Water electrolysis system

Abstract

To provide a water electrolysis system in which precipitates of an electrolytic solution are hardly accumulated in a flow path of a cleaning liquid.SOLUTION: The water electrolysis system 1 includes the liquid storage tank 3 that stores the electrolytic solution, the water electrolysis cell 4 in which the electrolyte membrane 20 is located between the anode portion 30 and the cathode portion 40, the first flow passage 50 in which the first groove portion 51 is formed on the surface facing the anode portion 30, the second flow passage 60 in which the second groove portion 61 is formed on the surface facing the cathode portion 40, the first supply 80 that supplies the electrolytic solution from the liquid storage tank 3 to the first groove portion 51, and the second supply 90 that supplies the cleaning liquid for cleaning the cathode portion 40 to the second groove portion 61. The second groove 61 includes the first portion 63 extending along the first axis and the second portion 70 extending along the second axis intersecting the first axis, and the inner wall surface of the portion where the first portion 63 and the second portion 70 are coupled is R-shaped.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to techniques for water electrolysis. [Background technology]

[0002] For example, in a water electrolysis system, it has been proposed to supply a cleaning solution to the water electrolysis cell in order to prevent deterioration of the water electrolysis cell due to deposits formed by the concentration of components of the electrolyte. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-256911 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses a cleaning method in which an acid cleaning solution is supplied to a water circulation path on the cathode side to prevent contamination of a membrane electrode assembly by ions migrating from the anode side through an electrolyte membrane or metal ions eluted due to deterioration of the metal in the power feeder. Cleaning the cathode part with a cleaning solution has a problem in that deposits tend to accumulate at corners of the cleaning solution flow path. In consideration of the above circumstances, one aspect of the present disclosure aims to provide a water electrolysis system in which deposits from the electrolyte solution are less likely to accumulate in the cleaning solution flow path. [Means for solving the problem]

[0005] In order to solve the above problems, a water electrolysis system according to one embodiment of the present disclosure includes a storage tank that stores an electrolytic solution, a water electrolysis cell including an electrolyte membrane located between an anode and a cathode, a first flow path portion having a first groove formed in a surface facing the anode, a second flow path portion having a second groove formed in a surface facing the cathode, a first supply portion that supplies the electrolytic solution from the storage tank to the first groove, and a second supply portion that supplies a cleaning solution for cleaning the cathode to the second groove, wherein the second groove portion includes a first portion extending along a first axis and a second portion extending along a second axis intersecting the first axis, and the inner wall surface of the portion where the first portion and the second portion are connected is rounded. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a configuration diagram of a water electrolysis system according to a first embodiment. [Figure 2] FIG. 1 is a schematic diagram of a water electrolysis cell according to a first embodiment. [Figure 3] FIG. 1 is a block diagram illustrating a functional configuration of a water electrolysis system. [Figure 4] 4 is a flowchart showing the operation of the control system in the first embodiment. [Figure 5] FIG. 4 is a plan view of a flow path forming surface of a second groove portion according to the first embodiment. [Figure 6] 4 is a cross-sectional view of a flow path forming surface of a second groove portion according to the first embodiment. FIG. [Figure 7] 10 is a schematic diagram showing how a cleaning liquid flows when the first surface of the outflow portion and the second surface of the second portion according to the first embodiment are connected in a discontinuous angular shape. FIG. [Figure 8] FIG. 10 is a schematic diagram illustrating how a cleaning liquid flows when the first surface of the outflow portion and the second surface of the second portion according to the first embodiment are rounded. DETAILED DESCRIPTION OF THE INVENTION

[0007] The embodiments for carrying out the present disclosure will be described with reference to the drawings. Note that the dimensions and scale of each element in each drawing may differ from those of the actual product. Furthermore, the embodiment described below is an exemplary embodiment that may be envisioned when carrying out the present disclosure. Therefore, the scope of the present disclosure is not limited to the embodiment exemplified below.

[0008] A: First embodiment 1 is a schematic diagram of a water electrolysis system 1 according to a first embodiment. The water electrolysis system 1 of the first embodiment includes a liquid storage tank 3, a power supply device 2, a water electrolysis cell 4, a gas-liquid separator 5, a gas-liquid separator 6, a first supply unit 80, a second supply unit 90, a pH sensor 7, and a control system 8.

[0009] The storage tank 3 is a tank for storing the electrolyte used in water electrolysis. The storage tank 3 can be made of a resin material (or a metal material) that is highly resistant to the corrosive action of the electrolyte. The electrolyte is an aqueous solution in which an electrolyte is dissolved to facilitate water electrolysis. Examples of the electrolyte that can be used include an aqueous potassium hydroxide solution and an aqueous sodium hydroxide solution. However, the type of electrolyte is not limited to the above examples and may be any type.

