Water electrolysis system

Abstract

To provide a water electrolysis system capable of shortening a start-up time of a water electrolysis cell stack.SOLUTION: A water electrolysis system 10 comprises a water electrolysis cell stack 12 that generates hydrogen and oxygen by water electrolysis, a water circulation path 14 provided with a pump 22 and supplying water to the water electrolysis cell stack 12, and a power supply device 16 that controls a current supplied to the water electrolysis cell stack 12 at start-up and causes water electrolysis to start from a state where water supplied to the water electrolysis cell stack 12 by the water circulation path 14 is at normal temperature.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water electrolysis system. [Background technology]

[0002] For example, Patent Document 1 discloses a hydrogen production device including an electrolytic cell for electrolyzing water and a rectifier for supplying DC power to the electrolytic cell. The control device for this hydrogen production device has a voltage control unit configured to adjust the output voltage of the rectifier so that the output voltage output from the rectifier to the electrolytic cell matches a set voltage, and a voltage setting unit configured to set the set voltage to a first voltage that is higher than the rated voltage of the electrolytic cell during at least a portion of the start-up of the hydrogen production device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2024-24244 Summary of the Invention [Problem to be solved by the invention]

[0004] The control device for a hydrogen production device described in Patent Document 1 sets the set voltage to a first voltage that is higher than the rated voltage of the electrolytic cell during at least a portion of the start-up period of the hydrogen production device. When the temperature T of the water in the electrolytic cell reaches a specified temperature TC, the control device determines that start-up of the hydrogen production device is complete and starts supplying hydrogen from the hydrogen production device (see, for example, Figure 3 of Patent Document 1). For this reason, it is necessary to wait until the temperature T of the water in the electrolytic cell reaches the specified temperature TC, and there is room for improvement in shortening the start-up time.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to provide a water electrolysis system that can shorten the start-up time of a water electrolysis cell stack. [Means for solving the problem]

[0006] A water electrolysis system according to a first aspect includes a water electrolysis cell stack that produces hydrogen and oxygen by water electrolysis; a water supply channel provided with a pump and that supplies water to the water electrolysis cell stack; and a power supply device that controls a current supplied to the water electrolysis cell stack at startup, thereby starting water electrolysis when the water supplied to the water electrolysis cell stack via the water supply channel is at room temperature.

[0007] In the water electrolysis system according to the first aspect, a pump provided in the water supply channel is driven to supply water to the water electrolysis cell stack. The power supply device controls the current supplied to the water electrolysis cell stack at startup, thereby starting water electrolysis from a state in which the water supplied to the water electrolysis cell stack through the water supply channel is at room temperature. The water electrolysis cell stack generates hydrogen and oxygen through water electrolysis. Therefore, by starting water electrolysis from a state in which the water supplied to the water electrolysis cell stack through the water supply channel is at room temperature, the time during which hydrogen is not generated in the water electrolysis cell stack can be shortened.

[0008] A water electrolysis system according to a second aspect includes a water electrolysis cell stack that produces hydrogen and oxygen through water electrolysis; a water supply channel provided with a pump and that supplies water to the water electrolysis cell stack; a power supply device that controls a voltage supplied to the water electrolysis cell stack at startup and starts water electrolysis when the water supplied to the water electrolysis cell stack via the water supply channel is at room temperature; and a switching controller that switches the control of the power supply device from voltage control to current control when the temperature of the water supplied to the water electrolysis cell stack reaches a predetermined temperature.

[0009] In the water electrolysis system according to the second aspect, water is supplied to the water electrolysis cell stack by driving a pump provided in the water supply channel. The power supply device controls the voltage supplied to the water electrolysis cell stack at startup, thereby starting water electrolysis when the water supplied to the water electrolysis cell stack through the water supply channel is at room temperature. Hydrogen and oxygen are produced by water electrolysis in the water electrolysis cell stack. Furthermore, the switching control unit switches the power supply device from voltage control to current control when the temperature of the water supplied to the water electrolysis cell stack rises to a predetermined temperature. Switching to current control stabilizes the amount of hydrogen produced. Therefore, by starting water electrolysis when the water supplied to the water electrolysis cell stack through the water supply channel is at room temperature, the time during which hydrogen is not produced in the water electrolysis cell stack can be shortened.

[0010] A water electrolysis system according to a third aspect is the water electrolysis system according to the first or second aspect, wherein the water supply channel comprises a water circulation channel that circulates water discharged from the water electrolysis cell stack and supplies the water to the water electrolysis cell stack.

