Water electrolysis system

Abstract

A water electrolysis system is provided. The water electrolysis system (10) has a flow rate adjusting valve (47) that relatively changes a flow rate of water flowing through a first flow passage portion (52a) and a flow rate of water flowing through a second flow passage portion (52b), the first flow passage portion being a flow passage portion that extends from the first water leading-out portion (26), the second flow passage portion being a flow passage portion that extends from the second water leading-out portion (28). Accordingly, electrolysis can be efficiently performed.

Description

Technical Field

[0001] This invention relates to a water electrolysis system. Background Technology

[0002] Japanese Patent Publication No. 2019-123899 discloses a water electrolysis system having a water electrolysis stack. Multiple water electrolysis cells are stacked within this water electrolysis stack. The stacking direction of the water electrolysis cells in the water electrolysis stack is set to be along the vertical direction. Summary of the Invention

[0003] Recently, there has been anticipation for efficient water electrolysis.

[0004] The purpose of this invention is to solve the above-mentioned technical problems.

[0005] The present invention provides a water electrolysis system comprising a water electrolysis stack having 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 on the upper side of the water electrolysis stack, the second water outlet is disposed on the lower side of 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. The water electrolysis system includes a flow regulating valve that 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 the flow channel extending from the first water outlet, and the second flow channel refers to the flow channel extending from the second water outlet.

[0006] According to the method of the present invention, electrolysis can be carried out efficiently.

[0007] The above-described objectives, features, and advantages should be readily understood from the following description of the embodiments with reference to the accompanying drawings. Attached Figure Description

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

[0009] Figure 2 This is a flowchart showing the sequence of actions that change the opening degree of the flow control valve.

[0010] Figure 3A It is a graph representing the change in voltage or resistance of a water electrolysis cell. Figure 3BIt is a graph showing the change in the flow rate of water discharged from the water electrolysis reactor. Detailed Implementation

[0011] Figure 1 This is a diagram illustrating a water electrolysis system 10 according to one embodiment. Figure 1 In the diagram, arrow A1 indicates the direction of gravity, and arrow A2 indicates the direction opposite to gravity. The water electrolysis system 10 has a water electrolysis reactor 12 that produces oxygen (at atmospheric pressure) and hydrogen (at a pressure higher than oxygen) by electrolyzing water.

[0012] The water electrolysis stack 12 has a plurality of stacked water electrolysis cells 14. The water electrolysis cells 14 are, for example, formed in a circular plate shape. Although detailed illustrations are omitted, the water electrolysis cell 14 has 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 cell 14 is a PEM-type cell using a proton exchange membrane as the electrolyte membrane.

[0013] The stacking direction of the water electrolysis cells 14 in the water electrolysis stack 12 is set along the vertical direction (arrow A direction). An electrolysis power supply 16, serving as a DC power source, 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 plurality of 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] A water inlet 22 and a water outlet 24 are provided in the water electrolysis stack 12. A water inlet 22a is formed in the water inlet 22 for introducing water into the water electrolysis stack 12. The water inlet 22a communicates with a water inlet connecting hole 25, which is configured to penetrate the water electrolysis cell 14 along the stacking direction. The water inlet connecting hole 25 allows water introduced from the water inlet 22a of the water inlet 22 to flow along the stacking direction. The water inlet connecting hole 25 communicates with the anode inlet side (water supply inlet side) of each water electrolysis cell 14.

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

[0016] The water outlet 24 has a first water outlet 26 and a second water outlet 28. The first water outlet 26 is provided at the upper end (one end) of the water electrolysis cell 14 (the upper end side of the water electrolysis stack 12) in the stacking direction among the plurality of water electrolysis cells 14. That is, the first water outlet 26 is located above the water inlet 22 (in the direction of arrow A2). A first water outlet 26a is formed in the first water outlet 26, which is used to export unreacted water (remaining water) that has not been electrolyzed from the water electrolysis stack 12.