[0010] The power supply device 2 is a DC power supply that supplies the water electrolysis cell 4 with electricity used in water electrolysis.

[0011] The water electrolysis cell 4 is a mechanism for producing hydrogen and oxygen from an electrolytic solution by water electrolysis. FIG. 2 is a schematic diagram of the water electrolysis cell 4 in the first embodiment. The water electrolysis cell 4 includes a membrane electrode assembly 10, a first flow path section 50, and a second flow path section 60. The membrane electrode assembly 10 is disposed between the first flow path section 50 and the second flow path section 60. Specifically, the first flow path section 50 and the second flow path section 60 are fixed to each other with fasteners such as screws or bolts, and the membrane electrode assembly 10 is sandwiched between the first flow path section 50 and the second flow path section 60.

[0012] The membrane electrode assembly 10 generates hydrogen and oxygen through water electrolysis. The membrane electrode assembly 10 of the first embodiment is configured by laminating an electrolyte membrane 20, an anode section 30, and a cathode section 40. Specifically, the electrolyte membrane 20 is disposed between the anode section 30 and the cathode section 40.

[0013] The electrolyte membrane 20 is an ion exchange membrane that separates the anode section 30 and the cathode section 40. An example of the electrolyte membrane 20 is a membrane that exchanges hydroxide ions (OH - However, the type of the electrolyte membrane 20 is not limited to the above examples, and may be any type.

[0014] The anode section 30 is a section that generates oxygen through water electrolysis (and also promotes this generation). 2OH - →H2O+1 / 2·O2+2e - The anode section 30 includes a first catalyst layer 32 and a first diffusion layer 31. The first reaction generates oxygen gas.

[0015] The first catalyst layer 32 is located between the electrolyte membrane 20 and the first diffusion layer 31. The first catalyst layer 32 is a thin film that adheres closely to the electrolyte membrane 20 and promotes the first reaction described above. The first catalyst layer 32 is formed of a metal material such as iridium (Ir), iron (Fe), or nickel (Ni). The first catalyst layer 32 may also be formed of an oxide of any of the metal materials listed above.

[0016] The first diffusion layer 31 is an element for efficiently separating and discharging oxygen gas generated by the first reaction. For example, a nickel (Ni) foam or a porous membrane made of a carbon-based material is used as the first diffusion layer 31. The first diffusion layer 31 also functions as an element for efficiently supplying the electrolyte to the first catalyst layer 32 (and further to the electrolyte membrane 20). The first diffusion layer 31 is also made of a conductive material and functions as a path for electrons exchanged with the first catalyst layer 32.

[0017] The cathode section 40 is a section that generates hydrogen through water electrolysis (and also a section that promotes this generation). 2H2O+2e - →H2+2OH - The second reaction generates hydrogen gas. The overall reaction in the water electrolysis cell 4 is as follows: H2O → H2 + 1 / 2 O2 The cathode section 40 includes a second catalyst layer 42 and a second diffusion layer 41.

[0018] The second catalyst layer 42 is located between the electrolyte membrane 20 and the second diffusion layer 41. The second catalyst layer 42 is a thin film that adheres closely to the electrolyte membrane 20 and promotes the second reaction. For example, the second catalyst layer 42 is formed of carbon carrying a metal material such as platinum (Pt). The material of the second catalyst layer 42 is arbitrary, and a material such as nickel (Ni) may be used. The electrolyte membrane 20 is located between the second catalyst layer 42 and the first catalyst layer 32.

[0019] The second diffusion layer 41 is an element for efficiently separating and discharging the hydrogen gas generated by the second reaction. For example, a porous membrane made of nickel (Ni) foam or a carbon-based material is used as the second diffusion layer 41. The second diffusion layer 41 is also made of a conductive material and functions as a path for electrons exchanged with the second catalyst layer 42.

[0020] The first flow path section 50 is a plate-shaped structure (separator) made of a conductive material such as metal. The anode section 30 is located between the first flow path section 50 and the electrolyte membrane 20. A first groove section 51 is formed on the surface of the first flow path section 50 facing the anode section 30.

[0021] The first groove portion 51 is a flow path that communicates with the anode portion 30. The first groove portion 51 is a flow path formed on the surface of the first flow path portion 50 that faces the anode portion 30. For example, oxygen gas generated in the anode portion 30 by the first reaction flows through the first groove portion 51. The first groove portion 51 also functions as a flow path for flowing the electrolyte solution.

[0022] The second flow path section 60 is a plate-shaped structure (separator) made of a conductive material such as metal. The cathode section 40 is located between the second flow path section 60 and the electrolyte membrane 20. A second groove section 61 is formed on the surface of the second flow path section 60 facing the cathode section 40.

