WO2023166861A1

WO2023166861A1 - Water electrolysis device and control method

Info

Publication number: WO2023166861A1
Application number: PCT/JP2023/000784
Authority: WO
Inventors: 祥太小川; 昌宏八巻
Original assignee: 日立造船株式会社
Priority date: 2022-03-03
Filing date: 2023-01-13
Publication date: 2023-09-07
Also published as: JP2023128433A; TW202340536A

Abstract

This water electrolysis device comprises: a water electrolysis tank (20) in which a plurality of electrolysis cells (10) each including a solid polymer electrolyte membrane (4) are connected in series; and a plurality of short circuits (60) connected to each of the plurality of electrolysis cells (10) and which short the electrolysis cells (10) upon stoppage of power supply to the water electrolysis tank (20).

Description

Water electrolysis device and control method

The present invention relates to a solid polymer type water electrolysis device that electrolyzes water to generate hydrogen and oxygen, and a control method thereof.

Conventionally, technologies for producing hydrogen using natural energy as primary energy have been developed, and one of them is known as a solid polymer type water electrolysis device. In a solid polymer type water electrolysis device, pure water is electrolyzed by applying a voltage to a solid polymer electrolyte membrane and causing an electric current to flow _. Oxygen (O ₂ ) is generated.

Further, regarding this type of water electrolysis device, Patent Documents 1 and 2 disclose a solid polymer type water electrolysis cell (a water electrolysis cell stack) in which a plurality of electrolysis cells including a solid polymer electrolyte membrane are stacked in series. A water electrolyzer is disclosed.

Japanese Patent Application Laid-Open No. 2015-48507 Japanese Patent Application Laid-Open No. 2021-46602

Here, in the solid polymer type water electrolysis device, oxygen remaining in the electrolysis cell reacts with hydrogen during the electrolysis stop period, and hydrogen peroxide (H ₂ O ₂ ) can be generated. The hydrogen peroxide decomposes the solid polymer electrolyte membrane, possibly degrading the electrolytic cell.

An object of one aspect of the present invention is to suppress the generation of hydrogen peroxide during the period when electrolysis is stopped, and to reduce deterioration of the electrolytic cell.

In order to solve the above problems, a water electrolysis apparatus according to an aspect of the present invention includes a water electrolysis tank in which a plurality of electrolytic cells each including a solid polymer electrolyte membrane are connected in series; a plurality of short circuits connected to each of one or more electrolysis cell units selected from the electrolysis cells and short-circuiting the electrolysis cell units when power supply to the water electrolyzer is stopped; Prepare.

In order to solve the above-described problems, a method for controlling a water electrolysis device according to an aspect of the present invention includes the steps of supplying power to a water electrolysis tank in which a plurality of electrolysis cells each including a solid polymer electrolyte membrane are connected in series; When power supply to the water electrolyzer is stopped, a plurality of short circuits are closed for each unit of one or more of the electrolyzed cells selected from the plurality of electrolyzed cells included in the water electrolyzer. and short-circuiting the electrolysis cell units.

According to one aspect of the present invention, it is possible to suppress generation of hydrogen peroxide during the electrolysis stop period and reduce deterioration of the electrolytic cell.

1 is a block diagram showing a schematic configuration of a water electrolysis device according to one embodiment of the present invention; FIG. FIG. 2 is a cross-sectional view showing the configuration of the water electrolytic bath shown in FIG. 1; FIG. 2 is a block diagram showing a schematic configuration of a water electrolytic bath, a rectifier and a short circuit shown in FIG. 1; It is a schematic diagram which shows schematic structure of the said short circuit. 4 is a flowchart showing an example of stop control executed by the water electrolysis device; 4 is a graph showing the change over time of the residual voltage of each electrolysis cell during the electrolysis stop period. 4 is a flowchart showing an example of determination control executed by the water electrolysis device; FIG. 5 is a schematic diagram showing a modification of the short circuit shown in FIG. 4; 4 is a graph showing measurement results of comparative tests in Examples.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 8. FIG. However, the following description is an example of the water electrolysis apparatus according to the present invention, and the technical scope of the present invention is not limited to the illustrated examples.

[Configuration of water electrolysis device 100]
First, the configuration of a water electrolysis device 100 according to one embodiment of the present invention will be described based on FIGS. 1 and 2. FIG. FIG. 1 is a block diagram showing a schematic configuration of a water electrolysis device 100 according to this embodiment. FIG. 2 is a cross-sectional view showing the structure of the water electrolytic bath 20 shown in FIG. The water electrolysis device 100 according to the present embodiment electrolyzes pure water by applying a voltage to the solid polymer electrolyte membrane 4 and causing an electric current to flow to generate hydrogen (H ₂ ) and oxygen (O ₂ ). This is a solid polymer type water electrolysis device.

As shown in FIG. 1, the water electrolysis device 100 includes a water electrolyzer 20, a hydrogen gas-liquid separator 21, an oxygen gas-liquid separator 22, a water circulation line 23, a first ion exchanger 24, pure water It includes a tank 25 , a branch line 41 and a second ion exchanger 43 . The water electrolysis device 100 also includes a rectifier (power supply unit) 50 and a short circuit 60 connected to the water electrolysis tank 20, and a control unit (determining unit) 70 that controls the operation of the water electrolysis device 100 as a whole.

