Water electrolysis system

Abstract

To provide a water electrolysis system capable of detecting an abnormal pressure rise even when its pressure sensor fails.SOLUTION: A water electrolysis system measures a hydrogen pressure in a water electrolysis cell, measures a first voltage at a first current in a normal operation of the water electrolysis cell when the hydrogen pressure is in a normal range, calculates a first resistance of the water electrolysis cell from the gradient of the voltage of the water electrolysis cell obtained by sweeping a prescribed current through the water electrolysis cell when the first voltage exceeds a first normal cell voltage threshold at the first current, and determines that the water electrolysis cell is in an abnormal condition when the first resistance is higher than the prescribed resistance threshold and stops the operation of the water electrolysis cell.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Various studies have been conducted on water electrolysis devices. For example, Patent Document 1 discloses a technique for detecting a pressure abnormality using a hydrogen pressure value and stopping hydrogen production. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-087396 Summary of the Invention [Problem to be solved by the invention]

[0004] If the pressure sensor fails, it will not be able to detect the abnormality, and the abnormal pressure will cause the safety device (relief valve) to operate, resulting in the release (exhaust) of the generated hydrogen.

[0005] The present disclosure has been made in view of the above-described circumstances, and has as its main object to provide a water electrolysis system that can detect an abnormality in pressure increase even when a pressure sensor fails. [Means for solving the problem]

[0006] The present disclosure provides a water electrolysis system, comprising: measuring a hydrogen pressure in a water electrolysis cell, and if the hydrogen pressure is within a normal range, measuring a first voltage at a first current during normal operation of the water electrolysis cell; if the first voltage exceeds a first normal cell voltage threshold at the first current, calculating a first resistance of the water electrolysis cell from a slope of the voltage of the water electrolysis cell obtained by sweeping a predetermined current through the water electrolysis cell; When the first resistance is higher than a predetermined resistance threshold, the water electrolysis cell is determined to be abnormal, and operation of the water electrolysis cell is stopped.

[0007] In the present disclosure, when it is determined that the water electrolysis cell has an abnormality, the operation of the water electrolysis cell is not stopped, and a second voltage is measured at a second current of the water electrolysis cell that is smaller than the first current; if the second voltage exceeds a second normal cell voltage threshold at the second current, calculating a second resistance of the water electrolysis cell from a slope of the voltage of the water electrolysis cell obtained by sweeping a predetermined current through the water electrolysis cell; If the second resistance is higher than a predetermined resistance threshold, it may be determined that an abnormality has occurred in the water electrolysis cell, and operation of the water electrolysis cell may be stopped.

[0008] In the present disclosure, the water electrolysis system includes the water electrolysis cell, a controller, a pressure sensor, and a voltage sensor, the pressure sensor measures the hydrogen pressure in the water electrolysis cell; when the control unit determines that the hydrogen pressure is within a normal range, the voltage sensor measures a first voltage at a first current during normal operation of the water electrolysis cell; when the control unit determines that the first voltage exceeds a first normal cell voltage threshold at the first current, the control unit calculates a first resistance of the water electrolysis cell from a slope of the voltage of the water electrolysis cell obtained by sweeping a predetermined current through the water electrolysis cell; When the first resistance is higher than a predetermined resistance threshold, the control unit may determine that an abnormality has occurred in the water electrolysis cell, and may stop operation of the water electrolysis cell. [Effects of the Invention]

[0009] The water electrolysis system of the present disclosure can detect an abnormal pressure increase even when the pressure sensor fails. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 is a schematic diagram illustrating an example of a water electrolysis system according to the present disclosure. [Figure 2] 1 is a flowchart illustrating an example of control of a water electrolysis system according to the present disclosure. [Figure 3] 10 is a flowchart illustrating another example of control of the water electrolysis system according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Embodiments of the present disclosure are described below. Matters necessary for implementing the present disclosure other than those specifically mentioned in this specification (e.g., the general configuration and manufacturing process of a water electrolysis system that do not characterize the present disclosure) can be understood as design matters of a person skilled in the art based on prior art in the relevant field. The present disclosure can be implemented based on the contents disclosed in this specification and common general technical knowledge in the relevant field. In this specification, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. Any combination of upper and lower limits in the numerical range can be adopted.

