WATER ELECTROLYSIS SYSTEM AND ENERGY SYSTEM

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2024-196553 filed on November 11, 2024, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The present disclosure relates to a water electrolysis system and an energy system.

DESCRIPTION OF THE RELATED ART

In recent years, in order to ensure that more people have access to affordable, reliable, sustainable and modern energy, research and development have been conducted in relation to an electrolysis system and an energy system that contribute to energy efficiency.

For example, in JP H09-139217 A, an energy system is disclosed that is equipped with a water electrolysis system and a fuel cell system. In the water electrolysis system, the water that is supplied from a water tank is electrolyzed in a water electrolysis device, to thereby generate hydrogen gas and oxygen gas. The fuel cell system generates electrical power through an electrochemical reaction between the hydrogen gas and the oxygen gas generated in the water electrolysis system.

SUMMARY OF THE INVENTION

There is a long awaited need for a more satisfactory water electrolysis system and a more satisfactory energy system.

The present disclosure has the object of solving the aforementioned problem.

One aspect of the present disclosure is characterized by a water electrolysis system, comprising: a water electrolysis device including an electrolyte membrane, and a first flow path and a second flow path that are disposed on both sides of the electrolyte membrane, the water electrolysis device being configured to, by electrolyzing water, generate an oxygen gas in the first flow path and generate a hydrogen gas in the second flow path; a first gas/liquid separator and a second gas/liquid separator that are configured to store the water; a water supply flow path configured to supply, to the water electrolysis device, the water that is stored in the first gas/liquid separator and the water that is stored in the second gas/liquid separator; a first lead-out flow path configured to lead out the oxygen gas that is generated in the first flow path into the first gas/liquid separator; and a second lead-out flow path configured to lead out the hydrogen gas that is generated in the second flow path into the second gas/liquid separator, wherein the first flow path and the second flow path are each filled with the water when the water is electrolyzed by the water electrolysis device, the water that is stored in the first gas/liquid separator and the water that is filled in the first flow path are connected to each other, and the water that is stored in the second gas/liquid separator and the water that is filled in the second flow path are connected to each other, and the water electrolysis system is configured to allow the water that is stored in the first gas/liquid separator and the water that is stored in the second gas/liquid separator to communicate with each other.

Another aspect of the present disclosure is characterized by an energy system, comprising the above-described water electrolysis system, and a fuel cell system configured to generate electrical power by using the hydrogen gas and the oxygen gas that are generated by the water electrolysis system, wherein water that is generated when the fuel cell system generates the electrical power is supplied to at least one of the first gas/liquid separator or the second gas/liquid separator.

According to the present disclosure, it is possible to provide a more satisfactory water electrolysis system and a more satisfactory energy system.

The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which a preferred embodiment of the present invention is shown by way of illustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an energy system;

FIG. 2 is a schematic diagram of a water electrolysis cell;

FIG. 3 is a schematic diagram of an energy system equipped with a water electrolysis system according to a First Exemplary Modification;

FIG. 4 is a schematic diagram of an energy system equipped with a water electrolysis system according to a Second Exemplary Modification;

FIG. 5 is a schematic diagram of an energy system equipped with a water electrolysis system according to a Third Exemplary Modification;

FIG. 6 is a schematic diagram of an energy system equipped with a water electrolysis system according to a Fourth Exemplary Modification; and

FIG. 7 is a schematic diagram of an energy system equipped with a water electrolysis system according to a Fifth Exemplary Modification.

DETAILED DESCRIPTION OF THE INVENTION

The water electrolysis system is equipped with a water electrolysis device including an electrolyte membrane, and a first flow path and a second flow path disposed on both sides of the electrolyte membrane. In JP H09-139217 A, for example, in the case that water is supplied from a water tank to the first flow path and is not supplied to the second flow path, a gas that is generated in the second flow path and raised in pressure may permeate through the electrolyte membrane and flow into the first flow path (cross leakage may occur). Further, in the case that the electrolyte membrane has deteriorated (for example, tearing or breakage in the electrolyte membrane has occurred), there is a possibility that the generated gases may mix with each other. The present disclosure is capable of providing a water electrolysis system and an energy system that can suppress cross leakage of the generated gases, and further, can suppress mixing of the generated gases with each other even in the case that the electrolyte membrane has deteriorated.

FIG. 1 is a schematic diagram of an energy system 12. As shown in FIG. 1, the energy system 12 is a circulative renewable energy system. The energy system 12 is a system in which a fuel cell system 14 and a water electrolysis system 10 are combined. The fuel cell system 14 generates electrical power by means of an electrochemical reaction between the oxygen gas and the hydrogen gas. In the fuel cell system 14, the water is generated when the electrical power is generated. The water electrolysis system 10 electrolyzes the water and thereby generates the oxygen gas and the hydrogen gas. The water electrolysis system 10 utilizes the water that is generated in the fuel cell system 14. The fuel cell system 14 utilizes the oxygen gas and the hydrogen gas that are generated in the water electrolysis system 10.

Such an energy system 12 can be positioned, for example, on the Earth or on the surface of the moon. Further, the energy system 12 may also be installed on an artificial satellite such as the International Space Station (ISS) or the like.

The fuel cell system 14 is equipped with a fuel cell stack 16. The fuel cell stack 16 is a polymer electrolyte fuel cell (PEFC). The fuel cell stack 16 includes a plurality of electrical power generating cells 18, and a pair of end plates 20. The plurality of electrical power generating cells 18 are stacked on one another. The pair of end plates 20 sandwich the plurality of electrical power generating cells 18 therebetween in the stacking direction of the plurality of electrical power generating cells 18.

A detailed illustration of the electrical power generating cells 18 is omitted. Each of the electrical power generating cells 18 includes a membrane electrode assembly (MEA), and a pair of separators. The membrane electrode assembly is sandwiched between the pair of separators. The membrane electrode assembly includes an electrolyte membrane, an anode, and a cathode. The electrolyte membrane is a solid polymer electrolyte membrane. The electrical power generating cells 18 generate electrical power by means of an electrochemical reaction between the hydrogen gas and the oxygen gas. When the electrical power generating cells 18 generate electrical power, the water is generated at the cathode.

The fuel cell system 14 is further equipped with a first oxygen gas supply path 22, a second oxygen gas supply path 24, an oxygen gas discharge path 26, a gas/liquid separator 28, and a first drainage path 30. The first oxygen gas supply path 22 supplies the oxygen gas that is generated by the water electrolysis system 10 to the gas/liquid separator 28. An on-off valve 32 is provided in the first oxygen gas supply path 22. The on-off valve 32 opens and closes the first oxygen gas supply path 22.

The second oxygen gas supply path 24 connects the gas/liquid separator 28 and the fuel cell stack 16 to each other. The second oxygen gas supply path 24 introduces the oxygen gas inside the gas/liquid separator 28 into the fuel cell stack 16. The oxygen gas discharge path 26 connects the fuel cell stack 16 and the gas/liquid separator 28 to each other. An oxygen exhaust gas (an off gas) that is discharged from the fuel cell stack 16 flows through the oxygen gas discharge path 26. The oxygen exhaust gas contains an unreacted oxygen gas that has not reacted in the electrical power generating cells 18. Further, the oxygen exhaust gas also contains moisture that is generated at the cathodes of the electrical power generating cells 18.

