Water electrolysis system, and differential pressure adjustment method of water electrolytic cell in water electrolysis system

Abstract

To perform a differential pressure adjustment of a water electrolytic cell with high responsiveness in the water electrolytic cell by quickly detecting pressure fluctuations of hydrogen and oxygen.SOLUTION: A water electrolysis system comprises: a water electrolytic cell which comprises a cathode, an anode, and an ion-exchange membrane arranged between the cathode and the anode, generates hydrogen and hydroxide ions from an electrolyte which is supplied to a cathode chamber arranged between the cathode and the ion-exchange membrane, and also generates oxygen from an electrolyte which is supplied to an anode chamber arranged between the anode and the ion-exchange membrane, and the hydroxide ions which have passed through the ion-exchange membrane; a differential pressure detection unit which detects a differential pressure between the cathode chamber and the anode chamber; and a differential pressure adjustment unit which adjusts the differential pressure between the cathode chamber and the anode chamber on the basis of the differential pressure detected by the differential pressure detection unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a water electrolysis system and a method for adjusting a differential pressure of a water electrolysis cell in the water electrolysis system. [Background technology]

[0002] Patent Document 1 discloses a water electrolysis device that electrolyzes pure water in a water electrolysis cell that uses a solid polymer electrolyte membrane as a cation exchange membrane. In this water electrolysis device, electrolysis produces a mixture of hydrogen and pure water in the cathode chamber of the water electrolysis cell, and a mixture of oxygen and pure water in the anode chamber. In a water electrolysis device that uses a solid polymer electrolyte membrane, it is necessary to keep the pressure difference between the cathode chamber and the anode chamber separated by the solid polymer electrolyte membrane small to prevent damage to the solid polymer electrolyte membrane. Therefore, the water electrolysis device disclosed in Patent Document 1 detects the pressures of hydrogen and oxygen with a pressure gauge and adjusts the pressures of hydrogen and oxygen to predetermined pressures by controlling the aperture of a pressure control valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-84042 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the water electrolysis apparatus described in Patent Document 1, a pressure gauge and a pressure control valve are respectively provided downstream of a cathode-side gas-liquid separator that separates a mixture of hydrogen and pure water into hydrogen gas and pure water, and an anode-side gas-liquid separator that separates a mixture of oxygen and pure water into oxygen gas and pure water. This results in a large time lag between when hydrogen and oxygen pressure fluctuations occur in the cathode chamber and the anode chamber of the water electrolysis apparatus and when the pressure fluctuations are detected by the pressure gauges provided downstream of the cathode-side gas-liquid separator and the anode-side gas-liquid separator. As a result, there is a problem of poor responsiveness between when the pressure gauges detect the pressure fluctuations of hydrogen and oxygen and when they adjust the differential pressure of the water electrolysis cells.

[0005] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a water electrolysis system that can quickly detect pressure fluctuations of hydrogen and oxygen and adjust the pressure difference across the water electrolysis cell with high responsiveness, and a method for adjusting the pressure difference across the water electrolysis cell in the water electrolysis system. [Means for solving the problem]

[0006] In order to solve the above problems, the water electrolysis system according to the present disclosure includes a water electrolysis cell including a cathode, an anode, and an ion exchange membrane disposed between the cathode and the anode, wherein the water electrolysis cell generates hydrogen and hydroxide ions from an electrolytic solution supplied to a cathode chamber between the cathode and the ion exchange membrane, and generates oxygen from the electrolytic solution supplied to an anode chamber between the anode and the ion exchange membrane and from the hydroxide ions that have passed through the ion exchange membrane; a differential pressure detection unit that detects a differential pressure between the cathode chamber and the anode chamber; and a differential pressure adjustment unit that adjusts the differential pressure between the cathode chamber and the anode chamber based on the differential pressure detected by the differential pressure detection unit.

[0007] A method for adjusting a differential pressure of a water electrolysis cell in a water electrolysis system according to the present disclosure includes the steps of detecting a differential pressure between the cathode chamber and the anode chamber, and adjusting the differential pressure between the cathode chamber and the anode chamber based on the detected differential pressure. [Effects of the Invention]

[0008] The water electrolysis system and the method for adjusting the differential pressure of a water electrolysis cell in the water electrolysis system disclosed herein enable rapid detection of fluctuations in hydrogen and oxygen pressure, and enable highly responsive adjustment of the differential pressure of the water electrolysis cell. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a configuration of a water electrolysis system according to a first embodiment of the present disclosure. [Figure 2] FIG. 1 is a cross-sectional view schematically illustrating a configuration of a water electrolysis cell of a water electrolysis system according to an embodiment of the present disclosure. [Figure 3] 1 is a flowchart illustrating an example of a procedure for a method for adjusting a differential pressure of a water electrolysis cell in a water electrolysis system according to an embodiment of the present disclosure. [Figure 4] FIG. 10 is a diagram showing an example of the relationship between a change in the differential pressure of the water electrolysis cell and the aperture of the cathode-side gas flow control valve when the differential pressure of the water electrolysis cell is adjusted in the water electrolysis system according to the first embodiment of the present disclosure. [Figure 5] FIG. 10 is a diagram showing the configuration of a water electrolysis system according to a second embodiment of the present disclosure. [Figure 6] FIG. 10 is a diagram showing an example of the relationship between a change in the differential pressure of the water electrolysis cell and the aperture of the cathode-side electrolyte flow control valve when the differential pressure of the water electrolysis cell is adjusted in the water electrolysis system according to the second embodiment of the present disclosure. [Figure 7] FIG. 10 is a diagram showing the configuration of a water electrolysis system according to a third embodiment of the present disclosure. [Figure 8] FIG. 11 is a diagram showing an example of the relationship between the change in the differential pressure of the water electrolysis cell and the rotation speed of the cathode pump when the differential pressure of the water electrolysis cell is adjusted in the water electrolysis system according to the third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of a water electrolysis system and a method for adjusting a differential pressure of a water electrolysis cell in a water electrolysis system according to the present disclosure will be described with reference to the accompanying drawings. However, the present disclosure is not limited to these embodiments. (Configuration of water electrolysis system) As shown in FIG. 1, a water electrolysis system 1A includes at least a water electrolysis cell 2, a cathode-side gas-liquid separator 3A, an anode-side gas-liquid separator 3B, a differential pressure detection unit 5, and a differential pressure adjustment unit 6A.

