Water electrolysis system

Abstract

The invention provides a water electrolysis system. The water electrolysis system (10) is provided with: a flow rate control valve (47) that relatively changes a first flow rate, which is the flow rate of water flowing through a first flow path part (52a) that extends from the first water discharge part (26), and a second flow rate, which is the flow rate of water flowing through a second flow path part (52b); the second flow path portion is a flow path portion extending from the second water lead-out portion (28). In this way, electrolysis can be efficiently performed.

Description

Technical Field

[0001] The present invention relates to a water electrolysis system. Background Art

[0002] Japanese Patent Application Publication No. 2019-123899 discloses a water electrolysis system having a water electrolysis stack. The stack comprises a plurality of water electrolysis cells stacked in a vertical direction. Summary of the Invention

[0003] Recently, high-efficiency electrolysis of water has been expected.

[0004] The purpose of the present invention is to solve the above technical problems.

[0005] The present invention is a water electrolysis system comprising a water electrolysis stack, wherein the water electrolysis stack comprises a plurality of water electrolysis cells, a water inlet, a first water outlet and a second water outlet, wherein the plurality of water electrolysis cells are stacked in a vertical direction, the first water outlet is arranged on the upper side of the water electrolysis stack, the second water outlet is arranged on the lower side of the water electrolysis stack, the water inlet is arranged between the first water outlet and the second water outlet in the stacking direction of the water electrolysis cells, and the water electrolysis system comprises a flow regulating valve which relatively changes the flow rate of water flowing through the first flow channel, i.e., the first flow rate, and the flow rate of water flowing through the second flow channel, i.e., the second flow rate, wherein the first flow channel refers to a flow channel extending from the first water outlet; and the second flow channel refers to a flow channel extending from the second water outlet.

[0006] According to the embodiment of the present invention, electrolysis can be performed efficiently.

[0007] The above-mentioned objects, features, and advantages will be readily understood from the following description of the embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a diagram showing a water electrolysis system according to one embodiment.

[0009] Figure 2 This is a flowchart showing the procedure of the flow control valve opening degree changing operation.

[0010] Figure 3A It is a graph showing the change in voltage or resistance of a water electrolysis cell. Figure 3BThis is a graph showing changes in the flow rate of water discharged from the water electrolysis stack. DETAILED DESCRIPTION

[0011] Figure 1 1 is a diagram showing a water electrolysis system 10 according to one embodiment. Figure 1 The arrow A1 indicates the direction of gravity, and the arrow A2 indicates the direction opposite to the direction of gravity. The water electrolysis system 10 includes a water electrolysis stack 12 that produces oxygen (normal pressure) and hydrogen (higher pressure than oxygen) by electrolyzing water.

[0012] The water electrolysis stack 12 includes a plurality of stacked water electrolysis cells 14. The water electrolysis cells 14 are formed, for example, in the shape of a disk. Although detailed illustrations are omitted, the water electrolysis cells 14 include a membrane electrode assembly, and an anode separator and a cathode separator disposed on both sides of the membrane electrode assembly. The membrane electrode assembly includes an electrolyte membrane, and an anode power supply (anode electrode) and a cathode power supply (cathode electrode) disposed on both sides of the electrolyte membrane in the thickness direction. In this embodiment, the water electrolysis cells 14 are PEM-type cells using a proton exchange membrane as the electrolyte membrane.

[0013] The stacking direction of the water electrolysis cells 14 of the water electrolysis stack 12 is arranged along the vertical direction (direction of arrow A). An electrolysis power supply 16, serving as a DC power supply, is connected to the water electrolysis stack 12. The electrolysis power supply 16 is connected, for example, to both ends of the series-connected water electrolysis cells 14. End plates 18a and 18b are provided at both ends of the stacking direction of the multiple water electrolysis cells 14. A hydrogen outlet channel 20 is connected to the upper end plate 18a, which communicates with the cathode side (high-pressure hydrogen generation side) of each water electrolysis cell 14.