[0023] The second groove portion 61 is a flow path that communicates with the cathode portion 40. The second groove portion 61 is a flow path formed on the surface of the second flow path portion 60 that faces the cathode portion 40. For example, hydrogen gas generated in the cathode portion 40 by the second reaction flows through the second groove portion 61. The second groove portion 61 also functions as a flow path that flows the electrolyte or a cleaning solution, which will be described later.

[0024] 1, the first supply unit 80 is a mechanism for supplying the electrolyte from the storage tank 3 to the first groove portion 51. The first supply unit 80 includes a first supply line 81 and a first supply pump .

[0025] The first supply line 81 is a pipe that connects the storage tank 3 and the first flow path section 50. That is, the first supply line 81 supplies the electrolytic solution from the storage tank 3 to the first groove section 51. The electrolytic solution supplied to the first flow path section 50 flows through the first groove section 51. The first supply line 81 can be made of a resin material (or a metal material) that is highly resistant to the corrosive action of the electrolytic solution.

[0026] The first supply pump 82 is provided midway along the first supply line 81. The first supply pump 82 is a pump that supplies the electrolyte solution sucked from the storage tank 3 to the first flow path section 50 via the first supply line 81.

[0027] Gas-liquid separator 5 is a device that separates and discharges oxygen gas generated by water electrolysis from the electrolytic solution. Gas-liquid separator 6 is a device that separates and discharges hydrogen gas generated by water electrolysis from the electrolytic solution.

[0028] The gas-liquid separator 5 is connected to the first flow path section 50 and the liquid storage tank 3. The gas-liquid separator 5 is a device that separates oxygen gas and electrolyte. The separated oxygen gas is discharged from the gas-liquid separator 5 to the outside via a discharge pipe. The separated electrolyte is sent to the liquid storage tank 3.

[0029] The gas-liquid separator 6 is connected to the second flow path section 60 and the liquid storage tank 3. The gas-liquid separator 6 is a device that separates hydrogen gas and electrolyte. The separated hydrogen gas is discharged from the gas-liquid separator 6 to the outside via a discharge pipe. The separated electrolyte is sent to the liquid storage tank 3.

[0030] Here, the water electrolysis performed in this embodiment will be described.

[0031] The first supply pump 82 supplies the electrolytic solution from the storage tank 3 to the first flow path section 50. The electrolytic solution supplied to the first flow path section 50 flows through the first groove section 51. The electrolytic solution that has flowed through the first groove section 51 passes through the anode section 30 and the electrolyte membrane 20 to reach the cathode section 40. When the power supply device 2 supplies power to the water electrolysis cell 4, oxygen gas is generated in the anode section 30 by the first reaction using the electrolytic solution, and hydrogen gas is generated in the cathode section 40 by the second reaction.

[0032] The electrolyte solution containing oxygen gas produced in the anode section 30 is sent to the gas-liquid separator 5 connected to the first flow path section 50. The electrolyte solution sent to the gas-liquid separator 5 is separated into oxygen gas and electrolyte solution. The separated oxygen gas is discharged from the discharge pipe. The electrolyte solution separated from the oxygen gas is collected in the storage tank 3.

[0033] The hydrogen gas generated in the cathode section 40 is sent to the gas-liquid separator 6 connected to the second flow path section 60. The hydrogen gas is separated into hydrogen gas and electrolytic solution by the gas-liquid separator 6, and the separated hydrogen is discharged from an exhaust pipe.

[0034] In the cathode section 40, water in the electrolyte solution supplied to the cathode section 40 is consumed, so the hydrogen gas generated in the cathode section 40 is hardly contaminated with the electrolyte solution. That is, the electrolyte solution is concentrated in the cathode section 40. The concentration of the electrolyte solution causes deposits to form between the electrolyte membrane 20 and the cathode section 40. Therefore, it is necessary to clean the cathode section 40 as the water electrolysis progresses. The degree of progress of water electrolysis can be determined from the pH of the electrolyte solution. This is because the electrolyte solution collected in the storage tank 3 consumes water, and the pH of the electrolyte solution increases over time as the water electrolysis progresses. Therefore, in the first embodiment, a second supply section 90 is provided to supply a cleaning solution for cleaning the cathode section 40 to the second groove section 61, a pH sensor 7 to measure the pH of the electrolyte solution, and a control system 8 to control cleaning of the cathode section 40 as the water electrolysis progresses.

[0035] The second supply unit 90 is a mechanism that supplies the electrolytic solution from the storage tank 3 to the second groove portion 61. The electrolytic solution supplied from the storage tank 3 to the second groove portion 61 is used as a cleaning solution for cleaning the cathode portion 40. The second supply unit 90 includes a second supply line 91 and a second supply pump 92.