[0011] (Configuration of water electrolysis cell) The water electrolysis cell 2 is, for example, a device that generates hydrogen by electrolyzing water contained in an electrolyte. The water electrolysis cell 2 is, for example, an anion exchange membrane (AEM) type electrolysis device. As shown in Fig. 2, the water electrolysis cell 2 includes a first separator 21, a second separator 22, an ion exchange membrane 23, a cathode catalyst layer 24, a cathode current collector 25, an anode catalyst layer 26, and an anode current collector 27.

[0012] The first separator 21 and the second separator 22 are arranged with a predetermined gap between them. An internal space S of the water electrolysis cell 2 is formed between the first separator 21 and the second separator 22, and includes a cathode chamber Sa and an anode chamber Sb, which will be described later. The first separator 21 is a member that defines one side of the internal space S of the water electrolysis cell 2. The first separator 21 has, for example, a rectangular plate shape and is made of a metal member. The first separator 21 has a first surface 21a that faces the cathode chamber Sa, which will be described later. A negative voltage is applied to the first separator 21 from, for example, a DC power supply 30.

[0013] The second separator 22 is a member that defines the other surface of the internal space S. The second separator 22 is, for example, a rectangular plate and is formed of a metal member. The second separator 22 has a second surface 22a that faces the anode chamber Sb, which will be described later. A positive voltage is applied to the second separator 22 from the DC power supply 30. As a result, a voltage with a predetermined potential difference is applied to the internal space S between the first separator 21 and the second separator 22. The first separator 21 and the second separator 22 form an electrolytic cell of the water electrolysis cell 2 as a pair of separators.

[0014] figure 2 As shown in FIG. 1, the lower end of the first separator 21 is connected to a cathode-side gas-liquid separator 3A (described later) via a supply line 101A, and the upper end of the first separator 21 is connected to the cathode-side gas-liquid separator 3A via a discharge line 102A.

[0015] A lower end of the second separator 22 is connected to an anode-side gas-liquid separator 3B (described later) via a supply line 101B. An upper end of the second separator 22 is connected to the anode-side gas-liquid separator 3B via a discharge line 102B.

[0016] As shown in FIG. 2 , the ion exchange membrane 23 is a membrane that selectively transmits ions. The ion exchange membrane 23 is, for example, a solid polymer electrolyte membrane. The ion exchange membrane 23 is, for example, an anion exchange membrane (AEM) that is hydroxide ion conductive. However, the ion exchange membrane 23 is not limited to the above example and may be an ion exchange membrane of a type different from the above example. The ion exchange membrane 23 is, for example, in the form of a rectangular sheet. The ion exchange membrane 23 is disposed between the first separator 21 and the second separator 22 and is located in the above-mentioned internal space S. In the internal space S, a cathode chamber Sa is formed between the ion exchange membrane 23 and the first surface 21 a of the first separator 21. In the internal space S, an anode chamber Sb is formed between the ion exchange membrane 23 and the second surface 22 a of the second separator 22.

[0017] The cathode catalyst layer 24 is a layer that promotes the chemical reaction in the cathode chamber Sa. The cathode catalyst layer 24 is, for example, in the form of a rectangular sheet. The cathode catalyst layer 24 is disposed on the cathode chamber Sa side of the ion exchange membrane 23. A negative voltage is applied to the cathode catalyst layer 24 from the DC power supply 30 via the first separator 21 and the cathode power supply 25. The cathode catalyst layer 24 may be made of any material that promotes the chemical reaction in the cathode chamber Sa, and various materials can be used.

[0018] The cathode current collector 25 is an electrical connection part that transmits the voltage applied to the first separator 21 to the cathode catalyst layer 24. The cathode current collector 25 is disposed in the cathode chamber Sa. The cathode current collector 25 is sandwiched between the first surface 21a of the first separator 21 and the cathode catalyst layer 24. The cathode current collector 25 has a structure that allows the electrolyte (water contained therein) and gas to pass through. The cathode current collector 25 is formed, for example, from a metal mesh structure, a sintered body (porous body), or fiber. In the present disclosure, the cathode catalyst layer 24 and the cathode current collector 25 form the cathode 20A of the water electrolysis cell 2.

[0019] The anode catalyst layer 26 is a layer that promotes chemical reactions in the anode chamber Sb. The anode catalyst layer 26 is, for example, in the form of a rectangular sheet. The anode catalyst layer 26 is disposed on the anode chamber Sb side of the ion exchange membrane 23. A positive voltage is applied to the anode catalyst layer 26 from the DC power supply 30 via the second separator 22 and the anode power supply 27. The anode catalyst layer 26 may be made of any material that promotes chemical reactions in the anode chamber Sb, and various materials can be used.

[0020] The anode current collector 27 is an electrical connection part that transmits the voltage applied to the second separator 22 to the anode catalyst layer 26. The anode current collector 27 is disposed in the anode chamber Sb. The anode current collector 27 is sandwiched between the second surface 22a of the second separator 22 and the anode catalyst layer 26. The anode current collector 27 has a structure that allows the electrolyte (water contained therein) and gas to pass through. The anode current collector 27 is formed, for example, from a metal mesh structure, a sintered body (porous body), or fiber. In the present disclosure, the anode catalyst layer 26 and the anode current collector 27 form the anode 20B of the water electrolysis cell 2. The water electrolysis cell 2 may be a unit having a plurality of the above-described configurations.

[0021] (Chemical reactions in water electrolysis cells) As shown in FIG. 1, the cathode chamber Sa is supplied with the electrolytic solution Es from the liquid phase of the cathode-side gas-liquid separator 3A via a supply line 101A. The electrolytic solution Es is, for example, pure water or an alkaline aqueous solution. In the present disclosure, an aqueous potassium hydroxide (KOH) solution is used as the alkaline aqueous solution. That is, the electrolytic solution Es contains potassium hydroxide and water (H2O). In the cathode chamber Sa, when a voltage is applied from a DC power supply 30, hydrogen (H2) and hydroxide ions (OH) are produced from the electrolytic solution Es according to the following formula (1): - ) is generated. 2H2O+2e - →H2+2OH - …(1) The hydroxide ions produced in the cathode chamber Sa move from the cathode chamber Sa to the anode chamber Sb through the ion exchange membrane 23. The hydrogen (hydrogen gas) produced in the cathode chamber Sa is returned to the liquid phase of the cathode-side gas-liquid separator 3A via the discharge line 102A together with the remaining electrolytic solution Es.

