Water electrolysis device and water electrolysis system using the same

Abstract

To provide a water electrolysis apparatus capable of downsizing a system.SOLUTION: A water electrolysis apparatus comprises a water electrolysis stack provided with a cell laminate obtained by laminating a plurality of water electrolysis cells, and a drainpipe connected to the water electrolysis stack. The water electrolysis stack comprises: a hydrogen electrode side manifold whose hydrogen generated by water electrolysis is circulated; an oxygen electrode side manifold whose oxygen generated by the water electrolysis is circulated; and a water supply manifold whose water used for the water electrolysis is circulated. The hydrogen electrode side manifold and the oxygen electrode side manifold pass therethrough in a lamination direction. The drainpipe comprises a hydrogen electrode side drainpipe connected to the hydrogen electrode side manifold, an oxygen electrode side drainpipe connected to the oxygen electrode side manifold, and a connection pipe by which the hydrogen electrode side drainpipe and the oxygen electrode side drainpipe are connected. The connection pipe comprises a drain valve for adjusting flow of water that circulates the connection pipe.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present application relates to a water electrolysis device and a water electrolysis system using the same. [Background technology]

[0002] A water electrolysis cell includes a membrane electrode assembly and a pair of separators disposed on both sides of the membrane electrode assembly. The membrane electrode assembly includes a solid electrolyte layer, an oxygen electrode catalyst layer disposed on one side of the solid electrolyte layer, and a hydrogen electrode catalyst layer disposed on the other side of the solid electrolyte layer. A water electrolysis device typically includes a water electrolysis stack in which multiple such water electrolysis cells are stacked.

[0003] The water electrolysis stack includes a water supply manifold for supplying water to be used in water electrolysis, a hydrogen electrode side manifold for circulating hydrogen produced by water electrolysis, and an oxygen electrode side manifold for circulating oxygen produced by water electrolysis. The water electrolysis reaction is carried out as follows: First, water is supplied to the water supply manifold, and then to the oxygen electrode catalyst layer of each cell. Then, a voltage is applied across the water electrolysis stack to cause the water electrolysis reaction. As a result, water is decomposed in the oxygen electrode catalyst layer to produce oxygen and protons. The oxygen is extracted through the oxygen electrode side manifold. The protons permeate the solid electrolyte layer and combine with electrons in the hydrogen electrode catalyst layer to produce hydrogen. The hydrogen is extracted through the hydrogen electrode side manifold.

[0004] Water electrolysis devices including such water electrolysis stacks are described, for example, in Patent Documents 1 and 2. Patent Document 1 discloses a water electrolysis device including an oxygen path, a hydrogen path, and two pure water paths. Patent Document 1 also discloses a configuration in which openings are provided only on the upper side of each path.

[0005] Patent Document 2 discloses a water electrolysis apparatus equipped with exhaust manifolds, hydrogen manifolds, and water supply manifolds. The exhaust manifolds are for discharging oxygen and water, the hydrogen manifolds are for circulating hydrogen produced by a reaction, and the water supply manifolds for supplying water. Because the hydrogen manifolds are located on protruding portions that protrude from the water electrolysis stack, they are exposed to the external atmosphere and cooled, causing the moisture contained in the hydrogen to condense. The condensed moisture is stored in a water reservoir located below the hydrogen manifolds. Meanwhile, hydrogen is extracted from an opening located above the hydrogen manifolds. Thus, the hydrogen manifolds described in Patent Document 2 have a gas-liquid separation function. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-164391 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-189689 Summary of the Invention [Problem to be solved by the invention]

[0007] In the water electrolysis device of Patent Document 1, the openings of all the paths (manifolds) are provided only on the upper side, so that unreacted water tends to remain in the water electrolysis stack and be easily blown up upward, resulting in a considerable amount of water flowing out downstream of the water electrolysis device, and therefore requiring the installation of a large gas-liquid separator.

[0008] Patent Document 2 describes that by providing the hydrogen communicating holes of a water electrolysis device with a gas-liquid separation function, it is not necessary to provide a separate gas-liquid separator on the hydrogen electrode side, thereby achieving the effect of reducing the size of the entire system. However, the water electrolysis device of Patent Document 2 discharges oxygen and water through the discharge communicating holes, which requires the installation of a large gas-liquid separator downstream.

