52A. The first flow regulating valve 70A regulates the flow rate of the reaction water passing through the second supply pipe 52A. The temperature sensor 72A detects the temperature of the reaction water supplied to the water electrolysis reactor 16A, i.e., the reaction water temperature. First flow regulating valves 70B and 70C and temperature sensors 72B and 72C are also respectively installed in the second supply pipes 52B and 52C.

[0034] The upstream ends of multiple first discharge pipes 54A-54C are connected to the oxygen electrode side of multiple water electrolysis reactors 16A-16C, respectively. The multiple first discharge pipes 54A-54C are connected in parallel with respect to the second discharge pipe 56. The downstream end of the second discharge pipe 56 is connected to the first gas-liquid separator 40. A valve 42B is installed in the second discharge pipe 56. Valve 42B regulates the amount of fluid passing through the second discharge pipe 56.

[0035] The upstream ends of the third discharge pipe 58 and the fourth discharge pipe 60 are connected to the first gas-liquid separator 40. The downstream end of the third discharge pipe 58 is connected to the tank 32. The downstream end of the fourth discharge pipe 60 is open to the outside of the water electrolysis system 2.

[0036] A gas-liquid mixture containing oxygen generated in the multiple water electrolyzers 16A-16C and unelectrolyzed reaction water is supplied to the first gas-liquid separator 40 via multiple first discharge pipes 54A-54C and a second discharge pipe 56. Then, in the first gas-liquid separator 40, the oxygen and reaction water are separated. The separated reaction water is supplied to tank 32 via a third discharge pipe 58. The separated oxygen is discharged to the outside via a fourth discharge pipe 60.

[0037] A bypass pipe 62 connects the first supply pipe 50 and the second discharge pipe 56. The upstream end of the bypass pipe 62 connects to the first supply pipe 50 between the ion exchanger 38 and valve 42A. The downstream end of the bypass pipe 62 connects to the second discharge pipe 56 between the first gas-liquid separator 40 and valve 42B. A valve 42C is installed on the bypass pipe 62. Valve 42C regulates the amount of fluid passing through the bypass pipe 62.

[0038] The hydrogen electrode side unit 80 includes a second gas-liquid separator 82, multiple fifth discharge pipes 84A to 84C, a sixth discharge pipe 86, a seventh discharge pipe 88, and an eighth discharge pipe 90.

[0039] The upstream ends of multiple fifth discharge pipes 84A-84C are respectively connected to the hydrogen electrode side of multiple water electrolysis reactors 16A-16C. The multiple fifth discharge pipes 84A-84C are connected in parallel with respect to the sixth discharge pipe 86. The downstream end of the sixth discharge pipe 86 is connected to the second gas-liquid separator 82. The upstream ends of the seventh discharge pipe 88 and the eighth discharge pipe 90 are connected to the second gas-liquid separator 82. The downstream end of the seventh discharge pipe 88 is connected to a hydrogen storage device. The downstream end of the eighth discharge pipe 90 is open to the outside of the water electrolysis system 2. Alternatively, in a modified example, the downstream end of the eighth discharge pipe 90 may be connected to a tank 32.

[0040] A gas-liquid mixture containing hydrogen generated in the multiple water electrolyzers 16A-16C and unelectrolyzed reaction water is supplied to the second gas-liquid separator 82 via multiple fifth discharge pipes 84A-84C and a sixth discharge pipe 86. Then, in the second gas-liquid separator 82, the hydrogen and reaction water are separated. The separated hydrogen is supplied to a hydrogen storage device via a seventh discharge pipe 88. The separated reaction water is discharged to the outside via an eighth discharge pipe 90.

[0041] Figure 1The control device 100 is a computer composed of CPU, ROM, RAM, etc. The control device 100 controls the operation of each component of the water electrolysis system 2.

[0042] (Adjustment and processing;) Figure 3 )

[0043] refer to Figure 3 The adjustment process performed by the control device 100 of the water electrolysis system 2 will be described. Furthermore, before performing the adjustment process, the control device 100 determines a common target current It (reference) for the multiple water electrolysis stacks 16A to 16C. Figure 4 ).

[0044] In S10, the control device 100 determines the stack voltage corresponding to the target current It for each of the plurality of water electrolysis stacks 16A to 16C.