[0022] A potassium hydroxide (KOH) aqueous solution is supplied as the electrolyte Es from the liquid phase of the anode-side gas-liquid separator 3B to the anode chamber Sb via a supply line 101B. When a voltage is applied from a DC power supply 30, hydroxide ions that have migrated from the cathode chamber Sa to the anode chamber Sb undergo a chemical reaction to produce oxygen (O2) and water (HO), as shown in the following formula (2): 2OH - →1 / 2O2+H2O+2e - …(2) In the water electrolysis cell 2, a chemical reaction such as that shown in the following formula (3) occurs based on the above formulas (1) and (2). H2O → H2 + 1 / 2O2…(3) The oxygen (oxygen gas) produced in the anode chamber Sb is returned to the liquid phase of the anode-side gas-liquid separator 3B via the discharge line 102B together with the remaining electrolytic solution Es.

[0023] (Gas-liquid separator configuration) The cathode-side gas-liquid separator 3A stores the electrolytic solution Es. The cathode-side gas-liquid separator 3A separates the hydrogen gas produced in the cathode chamber Sa from the electrolytic solution Es. The mixture of the hydrogen gas and the electrolytic solution Es produced in the cathode chamber Sa is sent to the cathode-side gas-liquid separator 3A via a discharge line 102A. In the liquid phase of the cathode-side gas-liquid separator 3A, the gaseous hydrogen gas is separated from the liquid electrolytic solution Es. The hydrogen gas separated in the cathode-side gas-liquid separator 3A is sent to a hydrogen recovery unit (not shown) via a recovery line 103A. Meanwhile, the electrolytic solution Es separated in the cathode-side gas-liquid separator 3A is sent to the water electrolysis cell 2 via a supply line 101A by a cathode-side pump 4A. The cathode-side gas-liquid separator 3A is replenished with the electrolytic solution Es from an electrolyte supply unit (not shown) as needed.

[0024] The anode-side gas-liquid separator 3B stores the electrolytic solution Es. The anode-side gas-liquid separator 3B separates the oxygen gas generated in the anode chamber Sb from the electrolytic solution Es. A mixture of the oxygen gas and the electrolytic solution Es generated in the anode chamber Sb is sent to the anode-side gas-liquid separator 3B via a discharge line 102B. In the liquid phase of the anode-side gas-liquid separator 3B, the gaseous oxygen gas is separated from the liquid electrolytic solution Es. The oxygen gas separated in the anode-side gas-liquid separator 3B is sent to an oxygen recovery unit (not shown) via a recovery line 103B. Meanwhile, the electrolytic solution Es separated in the anode-side gas-liquid separator 3B is sent to the water electrolysis cell 2 via a supply line 101B by an anode-side pump 4B. The anode-side gas-liquid separator 3B is replenished with the electrolytic solution Es from an electrolyte supply unit (not shown) as needed.

[0025] (Configuration of differential pressure detection unit) The differential pressure detection unit 5 detects the differential pressure between the cathode chamber Sa and the anode chamber Sb of the water electrolysis cell 2. In an embodiment of the present disclosure, the differential pressure detection unit 5 detects the differential pressure between the cathode-side electrolyte and the anode-side electrolyte at the inlet side of the water electrolysis cell 2. That is, the differential pressure detection unit 5 detects the differential pressure between the vicinity of the inlet to the water electrolysis cell 2 in the supply line 101A and the vicinity of the inlet to the water electrolysis cell 2 in the supply line 101B. The differential pressure detection unit 5 may also detect the differential pressure between the cathode-side electrolyte and the anode-side electrolyte at the outlet side of the water electrolysis cell 2.

[0026] (Configuration of differential pressure adjustment unit) The differential pressure adjustment unit 6A adjusts the differential pressure between the cathode chamber Sa and the anode chamber Sb based on the differential pressure detected by the differential pressure detection unit 5. In the embodiment of the present disclosure, the differential pressure adjustment unit 6A includes a cathode-side gas flow rate adjustment valve 7A, an anode-side gas flow rate adjustment valve 7B, and a differential pressure control unit 60.

[0027] The cathode-side gas flow rate control valve 7A is configured to be able to adjust the flow rate of hydrogen gas delivered from the cathode-side gas-liquid separator 3A. The cathode-side gas flow rate control valve 7A is provided in the recovery line 103A. The cathode-side gas flow rate control valve 7A adjusts the flow rate of hydrogen gas delivered from the cathode-side gas-liquid separator 3A by opening and closing the flow path in the recovery line 103A.

[0028] The anode-side gas flow rate control valve 7B is configured to be able to adjust the flow rate of oxygen gas delivered from the anode-side gas-liquid separator 3B. The anode-side gas flow rate control valve 7B is provided in the recovery line 103B. The anode-side gas flow rate control valve 7B adjusts the flow rate of oxygen gas delivered from the anode-side gas-liquid separator 3B by opening and closing the flow path in the recovery line 103B.

[0029] The differential pressure control unit 60 is a computer equipped with a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc. The differential pressure control unit 60 adjusts the differential pressure between the cathode chamber Sa and the anode chamber Sb when the differential pressure detected by the differential pressure detection unit 5 reaches a preset threshold. In the embodiment of the present disclosure, the differential pressure control unit 60 adjusts the aperture of at least one of the cathode-side gas flow control valve 7A and the anode-side gas flow control valve 7B when the differential pressure detected by the differential pressure detection unit 5 reaches a preset threshold.

[0030] In the water electrolysis cell 2, hydrogen (H) and oxygen (O) are produced from water (HO). Because hydrogen is produced in greater amounts in terms of molar ratio, the hydrogen pressure in the cathode chamber Sa tends to be higher than the oxygen pressure in the anode chamber Sb. Therefore, in an embodiment of the present disclosure, when the differential pressure detected by the differential pressure detection unit 5 reaches an upper threshold value within a preset range, the differential pressure control unit 60 adjusts the aperture of at least one of the cathode-side gas flow control valve 7A and the anode-side gas flow control valve 7B so that the aperture of the cathode-side gas flow control valve 7A is greater than the aperture of the anode-side gas flow control valve 7B. Specifically, for example, the differential pressure control unit 60 may increase the aperture of both the cathode-side gas flow control valve 7A and the anode-side gas flow control valve 7B so that the aperture of the cathode-side gas flow control valve 7A is greater than the aperture of the anode-side gas flow control valve 7B. Furthermore, for example, the differential pressure control unit 60 may increase the aperture of the cathode-side gas flow rate adjustment valve 7A while keeping the aperture of the anode-side gas flow rate adjustment valve 7B fixed. The differential pressure control unit 60 may terminate the adjustment of the differential pressure between the cathode chamber Sa and the anode chamber Sb as described above when the differential pressure detected by the differential pressure detection unit 5 reaches the lower limit threshold of a preset range.

