Water electrolysis system

Abstract

To obtain a water electrolysis system that can reduce costs. [Solution] The water electrolysis system comprises a water electrolysis cell stack that generates hydrogen and oxygen by water electrolysis, a water supply path equipped with a pump that supplies water to the water electrolysis cell stack, a power supply device that supplies current to the water electrolysis cell stack, a temperature sensor that detects the temperature of the water to be reacted in the water electrolysis cell stack, and a control device that controls the temperature of the water to be reacted in the water electrolysis cell stack by controlling the current of the power supply device based on the temperature detected by the temperature sensor, thereby increasing or decreasing the waste heat from water electrolysis in the water electrolysis cell stack.

Description

Technical Field

[0004]

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

Background Art

[0002] For example, Patent Document 1 discloses a water electrolysis system including a differential pressure type high-pressure water electrolysis device, a water supply pipe for supplying water to a water supply port of the differential pressure type high-pressure water electrolysis device, and a water discharge pipe for discharging water from a water discharge port of the differential pressure type high-pressure water electrolysis device. A radiator for cooling water is provided in the water supply pipe, and a first temperature sensor is provided between the radiator and the water supply port to monitor the temperature of the supply water supplied to the water supply port. A second temperature sensor for monitoring the temperature of the discharged water discharged from the water discharge port is provided in the water discharge pipe.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the water electrolysis system described in Patent Document 1, after the temperature of the discharged water monitored by the second temperature sensor exceeds a predetermined temperature, the temperature of the supply water supplied to the water supply port is monitored by the first temperature sensor, and control by the radiator is started to control the temperature of the supply water. Therefore, it is necessary to mount a radiator for cooling the supply water, and power for controlling the radiator is required, resulting in an increase in power consumption. For this reason, in the above water electrolysis system, the cost for mounting and operating the radiator increases.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a water electrolysis system capable of reducing costs.

Means for Solving the Problems

[0006] The water electrolysis system described in the first embodiment includes a water electrolysis cell stack that generates hydrogen and oxygen by water electrolysis, a water supply path provided with a pump that supplies water to the water electrolysis cell stack, a power supply device that supplies current to the water electrolysis cell stack, a temperature sensor that detects the temperature of the water to be reacted in the water electrolysis cell stack, and a control device that controls the temperature of the water to be reacted in the water electrolysis cell stack by controlling the current of the power supply device based on the temperature detected by the temperature sensor, thereby increasing or decreasing the waste heat from water electrolysis in the water electrolysis cell stack.

[0007] In the water electrolysis system described in the first embodiment, water is supplied to the water electrolysis cell stack by driving a pump installed in the water supply path. By supplying current to the water electrolysis cell stack by a power supply device, hydrogen and oxygen are generated in the water electrolysis cell stack by water electrolysis. In addition, the temperature of the water to be reacted in the water electrolysis cell stack is detected by a temperature sensor. The control device increases or decreases the waste heat from water electrolysis in the water electrolysis cell stack by controlling the current of the power supply device based on the temperature detected by the temperature sensor. This controls the temperature of the water to be reacted in the water electrolysis cell stack. Therefore, it is not necessary to install a heater or the like in the water supply path to raise the water temperature, and the power consumption required to operate the heater can be reduced.

[0008] The water electrolysis system described in the second embodiment is the water electrolysis system described in the first embodiment, wherein the water supply path consists of a water circulation path that circulates water discharged from the water electrolysis cell stack and supplies it to the water electrolysis cell stack, the temperature sensor is provided in the middle of the water circulation path and detects the temperature of the water flowing through the water circulation path, and the control device controls the current of the power supply device based on the temperature detected by the temperature sensor to increase or decrease the waste heat from water electrolysis in the water electrolysis cell stack and control the temperature of the water circulating in the water circulation path.

[0009] In the water electrolysis system described in the second embodiment, a pump installed in the water circulation path is driven to circulate water discharged from the water electrolysis cell stack and supply it to the water electrolysis cell stack. A temperature sensor is installed in the middle of the water circulation path, and the temperature of the water flowing through the water circulation path is detected by the temperature sensor. The control device controls the current of the power supply unit based on the temperature detected by the temperature sensor, thereby increasing or decreasing the waste heat from water electrolysis in the water electrolysis cell stack. This controls the temperature of the water circulating in the water circulation path. As a result, it is not necessary to install a heater to raise the temperature of the water circulating in the water circulation path or a chiller to lower the temperature of the water, and the power consumption required to operate the heater or chiller can be reduced.

[0010] The water electrolysis system according to the third embodiment is the water electrolysis system according to the first embodiment, wherein when the temperature detected by the temperature sensor falls below a first threshold, the control device increases the current of the power supply and increases the waste heat from water electrolysis in the water electrolysis cell stack, thereby raising the temperature of the water to be reacted in the water electrolysis cell stack.

[0011] In the water electrolysis system described in the third embodiment, when the temperature detected by the temperature sensor falls below a first threshold, the control device increases the current of the power supply, increases the waste heat from water electrolysis in the water electrolysis cell stack, and raises the temperature of the water used for the reaction in the water electrolysis cell stack. As a result, it becomes unnecessary to install heaters or other devices in the water supply path to raise the water temperature, and power consumption can be reduced more reliably.

[0012] The water electrolysis system according to the fourth embodiment, in the water electrolysis system according to the first embodiment, the control device reduces the current of the power supply and decreases the waste heat from water electrolysis in the water electrolysis cell stack when the temperature detected by the temperature sensor rises to a second threshold, thereby lowering the temperature of the water to be reacted in the water electrolysis cell stack.

