JP2023128433A - Water electrolysis apparatus and control method - Google Patents

Abstract

To suppress occurrence of a hydrogen peroxide and reduce deterioration of an electrolysis cell during a stop period of electrolysis.SOLUTION: A water electrolysis apparatus comprises: a water electrolytic bath (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), each of which is connected to each of the plurality of electrolysis cells (10) for shorting the electrolysis cells (10) in the wake of the stop of power supply to the water electrolytic bath (20).SELECTED DRAWING: Figure 3

Description

The present invention relates to a solid polymer type water electrolysis device that electrolyzes water to generate hydrogen and oxygen, and a method of controlling the same.

BACKGROUND ART Conventionally, hydrogen production technologies using natural energy as primary energy have been developed, and a solid polymer water electrolysis device is known as one of them. In a solid polymer type water electrolysis device, pure water is electrolyzed by applying a voltage to the solid polymer electrolyte membrane and passing a current through it, and hydrogen (H 2 ) is generated on the negative side of the solid polymer electrolyte membrane and hydrogen (H ₂ ) on the positive side of the solid polymer electrolyte membrane. Oxygen (O ₂ ) is generated.

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

Japanese Patent Application Publication No. 2015-48507 JP2021-46602A

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 ) may be generated. This hydrogen peroxide decomposes the solid polymer electrolyte membrane, potentially causing deterioration of the electrolytic cell.

One aspect of the present invention aims to suppress the generation of hydrogen peroxide during the electrolysis stop period and reduce deterioration of the electrolytic cell.

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

Furthermore, in order to solve the above problem, a method for controlling a water electrolysis device according to one aspect of the present invention includes a step of supplying power to a water electrolyzer in which a plurality of electrolytic cells each including a solid polymer electrolyte membrane are connected in series; Closing a plurality of short circuits that short-circuit each unit of one or more electrolytic cells selected from a plurality of electrolytic cells included in the water electrolyzer when the power supply to the water electrolyzer is stopped. and short-circuiting the units of the electrolytic cell.

According to one aspect of the present invention, generation of hydrogen peroxide during the electrolysis stop period can be suppressed, and deterioration of the electrolytic cell can be reduced.

1 is a block diagram showing a schematic configuration of a water electrolysis device according to an embodiment of the present invention. FIG. 2 is a sectional view showing the configuration of the water electrolyzer shown in FIG. 1. FIG. 2 is a block diagram showing a schematic configuration of a water electrolyzer, a rectifier, and a short circuit shown in FIG. 1. FIG. FIG. 3 is a schematic diagram showing a schematic configuration of the short circuit. It is a flow chart which shows an example of stop control performed by the water electrolysis device. It is a graph showing the time change of the residual voltage of each electrolytic cell during the electrolysis stop period. It is a flow chart which shows an example of judgment control performed by the water electrolysis device. 5 is a schematic diagram showing a modification of the short circuit shown in FIG. 4. FIG. It is a graph showing the measurement results of a comparative test in Examples.

An embodiment of the present invention will be described below based on FIGS. 1 to 8. However, the following explanation is an example of the water electrolysis device according to the present invention, and the technical scope of the present invention is not limited to the illustrated example.

[Configuration of water electrolysis device 100]
First, the configuration of a water electrolysis device 100 according to an embodiment of the present invention will be described based on FIGS. 1 and 2. FIG. 1 is a block diagram showing a schematic configuration of a water electrolysis device 100 according to this embodiment. FIG. 2 is a sectional view showing the configuration of the water electrolyzer 20 shown in FIG. 1. As shown in FIG. The water electrolysis device 100 according to the present embodiment electrolyzes pure water by applying a voltage to a solid polymer electrolyte membrane and passing an electric current through the solid polymer electrolyte membrane to generate hydrogen (H ₂ ) and oxygen (O ₂ ). This is a polymer 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, and a 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 section) 50 and a short circuit 60 connected to the water electrolysis tank 20, and a control section (determination section) 70 that controls the operation of the water electrolysis device 100 as a whole.