[0031] (Procedure for adjusting the differential pressure of water electrolysis cells in a water electrolysis system) As shown in FIG. 3 , the method for adjusting the differential pressure of a water electrolysis cell in a water electrolysis system according to an embodiment of the present disclosure includes step S11 of detecting the differential pressure, step S12 of determining whether the differential pressure has reached an upper threshold value, step S13 of adjusting the differential pressure, step S14 of checking the differential pressure, and step S15 of terminating the adjustment of the differential pressure.

[0032] In step S11 of detecting the differential pressure, the differential pressure detector 5 detects the differential pressure between the cathode chamber Sa and the anode chamber Sb of the water electrolysis cell 2 every time a preset time interval elapses.

[0033] In step S12, which determines whether the differential pressure has reached the upper threshold, the differential pressure control unit 60 determines whether the differential pressure detected by the differential pressure detection unit 5 has reached the upper threshold of a preset range. As a result, if the differential pressure detected by the differential pressure detection unit 5 has not reached the preset upper threshold (step S12: No), the process returns to step S11, and detection of the differential pressure between the cathode chamber Sa and the anode chamber Sb is repeated every time a preset time interval elapses. On the other hand, if the differential pressure detected by the differential pressure detection unit 5 has reached the preset upper threshold (step S12: Yes), the process proceeds to step S13.

[0034] In step S13 of adjusting the differential pressure, the differential pressure control unit 60 adjusts the aperture of at least one of the cathode-side gas flow control valve 7A and the anode-side gas flow control valve 7B. In an embodiment of the present disclosure, the differential pressure control unit 60 increases the aperture of the cathode-side gas flow control valve 7A by a preset aperture width while keeping the aperture of the anode-side gas flow control valve 7B fixed. This allows the water electrolysis system 1A As a result, the pressure of the hydrogen gas decreases, and the pressure difference between the cathode chamber Sa and the anode chamber Sb in the water electrolysis cell 2 decreases.

[0035] In step S14, the differential pressure is confirmed after step S13, in which the differential pressure is adjusted, and a preset time has elapsed. In step S14, the differential pressure is detected by the differential pressure detection unit 5. In step S14, the differential pressure is determined to determine whether the differential pressure between the cathode chamber Sa and the anode chamber Sb has reached a lower limit threshold of a preset range as a result of adjusting the differential pressure in step S13. If the differential pressure detected by the differential pressure detection unit 5 has not decreased to the preset lower limit threshold (step S14: No), step S13 continues. On the other hand, if the differential pressure detected by the differential pressure detection unit 5 has decreased to the preset lower limit threshold (step S14: Yes), the process proceeds to step S15.

[0036] In step S15, which ends the adjustment of the differential pressure, the implementation of step S13, which adjusts the differential pressure, is terminated. That is, the adjustment of the aperture of at least one of the cathode-side gas flow control valve 7A and the anode-side gas flow control valve 7B, which was performed in step S13, which adjusts the differential pressure, is terminated. In an embodiment of the present disclosure, the aperture of the cathode-side gas flow control valve 7A, which had been increased by a preset aperture width, is returned to its original aperture, while the aperture of the anode-side gas flow control valve 7B is kept fixed.

[0037] FIG. 4 shows an example of the method for adjusting the pressure difference between the water electrolysis cells in the water electrolysis system described above, in which the aperture of the anode-side gas flow control valve 7B is adjusted in accordance with the pressure difference between the cathode chamber Sa and the anode chamber Sb. As shown in Fig. 4, at time T1 when the pressure difference between the cathode chamber Sa and the anode chamber Sb reaches an upper threshold P1, the aperture of the anode-side gas flow control valve 7B is increased, thereby decreasing the pressure difference between the cathode chamber Sa and the anode chamber Sb. Thereafter, the increased aperture of the anode-side gas flow control valve 7B is maintained, thereby continuing to decrease the pressure difference between the cathode chamber Sa and the anode chamber Sb. At time T2 when the pressure difference between the cathode chamber Sa and the anode chamber Sb reaches a lower threshold P2, the aperture of the anode-side gas flow control valve 7B is returned to its original aperture. In this embodiment of the present disclosure, the lower threshold P2 is set to a negative value. That is, the lower threshold P2 is set so that the pressure in the cathode chamber Sa is lower than the pressure in the anode chamber Sb. As a result, even if the change (increase) in pressure in the cathode chamber Sa due to hydrogen gas becomes larger than the change (increase) in pressure in the anode chamber Sb due to oxygen gas after step S15, which ends the adjustment of the differential pressure, the time required for the differential pressure to reach the upper threshold value P1 can be extended. The upper threshold P1 and the lower threshold P2 are set so that the ion exchange membrane 23 is not damaged.

[0038] (Action and effect) In the water electrolysis system 1A configured as described above, the differential pressure detection unit 5 directly detects the differential pressure between the cathode chamber Sa and the anode chamber Sb of the water electrolysis cell 2. When the differential pressure detection unit 5 detects a change in the differential pressure, the differential pressure adjustment unit 6A can immediately adjust the differential pressure between the cathode chamber Sa and the anode chamber Sb based on the detected differential pressure. As a result, pressure fluctuations of hydrogen and oxygen can be quickly detected, and the differential pressure adjustment of the water electrolysis cell 2 can be performed with high responsiveness.

[0039] Furthermore, the differential pressure adjustment unit 6A adjusts the aperture of at least one of the cathode-side gas flow control valve 7A and the anode-side gas flow control valve 7B based on the differential pressure detected by the differential pressure detection unit 5. This makes it possible to easily adjust the differential pressure of the water electrolysis cell 2 in accordance with the differential pressure detected by the differential pressure detection unit 5.