[0036] The second supply line 91 is a pipe that connects the storage tank 3 and the second flow path section 60. That is, the second supply line 91 supplies the electrolytic solution from the storage tank 3 to the second groove section 61. The electrolytic solution supplied to the second flow path section 60 flows into the second groove section 61. The second supply line 91 can be made of a resin material (or a metal material) that is highly resistant to the corrosive action of the electrolytic solution.

[0037] The second supply pump 92 is provided midway along the second supply line 91. The second supply pump 92 is a pump that draws in the electrolytic solution from the storage tank 3 and supplies it as a cleaning solution for cleaning the second flow path section 60.

[0038] The pH sensor 7 is a device that measures the pH of the electrolyte. The pH sensor 7 is installed in the storage tank 3 so as to measure the pH of the electrolyte in the storage tank 3. In the first embodiment, the pH sensor 7 is installed in the storage tank 3, but the installation location of the pH sensor 7 is not limited thereto as long as it can measure the pH of the electrolyte used for water electrolysis. For example, the pH sensor 7 may be installed somewhere in the piping connecting the gas-liquid separator 5 and the storage tank 3, or somewhere in the piping connecting the first flow path section 50 and the gas-liquid separator 5.

[0039] The control system 8 is a system that controls measurement of the pH of the electrolytic solution in water electrolysis and cleaning of the cathode section 40. The control system 8 includes a control device 101 and a storage device 100.

[0040] The control device 101 is composed of one or more processors that control each element of the control system 8. Specifically, the control device 101 is composed of one or more types of processors, such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or an ASIC (Application Specific Integrated Circuit).

[0041] The storage device 100 is one or more memories that store programs executed by the control device 101 and data used by the control device 101. The storage device 100 is configured with a known storage medium such as a magnetic storage medium or a semiconductor storage medium. The storage device 100 may also be configured with a combination of multiple types of storage medium. A portable storage medium that can be attached to and detached from the control system 8 may also be used as the storage device 100.

[0042] 3 is a block diagram illustrating an example of the functional configuration of the control system 8. The control device 101 executes a program stored in the storage device 100 to realize multiple functions (acquisition unit 102, cleaning unit 103) for controlling the control system 8. The control system 8 may be realized as a single device, or may be realized as a collection of multiple devices configured separately from each other.

[0043] The acquiring unit 102 acquires the measured pH value of the electrolyte solution measured by the pH sensor 7. Specifically, for each unit period on the time axis, the acquiring unit 102 calculates the average of multiple measured pH values ​​within the unit period. Note that the acquiring unit 102 may also calculate the maximum value (worst value) of multiple pH values ​​within the unit period.

[0044] The cleaning unit 103 performs cleaning control by controlling the second supply unit 90 to supply a cleaning liquid for cleaning the cathode unit 40 to the second groove unit 61 in accordance with the measured pH value acquired by the acquisition unit 102. The cleaning control is a control that supplies the electrolyte sucked by the second supply pump 92 from the liquid storage tank 3 to the second groove unit 61 via the second supply line 91. Specifically, the cleaning unit 103 compares the measured pH value with a threshold value, and performs cleaning control when the measured pH value exceeds the threshold value. The cathode unit 40 is cleaned by supplying the electrolyte liquid to the second groove unit 61.

[0045] 4 is a flowchart illustrating a specific procedure for processing in parallel with water electrolysis performed by the control system 8. The processing begins when water electrolysis begins.

[0046] When water electrolysis starts, the control device 101 (acquisition unit 102) acquires the measured pH value measured by the pH sensor 7 (Sc1). Acquisition of the measured value is repeated, for example, for each unit period. Specifically, the control device 101 calculates the average of multiple measured pH values ​​within the unit period. The control device 101 may also calculate the maximum value (worst value) of multiple pH values ​​within the unit period.

[0047] When the measurement value is acquired, the control device 101 (cleaning unit 103) determines whether the measurement value exceeds the threshold value (Sc2). If the measurement value does not exceed the threshold value (Sc2: No), the control process proceeds to step Sc1. On the other hand, if the measurement value exceeds the threshold value (Sc2: Yes), cleaning control is performed by controlling the second supply pump 92 (Sc3). That is, the supply amount of cleaning liquid is set so that deposits on the cathode unit 40 are cleaned. The cleaning unit 103 supplies a predetermined amount of cleaning liquid from the storage tank 3 to the second groove portion 61 via the second supply line 91. When the cleaning control ends, the control process proceeds to step Sc1. As described above, the control system 8 can clean the cathode unit 40 in accordance with the progress of water electrolysis.

[0048] FIG. 5 is a plan view of the surface (hereinafter referred to as the "channel forming surface 62") of the second channel section 60 according to this embodiment that faces the cathode section 40. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. In the following description, the X-axis and Y-axis are assumed to be in a plane parallel to the channel forming surface 62. The X-axis and Y-axis are mutually orthogonal. The X-axis is, for example, an axis parallel to the horizontal direction. The Y-axis is, for example, an axis parallel to the vertical direction. The X-axis is an example of a "first axis," and the Y-axis is an example of a "second axis." A direction along the X-axis is referred to as the "X1 direction," and a direction opposite to the X1 direction is referred to as the "X2 direction." The X1 direction is an example of a "first direction," and the X2 direction is an example of a "second direction."