The water circulation line 23 is a line that circulates water from the hydrogen gas-liquid separator 21 and the oxygen gas-liquid separator 22 to the water electrolyzer 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 . Furthermore, a hydrogen cooler 31 is disposed at the outlet of the hydrogen gas-liquid separator 21, and an oxygen cooler 32 is disposed 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 from the water circulation line 23, processes it, and sends the treated water to the pure water tank 25. 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 performs ion exchange treatment on the cooled water are arranged in the branch line 41. The downstream end of the branch line 41 is connected to the pure water tank 25 . Further, 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 rate adjustment valve) 29 is arranged on the upstream side of the branch line 41. The opening and closing of the blow valve 29 is automatically controlled by the electrical conductivity of the circulating water obtained from the electrical conductivity controller 30 disposed between the circulating pump 27 and the circulating water cooler 28 in the water circulating line 23.

The water electrolyzer 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 electrolyzer cell stack in which a plurality of electrolytic cells 10 are connected in series. The water electrolyzer 20 includes an anode main electrode (electrode) 1 and a cathode main electrode (electrode) 2 arranged at both ends thereof, and a plurality of anode main electrodes (electrodes) 1 and cathode main electrodes (electrodes) 2 arranged in series between the anode main electrode 1 and the cathode main electrode 2. It mainly consists of an electrolytic cell 10 and four tightening bolts and nuts that integrate the plurality of electrolytic cells 10. In the illustrated example, the electrolytic cells 10 are connected in parallel in the horizontal direction, but the electrolytic cells 10 may be connected in parallel in the horizontal direction.

One electrolytic cell 10 includes the anode side of a bipolar plate 9 made of titanium alloy, a porous anode power supply body 7, a solid polymer electrolyte membrane 4, and catalyst electrode layers 5 and 6 provided on both sides thereof. It is composed of an MEA (Membrane Electrode Assemblies) 3, a porous cathode power supply body 8, and the cathode side of an adjacent bipolar plate 9.

Note that each electrolytic cell 10 disposed at both ends of the water electrolyzer 20 is configured to include an anode main electrode 1 or a cathode main electrode 2 instead of one of the two bipolar plates 9. That is, the electrolytic cell 10 disposed at the anode side end of the water electrolyzer 20 is connected to the anode main electrode 1, the anode power supply body 7, the MEA 3, the cathode power supply body 8, and the cathode side of the bipolar plate 9. configured. Further, the electrolytic cell 10 disposed at the cathode side end of the water electrolyzer 20 is connected to the anode side of the bipolar plate 9, the anode power supply body 7, the MEA 3, the cathode power supply body 8, and the cathode main electrode 2. configured.

In the water electrolyzer 20 , water supplied from the water supply header 11 arranged at the lower part of the water electrolyzer 20 passes through the anode power supply body 7 and reaches the anode side catalyst electrode layer 5 of the MEA 3 . The electric power applied at the anode side catalyst electrode layer 5 causes an electrolysis reaction of water to generate oxygen. The generated oxygen passes through the anode power supply body 7 and 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 disposed at the top of the water electrolyzer 20. be discharged. 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 power supply body 8 and pass through a vertical channel provided on the cathode side of the bipolar plate 9. The hydrogen rises within the water electrolyzer 20 and is discharged to the hydrogen header 13 located above the water electrolyzer 20 .

This water electrolyzer 20 is supplied with electric power (DC current) necessary 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 electrolyzer 20 and supplies power to the water electrolyzer 20 . As the electric power supplied to the water electrolyzer 20, in addition to electric power from a commercial power source, renewable energy such as solar power generation or wind power generation, or surplus power thereof, or the like can be used.

Here, the amount of power generated from renewable energy or its surplus power fluctuates greatly due to the influence of weather and the like. When such unstable power is used, it is necessary to stop the electrolysis operation of the water electrolyzer 20 during a period when the power necessary for the operation of the water electrolysis device 100 is not obtained. During this electrolysis stop period, oxygen remaining in the electrolytic cell 10 reacts with hydrogen, and hydrogen peroxide may be generated. There was a possibility that the electrolytic cell 10 would deteriorate due to the solid polymer electrolyte membrane 4 being decomposed by this hydrogen peroxide.