[0009] In view of the above circumstances, a main object of the present disclosure is to provide a water electrolysis device that allows the system to be downsized, and a water electrolysis system using the same. [Means for solving the problem]

[0010] In one aspect of the present disclosure to solve the above-described problems, there is provided a water electrolysis stack including a cell stack formed by stacking a plurality of water electrolysis cells, and a drain pipe connected to the water electrolysis stack, wherein the water electrolysis stack includes a hydrogen electrode-side manifold through which hydrogen produced by water electrolysis flows, an oxygen electrode-side manifold through which oxygen produced by water electrolysis flows, and a water supply manifold through which water used for water electrolysis flows, the hydrogen electrode-side manifold and the oxygen electrode-side manifold penetrating in the stacking direction, and the drain pipe includes a hydrogen electrode-side drain pipe connected to the hydrogen electrode-side manifold, and an oxygen electrode-side drain pipe connected to the oxygen electrode-side manifold. Simple pole The water electrolysis device includes an oxygen electrode side drain pipe connected to a side manifold, and a connecting pipe connecting the hydrogen electrode side drain pipe and the oxygen electrode side drain pipe, and the connecting pipe is equipped with a drain valve for adjusting the flow rate of water flowing through the connecting pipe.

[0011] In the water electrolysis apparatus, the connecting pipe may be inclined. The oxygen electrode-side drain pipe may be provided with a water level gauge. Furthermore, the number of hydrogen electrode-side manifolds may be two or more times the number of oxygen electrode-side manifolds.

[0012] In one aspect of the present disclosure for solving the above-described problems, there is provided a water electrolysis device comprising: the water electrolysis device; a power source for applying a voltage to the water electrolysis device; a water supply device for supplying water to the water electrolysis device; Place and a water supply device, and for passing water supplied from the water supply device to the water electrolysis device; a water discharge flow path connected to the water electrolysis device, and for passing water discharged from the water electrolysis device; a hydrogen tank for storing hydrogen produced by water electrolysis; a hydrogen distribution flow path connecting the water electrolysis device and the hydrogen tank, and for passing hydrogen supplied from the water electrolysis device to the hydrogen tank; and an oxygen distribution flow path connected to the water electrolysis device, and for passing oxygen produced by the water electrolysis reaction. [Effects of the Invention]

[0013] In the water electrolysis apparatus of the present disclosure, the oxygen electrode-side manifold and the hydrogen electrode-side manifold are through-holes and have a gas-liquid separation function, which allows the size or elimination of the gas-liquid separators arranged on the oxygen electrode side and the hydrogen electrode side, thereby enabling the size of the entire water electrolysis system to be reduced.

[0014] According to the water electrolysis system of the present disclosure, the water electrolysis device is included, and therefore the entire system can be made smaller. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view of a water electrolysis device 100. [Figure 2] FIG. 1 is an exploded perspective view of a water electrolysis cell 10. [Figure 3] FIG. 1 is a schematic diagram focusing on a drain pipe 40. [Figure 4] 10 is an example of a time chart when adjusting the water level of a drainage pipe using a water level gauge. [Figure 5] FIG. 1 is a block diagram of a water electrolysis system 1000. DETAILED DESCRIPTION OF THE INVENTION

[0016] [Water electrolysis device] The water electrolysis apparatus of the present disclosure will be described using a water electrolysis apparatus 100 as one embodiment. Fig. 1 shows a perspective view of the water electrolysis apparatus 100. For convenience, in Fig. 1, the movement of water is indicated by solid arrows, the movement of oxygen by dotted arrows, and the movement of hydrogen by dashed arrows. This also applies to Figs. 2, 3, and 5.

[0017] As shown in Fig. 1, the water electrolysis apparatus 100 includes a water electrolysis stack 30 having a cell stack 20 in which a plurality of water electrolysis cells 10 are stacked, and a drain pipe 40 connected to the water electrolysis stack 30. Fig. 1 shows the water electrolysis apparatus 100 with the stacking direction of the water electrolysis cells 10 aligned with the direction of gravity. However, the state of the water electrolysis apparatus 100 is not limited to the state in which the stacking direction is aligned with the direction of gravity, and may be changed as appropriate as long as the effects of the water electrolysis apparatus 100 are achieved.

[0018] <Water electrolysis cell 10> Fig. 2 shows an exploded perspective view of a water electrolysis cell 10. As shown in Fig. 2, the water electrolysis cell 10 includes a membrane electrode assembly 11 and a pair of separators 12 and 13 disposed on both sides of the membrane electrode assembly 11. A frame member 14 is also disposed around the membrane electrode assembly 11.

[0019] The membrane electrode assembly 11 includes a solid electrolyte layer, an oxygen electrode catalyst layer laminated on one surface of the solid electrolyte layer, and a hydrogen electrode catalyst layer laminated on the other surface of the solid electrolyte layer. In one embodiment, the membrane electrode assembly 11 has an oxygen electrode catalyst layer laminated on the upper surface of the solid electrolyte layer in the lamination direction, and a hydrogen electrode catalyst layer laminated on the lower surface.