[0017] The second water outlet 28 is disposed at the lower end (the other end) of one of the plurality of water electrolysis cells 14 in the stacking direction (the lower end of the water electrolysis stack 12). That is, the second water outlet 28 is located below the water inlet 22 and the first water outlet 26 (in the direction of arrow A1). A second water outlet 28a is formed in the second water outlet 28, which is used to export unreacted water (remaining 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 respectively positioned 180° apart from 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 respectively connected to the water outlet communication hole 30, which is configured to penetrate the water electrolysis cell 14 along the stacking direction. The water outlet communication hole 30 is connected to the anode outlet side (the side that discharges water and oxygen) of each water electrolysis cell 14, allowing unreacted water that has not been electrolyzed to flow along the stacking direction and be guided 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 channel 34, a water circulation loop 36, an air blower 38, an air supply channel 40, an air exhaust channel 42, a drainage channel 44, a switching valve 46, and a flow regulating valve 47.

[0020] The water supply device 32 guides water to the water circulation loop 36. The water can be pure water. The water circulation loop 36 has 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 part of the gas-liquid separator 48. The gas-liquid separator 48 functions as a water tank for storing water. In addition, in the case of AEM-type batteries using a negative ion exchange membrane as the electrolyte membrane, alkaline water is sometimes supplied to the water electrolysis battery 14.

[0021] A water supply channel 50 connects the bottom of the gas-liquid separator 48 to the water inlet 22. The water supply channel 50 guides water stored in the gas-liquid separator 48 to the water inlet 22. A water discharge channel 52 connects the first water outlet 26 and the second water outlet 28 to the upper part 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 produced through the reaction, and hydrogen that permeates from the cathode side to the anode side.

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

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

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

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

[0026] The drainage channel 44 is a channel for discharging water from the water circulation loop 36 and the water electrolysis reactor 12 to the outside. The drainage channel 44 is connected to the lowermost part (second channel section 52b) of the water discharge channel 52. A switching valve 46 is provided in the drainage channel 44. The switching valve 46 is configured as a solenoid valve for opening and closing the drainage channel 44.

[0027] A flow regulating valve 47 is provided in the second flow channel section 52b. The flow regulating valve 47 regulates the flow rate of water flowing through the second flow channel section 52b by changing its opening relative to the second flow channel section 52b. If the flow rate of water flowing through the second flow channel section 52b decreases, the flow rate of water flowing through the first flow channel section 52a will necessarily increase. Conversely, if the flow rate of water flowing through the second flow channel section 52b increases, the flow rate of water flowing through the first flow channel section 52a will necessarily decrease. That is, the flow regulating valve 47 relatively changes the flow rate of water flowing through the first flow channel section 52a (i.e., the first flow rate) and the flow rate of water flowing through the second flow channel section 52b (i.e., the second flow rate).

[0028] The water electrolysis system 10 includes a controller 55 for overall operation control. The controller 55 is a computer including a microcomputer. The controller 55 has a CPU (Central Processing Unit), ROM, RAM, etc., as memory. A detection unit 56 is connected to the controller 55. The detection unit 56 detects information representing the resistance (or voltage) of each of the plurality of water electrolysis cells 14. The detection unit 56 includes a voltage sensor for detecting the voltage of the water electrolysis cell 14. The detection unit 56 may also include a resistance sensor for detecting the resistance of the water electrolysis cell 14. The detection unit 56 may also include a current sensor for detecting the current flowing through the electrolysis power supply 16.

[0029] The controller 55 operates as a first acquisition unit 58, a second acquisition unit 60, an arithmetic unit 62, and a control unit 64 by reading and executing a program stored in the ROM via the CPU. Furthermore, at least one of the first acquisition unit 58, the second acquisition unit 60, the arithmetic unit 62, and the control unit 64 may also be configured as a hardware functional implementer.