Therefore, in the water electrolysis device 100, a short circuit 60 is connected to each electrolysis cell 10. The short circuit 60 is short-circuited for each electrolytic cell 10 during the period when the water electrolyzer 20 is not electrolyzed. In other words, the short circuit 60 short-circuits between the adjacent electrodes (anode main electrode 1, cathode main electrode 2, bipolar plate 9) of the electrolytic cell 10 during an electrolysis stop period of the water electrolyzer 20. In this way, by closing the short circuit 60 and short-circuiting the electrolytic cell 10 during the electrolysis stop period, the oxygen and hydrogen remaining in the electrolytic 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 becomes difficult to decompose. Therefore, generation of hydrogen peroxide during the electrolysis stop period can be suppressed, and deterioration of the electrolytic cell 10 can be reduced. Note that details of the short circuit 60 will be described later.

The hydrogen gas-liquid separator 21 separates hydrogen generated at the cathode of the water electrolyzer 20 from water. Further, the oxygen gas-liquid separator 22 separates oxygen generated at the anode of the water electrolyzer 20 from water. In FIG. 1, oxygen generated at the anode of a water electrolyzer 20 is sent to an oxygen gas-liquid separator 22. Further, 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 electrolyzer 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 piping, and are controlled so that the water surface level of the hydrogen gas-liquid separator 21 and the water surface level of the oxygen gas-liquid separator 22 are 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 via the water circulation line 23, and a portion of it is sent to the pure water tank 25 via the branch line 41. sent to.

The pure water tank 25 stores water that is electrolyzed in the water electrolyzer 20. The pure water tank 25 stores water that has been processed by the first ion exchanger 24 from newly supplied water (city water, etc.) to the water electrolyzer 20 . Further, the pure water tank 25 stores water obtained by treating circulating water taken out from the water circulation line 23 to the branch line 41 by the second ion exchanger 43. A supply pump 26 for sending water from 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 once stored in the pure water tank 25 is sent to the oxygen gas-liquid separator 22 by the supply pump 26 in accordance with a preset level of the oxygen gas-liquid separator 22.

The circulating water flowing through the water circulation line 23 is adjusted to a predetermined temperature (for example, 80° C.) by the circulating water cooler 28 and sent to the water electrolyzer 20 by the circulation 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 or less, and when the value is higher than that, the blow valve 29 is opened, and when it is less than that, the blow valve 29 is closed. It has become. The circulating water taken out to the branch line 41 is cooled to room temperature by a blow water cooler 42, supplied to a second ion exchanger 43, treated to have an electrical conductivity of, for example, 0.5 μS/cm or less, and then sent to a pure water tank. 25. In this way, by taking out a part of the circulating water in the water circulation 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, for example, a processor such as a CPU (Central Processing Unit). Alternatively, the control unit 70 is configured by a logic circuit formed on an integrated circuit (IC chip) or the like.

The control unit 70 controls power supply to the water electrolyzer 20 and controls the 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 electrolyzer 20 . For example, the control unit 70 closes the short circuit 60 when the power supply to the water electrolyzer 20 is stopped, and short-circuits 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 period of time has elapsed from the start of the short circuit of the electrolytic cell 10 .

[Configuration of short circuit 60]
Next, the configuration of the short circuit 60 included in the water electrolysis device 100 will be described based on FIGS. 3 and 4. FIG. 3 is a block diagram showing a schematic configuration of the water electrolyzer 20, the rectifier 50, and the short circuit 60 shown in FIG. FIG. 4 is a schematic diagram showing a schematic configuration of the short circuit 60 shown in FIG. 3.

As shown in FIG. 3, a plurality of electrolytic cells 10 are connected in series to the water electrolyzer 20, and a short circuit 60 is connected to each of these electrolytic cells 10. If the water electrolyzer 20 is, for example, a cell stack in which 30 electrolytic cells 10 are connected in series, 30 short circuits 60, the same number as the electrolytic cells 10, are arranged, and one short circuit is provided for each electrolytic 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 constitute each electrolytic cell 10. The short circuit 60 may be electrically connected to the two bipolar plates 9 using, for example, a measurement terminal of a voltmeter V attached to each electrolytic cell 10.