[0014] The water electrolysis stack 12 is provided with a water inlet 22 and a water outlet 24. A water inlet port 22a is formed in the water inlet port 22 for introducing water into the water electrolysis stack 12. The water inlet port 22a communicates with a water inlet communication hole 25 provided to penetrate the water electrolysis cells 14 in the stacking direction. The water inlet communication hole 25 allows water introduced from the water inlet port 22a of the water inlet port 22 to flow in the stacking direction. The water inlet communication hole 25 communicates with the anode inlet side (water supply inlet side) of each water electrolysis cell 14.

[0015] The water inlet 22 is provided in the water electrolysis cell 14 located between (in the middle of) the two ends in the stacking direction. Specifically, the water inlet 22 is provided in the water electrolysis cell 14 located in the central region of the stacking direction. The central region refers to, for example, the region in the middle of a region dividing the water electrolysis cells 14 into three equal parts in the stacking direction. However, the central region may also be, for example, the region in the middle of a region divided into three equal parts in the stacking direction at a ratio of 1:2:1.

[0016] The water discharge section 24 includes a first water discharge section 26 and a second water discharge section 28. The first water discharge section 26 is provided at the upper end (one end) of the plurality of water electrolysis cells 14 in the stacking direction (on the upper end side of the water electrolysis stack 12). Specifically, the first water discharge section 26 is located above the water inlet section 22 (in the direction of arrow A2). A first water outlet 26a is formed in the first water discharge section 26 for discharging unreacted water (excess water) that has not been electrolyzed from the water electrolysis stack 12.

[0017] The second water discharge portion 28 is provided at the lower end (the other end) of the plurality of water electrolysis cells 14 in the stacking direction (the lower end of the water electrolysis stack 12). Specifically, the second water discharge portion 28 is located below the water inlet portion 22 and the first water discharge portion 26 (in the direction of arrow A1). A second water discharge outlet 28a is formed in the second water discharge portion 28 for discharging unreacted water (excess water) that has not been electrolyzed from the water electrolysis stack 12.

[0018] The first water outlet 26 and the second water outlet 28 are each provided at a position 180° apart in phase with the water inlet 22 along the circumferential direction of the water electrolysis stack 12. The first water outlet 26a and the second water outlet 28a are each connected to a water outlet communication hole 30 provided to penetrate the water electrolysis cells 14 in the stacking direction. The water outlet communication hole 30 communicates with the anode outlet side (the side from which water and oxygen are discharged) of each water electrolysis cell 14, allowing unreacted water that has not been electrolyzed to flow along the stacking direction and be directed to the first water outlet 26 and the second water outlet 28.

[0019] The water electrolysis system 10 includes a water supply device 32 , a water supply passage 34 , a water circulation circuit 36 , an air blower 38 , an air supply passage 40 , an air exhaust passage 42 , a drainage passage 44 , an on-off valve 46 , and a flow rate regulating valve 47 .

[0020] The water supply device 32 directs water to the water circulation circuit 36. The water can be pure water. The water circulation circuit 36 includes a gas-liquid separator 48, a water supply channel 50, a water discharge channel 52, and a circulation pump 54. The water supply channel 34 is connected to the upper portion of the gas-liquid separator 48. The gas-liquid separator 48 functions as a water tank for storing water. In the case of AEM batteries using a negative ion exchange membrane as the electrolyte membrane, alkaline water may also be supplied to the water electrolysis cell 14.

[0021] The water supply channel 50 connects the bottom of the gas-liquid separator 48 to the water inlet 22. The water supply channel 50 guides the water stored in the gas-liquid separator 48 to the water inlet 22. The water discharge channel 52 connects the first water outlet 26 and the second water outlet 28 to the upper portion of the gas-liquid separator 48, respectively. The water discharge channel 52 guides the mixed fluid into the gas-liquid separator 48. The mixed fluid contains unreacted water that has not been electrolyzed, oxygen generated by the reaction, and hydrogen that has permeated from the cathode side to the anode side.

[0022] The water discharge passage 52 includes a first flow passage portion 52a extending from the first water discharge portion 26, a second flow passage portion 52b extending from the second water discharge portion 28, and a third flow passage portion 52c connecting the first and second flow passage portions 52a, 52b. The second flow passage portion 52b is located below the first and third flow passage portions 52a, 52c. In other words, the second flow passage portion 52b is located at the lowest point of the water discharge passage 52.