[0049] The second groove portion 61 of this embodiment includes a first portion 63 and a second portion 70 .

[0050] The first portion 63 extends along the X-axis. The first portion 63 includes an inlet portion 64 and an outlet portion 66. The inlet portion 64 and the outlet portion 66 are formed to be spaced apart from each other in the direction of the Y-axis. The inlet portion 64 and the outlet portion 66 are parallel to the direction of the X-axis. The outlet portion 66 is located in the positive direction of the Y-axis relative to the inlet portion 64.

[0051] An inlet 65 is formed at the end of the inlet section 64 in the X1 direction along the X axis. The inlet 65 is an opening for supplying a cleaning liquid to the cathode section 40. As shown in FIG. 1 , the inlet 65 is connected to a second supply line 91. The cleaning liquid is supplied to the inlet 65 through the second supply line 91 from a second supply pump 92 that has sucked in the electrolytic solution in the storage tank 3. The cleaning liquid that has flowed into the inlet 65 is supplied to the second diffusion layer 41 and the second catalyst layer 42, and cleans the cathode section 40.

[0052] 5, the flow path area in the inlet portion 64 decreases in the X2 direction. For example, consider a first position P1 and a second position P2 in the direction of the X axis. The second position P2 is located further in the X1 direction than the first position P1. The flow path area S1 in the inlet portion 64 at the first position P1 is smaller than the flow path area S2 in the inlet portion 64 at the second position P2, which is located further in the X1 direction than the first position P1.

[0053] An outlet 67 is formed at the end of the outflow section 66 in the X2 direction, opposite the X1 direction. The outlet 67 is an opening for discharging hydrogen gas generated by the second reaction and excess electrolyte or cleaning solution. As shown in FIG. 1 , the outlet 67 is connected to the gas-liquid separator 6. The electrolyte or cleaning solution that has passed through the second groove section 61 flows out from the outlet 67 and is sent to the gas-liquid separator 6.

[0054] 5, the flow path area of ​​the outflow portion 66 increases in the X2 direction. Therefore, the flow path area S3 of the outflow portion 66 at a first position P1 is larger than the flow path area S4 of the outflow portion 66 at a second position P2 that is closer to the X1 direction than the first position P1.

[0055] The second portion 70 includes a plurality of connecting portions 71. Each of the connecting portions 71 is a flow path that extends linearly along the Y-axis. The connecting portions 71 are arranged in the X-axis direction at intervals from one another. For example, the connecting portions 71 are arranged in the X-axis direction at equal intervals. Each connecting portion 71 connects the inlet portion 64 and the outlet portion 66. That is, the connecting portions 71 connect the inlet portion 64 and the outlet portion 66 at different positions along the X-axis.

[0056] As described above, the flow path area in the inlet portion 64 decreases in the X2 direction. Therefore, compared to a configuration in which the flow path area of ​​the inlet portion 64 is constant over the entire length in the X-axis direction, the flow rate of the electrolyte flowing from the inlet portion 64 to each of the multiple connecting portions 71 becomes more uniform.

[0057] Similarly, as described above, the flow path area in the outflow portion 66 increases in the X2 direction. Therefore, compared to a configuration in which the flow path area of ​​the outflow portion 66 is constant over the entire length in the X-axis direction, the flow rate of the electrolyte in each of the multiple connecting portions 71 connecting the inflow portion 64 and the outflow portion 66 becomes more uniform. Therefore, the electrolyte can be made to flow evenly in the second groove portion 61, and deposits on the cathode portion 40 can be effectively removed over a wide area.

[0058] 6, the multiple connecting portions 71 all have the same width Wa. The multiple connecting portions 71 are spaced equally apart from one another in the direction along the X axis, and the spacing Wb is the same length as the width of the connecting portion 71. The multiple connecting portions 71 all have the same depth D.

[0059] 5, the inner wall surface of the portion where the first portion 63 and the second portion 70 are connected is rounded. Specifically, in this embodiment, the inner wall surface of the portion where the inlet portion 64 and each of the plurality of connecting portions 71 are connected, and the inner wall surface of the portion where the outlet portion 66 and each of the plurality of connecting portions 71 are connected are rounded. The rounded shape indicates that the portions are connected by a continuous, rounded curved surface (for example, a circular arc surface).