The gas/liquid separator 28 separates, into a gas and a liquid, the oxygen exhaust gas that is guided from the oxygen gas discharge path 26. Stated otherwise, the gas/liquid separator 28 removes the water vapor from the oxygen exhaust gas. The gas/liquid separator 28 stores the water (liquid water) that is separated from the oxygen exhaust gas.

The first drainage path 30 is a flow path for the purpose of discharging the water that is stored in the gas/liquid separator 28 to the exterior of the gas/liquid separator 28. A first drainage pump 34 is provided in the first drainage path 30. The first drainage pump 34 delivers the water that is stored in the gas/liquid separator 28 to the water electrolysis system 10.

The fuel cell system 14 is further equipped with a first hydrogen gas supply path 36, a second hydrogen gas supply path 38, a hydrogen gas discharge path 40, a gas/liquid separator 42, and a second drainage path 44. The first hydrogen gas supply path 36 supplies the hydrogen gas that is generated by the water electrolysis system 10 to the gas/liquid separator 42. An on-off valve 46 is provided in the first hydrogen gas supply path 36. The on-off valve 46 opens and closes the first hydrogen gas supply path 36.

The second hydrogen gas supply path 38 connects the gas/liquid separator 42 and the fuel cell stack 16 to each other. The second hydrogen gas supply path 38 introduces the hydrogen gas inside the gas/liquid separator 42 into the fuel cell stack 16. The hydrogen gas discharge path 40 connects the fuel cell stack 16 and the gas/liquid separator 42 to each other. A hydrogen exhaust gas (an off gas) that is discharged from the fuel cell stack 16 flows through the hydrogen gas discharge path 40. The hydrogen exhaust gas contains an unreacted hydrogen gas that has not reacted in the electrical power generating cells 18. Further, the hydrogen exhaust gas also contains moisture that has permeated from the cathodes of the electrical power generating cells 18 through the electrolyte membrane and that is guided to the anodes.

The gas/liquid separator 42 separates, into a gas and a liquid, the hydrogen exhaust gas that is guided from the hydrogen gas discharge path 40. Stated otherwise, the gas/liquid separator 42 removes the water vapor from the hydrogen exhaust gas. The gas/liquid separator 42 stores the water (liquid water) that is separated from the hydrogen exhaust gas.

The second drainage path 44 is a flow path for the purpose of discharging the water that is stored in the gas/liquid separator 42 to the exterior of the gas/liquid separator 42. A second drainage pump 48 is provided in the second drainage path 44. The second drainage pump 48 delivers the water that is stored in the gas/liquid separator 42 to the water electrolysis system 10.

The fuel cell system 14 can be equipped with constituent elements apart from those described above. Specifically, the fuel cell system 14 can be equipped with, for example, a cooling device for allowing a cooling medium to be circulated through the fuel cell stack 16.

The water electrolysis system 10 is equipped with a water electrolysis device 50, a first gas/liquid separator 52, a second gas/liquid separator 54, a water supply flow path 56, a first lead-out flow path 58, an oxygen gas storage unit 60, a second lead-out flow path 62, and a hydrogen gas storage unit 64.

In the water electrolysis device 50, by the water (pure water) being electrolyzed, the oxygen gas and the hydrogen gas are generated. The water electrolysis device 50 includes an equal pressure water electrolysis stack 66, and an electrical power source 68. The equal pressure water electrolysis stack 66 includes a plurality of water electrolysis cells 70, and a pair of end plates 71. The plurality of water electrolysis cells 70 are stacked on one another. The pair of end plates 71 sandwich the plurality of water electrolysis cells 70 therebetween in the stacking direction of the water electrolysis cells 70.

FIG. 2 is a schematic diagram of the water electrolysis cells 70. As shown in FIG. 2, the water electrolysis cells 70 each include an electrolyte membrane 72, a first electrode catalyst layer 74, a second electrode catalyst layer 76, a first current collector 78, a second current collector 80, a first support member 82, and a second support member 84. The electrolyte membrane 72 is an ion exchange membrane that is capable of exchanging ions. The electrolyte membrane 72, for example, is a proton exchange membrane (PEM). The electrolyte membrane 72 may be an anion exchange membrane (AEM).

The first electrode catalyst layer 74 is laminated on one surface of the electrolyte membrane 72. The second electrode catalyst layer 76 is laminated on another surface of the electrolyte membrane 72. The first current collector 78 is laminated on the first electrode catalyst layer 74. The first current collector 78 is formed to be porous. The second current collector 80 is laminated on the second electrode catalyst layer 76. The second current collector 80 is formed to be porous.

The first support member 82 and the second support member 84 sandwich the electrolyte membrane 72 therebetween. A first flow path 86 is formed in the first support member 82. The first flow path 86 is adjacent to the first current collector 78. A second flow path 88 is formed in the second support member 84. The second flow path 88 is adjacent to the second current collector 80. The first flow path 86 and the second flow path 88 are disposed on both sides of the electrolyte membrane 72.

As shown in FIG. 1 and FIG. 2, the electrical power source 68 applies a voltage between the first current collector 78 and the second current collector 80 of the water electrolysis cell 70. The electrical power source 68 is a DC electrical power source. In the equal pressure water electrolysis stack 66, when a voltage is applied between the first current collector 78 and the second current collector 80, the water is subjected to electrolysis, and the oxygen gas is generated in the first flow path 86 and the hydrogen gas is generated in the second flow path 88. When the water electrolysis is carried out, the pressure in the first flow path 86 and the pressure in the second flow path 88 are the same as each other (refer to FIG. 2).

As shown in FIG. 1, the first gas/liquid separator 52 is capable of storing the water. The first drainage path 30 is connected to the first gas/liquid separator 52. Stated otherwise, the first drainage pump 34 delivers the water that is stored in the gas/liquid separator 28 to the first gas/liquid separator 52.

The second gas/liquid separator 54 is capable of storing the water. The second drainage path 44 is connected to the second gas/liquid separator 54. Stated otherwise, the second drainage pump 48 delivers the water that is stored in the gas/liquid separator 42 to the second gas/liquid separator 54. The capacity of the second gas/liquid separator 54 is the same as the capacity of the first gas/liquid separator 52.

The water supply flow path 56 supplies the water to the equal pressure water electrolysis stack 66. The water supply flow path 56 includes a first water supply flow path 90, a second water supply flow path 92, and an introduction flow path 94. The first water supply flow path 90 is connected to the first gas/liquid separator 52. The second water supply flow path 92 is connected to the second gas/liquid separator 54. The introduction flow path 94 is connected to the first water supply flow path 90 and the second water supply flow path 92.

The introduction flow path 94 joins the water that is supplied from the first water supply flow path 90 and the water that is supplied from the second water supply flow path 92, and introduces the joined water into the equal pressure water electrolysis stack 66. A water pump 96 is disposed in the introduction flow path 94. The water pump 96 delivers the water that is stored in the first gas/liquid separator 52 and the water that is stored in the second gas/liquid separator 54 to the equal pressure water electrolysis stack 66. The introduction flow path 94 introduces the water into the first flow path 86. The introduction flow path 94 does not introduce the water into the second flow path 88.