[0040] Furthermore, the differential pressure control unit 60 adjusts the differential pressure between the cathode chamber Sa and the anode chamber Sb when the differential pressure of the water electrolysis cell 2 reaches a preset threshold value. This allows the differential pressure of the water electrolysis cell 2 to be automatically adjusted based on the detected differential pressure.

[0041] The method for adjusting the pressure difference between the water electrolysis cell 2 in the water electrolysis system 1A of the above embodiment detects the pressure difference between the cathode chamber Sa and the anode chamber Sb, and adjusts the pressure difference between the cathode chamber Sa and the anode chamber Sb based on the detected pressure difference. This configuration enables rapid detection of pressure fluctuations of hydrogen and oxygen, and enables highly responsive adjustment of the pressure difference in the water electrolysis cell 2.

[0042] Second Embodiment Next, a second embodiment of a water electrolysis system and a method for adjusting a differential pressure of a water electrolysis cell in a water electrolysis system according to the present disclosure will be described. In the second embodiment described below, components common to the first embodiment are denoted by the same reference numerals in the drawings, and descriptions thereof will be omitted. The second embodiment differs from the first embodiment in that a cathode-side electrolyte flow control valve 8A and an anode-side electrolyte flow control valve 8B are provided as a differential pressure adjustment unit 6B.

[0043] As shown in FIG. 5, the water electrolysis system 1B includes at least a water electrolysis cell 2, a cathode-side gas-liquid separator 3A, an anode-side gas-liquid separator 3B, a differential pressure detection unit 5, and a differential pressure adjustment unit 6B.

[0044] (Configuration of differential pressure adjustment unit) The differential pressure adjustment unit 6B adjusts the differential pressure between the cathode chamber Sa and the anode chamber Sb based on the differential pressure detected by the differential pressure detection unit 5. In the embodiment of the present disclosure, the differential pressure adjustment unit 6B includes a cathode-side electrolyte flow control valve 8A, an anode-side electrolyte flow control valve 8B, and a differential pressure control unit 60.

[0045] The cathode-side electrolyte flow control valve 8A is configured to adjust the flow rate of the hydrogen-containing electrolyte Es delivered from the cathode chamber Sa. The cathode-side electrolyte flow control valve 8A is provided in the discharge line 102A. The cathode-side electrolyte flow control valve 8A adjusts the flow rate of the hydrogen gas delivered from the cathode chamber Sa by opening and closing the flow path in the discharge line 102A.

[0046] The anode-side electrolyte flow control valve 8B is configured to adjust the flow rate of the oxygen-containing electrolyte Es delivered from the anode chamber Sb. The anode-side electrolyte flow control valve 8B is provided in the discharge line 102B. The anode-side electrolyte flow control valve 8B adjusts the flow rate of the oxygen gas delivered from the anode chamber Sb by opening and closing the flow path in the discharge line 102B.

[0047] The differential pressure control unit 60 adjusts the differential pressure between the cathode chamber Sa and the anode chamber Sb when the differential pressure detected by the differential pressure detection unit 5 reaches a preset threshold, in the same manner as in the method for adjusting the differential pressure of the water electrolysis cell in the water electrolysis system described in the first embodiment (see FIG. 3 ). The differential pressure control unit 60 in the embodiment of the present disclosure adjusts the aperture of at least one of the cathode side electrolyte flow control valve 8A and the anode side electrolyte flow control valve 8B when the differential pressure detected by the differential pressure detection unit 5 reaches a preset threshold.

[0048] When the differential pressure detected by the differential pressure detection unit 5 reaches an upper limit threshold P1 of a preset range, the differential pressure control unit 60 adjusts the aperture of at least one of the cathode side electrolyte flow control valve 8A and the anode side electrolyte flow control valve 8B so that the aperture of the cathode side electrolyte flow control valve 8A is greater than the aperture of the anode side electrolyte flow control valve 8B. Specifically, for example, the differential pressure control unit 60 may increase the aperture of both the cathode side electrolyte flow control valve 8A and the anode side electrolyte flow control valve 8B so that the aperture of the cathode side electrolyte flow control valve 8A is greater than the aperture of the anode side electrolyte flow control valve 8B. Alternatively, for example, the differential pressure control unit 60 may increase the aperture of the cathode side electrolyte flow control valve 8A while keeping the aperture of the anode side electrolyte flow control valve 8B fixed. The differential pressure control unit 60 may terminate the adjustment of the differential pressure between the cathode chamber Sa and the anode chamber Sb as described above when the differential pressure detected by the differential pressure detection unit 5 reaches the lower limit threshold P2 of a preset range.

[0049] FIG. 6 shows an example of the method for adjusting the pressure difference between the water electrolysis cells in the water electrolysis system described above, in which the aperture of the anode-side electrolyte flow control valve 8B is adjusted in accordance with the pressure difference between the cathode chamber Sa and the anode chamber Sb. 6, at time T1 when the pressure difference between the cathode chamber Sa and the anode chamber Sb reaches an upper threshold P1, the aperture of the anode-side electrolyte flow control valve 8B is increased, thereby decreasing the pressure difference between the cathode chamber Sa and the anode chamber Sb. Thereafter, the increased aperture of the anode-side electrolyte flow control valve 8B is maintained, thereby continuing to decrease the pressure difference between the cathode chamber Sa and the anode chamber Sb. At time T2' when the pressure difference between the cathode chamber Sa and the anode chamber Sb reaches a lower threshold P2, the aperture of the anode-side electrolyte flow control valve 8B is returned to its original aperture. The cathode side electrolyte flow control valve 8A and the anode side electrolyte flow control valve 8B are disposed closer to the water electrolysis cell 2 than the cathode side gas flow control valve 7A and the anode side gas flow control valve 7B. Therefore, when the aperture of the anode side electrolyte flow control valve 8B is increased at time T1 when the pressure difference between the cathode chamber Sa and the anode chamber Sb reaches the upper threshold P1, the responsiveness of the anode side electrolyte flow control valve 8B to the decrease in the pressure difference between the cathode chamber Sa and the anode chamber Sb after the aperture of the anode side electrolyte flow control valve 8B is increased is improved compared to the first embodiment. Therefore, in Fig. 6, the time interval from time T1 when the upper threshold P1 is reached to time T2' when the lower threshold P2 is reached is shortened.