The resistance value (required resistance value) of the short-circuit circuit 60 is adjusted within a range that can consume the residual voltage of the electrolytic cell 10 at the time of short-circuiting and obtain the short-circuiting effect of the electrolytic cell 10. The residual voltage of the electrolytic cell 10 at the time of a short circuit depends on the configuration of the water electrolyzer 20, for example, the electrode surfaces 5a and 6a of the catalyst electrode layers 5 and 6 facing each other with the solid polymer electrolyte membrane 4 in between (see FIG. 2). Varies depending on 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. More preferably, it is .1 μΩ/mm ² or less. By setting the resistance value of the short circuit 60 within this range, the residual voltage of the electrolytic cell 10 at the time of short circuit can be appropriately consumed and the short circuit effect can be suitably obtained.

Short circuit 60 includes a relay 61, a fuse 62, and a conducting wire 63. In addition to each of these configurations, the short circuit 60 may further include a resistive element as necessary.

The relay (switching unit) 61 is a switch that opens and closes the short circuit 60. Switching of opening and closing of the relay 61 is controlled by a control unit 70. The relay 61 is controlled to open at or just before the start of electrolysis operation of the water electrolyzer 20, in other words, at or just before the start of the operation of the rectifier 50. Therefore, during the electrolytic operation period, the short circuit 60 is opened, and the electrolytic cell 10 is prevented from being short-circuited. On the other hand, the relay 61 is controlled to be closed while the water electrolyzer 20 is in an electrolysis stop period. Therefore, during the electrolysis stop period, the short circuit 60 becomes a closed circuit, and the electrolytic cell 10 is short-circuited.

Note that when a semiconductor relay is used as the relay 61, leakage current from the semiconductor relay occurs, and if a current exceeding the rated value is input, the semiconductor relay may be damaged. For this reason, it is preferable to use a mechanical relay as the relay 61.

The fuse (circuit protection unit) 62 opens (cuts off) 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 more, or when the temperature of the fuse 62 reaches a predetermined temperature or higher. ) to protect the short circuit 60. For example, if a malfunction occurs in the opening/closing operation of the relay 61 and the relay 61 is closed during the electrolytic operation, an overcurrent of a predetermined value or more flows through the short circuit 60, which generates heat and may cause a fire or the like. When such an overcurrent flows through the short circuit 60, the fuse element of the fuse 62 is blown and the short circuit 60 is opened. Therefore, the short circuit 60 can be protected from overcurrent, and the occurrence of fires and the like can be prevented.

The fuse 62 used has a characteristic of being blown by an overcurrent flowing through the short circuit 60 when the relay 61 is closed during the electrolysis operation. For example, a fuse 62 that has a fusing energy (l ² t) of about 22,500 or more, which is the thermal energy that passes through the fuse 62 from the time an overcurrent occurs until the fuse element blows out, can be suitably used.

Further, when a thermal fuse is used as the fuse 62, when the temperature of the fuse 62 becomes higher than a specified temperature due to an overcurrent, the fuse element melts and the short circuit 60 is opened. 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.

The conducting wire 63 is a cable made of a conductive material. The conducting wire 63 is, for example, a copper vinyl cable having a size of 3.5 sq or more. The conductor thickness (cross-sectional area) and length of the conducting wire 63 are appropriately selected based on the required resistance value of the short circuit 60 necessary to consume the residual voltage of the electrolytic 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. More preferably, it is 0.00009 mm ² /mm ² or more and 0.0005 mm ² /mm ² or less. By using the conductive wire 63 having a cross-sectional area within this range, the required resistance value of the short circuit 60 necessary for consuming the residual voltage of the electrolytic cell 10 at the time of a short circuit can be obtained without using a resistance element. can. Furthermore, heat generation in the short circuit 60 can be suppressed with respect to the current generated by the fuel cell reaction in the electrolytic cell 10 during a short circuit, and troubles such as disconnection of the conducting wire 63 can be prevented.