The first lead-out flow path 58 connects the equal pressure water electrolysis stack 66 and the first gas/liquid separator 52 to each other. The first lead-out flow path 58 leads out the oxygen gas that is generated in the first flow path 86 and the unreacted water into the first gas/liquid separator 52. The first lead-out flow path 58 and the first flow path 86 are filled with the water. The first gas/liquid separator 52 separates, from the water, the oxygen gas that is guided from the first flow path 86 of the equal pressure water electrolysis stack 66.

The oxygen gas storage unit 60 stores the oxygen gas that has been separated from the water by the first gas/liquid separator 52. The oxygen gas storage unit 60 includes two oxygen gas tanks 98, an oxygen gas introduction path 100, and an oxygen gas lead-out path 102. The two oxygen gas tanks 98 are disposed in parallel with each other. The capacities of the two oxygen gas tanks 98 are the same. The oxygen gas introduction path 100 connects the first gas/liquid separator 52 to each of the two oxygen gas tanks 98. The oxygen gas lead-out path 102 connects each of the two oxygen gas tanks 98 to the first oxygen gas supply path 22.

The second lead-out flow path 62 connects the equal pressure water electrolysis stack 66 and the second gas/liquid separator 54 to each other. The second lead-out flow path 62 leads out the hydrogen gas that is generated in the second flow path 88 into the second gas/liquid separator 54. The second gas/liquid separator 54 separates, from the water, the hydrogen gas that is guided from the second flow path 88 of the equal pressure water electrolysis stack 66.

The hydrogen gas storage unit 64 stores the hydrogen gas that has been separated from the water by the second gas/liquid separator 54. The hydrogen gas storage unit 64 includes four hydrogen gas tanks 104, a hydrogen gas introduction path 106, and a hydrogen gas lead-out path 108. The four hydrogen gas tanks 104 are disposed in parallel with each other. The capacities of the four hydrogen gas tanks 104 are the same. The capacity of each hydrogen gas tank 104 and the capacity of each oxygen gas tank 98 are the same as each other. More specifically, the capacity of the hydrogen gas storage unit 64 is twice the capacity of the oxygen gas storage unit 60. The hydrogen gas introduction path 106 connects the second gas/liquid separator 54 to each of the four hydrogen gas tanks 104. The hydrogen gas lead-out path 108 connects each of the four hydrogen gas tanks 104 to the first hydrogen gas supply path 36.

The water electrolysis system 10 can be equipped with constituent elements apart from those described above. In the water electrolysis system 10, the water that is stored in the first gas/liquid separator 52 and the water that is filled in the first flow path 86 are connected to each other by the water that is present in the first water supply flow path 90 and the water that is present in the introduction flow path 94. Further, the water that is stored in the first gas/liquid separator 52 and the water that is filled in the first flow path 86 are connected to each other by the water that is present in the first lead-out flow path 58.

The water that is stored in the second gas/liquid separator 54 and the water that is filled in the second flow path 88 are connected to each other by the water that is present in the second lead-out flow path 62. The water that is stored in the first gas/liquid separator 52 and the water that is stored in the second gas/liquid separator 54 are connected to each other by the water that is present in the first water supply flow path 90 and the water that is present in the second water supply flow path 92.

The energy system 12 may include a non-illustrated control device that serves to control the entirety of the fuel cell system 14 and the water electrolysis system 10.

Next, a description will be given concerning the basic operations of the energy system 12. In the water electrolysis system 10, in an initial state prior to the start of water electrolysis, the water that is stored in the second gas/liquid separator 54 flows via the second lead-out flow path 62 into the second flow path 88. More specifically, the second flow path 88 is filled with the water.

In the case that the water electrolysis system 10 is driven, the water pump 96 is driven and a voltage is applied between the first current collector 78 and the second current collector 80 by the electrical power source 68. When the water pump 96 is driven, the water that is stored in the first gas/liquid separator 52 and the water that is stored in the second gas/liquid separator 54 are supplied to the first flow path 86 of the equal pressure water electrolysis stack 66. In accordance therewith, the first flow path 86 is filled with the water.

The water that is introduced into the first flow path 86 is guided via the first current collector 78 to the first electrode catalyst layer 74. In the first electrode catalyst layer 74 (an anode catalyst layer), the water is subjected to electrolysis, and the hydrogen ions and the oxygen gas are generated.

The hydrogen ions move inside the electrolyte membrane 72 together with the water from the first electrode catalyst layer 74 to the second electrode catalyst layer 76 (a cathode catalyst layer). In accordance with this feature, the hydrogen ions are supplied to the second electrode catalyst layer 76, and the electrolyte membrane 72 is humidified. In the second electrode catalyst layer 76, the hydrogen ions combine, and thereby the hydrogen gas is generated.

The unreacted water that is supplied to the first electrode catalyst layer 74 but not reacted, and oxygen gas that is generated in the first electrode catalyst layer 74 are guided from the first flow path 86 via the first lead-out flow path 58 to the first gas/liquid separator 52. The oxygen gas that is guided to the first gas/liquid separator 52 passes through the oxygen gas introduction path 100, and is stored in the oxygen gas tanks 98. By the oxygen gas being introduced into the oxygen gas tanks 98, the pressure of the oxygen gas that is stored in the oxygen gas storage unit 60 can be raised to a predetermined set pressure.

The hydrogen gas that is generated in the second electrode catalyst layer 76 is guided from the second flow path 88 via the second lead-out flow path 62 to the second gas/liquid separator 54. The hydrogen gas that is guided to the second gas/liquid separator 54 passes through the hydrogen gas introduction path 106, and is stored in the hydrogen gas tanks 104. By the hydrogen gas being introduced into the hydrogen gas tanks 104, the pressure of the hydrogen gas that is stored in the hydrogen gas storage unit 64 can be raised to a predetermined set pressure. The pressure of the hydrogen gas that is stored in the hydrogen gas storage unit 64 and the pressure of the oxygen gas that is stored in the oxygen gas storage unit 60 are the same as each other.

In the water electrolysis system 10, the first flow path 86 and the second flow path 88 are each filled with the water when the water is electrolyzed by the equal pressure water electrolysis stack 66. In accordance with this feature, it is possible to suppress a situation in which the generated gases (the oxygen gas and the hydrogen gas) permeate through the electrolyte membrane 72. More specifically, cross leakage of the generated gases can be suppressed.

The ratio of the amount of the hydrogen gas to the amount of the oxygen gas generated by the electrolysis of water in the equal pressure water electrolysis stack 66 is 2 : 1. More specifically, the amount of the hydrogen gas per unit time generated by the equal pressure water electrolysis stack 66 is twice the amount of the oxygen gas per unit time generated by the equal pressure water electrolysis stack 66. In response thereto, the capacity of the hydrogen gas storage unit 64 is twice the capacity of the oxygen gas storage unit 60.