[0050] (Action and effect) The water electrolysis system 1B and the method for adjusting the pressure difference in the water electrolysis cell 2 in the water electrolysis system 1B configured as described above enable rapid detection of fluctuations in the hydrogen and oxygen pressures and highly responsive adjustment of the pressure difference in the water electrolysis cell 2, as in the first embodiment.

[0051] Furthermore, the differential pressure adjustment unit 6B adjusts the aperture of at least one of the cathode side electrolyte flow control valve 8A and the anode side electrolyte flow control valve 8B based on the differential pressure detected by the differential pressure detection unit 5. Compared to the configuration in which the cathode side gas flow control valve 7A and the anode side gas flow control valve 7B are used to adjust the differential pressure of the water electrolysis cell 2 as in the first embodiment, the differential pressure adjustment of the water electrolysis cell 2 can be performed at a position closer to the water electrolysis cell 2. Therefore, the differential pressure adjustment of the water electrolysis cell 2 can be performed with high responsiveness.

[0052] (Third embodiment) Next, a third embodiment of a water electrolysis system and a method for adjusting a differential pressure of a water electrolysis cell in a water electrolysis system according to the present disclosure will be described. In the third embodiment described below, components common to the first embodiment will be denoted by the same reference numerals in the drawings, and description thereof will be omitted. The third embodiment differs from the first and second embodiments in that a cathode pump 4A and an anode pump 4B are used as a differential pressure adjustment unit 6C.

[0053] As shown in FIG. 7, a water electrolysis system 1C includes at least a water electrolysis cell 2, a cathode-side gas-liquid separator 3A, an anode-side gas-liquid separator 3B, a differential pressure detection unit 5, and a differential pressure adjustment unit 6C.

[0054] (Configuration of differential pressure adjustment unit) The differential pressure adjustment unit 6C adjusts the differential pressure between the cathode chamber Sa and the anode chamber Sb based on the differential pressure detected by the differential pressure detection unit 5. In the embodiment of the present disclosure, the differential pressure adjustment unit 6C includes a cathode-side pump 4A, an anode-side pump 4B, and a differential pressure control unit 60.

[0055] The cathode-side pump 4A feeds the electrolytic solution Es from the cathode-side gas-liquid separator 3A to the water electrolysis cell 2. The cathode-side pump 4A is provided on the supply line 101A. The cathode-side pump 4A can adjust the flow rate of the electrolytic solution Es fed to the water electrolysis cell 2 by adjusting its rotation speed.

[0056] The anode-side pump 4B feeds the electrolyte solution Es from the anode-side gas-liquid separator 3B to the water electrolysis cell 2. The anode-side pump 4B is provided on the supply line 101B. The anode-side pump 4B can adjust the flow rate of the electrolyte solution Es fed to the water electrolysis cell 2 by adjusting its rotation speed.

[0057] The differential pressure control unit 60 adjusts the differential pressure between the cathode chamber Sa and the anode chamber Sb when the differential pressure detected by the differential pressure detection unit 5 reaches a preset threshold, in the same manner as in the method for adjusting the differential pressure of the water electrolysis cell in the water electrolysis system described in the first embodiment (see FIG. 3). The differential pressure control unit 60 in the embodiment of the present disclosure adjusts the rotation speed of at least one of the cathode side pump 4A and the anode side pump 4B when the differential pressure detected by the differential pressure detection unit 5 reaches a preset threshold.

[0058] When the differential pressure detected by the differential pressure detection unit 5 reaches an upper limit threshold P1 of a preset range, the differential pressure control unit 60 adjusts the rotation speed of at least one of the cathode side pump 4A and the anode side pump 4B so that the rotation speed of the anode side pump 4B is higher than the rotation speed of the cathode side pump 4A. 4B Alternatively, the rotation speeds of both the cathode pump 4A and the anode pump 4B may be increased so that the rotation speed of the cathode pump 4A is higher than the rotation speed of the cathode pump 4A. Alternatively, for example, the differential pressure control unit 60 may increase the rotation speed of the anode pump 4B while keeping the rotation speed of the cathode pump 4A fixed. When the rotation speed of the anode pump 4B is higher than the rotation speed of the cathode pump 4A, the pressure loss in the supply line 101B becomes greater than the pressure loss in the supply line 101A. This increases the flow rate of the electrolyte supplied to the cathode side of the water electrolysis cell 2. This reduces the pressure difference between the cathode chamber Sa and the anode chamber Sb of the water electrolysis cell 2.

[0059] The differential pressure control unit 60 may terminate the adjustment of the differential pressure between the cathode chamber Sa and the anode chamber Sb as described above when the differential pressure detected by the differential pressure detection unit 5 reaches the lower limit threshold P2 of a preset range.

[0060] FIG. 8 shows an example of the method for adjusting the pressure difference between the water electrolysis cells in the water electrolysis system described above, in which the rotation speed of the anode-side pump 4B is adjusted in accordance with the pressure difference between the cathode chamber Sa and the anode chamber Sb. As shown in FIG. 8, at time T1 when the pressure difference between the cathode chamber Sa and the anode chamber Sb reaches an upper threshold P1, the rotation speed of the anode-side pump 4B is increased, thereby decreasing the pressure difference between the cathode chamber Sa and the anode chamber Sb. Thereafter, the increased rotation speed of the anode-side pump 4B is maintained, thereby continuing to decrease the pressure difference between the cathode chamber Sa and the anode chamber Sb. At time T2″ when the pressure difference between the cathode chamber Sa and the anode chamber Sb reaches a lower threshold P2, the rotation speed of the anode-side pump 4B is returned to the original rotation speed.

[0061] By providing the cathode pump 4A and the anode pump 4B as the differential pressure adjustment unit 6C, it is not necessary to provide the cathode-side electrolyte flow control valve 8A and the anode-side electrolyte flow control valve 8B as the differential pressure adjustment unit 6B as in the second embodiment, which prevents an increase in the number of parts and costs of the water electrolysis system 1C. Furthermore, by providing the cathode side pump 4A and the anode side pump 4B, they are disposed closer to the water electrolysis cell 2 than the cathode side gas flow control valve 7A and the anode side gas flow control valve 7B. Therefore, when the rotation speed of the anode side pump 4B is increased at time T1 when the pressure difference between the cathode chamber Sa and the anode chamber Sb reaches the upper limit threshold P1, Compared to the first embodiment, The response when the differential pressure between the cathode chamber Sa and the anode chamber Sb decreases is improved. Therefore, in FIG. 8, the time interval from the time T1 when the upper threshold value P1 is reached to the time T2″ when the lower threshold value P2 is reached may be shortened.