[0011] In the water electrolysis system according to the third aspect, the water supply channel includes a water circulation channel that circulates water discharged from the water electrolysis cell stack and supplies the water to the water electrolysis cell stack, and the water is circulated through the water circulation channel. This allows the temperature of the water circulating through the water circulation channel to be increased by utilizing waste heat generated by water electrolysis in the water electrolysis cell stack. Therefore, hydrogen can be produced by the water electrolysis cell stack while the temperature of the water circulating through the water circulation channel is increasing.

[0012] A water electrolysis system according to a fourth aspect is the water electrolysis system according to the third aspect, wherein the water circulation path is provided with a water separator that separates water discharged from the water electrolysis cell stack from gas, and a water introduction part that introduces new water.

[0013] In the water electrolysis system according to the fourth aspect, the water separator provided in the water circulation path separates water discharged from the water electrolysis cell stack from gas. Furthermore, the water introducing unit introduces new water into the water circulation path. Therefore, the water discharged from the water electrolysis cell stack can be circulated through the water circulation path, and the water can be supplied to the water electrolysis cell stack with the new water introduced.

[0014] A water electrolysis system according to a fifth aspect is the water electrolysis system according to the first aspect, wherein the power supply device has a predetermined upper voltage limit.

[0015] In the water electrolysis system according to the fifth aspect, when water electrolysis is performed in the water electrolysis cell stack by controlling the current, the power supply device has a predetermined upper voltage limit, which makes it possible to suppress deterioration of the catalyst in the water electrolysis cell stack. [Effects of the Invention]

[0016] According to the present disclosure, it is possible to reduce the start-up time of a water electrolysis cell stack. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram illustrating the configuration of a water electrolysis system according to a first embodiment. [Figure 2] 1 is a block diagram showing the hardware configuration of a water electrolysis system according to a first embodiment. FIG. [Figure 3] 1 is a block diagram showing an example of the functional configuration of a water electrolysis system according to a first embodiment; [Figure 4] 4 is a graph showing the relationship between elapsed time and circulating water temperature, electrolysis current density, cell voltage, and hydrogen flow rate in the water electrolysis system according to the first embodiment. [Figure 5] FIG. 6 is a block diagram showing the hardware configuration of a water electrolysis system according to a second embodiment. [Figure 6] FIG. 10 is a block diagram illustrating an example of the functional configuration of a water electrolysis system according to a second embodiment. [Figure 7]10 is a graph showing the relationship between elapsed time and circulating water temperature, electrolysis current density, cell voltage, and hydrogen flow rate in a water electrolysis system according to a second embodiment. [Figure 8] FIG. 10 is a schematic diagram illustrating the configuration of a water electrolysis system according to a third embodiment. [Figure 9] FIG. 1 is a schematic diagram illustrating a water electrolysis system of a comparative example. [Figure 10] 1 is a graph showing the relationship between elapsed time and circulating water temperature, heater state, electrolysis current density, cell voltage, and hydrogen flow rate in a water electrolysis system of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, elements that are less relevant to the technology of the present disclosure are omitted.

[0019] [First embodiment] A water electrolysis system according to a first embodiment will now be described. Fig. 1 shows the overall configuration of a water electrolysis system 10 according to a first embodiment.

[0020] <Water electrolysis system configuration> As shown in Fig. 1, the water electrolysis system 10 includes a water electrolysis cell stack 12, a water circulation path 14, and a power supply 16. The water electrolysis system 10 also includes a control device 50 that controls each component of the water electrolysis system 10. Note that the dotted lines in Fig. 1 may indicate functional relationships that differ from the actual connections.

[0021] (Water electrolysis cell stack) The water electrolysis cell stack 12 generates hydrogen and oxygen through water electrolysis (i.e., electrolysis of water). More specifically, the water electrolysis cell stack 12 is formed by stacking water electrolysis cells (not shown), each of which forms an anode and a cathode with an electrolyte membrane sandwiched between them. When electricity is applied to the water electrolysis cell stack 12 by the power supply device 16, water supplied to the anode is electrolyzed, generating oxygen at the anode and hydrogen at the cathode.