[0013] In the water electrolysis system described in the fourth embodiment, when the temperature detected by the temperature sensor rises above a second threshold, the control device reduces the current of the power supply, thereby reducing the waste heat from water electrolysis in the water electrolysis cell stack and lowering the temperature of the water used for the reaction in the water electrolysis cell stack. As a result, it becomes unnecessary to install chillers or other devices in the water supply path to lower the water temperature, and power consumption can be reduced more reliably.

[0014] The water electrolysis system according to the fifth embodiment is the water electrolysis system according to the second embodiment, wherein when the temperature detected by the temperature sensor falls below a first threshold, the control device increases the current of the power supply and increases the waste heat from water electrolysis in the water electrolysis cell stack, thereby raising the temperature of the water circulating in the water circulation path.

[0015] In the water electrolysis system described in the fifth embodiment, when the temperature detected by the temperature sensor falls below a first threshold, the control device increases the current of the power supply, increases the waste heat from water electrolysis in the water electrolysis cell stack, and raises the temperature of the water circulating in the water circulation path. As a result, it becomes unnecessary to install heaters or other devices to raise the water temperature in the water circulation path, and power consumption can be reduced more reliably.

[0016] The water electrolysis system according to the sixth embodiment is the water electrolysis system according to the second embodiment, wherein when the temperature detected by the temperature sensor rises to a second threshold, the control device reduces the current of the power supply and reduces the waste heat from water electrolysis in the water electrolysis cell stack, thereby lowering the temperature of the water circulating in the water circulation path.

[0017] In the water electrolysis system described in the sixth embodiment, when the temperature detected by the temperature sensor rises above a second threshold, the control device reduces the current of the power supply, thereby reducing the heat generated during water electrolysis in the water electrolysis cell stack and lowering the temperature of the water circulating in the water circulation path. As a result, it becomes unnecessary to install chillers or other devices in the water circulation path to lower the water temperature, and power consumption can be reduced more reliably.

[0018] In the water electrolysis system according to the seventh aspect, in the water electrolysis system according to the second aspect, in the water circulation path, on the downstream side of the water electrolysis cell stack in the water flow direction of the water circulation path and on the upstream side of the temperature sensor, a water separator for separating water discharged from the water electrolysis cell stack from gas and a water introduction part for introducing new water are provided.

[0019] In the water electrolysis system according to the seventh aspect, water discharged from the water electrolysis cell stack is separated from gas by a water separator provided in the water circulation path. Further, new water is introduced into the water circulation path by the water introduction part. Therefore, it is possible to circulate the water discharged from the water electrolysis cell stack in the water circulation path and supply water to the water electrolysis cell stack in a state where new water is introduced. In addition, since the water separator and the water introduction part are provided on the downstream side of the water electrolysis cell stack in the water flow direction of the water circulation path and on the upstream side of the temperature sensor, the temperature of the water supplied to the water electrolysis cell stack can be more reliably controlled.

[0020] In the water electrolysis system according to the eighth aspect, in the water electrolysis system according to the first aspect, the power supply device is provided with a predetermined voltage upper limit.

[0021] In the water electrolysis system according to the eighth aspect, when performing water electrolysis in the water electrolysis cell stack by controlling the current, since the power supply device is provided with a predetermined voltage upper limit, deterioration of the catalyst of the water electrolysis cell stack can be suppressed.

Effect of the Invention

[0022] According to the present disclosure, the cost of the water electrolysis system can be reduced.

Brief Description of the Drawings

[0023] [Figure 1] It is a schematic configuration diagram showing a water electrolysis system according to the first embodiment. [[ID=二十九]] [Figure 2] It is a block diagram showing the hardware configuration of the water electrolysis system according to the first embodiment. [Figure 3] It is a block diagram showing an example of the functional configuration of the water electrolysis system according to the first embodiment. [Figure 4] It is a graph showing the relationship between the elapsed time, the circulating water temperature, the electrolysis current density, and the hydrogen flow rate in the water electrolysis system according to the first embodiment. [Figure 5] It is a schematic configuration diagram showing the water electrolysis system according to the second embodiment. [Figure 6] It is a block diagram showing the hardware configuration of the water electrolysis system according to the second embodiment. [Figure 7] It is a block diagram showing an example of the functional configuration of the water electrolysis system according to the second embodiment. [Figure 8] It is a graph showing the relationship between the elapsed time, the circulating water temperature, the electrolysis current density, and the hydrogen flow rate in the water electrolysis system according to the second embodiment. [Figure 9] It is a schematic configuration diagram showing the water electrolysis system of the comparative example. [Figure 10] It is a graph showing the relationship between the elapsed time, the circulating water temperature, the electrolysis current density, the state of the heater, the state of the chiller, and the hydrogen flow rate in the water electrolysis system of the comparative example.

Mode for Carrying Out the Invention

[0024] Hereinafter, embodiments of the present disclosure will be described based on the drawings. In each drawing, those having low relevance to the technology of the present disclosure are omitted from illustration.

[0025] 〔First Embodiment〕 The water electrolysis system according to the first embodiment will be described. In FIG. 1, the overall configuration of the water electrolysis system 10 according to the first embodiment is shown.

[0026] <Configuration of the water electrolysis system> As shown in Figure 1, the water electrolysis system 10 comprises a water electrolysis cell stack 12, a water circulation path 14, a power supply unit 16, and a temperature sensor 30. Furthermore, the water electrolysis system 10 includes a control device 50 that controls each part of the water electrolysis system 10. Note that the dotted lines in Figure 1 include cases that show functional relationships that differ from the actual connection relationships.

[0027] (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) that form an anode and a cathode with an electrolyte membrane in between. In the water electrolysis cell stack 12, when power is supplied by the power supply unit 16, the water supplied to the anode is electrolyzed, generating oxygen at the anode and hydrogen at the cathode.