[0020] The solid electrolyte layer is not particularly limited as long as it has proton conductivity. For example, it may be a polymer electrolyte having a sulfonic acid group. From the viewpoint of durability, the polymer electrolyte may be a fluorine-containing polymer. For example, it may be a perfluorocarbon polymer.

[0021] The oxygen electrode catalyst layer includes an oxygen electrode catalyst capable of generating oxygen by water electrolysis. The oxygen electrode catalyst is not particularly limited, but examples thereof include metal catalysts. Examples of metal catalysts include metal catalysts containing Pt, Ru, Rh, Os, Ir, Pd, and Au. The metal catalyst may be an oxide of these metals. The oxygen electrode catalyst may also be an electrically conductive support (metal-supported catalyst) that supports the metal catalyst. The oxygen electrode catalyst layer may also include an ionomer having proton conductivity. The ionomer is not particularly limited. For example, a proton-conducting polymer may be used. Examples of proton-conducting polymers include fluoroalkyl polymers such as polytetrafluoroethylene; fluoroalkyl polymers such as perfluoroalkylsulfonic acid polymers, and the like.

[0022] The hydrogen electrode catalyst layer includes a hydrogen electrode catalyst capable of generating hydrogen by water electrolysis. The hydrogen electrode catalyst is not particularly limited, but examples thereof include metal catalysts. Examples of metal catalysts include metal catalysts containing Pt, Ru, Rh, Os, Ir, Pd, and Au in their composition. The metal catalyst may be an oxide of these metals. The hydrogen electrode catalyst may also be an electrically conductive support (metal-supported catalyst) that supports a metal catalyst. The type of support is not particularly limited, but examples thereof include carbon supports. The hydrogen electrode catalyst layer may also include an ionomer having proton conductivity. The ionomer is not particularly limited, but examples thereof include the ionomers described above.

[0023] Separators 12 and 13 are disposed on both sides of the membrane electrode assembly 11. Separator 12 is disposed on the oxygen electrode catalyst layer side. Separator 13 is disposed on the hydrogen electrode catalyst layer side. Separators 12 and 13 are formed from conductive materials. Examples include resin materials containing carbon materials, and metal materials such as iron, copper, stainless steel, and titanium. Predetermined flow paths are formed on the catalyst layer side of separators 12 and 13, and these flow paths serve to guide water supplied to the water electrolysis cell 10, and oxygen and hydrogen produced by the water electrolysis reaction.

[0024] The frame member 14 is disposed around the membrane electrode assembly 11. As shown in Fig. 2, the frame member 14 has hydrogen electrode holes 14a and 14b, an oxygen electrode hole 14c, and a water supply hole 14d. The material of the frame member is not particularly limited, but an insulating resin can be used, for example.

[0025] The water electrolysis cell 10 is formed by arranging a pair of separators 12, 13 on both sides of a membrane electrode assembly 11 having a frame-shaped member 14. These members are stacked in this manner so that the hydrogen electrode holes 14a, 14b of the frame-shaped member 14 communicate with the hydrogen electrode holes 12a, 12b, 13a, 13b of the separators 12, 13, the oxygen electrode hole 14c of the frame-shaped member 14 communicates with the oxygen electrode holes 12c, 12c of the separators 12, 13, and the water supply hole 14d of the frame-shaped member 14 communicates with the water supply holes 12d, 13d of the separators 12, 13. Hereinafter, these communicating holes may be referred to as hydrogen electrode communicating holes 10a, 10b, oxygen electrode communicating hole 10c, and water supply communicating hole 10d, respectively.

[0026] The water electrolysis reaction in the water electrolysis cell 10 will now be described. Water is supplied to the water electrolysis cell 10 through the water supply passage 10d, and a voltage is applied, causing a water electrolysis reaction in each catalyst layer. First, water is supplied to the oxygen electrode catalyst layer (solid arrow in FIG. 2), and oxygen and protons are generated by the water electrolysis reaction. The generated oxygen moves along the flow path formed in the separator 12 and is extracted to the outside through the oxygen electrode communication hole 10c (dotted arrow in FIG. 2). Similarly, water moves along the flow path formed in the separator 12 and is extracted to the outside through the oxygen electrode communication hole 10c. Protons generated in the oxygen electrode catalyst layer 13 permeate the solid electrolyte layer and reach the hydrogen electrode catalyst layer. The protons then combine with electrons to generate hydrogen. The generated hydrogen moves along the flow path formed in the separator 13 and is extracted to the outside through the hydrogen electrode communication holes 10a and 10b (dashed arrow in FIG. 2).