The water circulation line 23 is a line for circulating water from the hydrogen gas-liquid separator 21 and the oxygen gas-liquid separator 22 to the water electrolytic bath 20 . A circulation pump 27 for circulating water and a circulating water cooler 28 for cooling the circulating water before supplying it to the water electrolyzer 20 are arranged in the water circulation line 23 . A hydrogen cooler 31 is arranged at the outlet of the hydrogen gas-liquid separator 21 , and an oxygen cooler 32 is arranged at the outlet of the oxygen gas-liquid separator 22 .

The branch line 41 is a line that takes out a part of the circulating water of the water circulation line 23 and treats it, and sends the treated water to the pure water tank 25 . The branch line 41 is provided with a blow water cooler 42 that cools the circulating water taken out from the water circulation line 23 and a second ion exchanger 43 that ion-exchanges the cooled water. The branch line 41 is connected to the pure water tank 25 at its downstream end. The upstream end of the branch line 41 is connected between the circulation pump 27 and the circulation water cooler 28 of the water circulation line 23 . A blow valve (flow control valve) 29 is arranged upstream of the branch line 41 . The opening and closing of the blow valve 29 is automatically controlled by the electric conductivity of the circulating water obtained from the electric conductivity controller 30 arranged between the circulation pump 27 of the water circulation line 23 and the circulating water cooler 28 .

The water electrolytic bath 20 electrolyzes water using a polymer electrolyte membrane to generate oxygen at the anode and hydrogen at the cathode. As shown in FIG. 2, the water electrolyzer 20 is a water electrolysis cell stack in which a plurality of electrolysis cells 10 are connected in series. The water electrolytic bath 20 has an anode main electrode (electrode) 1 and a cathode main electrode (electrode) 2 arranged at both ends thereof, and a plurality of electrodes arranged in series between the anode main electrode 1 and the cathode main electrode 2. It is mainly composed of an electrolytic cell 10 and four tightening bolts and nuts that integrate the plural electrolytic cells 10 . In addition, in the illustrated example, the electrolysis cells 10 are arranged in the horizontal direction and connected, but the electrolysis cells 10 may be arranged in the vertical direction and connected.

One electrolysis cell 10 includes a titanium alloy bipolar plate 9 on the anode side, a porous anode feeder 7, a solid polymer electrolyte membrane 4, and

catalyst electrode layers

5 and 6 provided on both sides thereof. It is composed of MEA (Membrane Electrode Assemblies) 3 including a membrane electrode assembly, a porous cathode feeder 8 and the cathode side of the adjacent bipolar plate 9 .

Each electrolysis cell 10 arranged at both ends of the water electrolyzer 20 includes an anode main electrode 1 or a cathode main electrode 2 in place of one of the two bipolar plates 9 . That is, the electrolytic cell 10 arranged at the end of the water electrolytic bath 20 on the anode side is composed of the anode main electrode 1, the anode feeder 7, the MEA 3, the cathode feeder 8, and the cathode side of the bipolar plate 9. Configured. Further, the electrolysis cell 10 arranged at the cathode-side end of the water electrolyzer 20 is composed of the anode side of the bipolar plate 9, the anode feeder 7, the MEA 3, the cathode feeder 8, and the cathode main electrode 2. Configured.

In the water electrolyzer 20 , water supplied from the water supply header 11 arranged at the bottom of the water electrolyzer 20 passes through the anode power feeder 7 and reaches the anode-side catalytic electrode layer 5 of the MEA 3 . Electric power applied to the anode-side catalytic electrode layer 5 causes an electrolysis reaction of water to generate oxygen. The generated oxygen passes through the anode feeder 7, rises together with unreacted water in the vertical flow path provided on the anode side of the bipolar plate 9, and reaches the oxygen header 12 arranged in the upper part of the water electrolyzer 20. Ejected. On the other hand, hydrogen generated on the surface of the cathode-side catalyst electrode layer 6 of the MEA 3 and water that has permeated the solid polymer electrolyte membrane 4 pass through the cathode feeder 8 and flow through the vertical flow path provided on the cathode side of the bipolar plate 9. It rises inside and is discharged to the hydrogen header 13 arranged in the upper part of the water electrolyzer 20 .

The water electrolyzer 20 is supplied with electric power (direct current) required for water electrolysis from a rectifier 50 . The rectifier 50 is connected to the anode main electrode 1 and the cathode main electrode 2 of the water electrolytic bath 20 and supplies power to the water electrolytic bath 20 . As electric power to be supplied to the water electrolyzer 20, in addition to electric power from a commercial power supply, renewable energy such as solar power generation and wind power generation, or surplus power thereof, or the like can be used.

Here, with renewable energy or its surplus power, etc., the amount of power generated fluctuates greatly due to the effects of weather and other factors. When such unstable power is used, it is necessary to stop the electrolysis operation of the water electrolyzer 20 during the period when the power required for the operation of the water electrolyzer 100 cannot be obtained. Oxygen and hydrogen remaining in the electrolysis cell 10 may react with each other during this stop period of electrolysis to generate hydrogen peroxide. The hydrogen peroxide decomposes the solid polymer electrolyte membrane 4 , possibly degrading the electrolytic cell 10 .