[0062] (Action and effect) The water electrolysis system 1C and the method for adjusting the pressure difference in the water electrolysis cell 2 in the water electrolysis system 1C configured as described above enable rapid detection of fluctuations in the hydrogen and oxygen pressures and highly responsive adjustment of the pressure difference in the water electrolysis cell 2, as in the first embodiment.

[0063] Furthermore, the differential pressure adjustment unit 6C adjusts the rotation speed of at least one of the cathode pump 4A and the anode pump 4B based on the differential pressure detected by the differential pressure detection unit 5. Compared to a configuration in which the cathode gas flow control valve 7A and the anode gas flow control valve 7B adjust the differential pressure of the water electrolysis cell 2, the differential pressure adjustment of the water electrolysis cell 2 can be performed at a position closer to the water electrolysis cell 2. Therefore, the differential pressure adjustment of the water electrolysis cell 2 can be performed with high responsiveness.

[0064] (Other embodiments) The above describes in detail the embodiments of the present disclosure with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present disclosure. In the above embodiment, the procedure for adjusting the pressure difference of the water electrolysis cell 2 in the water electrolysis systems 1A to 1C has been described, but the procedure, threshold values ​​used for determination, etc. can be changed as appropriate. Furthermore, although the above embodiment has been described with reference to an example of the configuration of the water electrolysis cell 2, the configuration of the water electrolysis cell 2 can be modified as appropriate.

[0065] A program for implementing all or part of the functions of the method for adjusting the differential pressure of the water electrolysis cell 2 in the water electrolysis systems 1A to 1C may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed to perform processing by each functional unit. The term "computer system" as used herein includes hardware such as an OS and peripheral devices. In addition, if a WWW system is used, the term "computer system" also includes a website provision environment (or display environment). The term "computer-readable recording medium" refers to portable media such as CDs, DVDs, and USBs, as well as storage devices such as hard disks built into the computer system. When the program is distributed to the differential pressure control unit 60 via a communication line, the differential pressure control unit 60 may load the program into storage and execute the processing. The program may be for implementing part of the functions described above, or may be capable of implementing the functions described above in combination with a program already stored in the computer system.

[0066] <Additional Notes> The water electrolysis systems 1A to 1C described in the respective embodiments and the method for adjusting the pressure difference of the water electrolysis cells 2 in the water electrolysis systems 1A to 1C can be understood, for example, as follows.

[0067] (1) Each of water electrolysis systems 1A to 1C according to a first aspect includes a cathode 20A, an anode 20B, and an ion exchange membrane 23 disposed between the cathode 20A and the anode 20B. The water electrolysis cell 2 generates hydrogen and hydroxide ions from an electrolytic solution Es supplied to a cathode chamber Sa between the cathode 20A and the ion exchange membrane 23, and generates oxygen from the electrolytic solution Es supplied to an anode chamber Sb between the anode 20B and the ion exchange membrane 23 and the hydroxide ions that have passed through the ion exchange membrane 23; a differential pressure detection unit 5 detecting a differential pressure between the cathode chamber Sa and the anode chamber Sb; and differential pressure adjustment units 6A to 6C adjusting the differential pressure between the cathode chamber Sa and the anode chamber Sb based on the differential pressure detected by the differential pressure detection unit 5.

[0068] In the water electrolysis systems 1A to 1C, the differential pressure detection unit 5 directly detects the differential pressure between the cathode chamber Sa and the anode chamber Sb of the water electrolysis cell 2. When the differential pressure detection unit 5 detects a change in the differential pressure, the differential pressure adjustment units 6A to 6C can immediately adjust the differential pressure between the cathode chamber Sa and the anode chamber Sb based on the detected differential pressure. As a result, pressure fluctuations of hydrogen and oxygen can be quickly detected, and the differential pressure adjustment of the water electrolysis cell 2 can be performed with high responsiveness.

[0069] (2) The water electrolysis system 1A according to a second aspect relates to the water electrolysis system 1A of (1), further including: a cathode-side gas-liquid separator 3A that separates hydrogen gas generated in the cathode chamber Sa from the electrolytic solution Es into gas and liquid; and an anode-side gas-liquid separator 3B that separates oxygen gas generated in the anode chamber Sb into gas and liquid from the electrolytic solution Es. The differential pressure adjustment unit 6A adjusts the aperture of at least one of a cathode-side gas flow control valve 7A that adjusts the flow rate of hydrogen gas delivered from the cathode-side gas-liquid separator 3A and an anode-side gas flow control valve 7B that adjusts the flow rate of oxygen gas delivered from the anode-side gas-liquid separator 3B, based on the differential pressure detected by the differential pressure detection unit 5.

[0070] With this configuration, the differential pressure adjustment unit 6A adjusts the aperture of at least one of the cathode-side gas flow control valve 7A and the anode-side gas flow control valve 7B based on the differential pressure detected by the differential pressure detection unit 5, thereby enabling adjustment of the differential pressure in the water electrolysis cell 2.

[0071] (3) A water electrolysis system 1B according to a third aspect is the water electrolysis system 1B according to (1), wherein the differential pressure adjustment unit 6B adjusts, based on the differential pressure detected by the differential pressure detection unit 5, an aperture of at least one of a cathode-side electrolyte flow control valve 8A that adjusts the flow rate of the hydrogen-containing electrolyte solution Es delivered from the cathode chamber Sa and an anode-side electrolyte flow control valve 8B that adjusts the flow rate of the oxygen-containing electrolyte solution Es delivered from the anode chamber Sb.

[0072] With this configuration, the differential pressure adjustment unit 6B adjusts the aperture of at least one of the cathode-side electrolyte flow control valve 8A and the anode-side electrolyte flow control valve 8B based on the differential pressure detected by the differential pressure detection unit 5. Compared to a configuration in which the cathode-side gas flow control valve 7A and the anode-side gas flow control valve 7B adjust the differential pressure of the water electrolysis cell 2, this configuration allows the differential pressure adjustment of the water electrolysis cell 2 to be performed at a position closer to the water electrolysis cell 2. Therefore, the differential pressure adjustment of the water electrolysis cell 2 can be performed with high responsiveness.