[0022] A supply-side end 14A of a water circulation channel 14 is connected to an anode-side inlet of the water electrolysis cell stack 12, and water is supplied from the supply-side end 14A of the water circulation channel 14. The water circulation channel 14 is an example of a water supply channel. A cathode-side outlet of the water electrolysis cell stack 12 is connected to a hydrogen delivery channel 13, and hydrogen is delivered from the hydrogen delivery channel 13. A discharge-side end 14B of the water circulation channel 14 is connected to an anode-side outlet of the water electrolysis cell stack 12, and oxygen and water are delivered from the discharge-side end 14B of the water circulation channel 14.

[0023] (Water circulation path) The water circulation path 14 circulates water discharged from the water electrolysis cell stack 12 to the discharge end 14B, and supplies water from the supply end 14A to the water electrolysis cell stack 12. In other words, the water circulation path 14 circulates water through the water electrolysis cell stack 12.

[0024] A pump 22 is provided in the water circulation path 14. By driving the pump 22, the water in the water circulation path 14 is circulated.

[0025] In the water electrolysis cell stack 12, heat may be generated by an exothermic reaction when hydrogen and oxygen are produced by water electrolysis. The water electrolysis system 10 of the first embodiment is configured to use waste heat generated by water electrolysis in the water electrolysis cell stack 12 to increase the temperature of water circulating through the water circulation path 14. A temperature sensor 30 is provided near an end 14A on the supply side of the water circulation path 14, which supplies water to the water electrolysis cell stack 12, and detects the temperature of the water.

[0026] A gas-liquid separator 20 is provided in the water circulation path 14. The gas-liquid separator 20 is an example of a water separator and separates water discharged from the water electrolysis cell stack 12 from gas. Specifically, the gas-liquid separator 20 separates oxygen and water from the water circulation path 14 and stores the separated water W. An oxygen delivery path 21 is connected to the gas-liquid separator 20, and oxygen is delivered from the oxygen delivery path 21. As an example, the gas-liquid separator 20 is provided downstream of the water electrolysis cell stack 12 in the water transfer direction of the water circulation path 14 and upstream of the pump 22.

[0027] The water circulation path 14 is provided with a water inlet 24 that introduces fresh pure water. Pure water is an example of fresh water. As an example, the water inlet 24 supplies fresh pure water to the gas-liquid separator 20 disposed in the water circulation path 14. The water inlet 24 includes an inlet path 26 connected between the pure water reservoir 25 and the gas-liquid separator 20 and an adjustment valve 27 that adjusts the flow rate of water flowing through the inlet path 26. The gas-liquid separator 20 is provided with a water level gauge 28 that detects the level of the water W therein, and the adjustment valve 27 is controlled based on the water level detected by the water level gauge 28. For example, when the water level detected by the water level gauge 28 is equal to or lower than a predetermined value, the adjustment valve 27 is opened, and pure water is supplied from the pure water reservoir 25 to the gas-liquid separator 20 via the inlet path 26.

[0028] A heat exchanger 32 and an ion exchange resin 36 are provided along the water circulation path 14. The heat exchanger 32 includes a heat medium circulation path 33 that circulates a heat medium, such as oil, between the heat exchanger 32 and a chiller 34. The chiller 34 is a device that maintains the temperature of the water in the water circulation path 14 at a preset temperature by circulating the heat medium through the heat medium circulation path 33 while managing the liquid temperature of the heat medium. The chiller 34 is often used primarily to cool water. If the temperature of the water in the water circulation path 14 is higher than a predetermined value, it can be cooled by the chiller 34. As an example, the heat exchanger 32 is provided downstream of the pump 22 in the water transfer direction of the water circulation path 14 and upstream of the ion exchange resin 36.

[0029] The ion exchange resin 36 performs ion exchange treatment on the water to remove impurities from the circulating water and maintains the electrical resistivity at a value close to that of theoretically pure water. As an example, the ion exchange resin 36 is provided downstream of the heat exchanger 32 in the water transfer direction of the water circulation path 14 and upstream of the water electrolysis cell stack 12.

[0030] (power supply) The power supply device 16 is electrically connected to the water electrolysis cell stack 12 via wiring 17. The power supply device 16 has a function of operating the water electrolysis cell stack 12 by supplying a direct current to the water electrolysis cell stack 12 via the wiring 17. The power supply device 16 controls the direct current supplied to the water electrolysis cell stack 12.

[0031] As an example, the power supply device 16 is electrically connected to the control device 50, and the control device 50 controls the operation of the power supply device 16. For example, since the direct current supplied to the water electrolysis cell stack 12 is proportional to the amount of hydrogen produced by water electrolysis in the water electrolysis cell stack 12, the amount of hydrogen produced can be adjusted by controlling the direct current using the power supply device 16.