[0023] The circulation pump 54 is provided, for example, in the water supply passage 50. The circulation pump 54 circulates water so that the water stored in the gas-liquid separator 48 is supplied from the water inlet 22 to the water electrolysis stack 12 via the water supply passage 50, and unreacted water in the water electrolysis stack 12 that has not been electrolyzed is discharged from the water outlet 24 to the gas-liquid separator 48 via the water discharge passage 52.

[0024] In such a water circulation circuit 36 , the second water outlet portion 28 is located below the gas-liquid separator 48 , the water supply passage 50 , and the circulation pump 54 , and is connected to the lowermost portion (second flow path portion 52 b ) of the water discharge passage 52 .

[0025] Blower 38 is an air supply device for introducing dilution air into gas-liquid separator 48 through air supply duct 40. Air supply duct 40 and air discharge duct 42 are connected to the upper portion of gas-liquid separator 48. Oxygen and hydrogen in gas-liquid separator 48 are discharged into air discharge duct 42 along with the air introduced from blower 38.

[0026] The drain flow path 44 is a flow path for discharging water from the water circulation circuit 36 and the water electrolysis stack 12 to the outside. The drain flow path 44 is connected to the lowest portion (second flow path portion 52b) of the water discharge passage 52. An on-off valve 46 is provided in the drain flow path 44. The on-off valve 46 is configured as a solenoid valve for opening and closing the drain flow path 44.

[0027] The flow control valve 47 is provided in the second flow channel portion 52b. The flow control valve 47 adjusts the flow rate of water flowing through the second flow channel portion 52b by changing the opening relative to the second flow channel portion 52b. If the flow rate of water flowing through the second flow channel portion 52b decreases, the flow rate of water flowing through the first flow channel portion 52a will inevitably increase. Conversely, if the flow rate of water flowing through the second flow channel portion 52b increases, the flow rate of water flowing through the first flow channel portion 52a will inevitably decrease. In other words, the flow control valve 47 relatively changes the flow rate of water flowing through the first flow channel portion 52a, i.e., the first flow rate, and the flow rate of water flowing through the second flow channel portion 52b, i.e., the second flow rate.

[0028] The water electrolysis system 10 includes a controller 55 that controls the overall operation of the water electrolysis system 10. The controller 55 is a computer including a microcomputer. The controller 55 includes a CPU (central processing unit), ROM, RAM, and other memory components. A detection unit 56 is connected to the controller 55. The detection unit 56 detects information indicating the resistance (or voltage) of each of the multiple water electrolysis cells 14. The detection unit 56 includes a voltage sensor for detecting the voltage of the water electrolysis cells 14. The detection unit 56 may also include a resistance sensor for detecting the resistance of the water electrolysis cells 14. The detection unit 56 may also include a current sensor for detecting the current flowing through the electrolysis power supply 16.

[0029] The CPU reads and executes the program stored in the ROM, and the controller 55 operates as a first acquisition unit 58, a second acquisition unit 60, a calculation unit 62, and a control unit 64. Furthermore, at least one of the first acquisition unit 58, the second acquisition unit 60, the calculation unit 62, and the control unit 64 may be configured as a hardware function implementer.

[0030] The first acquisition unit 58 uses the detection unit 56 to acquire information indicating the resistance of the upper battery 14U. When the gas in the mixed fluid is retained on the upper battery 14U side, the cross-sectional area of the current flowing through the anode power supply (anode electrode) and the cathode power supply (cathode electrode) decreases, and the resistance value increases. The upper battery 14U is one of the multiple water electrolysis cells 14 located at the top in the stacking direction. The upper battery 14U can also be the water electrolysis cell 14 located at the top in the stacking direction. The second acquisition unit 60 uses the detection unit 56 to acquire information indicating the resistance of the lower battery 14D. The lower battery 14D is one of the multiple water electrolysis cells 14 located at the bottom in the stacking direction. The lower battery 14D can also be the water electrolysis cell 14 located at the bottom in the stacking direction.