[0027] <Cell stack 20> The cell stack 20 is formed by stacking multiple water electrolysis cells 10. The number of stacked water electrolysis cells 10 is not particularly limited and may be set appropriately depending on the desired performance ratio. In the cell stack 20, the multiple water electrolysis cells 10 are stacked so that the hydrogen electrode communication holes 10a, 10b, the oxygen electrode communication holes 10c, and the water supply communication holes 10d are communicated with each other.

[0028] <Water electrolysis stack 30> The water electrolysis stack 30 includes a cell stack 20. As shown in Fig. 1 , end plates 35a, 35b are arranged on both end surfaces of the cell stack 20. The end plate 35a is arranged on the upper end surface in the stacking direction of the cell stack 20, and the end plate 35b is arranged on the lower end surface in the stacking direction of the cell stack 20. The end plates 35a, 35b are composed of a terminal plate, an insulating plate, and an end plate, which are arranged in this order toward the outside in the stacking direction.

[0029] The terminal plates have terminals that are connected to an external power source, and when a voltage is applied to the terminal plates from the power source, the voltage is applied to the cell stack 20 arranged between the terminal plates. The end plates are components that apply a restraining force to the inside in the stacking direction and enhance the adhesion of the cell stack 20. For example, the end plates may be restrained using bolts and nuts to restrain the cell stack. The insulating plates serve to insulate the terminal plates and end plates. Note that in one embodiment, terminal plates, insulating plates, and end plates are used as the end plates 35a and 35b, but these components are not required. End plates 35a and 35b may be replaced by components that fulfill the roles of these components.

[0030] The water electrolysis stack 30 includes hydrogen electrode-side manifolds 31 and 32 through which hydrogen produced by water electrolysis flows, an oxygen electrode-side manifold 33 through which oxygen produced by water electrolysis flows, and a water supply manifold 34 through which water to be used for water electrolysis flows. As indicated by the arrows in Fig. 1 , in the water electrolysis stack 30, the hydrogen electrode-side manifolds 31 and 32 and the oxygen electrode-side manifold 33 are outlet-side manifolds, and the water supply manifold 34 is an inlet-side manifold.

[0031] The hydrogen electrode-side manifolds 31 and 32 are through-holes that penetrate the stacking direction and communicate with the hydrogen electrode communication holes 10a and 10b, respectively. The hydrogen electrode-side manifolds 31 and 32 also communicate with the end plates 35a and 35b. Therefore, the hydrogen electrode-side manifolds 31 and 32 each have openings on their upper and lower sides in the stacking direction. The openings 31a and 32a on the upper side in the stacking direction are formed in the end plate of end plate 35a, and the openings 31b and 32b (Figure 3) on the lower side in the stacking direction are formed in the end plate of end plate 35b.

[0032] As described above, hydrogen produced by water electrolysis flows through the hydrogen electrode side manifolds 31 and 32. However, water flowing through the oxygen electrode catalyst layer in the water electrolysis cell 10 may permeate the membrane electrode assembly 11 and leak to the hydrogen electrode catalyst layer side. Therefore, the leaked water may also flow through the hydrogen electrode side manifolds 31 and 32.

[0033] Here, the hydrogen electrode-side manifolds 31, 32, which are through-holes, have a gas-liquid separation function, and can easily separate hydrogen and water. Specifically, hydrogen that reaches the hydrogen electrode-side manifolds 31, 32 moves upward in the stacking direction and is removed to the outside through openings 31a, 32a. In contrast, water that reaches the hydrogen electrode-side manifolds 31, 32 moves downward in the stacking direction due to the influence of gravity and is sent to the drain pipe 40 (hydrogen electrode-side drain pipes 41, 42) through openings 31b, 32b.

[0034] The oxygen electrode-side manifold 33 is a through-hole that penetrates in the stacking direction and communicates with the oxygen electrode communicating holes 10c. The oxygen electrode-side manifold 33 also communicates with the end plates 35a and 35b. Therefore, the oxygen electrode-side manifold 33 has openings on both the upper and lower sides in the stacking direction. The opening 33a provided on the upper side in the stacking direction is formed in the end plate of the end plate 35a, and the opening 33b (FIG. 3) provided on the lower side in the stacking direction is formed in the end plate of the end plate 35b.

[0035] As described above, the oxygen electrode side manifold 33 is a through-hole like the hydrogen electrode side manifolds 31 and 32, and thus has a gas-liquid separation function. As described above, oxygen and water generated by water electrolysis flow through the oxygen electrode side manifold 33. Therefore, the oxygen electrode side manifold 33 can easily separate oxygen and water. Specifically, oxygen that reaches the oxygen electrode side manifold 33 moves upward in the stacking direction and is taken out through the opening 33a. In contrast, water that reaches the oxygen electrode side manifold 33 moves downward in the stacking direction due to the influence of gravity and is sent to the drain pipe 40 (oxygen electrode side drain pipe 43) through the opening 33b.