[0045] In S12, the control device 100 uses the multiple stack voltages determined in S10 to determine the water electrolysis unit with the lowest performance among the multiple water electrolysis units 16A to 16C as the reference water electrolysis unit. The water electrolysis unit with the lowest performance is the water electrolysis unit with the highest stack voltage determined in S10 among the multiple water electrolysis units 16A to 16C. In addition, the water electrolysis unit with the lowest performance is also the water electrolysis unit with the lowest stack current relative to the same stack voltage. Hereinafter, water electrolysis units other than the reference water electrolysis unit will be referred to as "target water electrolysis units". Furthermore, hereafter, the stack voltage of the reference water electrolysis unit corresponding to the target current It and the stack voltage of the target water electrolysis unit corresponding to the target current It will be referred to as "reference voltage" and "target voltage", respectively.

[0046] In S14, the control device 100 calculates multiple target reaction water quantities corresponding to the multiple water electrolysis reactors 16A to 16C respectively. The control device 100 calculates the target reaction water quantity for each of the multiple water electrolysis reactors 16A to 16C to ensure that the reactor voltage corresponding to the target current It is the same. As mentioned above, the reference voltage is greater than the target voltage. Furthermore, the lower the temperature of the water electrolysis reactor, the lower its performance. That is, the lower the temperature of the water electrolysis reactor, the larger the reactor voltage becomes relative to the same reactor current. Therefore, the control device 100 determines multiple target reaction water quantities to ensure that the temperature of the target water electrolysis reactor is lower than the temperature of the reference water electrolysis reactor. Specifically, the control device 100 determines multiple target reaction water quantities to ensure that the amount of reaction water supplied to the target water electrolysis reactor is greater than the amount of reaction water supplied to the reference water electrolysis reactor.

[0047] The control device 100 calculates the voltage difference, which is the difference between the reference voltage and the target voltage, for each of the target water electrolyzers. Next, the control device 100 uses the current temperature of the reaction water and the voltage difference to calculate the amount of reaction water required to make the voltage difference zero. Then, the control device 100 uses the amount of reaction water flowing through the multiple second supply pipes 52A-52C and the determined necessary amount of reaction water to calculate the target amount of reaction water corresponding to each of the multiple water electrolyzers 16A-16C.

[0048] In S16, the control device 100 uses multiple target reaction water volumes calculated in S14 to control the operation (opening degree) of multiple first flow regulating valves 70A to 70C. As a result, the amount of reaction water supplied to the target water electrolyzer is greater than the amount supplied to the reference water electrolyzer. Furthermore, the temperature of the target water electrolyzer decreases, and the IV characteristics of the target water electrolyzer change. Consequently, the reactor voltage in the target water electrolyzer corresponding to the target current It is the same as or approximately the reference voltage.

[0049] In S20, the control device 100 determines whether the difference between the detected values ​​from each current sensor 18A to 18C, i.e., the current difference, is within a specified value. If the current difference is not within the specified value ("No" in S20), the control device 100 proceeds to S22. On the other hand, if the current difference is within the specified value ("Yes" in S20), the control device 100 proceeds to S24.

[0050] In S22, the control device 100 controls the operation (opening degree) of a plurality of first flow regulating valves 70A to 70C to keep the current difference within a specified value. As an example, when the reactor current of the water electrolysis reactor 16A is at its maximum, the control device 100 controls the operation of the first flow regulating valve 70A to increase the amount of reaction water supplied to the water electrolysis reactor 16A.

[0051] In S24, the control device 100 determines whether the time elapsed since the execution of S10 has exceeded the first predetermined time. If the control device 100 determines that the first predetermined time has elapsed ("Yes" in S24), it proceeds to S26. On the other hand, if the control device 100 determines that the elapsed time has not exceeded the first predetermined time ("No" in S24), it proceeds to S30.

[0052] In S26, the control device 100 controls the operation (opening degree) of multiple first flow regulating valves 70A to 70C to ensure that the amount of reaction water supplied to each water electrolysis reactor 16A to 16C is the same. If S26 ends, the control device 100 returns to S10. Alternatively, if a second predetermined time has elapsed since the end of S26, the control device 100 can execute the process of S10. The second predetermined time is the time required for the temperature of each water electrolysis reactor 16A to 16C to become the same.

[0053] Furthermore, in S30, the control device 100 determines whether an end signal has been received. If an end signal is received (yes in S30), the control device 100 terminates the process. Figure 3 The processing continues. On the other hand, if the control device 100 does not receive an end signal ("No" in S30), it returns to S20.