[0032] In the water electrolysis system 10 of the first embodiment, the power supply device 16 controls the current supplied to the water electrolysis cell stack 12 at startup, thereby starting water electrolysis when the water supplied to the water electrolysis cell stack 12 through the water circulation path 14 is at room temperature. For example, the power supply device 16 starts water electrolysis by the water electrolysis cell stack 12 with a current that is permissible when the temperature of the water in the water circulation path 14 is at room temperature (for example, approximately 20°C). This causes hydrogen and oxygen to be generated by water electrolysis in the water electrolysis cell stack 12. At this time, the waste heat from water electrolysis by the water electrolysis system 10 can be used to increase the temperature of the water in the water circulation path 14. In other words, hydrogen can be generated by water electrolysis in the water electrolysis cell stack 12 while the temperature of the water in the water circulation path 14 is increasing.

[0033] Furthermore, the power supply device 16 is provided with a predetermined upper voltage limit. By providing a predetermined upper voltage limit, it is possible to prevent the deterioration of the catalyst in the water electrolysis cell stack 12 from accelerating.

[0034] (Control device) FIG. 2 is a block diagram showing the hardware configuration of the water electrolysis system 10.

[0035] 2, the water electrolysis system 10 includes a control device 50. The control device 50 includes a central processing unit (CPU) 51, a read-only memory (ROM) 52, a random access memory (RAM) 53, a storage 54, and an input / output interface 55. These components are connected to each other via a bus 59 so that they can communicate with each other.

[0036] The CPU 51 is a central processing unit that executes various programs and controls various components. That is, the CPU 51 reads programs from the ROM 52 or the storage 54 and executes the programs using the RAM 53 as a work area. The CPU 51 controls the above components and performs various arithmetic processing in accordance with the programs stored in the ROM 52 or the storage 54. In the first embodiment, the ROM 52 or the storage 54 stores programs that operate the water electrolysis system 10.

[0037] The ROM 52 stores various programs and various data. The RAM 53 serves as a working area and temporarily stores programs or data. The storage 54 is configured with an HDD (Hard Disk Drive) or SSD (Solid State Drive) and stores various programs including the operating system and various data.

[0038] The input / output interface 55 is an interface for transmitting and receiving information to and from each component installed in the water electrolysis system 10. For example, the input / output interface 55 is electrically connected to the power supply device 16, the pump 22, the temperature sensor 30, the current detection unit 62, the voltage detection unit 64, and the hydrogen flow meter 66. As a result, the CPU 51 controls the operations of the power supply device 16 and the pump 22 via the input / output interface 55. The CPU 51 also receives, via the input / output interface 55, the detection values ​​detected by the temperature sensor 30, the current detection unit 62, the voltage detection unit 64, and the hydrogen flow meter 66.

[0039] The current detector 62 is provided in, for example, the water electrolysis cell stack 12, and detects the current in the water electrolysis cell stack 12. The CPU 51 acquires the current detected by the current detector 62 and converts it into an electrolysis current density.

[0040] The voltage detection unit 64 is provided in, for example, the water electrolysis cell stack 12 and detects the cell voltage of the water electrolysis cell stack 12.

[0041] The hydrogen flow meter 66 is provided, for example, in the hydrogen delivery path 13 and detects the hydrogen flow rate in the hydrogen delivery path 13 .

[0042] FIG. 3 is a block diagram showing an example of the functional configuration of the control device 50 in the water electrolysis system 10.

[0043] 3, the water electrolysis system 10 has, as functional components, a circulating water temperature acquisition unit 71, a pump control unit 72, a voltage acquisition unit 73, and a power supply control unit 74. Each functional component is realized by the CPU 51 reading out a program stored in the ROM 52, loading the program into the RAM 53, and executing the program.

[0044] The circulating water temperature acquisition unit 71 acquires the temperature of the circulating water in the water circulation path 14 detected by the temperature sensor 30 .

[0045] The pump control unit 72 controls the driving of the pump 22. By driving the pump 22, water is circulated through the water circulation path .

[0046] The voltage acquisition unit 73 acquires the cell voltage detected by the voltage detection unit 64 .

[0047] The power supply device control unit 74 controls the operation of the power supply device 16. In the first embodiment, the power supply device 16 controls the DC current supplied to the water electrolysis cell stack 12, but the power supply device control unit 74 may also control the DC current of the power supply device 16. Furthermore, the power supply device control unit 74 may control the DC current supplied from the power supply device 16 to the water electrolysis cell stack 12 based on, for example, the cell voltage detected by the voltage detection unit 64 so as not to exceed a predetermined upper voltage limit.