[0031] The calculation unit 62 performs calculations based on the information indicating the resistance acquired by the first acquisition unit 58 and the information indicating the resistance acquired by the second acquisition unit 60. The control unit 64 controls the driving and stopping of the circulation pump 54, controls the driving and stopping of the blower 38, and controls the opening and closing of the on-off valve 46. The control unit 64 also controls the opening change of the flow control valve 47. The opening change of the flow control valve 47 is an action to change the opening of the flow control valve 47 relative to the second flow path portion 52b.

[0032] The water electrolysis system 10 configured in this manner operates as follows.

[0033] When the circulation pump 54 is driven, the water in the gas-liquid separator 48 is supplied to the water inlet 22 (located in the water electrolysis cell 14 at approximately the center in the stacking direction) via the water supply passage 50. The water supplied to the water inlet 22 flows into the water inlet communication hole 25 and circulates upward and downward (in the stacking direction), thereby being distributed to the anode inlet side of each water electrolysis cell 14.

[0034] At this time, when a voltage is applied to the water electrolysis stack 12 by the electrolysis power supply 16, water is electrolyzed on the anode side of each water electrolysis cell 14. As the water is electrolyzed, hydrogen ions, electrons, and oxygen are generated on the anode side of each water electrolysis cell 14. Meanwhile, on the cathode side of each water electrolysis cell 14, hydrogen ions combine with electrons to produce hydrogen. This hydrogen is extracted into the hydrogen outlet channel 20 as dry hydrogen (product hydrogen), which is then supplied to a fuel cell electric vehicle (not shown), etc.

[0035] Meanwhile, at the anode outlet, oxygen generated by the reaction, unreacted water that was not electrolyzed, and permeated hydrogen flow. This mixed fluid containing oxygen, water, and hydrogen is discharged into the water discharge passage 30 and circulates upward and downward (in the stacking direction). The mixed fluid flowing upward within the water discharge passage 30 is guided to the first flow channel 52a via the first water discharge portion 26. The mixed fluid flowing downward within the water discharge passage 30 is guided to the second flow channel 52b via the second water discharge portion 28.

[0036] The mixed fluid in the first flow channel 52a and the mixed fluid in the second flow channel 52b merge in the third flow channel 52c and are guided to the upper portion of the gas-liquid separator 48, where they are separated into liquid (water) and gas (oxygen and hydrogen). In this case, the on-off valve 46 closes the drain flow channel 44.

[0037] The water separated from the mixed fluid is stored in the gas-liquid separator 48. The water stored in the gas-liquid separator 48 flows out to the water supply passage 50 via the circulation pump 54. The oxygen and hydrogen separated from the mixed fluid are discharged to the outside from the air discharge passage 42 via the blower 38.

[0038] Next, the opening degree changing operation of the flow rate regulating valve 47 will be described. The opening degree changing operation of the flow rate regulating valve 47 is performed during the operation of the water electrolysis system 10 . Figure 2 This is a flowchart showing the procedure of the opening degree changing operation of the flow rate regulating valve 47 .

[0039] In step S1, the first acquisition unit 58 begins acquiring the first information. The second acquisition unit 60 begins acquiring the second information. The first information is information indicating the resistance of the upper cell 14U detected by the detection unit 56 when a predetermined current flows through the upper cell 14U. The second information is information indicating the resistance of the lower cell 14D detected by the detection unit 56 when a predetermined current flows through the lower cell 14D. The first and second information are simultaneously stored in the memory upon acquisition. Alternatively, the first and second information may be acquired using a current sensor (not shown) for detecting the current flowing through the electrolytic power source 16. When the acquisition of the first and second information begins, the process proceeds to the voltage value comparison step of step S2.

[0040] In step S2, the calculation unit 62 calculates the voltage difference (deviation) between the upper cell 14U and the lower cell 14D based on the first information and the second information just stored in the memory. The voltage difference may be the absolute value of the voltage difference. The calculation unit 62 may also calculate the resistance difference between the upper cell 14U and the lower cell 14D. The resistance difference may be the absolute value of the resistance difference.