Therefore, in the water electrolysis device 100, the short circuit 60 is connected to each electrolysis cell 10. The short circuit 60 short-circuits each electrolysis cell 10 during the electrolysis stop period of the water electrolyzer 20 . In other words, the short circuit 60 short-circuits the mutually adjacent electrodes (anode main electrode 1, cathode main electrode 2, bipolar plate 9) of the electrolytic cell 10 during the electrolysis stop period of the water electrolytic bath 20. FIG. Thus, by closing the short circuit 60 and short-circuiting the electrolysis cell 10 during the electrolysis stop period, the oxygen and hydrogen remaining in the electrolysis cell 10 can be consumed using the fuel cell reaction. can. Therefore, generation of hydrogen peroxide within the electrolytic cell 10 is suppressed, and as a result, the solid polymer electrolyte membrane 4 is less likely to be decomposed. Therefore, it is possible to suppress the generation of hydrogen peroxide during the stop period of electrolysis and reduce the deterioration of the electrolytic cell 10 . Details of the short circuit 60 will be described later.

The hydrogen gas-liquid separator 21 separates the hydrogen generated at the cathode of the water electrolyzer 20 and water. In addition, the oxygen-gas-liquid separator 22 separates oxygen and water generated at the anode of the water electrolytic bath 20 . In FIG. 1, oxygen generated at the anode of water electrolyzer 20 is sent to oxygen gas-liquid separator 22 . Also, the hydrogen generated at the cathode of the water electrolyzer 20 is sent to the hydrogen gas-liquid separator 21 . At this time, most of the water discharged from the water electrolytic bath 20 is sent to the oxygen-gas-liquid separator 22 . The hydrogen gas-liquid separator 21 and the oxygen gas-liquid separator 22 are connected by a pipe, and the water surface level of the hydrogen gas-liquid separator 21 and the water surface level of the oxygen gas-liquid separator 22 are controlled to be equal. be done. The water sent to the hydrogen gas-liquid separator 21 and the oxygen gas-liquid separator 22 is re-supplied to the water electrolyzer 20 through the water circulation line 23, and part of it passes through the branch line 41 to the pure water tank 25. sent to

The pure water tank 25 stores water to be electrolyzed in the water electrolytic bath 20. The pure water tank 25 stores water obtained by treating the supply water (city water, etc.) newly supplied to the water electrolyzer 20 by the first ion exchanger 24 . The pure water tank 25 stores water obtained by treating the circulating water extracted from the water circulating line 23 to the branch line 41 with the second ion exchanger 43 . A supply pump 26 for sending the water in the pure water tank 25 to the oxygen-gas-liquid separator 22 is arranged in a pipe connecting the pure-water tank 25 and the oxygen-gas-liquid separator 22 . The water temporarily stored in the pure water tank 25 is sent to the oxygen-gas-liquid separator 22 by the supply pump 26 according to the preset level setting value of the oxygen-gas-liquid separator 22 .

The circulating water flowing through the water circulating line 23 is adjusted to a predetermined temperature (eg, 80° C.) by the circulating water cooler 28 and sent to the water electrolyzer 20 by the circulating pump 27 . The set value of the circulating water for flowing the circulating water to the branch line 41 side is, for example, 1 μS/cm. ing. The circulating water taken out to the branch line 41 is cooled to room temperature by the blow water cooler 42, supplied to the second ion exchanger 43, processed to have an electric conductivity of 0.5 μS/cm or less, and then sent to the pure water tank. 25. In this way, by extracting a part of the circulating water in the water circulating line 23 to the branch line 41 and treating it, the content of impurities in the circulating water can be suppressed.

The control unit 70 comprehensively controls the operation of the water electrolysis device 100 . The control unit 70 is configured by a processor such as a CPU (Central Processing Unit). Alternatively, the control unit 70 is configured by a logic circuit formed in an integrated circuit (IC chip) or the like.

The control unit 70 controls power supply to the water electrolyzer 20 and controls operation of the water electrolyzer 20 . Further, the control unit 70 controls opening and closing of the short circuit 60 based on the state of power supply to the water electrolytic bath 20 . For example, the control unit 70 closes the short circuit 60 when power supply to the water electrolyzer 20 is stopped, thereby short-circuiting each electrolytic cell 10 . Further, the control unit 70 determines the operating state of the short circuit 60 based on the residual voltage of the electrolytic cell 10 after a predetermined time has passed since the start of the short circuit of the electrolytic cell 10 .

[Structure of short circuit 60]
Next, the configuration of the short circuit 60 included in the water electrolysis device 100 will be described with reference to FIGS. 3 and 4. FIG. FIG. 3 is a block diagram showing a schematic configuration of water electrolytic bath 20, rectifier 50 and short circuit 60 shown in FIG. FIG. 4 is a schematic diagram showing a schematic configuration of the short circuit 60 shown in FIG.

As shown in FIG. 3, a plurality of electrolytic cells 10 are connected in series to the water electrolytic bath 20, and a short circuit 60 is connected to each of these electrolytic cells 10. If the water electrolyzer 20 is a cell stack in which, for example, 30 electrolysis cells 10 are connected in series, 30 short circuits 60, which are the same number as the electrolysis cells 10, are arranged, and one short circuit is provided for each electrolysis cell 10. A circuit 60 is connected.