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

(stop control)
First, the stop control (control method) of the water electrolysis device 100 will be explained based on FIGS. 5 and 6. FIG. 5 is a flowchart showing an example of stop control executed by the water electrolysis device 100. During the electrolysis operation period of the water electrolyzer 20, the control unit 70 controls the rectifier 50 and supplies power to the water electrolyzer 20. Further, the control unit 70 controls the relay 61 to open, thereby opening the short circuit 60.

In the stop control of the water electrolysis device 100, the control unit (determination unit) 70 determines whether there is a need to stop the electrolysis operation of the water electrolysis tank 20 (S1).

For example, when the amount of hydrogen in a hydrogen tank (not shown) that stores hydrogen generated in the water electrolyzer 20 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, and the electrolysis operation of the water electrolyzer 20 is stopped (S2). Further, for example, when the amount of power generated by renewable energy becomes 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). Further, for example, when receiving an input from the user for an instruction to stop the electrolytic operation of the water electrolyzer 20, the control unit 70 determines that it is necessary to stop the electrolytic operation (YES in S1), and The electrolysis operation of the water electrolyzer 20 is stopped by stopping power supply to the water electrolyzer 20 (S2).

On the other hand, if 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 repeatedly executes the determination in step S1. .

Next, the control unit 70 executes control to short-circuit each electrolytic cell 10, triggered by stopping power supply to the water electrolyzer 20 (stopping electrolysis) in step S2 (S3). Specifically, the control unit 70 switches the relays 61 of each short circuit 60 from open to closed at the same time as the electrolysis stops, or immediately after, to make each short circuit 60 a closed circuit, thereby causing each electrolytic cell 10 to be closed. 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 reduced. Therefore, generation of hydrogen peroxide within the electrolytic cell 10 is suppressed, and as a result, the solid polymer electrolyte membrane 4 becomes difficult to decompose.

FIG. 6 is a graph showing temporal changes in the residual voltage of each electrolytic cell 10 during the electrolysis stop period. FIG. 6 shows the change over time in the residual voltage of each electrolytic cell 10 in a cell stack (water electrolyzer 20) in which ten electrolytic cells 10 are vertically stacked. Note that "No. 1 cell" to "No. 10 cell" in the figure indicate that the "No. 1 cell" to "No. 1 cell" are stacked in the order from the bottom in the vertical direction. That is, the electrolytic cell 10 located at the top in the vertical direction is referred to as the "No. 1 cell", and the electrolytic cell 10 located at the bottom in the vertical direction is designated as the "No. 10 cell".

Since the amount of oxygen and hydrogen remaining in the electrolytic cell 10 when electrolysis is stopped differs for each electrolytic cell 10, the residual voltage of each electrolytic cell 10 varies from "No. 1 cell" to "No. .10 cells". For this reason, for example, when all of the plurality of electrolytic cells 10 are short-circuited by one short circuit 60, the reduction in residual voltage of each electrolytic cell 10 varies, and the generation of hydrogen peroxide within the electrolytic cell 10 is effectively suppressed. I can't suppress it.

Therefore, it is preferable that one short circuit 60 is connected to each electrolytic cell 10. This makes it possible to individually short-circuit each electrolytic cell 10 in step S3, effectively suppressing the generation of hydrogen peroxide during the electrolysis stop period, and reducing deterioration of the electrolytic cell 10. Further, the residual voltage of the water electrolyzer 20 increases depending on the number of electrolytic cells 10 connected in series. For this reason, for example, there is a risk of electric shock when maintaining the water electrolyzer 20 during the electrolysis stop period, but by short-circuiting each electrolytic cell 10 individually to efficiently reduce the residual voltage, the water electrolyzer 20 can be maintained safely.

In addition, when the control unit 70 executes the short-circuiting control in step S<b>3 , it starts determination control for determining the operating state of the short-circuiting circuit 60 . Note that details of the determination control will be described later.