[0041] The control unit 64 compares the voltage difference between the upper cell 14U and the lower cell 14D, calculated by the calculation unit 62, with a threshold value. If the voltage difference between the upper cell 14U and the lower cell 14D is less than the threshold value (step S2: No), the opening change operation does not proceed to step S3. In this case, the calculation by the calculation unit 62 and the comparison by the control unit 64 are repeated. On the other hand, if the voltage difference between the upper cell 14U and the lower cell 14D is greater than the threshold value (step S2: Yes), it is determined that the gas in the mixed fluid is stagnating on the upper cell 14U side, and the process proceeds to step S3 to change the opening.

[0042] In step S3, the control unit 64 sets the opening of the flow control valve 47 so that the first flow rate (the flow rate of water flowing through the first flow channel portion 52a) is greater than the second flow rate (the flow rate of water flowing through the second flow channel portion 52b). Specifically, the control unit 64 sets the opening of the flow control valve 47 to be smaller than a predetermined opening. After the opening of the flow control valve 47 is set, the process proceeds to the voltage value comparison step in step S4.

[0043] In step S4, the calculation unit 62 calculates the difference (deviation) in the voltage values between the upper battery 14U and the lower battery 14D based on the first and second information just stored in the memory. The control unit 64 compares the difference in voltage values between the upper battery 14U and the lower battery 14D calculated by the calculation unit 62 with a threshold value. If the difference in voltage values between the upper battery 14U and the lower battery 14D is still greater than the threshold value (step S4: No), the opening change operation does not proceed to step S5. In this case, the calculation by the calculation unit 62 and the comparison by the control unit 64 are repeated. On the other hand, if the difference in voltage values between the upper battery 14U and the lower battery 14D is less than the threshold value (step S4: Yes), it is determined that the gas trapped on the upper battery 14U side has been discharged, and the operation proceeds to step S5 to change the opening.

[0044] In step S5, the control unit 64 sets the opening of the flow control valve 47 so that the first flow rate (the flow rate of water flowing through the first flow channel portion 52a) approaches the second flow rate (the flow rate of water flowing through the second flow channel portion 52b). Specifically, the control unit 64 sets the opening of the flow control valve 47 to a predetermined opening. After the opening of the flow control valve 47 is set, the opening change operation proceeds to step S2.

[0045] Figure 3A is a graph showing changes in voltage or resistance of the water electrolysis cell 14. Figure 3B A graph showing changes in the flow rate of water discharged from the water electrolysis stack 12.

[0046] Oxygen generated by the electrolysis of water on the anode side of the water electrolysis cell 14 exists as bubbles in the water supplied to the anode side of the water electrolysis cell 14. The bubbles rise due to buoyancy. Therefore, the higher the water electrolysis cell 14 is arranged in the stacking direction, the more likely the bubbles that rise using the water outlet communication hole 30 are to accumulate near the anode power supply. Figure 3A As shown, bubbles accumulate in the anode power supply over time, increasing the resistance or voltage of water electrolysis cell 14. This is because as bubbles accumulate in the anode power supply, the contact area between the anode power supply and water decreases. In other words, the bubbles act as a resistor. Therefore, the more bubbles accumulate in the anode power supply, the lower the electrolysis efficiency of water electrolysis cell 14.

[0047] In this embodiment, the calculation unit 62 calculates the difference between the voltage value of the upper cell 14U when a predetermined current is flowing and the voltage value of the lower cell 14D when a predetermined current is flowing. Therefore, the degree of bubble accumulation in the anode power supply can be accurately estimated.

[0048] In addition, in this embodiment, when the difference is greater than the threshold value, the control unit 64 sets the opening of the flow control valve 47 to be smaller than the predetermined opening. Figure 3B As shown, the first flow rate (the flow rate of water flowing through the first flow channel portion 52a) increases over time. On the other hand, the second flow rate (the flow rate of water flowing through the second flow channel portion 52b) decreases over time. In other words, the flow rate is changed so that the first flow rate is larger than the second flow rate. This allows bubbles accumulated in the anode current source to be effectively discharged from the water electrolysis stack 12. As a result, water can be efficiently electrolyzed.

[0049] The above-mentioned embodiment may be modified as follows.

[0050] For example, the control unit 64 may set the opening of the flow rate regulating valve 47 so that the larger the difference, the larger the first flow rate is relative to the second flow rate. This can reduce the accumulation of bubbles in the anode power supply.