As shown in FIG. 4 , the short circuit 60 is electrically connected to the two bipolar plates 9 that make up each electrolytic cell 10 . The short circuit 60 may be electrically connected to the two bipolar plates 9 using, for example, measurement terminals of a voltmeter V attached to each electrolytic cell 10 .

The resistance value (required resistance value) of the short circuit 60 is adjusted to a range that consumes the residual voltage of the electrolytic cell 10 at the time of short circuit and obtains the effect of shorting the electrolytic cell 10 . The residual voltage of the electrolytic cell 10 at the time of short circuit depends on the configuration of the water electrolytic cell 20, for example, the electrode surfaces 5a and 6a (see FIG. 2) of the catalyst electrode layers 5 and 6 facing each other with the solid polymer electrolyte membrane 4 interposed therebetween. It varies depending on the area, etc. Therefore, the resistance value of the short circuit 60 is preferably 0.002 μΩ/mm ² or more and 0.2 μΩ/mm ² or less per unit area of the electrode surfaces 5a and 6a, and 0.01 μΩ/mm ² or more and 0 0.1 μΩ/mm ² or less is more preferable. By setting the resistance value of the short circuit 60 within this range, the residual voltage of the electrolysis cell 10 at the time of short circuit can be appropriately consumed, and the effect of short circuit can be preferably obtained.

The short circuit 60 includes a relay 61, a fuse 62, and a conductor 63. It should be noted that the short circuit 60 may further include a resistive element in addition to each of these components, if necessary.

A relay (switching unit) 61 is a switch that switches between opening and closing of the short circuit 60 . Switching between the opening and closing of the relay 61 is controlled by the controller 70 . The relay 61 is controlled to open at or immediately before the electrolysis operation of the water electrolyzer 20 is started, in other words, at the time or immediately before the operation of the rectifier 50 is started. For this reason, the short circuit 60 is opened during the electrolysis operation so that the electrolysis cell 10 is not short-circuited. On the other hand, the relay 61 is controlled to be closed while the electrolysis of the water electrolytic bath 20 is stopped. Therefore, the short circuit 60 becomes a closed circuit during the electrolysis stop period, and the electrolysis cell 10 is short-circuited.

In addition, when a semiconductor relay is used as the relay 61, leakage current from the semiconductor relay may occur, and the semiconductor relay may be damaged if a current exceeding the rated value is input. Therefore, it is preferable to use a mechanical relay as the relay 61 .

The fuse (circuit protection unit) 62 opens (breaks) the short circuit 60 when a current (overcurrent) of a predetermined value or more flows through the short circuit 60 for a predetermined time or longer, or when the temperature of the fuse 62 exceeds a predetermined temperature. ) to protect the short circuit 60 . For example, if the opening/closing operation of the relay 61 fails and the relay 61 is closed during the electrolysis operation, an overcurrent of a predetermined value or more flows through the short circuit 60, generating heat and possibly causing a fire or the like. When such an overcurrent flows through the short circuit 60, the fuse element of the fuse 62 blows and the short circuit 60 is opened. Therefore, the short circuit 60 can be protected from overcurrent, and the occurrence of fire or the like can be prevented.

The fuse 62 has a characteristic of being fused by an overcurrent flowing through the short circuit 60 when the relay 61 is closed during the electrolysis operation. For example, as the fuse 62, a fuse having a fusing energy (l ² t) of about 22500 or more, which is the thermal energy passing through the fuse 62 until the fuse element fuses after an overcurrent occurs, can be preferably used.

Also, when a thermal fuse is used as the fuse 62, the fuse element melts and the short circuit 60 is opened when the temperature of the fuse 62 exceeds a specified temperature due to overcurrent. Therefore, by using a thermal fuse as the fuse 62, overcurrent can be safely prevented and the temperature of the short circuit 60 can be controlled. Note that the short circuit 60 may include a circuit protector or the like as a circuit protection section instead of the fuse 62 .

Conductor 63 is a cable made of a conductive material. The conducting wire 63 is, for example, a copper vinyl cable of 3.5 sq or more. The conductor thickness (cross-sectional area) and length of the lead wire 63 are appropriately selected based on the required resistance value of the short circuit 60 required to consume the residual voltage of the electrolysis cell 10 at the time of short circuit. For example, when the conductor of the conducting wire 63 is made of copper, the cross-sectional area of the conducting wire 63 is preferably 0.00006 mm ² /mm ² or more and 0.001 mm ² /mm ² or less per unit area of the electrode surfaces 5a and 6a. It is more preferably 0.00009 mm ² /mm ² or more and 0.0005 mm ² /mm ² or less. By using the conductor wire 63 having a cross-sectional area within this range, the required resistance value of the short circuit 60 required to consume the residual voltage of the electrolytic cell 10 at the time of short circuit can be obtained without using a resistive element. can. In addition, it is possible to suppress the heat generation of the short circuit 60 against the current generated by the fuel cell reaction in the electrolysis cell 10 at the time of short circuit, thereby preventing troubles such as disconnection of the lead wire 63 .