[0028] The supply end 14A of the water circulation path 14 is connected to the anode inlet of the water electrolysis cell stack 12, and water is supplied from the supply end 14A of the water circulation path 14. The hydrogen discharge path 38 is connected to the cathode outlet of the water electrolysis cell stack 12, and hydrogen is discharged from the hydrogen discharge path 38. The discharge end 14B of the water circulation path 14 is connected to the anode outlet of the water electrolysis cell stack 12, and oxygen and water are discharged from the discharge end 14B of the water circulation path 14.

[0029] (Water circulation path and temperature sensor) The water circulation path 14 circulates the water discharged from the water electrolysis cell stack 12 to the discharge end 14B, and supplies water to the water electrolysis cell stack 12 from the supply end 14A. In other words, the water circulation path 14 circulates water via the water electrolysis cell stack 12. The water circulation path 14 is an example of a water supply path.

[0030] A pump 22 is installed in the middle of the water circulation path 14. By driving the pump 22, the water in the water circulation path 14 is circulated.

[0031] In the water electrolysis cell stack 12, heat may be generated due to an exothermic reaction when hydrogen and oxygen are produced by water electrolysis. The water electrolysis system 10 is configured to utilize the waste heat from water electrolysis in the water electrolysis cell stack 12 to raise the temperature of the water circulating in the water circulation path 14.

[0032] The temperature sensor 30 is located near the supply end 14A of the water circulation path 14 that supplies water to the water electrolysis cell stack 12. For example, the temperature sensor 30 is located downstream of the pump 22 and the ion exchange resin 36 (described later) in the water flow direction of the water circulation path 14, and upstream of the water electrolysis cell stack 12. The temperature sensor 30 detects the temperature of the water flowing through the water circulation path 14. In other words, the temperature sensor 30 detects the temperature of the water used for the reaction in the water electrolysis cell stack 12.

[0033] A gas-liquid separator 20 is provided in the middle of the water circulation path 14. The gas-liquid separator 20 is an example of a water separator and separates the water discharged from the water electrolysis cell stack 12 from the 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 supply passage 21 is connected to the gas-liquid separator 20, and oxygen is supplied from the oxygen supply passage 21. As an example, the gas-liquid separator 20 is provided downstream of the water electrolysis cell stack 12 in the water circulation path 14's water transfer direction (i.e., the water flow direction) and upstream of the pump 22.

[0034] The water circulation path 14 is equipped with a water inlet 24 for introducing new pure water. Pure water is an example of new water. New water is pure water supplied from outside the water electrolysis system 10. For example, the water inlet 24 supplies new pure water into the gas-liquid separator 20 located in the water circulation path 14. The water inlet 24 includes an inlet passage 26 connected between the pure water storage section 25 and the gas-liquid separator 20, and a control valve 27 for adjusting the flow rate of water through the inlet passage 26. The gas-liquid separator 20 is equipped with a water level gauge 28 for detecting the water level of the water W inside, and the control 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 falls below a predetermined value, the control valve 27 is opened, and pure water is supplied from the pure water storage section 25 to the gas-liquid separator 20 via the inlet passage 26.

[0035] An ion exchange resin 36 is provided in the middle of the water circulation path 14. The ion exchange resin 36 removes impurities from the circulating water by ion exchange treatment and maintains the electrical resistivity at a value close to the electrical exchange rate of theoretically pure water. As an example, the ion exchange resin 36 is provided downstream of the pump 22 in the water transfer direction of the water circulation path 14 and upstream of the water electrolysis cell stack 12 and the temperature sensor 30.

[0036] (power supply) The power supply unit 16 is electrically connected to the water electrolysis cell stack 12 by wiring 17. The power supply unit 16 has the function of operating the water electrolysis cell stack 12 by supplying current (e.g., DC current) to the water electrolysis cell stack 12 via the wiring 17.

[0037] For example, the power supply unit 16 is electrically connected to the control device 50, and the control device 50 controls the operation of the power supply unit 16. For example, the control device 50 controls the current (e.g., DC current) supplied from the power supply unit 16 to the water electrolysis cell stack 12. For example, since the DC 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 DC current of the power supply unit 16 with the control device 50.

[0038] Furthermore, the power supply unit 16 is provided with a predetermined voltage limit. By providing a predetermined voltage limit, it is possible to prevent the deterioration of the catalyst in the water electrolysis cell stack 12 from accelerating. The voltage limit may be a limit controlled by the power supply unit 16, or an upper limit may be set by the power supply unit 16 itself. For example, a protection circuit, a voltage regulator, or a Zener diode can be used to set the upper limit of the power supply unit 16.

[0039] (Control device) Figure 2 is a block diagram showing the hardware configuration of the water electrolysis system 10.

[0040] As shown in Figure 2, the water electrolysis system 10 includes a control device 50. The control device 50 consists of a CPU (Central Processing Unit) 51, ROM (Read Only Memory) 52, RAM (Random Access Memory) 53, storage 54, and an input / output interface 55. Each component is connected to the others via a bus 59 so that they can communicate with each other.

[0041] The CPU 51 is a central processing unit that executes various programs and controls various parts. Specifically, the CPU 51 reads a program from the ROM 52 or storage 54 and executes the program using the RAM 53 as a working area. The CPU 51 controls each of the above components and performs various calculations according to the program stored in the ROM 52 or storage 54. In the first embodiment, the ROM 52 or storage 54 stores a program for operating the water electrolysis system 10.

[0042] ROM 52 stores various programs and data. RAM 53 temporarily stores programs or data as a working area. Storage 54 consists of an HDD (Hard Disk Drive) or SSD (Solid State Drive) and stores various programs, including the operating system, and various data.