[0054] (Specific details)

[0055] refer to Figure 4 , Figure 5 The specific implementation details of the water electrolysis system 2 in this embodiment will be explained. Figure 4 The multiple IV characteristics 110A to 110C correspond to multiple water electrolysis reactors 16A to 16C, respectively.

[0056] The control device 100 determines multiple stack voltages VA to VC corresponding to the target current for each of the multiple water electrolysis stacks 16A to 16C. Figure 3 (S10). Next, in the control device 100, since the stack voltage VA is the maximum, the water electrolysis stack 16A corresponding to the stack voltage VA is determined as the reference water electrolysis stack (S12). Furthermore, the control device 100 determines water electrolysis stacks 16B and 16C as reference water electrolysis stacks.

[0057] Control device 100 calculates the voltage difference between the reference voltage VA and the target voltage VB for water electrolysis reactor 16B. Using the current temperature of the reaction water and the voltage difference, control device 100 calculates the amount of reaction water required to make the voltage difference zero. Control device 100 performs the same process for water electrolysis reactor 16C. Next, using the amount of reaction water flowing through the multiple second supply pipes 52A-52C and the determined required amount of reaction water, control device 100 calculates the target amount of reaction water corresponding to each of the multiple water electrolysis reactors 16A-16C (S14).

[0058] The control device 100 uses multiple target reaction water flows to control the operation (opening degree) of multiple first flow regulating valves 70A to 70C. In this case, the amount of reaction water supplied to the water electrolysis reactors 16B and 16C is greater than the amount supplied to the water electrolysis reactor 16A, therefore the temperature of the water electrolysis reactors 16B and 16C is lower than the temperature of the water electrolysis reactor 16A. Furthermore, the amount of reaction water supplied to the water electrolysis reactor 16C is greater than the amount supplied to the water electrolysis reactor 16B, therefore the temperature of the water electrolysis reactor 16C is lower than the temperature of the water electrolysis reactor 16B. As the temperature of the water electrolysis reactors 16B and 16C decreases, the IV characteristics 110B and 110C become IV characteristics 110B' and 110C'. As a result, the reactor voltage corresponding to the target current It in the water electrolysis reactors 16B and 16C is consistent with or approximately equal to the reference voltage VA. Then, the control device 100 executes... Figure 3 The processing of S20 to S26 and S30.

[0059] As described above, in this embodiment, the control device 100 lowers the temperature of the target water electrolysis reactor so that the reactor voltage corresponding to the target current in the target water electrolysis reactor is consistent with or approximately the reference voltage. Based on this structure, the durability of the target water electrolysis reactor can be improved.

[0060] As described above, the water electrolysis system 2 includes: a power supply unit 10; multiple water electrolysis stacks 16A to 16C connected in parallel with respect to the power supply unit 10; multiple first flow regulating valves 70A to 70C (an example of a "temperature regulating unit") for regulating the temperature of each of the multiple water electrolysis stacks 16A to 16C; and a control device 100 that controls the operation of the multiple flow regulating valves. The control device 100 controls the operation of the multiple first flow regulating valves 70A to 70C so that the difference in current flowing through the multiple water electrolysis stacks 16A to 16C is smaller than when the multiple first flow regulating valves 70A to 70C are not activated. Figure 3 ).

[0061] According to the water electrolysis system 2 described above, the control device 100 can change the IV characteristics of the water electrolysis stacks 16A to 16C corresponding to the first flow regulating valves 70A to 70C by controlling the operation of the first flow regulating valves 70A to 70C. Then, by changing the IV characteristics of the water electrolysis stacks 16A to 16C, the magnitude of the stack current of the water electrolysis stacks 16A to 16C changes. Therefore, the control device 100 can control the operation of the first flow regulating valves 70A to 70C to adjust the magnitude of the stack current of the multiple water electrolysis stacks 16A to 16C. Therefore, the difference in current flowing through the multiple water electrolysis stacks 16A to 16C can be reduced.

[0062] Furthermore, based on the above structure, the control device 100 can adjust the IV characteristics of all water electrolyzers 16A to 16C. Therefore, it is possible to make the current flowing through the multiple water electrolyzers 16A to 16C consistent or approximately the same.

[0063] Furthermore, the water electrolysis system 2 also includes multiple second supply pipes 52A-52C (an example of "multiple reaction water supply pipes") that are respectively connected to the oxygen electrode side of multiple water electrolysis reactors 16A-16C. First flow regulating valves 70A-70C are respectively installed on the second supply pipes 52A-52C that are connected to the water electrolysis reactors 16A-16C corresponding to the first flow regulating valves 70A-70C.