[0012] The present disclosure provides a water electrolysis system, comprising: measuring a hydrogen pressure in a water electrolysis cell, and if the hydrogen pressure is within a normal range, measuring a first voltage at a first current during normal operation of the water electrolysis cell; if the first voltage exceeds a first normal cell voltage threshold at the first current, calculating a first resistance of the water electrolysis cell from a slope of the voltage of the water electrolysis cell obtained by sweeping a predetermined current through the water electrolysis cell; When the first resistance is higher than a predetermined resistance threshold, the water electrolysis cell is determined to be abnormal, and operation of the water electrolysis cell is stopped.

[0013] When the water electrolysis system of the present disclosure determines that the water electrolysis cell has an abnormality, it may measure a second voltage at a second current lower than the first current of the water electrolysis cell without stopping operation of the water electrolysis cell, and if the second voltage exceeds a second normal cell voltage threshold at the second current, calculate a second resistance of the water electrolysis cell from a slope of the voltage of the water electrolysis cell obtained by sweeping a predetermined current through the water electrolysis cell, and if the second resistance is higher than the predetermined resistance threshold, determine that the water electrolysis cell has an abnormality and stop operation of the water electrolysis cell.

[0014] The present disclosure can provide a method for detecting a pressure abnormality in a water electrolysis cell without using a pressure sensor value when the pressure sensor fails.

[0015] The water electrolysis system according to the present disclosure may include a water electrolysis cell, a controller, a pressure sensor, and a voltage sensor.

[0016] The water electrolysis cell may be a water electrolysis cell stack (hereinafter sometimes referred to as a stack) formed by stacking a plurality of such water electrolysis cells. The number of water electrolysis cells stacked is not particularly limited, and may be, for example, from 2 to several hundred. The water electrolysis cell of the present disclosure electrolyzes water supplied to the anode (oxygen electrode), generating oxygen from the anode and hydrogen from the cathode (hydrogen electrode) as follows. Anode: H2O → 2H + + 1 / 2O2+ 2e - Cathode: 2H + + 2e - → H2 The water electrolysis cell has at least an electrode unit, and may have two separators that sandwich the electrode unit, if necessary. The electrode section includes an anode gas diffusion layer, an anode catalyst layer, an electrolyte membrane, a cathode catalyst layer, and a cathode gas diffusion layer in this order.

[0017] The cathode (hydrogen electrode) includes a cathode catalyst layer and a cathode-side gas diffusion layer. The anode (oxygen electrode) includes an anode catalyst layer and an anode-side gas diffusion layer.

[0018] The cathode catalyst layer and the anode catalyst layer are collectively referred to as catalyst layers. The catalyst layer may include, for example, a catalytic metal that promotes water electrolysis, a proton-conductive electrolyte, and an electron-conductive carrier. Examples of catalyst metals that can be used include iridium (Ir), iridium dioxide (IrO2), ruthenium (Ru), platinum (Pt), and alloys of Pt with other metals (e.g., Pt alloys mixed with cobalt and nickel). The anode catalyst layer may use, for example, Ir, iridium dioxide (IrO2), and Ru as the catalyst metal, and the cathode catalyst layer may use, for example, Pt and Pt alloys as the catalyst metal. The electrolyte may be a fluorine-based resin, etc. As the fluorine-based resin, for example, a Nafion solution may be used. The catalytic metal is supported on a carrier, and in each catalyst layer, the carrier supporting the catalytic metal (catalyst-supported carrier) and the electrolyte may be mixed together. Examples of the carrier for supporting the catalytic metal include carbon materials such as carbon, which are generally available commercially.