In this case, the force with which the oxygen gas inside the first gas/liquid separator 52 pushes against the water surface and the force with which the hydrogen gas inside the second gas/liquid separator 54 pushes against the water surface can be made the same as each other. Moreover, in the following description, the force with which the oxygen gas inside the first gas/liquid separator 52 pushes against the water surface may be referred to as a "first pushing force", and the force with which the hydrogen gas inside the second gas/liquid separator 54 pushes against the water surface may be referred to as a "second pushing force".

In this manner, the water pressure inside the first flow path 86 and the water pressure inside the second flow path 88 become the same, and even in the case that the electrolyte membrane 72 has deteriorated (for example, tearing or breakage in the electrolyte membrane 72 has occurred), it is possible to suppress a situation in which the generated gases (the hydrogen gas and the oxygen gas) become mixed with each other. Thus, the reliability of the water electrolysis system 10 is enhanced.

Furthermore, the water that is stored in the first gas/liquid separator 52 and the water that is stored in the second gas/liquid separator 54 are connected to each other by the water that is present in the first water supply flow path 90 and the water that is present in the second water supply flow path 92. In this case, since the water level in the first gas/liquid separator 52 and the water level in the second gas/liquid separator 54 change in a manner so that the first pushing force and the second pushing force become the same, the generation of a pressure difference between the first flow path 86 and the second flow path 88 can be suppressed.

In the fuel cell system 14, by the on-off valve 32 opening the first oxygen gas supply path 22, the oxygen gas that is stored in the oxygen gas storage unit 60 is introduced, via the first oxygen gas supply path 22, the gas/liquid separator 28, and the second oxygen gas supply path 24, into the fuel cell stack 16. Further, by the on-off valve 46 opening the first hydrogen gas supply path 36, the hydrogen gas that is stored in the hydrogen gas storage unit 64 is introduced, via the first hydrogen gas supply path 36, the gas/liquid separator 42, and the second hydrogen gas supply path 38, into the fuel cell stack 16.

The fuel cell stack 16 generates electrical power by means of an electrochemical reaction between the hydrogen gas and the oxygen gas. The oxygen exhaust gas is discharged via the oxygen gas discharge path 26 into the gas/liquid separator 28. In the gas/liquid separator 28, the oxygen exhaust gas is separated into a gas and a liquid. The oxygen exhaust gas from which moisture has been removed is guided to the second oxygen gas supply path 24 and is reused. In the case that the water that is stored in the gas/liquid separator 28 is delivered to the first gas/liquid separator 52, the operation of the water electrolysis system 10 is stopped, and the pressure of the oxygen gas inside the first gas/liquid separator 52 is sufficiently reduced.

The hydrogen exhaust gas is discharged via the hydrogen gas discharge path 40 into the gas/liquid separator 42. In the gas/liquid separator 42, the hydrogen exhaust gas is separated into a gas and a liquid. The hydrogen exhaust gas from which moisture has been removed is guided to the second hydrogen gas supply path 38 and is reused. In the case that the water that is stored in the gas/liquid separator 42 is delivered to the second gas/liquid separator 54, the operation of the water electrolysis system 10 is stopped, and the pressure of the hydrogen gas inside the second gas/liquid separator 54 is sufficiently reduced.

According to the present embodiment, since each of the first flow path 86 and the second flow path 88 is filled with the water when the water is electrolyzed by the water electrolysis device 50, a situation in which the generated gases permeate through the electrolyte membrane 72 (i.e., the occurrence of cross leakage) can be suppressed.

Further, the water that is stored in the first gas/liquid separator 52 and the water that is filled in the first flow path 86 are connected to each other, and the water that is stored in the second gas/liquid separator 54 and the water that is filled in the second flow path 88 are connected to each other. In accordance with this feature, by adjusting the force with which the oxygen gas inside the first gas/liquid separator 52 pushes against the water surface and the force with which the hydrogen gas inside the second gas/liquid separator 54 pushes against the water surface, the pressure in the first flow path 86 and the pressure in the second flow path 88 can be made the same as each other. In accordance therewith, even in the case that the electrolyte membrane 72 has deteriorated (for example, tearing or breakage in the electrolyte membrane 72 has occurred), it is possible to suppress a situation in which the generated gases become mixed with each other.

Furthermore, the water electrolysis system 10 is configured in a manner so that the water that is stored in the first gas/liquid separator 52 and the water that is stored in the second gas/liquid separator 54 are capable of communicating with each other. In this case, the water level in the first gas/liquid separator 52 and the water level in the second gas/liquid separator 54 can be adjusted in a manner so that the force with which the oxygen gas pushes against the water that is stored in the first gas/liquid separator 52 and the force with which the hydrogen gas pushes against the water that is stored in the second gas/liquid separator 54 become the same. Thus, a more satisfactory water electrolysis system 10 and a more satisfactory energy system 12 can be obtained.

The water electrolysis system 10 is not necessarily limited to the configuration described above. The capacities of the two oxygen gas tanks 98 need not necessarily be the same. The capacities of the four hydrogen gas tanks 104 need not necessarily be the same. The oxygen gas storage unit 60 may include one or three or more oxygen gas tanks 98. Further, the hydrogen gas storage unit 64 may include one, two, three, or five or more hydrogen gas tanks 104. Further, the capacity of the hydrogen gas storage unit 64 may be the same as or smaller than the capacity of the oxygen gas storage unit 60.

In the water electrolysis system 10, the introduction flow path 94 may introduce the water into the second flow path 88 without introducing the water into the first flow path 86 of the equal pressure water electrolysis stack 66. Further, the introduction flow path 94 may introduce the water into both of the first flow path 86 and the second flow path 88.

First Exemplary Modification

Next, a description will be given concerning a water electrolysis system 10A according to a First Exemplary Modification. In the water electrolysis system 10A according to the First Exemplary Modification, the same constituent elements as those of the above-described water electrolysis system 10 are denoted by the same reference numerals, and detailed description thereof will be omitted. In the present exemplary modification, concerning the same constituent elements as those of the above-described water electrolysis system 10, the same advantageous effects are realized.

FIG. 3 is a schematic diagram of the energy system 12 equipped with the water electrolysis system 10A according to the First Exemplary Modification. As shown in FIG. 3, the water electrolysis system 10A is equipped with the water electrolysis device 50, a first gas/liquid separator 52a, a second gas/liquid separator 54a, a water supply flow path 56a, a first lead-out flow path 58a, and a second lead-out flow path 62a.

The first gas/liquid separator 52a includes two first tank portions 110, and an oxygen gas lead-out path 112. The first tank portions 110 are capable of storing water. The first tank portions 110 also function as oxygen gas tanks 98a that store the oxygen gas. More specifically, the first gas/liquid separator 52a also functions as an oxygen gas storage unit 60a that stores the oxygen gas. The two first tank portions 110 are disposed in parallel with each other. The capacities of the two first tank portions 110 are the same. The oxygen gas lead-out path 112 connects each of the two first tank portions 110 to the first oxygen gas supply path 22. The oxygen gases that are stored in the respective first tank portions 110 communicate with each other via the oxygen gas lead-out path 112.