[Control of water electrolysis device 100]
Next, control of the water electrolysis device 100 will be described with reference to FIGS. 5 to 7. FIG. Below, as an example of the control method of the water electrolysis device 100, the stop control for stopping the operation of the water electrolysis device 100 and the determination control for determining the operation state of the short circuit 60 will be described.

(stop control)
First, based on FIG.5 and FIG.6, the stop control (control method) of the water electrolysis apparatus 100 is demonstrated. FIG. 5 is a flowchart showing an example of stop control executed by the water electrolysis device 100. As shown in FIG. The controller 70 controls the rectifier 50 and supplies power to the water electrolyzer 20 during the electrolysis operation period of the water electrolyzer 20 . In addition, the control unit 70 opens the relay 61 and opens the short circuit 60 .

In the stop control of the water electrolysis device 100, the control unit (determination unit) 70 determines whether or not it is necessary to stop the electrolysis operation of the water electrolyzer 20 (S1).

For example, when the amount of hydrogen in a hydrogen tank (not shown) storing hydrogen generated in the water electrolyzer 20 reaches or exceeds a predetermined value, the control unit 70 determines that it is necessary to stop the electrolysis operation (S1 YES), the power supply to the water electrolyzer 20 is stopped to stop the electrolysis operation of the water electrolyzer 20 (S2). Further, for example, when the amount of power generated by renewable energy becomes equal to or less than a predetermined value, the control unit 70 determines that it is necessary to stop the electrolysis operation (YES in S1), and stops the electrolysis operation of the water electrolyzer 20. (S2). Furthermore, for example, when an input of an instruction to stop the electrolysis operation of the water electrolyzer 20 is received from the user, the control unit 70 determines that it is necessary to stop the electrolysis operation (YES in S1). to stop the electrolysis operation of the water electrolyzer 20 (S2).

On the other hand, when it is determined that there is no need to stop the electrolysis operation of the water electrolyzer 20 (NO in S1), the control unit 70 maintains power supply to the water electrolyzer 20 and repeats the determination of step S1. .

Next, the control unit 70 executes control to short-circuit the electrolysis cells 10 when the power supply to the water electrolyzer 20 is stopped (electrolysis is stopped) in step S2 (S3). Specifically, the control unit 70 closes each short circuit 60 by switching the relay 61 of each short circuit 60 from open to closed simultaneously with or immediately after stopping the electrolysis, thereby closing each electrolysis cell 10. short circuit. As a result, the oxygen and hydrogen remaining in the electrolytic cell 10 are consumed using the fuel cell reaction, and the residual voltage of the electrolytic cell 10 is lowered. Therefore, generation of hydrogen peroxide in the electrolytic cell 10 is suppressed, and as a result, the solid polymer electrolyte membrane 4 is less likely to be decomposed.

FIG. 6 is a graph showing the change over time of the residual voltage of each electrolysis cell 10 during the electrolysis stop period. FIG. 6 shows the change over time of the residual voltage of each electrolytic cell 10 in a cell stack (water electrolytic bath 20) in which ten electrolytic cells 10 are stacked vertically. Note that "No. 1 cell" to "No. 10 cell" in the figure indicate that "No. 10 cell" to "No. 1 cell" are stacked in this order from the lower side in the vertical direction. In other words, the electrolytic cell 10 located at the uppermost position in the vertical direction is referred to as "No. 1 cell", and the electrolytic cell 10 positioned at the lowermost position in the vertical direction is referred to as "No. 10 cell".

Since the amount of oxygen and the amount of hydrogen remaining in the electrolysis cell 10 when electrolysis is stopped differs for each electrolysis cell 10, as shown in FIG. .10 cells”. Therefore, for example, when a plurality of electrolysis cells 10 are all short-circuited by one short circuit 60, the residual voltage of each electrolysis cell 10 varies, and the generation of hydrogen peroxide in the electrolysis cell 10 is effectively prevented. I can't hold back.

Therefore, it is preferable to connect one short circuit 60 to each electrolytic cell 10 . As a result, in step S3, each electrolytic cell 10 can be individually short-circuited, and generation of hydrogen peroxide can be effectively suppressed during the electrolysis stop period, and deterioration of the electrolytic cell 10 can be reduced. Moreover, the residual voltage of the water electrolytic bath 20 increases according to the number of the electrolytic cells 10 connected in series. For this reason, for example, there is a risk of electric shock during maintenance of the water electrolyzer 20 during the period when electrolysis is stopped. 20 can be safely maintained.

It should be noted that the control unit 70 starts determination control for determining the operation state of the short circuit 60 when the short circuit control is executed in step S3. Details of the determination control will be described later.

Next, after short-circuiting the electrolysis cell 10 in step S3, the control unit 70 executes control to cool the circulating water (S4). The circulating water is at high temperature and high pressure during electrolysis operation. Therefore, the control unit 70 controls the circulating water cooler 28 to lower the temperature of the circulating water during the electrolysis operation.

Next, after cooling the electrolyzed water in step S4, the control unit 70 executes control to reduce the pressure in the water electrolyzer 20 (S5). The control unit 70 controls, for example, a hydrogen exhaust control valve (not shown) arranged downstream of the hydrogen cooler 31 to exhaust hydrogen into the atmosphere, thereby reducing the pressure in the water electrolyzer 20 .