[0019] The electrolyte membrane may be a solid polymer electrolyte membrane. Examples of the solid polymer electrolyte membrane include a fluorine-based electrolyte membrane such as a thin film of perfluorosulfonic acid containing water, and a hydrocarbon-based electrolyte membrane. The electrolyte membrane may be, for example, a Nafion membrane (manufactured by DuPont).

[0020] The cathode side gas diffusion layer and the anode side gas diffusion layer are collectively referred to as the gas diffusion layer (GDL). The gas diffusion layer may be a gas-permeable, i.e., porous, electrically conductive member or the like. Examples of the conductive member include porous carbon materials such as carbon cloth and carbon paper, and porous metal materials such as metal mesh and foam metal.

[0021] The anode separator and cathode separator are collectively referred to as separators. The cathode separator is disposed adjacent to the surface of the cathode-side gas diffusion layer opposite to the cathode catalyst layer side. The anode separator is disposed adjacent to the surface of the anode-side gas diffusion layer opposite to the anode catalyst layer side. The two separators, the anode separator and the cathode separator, sandwich the resin frame and the electrode portion. The separator may have holes serving as manifolds, such as supply holes and discharge holes, for circulating fluids such as reaction water, oxygen, hydrogen, and a cooling medium in the stacking direction of the water electrolysis cells. The reaction water and the cooling medium may be water, pure water, or the like. The supply holes include an anode supply hole, a cathode supply hole, and a coolant supply hole. Examples of the exhaust holes include an anode exhaust hole, a cathode exhaust hole, and a coolant exhaust hole. The separator may have flow paths for reaction fluids such as reaction water, oxygen, hydrogen, etc. on the surface in contact with the gas diffusion layer. The separator may also have flow paths for a cooling medium for maintaining a constant temperature of the water electrolysis cell on the surface opposite to the surface in contact with the gas diffusion layer. The anode separator may have a flow path for anode fluid such as reaction water, oxygen, etc. on the surface in contact with the anode-side gas diffusion layer. The anode separator may also have a flow path for a cooling medium for maintaining a constant temperature of the water electrolysis cell on the surface opposite to the surface in contact with the anode-side gas diffusion layer. The cathode separator may have a flow path for a cathode fluid such as hydrogen on the surface in contact with the cathode-side gas diffusion layer, and may have a flow path for a cooling medium for maintaining a constant temperature of the water electrolysis cell on the surface opposite to the surface in contact with the cathode-side gas diffusion layer. The separator may be a gas-impermeable conductive material, etc. Examples of the gas-impermeable conductive material include dense carbon made gas-impermeable by compressing a resin material such as a thermosetting resin, a thermoplastic resin, or a resin fiber, and a carbon material such as a carbon powder or a carbon fiber, and a press-molded metal (e.g., titanium, stainless steel, etc.) plate. The shape of the separator may be rectangular, horizontally elongated hexagonal, horizontally elongated octagonal, circular, oval, or the like.

[0022] The water electrolysis cell may typically have a resin frame. The resin frame is disposed around the outer periphery of the electrode unit and is disposed between the cathode separator and the anode separator. The resin frame may have a skeleton, an opening, and a hole. The skeleton is the main part of the resin frame that is connected to the electrode parts. The opening is a holding area for the electrode unit, and is an area that penetrates a part of the skeleton to accommodate the electrode unit. The opening may be located in the resin frame at a position where the skeleton is disposed around (the outer periphery of) the electrode unit, or may be located in the center of the resin frame. The holes in the resin frame allow fluids such as reaction water, oxygen, hydrogen, and a cooling medium to circulate in the stacking direction of the water electrolysis cells. The holes in the resin frame may be aligned with the holes in the separators so as to communicate with each other. The resin frame may include a frame-shaped core layer and two frame-shaped shell layers, that is, a first shell layer and a second shell layer, provided on both sides of the core layer. The first and second shell layers may be provided in a frame shape on both sides of the core layer, similarly to the core layer.