[0036] The water supply manifold 34 is a communication hole that communicates with the water supply communication holes 10d. The water supply manifold 34 also communicates with the end plate 35a. Therefore, the opening 34a provided on the upper side of the water supply manifold 34 in the stacking direction is formed in the end plate of the end plate 35a. On the other hand, the lower end of the water supply manifold 34 in the stacking direction is closed. Typically, the water supply hole 13d of the separator 13 of the water electrolysis cell 10 located at the bottom in the stacking direction is closed. Alternatively, the closed portion may be provided in the end plate 35b. By closing the lower end of the water supply manifold 34 in this manner, water supplied from the outside can be supplied to each water electrolysis cell 10.

[0037] <Drain pipe 40> As described above, the hydrogen electrode-side manifolds 31 and 32 and the oxygen electrode-side manifold 33 have a gas-liquid separation function, which moves water downward in the stacking direction. The drain pipe 40 has the function of joining and discharging this water. As shown in Figure 1, the drain pipe 40 includes hydrogen electrode-side drain pipes 41 and 42 connected to the hydrogen electrode-side manifolds 31 and 32, an oxygen electrode-side drain pipe 43 connected to the oxygen electrode-side manifold 33, and connecting pipes 44 and 45 that connect the hydrogen electrode-side drain pipes 41 and 42 and the oxygen electrode-side drain pipe 43. Figure 3 shows a schematic diagram focusing on the drain pipe 40.

[0038] (hydrogen electrode side drainage pipes 41, 42) The hydrogen electrode side drain pipes 41, 42 are pipes that carry water separated by the gas-liquid separation function of the hydrogen electrode side manifolds 31, 32. Upper end portions 41a, 42a of the hydrogen electrode side drain pipes 41, 42 in the stacking direction are connected to lower openings 31b, 32b of the hydrogen electrode side manifolds 31, 32 in the stacking direction. Lower end portions 41b, 42b of the hydrogen electrode side drain pipes 41, 42 in the stacking direction are connected to one end of connecting pipes 44, 45 (connection positions 44a, 45a). However, in the water electrolysis device of the present disclosure, the connection position between the hydrogen electrode side drain pipe and the connecting pipe is not limited to the lower end portion of the hydrogen electrode side drain pipe in the stacking direction.

[0039] (Oxygen electrode side drain pipe 43) The oxygen electrode side drain pipe 43 is a pipe through which water separated by the gas-liquid separation function of the oxygen electrode side manifold 33 flows. An upper end 43a of the oxygen electrode side drain pipe 43 in the stacking direction is connected to an opening 33b on the lower side of the oxygen electrode side manifold 33 in the stacking direction. The oxygen electrode side drain pipe 43 is connected to the other ends of the connecting pipes 44 and 45 (connection positions 44b and 45b). The connection positions 44b and 45b between the oxygen electrode side drain pipe 43 and the connecting pipes 44 and 45 are not particularly limited. However, as described below, the connection positions 44b and 45b may be located above the connection positions 44a and 45a in the stacking direction. The lower end 43b of the oxygen electrode side drain pipe 43 in the stacking direction may be connected to, for example, a drain valve or a circulation pump. If the lower end 43b is connected to a circulation pump, the discharged water may be circulated to the water supply manifold 34.

[0040] (Connecting pipes 44 and 45) The connecting pipes 44, 45 connect the hydrogen electrode side drain pipes 41, 42 and the oxygen electrode side drain pipe 43, and are pipes for flowing the water separated by the hydrogen electrode side manifolds 31, 32 from the hydrogen electrode side drain pipes 41, 42 to the oxygen electrode side drain pipe 43.

[0041] In this way, the water separated by the hydrogen electrode-side manifolds 31, 32 flows through the hydrogen electrode-side drain pipes 41, 42 and connecting pipes 44, 45 into the oxygen electrode-side drain pipe 43, where it joins with the water separated by the oxygen electrode-side manifold 33. In the water electrolysis device 100, the pressure on the oxygen electrode side is typically set lower than the pressure on the hydrogen electrode side. That is, the pressure of oxygen generated by the water electrolysis reaction is set lower than the pressure of hydrogen. The pressures of hydrogen and oxygen can be measured by pressure measuring devices installed near the outlets (openings 31a, 32a, 33a) of the hydrogen electrode-side manifolds 31, 32 and the oxygen electrode-side manifold 33.