[0048] (Operation example of water electrolysis system 10) Next, an example of operation of the water electrolysis system 10 will be described.

[0049] FIG. 4 is a graph showing the relationship between elapsed time and the circulating water temperature, electrolysis current density, cell voltage, and hydrogen flow rate in the water electrolysis system 10. As shown in FIG. 4, when no current is supplied to the water electrolysis cell stack 12, the temperature of the water circulating through the water circulation path 14 is 20°C. In the water electrolysis system 10, the time when current is supplied to the water electrolysis cell stack 12 is defined as the start-up time (e.g., point 1:00 in the graph shown in FIG. 4). In the water electrolysis system 10, water electrolysis is initiated when the water supplied to the water electrolysis cell stack 12 through the water circulation path 14 is at room temperature (e.g., about 20°C) by controlling the current supplied from the power supply device 16 to the water electrolysis cell stack 12 at start-up. In the water electrolysis system 10, hydrogen and oxygen are produced by water electrolysis. For example, when the circulating water in the water circulation path 14 is at room temperature (e.g., about 20°C), the electrolysis current density of the water electrolysis cell stack 12 increases, and the hydrogen flow rate increases (see FIG. 4).

[0050] In addition, the temperature of the circulating water in the water circulation path 14 is increased by utilizing the exhaust heat from the water electrolysis cell stack 12. For example, the temperature of the circulating water gradually increases to approximately 80°C (see FIG. 4). In this state, the current of the power supply 16 is controlled to be approximately constant, thereby maintaining an approximately constant hydrogen flow rate (see FIG. 4). The amount of hydrogen produced by the water electrolysis cell stack 12 corresponds to the value of the current supplied from the power supply 16.

[0051] <Action and effect> Next, the operation and effects of the first embodiment will be described.

[0052] In the water electrolysis system 10, water is supplied to the water electrolysis cell stack 12 by driving a pump 22 provided in the water circulation path 14. The power supply device 16 controls the current supplied to the water electrolysis cell stack 12 at startup, so that water electrolysis is initiated when the water supplied to the water electrolysis cell stack 12 via the water circulation path 14 is at room temperature. In the water electrolysis cell stack 12, hydrogen and oxygen are produced by water electrolysis. Therefore, by starting water electrolysis when the water supplied to the water electrolysis cell stack 12 via the water circulation path 14 is at room temperature, the time during which hydrogen is not generated in the water electrolysis cell stack 12 can be shortened.

[0053] The water electrolysis system 10 is also provided with a water circulation path 14 that circulates water discharged from the water electrolysis cell stack 12 and supplies the water to the water electrolysis cell stack 12, and the water is circulated through the water circulation path 14. In this way, the temperature of the water circulating through the water circulation path 14 is increased by utilizing waste heat generated by water electrolysis in the water electrolysis cell stack 12. Therefore, in the water electrolysis system 10, hydrogen can be produced by the water electrolysis cell stack 12 while the temperature of the water circulating through the water circulation path 14 is increasing.

[0054] In the water electrolysis system 10, the gas-liquid separator 20 provided in the water circulation path 14 separates the water discharged from the water electrolysis cell stack 12 from the gas. Furthermore, the water introducing unit 24 introduces new pure water into the gas-liquid separator 20 of the water circulation path 14. Therefore, in the water electrolysis system 10, the water discharged from the water electrolysis cell stack 12 is circulated through the water circulation path 14, and water can be supplied to the water electrolysis cell stack 12 with new pure water introduced.

[0055] Furthermore, the power supply device 16 is provided with a predetermined upper voltage limit. That is, when water electrolysis is performed in the water electrolysis cell stack 12 by controlling the current, the power supply device 16 has a predetermined upper voltage limit, so that the water electrolysis system 10 can suppress deterioration of the catalyst in the water electrolysis cell stack 12.

[0056] A comparative example of a water electrolysis system 500 will now be described. Fig. 9 is a schematic diagram showing the configuration of the comparative example of a water electrolysis system 500.

[0057] 9 , a water electrolysis system 500 of the comparative example includes a heater 502 disposed on the water supply side of the water circulation channel 14. The heater 502 increases the temperature of the water in the water circulation channel 14. The heater 502 is disposed downstream of the ion exchange resin 36 in the water transfer direction of the water circulation channel 14 and upstream of the water electrolysis cell stack 12 and the temperature sensor 30.