[0043] The input / output interface 55 is an interface for sending and receiving information between the CPU and each component mounted on the water electrolysis system 10. For example, the input / output interface 55 is electrically connected to the power supply unit 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 operation of the power supply unit 16 and the pump 22 via the input / output interface 55. The CPU 51 also receives detection values ​​detected by the temperature sensor 30, the current detection unit 62, the voltage detection unit 64, and the hydrogen flow meter 66, respectively, via the input / output interface 55.

[0044] The current detection unit 62 is provided, for example, in the water electrolysis cell stack 12 and detects the current of the water electrolysis cell stack 12. The CPU 51 acquires the current detected by the current detection unit 62 and converts it into an electrolysis current density.

[0045] The voltage detection unit 64 is provided, for example, in the water electrolysis cell stack 12 and detects the cell voltage of the water electrolysis cell stack 12.

[0046] The hydrogen flow meter 66 is installed, for example, in the hydrogen delivery passage 38 and detects the hydrogen flow rate in the hydrogen delivery passage 38.

[0047] Figure 3 is a block diagram showing an example of the functional configuration of the control device 50 in the water electrolysis system 10.

[0048] As shown in Figure 3, the control device 50 in the water electrolysis system 10 has a functional configuration consisting of a circulating water temperature acquisition unit 71, a pump control unit 72, a current density acquisition unit 73, and a power supply control unit 74. Each functional configuration is realized by the CPU 51 reading a program stored in the ROM 52, loading it into the RAM 53, and executing it.

[0049] The circulating water temperature acquisition unit 71 acquires the temperature of the circulating water in the water circulation path 14, which is detected by the temperature sensor 30.

[0050] The pump control unit 72 controls the operation of the pump 22. By driving the pump 22, water is circulated through the water circulation path 14.

[0051] The current density acquisition unit 73 acquires the electrolytic current density converted based on the current detection value of the water electrolytic cell stack 12 detected by the current detection unit 62.

[0052] The power supply control unit 74 controls the operation of the power supply unit 16. Based on the temperature detected by the temperature sensor 30, the power supply control unit 74 controls the current (e.g., DC current) of the power supply unit 16. More specifically, by controlling the current of the power supply unit 16, the power supply control unit 74 increases or decreases the waste heat from water electrolysis in the water electrolysis cell stack 12, thereby controlling the temperature of the water circulating in the water circulation path 14.

[0053] For example, the power supply control unit 74 increases the current of the power supply unit 16 when the temperature detected by the temperature sensor 30 falls below a first threshold. More specifically, by increasing the current of the power supply unit 16, the power supply control unit 74 increases the waste heat from water electrolysis in the water electrolysis cell stack 12, thereby raising the temperature of the water circulating in the water circulation path 14. For example, the first threshold is a temperature set according to the temperature difference from a reference temperature (e.g., 80°C). If the absolute value of the temperature difference from the reference temperature (e.g., 80°C) is to be kept within a predetermined range (e.g., within 10°C), the first threshold is, for example, 70°C. When the temperature detected by the temperature sensor 30 falls below a first threshold (e.g., 70°C), the current of the power supply unit 16 is increased.

[0054] As an example, the power supply control unit 74 reduces the current of the power supply 16 if the temperature detected by the temperature sensor 30 rises above the second threshold. More specifically, by reducing the current of the power supply 16, the power supply control unit 74 reduces the waste heat from water electrolysis in the water electrolysis cell stack 12 and lowers the temperature of the water circulating in the water circulation path 14. As an example, the second threshold is a temperature set according to the temperature difference from a reference temperature (e.g., 80°C). If the absolute value of the temperature difference from the reference temperature (e.g., 80°C) is to be kept within a predetermined range (e.g., within 10°C), the second threshold will be, for example, 90°C. If the temperature detected by the temperature sensor 30 rises above the second threshold (e.g., 90°C), the current of the power supply 16 is reduced.

[0055] Furthermore, the power supply control unit 74 controls the current supplied to the water electrolysis cell stack 12 by the power supply unit 16, for example, based on the cell voltage detected by the voltage detection unit 64, so as not to exceed a predetermined voltage upper limit.

[0056] (Example of operation of water electrolysis system 10) Next, an example of the operation of the water electrolysis system 10 will be described.

[0057] Figure 4 is a graph showing the relationship between elapsed time in the water electrolysis system 10, circulating water temperature, electrolysis current density, and hydrogen flow rate.

[0058] In the water electrolysis system 10, the pump 22 is driven to circulate water in the water circulation path 14. Furthermore, by supplying current from the power supply unit 16 to the water electrolysis cell stack 12, the water electrolysis cell stack 12 is operated to generate hydrogen and oxygen through water electrolysis (i.e., electrolysis of water). The operation of the power supply unit 16 is controlled by the CPU 51 of the control device 50. The CPU 51 obtains the water temperature in the water circulation path 14 detected by the temperature sensor 30. As shown in Figure 4, when the operation of the water electrolysis cell stack 12 is stable, the water temperature in the water circulation path 14 detected by the temperature sensor 30 is approximately 80°C, which is near the reference temperature.

[0059] As shown in Figure 4, the CPU 51 increases the current of the power supply 16 when the temperature detected by the temperature sensor 30 falls below a first threshold (for example, 70°C). For example, it increases the DC current of the power supply 16 to an acceptable value. That is, by increasing the current of the power supply 16, the CPU 51 increases the heat dissipated from water electrolysis in the water electrolysis cell stack 12, thereby raising the temperature of the water circulating in the water circulation path 14.