[0042] As described above, because the pressure on the oxygen electrode side is set lower than the pressure on the hydrogen electrode side, there is a risk that not only water but also hydrogen will flow from the hydrogen electrode-side drain pipes 41 and 42 to the oxygen electrode drain pipe 43 via the connecting pipes 44 and 45 due to the pressure difference. Therefore, the water electrolysis apparatus 100 is provided with drain valves on the connecting pipes 44 and 45 to prevent hydrogen from flowing into the oxygen electrode drain pipe 43.

[0043] The drain valves adjust the flow rate of water flowing through the connecting pipes 44, 45, and in one embodiment include a shutoff valve 46 and a flow regulation valve 47. The shutoff valve 46 is an on-off valve that controls the flow and cut-off of water flowing through the connecting pipes 44, 45. The flow regulation valve 47 adjusts the flow rate of the water flowing through, and the flow rate can be adjusted by changing the opening degree of the valve. The shutoff valve 46 and the flow regulation valve 47 are arranged from the high pressure side to the low pressure side, i.e., from the hydrogen electrode side drain pipes 41, 42 to the oxygen electrode side drain pipe 43.

[0044] A method for suppressing the inflow of hydrogen into the oxygen electrode-side drain pipe 42 using the shutoff valve 46 and the flow regulation valve 47 will be described. First, water is stored in the hydrogen electrode-side drain pipes 41 and 42 with the shutoff valve 46 and the flow regulation valve 47 closed. Next, when the water level reaches a predetermined height, the shutoff valve 46 and the flow regulation valve 47 are opened in this order. At this time, the opening degree of the flow regulation valve 47 may be adjusted as appropriate. Then, when the water level drops to a predetermined position (set to a position higher than the connection positions 44a and 45a to suppress the inflow of hydrogen into the oxygen electrode-side drain pipe 42), the shutoff valve 46 and the flow regulation valve 47 are closed. By operating the shutoff valve 46 and the flow regulation valve 47 in this manner, the inflow of hydrogen into the oxygen electrode-side drain pipe 43 can be suppressed.

[0045] To easily adjust the level of the stored water, a water level gauge may be provided in the hydrogen electrode side drain pipes 41, 42. This allows the shutoff valve 46 and the flow regulation valve 47 to be opened when the water level reaches a predetermined height (H in FIG. 3), and the shutoff valve 46 and the flow regulation valve 47 to be closed when the water level drops to a predetermined height (L in FIG. 3).

[0046] Figure 4 shows an example of a time chart when adjusting the water level in a drain pipe using a water level gauge. As shown in Figure 4, immediately after the start, the water level gauge indicates Low, and the shutoff valve and flow regulation valve are closed. Next, water electrolysis begins at time t1, and the water level rises over time. Then, at time t2, the water level gauge detects that the water level has risen to a predetermined height, and at time t3, the shutoff valve is opened. Next, at time t4, the flow regulation valve gradually opens, causing the water level to drop. Then, at time t5, the water level gauge detects that the water level has fallen to a predetermined height, and the shutoff valve and flow regulation valve are closed. Because the water level does not change, the shutoff valve and flow regulation valve remain closed at time t6.

[0047] The connecting pipes 44, 45 will now be described. As shown in Figures 1 and 3, the connecting pipes 44, 45 are inclined. The inclination increases from the high-pressure side to the low-pressure side, i.e., from the hydrogen electrode-side drain pipes 41, 42 toward the oxygen electrode-side drain pipe 43. This means that the connection positions 45, 45b between the oxygen electrode-side drain pipe 43 and the connecting pipes 44, 45 are located higher in the stacking direction than the connection positions 44a, 45a between the hydrogen electrode-side drain pipes 41, 42 and the connecting pipes 44, 45. By inclining the connecting pipes 44, 45 in this way, the inflow of hydrogen into the oxygen electrode-side drain pipe 43 can be further suppressed. The inclination may be provided only on a portion of the connecting pipes 44, 45, or may be provided on the entire pipe to enhance the effect. The inclination angle is not particularly limited and may be set appropriately depending on the purpose.

[0048] <Effects> In conventional water electrolysis systems, hydrogen and water discharged from the hydrogen electrode-side manifold are separated by a gas-liquid separator. Furthermore, oxygen and water discharged from the oxygen electrode-side manifold are separated by a gas-liquid separator. Thus, conventional water electrolysis systems are provided with gas-liquid separators on both the oxygen electrode side and the hydrogen electrode side. On the other hand, as described above, the water electrolysis device 100 includes the hydrogen electrode-side manifolds 31 and 32 and the oxygen electrode-side manifold 33, which have a gas-liquid separation function. This allows the gas-liquid separators provided on the oxygen electrode side and the hydrogen electrode side of the water electrolysis system to be downsized or eliminated. Therefore, the water electrolysis device 100 allows the entire water electrolysis system to be downsized.