Next, the control unit 70 short-circuits the electrolytic cell 10 in step S3, and then executes control to cool the circulating water (S4). During electrolysis operation, the circulating water is at high temperature and pressure. Therefore, the control unit 70 controls the circulating water cooler 28 to lower the temperature of the circulating water than during 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 a hydrogen exhaust control valve (not shown) disposed downstream of the hydrogen cooler 31, for example, and depressurizes the water electrolyzer 20 by exhausting hydrogen into the atmosphere.

Finally, after reducing the pressure in the water electrolyzer 20 in step S5, the control unit 70 executes control to stop circulating water (S6). The control unit 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.

As described above, the stop control performed by the water electrolysis device 100 includes step S3 of closing the short circuit 60 to short-circuit the electrolytic cell 10 when the power supply to the water electrolyzer 20 is stopped. Thereby, 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 becomes difficult to decompose. Therefore, generation of hydrogen peroxide during the electrolysis stop period can be suppressed, and deterioration of the electrolytic cell 10 can be reduced.

(judgment control)
Next, determination control (control method) for determining the operating state of the short circuit 60 will be described based on FIG. 7. FIG. 7 is a flowchart showing an example of the 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 from the start of short circuiting (S11) of the electrolytic cell 10, it is possible that some kind of malfunction has occurred in the short circuit 60. There is sex. Therefore, the control unit 70 executes 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 a predetermined time has elapsed since short-circuiting of the electrolytic cell 10 was started in step S3 shown in FIG. 5 (S11). If the predetermined time has not elapsed since the start of short circuiting of the electrolytic cell 10 (NO in S11), the control unit 70 waits until the predetermined time has elapsed.

On the other hand, if a predetermined period of time has elapsed since the start of short circuiting of the electrolytic cell 10 (YES in S11), the control unit 70 determines whether 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 electrolytic cell 10 based on the output value from the voltmeter V attached to each electrolytic cell 10, for example, and determines whether each acquired residual voltage is equal to or higher than a predetermined value. If at least one of the residual voltages of each electrolysis cell 10 is equal to or higher than the predetermined value (YES in S12), there is a possibility that an abnormality has occurred in the water electrolysis device 100.

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 an abnormality has occurred in the water electrolysis device 100 (S13). The warning method is not particularly limited, but may include, for example, displaying information such as the possibility that an abnormality has occurred in the short circuit 60 connected to the electrolytic cell 10, turning on a warning light, or warning. Examples include emitting sounds.

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 ends the determination control without issuing a warning in step S13.

In this manner, according to the determination control executed by the water electrolysis device 100, the operating state of the short circuit 60 can be determined based on the residual voltage of the electrolytic cell 10, so that a malfunction in the water electrolysis device 100 can be discovered early. can do.

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

In the water electrolysis device 100, by closing the short circuit 60 and short-circuiting the electrolytic cell 10 when electrolysis is stopped (when power supply is stopped), oxygen remaining in the electrolytic cell 10 is removed using a fuel cell reaction. Hydrogen can be consumed. Therefore, generation of hydrogen peroxide is suppressed, and as a result, the solid polymer electrolyte membrane becomes difficult to decompose.

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 electrolytic cell 10.

Furthermore, with a configuration like the water electrolysis device 100, energy efficiency during operation of the water electrolysis device 100 is improved by reducing deterioration of the electrolytic cell 10. This will contribute to achieving the Sustainable Development Goals (SDGs).

[Modified example]
(Modification 1)
In the embodiment described above, a configuration example of the water electrolysis device 100 in which one short circuit 60 is connected to each electrolytic 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 device according to the present invention, one short circuit 60 is connected to each unit of one or two or more adjacent electrolytic cells 10 selected from the plurality of electrolytic cells 10 included in the water electrolyzer 20. may have been done. In other words, one short circuit 60 may be connected to each unit of a plurality of electrolytic cells 10 (for example, a unit of about two to three adjacent electrolytic cells 10).

Even with such a configuration, by closing the short circuit 60 and short-circuiting the electrolytic cell 10 during the electrolysis stop period, the remaining oxygen and oxygen in the electrolytic cell 10 can be removed using the fuel cell reaction. can be consumed. Therefore, generation of hydrogen peroxide during the electrolysis stop period can be suppressed, and deterioration of the electrolytic cell 10 can be reduced.