[0051] Alternatively, the calculation unit 62 may calculate the difference between the first flow rate detected by the first flow rate sensor provided in the first flow channel portion 52a and the second flow rate detected by the second flow rate sensor provided in the second flow channel portion 52b.

[0052] Alternatively, the flow control valve 47 may be provided in the first flow channel portion 52a instead of the second flow channel portion 52b. In this case, for example, the flow control valve 47 is provided in the first flow channel portion 52a, which has a larger cross-sectional area than the second flow channel portion 52b. Furthermore, the predetermined opening of the flow control valve 47 is set so that the cross-sectional area of the first flow channel portion 52a is equal to the cross-sectional area of the second flow channel portion 52b. Furthermore, in step S3, the control unit 64 sets the opening of the flow control valve 47 to be larger than the predetermined opening. This achieves the same effects as the above-described embodiment.

[0053] Alternatively, the water electrolysis cell 14 may be an AEM type cell. In this case, the water supply 32 directs alkaline water to the water circulation loop 36.

[0054] Alternatively, the anode power supply (anode electrode) and cathode power supply (cathode electrode) may be arranged opposite each other in the water electrolysis stack 12. In this case, the water inlet communication hole 25 communicates with the cathode inlet side of each water electrolysis cell 14. In each water electrolysis cell 14, water is electrolyzed on the cathode side. As the water is electrolyzed, hydrogen is generated on the cathode side of each water electrolysis cell 14. Meanwhile, oxygen is generated on the anode side of each water electrolysis cell 14. This oxygen is extracted into the hydrogen outlet channel 20.

[0055] As described above, in this embodiment, a flow control valve 47 is provided. This flow control valve 47 relatively varies the flow rate of water flowing through the first flow channel portion 52a above the water electrolysis stack 12 and the flow rate of water flowing through the second flow channel portion 52b below the water electrolysis stack 12. This allows the flow rate of water above the water electrolysis stack 12 to be greater than the flow rate of water below the water electrolysis stack 12. Therefore, even if gas bubbles formed within the water due to electrolysis rise due to buoyancy, they are not accumulated in the water electrolysis cell 14 located above and are instead discharged into the first flow channel portion 52a. This reduces the interference of bubbles with water electrolysis, resulting in efficient water electrolysis.

[0056] Regarding the above-mentioned embodiment, the following additional notes are disclosed.

[0057] (Note 1) The water electrolysis system (10) of the present invention has a water electrolysis stack (12), which has a plurality of water electrolysis cells (14), a water inlet (22), a first water outlet (26) and a second water outlet (28), wherein the plurality of water electrolysis cells are stacked in a vertical direction, the first water outlet is arranged on the upper side of the water electrolysis stack, the second water outlet is arranged on the lower side of the water electrolysis stack, and the water inlet is arranged in the stacking direction of the water electrolysis cells. Between the first water outlet portion and the second water outlet portion, the water electrolysis system has a flow regulating valve (47), which relatively changes the flow rate of the water flowing through the first flow channel portion (52a), i.e., the first flow rate, and the flow rate of the water flowing through the second flow channel portion (52b), i.e., the second flow rate, wherein the first flow channel portion (52a) refers to the flow channel portion extending from the first water outlet portion; and the second flow channel portion (52b) refers to the flow channel portion extending from the second water outlet portion.

[0058] (Note 2) In the water electrolysis system described in Supplement 1, it can be provided with a detection unit (56), a first acquisition unit (58), a second acquisition unit (60), a calculation unit (62) and a control unit (64), wherein the detection unit (56) is used to detect information indicating the resistance of each of the plurality of water electrolysis cells; the first acquisition unit (58) acquires the information of the upper cell detected by the detection unit when a specified current flows through the water electrolysis cell located above in the stacking direction, i.e., the upper cell (14U); the second acquisition unit (60) acquires the information of the lower cell detected by the detection unit when a specified current flows through the water electrolysis cell located below in the stacking direction, i.e., the lower cell (14D); the calculation unit (62) calculates the difference in voltage or resistance between the upper cell and the lower cell based on the information acquired by the first acquisition unit and the information acquired by the second acquisition unit; and the control unit (64) sets the opening of the flow control valve based on the difference.