[0023] The core layer may be a structural member having gas sealing and insulating properties, and may be formed of a material whose structure does not change even under the temperature conditions of thermocompression bonding in the manufacturing process of the water electrolysis cell. Specifically, the core layer may be made of a resin such as polyethylene, polypropylene, PC (polycarbonate), PPS (polyphenylene sulfide), PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PA (polyamide), PI (polyimide), PS (polystyrene), PPE (polyphenylene ether), PEEK (polyether ether ketone), cycloolefin, PES (polyethersulfone), PPSU (polyphenylsulfone), LCP (liquid crystal polymer), or epoxy resin. The core layer may also be made of a rubber material such as EPDM (ethylene propylene diene rubber), fluororubber, or silicone rubber. The thickness of the core layer may be 5 μm or more, or 20 μm or more, from the viewpoint of ensuring insulation, and may be 200 μm or less, or 150 μm or less, from the viewpoint of reducing the thickness of the water electrolysis cell.

[0024] The first and second shell layers may have properties such as high adhesiveness to other substances, softening under the temperature conditions during thermocompression bonding, and lower viscosity and melting point than the core layer in order to bond the core layer to the anode separator and the cathode separator and ensure sealing. Specifically, the first and second shell layers may be made of a thermoplastic resin such as a polyester or modified olefin resin, or a thermosetting resin such as a modified epoxy resin. The resin constituting the first shell layer and the resin constituting the second shell layer may be the same type of resin or different types of resin. By providing shell layers on both sides of the core layer, bonding between the resin frame and the two separators by hot pressing becomes easier. The thickness of each of the first shell layer and the second shell layer may be 5 μm or more, or 30 μm or more, from the viewpoint of ensuring adhesiveness, and may be 100 μm or less, or 40 μm or less, from the viewpoint of reducing the thickness of the water electrolysis cell.

[0025] In the resin frame, the first shell layer and the second shell layer may be provided only in the portions that bond to the anode separator and the cathode separator, respectively. The first shell layer provided on one surface of the core layer may be bonded to the cathode separator. The second shell layer provided on the other surface of the core layer may be bonded to the anode separator. The resin frame may then be sandwiched between a pair of separators.

[0026] The water electrolysis cell stack may include a gasket or a resin sheet disposed between each of the water electrolysis cells to surround each hole and ensure gas sealing.

[0027] The water electrolysis cell stack may have manifolds such as an inlet manifold to which the supply holes communicate and an outlet manifold to which the discharge holes communicate. Examples of the inlet manifold include an anode inlet manifold, a cathode inlet manifold, and a coolant inlet manifold. Examples of the outlet manifold include an anode outlet manifold, a cathode outlet manifold, and a coolant outlet manifold.

[0028] The pressure sensor is disposed on a hydrogen extraction flow path, which will be described later, and measures the hydrogen pressure in the water electrolysis cell. The pressure sensor is electrically connected to the control unit, which detects the hydrogen pressure obtained by the pressure sensor. The pressure sensor may be a conventionally known pressure gauge or the like.

[0029] The voltage sensor measures the voltage of the electrolysis cell. In the case of a water electrolysis cell stack, the voltage sensor measures the voltage of each water electrolysis cell. Because the voltage of the water electrolysis cell stack is the average value of the voltages of each water electrolysis cell, measuring only the voltage of the water electrolysis cell stack may not detect abnormalities in each water electrolysis cell, so the voltage of each water electrolysis cell is measured. The voltage sensor is electrically connected to the control unit, which detects the voltage of the water electrolysis cell obtained by the voltage sensor. The voltage sensor may be a conventionally known voltmeter, etc. The voltage sensor may have voltage measurement terminals and wiring connected to each water electrolysis cell.