(Modification 2)
Moreover, in the embodiment described above, a 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 includes a relay 61 and a conducting wire 63. For example, if a problem occurs in the opening/closing operation of the relay 61 and the relay 61 is closed during the electrolytic operation, the voltage of the electrolytic cell 10 will be lower than the reference voltage, which is the voltage of the electrolytic cell 10 during normal operation. . Therefore, the control unit 70 acquires the voltage of each electrolytic cell 10 during the electrolysis operation period from the voltmeter V attached to each electrolytic cell 10, and compares the acquired voltage with a reference voltage. If the voltage obtained from the voltmeter V is lower than the reference voltage, there is a possibility that some kind of malfunction has occurred in the water electrolysis device 100. Therefore, the control unit 70 warns the user that there is a possibility that the water electrolysis device 100 is malfunctioning. Thereby, it is possible to avoid overcurrent from flowing into the short circuit 60 due to a malfunction in the opening/closing operation of the relay 61, protect the short circuit 60 from overcurrent, and prevent the occurrence of a fire or the like.

An embodiment of the present invention will be described based on FIG. 9. In this example, the water electrolysis device 100 according to the present invention is used to measure the electrolysis voltage increase value (V) when short-circuit measures are taken and when no short-circuit measures are taken for the electrolysis cell 10 during the electrolysis stop period. 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 increase value during the electrolysis operation period increases. Therefore, in this comparative test, the effect of suppressing the decomposition of the solid polymer electrolyte membrane 4 due to short circuit measures was compared by comparing the electrolysis voltage increase value when short circuit measures were taken and the electrolysis voltage rise value when no short circuit measures were taken. was verified.

表１は、比較試験の条件を示す表である。比較試験では、表１に示す条件下において、水電解槽２０を１５秒間電解運転した後に７２００秒間電解停止する制御を繰り返し行い、電解運転期間中の電解電圧上昇値を計測した。

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 electrolysis for 15 seconds and then stopped for 7200 seconds, and the electrolysis voltage increase value during the electrolysis operation period was measured.

FIG. 9 is a graph showing the results of a comparative test. A1 and A2 shown in FIG. 9 show measurement results when short-circuit measures were taken. Moreover, A3 shown in FIG. 9 shows the measurement results when no short-circuit measures were taken. Specifically, "A1: Short circuit at stop_circulation 7,200 sec" shown in FIG. 9 short-circuits each electrolytic cell 10 during the electrolysis stop period, and continues to flow circulating water for 7200 seconds during the electrolysis stop period. The measurement results when control is performed are shown. In addition, "A2: Short circuit at stop_circulation 120 sec" shown in FIG. 9 short-circuits each electrolytic cell 10 during the electrolysis stop period, and stops the circulation pump 27 120 seconds (second predetermined time) after the start of the short circuit. The measurement results are shown when the control is performed to stop the circulating water. In addition, "A3: No countermeasure" shown in FIG. 9 is the measurement result when each electrolytic cell 10 is not short-circuited during the electrolysis stop period and the circulating water is continued to flow for 7200 seconds during the electrolysis stop period. shows.

As shown in FIG. 9, A3, in which no short-circuit measures were taken during the electrolysis stop period, had a larger electrolytic voltage increase value than A1 and A2, in which short-circuit measures were taken. In addition, in A1 and A2 to which short-circuit measures were taken, the electrolytic voltage increase value of A2 was the smallest, and the electrolytic voltage increase value of A1 was approximately between A2 and A3.

The results of the above comparative tests confirmed that by taking short-circuit measures during the electrolysis stop period, the electrolysis voltage increase value during the electrolysis operation period was reduced. This is presumed to be because the generation of hydrogen peroxide was suppressed by taking short-circuit measures during the electrolysis stop period, and the decomposition of the solid polymer electrolyte membrane 4 was suppressed.

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

In the water electrolysis device according to the second aspect of the present invention, in the first aspect, the short circuit may be connected to each electrolytic cell.

In the water electrolysis device according to aspect 3 of the present invention, in aspect 1 or 2, the operating state of the short circuit is determined based on the residual voltage of the electrolytic cell after a predetermined time has elapsed from the start of the short circuit of the electrolytic cell. It may further include a determination section (control section 70).