[0060] As shown in Figure 4, as the current value of the power supply 16 increases, the electrolysis current density of the water electrolysis cell stack 12 increases, and the hydrogen flow rate delivered from the water electrolysis cell stack 12 to the hydrogen delivery path 38 increases. In addition, increasing the current of the power supply 16 also increases the voltage, and the temperature of the water electrolysis cell stack 12 rises due to the increased overvoltage from the electrolysis thermal neutral point voltage. As a result, the heat dissipated from the water electrolysis cell stack 12 increases, and the temperature of the water in the water circulation path 14 (i.e., circulating water) gradually rises. Then, when the temperature detected by the temperature sensor 30 reaches the reference temperature (for example, 80°C), the CPU 51 returns the current value of the power supply 16 to its original value. As a result, the temperature of the water circulating in the water circulation path 14 stabilizes at approximately 80°C, near the reference temperature.

[0061] As shown in Figure 4, the CPU 51 reduces the current of the power supply 16 when the temperature detected by the temperature sensor 30 rises above a second threshold (for example, 90°C). In other words, by reducing the current of the power supply 16, the heat generated from water electrolysis in the water electrolysis cell stack 12 is reduced, and the temperature of the water circulating in the water circulation path 14 is lowered.

[0062] As shown in Figure 4, as the current value of the power supply 16 decreases, the electrolysis current density of the water electrolysis cell stack 12 decreases, and the hydrogen flow rate delivered from the water electrolysis cell stack 12 to the hydrogen delivery path 38 decreases. Also, when the current of the power supply 16 is reduced, the voltage also decreases, approaching or falling below the voltage of the electrolysis thermal neutral point, so the temperature of the water electrolysis cell stack 12 decreases. As a result, the heat dissipated from the water electrolysis cell stack 12 decreases, and the temperature of the water in the water circulation path 14 (i.e., circulating water) gradually decreases. Then, when the temperature detected by the temperature sensor 30 reaches the reference temperature (for example, 80°C), the CPU 51 returns the current value of the power supply 16 to its original value. As a result, the temperature of the water circulating in the water circulation path 14 stabilizes at approximately 80°C, near the reference temperature.

[0063] <Mechanism and Effects> Next, the operation and effects of the first embodiment will be described.

[0064] In the water electrolysis system 10, a pump 22 installed in the water circulation path 14 is driven to circulate water discharged from the water electrolysis cell stack 12 through the water circulation path 14 and supply it to the water electrolysis cell stack 12. The power supply device 16 supplies current to the water electrolysis cell stack 12, causing the water electrolysis cell stack 12 to generate hydrogen and oxygen through water electrolysis (i.e., electrolysis of water).

[0065] A temperature sensor 30 is installed in the middle of the water circulation path 14, and the temperature of the water flowing through the water circulation path 14 is detected by the temperature sensor 30. Based on the temperature detected by the temperature sensor 30, the control device 50 controls the current of the power supply unit 16 to increase or decrease the waste heat from water electrolysis in the water electrolysis cell stack 12. This controls the temperature of the water circulating in the water circulation path 14. As a result, there is no need to install a heater to raise the temperature of the water circulating in the water circulation path 14 or a chiller to lower the temperature of the water, and the power consumption required to operate the heater or chiller can be reduced. Therefore, the water electrolysis system 10 can reduce costs compared to a system that is operated with a heater or chiller.

[0066] Furthermore, in the water electrolysis system 10, when the temperature detected by the temperature sensor 30 falls below a first threshold, the control device 50 increases the current of the power supply unit 16, thereby increasing the waste heat from water electrolysis in the water electrolysis cell stack 12 and raising the temperature of the water circulating in the water circulation path 14. As a result, the water electrolysis system 10 does not require the installation of heaters or other devices to raise the water temperature in the water circulation path 14, and power consumption can be reduced more reliably.

[0067] Furthermore, in the water electrolysis system 10, if the temperature detected by the temperature sensor 30 rises above a second threshold, the control device 50 reduces the current of the power supply unit 16, thereby reducing the waste heat from water electrolysis in the water electrolysis cell stack 12 and lowering the temperature of the water circulating in the water circulation path 14. As a result, the water electrolysis system 10 does not require the installation of chillers or other devices to lower the water temperature in the water circulation path 14, and power consumption can be reduced more reliably.

[0068] Furthermore, in the water electrolysis system 10, a gas-liquid separator 20 and a water inlet 24 are provided in the water circulation path 14, downstream of the water electrolysis cell stack 12 in the direction of water flow in the water circulation path 14 and upstream of the temperature sensor 30. 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. In addition, new water is introduced into the water circulation path 14 by the water inlet 24. As a result, the water discharged from the water electrolysis cell stack 12 is circulated in the water circulation path 14, and water can be supplied to the water electrolysis cell stack 12 with new water introduced in between. Moreover, since the gas-liquid separator 20 and the water inlet 24 are provided downstream of the water electrolysis cell stack 12 in the direction of water flow in the water circulation path 14 and upstream of the temperature sensor 30, the temperature of the water supplied to the water electrolysis cell stack 12 can be controlled more reliably.

[0069] Furthermore, in the water electrolysis system 10, a predetermined voltage limit is provided for the power supply unit 16. Therefore, in the water electrolysis system 10, when water electrolysis is performed in the water electrolysis cell stack 12 by controlling the current, the deterioration of the catalyst in the water electrolysis cell stack 12 can be suppressed.

[0070] Here, we will describe the comparative example water electrolysis system 500. Figure 9 is a schematic diagram showing the comparative example water electrolysis system 500.

[0071] As shown in Figure 9, the comparative example water electrolysis system 500 is equipped with a heat exchanger 510 and a heater 520 in the middle of the water circulation path 14.

[0072] The heat exchanger 510 is equipped with a heat transfer medium circulation path 514 that circulates a heat transfer medium such as oil between it and the chiller 512. The chiller 512 cools the water in the water circulation path 14 by circulating the heat transfer medium through the heat transfer medium circulation path 514 while controlling the liquid temperature of the heat transfer medium. The heat exchanger 510 is located downstream of the pump 22 and upstream of the ion exchange resin 36 in the direction of water transfer in the water circulation path 14.