[0058] Fig. 10 is a graph showing the relationship between elapsed time and the circulating water temperature, heater temperature, electrolysis current density, cell voltage, and hydrogen flow rate in a water electrolysis system 500 of a comparative example. As shown in Fig. 10, at start-up of the water electrolysis system 500, the heater 502 is turned on and the pump 22 is driven to circulate water through the water circulation path 14. This causes the heat from the heater 502 to increase the temperature of the circulating water in the water circulation path 14. Thereafter, when the temperature sensor 30 detects that the temperature of the circulating water has reached a predetermined temperature (e.g., 80°C), the water electrolysis system 500 determines that start-up is complete. The time for which the heater 502 increases the temperature of the circulating water in the water circulation path 14 is, for example, approximately one hour.

[0059] Thereafter, in the water electrolysis system 500, the power supply device (not shown) gradually increases the current supplied to the water electrolysis cell stack 12 to operate the water electrolysis cell stack 12 at a predetermined current density, thereby causing the water electrolysis cell stack 12 to produce hydrogen and oxygen through water electrolysis.

[0060] The water electrolysis system 500 requires the installation of a heater 502. Furthermore, the use of the heater 502 increases power consumption at startup. Furthermore, it takes time to increase the temperature of the circulating water in the water circulation path 14. Furthermore, while the temperature of the circulating water in the water circulation path 14 is increasing, the water electrolysis cell stack 12 is not producing hydrogen.

[0061] In contrast, in the water electrolysis system 10 of the first embodiment, water is supplied to the water electrolysis cell stack 12 by driving the pump 22 provided in the water circulation path 14. The power supply device 16 controls the current supplied to the water electrolysis cell stack 12 at start-up, so that water electrolysis starts when the water supplied to the water electrolysis cell stack 12 via the water circulation path 14 is at room temperature. This eliminates the need for a heater in the water electrolysis system 10. Furthermore, the water electrolysis system 10 can shorten the start-up time of the water electrolysis cell stack 12.

[0062] Second Embodiment Next, a water electrolysis system according to a second embodiment will be described. Note that the same components as those in the first embodiment will be assigned the same reference numerals and descriptions thereof will be omitted.

[0063] Fig. 5 is a block diagram showing the hardware configuration of a water electrolysis system 100 according to a second embodiment. As shown in Fig. 5, the water electrolysis system 100 differs from the water electrolysis system 10 of the first embodiment in that it includes a power supply device 102 and a control device 110. That is, the configuration of each component of the water electrolysis system 100 is similar to the configuration of each component of the water electrolysis system 10 of the first embodiment shown in Fig. 1, but the power supply device 102 and the control device 110 are different. The control device 110 controls the operation of the power supply device 102.

[0064] The power supply device 102 controls the voltage supplied to the water electrolysis cell stack 12 at startup, and starts water electrolysis when the water supplied to the water electrolysis cell stack 12 through the water circulation path 14 is at room temperature. Furthermore, when the temperature of the water inside the water electrolysis cell stack 12 rises to a predetermined temperature, the control device 110 switches the control of the power supply device 102 from voltage control to current control.

[0065] FIG. 6 is a block diagram showing an example of the functional configuration of the control device 110 in the water electrolysis system 100.

[0066] 6, the water electrolysis system 100 has, as functional components, a circulating water temperature acquisition unit 71, a pump control unit 72, a voltage control unit 121, and a switching control unit 122. Each functional component is realized by the CPU 51 reading out a program stored in the ROM 52, loading the program into the RAM 53, and executing the program.

[0067] The voltage control unit 121 controls the voltage supplied from the power supply device 102 to the water electrolysis cell stack 12. In the second embodiment, the voltage control unit 121 controls the voltage supplied from the power supply device 102 to the water electrolysis cell stack 12 at startup, thereby starting water electrolysis from a state in which the water supplied to the water electrolysis cell stack 12 through the water circulation path 14 is at room temperature.

[0068] When the temperature of the water supplied to the water electrolysis cell stack 12 rises to a predetermined temperature, the switching control unit 122 switches the power supply device 102 from voltage control to current control. Furthermore, the switching control unit 122 controls the current supplied from the power supply device 102 to the water electrolysis cell stack 12. The temperature of the water supplied to the water electrolysis cell stack 12 is, for example, the temperature of the water detected by the temperature sensor 30.

[0069] Next, an example of operation of the water electrolysis system 100 will be described.