[0030] The first acquisition unit 58 uses the detection unit 56 to acquire information indicating the resistance of the upper battery 14U. When gas in the mixed fluid is retained on the upper battery 14U side, the cross-sectional area for the current flowing in 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 batteries 14 located at the top in the stacking direction. The upper battery 14U may also be the uppermost water electrolysis battery 14 located 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 batteries 14 located at the bottom in the stacking direction. The lower battery 14D may also be the lowermost water electrolysis battery 14 located in the stacking direction.

[0031] The calculation unit 62 performs calculations based on the resistance information acquired by the first acquisition unit 58 and the resistance information acquired by the second acquisition unit 60. The control unit 64 controls the driving and stopping of the circulating pump 54, the driving and stopping of the blower 38, and the opening and closing of the switching valve 46. In addition, the control unit 64 controls the opening change of the flow regulating valve 47. The opening change of the flow regulating valve 47 is the operation of changing the opening of the flow regulating valve 47 relative to the second flow channel section 52b.

[0032] The water electrolysis system 10 constructed in this way operates as follows.

[0033] When the circulation pump 54 is driven, water in the gas-liquid separator 48 is supplied to the water inlet 22 (located in the water electrolysis cell 14, which is approximately in the center of the stacking direction) via the water supply channel 50. The water supplied to the water inlet 22 flows into the water inlet communication hole 25 and flows 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 source 16, water is electrolyzed at the anode side of each water electrolysis cell 14. During electrolysis, hydrogen ions, electrons, and oxygen are generated at the anode side of each water electrolysis cell 14. Meanwhile, at the cathode side of each water electrolysis cell 14, hydrogen ions combine with electrons to form hydrogen. This hydrogen is extracted to the hydrogen outlet channel 20, becoming dry hydrogen (product hydrogen), and supplied to fuel cell electric vehicles (not shown).

[0035] On the other hand, at the anode outlet side, oxygen generated by the reaction, unreacted water that has not been electrolyzed, and permeated hydrogen flow. This mixture of oxygen, water, and hydrogen is discharged into the water discharge communication hole 30 and flows upward and downward (in the stacking direction). The mixture flowing upward within the water discharge communication hole 30 is guided to the first flow channel 52a via the first water discharge section 26. The mixture flowing downward within the water discharge communication hole 30 is guided to the second flow channel 52b via the second water discharge section 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 part of the gas-liquid separator 48, where they are separated into liquid (water) and gas (oxygen and hydrogen). Furthermore, in this case, the switch valve 46 closes the drain channel 44.

[0037] Water separated from the mixed fluid is stored in a gas-liquid separator 48. The water stored in the gas-liquid separator 48 flows out to the water supply channel 50 via a circulation pump 54. Oxygen and hydrogen separated from the mixed fluid are discharged to the outside through an air exhaust channel 42 via a blower 38.

[0038] Next, the operation of changing the opening degree of the flow regulating valve 47 will be explained. The operation of changing the opening degree of the flow regulating valve 47 is performed during the operation of the water electrolysis system 10. Figure 2 This is a flowchart showing the sequence of actions that change the opening degree of the flow control valve 47.

[0039] In step S1, the first acquisition unit 58 begins acquiring first information. The second acquisition unit 60 begins acquiring second information. The first information represents the resistance of the upper battery 14U detected by the detection unit 56 when a specified current flows through it. The second information represents the resistance of the lower battery 14D detected by the detection unit 56 when a specified current flows through it. The first and second information are stored in the memory simultaneously with acquisition. A current sensor (not shown) for detecting the current flowing through the electrolytic power supply 16 can also be used to acquire the first and second information. When acquiring the first and second information begins, the process proceeds to the voltage value comparison step in step S2.

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

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

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

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

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

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

[0046] Oxygen generated at the anode side of the water electrolysis cell 14 through water electrolysis exists as bubbles in the water supplied to the anode side of the water electrolysis cell 14. Furthermore, these bubbles rise due to buoyancy. Therefore, the higher the water electrolysis cell 14 is positioned in the stacking direction, the easier it is for the bubbles that rise using the water outlet connecting hole 30 to accumulate near the anode power supply. Figure 3A As shown, bubbles accumulate in the anode power supply over time, causing the resistance or voltage of the water electrolysis cell 14 to increase. This is because the contact area between the anode power supply and water decreases when bubbles accumulate in the anode power supply. That is, the bubbles can act as a resistive element. Therefore, the more bubbles accumulate in the anode power supply, the lower the electrolysis efficiency of the water electrolysis cell 14 becomes.