[0030] The control unit may include a current control device that controls the current flowing through the water electrolysis cell. The control unit controls the operation of the water electrolysis cell. The control unit physically includes, for example, a processing unit such as a CPU (Central Processing Unit), a storage device such as a ROM (Read Only Memory) that stores control programs and control data processed by the CPU, a RAM (Random Access Memory) that is used mainly as various work areas for control processing, and an input / output interface. The control unit may also be, for example, a control device such as an Electronic Control Unit (ECU).

[0031] The control unit may execute the following first control. When the control unit determines that the hydrogen pressure is within the normal range, the control unit causes the current control device to pass a first current to the water electrolysis cell during normal operation of the water electrolysis cell. The voltage sensor measures a first voltage at the first current during normal operation of the water electrolysis cell. When the control unit determines that the first voltage exceeds a first normal cell voltage threshold for the first current, the control unit causes the current control device to sweep a predetermined current through the water electrolysis cell and calculates a first resistance of the water electrolysis cell from the slope of the obtained voltage of the water electrolysis cell. If the first resistance is higher than a predetermined resistance threshold, the control unit determines that an abnormality has occurred in the water electrolysis cell, and stops operation of the water electrolysis cell.

[0032] The control unit may execute the second control described below. If the first resistance is higher than a predetermined resistance threshold and the control unit determines that the water electrolysis cell is abnormal, the control unit does not stop operation of the water electrolysis cell, but instead causes the current control device to pass a second current smaller than the first current through the water electrolysis cell. The voltage sensor measures a second voltage at the second current of the water electrolysis cell. If the control unit determines that the second voltage exceeds a second normal cell voltage threshold at the second current, the control unit causes the current control device to sweep a predetermined current through the water electrolysis cell and calculates a second resistance of the water electrolysis cell from the slope of the obtained voltage of the water electrolysis cell. If the second resistance is higher than the predetermined resistance threshold, the control unit determines that the water electrolysis cell is abnormal and stops operation of the water electrolysis cell.

[0033] The water electrolysis system may have a water system, a hydrogen system, and an oxygen-containing gas system.

[0034] The water system may have a water supply section, a water supply flow path, a water discharge flow path, and the like. The water supply unit may be a water storage tank that stores water, pure water, or the like. The water supply passage connects the water supply unit to the oxygen electrode of the water electrolysis cell. The water supply unit supplies water, pure water, etc. to the oxygen electrode of the water electrolysis cell via the water supply passage. The water discharge flow path may be connected to the water electrolysis cell and may discharge unreacted water, etc. discharged from the water electrolysis cell to the outside of the water electrolysis system, or may be connected to the water electrolysis cell and a water supply unit and may recover unreacted water, etc. discharged from the water electrolysis cell to the water supply unit.

[0035] The hydrogen system may include a hydrogen storage tank, a hydrogen extraction flow path, the above-mentioned pressure sensor (hydrogen pressure sensor), a hydrogen relief valve, and the like. The hydrogen storage tank stores the hydrogen generated by water electrolysis. The hydrogen extraction flow path may connect the hydrogen storage tank and the hydrogen electrode of the water electrolysis cell, and hydrogen discharged from the hydrogen electrode by water electrolysis in the water electrolysis cell may be stored in the hydrogen storage tank. The hydrogen relief valve is disposed on the hydrogen extraction flow path, and opens when an abnormality is detected to discharge hydrogen outside the water electrolysis system. The hydrogen relief valve is electrically connected to a control unit, which controls the opening and closing of the hydrogen relief valve.

[0036] The oxygen-containing gas system may include an oxygen discharge channel and the like. The oxygen discharge flow path may be connected to the oxygen electrode of the water electrolysis cell, and may discharge an oxygen-containing gas discharged from the oxygen electrode due to water electrolysis in the water electrolysis cell to the outside of the water electrolysis system. The oxygen-containing gas may be oxygen, air, etc. The water discharge flow path may also serve as the oxygen discharge flow path.