[0064] According to the above structure, the control device 100 can adjust the temperature of the multiple water electrolysis reactors 16A to 16C, i.e. the magnitude of the stack current of the water electrolysis reactors 16A to 16C, by adjusting the amount of reaction water supplied to the multiple water electrolysis reactors 16A to 16C.

[0065] (Second embodiment)

[0066] refer to Figure 6 The water electrolysis system 202 of the second embodiment will be described below. Hereinafter, common structures in the embodiments will be labeled with the same symbols and their descriptions will be omitted.

[0067] like Figure 6 As shown, the water electrolysis system 202 of the second embodiment has a plurality of second heat exchangers 270A to 270C instead of a plurality of first flow regulating valves 70A to 70C, which differs from the water electrolysis system 2 of the first embodiment. The plurality of second heat exchangers 270A to 270C are respectively provided on a plurality of second supply pipes 52A to 52C.

[0068] (Adjustment and processing;) Figure 3 )

[0069] The control device 100 of the second embodiment also performs... Figure 3 The processing of S14, S16, S22, and S26 in the second embodiment differs from that in the first embodiment.

[0070] In S14, the control device 100 calculates the temperature of the reaction water to be supplied to the multiple water electrolyzers 16A to 16C, i.e., the target reaction water temperature. The target reaction water temperature is the target temperature used to achieve a zero voltage difference. The control device 100 determines the target reaction water temperature using the current reaction water temperature and the voltage difference. Furthermore, the control device 100 determines the target reaction water temperature to ensure that the temperature of the target water electrolyzer is lower than the temperature of the reference water electrolyzer.

[0071] In S16, the control device 100 uses the multiple reaction water temperatures calculated in S14 to control the operation of the multiple second heat exchangers 270A to 270C. As a result, the reaction water temperature supplied to the target water electrolyzer is lower than the reaction water temperature supplied to the reference water electrolyzer. Furthermore, the lower temperature of the target water electrolyzer causes a change in its IV characteristics. Consequently, the reactor voltage in the target water electrolyzer corresponding to the target current It is consistent with or approximately equal to the reference voltage.

[0072] Furthermore, in S22, the control device 100 controls the operation of the second heat exchangers 270A to 270C to keep the current difference within a specified value. Specifically, the control device 100 drives the heat exchanger corresponding to the target water electrolysis reactor. As an example, when the reactor current of the water electrolysis reactor 16A is at its maximum, the control device 100 controls the operation of the second heat exchanger 270A to reduce the temperature of the reaction water supplied to the water electrolysis reactor 16A.

[0073] Furthermore, in S26, the control device 100 stops the plurality of second heat exchangers 270A to 270C.

[0074] As described above, the water electrolysis system 202 also includes multiple second supply pipes 52A-52C (an example of "multiple reaction water supply pipes") that are respectively connected to the oxygen electrode side of multiple water electrolysis reactors 16A-16C. Multiple second heat exchangers 270A-270C (an example of "at least one temperature control unit") are respectively provided on the second supply pipes 52A-52C that are connected to the water electrolysis reactors 16A-16C corresponding to the second heat exchangers 270A-270C.

[0075] According to the above structure, the control device 100 can adjust the temperature of the water electrolysis reactor 16A to 16C, i.e. the stack current of the water electrolysis reactor 16A to 16C, by adjusting the temperature of the reaction water supplied to the water electrolysis reactor 16A to 16C.

[0076] (Third embodiment)

[0077] refer to Figure 7 The water electrolysis system 302 of the third embodiment will be described.

[0078] like Figure 7 As shown, the water electrolysis system 302 of the third embodiment does not have multiple first flow regulating valves 70A to 70C (see reference). Figure 2 ) and multiple second heat exchangers 270A to 270C (reference) Figure 6 The water electrolysis system 302 includes a cooling unit 310. The cooling unit 310 includes a third heat exchanger 320 and a pump 322.