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

[0048] Furthermore, in this embodiment, when the difference exceeds a threshold, the control unit 64 sets the opening of the flow regulating valve 47 to be smaller than a predetermined opening. Therefore, as... Figure 3B As shown, the first flow rate (the flow rate of water flowing through the first flow channel 52a) increases over time. On the other hand, the second flow rate (the flow rate of water flowing through the second flow channel 52b) decreases over time. That is, the flow rate is changed so that the first flow rate is greater than the second flow rate. Accordingly, bubbles accumulated in the anode power supply can be effectively discharged from the water electrolysis stack 12. As a result, water electrolysis can be performed efficiently.

[0049] The above implementation method can also be modified as follows.

[0050] For example, the control unit 64 can set the opening of the flow regulating valve 47 in such a way that the larger the difference, the larger the first flow rate is compared to the second flow rate. This reduces the accumulation of bubbles in the anode power supply.

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

[0052] Alternatively, the flow regulating valve 47 can be disposed in the first flow channel portion 52a instead of the second flow channel portion 52b. In this case, for example, the flow regulating valve 47 is disposed 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 degree of the flow regulating valve 47 is set such 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. Then, in step S3, the control unit 64 sets the opening degree of the flow regulating valve 47 to be larger than the predetermined opening degree. This achieves the same effect as the embodiment described above.

[0053] Alternatively, the water electrolysis battery 14 can be an AEM type battery. In this case, the water supply device 32 guides alkaline water to the water circulation loop 36.

[0054] Alternatively, in the water electrolysis stack 12, the anode power supply (anode electrode) and the cathode power supply (cathode electrode) can be arranged in opposite directions. In this case, the water inlet connection 25 is connected to the cathode inlet side of each water electrolysis cell 14. In each water electrolysis cell 14, water is electrolyzed on the cathode side. When water is electrolyzed, hydrogen is generated on the cathode side of each water electrolysis cell 14. On the other hand, oxygen is obtained on the anode side of each water electrolysis cell 14. This oxygen is extracted to the hydrogen outlet channel 20.

[0055] As described above, in this embodiment, a flow regulating valve 47 is provided, which relatively changes the flow rate of water flowing in the first flow channel 52a on the upper side of the water electrolysis stack 12 and the flow rate of water flowing in the second flow channel 52b on the lower side of the water electrolysis stack 12. Accordingly, the flow rate of water on the upper side of the water electrolysis stack 12 can be greater than the flow rate of water on the lower side of the water electrolysis stack 12. Therefore, even if gas existing as bubbles in the water due to water electrolysis rises due to buoyancy, it will not accumulate in the upper water electrolysis cell 14 and can be discharged to the first flow channel 52a. Therefore, the obstruction of water electrolysis by bubbles can be reduced, resulting in efficient water electrolysis.

[0056] The following notes are also disclosed regarding the above-described embodiments.

[0057] (Postscript 1)

[0058] The water electrolysis system (10) of the present invention has a water electrolysis stack (12) having 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 disposed on the upper side of the water electrolysis stack, the second water outlet is disposed on the lower side of the water electrolysis stack, and the water inlet is disposed in the stacking direction of the water electrolysis cells. Between the first water outlet and the second water outlet, the water electrolysis system has a flow regulating valve (47) that relatively changes the flow rate of the water flowing through the first flow channel (52a), i.e., the first flow rate, and the flow rate of the water flowing through the second flow channel (52b), i.e., the second flow rate, wherein the first flow channel (52a) refers to the flow channel extending from the first water outlet; and the second flow channel (52b) refers to the flow channel extending from the second water outlet.