[0037] 1 is a schematic diagram illustrating an example of a water electrolysis system according to the present disclosure. However, the water electrolysis system according to the present disclosure is not limited to the configuration shown in FIG. 1 includes a stack, a current control device provided in a control unit, a voltage sensor, a water system, and a hydrogen system. For convenience, descriptions of other components such as an oxygen-containing gas system are omitted. The water system has a water supply flow path that supplies pure water to the stack and a water discharge flow path that discharges pure water from the stack. The hydrogen system has a hydrogen extraction flow path, a hydrogen pressure sensor disposed on the hydrogen extraction flow path, and a hydrogen relief valve. In the stack, voltage measurement terminals of a voltage sensor are attached to each electrolysis cell via wiring so that the voltage of each electrolysis cell can be measured. A current control device controls the current in the stack. The voltage of each electrolysis cell measured by the voltage sensor is stored in the control unit.

[0038] (First embodiment) FIG. 2 is a flowchart showing an example of control of the water electrolysis system of the present disclosure. 1. The pressure sensor measures the hydrogen pressure in the water electrolysis cell stack, and the control unit determines whether the hydrogen pressure is within the normal range. If the hydrogen pressure is abnormal, the control unit takes appropriate measures (abnormality measures), such as stopping water electrolysis. 2. If the control unit determines that the hydrogen pressure value is within the normal range, the control unit causes the current control device to supply a first current corresponding to normal operation of the water electrolysis cells, measures a first voltage of each water electrolysis cell using the voltage sensor, and compares the measured voltage with a first normal cell voltage threshold to determine whether a voltage increase has occurred, i.e., whether the first voltage is equal to or less than the first normal cell voltage threshold. 3. If the control unit determines that the first voltage exceeds the first normal cell voltage threshold, i.e., that the cell voltage is abnormal, the control unit sweeps a predetermined current through the electrolysis cell using the current control device and calculates a first resistance of the electrolysis cell from the slope of the resulting voltage of the electrolysis cell. The control unit determines whether the first resistance is equal to or less than the predetermined resistance threshold. If the first resistance is higher than the predetermined resistance threshold, the control unit determines that the electrolysis cell is abnormal, and as an abnormality response, the control unit stops operation of the electrolysis cell. If the first resistance is equal to or less than the predetermined resistance threshold, the control unit continues operation of the water electrolysis cell.

[0039] (Second embodiment) FIG. 3 is a flowchart showing another example of control of a water electrolysis system according to the present disclosure. 1. The pressure sensor measures the hydrogen pressure in the water electrolysis cell stack, and the control unit determines whether the hydrogen pressure is within the normal range. If the hydrogen pressure is abnormal, the control unit takes appropriate measures (abnormality measures), such as stopping water electrolysis. 2. If the control unit determines that the hydrogen pressure value is within the normal range, the control unit causes the current control device to supply a first current corresponding to normal operation of the water electrolysis cells, and measures a first voltage of each water electrolysis cell using the voltage sensor. The control unit compares the first voltage with a first normal cell voltage threshold to determine whether a voltage rise has occurred, i.e., whether the first voltage is equal to or less than the first normal cell voltage threshold. 3. If the control unit determines that the first voltage exceeds the first normal cell voltage threshold, the control unit causes the current control device to supply a second current smaller than the first current (first current > second current) to the water electrolysis cells, measures the second voltage of each water electrolysis cell using the voltage sensor, and compares the second voltage with the second normal cell voltage threshold to determine whether the second voltage is equal to or less than the second normal cell voltage threshold. 4. If the control unit determines that the second voltage exceeds the second normal cell voltage threshold, the control unit sweeps a predetermined current through the electrolysis cell using the current control device, and calculates a second resistance of the electrolysis cell from the slope of the resulting voltage of the electrolysis cell. The control unit determines whether the second resistance is equal to or less than the predetermined resistance threshold. If the second resistance is higher than the predetermined resistance threshold, the control unit determines that the electrolysis cell is abnormal, and as a measure to deal with the abnormality, the control unit stops operation of the electrolysis cell. If the second resistance is equal to or less than the predetermined resistance threshold, the control unit continues operation of the water electrolysis cell. In the first embodiment, the first voltage is measured at a first current during normal operation of the water electrolysis cell, which may result in an increase in resistance due to overvoltage, etc. In the second embodiment, after measuring the first voltage, the second voltage is measured at a second current that is smaller than the first current and is less affected by resistance, which improves the accuracy of detecting an abnormality in resistance. The second current is not particularly limited as long as it is a current smaller than the first current.