Finally, after depressurizing the water electrolytic bath 20 in step S5, the control unit 70 executes control to stop the circulation of water (S6). The controller 70 controls, for example, the circulation pump 27 to stop the circulation of the circulating water. As a result, the operation of the water electrolysis device 100 is stopped, and the control unit 70 ends the stop control.

Thus, the stop control executed by the water electrolysis device 100 includes step S3 of closing the short circuit 60 to short-circuit the electrolysis cells 10 when the power supply to the water electrolyzer 20 is stopped. As a result, oxygen and hydrogen remaining in the electrolytic cell 10 can be consumed using the fuel cell reaction. Therefore, generation of hydrogen peroxide within the electrolytic cell 10 is suppressed, and as a result, the solid polymer electrolyte membrane 4 is less likely to be decomposed. Therefore, it is possible to suppress the generation of hydrogen peroxide during the stop period of electrolysis and reduce the deterioration of the electrolytic cell 10 .

(judgment control)
Next, determination control (control method) for determining the operating state of the short circuit 60 will be described with reference to FIG. FIG. 7 is a flowchart showing an example of determination control shown in FIG. For example, if the residual voltage of the electrolytic cell 10 has not decreased to a predetermined value after a predetermined time (first predetermined time) has elapsed since the start of short circuiting of the electrolytic cell 10 (S11), it is possible that some problem has occurred in the short circuit 60. have a nature. Therefore, the control unit 70 performs determination control to determine whether the operating state of the short circuit 60 is normal or abnormal.

In the determination control, the control unit (determination unit) 70 determines whether or not a predetermined time has passed since the short circuit of the electrolytic cell 10 was started in step S3 shown in FIG. 5 (S11). If the predetermined time has not passed since the start of the short circuit of the electrolytic cell 10 (NO in S11), the control unit 70 waits until the predetermined time has passed.

On the other hand, if a predetermined time has passed since the start of the short circuit of the electrolytic cell 10 (YES in S11), the control unit 70 determines whether or not the residual voltage of the electrolytic cell 10 is equal to or higher than a predetermined value (S12). The control unit 70 acquires the residual voltage of each electrolysis cell 10 based on, for example, the output value from the voltmeter V attached to each electrolysis cell 10, and determines whether or not each acquired residual voltage is equal to or higher than a predetermined value. If at least one of the residual voltages of the electrolysis cells 10 is equal to or higher than the predetermined value (YES in S12), there is a possibility that the water electrolysis device 100 is malfunctioning.

Therefore, when the residual voltage of the electrolysis cell 10 is equal to or higher than a predetermined value, the control unit 70 warns the user that there is a possibility that the water electrolysis device 100 is abnormal (S13). Although the warning method is not particularly limited, for example, information such as the possibility that an abnormality has occurred in the short circuit 60 connected to the electrolytic cell 10 of which order is displayed on the display, a warning light is turned on, or a warning is given. uttering a sound, and the like.

On the other hand, if the residual voltage of the electrolytic cell 10 is less than the predetermined value (NO in S12), the control unit 70 terminates the determination control without issuing a warning in step S13.

In this way, according to the determination control executed by the water electrolysis device 100, it is possible to determine the operating state of the short circuit 60 based on the residual voltage of the electrolysis cell 10, so that the failure of the water electrolysis device 100 can be detected early. can do.

[Effect of water electrolysis device 100]
As described above, the water electrolysis apparatus 100 according to the present embodiment includes a water electrolytic bath 20 in which a plurality of electrolytic cells 10 each including a solid polymer electrolyte membrane 4 and electrodes sandwiching the solid polymer electrolyte membrane 4 are connected in series. , and a plurality of short circuits 60 connected to each of the plurality of electrolysis cells 10 included in the water electrolysis bath 20 and short-circuiting the electrolysis cells 10 when power supply to the water electrolysis bath 20 is stopped.

In the water electrolysis apparatus 100, when the electrolysis is stopped (when the power supply is stopped), the short circuit 60 is closed to short-circuit the electrolysis cell 10, thereby utilizing the fuel cell reaction to remove the oxygen remaining in the electrolysis cell 10 and Can consume hydrogen. Therefore, generation of hydrogen peroxide is suppressed, and as a result, the solid polymer electrolyte membrane 4 is less likely to be decomposed.

Therefore, according to the present embodiment, it is possible to realize the water electrolysis device 100 that can suppress the generation of hydrogen peroxide during the electrolysis stop period and reduce the deterioration of the electrolysis cell 10 .

In addition, according to the configuration of the water electrolysis device 100, the deterioration of the electrolysis cells 10 is reduced, thereby improving the energy efficiency during operation of the water electrolysis device 100. This will contribute to the achievement of the Sustainable Development Goals (SDGs).

[Modification]
(Modification 1)
In the embodiment described above, the configuration example of the water electrolysis device 100 in which one short circuit 60 is connected to each electrolysis cell 10 has been described. However, the water electrolysis device according to the present invention is not limited to this configuration. In the water electrolysis apparatus according to the present invention, one short circuit 60 is connected for each unit of one or two or more adjacent electrolysis cells 10 selected from a plurality of electrolysis cells 10 included in the water electrolysis tank 20. may have been That is, one short circuit 60 may be connected to each unit of a plurality of electrolytic cells 10 (for example, units of about two to three adjacent electrolytic cells 10).