[0070] Fig. 7 is a graph showing the relationship between elapsed time and the circulating water temperature, electrolysis current density, cell voltage, and hydrogen flow rate in the water electrolysis system 100. As shown in Fig. 7, the water electrolysis system 100 starts water electrolysis when the water supplied to the water electrolysis cell stack 12 via the water circulation path 14 is at room temperature (e.g., approximately 20°C) by controlling the voltage of the power supply device 102 at startup. For example, the power supply device 102 starts water electrolysis in the water electrolysis cell stack 12 at a voltage that does not accelerate deterioration of the catalyst in the water electrolysis cell stack 12. As a result, hydrogen and oxygen are produced by water electrolysis in the water electrolysis cell stack 12. During this process, the temperature of the circulating water in the water circulation path 14 increases, and the electrolysis current density in the water electrolysis cell stack 12 also increases (see Fig. 7).

[0071] 7, constant voltage control is performed by the power supply device 102. Constant voltage control is one of the control methods for the power supply circuit of the power supply device 102, and refers to control so that the voltage value is always constant.

[0072] In the water electrolysis system 100, the temperature of the circulating water in the water circulation path 14 is increased by utilizing the waste heat from the water electrolysis cell stack 12.

[0073] When the temperature of the water supplied to the water electrolysis cell stack 12 rises to a predetermined temperature, the control device 110 switches the power supply device 102 from voltage control to current control. For example, when the temperature of the circulating water in the water circulation path 14 detected by the temperature sensor 30 rises to a predetermined temperature (e.g., 70°C), the control device 110 switches the power supply device 102 from voltage control to current control.

[0074] 7, constant current control is performed by the power supply device 102. Constant current control is a control method for the power supply circuit of the power supply device 102, and refers to control so that the current value is always constant. As a result, the amount of hydrogen produced by the water electrolysis cell stack 12 corresponds to the value of the current supplied from the power supply device 102. The other configurations of the water electrolysis system 100 of the second embodiment are similar to those of the water electrolysis system 10 of the first embodiment.

[0075] Next, the operation and effects of the second embodiment will be described.

[0076] In the water electrolysis system 100, water is supplied to the water electrolysis cell stack 12 by driving a pump 22 provided in the water circulation channel 14. The power supply device 102 controls the voltage supplied to the water electrolysis cell stack 12 at startup, thereby starting water electrolysis from a state in which the water supplied to the water electrolysis cell stack via the water circulation channel 14 is at room temperature. Hydrogen and oxygen are produced by water electrolysis in the water electrolysis cell stack 12. Furthermore, the switching control unit 122 of the control device 110 switches the power supply device 102 from voltage control to current control when the temperature of the water supplied to the water electrolysis cell stack 12 rises to a predetermined temperature. Switching the power supply device 102 to current control stabilizes the amount of hydrogen produced. Therefore, by starting water electrolysis from a state in which the water supplied to the water electrolysis cell stack 12 via the water circulation channel 14 is at room temperature, the time during which hydrogen is not produced in the water electrolysis cell stack 12 can be shortened.

[0077] This eliminates the need for a heater in the water electrolysis system 100. Furthermore, the water electrolysis system 100 enables the start-up time of the water electrolysis cell stack 12 to be shortened.

[0078] Furthermore, the water electrolysis system 100 has the same configuration as the water electrolysis system 10 of the first embodiment, and can provide the same functions and effects.

[0079] Third Embodiment Next, a water electrolysis system according to a third embodiment will be described. Note that the same components as those in the first and second embodiments are designated by the same reference numerals, and description thereof will be omitted.

[0080] Fig. 8 is a schematic diagram showing a water electrolysis system 200 according to a third embodiment. As shown in Fig. 8, the water electrolysis system 200 differs from the water electrolysis system 10 according to the first embodiment in that it includes a water supply channel 202 that supplies water to the water electrolysis cell stack 12. A gas-liquid separator 20 and a water introduction section 24 are provided upstream of the water supply channel 202 in the direction of water flow.

[0081] The water supply channel 202 is provided with a pump 22 and an ion exchange resin 36. By driving the pump 22, water from the gas-liquid separator 20 is introduced into the water supply channel 202, and the water is further supplied to the water electrolysis cell stack 12 through the water supply channel 202. As an example, the pump 22 is arranged downstream of the gas-liquid separator 20 in the direction of water flow in the water supply channel 202 and upstream of the ion exchange resin 36. The ion exchange resin 36 is arranged downstream of the pump 22 in the direction of water flow in the water supply channel 202 and upstream of the water electrolysis cell stack 12.