The second gas/liquid separator 54a includes four second tank portions 114, and a hydrogen gas lead-out path 116. The second tank portions 114 are capable of storing water. The second tank portions 114 also function as hydrogen gas tanks 104a that store the hydrogen gas. More specifically, the second gas/liquid separator 54a also functions as a hydrogen gas storage unit 64a that stores the hydrogen gas. The four second tank portions 114 are disposed in parallel with each other. The capacities of the four second tank portions 114 are the same. The hydrogen gas lead-out path 116 connects each of the four second tank portions 114 to the first hydrogen gas supply path 36. The hydrogen gases that are stored in the respective second tank portions 114 communicate with each other via the hydrogen gas lead-out path 116.

The pressure of the hydrogen gas that is stored in the second gas/liquid separator 54a and the pressure of the oxygen gas that is stored in the first gas/liquid separator 52a are the same as each other.

The water supply flow path 56a includes a first water supply flow path 90a, a second water supply flow path 92a, a connecting flow path 118, and an introduction flow path 94a. The first water supply flow path 90a connects the two first tank portions 110 to each other. In accordance with this feature, the waters that are stored in the first tank portions 110 are connected to each other via the water that is present in the first water supply flow path 90a. The second water supply flow path 92a connects the four second tank portions 114 to each other. In accordance with this feature, the waters that are stored in the second tank portions 114 are connected to each other via the water that is present in the second water supply flow path 92a.

The connecting flow path 118 connects the first water supply flow path 90a and the second water supply flow path 92a to each other. In accordance with this feature, the water that is stored in each of the first tank portions 110 and the water that is stored in each of the second tank portions 114 are connected to each other. The introduction flow path 94a connects the second water supply flow path 92a and the equal pressure water electrolysis stack 66 to each other. The water pump 96 is disposed in the introduction flow path 94a.

The water pump 96 delivers the water that is stored in the first tank portions 110 and the water that is stored in the second tank portions 114 to the equal pressure water electrolysis stack 66. The introduction flow path 94a introduces the water into the first flow path 86 of the equal pressure water electrolysis stack 66. The introduction flow path 94a does not introduce the water into the second flow path 88 of the equal pressure water electrolysis stack 66.

The first lead-out flow path 58a leads out the oxygen gas that is generated in the first flow path 86 and the unreacted water into the first tank portions 110. The second lead-out flow path 62a leads out the hydrogen gas that is generated in the second flow path 88 into the second tank portions 114.

The first flow path 86 and the second flow path 88 are each filled with the water. The water that is stored in the first tank portions 110 and the water that is filled in the first flow path 86 are connected to each other by the water that is present in the water supply flow path 56a. Further, the water that is stored in the first tank portions 110 and the water that is filled in the first flow path 86 are connected to each other by the water that is present in the first lead-out flow path 58a. The water that is stored in the second tank portions 114 and the water that is filled in the second flow path 88 are connected to each other by the water that is present in the second lead-out flow path 62a.

According to the present exemplary modification, the force (the first pushing force) with which the oxygen gas that is stored in the two oxygen gas tanks 98a pushes against the water surface and the force (the second pushing force) with which the hydrogen gas that is stored in the four hydrogen gas tanks 104a pushes against the water surface are the same as each other. Therefore, the pressure in the first flow path 86 and the pressure in the second flow path 88 can be made the same as each other. Thus, the same advantageous effects as those of the above-described water electrolysis system 10 are achieved.

According to the present exemplary modification, the first gas/liquid separator 52a functions as the oxygen gas storage unit 60a, and the second gas/liquid separator 54a functions as the hydrogen gas storage unit 64a, thereby enabling the water electrolysis system 10A to have a compact configuration.

The water electrolysis system 10A is not necessarily limited to the configuration described above. The capacities of the two first tank portions 110 need not necessarily be the same. The capacities of the four second tank portions 114 need not necessarily be the same. The first gas/liquid separator 52a may include one or three or more first tank portions 110. Further, the second gas/liquid separator 54a may include one, two, three, or five or more second tank portions 114. The capacity of the second gas/liquid separator 54a may be the same as or smaller than the capacity of the first gas/liquid separator 52a.

In the water electrolysis system 10A, the introduction flow path 94a may introduce the water into the second flow path 88 without introducing the water into the first flow path 86 of the equal pressure water electrolysis stack 66. Further, the introduction flow path 94a may introduce the water into both of the first flow path 86 and the second flow path 88.

Second Exemplary Modification

Next, a description will be given concerning a water electrolysis system 10B according to a Second Exemplary Modification. In the water electrolysis system 10B according to the Second Exemplary Modification, the same constituent elements as those of the above-described water electrolysis systems 10 and 10A are denoted by the same reference numerals, and detailed description thereof will be omitted. In the present exemplary modification, concerning the same constituent elements as those of the above-described water electrolysis systems 10 and 10A, the same advantageous effects are realized.

FIG. 4 is a schematic diagram of the energy system 12 equipped with the water electrolysis system 10B according to the Second Exemplary Modification. As shown in FIG. 4, the water electrolysis system 10B is equipped with the water electrolysis device 50, a first gas/liquid separator 52b, a second gas/liquid separator 54b, a water supply flow path 56b, a first lead-out flow path 58b, an oxygen gas storage unit 60b, a second lead-out flow path 62b, and a hydrogen gas storage unit 64b.

The capacity of the second gas/liquid separator 54b is larger than the capacity of the first gas/liquid separator 52b. Specifically, the capacity of the second gas/liquid separator 54b is twice the capacity of the first gas/liquid separator 52b.

The water supply flow path 56b includes a first water supply flow path 90b, a second water supply flow path 92b, and an introduction flow path 94b. The first water supply flow path 90b is connected to the first gas/liquid separator 52b. The second water supply flow path 92b is connected to the second gas/liquid separator 54b. The introduction flow path 94b is connected to the first water supply flow path 90b and the second water supply flow path 92b.

The introduction flow path 94b joins the water that is supplied from the first water supply flow path 90b and the water that is supplied from the second water supply flow path 92b to flow together, and introduces the joined water into the equal pressure water electrolysis stack 66. The water pump 96 is disposed in the introduction flow path 94b. The water pump 96 delivers the water that is stored in the first gas/liquid separator 52b and the water that is stored in the second gas/liquid separator 54b to the equal pressure water electrolysis stack 66. The introduction flow path 94b introduces the water into the first flow path 86. The introduction flow path 94b does not introduce the water into the second flow path 88.

The first lead-out flow path 58b leads out the oxygen gas that is generated in the first flow path 86 and the unreacted water into the first gas/liquid separator 52b. The second lead-out flow path 62b leads out the hydrogen gas that is generated in the second flow path 88 into the second gas/liquid separator 54b.

The oxygen gas storage unit 60b is configured in the same manner as the above-described oxygen gas storage unit 60. A first back pressure valve 122 is disposed in the oxygen gas introduction path 100 of the oxygen gas storage unit 60b. The first back pressure valve 122 opens in the case that the pressure of the oxygen gas inside the first gas/liquid separator 52b is greater than or equal to a predetermined oxygen gas pressure threshold value. The first back pressure valve 122 closes in the case that the pressure of the oxygen gas inside the first gas/liquid separator 52b is less than the oxygen gas pressure threshold value.