[0073] The heater 520 raises the temperature of the water in the water circulation path 14. The heater 520 is located downstream of the ion exchange resin 36 in the water transfer direction of the water circulation path 14, and upstream of the water electrolysis cell stack 12 and the temperature sensor 30.

[0074] Figure 10 is a graph showing the relationship between elapsed time, circulating water temperature, electrolysis current density, ON or OFF state of heater 520, ON or OFF state of chiller 512, and hydrogen flow rate in the comparative example water electrolysis system 500.

[0075] As shown in Figure 10, in the comparative example water electrolysis system 500, the electrolysis current density of the water electrolysis cell stack 12 is controlled to be constant at a predetermined value. As a result, the hydrogen flow rate delivered from the water electrolysis cell stack 12 to the hydrogen delivery passage 38 is approximately constant.

[0076] As shown in Figure 10, in the comparative example water electrolysis system 500, when the temperature of the water in the water circulation path 14 (i.e., circulating water) falls below a first threshold (e.g., 70°C) during water electrolysis by the water electrolysis cell stack 12, the heater 520 is turned ON to raise the temperature of the water in the water circulation path 14. As a result, the temperature of the water in the water circulation path 14 gradually rises, and when the temperature of the water in the water circulation path 14 (i.e., circulating water) reaches a reference temperature (e.g., 80°C), the heater 520 is turned OFF. Also, when the temperature of the water in the water circulation path 14 (i.e., circulating water) rises above a second threshold (e.g., 90°C) during water electrolysis by the water electrolysis cell stack 12, the chiller 512 is turned ON to lower the temperature of the water in the water circulation path 14. As a result, the temperature of the water in the water circulation path 14 gradually decreases, and when the temperature of the water in the water circulation path 14 (i.e., circulating water) reaches a reference temperature (e.g., 80°C), the chiller 512 is turned OFF.

[0077] In the comparative example water electrolysis system 500, the installation of a heater 520 and a chiller 512 is required, which increases the system cost. In addition, the heater 520 and chiller 512 control the temperature of the water in the water circulation path 14, which increases power consumption.

[0078] In contrast, the water electrolysis system 10 of the first embodiment does not require the installation of a heater and chiller. Furthermore, in the water electrolysis system 10, the control device 50 controls the current of the power supply unit 16 based on the temperature detected by the temperature sensor 30, thereby increasing or decreasing the waste heat from water electrolysis in the water electrolysis cell stack 12 and controlling the temperature of the water circulating in the water circulation path 14. As a result, the water electrolysis system 10 can reduce power consumption compared to the case where the temperature of the water in the water circulation path 14 is controlled by a heater and chiller. Consequently, the water electrolysis system 10 can reduce costs compared to the case where a heater or chiller is installed and operated.

[0079] [Second Embodiment] Next, the water electrolysis system of the second embodiment will be described. Note that components identical to those of the first embodiment described above will be given the same numbers and their descriptions will be omitted.

[0080] <Configuration of the water electrolysis system> Figure 5 is a schematic diagram showing the water electrolysis system 100 of the second embodiment. As shown in Figure 5, the water electrolysis system 100 has a different configuration from the water electrolysis system 10 of the first embodiment, and includes a water supply channel 102 for supplying water to the water electrolysis cell stack 12 and a control device 150. A gas-liquid separator 20 and a water introduction section 24 are provided on the upstream side of the water flow direction of the water supply channel 102.

[0081] The water supply channel 102 is equipped 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 102, and water is then supplied to the water electrolysis cell stack 12 through the water supply channel 102. For example, the pump 22 is located downstream of the gas-liquid separator 20 in the direction of water flow in the water supply channel 102, and upstream of the ion exchange resin 36. The ion exchange resin 36 is located downstream of the pump 22 in the direction of water flow in the water supply channel 102, and upstream of the water electrolysis cell stack 12.

[0082] The water electrolysis cell stack 12 is equipped with a temperature sensor 104 for measuring the temperature of the water inside. Specifically, the temperature sensor 104 detects the temperature of the water used for the reaction in the water electrolysis cell stack 12. Furthermore, the water electrolysis cell stack 12 is equipped with a hydrogen outlet passage 38 for supplying hydrogen and an oxygen outlet passage 106 for supplying oxygen.

[0083] Furthermore, the water electrolysis system 100 includes a power supply unit 16 that supplies current to the water electrolysis cell stack 12.

[0084] The control device 150 controls each part of the water electrolysis system 100.

[0085] Figure 6 is a block diagram showing the hardware configuration of the water electrolysis system 100.

[0086] As shown in Figure 6, the water electrolysis system 100 includes a control device 150. The control device 150 has a CPU 51, ROM 52, RAM 53, storage 54, and an input / output interface 55. Each component is connected to the others so as to be able to communicate with each other via a bus 59.

[0087] The input / output interface 55 is electrically connected to the power supply unit 16, the pump 22, the temperature sensor 104, the current detection unit 62, the voltage detection unit 64, and the hydrogen flow meter 66. Through this, the CPU 51 controls the operation of the power supply unit 16 and the pump 22 via the input / output interface 55. The CPU 51 also receives detection values ​​from the temperature sensor 104, the current detection unit 62, the voltage detection unit 64, and the hydrogen flow meter 66, respectively, via the input / output interface 55.

[0088] Figure 7 is a block diagram showing an example of the functional configuration of the control device 150 in the water electrolysis system 100.

[0089] As shown in Figure 7, the control device 150 in the water electrolysis system 100 has a functional configuration consisting of a stack temperature acquisition unit 151, a pump control unit 72, a current density acquisition unit 73, and a power supply control unit 152. Each functional configuration is realized by the CPU 51 reading a program stored in the ROM 52, loading it into the RAM 53, and executing it.