[0073] (4) A water electrolysis system 1C according to a fourth aspect is the water electrolysis system 1C according to (1), wherein the differential pressure adjustment unit 6C adjusts the rotation speed of at least one of the cathode-side pump 4A that supplies the electrolytic solution Es from the cathode-side gas-liquid separator 3A to the cathode chamber Sa and the anode-side pump 4B that supplies the electrolytic solution Es from the anode-side gas-liquid separator 3B to the anode chamber Sb, based on the differential pressure detected by the differential pressure detection unit 5.

[0074] With this configuration, the differential pressure adjustment unit 6C adjusts the rotation speed of at least one of the cathode pump 4A and the anode pump 4B based on the differential pressure detected by the differential pressure detection unit 5. Compared to a configuration in which the cathode gas flow control valve 7A and the anode gas flow control valve 7B adjust the differential pressure of the water electrolysis cell 2, this configuration allows the differential pressure adjustment of the water electrolysis cell 2 to be performed at a position closer to the water electrolysis cell 2. Therefore, the differential pressure adjustment of the water electrolysis cell 2 can be performed with high responsiveness.

[0075] (5) The water electrolysis systems 1A to 1C according to a fifth aspect are any one of the water electrolysis systems 1A to 1C described in (1) to (4), wherein the differential pressure adjustment units 6A to 6C further include a differential pressure control unit 60 that adjusts the differential pressure between the cathode chamber Sa and the anode chamber Sb when the differential pressure detected by the differential pressure detection unit 5 reaches a preset threshold.

[0076] According to this configuration, when the differential pressure reaches a preset threshold value, the differential pressure control unit 60 adjusts the differential pressure between the cathode chamber Sa and the anode chamber Sb, thereby automatically adjusting the differential pressure in the water electrolysis cell 2.

[0077] (6) A method for adjusting the pressure difference in the water electrolysis cell 2 in the water electrolysis systems 1A to 1C according to a sixth aspect is a method for adjusting the pressure difference in the water electrolysis cell 2 in any one of the water electrolysis systems 1A to 1C according to (1) to (5), comprising: step S11 of detecting the pressure difference between the cathode chamber Sa and the anode chamber Sb; and step S13 of adjusting the pressure difference between the cathode chamber Sa and the anode chamber Sb based on the detected pressure difference.

[0078] This configuration allows for rapid detection of fluctuations in the hydrogen and oxygen pressures, and allows for highly responsive adjustment of the pressure difference in the water electrolysis cell 2. [Explanation of symbols]

[0079] 1A~1C...Water electrolysis system 2…Water electrolysis cell 3A…Cathode side gas-liquid separator 3B…Anode side gas-liquid separator 4A: Cathode pump 4B...Anode side pump 5...Differential pressure detection section 6A~6C...Differential pressure adjustment section 7A: Cathode gas flow control valve 7B...Anode side gas flow control valve 8A: Cathode side electrolyte flow control valve 8B...Anode side electrolyte flow rate adjustment valve 20A…Cathode 20B…Anode 21...First separator 21a…front page 22...Second separator 22a…Second side 23...Ion exchange membrane 24...Cathode catalyst layer 25...Cathode power supply 26...Anode catalyst layer 27...Anode power supply 30…DC power supply 60...Differential pressure control section 101A, 101B...supply lines 102A, 102B...Discharge lines 103A, 103B...recovery lines Es…electrolyte S…interior space Sa…Cathode chamber Sb…Anode chamber

Claims

1. a water electrolysis cell comprising a cathode, an anode, and an ion exchange membrane disposed between the cathode and the anode, wherein hydrogen and hydroxide ions are produced from an electrolytic solution supplied to a cathode chamber between the cathode and the ion exchange membrane, and oxygen is produced from the electrolytic solution supplied to an anode chamber between the anode and the ion exchange membrane and from the hydroxide ions that have passed through the ion exchange membrane; a differential pressure detection unit that detects a differential pressure between the cathode chamber and the anode chamber; a differential pressure adjustment unit that adjusts the differential pressure between the cathode chamber and the anode chamber based on the differential pressure detected by the differential pressure detection unit.

2. a cathode-side gas-liquid separator that separates the hydrogen gas generated in the cathode chamber from the electrolytic solution; an anode-side gas-liquid separator that separates the oxygen gas generated in the anode chamber from the electrolytic solution, The differential pressure adjustment unit is a cathode-side gas flow rate control valve for adjusting the flow rate of hydrogen gas delivered from the cathode-side gas-liquid separator; and an anode-side gas flow rate control valve that adjusts the flow rate of oxygen gas delivered from the anode-side gas-liquid separator, and the opening degree of at least one of the valves is adjusted based on the differential pressure detected by the differential pressure detection unit. The water electrolysis system according to claim 1 .

3. The differential pressure adjustment unit is a cathode-side electrolyte flow rate control valve for controlling the flow rate of the hydrogen-containing electrolyte discharged from the cathode chamber; and an anode-side electrolyte flow rate regulating valve that regulates the flow rate of the oxygen-containing electrolyte delivered from the anode chamber, and the opening degree of at least one of the valves is adjusted based on the differential pressure detected by the differential pressure detecting unit. The water electrolysis system according to claim 1 .

4. a cathode-side gas-liquid separator that separates the hydrogen gas generated in the cathode chamber from the electrolytic solution; an anode-side gas-liquid separator that separates the oxygen gas generated in the anode chamber from the electrolytic solution, The differential pressure adjustment unit is a cathode-side pump for supplying the electrolytic solution from the cathode-side gas-liquid separator to the cathode chamber; and an anode-side pump that supplies the electrolytic solution from the anode-side gas-liquid separator to the anode chamber, the rotation speed of at least one of the anode-side pump and the anode-side pump is adjusted based on the differential pressure detected by the differential pressure detection unit. The water electrolysis system according to claim 1 .

5. The differential pressure adjustment unit is a differential pressure control unit that adjusts the differential pressure between the cathode chamber and the anode chamber when the differential pressure detected by the differential pressure detection unit reaches a preset threshold value. The water electrolysis system according to claim 1 or 2.

6. A method for adjusting a differential pressure of a water electrolysis cell in a water electrolysis system according to claim 1 or 2, comprising: detecting a differential pressure between the cathode chamber and the anode chamber; and adjusting the differential pressure between the cathode chamber and the anode chamber based on the detected differential pressure.

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