The hydrogen gas storage unit 64b is configured in the same manner as the above-described hydrogen gas storage unit 64. The hydrogen gas storage unit 64b includes two hydrogen gas tanks 104. Further, a second back pressure valve 124 is disposed in the hydrogen gas introduction path 106 of the hydrogen gas storage unit 64b. The second back pressure valve 124 opens in the case that the pressure of the hydrogen gas inside the second gas/liquid separator 54b is greater than or equal to a predetermined hydrogen gas pressure threshold value. The second back pressure valve 124 closes in the case that the pressure of the hydrogen gas inside the second gas/liquid separator 54b is less than the hydrogen gas pressure threshold value. In the water electrolysis system 10B, the pressure of the hydrogen gas that is stored in the hydrogen gas storage unit 64b is higher than the pressure of the oxygen gas that is stored in the oxygen gas storage unit 60b.

In the water electrolysis system 10B, since the capacity of the second gas/liquid separator 54b is twice the capacity of the first gas/liquid separator 52b, the pressure of the oxygen gas inside the first gas/liquid separator 52b and the pressure of the hydrogen gas inside the second gas/liquid separator 54b can be made the same as each other. Therefore, the pressure in the first flow path 86 and the pressure in the second flow path 88 can be made the same as each other. Accordingly, the same advantageous effects as those of the above-described water electrolysis system 10 are achieved.

The water electrolysis system 10B is not necessarily limited to the configuration described above. The oxygen gas storage unit 60b may include one or three or more oxygen gas tanks 98. Further, the hydrogen gas storage unit 64b may include one or three or more hydrogen gas tanks 104. The capacity of the second gas/liquid separator 54b may be the same as or smaller than the capacity of the first gas/liquid separator 52b.

In the water electrolysis system 10B, the introduction flow path 94b may introduce the water into the second flow path 88 without introducing the water into the first flow path 86 of the equal pressure water electrolysis stack 66. Further, the introduction flow path 94b may introduce the water into both of the first flow path 86 and the second flow path 88.

Third Exemplary Modification

Next, a description will be given concerning a water electrolysis system 10C according to a Third Exemplary Modification. In the water electrolysis system 10C according to the Third Exemplary Modification, the same constituent elements as those of the above-described water electrolysis systems 10, 10A, and 10B are denoted by the same reference numerals, and detailed description thereof will be omitted. In the present exemplary modification, concerning the same constituent elements as those of the above-described water electrolysis systems 10, 10A, and 10B, the same advantageous effects are realized.

FIG. 5 is a schematic diagram of the energy system 12 equipped with the water electrolysis system 10C according to the Third Exemplary Modification. As shown in FIG. 5, the water electrolysis system 10C is equipped with the water electrolysis device 50, a first gas/liquid separator 52c, a second gas/liquid separator 54c, a water supply flow path 56c, a first lead-out flow path 58c, an oxygen gas storage unit 60c, a second lead-out flow path 62c, and a hydrogen gas storage unit 64c.

The capacity of the first gas/liquid separator 52c and the capacity of the second gas/liquid separator 54c are the same as each other. The water supply flow path 56c includes a first water supply flow path 90c, a second water supply flow path 92c, and an introduction flow path 94c. The first water supply flow path 90c is connected to the first gas/liquid separator 52c.

The second water supply flow path 92c is connected to the second gas/liquid separator 54c. The introduction flow path 94c is connected to the first water supply flow path 90c and the second water supply flow path 92c. The water pump 96 is disposed in the introduction flow path 94c. The introduction flow path 94c supplies the water to both of the first flow path 86 and the second flow path 88. The first flow path 86 and the second flow path 88 are filled with the water.

The first lead-out flow path 58c leads out the oxygen gas that is generated in the first flow path 86 and the unreacted water into the first gas/liquid separator 52c. The second lead-out flow path 62c leads out the hydrogen gas that is generated in the second flow path 88 into the second gas/liquid separator 54c.

According to the present exemplary modification, the water level in the second gas/liquid separator 54c is lower than the water level in the first gas/liquid separator 52c. In accordance with this feature, the space within the second gas/liquid separator 54c in which the hydrogen gas can be accommodated can be made larger than the space within the first gas/liquid separator 52c in which the oxygen gas can be accommodated. Therefore, the first pressing force and the second pressing force can be made the same as each other. Accordingly, the same advantageous effects as those of the above-described water electrolysis system 10 are achieved.

The water electrolysis system 10C is not necessarily limited to the configuration described above. The oxygen gas storage unit 60c may include one or three or more oxygen gas tanks 98. Further, the hydrogen gas storage unit 64c may include one or three or more hydrogen gas tanks 104. The capacity of the second gas/liquid separator 54c may be larger than or smaller than the capacity of the first gas/liquid separator 52c.

Fourth Exemplary Modification

Next, a description will be given concerning a water electrolysis system 10D according to a Fourth Exemplary Modification. In the water electrolysis system 10D according to the Fourth Exemplary Modification, the same constituent elements as those of the above-described water electrolysis systems 10, and 10A to 10C are denoted by the same reference numerals, and detailed description thereof will be omitted. In the present exemplary modification, concerning the same constituent elements as those of the above-described water electrolysis systems 10, and 10A to 10C, the same advantageous effects are realized.

FIG. 6 is a schematic diagram of the energy system 12 equipped with the water electrolysis system 10D according to the Fourth Exemplary Modification. As shown in FIG. 6, the water electrolysis system 10D is equipped with the water electrolysis device 50, a first gas/liquid separator 52d, a second gas/liquid separator 54d, a water supply flow path 56d, a first lead-out flow path 58d, an oxygen gas storage unit 60d, a second lead-out flow path 62d, a hydrogen gas storage unit 64d, and a communication path 132.

The capacity of the second gas/liquid separator 54d is twice the capacity of the first gas/liquid separator 52d. The water supply flow path 56d includes a first introduction flow path 134, and a second introduction flow path 136. The first introduction flow path 134 connects the first gas/liquid separator 52d and the equal pressure water electrolysis stack 66 to each other. A water pump 138 is disposed in the first introduction flow path 134. The water pump 138 delivers the water that is stored in the first gas/liquid separator 52d to the first flow path 86 of the equal pressure water electrolysis stack 66.

The second introduction flow path 136 connects the second gas/liquid separator 54d and the equal pressure water electrolysis stack 66 to each other. A water pump 140 is disposed in the second introduction flow path 136. The water pump 140 delivers the water that is stored in the second gas/liquid separator 54d to the second flow path 88 of the equal pressure water electrolysis stack 66.

The first flow path 86 is filled with the water that is supplied from the first introduction flow path 134. The first lead-out flow path 58d leads out the oxygen gas that is generated in the first flow path 86 and the unreacted water into the first gas/liquid separator 52d. The second flow path 88 is filled with the water that is supplied from the second introduction flow path 136. The second lead-out flow path 62d leads out the hydrogen gas that is generated in the second flow path 88 and the unreacted water into the second gas/liquid separator 54d.