[0059] (Postscript 2)

[0060] In the water electrolysis system described in Appendix 1, it may include a detection unit (56), a first acquisition unit (58), a second acquisition unit (60), a calculation unit (62), and a control unit (64). The detection unit (56) is used to detect information representing the resistance of each of the plurality of water electrolysis cells. The first acquisition unit (58) acquires the information of the upper cell (14U) detected by the detection unit when a predetermined current flows through the upper water electrolysis cell (14U) located in the stacking direction. The second acquisition unit (60) acquires the information of the lower cell (14D) detected by the detection unit when a predetermined current flows through the lower water electrolysis cell (14D) located in the stacking direction. The calculation unit (62) calculates the difference between the voltage or resistance values ​​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. The control unit (64) sets the opening degree of the flow regulating valve based on the difference.

[0061] (Note 3)

[0062] In the water electrolysis system described in Appendix 2, the control unit may set the opening of the flow regulating valve in such a way that the first flow rate is greater than the second flow rate when the difference is above a threshold.

[0063] (Postscript 4)

[0064] In the water electrolysis system described in Appendix 3, the control unit may set the opening of the flow regulating valve such that the first flow rate is close to the second flow rate when the difference above the threshold is less than the threshold.

[0065] (Note 5)

[0066] In the water electrolysis system described in Appendix 2, the control unit may set the opening of the flow regulating valve in such a way that the larger the difference, the larger the first flow rate is compared to the second flow rate.

[0067] (Note 6)

[0068] In the water electrolysis system described in Appendix 2, the upper battery refers to the water electrolysis battery located at the top of the stacking direction, and the lower battery refers to the water electrolysis battery located at the bottom of the stacking direction.

[0069] Although the present invention has been described in detail, it is not limited to the embodiments described above. Various additions, substitutions, modifications, and partial deletions can be made to these embodiments without departing from the spirit of the invention, or from the spirit of the invention derived from the content described in the technical solutions and their equivalents. Furthermore, these embodiments can also be implemented in combination. For example, in the above embodiments, the order of each action and the order of each process are shown as an example, and are not limited thereto. The same applies to the use of numerical values ​​or formulas in the description of the above embodiments.

Claims

1. A water electrolysis system comprising a water electrolysis stack having 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 on the upper side of the water electrolysis stack, the second water outlet is disposed on the lower side of 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. Its features are, It includes a flow regulating valve, a detection unit, a first acquisition unit, a second acquisition unit, a calculation unit, and a control unit, wherein... The flow regulating valve 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 the flow channel extending from the first water outlet; and the second flow channel refers to the flow channel extending from the second water outlet. The detection unit is used to detect information representing 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 when a predetermined current flows through the water electrolysis cell located above the stacking direction, i.e., the upper battery. The second acquisition unit acquires the information of the lower battery detected by the detection unit when a predetermined current flows through the water electrolysis cell located below the stacking direction, i.e., the lower battery. The calculation unit calculates the difference in voltage or resistance between the upper battery and the lower battery based on the information obtained by the first acquisition unit and the information obtained by the second acquisition unit. The control unit sets the opening degree of the flow regulating valve based on the differential.

2. The water electrolysis system according to claim 1, characterized in that, When the difference is above a threshold, the control unit sets the opening of the flow regulating valve in such a way that the first flow rate is greater than the second flow rate.

3. The water electrolysis system according to claim 2, characterized in that, When the difference that reaches or exceeds the threshold is less than the threshold, the control unit sets the opening of the flow regulating valve in such a way that the first flow rate is close to the second flow rate.

4. The water electrolysis system according to claim 1, characterized in that, The control unit sets the opening of the flow regulating valve in such a way that the larger the difference, the larger the first flow rate is compared to the second flow rate.

5. The water electrolysis system according to claim 1, characterized in that, The uppermost battery refers to the water electrolysis battery located at the top of the stacking direction. The lower battery refers to the water electrolysis battery located at the bottom of the stacking direction.

Images