[0060] FIG. 7 is a schematic diagram of the flow of cleaning liquid in a configuration (hereinafter referred to as the "Comparative Example") in which the first surface 68 of the outflow portion 66 and the second surface 72 of the second portion 70 are connected by a discontinuous angular shape. The dashed arrows in FIG. 7 indicate the flow of cleaning liquid. In the Comparative Example, the cleaning liquid flows along the wall surface, separating to form vortices, causing the cleaning liquid to accumulate near the corners. On the other hand, FIG. 8 is a schematic diagram of the flow of cleaning liquid in this embodiment. The dashed arrows in FIG. 8 indicate the flow of cleaning liquid. As described above, in this embodiment, the first surface 68 of the outflow portion 66 and the second surface 72 of the second portion 70 are rounded. In this configuration, the cleaning liquid moves along the rounded wall surface, resulting in less stagnation of cleaning liquid. Therefore, compared to the Comparative Example in which the inner wall surface of the portion where the first portion 63 and the second portion 70 are connected is discontinuous and angular, in this embodiment, stagnation of cleaning liquid flowing through the second groove portion 61 (e.g., a decrease in flow rate) is suppressed. Therefore, deposits from the cathode portion 40 are prevented from remaining in the second groove portion 61.

[0061] B: Modified example Specific modified embodiments that can be added to each of the embodiments exemplified above are exemplified below. Two or more embodiments arbitrarily selected from the following examples may be appropriately combined within a range that does not contradict each other.

[0062] (1) In the first embodiment, the electrolyte in the storage tank 3 is supplied as the cleaning liquid. However, the cleaning liquid is not limited to the electrolyte in the storage tank 3, as long as the cleaning liquid is a liquid that can be used to clean the cathode unit 40. For example, a cleaning liquid prepared in a dedicated tank or a cleaning liquid supplied to the cathode unit 40 from a cleaning liquid supply line may be used. However, a configuration in which the electrolyte in the storage tank 3 is supplied as the cleaning liquid can simplify the configuration of the water electrolysis system 1 compared to a configuration in which a liquid different from the electrolyte used for water electrolysis is supplied as the cleaning liquid. Specifically, this configuration can achieve effects such as reduction in installation space and costs.

[0063] (2) In the first embodiment, the cleaning liquid supplied for cleaning the cathode section 40 is collected in the liquid storage tank 3, but the embodiment is not limited to collecting the cleaning liquid in the liquid storage tank 3. For example, the cleaning liquid may be collected in a dedicated recovery tank, or the cleaning liquid used for cleaning may be discharged to the outside.

[0064] (3) In the first embodiment, a predetermined amount of cleaning liquid is used to clean the cathode 40, but the amount of cleaning liquid used for cleaning is not limited to a fixed value. For example, possible configurations include supplying the cleaning liquid for a predetermined time, continuing the supply of the cleaning liquid until the value measured by the pH sensor 7 falls below a predetermined threshold, and providing another pH sensor 7 in the piping between the outlet 67 and the gas-liquid separator 6, and supplying the cleaning liquid until the difference in pH between the pH sensor 7 installed in the storage tank 3 and the pH sensor 7 installed in the piping between the outlet 67 and the gas-liquid separator 6 reaches a predetermined value.

[0065] (4) In the first embodiment, the grooves of the second portion 70 are straight, but the grooves of the second portion 70 do not have to be straight. For example, they may be wavy.

[0066] (5) In the first embodiment, the inner wall surface of the portion where the inlet portion 64 is connected to each of the multiple connecting portions 71 is rounded. Furthermore, the inner wall surface of the portion where the outlet portion 66 is connected to each of the multiple connecting portions 71 is also rounded. However, as long as the accumulation of cleaning liquid is suppressed, all of the inner wall surfaces of the portion where the inlet portion 64 or the outlet portion 66 is connected to each of the multiple connecting portions 71 do not have to be rounded. For example, a configuration is envisioned in which the inner wall surface of the portion where the inlet portion 64 is connected to the connecting portion 71 located at the end in the X2 direction and the inner wall surface of the portion where the outflow portion 66 is connected to the connecting portion 71 located at the end in the X1 direction are rounded, and the portions where the other connecting portions 71 are connected to the inlet portion 64 or the outflow portion 66 are angular.

[0067] (6) In the first embodiment, the multiple connecting portions 71 are arranged at equal intervals, but the intervals Wb between the multiple connecting portions 71 are not limited to being equal intervals. For example, the intervals Wb between the multiple connecting portions 71 may be narrowed in the X2 direction or may be widened in the X2 direction.

[0068] (7) In the first embodiment, the widths Wa of the multiple connecting portions 71 are the same, but the widths Wa of the multiple connecting portions 71 are not limited to being the same. For example, the widths Wa of the connecting portions 71 may be narrowed in the X2 direction, or may be widened in the X2 direction.