[0049] In the water electrolysis apparatus 100, the water separated by the hydrogen electrode-side manifolds 31 and 32 and the oxygen electrode-side manifold 33 flows into the hydrogen electrode-side drain pipes 41 and 42 and the oxygen electrode-side drain pipe 43, respectively. The water that flows into the hydrogen electrode-side drain pipes 41 and 42 flows into the oxygen electrode-side drain pipe 43 via connecting pipes 44 and 45. This allows the water to be discharged to be collected in the oxygen electrode-side drain pipe 43, thereby improving drainage efficiency.

[0050] However, as described above, in the water electrolysis apparatus 100, the pressure on the oxygen electrode side is usually set lower than the pressure on the hydrogen electrode side. Therefore, due to the pressure difference, there is a risk that hydrogen will flow from the hydrogen electrode side drain pipes 41 and 42 into the oxygen electrode side drain pipe 43 via the connecting pipes 44 and 45. Therefore, in the water electrolysis apparatus 100, in order to suppress backflow of gas due to such a pressure difference, drain valves (shutoff valve 46 and flow adjustment valve 47) are provided on the connecting pipes 44 and 45. This makes it possible to suppress backflow of gas in the drain pipe 40.

[0051] <Supplementary information> In the water electrolysis apparatus 100, the number of hydrogen electrode-side manifolds is twice the number of oxygen electrode-side manifolds. This is because the amount of hydrogen produced by the water electrolysis reaction is twice the amount of oxygen. Therefore, by providing the water electrolysis apparatus 100 with twice the number of hydrogen electrode-side manifolds as the number of oxygen electrode-side manifolds, it is possible to reduce pressure loss due to hydrogen produced by the water electrolysis reaction. However, in the water electrolysis apparatus according to the present disclosure, the number of hydrogen electrode-side manifolds may be less than twice the number of oxygen electrode-side manifolds. For example, the number of hydrogen electrode-side manifolds may be the same as the number of oxygen electrode-side manifolds. However, from the perspective of reducing pressure loss, the number of hydrogen electrode-side manifolds may be more than twice the number of oxygen electrode-side manifolds.

[0052] In the water electrolysis device 100, the structure of the drain pipe 40 is determined based on the fact that the pressure on the oxygen electrode side is set lower than the pressure on the hydrogen electrode side. However, in the water electrolysis device disclosed herein, the pressure on the hydrogen electrode side may be set lower than the pressure on the oxygen electrode side. In this case, the water separated by the water electrolysis stack may be collected in the hydrogen electrode side drain pipe on the low-pressure side and discharged to the outside. In addition, the inclination of the connecting pipe may be set to increase from the oxygen electrode side drain pipe toward the hydrogen electrode side drain pipe.

[0053] [Water electrolysis system] Use of the water electrolysis device described above allows the entire water electrolysis system to be miniaturized. Therefore, the present disclosure describes an embodiment of a water electrolysis system using the water electrolysis device. In the embodiment, neither the oxygen electrode side nor the hydrogen electrode side includes a gas-liquid separator. However, the water electrolysis system of the present disclosure may include a gas-liquid separator on at least one of the oxygen electrode side and the hydrogen electrode side.

[0054] One embodiment is a water electrolysis system 1000 comprising the water electrolysis device 100, a power supply 200 that applies a voltage to the water electrolysis device 100, a water supply device 300 that supplies water to the water electrolysis device 100, a water supply flow path 510 that connects the water electrolysis device 100 and the water supply device 300 and through which water supplied from the water supply device 300 to the water electrolysis device 100 flows, a water discharge flow path 520 that is connected to the water electrolysis device 100 and through which water discharged from the water electrolysis device 100 flows, a hydrogen tank 400 that stores hydrogen produced by water electrolysis, a hydrogen distribution flow path 530 that connects the water electrolysis device 100 and the hydrogen tank 400 and through which hydrogen supplied from the water electrolysis device 100 to the hydrogen tank 400 flows, and an oxygen distribution flow path 540 that is connected to the water electrolysis device 100 and through which oxygen produced by the water electrolysis reaction flows. Fig. 5 shows a block diagram of the water electrolysis system 1000.

[0055] The water electrolysis apparatus 100 has been described above, and therefore a detailed description thereof will be omitted here. The power supply 200 applies a voltage to the water electrolysis apparatus 100 to cause a water electrolysis reaction in the water electrolysis apparatus 100. Such a power supply 200 is known. The power supply 200 is connected to the terminal plates of the end plates 35a, 35b of the water electrolysis apparatus 100. The water supply device 300 supplies water to the water electrolysis apparatus 100. Such a water supply device 300 is known. The hydrogen tank 400 stores hydrogen produced by water electrolysis. Such a hydrogen tank 400 is known.