Even with such a configuration, by closing the short circuit 60 and short-circuiting the electrolysis cell 10 during the electrolysis stop period, the oxygen remaining in the electrolysis cell 10 and the oxygen remaining in the electrolysis cell 10 can be can be consumed. Therefore, it is possible to suppress the generation of hydrogen peroxide during the period when electrolysis is stopped, and to reduce deterioration of the electrolytic cell 10 .

(Modification 2)
Further, in the above-described embodiment, the configuration example in which the short circuit 60 includes the fuse 62 has been described. However, it is also possible to omit the fuse 62 in the short circuit 60 .

FIG. 8 is a schematic diagram showing a short circuit 60a that is a modification of the short circuit 60 shown in FIG. As shown in FIG. 8, the short circuit 60a is composed of a relay 61 and a lead wire 63. As shown in FIG. For example, if the opening/closing operation of the relay 61 fails and the relay 61 is closed during the electrolysis operation, the voltage of the electrolysis cell 10 becomes lower than the reference voltage, which is the voltage of the electrolysis cell 10 during normal operation. . Therefore, the control unit 70 acquires the voltage of each electrolysis cell 10 during the electrolysis operation period from the voltmeter V attached to each electrolysis cell 10, and compares the acquired voltage with the reference voltage. If the voltage obtained from the voltmeter V is lower than the reference voltage, the water electrolysis device 100 may have some problem. Therefore, the control unit 70 warns the user that the water electrolysis device 100 may be malfunctioning. As a result, it is possible to prevent an overcurrent from flowing through the short circuit 60a due to the failure of the opening/closing operation of the relay 61, protect the short circuit 60a from overcurrent, and prevent fires from occurring.

An embodiment of the present invention will be described based on FIG. In this embodiment, using the water electrolysis device 100 according to the present invention, the electrolysis voltage rise value (V) is measured in each of the cases where measures against short circuiting of the electrolysis cell 10 are taken during the stop period of electrolysis and where it is not taken. A comparative test was conducted. In the water electrolysis device 100, as the decomposition of the solid polymer electrolyte membrane 4 progresses, the electrolysis voltage rise value during electrolysis operation increases. Therefore, in this comparative test, by comparing the electrolysis voltage rise value when short circuit countermeasures are taken and the electrolysis voltage rise value when short circuit countermeasures are not taken, the effect of suppressing decomposition of the solid polymer electrolyte membrane 4 by short circuit countermeasures. verified.

Table 1 is a table showing the conditions of the comparative test. In the comparative test, under the conditions shown in Table 1, the water electrolyzer 20 was repeatedly operated for 15 seconds and then stopped for 7200 seconds, and the electrolysis voltage rise value during the electrolysis operation was measured.

FIG. 9 is a graph showing the results of the comparative test. A1 and A2 shown in FIG. 9 show the measurement results when measures against short circuits are taken. Further, A3 shown in FIG. 9 shows the measurement result when no measures against short circuits are taken. Specifically, "A1: short circuit at stop_circulation 7,200 sec" shown in FIG. Measured results when control is performed are shown. In addition, "A2: short circuit at stop_circulation 120 sec" shown in FIG. The measurement results are shown when control is performed to stop the circulating water. In addition, "A3: No countermeasure" shown in FIG. 9 is the measurement result when each electrolysis cell 10 is not short-circuited during the electrolysis stop period and control is performed to keep the circulating water flowing for 7200 seconds during the electrolysis stop period. indicates

As shown in FIG. 9, A3, in which short-circuit countermeasures were not taken during the electrolysis stop period, had a larger electrolysis voltage rise value than A1 and A2, in which short-circuit countermeasures were taken. In addition, in A1 and A2 in which short-circuit measures were taken, the electrolytic voltage rise value of A2 was the smallest, and the electrolytic voltage rise value of A1 was between A2 and A3.

From the results of the above comparison test, it was confirmed that the electrolysis voltage rise value during the electrolysis operation period was reduced by taking short-circuit countermeasures during the electrolysis stop period. It is presumed that this is because the generation of hydrogen peroxide was suppressed and the decomposition of the solid polymer electrolyte membrane 4 was suppressed by taking short-circuit countermeasures during the electrolysis stop period.

〔summary〕
A water electrolysis device according to aspect 1 of the present invention is selected from a water electrolysis tank in which a plurality of electrolysis cells each including a solid polymer electrolyte membrane are connected in series, and a plurality of the electrolysis cells included in the water electrolysis tank. a plurality of short circuits connected to each of the one or more electrolytic cell units and short-circuiting the electrolytic cell units when power supply to the water electrolytic bath is stopped.

In the water electrolysis apparatus according to Aspect 2 of the present invention, in Aspect 1 above, the short circuit may be connected for each one of the electrolysis cells.

In the water electrolysis apparatus according to aspect 3 of the present invention, in the above aspect 1 or 2, the operation state of the short circuit is determined based on the residual voltage of the electrolytic cell after a predetermined time has elapsed since the start of short circuiting of the electrolytic cell. A determination unit (control unit 70) may be further provided.