[0090] The stack temperature acquisition unit 151 acquires the temperature of the water inside the water electrolysis cell stack 12 detected by the temperature sensor 104 (i.e., the temperature of the water used for the reaction in the water electrolysis cell stack 12).

[0091] The power supply control unit 152 controls the operation of the power supply unit 16. Based on the temperature detected by the temperature sensor 104, the power supply control unit 152 controls the current (e.g., DC current) of the power supply unit 16. More specifically, by controlling the current of the power supply unit 16, the power supply control unit 152 increases or decreases the waste heat from water electrolysis in the water electrolysis cell stack 12, thereby controlling the temperature of the water used for the reaction in the water electrolysis cell stack.

[0092] For example, if the temperature detected by the temperature sensor 104 falls below a first threshold, the power supply control unit 152 increases the current of the power supply unit 16, thereby increasing the heat dissipated from water electrolysis in the water electrolysis cell stack 12 and raising the temperature of the water used for the reaction in the water electrolysis cell stack 12. For example, the first threshold is a temperature set according to the temperature difference from a reference temperature (e.g., 80°C). If the absolute value of the temperature difference from the reference temperature (e.g., 80°C) is to be kept within a predetermined range (e.g., within 10°C), the first threshold is, for example, 70°C. If the temperature detected by the temperature sensor 104 falls below the first threshold (e.g., 70°C), the current of the power supply unit 16 is increased.

[0093] For example, if the temperature detected by the temperature sensor 104 rises above the second threshold, the power supply control unit 152 reduces the current of the power supply unit 16, thereby reducing the heat waste from water electrolysis in the water electrolysis cell stack 12 and lowering the temperature of the water used for the reaction in the water electrolysis cell stack 12. For example, the second threshold is a temperature set according to the temperature difference from a reference temperature (e.g., 80°C). If the absolute value of the temperature difference from the reference temperature (e.g., 80°C) is to be kept within a predetermined range (e.g., within 10°C), the second threshold will be, for example, 90°C. If the temperature detected by the temperature sensor 104 rises above the second threshold (e.g., 90°C), the current of the power supply unit 16 is reduced. The other configurations of the water electrolysis system 100 are the same as those of the water electrolysis system 10 of the first embodiment.

[0094] Next, an example of the operation of the water electrolysis system 100 will be described.

[0095] Figure 8 is a graph showing the relationship between elapsed time in the water electrolysis system 100, stack temperature, electrolysis current density, and hydrogen flow rate. The stack temperature is the temperature of the water inside the water electrolysis cell stack 12, as detected by the temperature sensor 104.

[0096] In the water electrolysis system 100, the pump 22 is driven to supply water from the water supply path 102 to the water electrolysis cell stack 12. Furthermore, by supplying current from the power supply unit 16 to the water electrolysis cell stack 12, the water electrolysis cell stack 12 is operated to produce hydrogen and oxygen through water electrolysis (i.e., electrolysis of water). The operation of the power supply unit 16 is controlled by the CPU 51 of the control device 150. The CPU 51 acquires the stack temperature detected by the temperature sensor 104. As shown in Figure 8, when the operation of the water electrolysis cell stack 12 is stable, the stack temperature detected by the temperature sensor 104 is approximately 80°C, near the reference temperature.

[0097] As shown in Figure 8, the CPU 51 increases the current of the power supply 16 when the temperature detected by the temperature sensor 104 falls below a first threshold (for example, 70°C). For example, it increases the DC current of the power supply 16 to an acceptable value. That is, by increasing the current of the power supply 16, the heat dissipated from water electrolysis in the water electrolysis cell stack 12 is increased, and the temperature of the water used for the reaction in the water electrolysis cell stack 12 is raised.

[0098] As shown in Figure 8, as the current value of the power supply 16 increases, the electrolysis current density of the water electrolysis cell stack 12 increases, and the hydrogen flow rate delivered from the water electrolysis cell stack 12 to the hydrogen delivery path 38 increases. In addition, increasing the current of the power supply 16 also increases the voltage, and the temperature of the water electrolysis cell stack 12 rises due to the increased overvoltage from the electrolysis thermal neutral point voltage. As a result, the heat dissipated from the water electrolysis cell stack 12 increases, and the stack temperature gradually rises. Then, when the temperature detected by the temperature sensor 104 reaches the reference temperature (for example, 80°C), the CPU 51 returns the current value of the power supply 16 to its original value. As a result, the stack temperature stabilizes at approximately 80°C, near the reference temperature.

[0099] As shown in Figure 8, the CPU 51 reduces the current of the power supply 16 when the temperature detected by the temperature sensor 104 rises above a second threshold (for example, 90°C). In other words, by reducing the current of the power supply 16, the heat generated from water electrolysis in the water electrolysis cell stack 12 is reduced, and the temperature of the water used for the reaction in the water electrolysis cell stack 12 is lowered.

[0100] As shown in Figure 8, as the current value of the power supply 16 decreases, the electrolysis current density of the water electrolysis cell stack 12 decreases, and the hydrogen flow rate delivered from the water electrolysis cell stack 12 to the hydrogen delivery passage 38 decreases. Also, when the current of the power supply 16 is reduced, the voltage also decreases, approaching or falling below the voltage of the electrolysis thermal neutral point, so the temperature of the water electrolysis cell stack 12 decreases. As a result, the heat dissipated from the water electrolysis cell stack 12 decreases, and the stack temperature gradually decreases. Then, when the temperature detected by the temperature sensor 104 reaches the reference temperature (for example, 80°C), the CPU 51 returns the current value of the power supply 16 to its original value. As a result, the stack temperature stabilizes at approximately 80°C, near the reference temperature.

[0101] <Mechanism and Effects> Next, the operation and effects of the second embodiment will be described.