[0079] The cooling unit 310 also includes a first cooling water supply pipe 330, multiple second cooling water supply pipes 332A-332C, multiple first cooling water discharge pipes 334A-334C, and a second cooling water discharge pipe 336. The upstream end of the first cooling water supply pipe 330 is connected to the third heat exchanger 320. A pump 322 is installed in the first cooling water supply pipe 330. The multiple second cooling water supply pipes 332A-332C are connected in parallel with respect to the first cooling water supply pipe 330. The downstream ends of the multiple second cooling water supply pipes 332A-332C are respectively connected to multiple water electrolysis reactors 16A-16C. A second flow regulating valve 340A and a temperature sensor 342A are installed on the second cooling water supply pipe 332A. The second flow regulating valve 340A regulates the flow rate of cooling water through the second cooling water supply pipe 332A. Temperature sensor 342A detects the temperature of the cooling water supplied to the water electrolysis reactor 16A. Second flow regulating valves 340B and 340C, and temperature sensors 342B and 342C are also installed in the second cooling water supply pipes 332B and 332C, respectively. The cooling water supplied to each water electrolysis reactor 16A to 16C flows through flow paths provided between multiple units C.

[0080] The upstream ends of multiple first cooling water discharge pipes 334A-334C are connected to multiple water electrolysis reactors 16A-16C, respectively. The multiple first cooling water discharge pipes 334A-334C are connected in parallel with respect to the second cooling water discharge pipe 336. The downstream end of the second cooling water discharge pipe 336 is connected to the third heat exchanger 320.

[0081] (Adjustment and processing;) Figure 3 )

[0082] The control device 100 of the third embodiment also performs... Figure 3 The processing of S14, S16, S22, and S26 in the third embodiment differs from that in the first embodiment.

[0083] In S14, the control device 100 calculates multiple target cooling water volumes corresponding to the multiple water electrolysis reactors 16A to 16C respectively. Furthermore, the control device 100 determines the amount of cooling water to be supplied to one or more target water electrolysis reactors, i.e., the target cooling water volume. The target cooling water volume is the target water volume used to achieve a zero voltage difference. The control device 100 determines the target cooling water volume using the current cooling water temperature and voltage difference. Next, the control device 100 calculates the target cooling water volume corresponding to each of the multiple water electrolysis reactors 16A to 16C using the cooling water volume flowing through the multiple second cooling water supply pipes 332A to 332C and the determined target cooling water volume. Additionally, in Figure 4In the case shown, the target cooling water volume corresponding to water electrolyzers 16B and 16C, which are the target water electrolyzers, is greater than the target cooling water volume corresponding to water electrolyzer 16A, which is the reference water electrolyzer.

[0084] In S16, the control device 100 uses multiple target cooling water volumes calculated in S14 to control the operation (opening degree) of multiple second flow regulating valves 340A to 340C. As a result, the cooling water volume supplied to the target water electrolyzer is greater than the cooling water volume supplied to the reference water electrolyzer. Furthermore, the temperature of the target water electrolyzer decreases, and the IV characteristics of the target water electrolyzer change. Consequently, the reactor voltage in the target water electrolyzer corresponding to the target current It is consistent with or approximately equal to the reference voltage.

[0085] Furthermore, in S22, the control device 100 controls the operation of multiple second flow regulating valves 340A to 340C to keep the current difference within a specified value. As an example, when the reactor current of the water electrolysis reactor 16A is at its maximum, the control device 100 controls the operation of the second flow regulating valve 340A to increase the amount of cooling water supplied to the water electrolysis reactor 16A.

[0086] Furthermore, in S26, the control device 100 controls the operation (opening degree) of multiple second flow regulating valves 340A to 340C to ensure that the amount of cooling water supplied to each water electrolysis reactor 16A to 16C is the same.

[0087] As described above, the water electrolysis system 302 also includes multiple second cooling water supply pipes 332A to 332C (an example of "multiple cooling water supply pipes") that are respectively connected to multiple water electrolysis reactors 16A to 16C. Multiple second flow regulating valves 340A to 340C (an example of "at least one temperature regulating unit") are respectively provided on the second cooling water supply pipes 332A to 332C that are connected to the water electrolysis reactors 16A to 16C corresponding to the second flow regulating valves 340A to 340C.

[0088] According to the above structure, the control device 100 can adjust the temperature of the water electrolyzers 16A to 16C by adjusting the amount of cooling water supplied to the water electrolyzers 16A to 16C.

[0089] The above provides a detailed description of specific examples of the technology disclosed in this specification. However, these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes technologies obtained by various modifications and alterations to the specific examples illustrated above.

[0090] (Example 1) The number of water electrolysis reactors is not limited to 3; it can be 2 or more.

[0091] (Second Modification) In the second embodiment Figure 3In S12, the control device 100 can determine the water electrolyzer with the highest performance IV characteristics as the reference water electrolyzer.