[0069] (8) In the first embodiment, the depths D of the multiple connecting portions 71 are the same, but the depths D of the multiple connecting portions 71 are not limited to being the same. For example, the depths D of the multiple connecting portions 71 may be shallower in the X2 direction, or may be deeper in the X2 direction.

[0070] (9) In the first embodiment, the interval Wb between the multiple connecting portions 71 of the second portion 70 and the width Wa of the multiple connecting portions 71 are the same length, but the interval Wb between the multiple connecting portions 71 of the second portion 70 do not have to be the same as the width Wa of the multiple connecting portions 71. For example, a configuration in which the interval Wb between the multiple connecting portions 71 is wider than the width Wa of the multiple connecting portions 71, or a configuration in which the interval Wb between the multiple connecting portions 71 is narrower than the width Wa of the multiple connecting portions 71, etc. are conceivable.

[0071] (10) The term "nth" (n is a natural number) in this application is used only as a formal and convenient label to distinguish each element in the description and does not have any substantive meaning. Therefore, there is no room for restrictive interpretation of the position of each element or the order of production, etc., based on the term "nth."

[0072] C: Notes From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0073] A water electrolysis system according to one aspect (Aspect 1) of the present disclosure includes a storage tank for storing an electrolytic solution, a membrane electrode assembly including an electrolyte membrane located between an anode and a cathode, a first flow path portion having a first groove formed in a surface facing the anode, a second flow path portion having a second groove formed in a surface facing the cathode, a first supply portion for supplying the electrolytic solution from the storage tank to the first groove, and a second supply portion for supplying a cleaning solution for cleaning the cathode to the second groove, wherein the second groove portion includes a first portion extending along a first axis and a second portion extending along a second axis intersecting the first axis, and the inner wall surface of the portion connecting the first and second portions is rounded. According to the above aspect, water electrolysis is achieved by supplying the electrolytic solution supplied from the storage tank to the first flow path portion to the anode. Meanwhile, the cleaning solution supplied to the second flow path portion also reaches the cathode, separately from the supply of the electrolytic solution to the anode. That is, deposits generated between the electrolyte membrane and the cathode due to the concentration of the electrolyte solution are removed by the cleaning solution supplied through the second groove. Furthermore, the inner wall surface of the portion where the first portion and the second portion are connected is rounded. According to the above embodiment, the cleaning solution moves along the rounded inner wall surface. Therefore, compared to a configuration in which the portion where the first portion and the second portion are connected has a discontinuous angular shape, for example, retention of the cleaning solution (e.g., a decrease in flow rate) at the portion where the first portion and the second portion are connected is suppressed. The cleaning solution is a liquid supplied to the second groove for cleaning the cathode. The cleaning solution is, for example, an electrolyte solution or water. The electrolyte solution is an aqueous solution in which an electrolyte is dissolved, which facilitates water electrolysis. For example, a potassium hydroxide aqueous solution or a sodium hydroxide aqueous solution can be used as the electrolyte solution. However, the type of electrolyte is arbitrary and is not limited to the above examples. The water is either pure water or tap water.

[0074] In a water electrolysis system according to a specific example (Aspect 2) of Aspect 1, the first portion includes an inlet having an inlet formed at an end in a first direction along the first axis, and an outlet having an outlet formed at an end in a second direction opposite to the first direction. The second portion includes a plurality of connecting portions connecting the inlet and the outlet at different positions along the first axis. The inner wall surface of a portion where the inlet is connected to one of the connecting portions located at an end in the second direction is rounded, and the inner wall surface of a portion where the outlet is connected to one of the connecting portions located at an end in the first direction is rounded. According to the above aspect, the cleaning liquid moves along the rounded inner wall surface. Therefore, it is possible to effectively prevent the cleaning liquid from accumulating in the portion. Furthermore, the inner wall surface of a portion where the inlet is connected to the connecting portion located at the end in the first direction is also rounded. Therefore, it is possible to effectively prevent the cleaning liquid from accumulating in the portion.

[0075] In a water electrolysis system according to a specific example of Aspect 2 (Aspect 3), the inner wall surfaces of the portions where the inlet and each of the multiple connecting parts are connected are rounded, and the inner wall surfaces of the portions where the outlet and each of the multiple connecting parts are connected are also rounded. According to the above aspect, the cleaning liquid moves along the rounded inner wall surfaces. Therefore, it is possible to effectively prevent the cleaning liquid from accumulating in these portions. Furthermore, the inner wall surfaces of the portions where the outlet and each of the multiple connecting parts are connected are also rounded. Therefore, it is possible to effectively prevent the cleaning liquid from accumulating in these portions.