[0040] The first normal cell voltage threshold and the second normal cell voltage threshold are collectively referred to as the normal cell voltage threshold (sometimes simply referred to as the voltage threshold). The normal cell voltage threshold may be the voltage when the water electrolysis cell reaches the operating hydrogen pressure after startup, or may be a voltage value obtained by performing a current sweep to check the resistance of the water electrolysis cell and determining that the resistance is within a normal range when a voltage increase is observed, etc. Because the temperature of the water electrolysis cell is low during startup and the temperature of the water electrolysis cell is elevated after the current sweep compared to the temperature at startup, the normal cell voltage threshold may be appropriately reset in accordance with the state of the water electrolysis cell.

[0041] The resistance threshold may be the lower design limit of the cell. In the event of a pressure abnormality, the separator of the water electrolysis cell is deformed, which increases the contact resistance within the water electrolysis cell. If the pressure inside the water electrolysis cell exceeds the normal operating range, the hydrogen pressure inside the water electrolysis cell causes the separator to deform in the direction of expanding as the water electrolysis cell moves, for example, into the shape of a dorayaki pancake. This weakens the load pressing the separator against the GDL, increasing the contact resistance between them, and in water electrolysis where a constant current is flowing, the voltage rises to maintain the current. Therefore, even if the pressure sensor fails, it is possible to determine whether or not there is an abnormality by calculating the resistance of the water electrolysis cell.

Claims

1. A water electrolysis system, measuring a hydrogen pressure in the water electrolysis cell, and if the hydrogen pressure is within a normal range, measuring a first voltage at a first current during normal operation of the water electrolysis cell; if the first voltage exceeds a first normal cell voltage threshold at the first current, calculating a first resistance of the water electrolysis cell from a slope of the voltage of the water electrolysis cell obtained by sweeping a predetermined current through the water electrolysis cell; When the first resistance is higher than a predetermined resistance threshold, the water electrolysis cell is determined to be abnormal, and operation of the water electrolysis cell is stopped.

2. If the first voltage exceeds the first normal cell voltage threshold, the first resistance is not calculated, and a second voltage at a second current smaller than the first current of the water electrolysis cell is measured; if the second voltage exceeds a second normal cell voltage threshold at the second current, calculating a second resistance of the water electrolysis cell from a slope of the voltage of the water electrolysis cell obtained by sweeping a predetermined current through the water electrolysis cell; The water electrolysis system according to claim 1 , wherein, when the second resistance is higher than a predetermined resistance threshold, it is determined that an abnormality has occurred in the water electrolysis cell, and operation of the water electrolysis cell is stopped.

3. the water electrolysis system includes the water electrolysis cell, a controller, a pressure sensor, and a voltage sensor; the pressure sensor measures the hydrogen pressure in the water electrolysis cell; when the control unit determines that the hydrogen pressure is within a normal range, the voltage sensor measures a first voltage at a first current during normal operation of the water electrolysis cell; when the control unit determines that the first voltage exceeds a first normal cell voltage threshold at the first current, the control unit calculates a first resistance of the water electrolysis cell from a slope of the voltage of the water electrolysis cell obtained by sweeping a predetermined current through the water electrolysis cell; The water electrolysis system according to claim 1 , wherein when the first resistance is higher than a predetermined resistance threshold, the controller determines that an abnormality has occurred in the water electrolysis cell and stops operation of the water electrolysis cell.

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