[0102] In the water electrolysis system 100, water is supplied to the water electrolysis cell stack 12 by driving a pump 22 located in the water supply path 102. The power supply unit 16 supplies current to the water electrolysis cell stack 12, causing hydrogen and oxygen to be generated by water electrolysis in the water electrolysis cell stack 12. A temperature sensor 104 detects the temperature of the water to be reacted in the water electrolysis cell stack 12. The control device 150 controls the current of the power supply unit 16 based on the temperature detected by the temperature sensor 104, thereby increasing or decreasing the waste heat generated by water electrolysis in the water electrolysis cell stack 12. This controls the temperature of the water to be reacted in the water electrolysis cell stack 12. As a result, the water electrolysis system 100 does not require a heater to raise the water temperature in the water supply path 102, and the power consumption required to operate the heater can be reduced. Therefore, the water electrolysis system 100 can reduce costs compared to a system that uses a heater.

[0103] Furthermore, in the water electrolysis system 100, if the temperature detected by the temperature sensor 104 falls below a first threshold, the control device 150 increases the current of the power supply unit 16, thereby increasing the waste heat from water electrolysis in the water electrolysis cell stack 12 and raising the temperature of the water used for the reaction in the water electrolysis cell stack 12. As a result, the water electrolysis system 100 does not require the installation of heaters or other devices to raise the water temperature in the water supply path 102, and power consumption can be reduced more reliably.

[0104] Furthermore, in the water electrolysis system 100, if the temperature detected by the temperature sensor 104 rises above a second threshold, the control device 150 reduces the current of the power supply unit 16, thereby reducing the waste heat from water electrolysis in the water electrolysis cell stack 12 and lowering the temperature of the water used for the reaction in the water electrolysis cell stack 12. As a result, the water electrolysis system 100 does not require the installation of a chiller or other device to lower the water temperature in the water supply path 102, and power consumption can be reduced more reliably.

[0105] Furthermore, the water electrolysis system 100 can achieve the same operation and effects as the water electrolysis system 10 of the first embodiment by having the same configuration.

[0106] Furthermore, the water electrolysis system 100 may be configured such that excess water in the water electrolysis cell stack 12 is circulated and returned to the water electrolysis cell stack 12.

[0107] 〔supplementary explanation〕 In the water electrolysis systems 10 and 100 of the first and second embodiments, the configuration of each part may be changed or other equipment may be added without departing from the gist of the present disclosure.

[0108] Although embodiments of this disclosure have been described with reference to specific examples, these embodiments are merely examples and can be modified in various ways without departing from the spirit of the disclosure. Furthermore, it goes without saying that the scope of rights of this disclosure is not limited to these embodiments and can be implemented in various ways without departing from the spirit of the disclosure. [Explanation of symbols]

[0109] 10...Water electrolysis system, 12...Water electrolysis cell stack, 14...Water circulation path, 16...Power supply unit, 20...Gas-liquid separator (water separator), 22...Pump, 24...Water inlet, 30...Temperature sensor, 50...Control device, 100...Water electrolysis system, 102...Water supply path, 104...Temperature sensor, 150...Control device

Claims

1. A water electrolysis cell stack that generates hydrogen and oxygen through water electrolysis, A pump is provided, and a water supply path is provided to supply water to the water electrolysis cell stack, A power supply device that supplies current to the aforementioned water electrolysis cell stack, A temperature sensor for detecting the temperature of the water to be reacted in the water electrolysis cell stack, A control device controls the current of the power supply device based on the temperature detected by the temperature sensor, thereby increasing or decreasing the waste heat from water electrolysis in the water electrolysis cell stack and controlling the temperature of the water to be reacted in the water electrolysis cell stack. A water electrolysis system having the following features.

2. The water supply path consists of a water circulation path that circulates the water discharged from the water electrolysis cell stack and supplies it to the water electrolysis cell stack. The temperature sensor is installed in the middle of the water circulation path and detects the temperature of the water flowing through the water circulation path. The water electrolysis system according to claim 1, wherein the control device controls the current of the power supply based on the temperature detected by the temperature sensor, thereby increasing or decreasing the waste heat from water electrolysis in the water electrolysis cell stack and controlling the temperature of the water circulating in the water circulation path.

3. The water electrolysis system according to claim 1, wherein the control device increases the current of the power supply and increases the waste heat from water electrolysis in the water electrolysis cell stack when the temperature detected by the temperature sensor falls below a first threshold, thereby increasing the temperature of the water to be reacted in the water electrolysis cell stack.

4. The water electrolysis system according to claim 1, wherein the control device, when the temperature detected by the temperature sensor rises to a second threshold, reduces the current of the power supply and decreases the waste heat from water electrolysis in the water electrolysis cell stack, thereby lowering the temperature of the water to be reacted in the water electrolysis cell stack.

5. The water electrolysis system according to claim 2, wherein the control device increases the current of the power supply and increases the waste heat from water electrolysis in the water electrolysis cell stack when the temperature detected by the temperature sensor falls below a first threshold, thereby increasing the temperature of the water circulating in the water circulation path.

6. The water electrolysis system according to claim 2, wherein the control device, when the temperature detected by the temperature sensor rises to a second threshold, reduces the current of the power supply and decreases the waste heat from water electrolysis in the water electrolysis cell stack, thereby lowering the temperature of the water circulating in the water circulation path.

7. The water electrolysis system according to claim 2, wherein the water circulation path is provided with a water separator for separating water discharged from the water electrolysis cell stack from gas and a water introduction section for introducing new water, located downstream of the water electrolysis cell stack and upstream of the temperature sensor in the water flow direction of the water circulation path.

8. The water electrolysis system according to claim 1, wherein the power supply device is provided with a predetermined voltage upper limit.

Images