[0092] (3rd variation) In Figure 3 In S12, the control device 100 can determine the average value of the stack voltage of multiple water electrolysis stacks 16A to 16C as the target voltage.

[0093] (4th Modification) In the first embodiment, the water electrolysis system 2 only needs to have one or more first flow regulating valves. In this modification, the water electrolysis system 2 can define a water electrolysis stack that does not have a corresponding first flow regulating valve as a reference water electrolysis stack. In the second embodiment, the water electrolysis system 2 also only needs to have one or more second heat exchangers. In the third embodiment, the water electrolysis system 2 also only needs to have one or more second flow regulating valves.

[0094] (5th variation) The water electrolysis system 2 of the first embodiment may have at least one of the second heat exchanger 270A to 270C and the cooling unit 310.

[0095] Furthermore, the technical elements described in this specification or drawings are technically useful individually or in various combinations, and are not limited to the combinations recited in the claims at the time of application. Moreover, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and each of these objectives is technically useful in itself.

[0096] Symbol Explanation

[0097] 2-Water electrolysis system, 10-Power supply unit, 12-Rectifier, 14A~14C-Parallel circuit, 16A~16C-Water electrolysis stack, 18A~18C-Current sensor, 20A~20C-Voltage sensor, 30-Oxygen electrode side unit, 32-Tank, 34-Pump, 36-First heat exchanger, 38-Ion exchanger, 40-First gas-liquid separator, 40C-Second flow control valve, 42A-Valve, 42B-Valve, 42C-Valve, 50-First supply piping, 52A~52C-Second supply piping, 54A~54C-First discharge piping, 56-Second discharge piping, 58-Third discharge piping, 60-Fourth discharge piping, 62-Bypass piping, 70A~70C-First flow control valve, 72A ~72C - Temperature sensor, 80 - Hydrogen electrode side unit, 82 - Second gas-liquid separator, 84A~84C - Fifth discharge pipe, 86 - Sixth discharge pipe, 88 - Seventh discharge pipe, 90 - Eighth discharge pipe, 100 - Control device, 202 - Water electrolysis system, 270A~270C - Second heat exchanger, 302 - Water electrolysis system, 310 - Cooling unit, 320 - Third heat exchanger, 322 - Pump, 330 - First cooling water supply pipe, 332A~332C - Second cooling water supply pipe, 334A~334C - First cooling water discharge pipe, 336 - Second cooling water discharge pipe, 340A~340C - Second flow regulating valve, 342A~342C - Temperature sensor.

Claims

1. A water electrolysis system, characterized in that, have: Power supply unit; Multiple water electrolysis reactors are connected in parallel with respect to the power supply unit; At least one temperature regulating unit is provided for regulating the temperature of at least one of the plurality of water electrolyzers; and A control device that controls the operation of the at least one temperature regulating unit. The control device controls the operation of the at least one temperature regulating unit so that the difference in current flowing through the plurality of water electrolyzers is smaller than when the at least one temperature regulating unit is not activated.

2. The water electrolysis system according to claim 1, characterized in that, It also has: Multiple reaction water supply pipes are respectively connected to the oxygen electrode side of the multiple water electrolysis reactors. Each of the at least one temperature regulating unit is disposed in the reaction water supply pipe connected to the water electrolysis reactor corresponding to the temperature regulating unit, and includes a flow regulating unit that regulates the amount of reaction water passing through the reaction water supply pipe in which the temperature regulating unit is disposed.

3. The water electrolysis system according to claim 1, characterized in that, It also has: Multiple reaction water supply pipes are respectively connected to the oxygen electrode side of the multiple water electrolysis reactors. Each of the at least one temperature regulating unit is disposed in the reaction water supply pipe connected to the water electrolysis reactor corresponding to the temperature regulating unit, and includes a heat exchanger that regulates the temperature of the reaction water passing through the reaction water supply pipe in which the temperature regulating unit is disposed.

4. The water electrolysis system according to claim 1, characterized in that, The water electrolysis system also features: Multiple cooling water supply pipes are respectively connected to the multiple water electrolyzers. Each of the at least one temperature regulating unit is disposed in the cooling water supply pipe connected to the water electrolysis reactor corresponding to the temperature regulating unit, and includes a flow regulating unit that regulates the amount of cooling water passing through the cooling water supply pipe in which the temperature regulating unit is disposed.

5. The water electrolysis system according to claim 1, characterized in that, The at least one temperature regulating unit includes: Multiple temperature control units, each corresponding to one of the multiple water electrolysis reactors.

Images