[0076] In a water electrolysis system according to a specific example (Aspect 4) of Aspect 2 or Aspect 3, the flow path area in the inlet section decreases in the second direction, and the flow path area in the outlet section increases in the second direction. According to the above aspect, the flow rate of the electrolyte in each of the multiple connecting sections connecting the inlet section and the outlet section approaches uniformity. This allows the electrolyte to flow evenly throughout the second groove section. Because the electrolyte can be flowed evenly throughout the second groove section, deposits on the cathode section can be effectively removed over a wide area.

[0077] In the water electrolysis system according to any one of Aspects 1 to 4 (Aspect 5), the second supply unit supplies the electrolytic solution in the storage tank as the cleaning solution to the second groove portion. This aspect simplifies the configuration of the water electrolysis system compared to a configuration in which a liquid different from the electrolytic solution used for water electrolysis is supplied as the cleaning solution to the second groove portion.

[0078] The water electrolysis system according to any one of the first to fifth embodiments (aspect 6) further includes a pH sensor for measuring the pH of the electrolyte solution, an acquisition unit for acquiring the pH sensor measurement value, and a cleaning unit for controlling the second supply unit to supply a cleaning solution for cleaning the cathode solution to the second flow path unit in accordance with the pH sensor measurement value. According to the above aspects, the cathode solution is automatically cleaned. Therefore, the cathode solution can be efficiently cleaned without requiring user instructions. Control according to the pH sensor measurement value means, for example, control when the pH value of the electrolyte solution reaches a predetermined value, or control that changes in stages according to the pH value of the electrolyte solution. [Explanation of symbols]

[0079] 1...water electrolysis system, 2...power supply, 3...storage tank, 4...water electrolysis cell, 5...gas-liquid separator, 6...gas-liquid separator, 7...pH sensor, 8...control system, 10...membrane electrode assembly, 20...electrolyte membrane, 30...anode portion, 31...first diffusion layer, 32...first catalyst layer, 40...cathode portion, 41...second diffusion layer, 42...second catalyst layer, 50...first flow path portion, 51...first groove portion, 60...second flow path portion, 61...second groove portion, 62...flow path forming surface, 63...first portion, 64...inlet portion, 65...inlet port, 66...outlet portion, 67...outlet port, 68...first surface, 70...second portion, 71...connecting portion, 72 ...second surface, 80...first supply section, 81...first supply line, 82...first supply pump, 90...second supply section, 91...second supply line, 92...second supply pump, 100...storage device, 101...control device, 102...acquisition section, 103...cleaning section, D...depth of connecting section, P1...first position, P2...second position, S1...flow path area of ​​inlet section at first position P1, S2...flow path area of ​​inlet section at second position P2, S3...flow path area of ​​outlet section at first position P1, S4...flow path area of ​​outlet section at second position P2, Wa...width of connecting section, Wb...spacing between connecting sections.

Claims

1. a storage tank for storing an electrolyte; a membrane electrode assembly having an electrolyte membrane located between an anode portion and a cathode portion; a first flow path portion having a first groove portion formed on a surface facing the anode portion; a second flow path portion having a second groove portion formed on a surface facing the cathode portion; a first supply unit that supplies the electrolytic solution from the storage tank to the first groove portion; a second supply unit that supplies a cleaning liquid for cleaning the cathode unit to the second groove unit; Equipped with The second groove portion is a first portion extending along a first axis; a second portion extending along a second axis that intersects the first axis; The inner wall surface of the portion where the first portion and the second portion are connected is rounded. Water electrolysis system.

2. The first portion is an inflow portion having an inflow port formed at an end portion in a first direction along the first axis; an outflow portion having an outflow port formed at an end portion in a second direction opposite to the first direction, The second portion is a plurality of connecting portions that connect the inlet portion and the outlet portion at different positions along the first axis, an inner wall surface of a portion where the inlet portion and a connecting portion located at an end in the second direction among the plurality of connecting portions are connected to each other has an R-shape; An inner wall surface of a portion where the outflow portion and a connecting portion located at an end in the first direction among the plurality of connecting portions are connected is rounded. The water electrolysis system according to claim 1.

3. an inner wall surface of a portion where the inlet portion and each of the plurality of connecting portions are connected is rounded; The inner wall surface of the portion where the outflow portion and each of the plurality of connecting portions are connected is rounded. The water electrolysis system according to claim 2.

4. a flow path area in the inlet portion decreases in the second direction; The flow path area of ​​the outlet portion increases in the second direction. The water electrolysis system according to claim 2 or 3.

5. The second supply unit supplies the electrolyte in the storage tank to the second groove as the cleaning liquid. The water electrolysis system according to any one of claims 1 to 3.

6. A pH sensor is provided to measure the pH of the electrolyte. an acquisition unit that acquires a measurement value of the pH sensor; a cleaning unit that controls the second supply unit to supply a cleaning liquid for cleaning the cathode unit to the second flow path unit according to the measurement value of the pH sensor; The water electrolysis system according to claim 1 , further comprising:

Images