In the water electrolysis system 10D, the first back pressure valve 122 and the second back pressure valve 124 as shown in FIG. 4 are not provided. Therefore, the pressure of the oxygen gas inside the first gas/liquid separator 52d is the same as the pressure of the oxygen gas inside each of the oxygen gas tanks 98. Further, the pressure of the hydrogen gas inside the second gas/liquid separator 54d is the same as the pressure of the hydrogen gas inside each of the hydrogen gas tanks 104. Therefore, the pressure of the hydrogen gas inside the second gas/liquid separator 54d becomes twice the pressure of the oxygen gas inside the first gas/liquid separator 52d.

The communication path 132 causes the water that is stored in the first gas/liquid separator 52d and the water that is stored in the second gas/liquid separator 54d to communicate with each other. An on-off valve 142 is disposed in the communication path 132. The on-off valve 142 opens and closes the communication path 132.

In the water electrolysis system 10D, in an initial state prior to the start of water electrolysis, the pressure inside the first gas/liquid separator 52d and the pressure inside the second gas/liquid separator 54d are the same as each other. In the water electrolysis system 10D, in the initial state of the water electrolysis system 10D, by the on-off valve 142 opening the communication path 132, the water level in the first gas/liquid separator 52d and the water level in the second gas/liquid separator 54d are set to the same position. Thereafter, in a state with the on-off valve 142 having closed the communication path 132, the water electrolysis is started by the equal pressure water electrolysis stack 66.

In the present exemplary modification, since the capacity of the second gas/liquid separator 54d is twice the capacity of the first gas/liquid separator 52d, the force (the first pushing force) with which the oxygen gas inside the first gas/liquid separator 52d pushes against the water surface and the force (the second pushing force) with which the hydrogen gas inside the second gas/liquid separator 54d pushes against the water surface can be made the same as each other. Therefore, the same advantageous effects as those of the above-described water electrolysis system 10 are achieved.

According to the present exemplary modification, the water supply flow path 56d includes the first introduction flow path 134 that introduces the water that is stored in the first gas/liquid separator 52d into the first flow path 86, and the second introduction flow path 136 that introduces the water that is stored in the second gas/liquid separator 54d into the second flow path 88. The water electrolysis system 10D is further equipped with the communication path 132 for causing the water that is stored in the first gas/liquid separator 52d and the water that is stored in the second gas/liquid separator 54d to communicate with each other, and the on-off valve 142 that opens and closes the communication path 132.

In accordance with such a configuration, by the on-off valve 142 opening the communication path 132, the water level in the first gas/liquid separator 52d and the water level in the second gas/liquid separator 54d can be adjusted.

The water electrolysis system 10D is not necessarily limited to the configuration described above. The oxygen gas storage unit 60d may include one or three or more oxygen gas tanks 98. Further, the hydrogen gas storage unit 64d may include one or three or more hydrogen gas tanks 104. The capacity of the second gas/liquid separator 54d may be the same as or smaller than the capacity of the first gas/liquid separator 52d.

Fifth Exemplary Modification

Next, a description will be given concerning a water electrolysis system 10E according to a Fifth Exemplary Modification. In the water electrolysis system 10E according to the Fifth Exemplary Modification, the same constituent elements as those of the above-described water electrolysis systems 10, and 10A to 10D are denoted by the same reference numerals, and detailed description thereof will be omitted. In the present exemplary modification, concerning the same constituent elements as those of the above-described water electrolysis systems 10, and 10A to 10D, the same advantageous effects are realized.

FIG. 7 is a schematic diagram of the energy system 12 equipped with the water electrolysis system 10E according to the Fifth Exemplary Modification. As shown in FIG. 7, the water electrolysis system 10E is equipped with the water electrolysis device 50, a first gas/liquid separator 52e, a second gas/liquid separator 54e, a water supply flow path 56e, a first lead-out flow path 58e, a second lead-out flow path 62e, and a communication path 132a.

The first gas/liquid separator 52e is configured in the same manner as the above-described first gas/liquid separator 52a (refer to FIG. 3). The second gas/liquid separator 54e is configured in the same manner as the above-described second gas/liquid separator 54a (refer to FIG. 3). The second gas/liquid separator 54e includes two second tank portions 114.

The water supply flow path 56e includes a first introduction flow path 134a, and a second introduction flow path 136a. The first introduction flow path 134a connects the two first tank portions 110 and the equal pressure water electrolysis stack 66 to each other. The water pump 138 is disposed in the first introduction flow path 134a. The water pump 138 delivers the water that is stored in the first gas/liquid separator 52e to the first flow path 86 of the equal pressure water electrolysis stack 66.

The second introduction flow path 136a connects the two second tank portions 114 and the equal pressure water electrolysis stack 66 to each other. The water pump 140 is disposed in the second introduction flow path 136a. The water pump 140 delivers the water that is stored in the second gas/liquid separator 54e to the second flow path 88 of the equal pressure water electrolysis stack 66.

The first flow path 86 is filled with the water that is supplied from the first introduction flow path 134a. The first lead-out flow path 58e leads out the oxygen gas that is generated in the first flow path 86 and the unreacted water into the first gas/liquid separator 52e. The second flow path 88 is filled with the water that is supplied from the second introduction flow path 136a.

The communication path 132a connects the first introduction flow path 134a and the second introduction flow path 136a to each other. The communication path 132a can cause the water that is stored in the first gas/liquid separator 52e and the water that is stored in the second gas/liquid separator 54e to communicate with each other. The on-off valve 142 is disposed in the communication path 132a. The on-off valve 142 opens and closes the communication path 132a.

In the water electrolysis system 10E, after the fuel cell stack 16 has started generating electrical power, the on-off valve 142 is controlled and opens the communication path 132a. More specifically, in the water electrolysis system 10E, after the pressure of the oxygen gas inside the first gas/liquid separator 52e and the pressure of the hydrogen gas inside the second gas/liquid separator 54e have decreased, the on-off valve 142 opens the communication path 132a.

According to the present exemplary modification, in a state in which the communication path 132a is opened by the on-off valve 142, the water level in the second gas/liquid separator 54e becomes lower than the water level in the first gas/liquid separator 52e. In accordance with this feature, the space within the second gas/liquid separator 54e in which the hydrogen gas can be accommodated can be made larger than the space within the first gas/liquid separator 52e in which the oxygen gas can be accommodated. Therefore, the first pressing force and the second pressing force can be made the same as each other. Accordingly, the same advantageous effects as those of the above-described water electrolysis system 10 are achieved.

The water electrolysis system 10E is not necessarily limited to the configuration described above. The capacities of the two first tank portions 110 need not necessarily be the same. The capacities of the two second tank portions 114 need not necessarily be the same. The first gas/liquid separator 52e may include one or three or more first tank portions 110. Further, the second gas/liquid separator 54e may include one or three or more second tank portions 114. The capacity of the second gas/liquid separator 54e may be larger than or smaller than the capacity of the first gas/liquid separator 52e.

Concerning the above-described embodiments, the following supplementary notes are further disclosed.