[0059] (Note 3) In the water electrolysis system according to Supplementary Note 2, the control unit may set the opening of the flow rate regulating valve so that the first flow rate is greater than the second flow rate when the difference is equal to or greater than a threshold value.

[0060] (Note 4) In the water electrolysis system according to Supplementary Note 3, when the difference that is equal to or greater than the threshold value is smaller than the threshold value, the control unit may set the opening of the flow rate regulating valve so that the first flow rate approaches the second flow rate.

[0061] (Note 5) In the water electrolysis system according to Supplementary Note 2, the control unit may set the opening of the flow rate regulating valve so that the first flow rate becomes larger than the second flow rate as the difference becomes larger.

[0062] (Note 6) In the water electrolysis system described in Supplementary Note 2, the upper cell may be the water electrolysis cell located at the uppermost position in the stacking direction, and the lower cell may be the water electrolysis cell located at the lowermost position in the stacking direction.

[0063] Although the present invention has been described in detail, the present invention is not limited to the above-mentioned embodiments. These embodiments can be supplemented, replaced, changed, partially deleted, etc. without departing from the scope of the present invention, or without departing from the scope of the present invention derived from the contents recorded in the technical solution and its equivalents. In addition, these embodiments can also be implemented in combination. For example, in the above-mentioned embodiment, the order of each action and the order of each processing are shown as an example and are not limited to this. In addition, the same applies to the case where numerical values or formulas are used in the description of the above-mentioned embodiment.

Claims

1. A water electrolysis system comprising a water electrolysis stack, the water electrolysis stack comprising a plurality of water electrolysis cells, a water inlet, a first water outlet, and a second water outlet, wherein the plurality of water electrolysis cells are stacked in a vertical direction, the first water outlet is disposed above the water electrolysis stack, the second water outlet is disposed below the water electrolysis stack, and the water inlet is disposed between the first water outlet and the second water outlet in the stacking direction of the water electrolysis cells. It is characterized by: It has a flow regulating valve, which relatively changes the flow rate of water flowing through the first flow channel portion, i.e., the first flow rate, and the flow rate of water flowing through the second flow channel portion, i.e., the second flow rate, wherein the first flow channel portion refers to the flow channel portion extending from the first water outlet portion; the second flow channel portion refers to the flow channel portion extending from the second water outlet portion.

2. The water electrolysis system according to claim 1, characterized in that It has a detection unit, a first acquisition unit, a second acquisition unit, a calculation unit and a control unit, wherein: The detection unit is configured to detect information indicating the resistance of each of the plurality of water electrolysis cells; The first acquisition unit acquires the information of the upper battery detected by the detection unit in a state where a predetermined current flows through the water electrolysis battery located at the upper side in the stacking direction, i.e., the upper battery; The second acquisition unit acquires the information of the lower battery detected by the detection unit in a state where a predetermined current flows through the water electrolysis battery located at the bottom in the stacking direction, i.e., the lower battery; The calculation unit calculates a difference in voltage or resistance between the upper battery and the lower battery based on the information acquired by the first acquisition unit and the information acquired by the second acquisition unit; The control unit sets the opening degree of the flow rate regulating valve based on the difference.

3. The water electrolysis system according to claim 2, characterized in that When the difference is equal to or greater than a threshold value, the control unit sets the opening degree of the flow rate regulating valve so that the first flow rate is greater than the second flow rate.

4. The water electrolysis system according to claim 3, characterized in that When the difference that is equal to or greater than the threshold value is smaller than the threshold value, the control unit sets the opening of the flow rate regulating valve so that the first flow rate approaches the second flow rate.

5. The water electrolysis system according to claim 2, characterized in that: The control unit sets the opening degree of the flow rate regulating valve so that the first flow rate becomes larger than the second flow rate as the difference becomes larger.

6. The water electrolysis system according to claim 2, characterized in that: The upper battery refers to the water electrolysis battery located at the top in the stacking direction, The lower cell refers to the water electrolysis cell located at the bottom in the stacking direction.

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