[0082] The water electrolysis cell stack 12 is provided with a temperature sensor 204 that measures the temperature of the water inside. Furthermore, the water electrolysis cell stack 12 is provided with a hydrogen delivery path 13 that delivers hydrogen and an oxygen delivery path 206 that delivers oxygen.

[0083] The water electrolysis system 200 also includes a power supply device 16. The power supply device 16 controls the current supplied to the water electrolysis cell stack 12 at startup, thereby starting water electrolysis from a state in which the water supplied to the water electrolysis cell stack 12 through the water circulation path 14 is at room temperature. Other configurations of the water electrolysis system 200 of the third embodiment are similar to those of the water electrolysis system 10 of the first embodiment.

[0084] Next, the operation and effects of the third embodiment will be described.

[0085] In the water electrolysis system 200, water is supplied to the water electrolysis cell stack 12 by driving a pump 22 provided in a water supply channel 202. The power supply device 16 controls the current supplied to the water electrolysis cell stack 12 at startup, so that water electrolysis is initiated when the water supplied to the water electrolysis cell stack 12 via the water supply channel 202 is at room temperature. In the water electrolysis cell stack 12, hydrogen and oxygen are produced by water electrolysis. Therefore, by starting water electrolysis when the water supplied to the water electrolysis cell stack via the water supply channel 202 is at room temperature, the time during which hydrogen is not generated in the water electrolysis cell stack 12 can be shortened.

[0086] This eliminates the need for a heater in the water electrolysis system 200. Furthermore, the water electrolysis system 200 enables the start-up time of the water electrolysis cell stack 12 to be shortened.

[0087] Furthermore, the water electrolysis system 200 has the same configuration as the water electrolysis system 10 of the first embodiment, and can therefore achieve the same functions and effects.

[0088] Although the water electrolysis system 200 is provided with the power supply device 16, the present disclosure is not limited to this configuration. For example, the power supply device 102 may be provided instead of the power supply device 16, as in the water electrolysis system 100 of the second embodiment, and the power supply device 102 may be operated in the same manner as in the water electrolysis system 100 of the second embodiment.

[0089] 〔supplementary explanation〕 In the water electrolysis systems 10, 100, and 200 according to the first to third embodiments, the configuration of each component may be changed or other devices may be added without departing from the scope of the present disclosure.

[0090] Although the embodiments of the present disclosure have been described above, these embodiments are merely examples and can be modified in various ways without departing from the spirit of the present disclosure. Furthermore, it goes without saying that the scope of the present disclosure is not limited to these embodiments and can be embodied in various ways without departing from the spirit of the present disclosure. [Explanation of symbols]

[0091] 10...water electrolysis system, 12...water electrolysis cell stack, 14...water circulation path (water supply path), 16...power supply device, 20...gas-liquid separator (water separator), 22...pump, 24...water introduction section, 100...water electrolysis system, 102...power supply device, 122...switching control section, 200...water electrolysis system, 202...water supply path

Claims

1. a water electrolysis cell stack that generates hydrogen and oxygen by water electrolysis; a water supply channel provided with a pump and supplying water to the water electrolysis cell stack; a power supply device that controls a current supplied to the water electrolysis cell stack at startup, and starts water electrolysis when the water supplied to the water electrolysis cell stack through the water supply channel is at room temperature; A water electrolysis system having the above structure.

2. a water electrolysis cell stack that generates hydrogen and oxygen by water electrolysis; a water supply channel provided with a pump and supplying water to the water electrolysis cell stack; a power supply device that controls a voltage supplied to the water electrolysis cell stack at startup, and starts water electrolysis when the water supplied to the water electrolysis cell stack through the water supply channel is at room temperature; a switching control unit that switches the power supply device from voltage control to current control when the temperature of the water supplied to the water electrolysis cell stack rises to a predetermined temperature; A water electrolysis system having the above structure.

3. 3. The water electrolysis system according to claim 1, wherein the water supply passage comprises a water circulation passage that circulates water discharged from the water electrolysis cell stack and supplies the water to the water electrolysis cell stack.

4. 4. The water electrolysis system according to claim 3, wherein the water circulation path is provided with a water separator that separates water discharged from the water electrolysis cell stack from gas, and a water inlet that introduces new water.

5. The water electrolysis system according to claim 1 , wherein the power supply device has a predetermined upper voltage limit.

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