[0056] The water supply flow path 510 is a pipe for carrying water supplied from the water supply device 300 to the water electrolysis device 100. The water supply flow path 510 is connected to the opening 34a of the water supply manifold 34 of the water electrolysis device 100.

[0057] The water discharge flow path 520 is connected to the water electrolysis apparatus 100 and is a pipe for passing water discharged from the water electrolysis apparatus 100. The water discharge flow path 520 is connected to the oxygen electrode side drain pipe 43 of the water electrolysis apparatus 100. The water discharged from the water electrolysis apparatus 100 may be discharged to the outside via the water discharge flow path 520, or may be sent to the water supply device 300 as shown in FIG. 5 . In other words, the water discharge flow path 520 may connect the oxygen electrode side drain pipe 43 and the water supply device 300. This allows the water to be reused.

[0058] The hydrogen flow channel 530 connects the water electrolysis apparatus 100 and the hydrogen tank 400, and is a pipe for passing hydrogen supplied from the water electrolysis apparatus 100 to the hydrogen tank 400. The hydrogen flow channel 530 is connected to the openings 31a and 32a of the hydrogen electrode-side supply manifolds 31 and 32 of the water electrolysis apparatus 100, respectively. As shown in Fig. 5, the hydrogen flow channel 530 may be configured to join hydrogen flowing from the hydrogen electrode-side supply manifolds 31 and 32.

[0059] The oxygen flow channel 540 is a pipe connected to the water electrolysis apparatus 100 for passing oxygen generated by the water electrolysis reaction. The oxygen flow channel 540 is connected to the opening 33a of the oxygen electrode-side manifold 33 of the water electrolysis apparatus 100. Oxygen discharged from the water electrolysis apparatus 100 may be discharged to the outside via the oxygen flow channel 540. [Explanation of symbols]

[0060] 10 Water electrolysis cell 11 Membrane electrode assembly 11 12, 13 Separator 14 Frame-shaped member 14 20 cell stack 30 Water electrolysis stack 31, 32 Hydrogen electrode side manifold 33 Oxygen electrode side manifold 34 Water Supply Manifold 35a, 35b end plates 40 Drain pipe 41, 42 Hydrogen electrode side drain pipe 43 Oxygen electrode side drain pipe 44, 45 Connecting pipe 46 Shut-off valve 47 Flow Regulating Valve 100 Water electrolysis equipment 200 power supply 300 Water supply equipment 400 Hydrogen Tank 1000 Water Electrolysis System

Claims

1. a water electrolysis stack including a cell stack in which a plurality of water electrolysis cells are stacked, and a drain pipe connected to the water electrolysis stack, The water electrolysis stack includes a hydrogen electrode side manifold through which hydrogen generated by water electrolysis flows; an oxygen electrode-side manifold through which oxygen produced by water electrolysis flows, and a water supply manifold through which water to be used for water electrolysis flows; the hydrogen electrode side manifold and the oxygen electrode side manifold penetrate each other in the stacking direction, the drain pipe comprises a hydrogen electrode side drain pipe connected to the hydrogen electrode side manifold, an oxygen electrode side drain pipe connected to the oxygen electrode side manifold, and a connecting pipe connecting the hydrogen electrode side drain pipe and the oxygen electrode side drain pipe, The connecting pipe is provided with a drain valve for adjusting the flow rate of water flowing through the connecting pipe. Water electrolysis equipment.

2. The water electrolysis apparatus according to claim 1 , wherein the connecting pipe has an inclination.

3. The water electrolysis apparatus according to claim 1 or 2, wherein a water level meter is provided in the oxygen electrode side drain pipe.

4. 3. The water electrolysis apparatus according to claim 1, wherein the number of the hydrogen electrode side manifolds is at least twice the number of the oxygen electrode side manifolds.

5. The water electrolysis device according to claim 1 or 2; a power source that applies a voltage to the water electrolysis device; a water supply device that supplies water to the water electrolysis device; a water supply flow path connecting the water electrolysis apparatus and the water supply device, for flowing the water supplied from the water supply device to the water electrolysis apparatus; a water discharge flow path connected to the water electrolysis device for allowing water discharged from the water electrolysis device to flow; a hydrogen tank for storing hydrogen generated by water electrolysis; a hydrogen flow path connecting the water electrolysis device and the hydrogen tank, for flowing hydrogen supplied from the water electrolysis device to the hydrogen tank; an oxygen flow path connected to the water electrolysis device for flowing oxygen generated by the water electrolysis reaction; Water electrolysis system.

Images