In the water electrolysis device according to aspect 4 of the present invention, in any one of aspects 1 to 3 above, the short circuit further includes a switching unit (relay 61) that switches opening and closing of the short circuit, or the short circuit The circuit may further include a switching unit (relay 61) that switches the 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 electrolytic cell includes a catalyst electrode layer disposed with the solid polymer electrolyte membrane in between and having electrode surfaces facing each other, and the electrode surface The resistance value of the short circuit per unit area of 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 a catalyst electrode layer disposed with the solid polymer electrolyte membrane in between and having electrode surfaces facing each other, and The cross-sectional area of the conducting 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 includes a step of supplying power to a water electrolyzer in which a plurality of electrolytic cells each including a solid polymer electrolyte membrane are connected in series, and a step in which power supply to the water electrolyzer is stopped. Taking this as an opportunity, close a plurality of short circuits that short-circuit each unit of one or more electrolytic cells selected from the plurality of electrolytic cells included in the water electrolyzer, and short-circuit the units of electrolytic cells. and a step of doing so.

In the method for controlling a water electrolysis device according to aspect 8 of the present invention, in aspect 7, the operating state of the short circuit is determined based on the residual voltage of the electrolytic cell after a first predetermined period of time has elapsed from the start of short circuiting of the electrolytic cell. The method may further include a step of determining.

A control method for a water electrolysis device according to aspect 9 of the present invention is, in aspect 7 or 8, stopping the flow of circulating water circulating through the water electrolysis device after a second predetermined time has elapsed from the start of short-circuiting of the electrolysis cell. It may further include a step.

The present invention is not limited to the embodiments described above, and various changes can be made within the scope of the claims, and the present invention also includes embodiments obtained by appropriately combining the technical means disclosed in the embodiments. falls within the technical scope of the invention.

5・6 Catalyst 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 section)
63 Conductor 70 Control section (judgment section)
100 Water electrolysis device

Claims (9)

A water electrolyzer in which multiple electrolytic cells including a solid polymer electrolyte membrane are connected in series;
One or more units of the electrolytic cells selected from the plurality of electrolytic cells included in the water electrolyzer are connected, and the units of the electrolytic cells are connected when the power supply to the water electrolyzer is stopped. multiple short circuits,
A water electrolysis device comprising: The water electrolysis device according to claim 1, wherein the short circuit is connected for each electrolysis cell. The water electrolysis device 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 period of time has elapsed from the start of the short circuit of the electrolysis cell. The short circuit is
further comprising a switching unit that switches opening and closing of the short circuit;
or
a switching unit that switches opening and closing of the short circuit;
The water electrolysis device according to any one of claims 1 to 3, further comprising a circuit protection unit that opens the short circuit when a current of a predetermined value or more flows through the short circuit. The electrolytic cell includes a catalyst electrode layer disposed with the solid polymer electrolyte membrane in between 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 a catalyst electrode layer disposed with the solid polymer electrolyte membrane in between and having electrode surfaces facing each other,
The water according to claim 4 or 5, 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. Electrolyzer. A method for controlling a water electrolysis device, the method comprising:
A step of supplying power to a water electrolyzer in which a plurality of electrolytic cells including a solid polymer electrolyte membrane are connected in series;
Closing a plurality of short circuits that short-circuit each unit of one or more electrolytic cells selected from a plurality of electrolytic cells included in the water electrolyzer when the power supply to the water electrolyzer is stopped. and short-circuiting the units of the electrolytic cell;
A method of controlling a water electrolysis device including: The method for controlling a water electrolysis device according to claim 7, further comprising the step of determining the operating state of the short circuit based on the residual voltage of the electrolytic cell after a first predetermined period of time has elapsed from the start of the short circuit of the electrolytic cell. . The method for controlling a water electrolysis device according to claim 7 or 8, further comprising the step of stopping the flow of circulating water circulating through the water electrolysis device after a second predetermined period of time has elapsed from the start of short circuiting of the electrolysis cell.

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