Supplementary Note 1

The water electrolysis system (10, 10A to 10E) according to the present disclosure includes: the water electrolysis device (50) including the electrolyte membrane (72), and the first flow path (86) and the second flow path (88) that are disposed on both sides of the electrolyte membrane, the water electrolysis device generating the oxygen gas in the first flow path and generating the hydrogen gas in the second flow path by electrolyzing the water; the first gas/liquid separator (52, 52a to 52e) and the second gas/liquid separator (54, 54a to 54e) that are capable of storing the water; the water supply flow path (56, 56a to 56e) for supplying, to the water electrolysis device, the water that is stored in the first gas/liquid separator and the water that is stored in the second gas/liquid separator; the first lead-out flow path (58, 58a to 58e) that leads out the oxygen gas that is generated in the first flow path into the first gas/liquid separator; and the second lead-out flow path (62, 62a to 62e) that leads out the hydrogen gas that is generated in the second flow path into the second gas/liquid separator, wherein the first flow path and the second flow path are each filled with the water when the water is electrolyzed by the water electrolysis device, the water that is stored in the first gas/liquid separator and the water that is filled in the first flow path are connected to each other, and the water that is stored in the second gas/liquid separator and the water that is filled in the second flow path are connected to each other, and the water electrolysis system is configured to allow the water that is stored in the first gas/liquid separator and the water that is stored in the second gas/liquid separator to communicate with each other.

In accordance with such a configuration, since each of the first flow path and the second flow path is filled with the water when the water is electrolyzed by the water electrolysis device, a situation in which the generated gases permeate through the electrolyte membrane (i.e., the occurrence of cross leakage) can be suppressed.

Further, the water that is stored in the first gas/liquid separator and the water that is filled in the first flow path are connected to each other, and the water that is stored in the second gas/liquid separator and the water that is filled in the second flow path are connected to each other. In accordance with this feature, by adjusting the force (the first pushing force) with which the oxygen gas inside the first gas/liquid separator pushes against the water surface and the force (the second pushing force) with which the hydrogen gas inside the second gas/liquid separator pushes against the water surface, the pressure in the first flow path and the pressure in the second flow path can be made the same as each other. In accordance therewith, even in the case that the electrolyte membrane has deteriorated (for example, tearing or breakage in the electrolyte membrane 72 has occurred), it is possible to suppress a situation in which the generated gases become mixed with each other.

Furthermore, the water electrolysis system is configured to allow the water that is stored in the first gas/liquid separator and the water that is stored in the second gas/liquid separator to communicate with each other. In this case, the water level in the first gas/liquid separator and the water level in the second gas/liquid separator can be adjusted in a manner so that the first pushing force and the second pushing force become the same. Thus, a more satisfactory water electrolysis system can be obtained.

Supplementary Note 2

In the water electrolysis system according to Supplementary Note 1, the water supply flow path may include the first water supply flow path (90, 90a to 90c) that is connected to the first gas/liquid separator, the second water supply flow path (92, 92a to 92c) that is connected to the second gas/liquid separator, and the introduction flow path (94, 94a to 94c) that is connected to the first water supply flow path and the second water supply flow path, and that serves to join the water that is supplied from the first water supply flow path and the water that is supplied from the second water supply flow path, and to introduce the joined water into the water electrolysis device.

In accordance with such a configuration, by means of a simple configuration, the water that is stored in the first gas/liquid separator and the water that is stored in the second gas/liquid separator can be brought into communication with each other.

Supplementary Note 3

In the water electrolysis system according to Supplementary Note 2, the introduction flow path may introduce the water into only one flow path among the first flow path and the second flow path, the water that is introduced into the one flow path may be introduced into one gas/liquid separator among the first gas/liquid separator and the second gas/liquid separator, and the water that is present in another flow path among the first flow path and the second flow path may be connected, via either the first lead-out flow path or the second lead-out flow path, to the water that is stored in another gas/liquid separator among the first gas/liquid separator and the second gas/liquid separator.

In accordance with such a configuration, even in the case that the water is introduced into only one of the first flow path or the second flow path, the first flow path and the second flow path can be filled with the water.

Supplementary Note 4

In the water electrolysis system according to Supplementary Note 2 or 3, the introduction flow path may introduce the water into both of the first flow path and the second flow path, the water that is introduced from the introduction flow path into the first flow path may flow via the first lead-out flow path into the first gas/liquid separator, and the water that is introduced from the introduction flow path into the second flow path may flow via the second lead-out flow path into the second gas/liquid separator.

In accordance with such a configuration, the first flow path and the second flow path can be easily filled with the water.

Supplementary Note 5

In the water electrolysis system according to Supplementary Note 1, the water supply flow path may include the first introduction flow path (134, 134a) that introduces the water that is stored in the first gas/liquid separator into the first flow path, and the second introduction flow path (136, 136a) that introduces the water that is stored in the second gas/liquid separator into the second flow path, and the water electrolysis system may further include the communication path (132, 132a) for causing the water that is stored in the first gas/liquid separator and the water that is stored in the second gas/liquid separator to communicate with each other, and the on-off valve (142) that opens and closes the communication path.

In accordance with such a configuration, by the on-off valve opening the communication path, the water level in the first gas/liquid separator and the water level in the second gas/liquid separator can be adjusted.

Supplementary Note 6

In the water electrolysis system according to any one of Supplementary Notes 1 to 5, the capacity of the second gas/liquid separator may be larger than the capacity of the first gas/liquid separator.

In accordance with such a configuration, it becomes easier for the first pressing force and the second pressing force to be made the same as each other.

Supplementary Note 7

The water electrolysis system according to any one of Supplementary Notes 1 to 6 may further include the oxygen gas storage unit (60) that communicates with the first gas/liquid separator and serves to store the oxygen gas, and the hydrogen gas storage unit (64) that communicates with the second gas/liquid separator and serves to store the hydrogen gas, wherein the capacity of the hydrogen gas storage unit may be larger than the capacity of the oxygen gas storage unit.

In accordance with such a configuration, it becomes easier for the first pressing force and the second pressing force to be made the same as each other.

Supplementary Note 8

The energy system (12) according to the present disclosure includes the water electrolysis system according to any one of Supplementary Notes 1 to 7, and the fuel cell system (14) that is configured to generate the electrical power by using the hydrogen gas and the oxygen gas that are generated by the water electrolysis system, wherein the water that is generated when the fuel cell system generates the electrical power is supplied to at least one of the first gas/liquid separator or the second gas/liquid separator.

In accordance with such a configuration, an energy system that exhibits the advantageous effects described in Supplementary Notes 1 to 7 can be obtained.

Although the present disclosure has been described in detail, the present disclosure is not necessarily limited to the individual embodiments described above. These embodiments can be subjected to various additions, substitutions, modifications, partial deletions and the like, withing a range that does not depart from the essence and gist of the present disclosure, or alternatively, the spirit and gist of the present disclosure as derived from the contents described in the claims and their equivalents. Further, these embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of the operations and the order of the processes are shown merely as examples, and the present disclosure is not necessarily limited to these examples. The same applies also in the case that numerical values or mathematical expressions are used in the description of the aforementioned embodiments.