In the water electrolysis device according to Aspect 4 of the present invention, in any one of Aspects 1 to 3, the short circuit further includes a switching unit (relay 61) for switching opening and closing of the short circuit, or It may further include a switching unit (relay 61) that switches between opening and closing of the circuit, and a circuit protection unit (fuse 62) that opens the short circuit when a current of a predetermined value or more flows through the short circuit. .

In the water electrolysis device according to Aspect 5 of the present invention, in Aspect 4, the electrolysis cell includes a catalyst electrode layer having electrode surfaces facing each other, arranged with the solid polymer electrolyte membrane interposed therebetween, and the electrode surfaces A resistance value of the short circuit per unit area may be 0.002 μΩ/mm ² or more and 0.2 μΩ/mm ² or less.

In the water electrolysis device according to aspect 5 of the present invention, in the

above aspect

4 or 5, the electrolytic cell includes catalyst electrode layers arranged with the solid polymer electrolyte membrane interposed therebetween and having electrode surfaces facing each other, A cross-sectional area of the conductive wire used for the short circuit per unit area of the electrode surface may be 0.00006 mm ² /mm ² or more and 0.001 mm ² /mm ² or less.

A method for controlling a water electrolysis device according to aspect 7 of the present invention comprises the steps of: supplying power to a water electrolysis cell in which a plurality of electrolytic cells each including a solid polymer electrolyte membrane are connected in series; and stopping the power supply to the water electrolysis cell. Taking this as an opportunity, a plurality of short circuits for short-circuiting the units of one or more of the electrolysis cells selected from the plurality of electrolysis cells contained in the water electrolysis tank are closed to short-circuit the units of the electrolysis cells. and

A method for controlling a water electrolysis device according to aspect 8 of the present invention is characterized in that, in aspect 7, the operation state of the short circuit is determined based on the residual voltage of the electrolysis cell after a first predetermined time has passed since the start of the short circuit of the electrolysis cell. may further include the step of determining

A method for controlling a water electrolysis device according to aspect 9 of the present invention is the method for controlling a water electrolysis device according to

aspect

7 or 8, in which the flow of circulating water circulating in the water electrolysis device is stopped after a second predetermined time has elapsed from the start of the short circuit of the electrolysis cell. Further steps may be included.

The present invention is not limited to the above-described embodiments, and can be modified in various ways within the scope of the claims. It is included in the technical scope of the invention.

5 6 Catalytic electrode layer 5a 6a Electrode surface 10 Electrolytic cell 20 Water electrolyzer 50 Rectifier 60 60a Short circuit 61 Relay (switching part)
62 Fuse (circuit protection part)
63 conducting wire 70 control unit (determining unit)
100 water electrolyzer

Claims

a water electrolytic bath in which a plurality of electrolytic cells each containing a solid polymer electrolyte membrane are connected in series;
One or more electrolysis cell units selected from the plurality of electrolysis cells included in the water electrolysis bath are connected, and the electrolysis cell units are connected when power supply to the water electrolysis bath is stopped. a plurality of short circuits that short;
A water electrolysis device comprising:
The water electrolysis device according to claim 1, wherein the short circuit is connected for each one of the electrolysis cells.
The water electrolysis apparatus according to claim 1 or 2, further comprising a determination unit that determines the operating state of the short circuit based on the residual voltage of the electrolysis cell after a predetermined time has passed since the start of the short circuit of the electrolysis cell.
The short circuit is
Further comprising a switching unit for switching opening and closing of the short circuit,
or
a switching unit that switches between opening and closing of the short circuit;
3. The water electrolysis device according to claim 1, further comprising a circuit protector that opens the short circuit when a current of a predetermined value or more flows through the short circuit.
The electrolytic cell includes catalyst electrode layers arranged with the solid polymer electrolyte membrane interposed therebetween and having electrode surfaces facing each other,
The water electrolysis device according to claim 4, wherein the resistance value of the short circuit per unit area of the electrode surface is 0.002 µΩ/mm 2 or more and 0.2 µΩ/mm 2 or less.
The electrolytic cell includes catalyst electrode layers arranged with the solid polymer electrolyte membrane interposed therebetween and having electrode surfaces facing each other,
5. The water electrolysis device according to claim 4, wherein the cross-sectional area of the conductive wire used for the short circuit per unit area of the electrode surface is 0.00006 mm 2 /mm 2 or more and 0.001 mm 2 /mm 2 or less. .
A control method for a water electrolysis device,
a step of supplying power to a water electrolytic bath in which a plurality of electrolytic cells each containing a solid polymer electrolyte membrane are connected in series;
When power supply to the water electrolyzer is stopped, a plurality of short circuits are closed for each unit of one or more of the electrolyzed cells selected from the plurality of electrolyzed cells included in the water electrolyzer. and short-circuiting the unit of the electrolytic cell;
A method of controlling a water electrolysis device comprising:
8. The method for controlling a water electrolysis device according to claim 7, further comprising the step of determining the operating state of said short circuit based on the residual voltage of said electrolysis cell after a first predetermined time has passed since said short circuit of said electrolysis cell started. .
The method for controlling a water electrolysis device according to claim 7 or 8, further comprising a step of stopping the flow of circulating water circulating in the water electrolysis device after a second predetermined time has passed since the start of the short circuit of the electrolysis cell.