Water electrolysis system

Abstract

The invention provides a water electrolysis system capable of ensuring cooling of a water electrolysis cell and suppressing deterioration of durability of the water electrolysis cell. A water electrolysis system for obtaining hydrogen from a hydrogen electrode by supplying water to an oxygen electrode of a water electrolysis cell and applying a voltage to the water electrolysis cell, the water electrolysis system having a cooling fluid path for supplying a cooling fluid different from the water supplied to the oxygen electrode to the water electrolysis cell through a flow path different from a flow path through which the water is supplied to the oxygen electrode.

Description

Technical Field

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

[0002] Patent Document 1 discloses circulating cooling water cooled in a radiator to a water electrolysis stack.

[0003] Patent Document 2 discloses coping with the influence of a double-layer flow in water electrolysis.

[0004] Patent Document 3 discloses cooling supply water to the anode before supplying it to the stack.

[0005] Patent Document 4 discloses continuing the circulation of water to the anode to effect cooling when water electrolysis stops.

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2022-153049

[0007] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2002-285368

[0008] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2017-203203

[0009] Patent Document 4: Japanese Unexamined Patent Application Publication No. 2012-067343

[0010] On the outlet side of the oxygen electrode of the water electrolysis cell, as oxygen is generated, the proportion of oxygen in the supply water for water electrolysis increases, and the cooling effect brought about by the supply water is lower than that on the inlet side, and it cannot be said that the suppression of the temperature rise of the water electrolysis cell is sufficient. If the temperature of the water electrolysis cell rises excessively, the durability of the water electrolysis cell will decrease. Summary of the Invention

[0011] In view of the above problems, an object of the present disclosure is to provide a water electrolysis system that can ensure cooling of a water electrolysis cell and suppress a decrease in the durability of the water electrolysis cell.

[0012] The present application discloses a water electrolysis system that obtains hydrogen from a hydrogen electrode by supplying water to an oxygen electrode of a water electrolysis cell and applying a voltage to the water electrolysis cell, and includes a cooling fluid path that supplies a cooling fluid different from the water supplied to the oxygen electrode to the water electrolysis cell through a second flow path different from a first flow path for supplying water to the oxygen electrode.

[0013] It may be configured such that the direction of flow of the cooling fluid is in a countercurrent relationship with the direction of flow of the water supplied to the oxygen electrode.

[0014] The cooling fluid may be accompanying water discharged from the hydrogen electrode.

[0015] The cooling fluid may be water branched from a path for supplying water to the oxygen electrode.

[0016] The cooling fluid may be water supplied from a gas-liquid separator provided on the hydrogen electrode side.

[0017] In the above water electrolysis system, the water electrolysis cell may have a diaphragm at the oxygen electrode, a first flow path formed on the first surface of the diaphragm, and a second flow path formed on the second surface opposite to the first surface.

[0018] In the above water electrolysis system, the first flow path and the second flow path may extend in parallel.

[0019] According to the present disclosure, it is possible to suppress an increase in the proportion of oxygen and a rise in the temperature of the outlet region of the oxygen electrode where the cooling effect is reduced by the circulation of the cooling fluid. Description of the Drawings

[0020] Figure 1 It is a plan view of the water electrolysis cell 10.

[0021] Figure 2 It is a cross-sectional view for explaining the layer structure in the water electrolysis region 10a of the water electrolysis cell 10.

[0022] Figure 3 It is another cross-sectional view for explaining the layer structure in the water electrolysis region 10a of the water electrolysis cell 10.

[0023] Figure 4 It is a schematic diagram for explaining the structure of the water electrolysis stack 20.

[0024] Figure 5 It is a view for explaining the stacked structure of the water electrolysis cells 10 in the water electrolysis stack 20.

[0025] Figure 6 It is another view for explaining the stacked structure of the water electrolysis cells 10 in the water electrolysis stack 20.

[0026] Figure 7 It is a schematic diagram for explaining Mode 1 of the water electrolysis system 30.

[0027] Figure 8 It is a schematic diagram for explaining Mode 2 of the water electrolysis system 30.

[0028] Figure 9 It is a schematic diagram for explaining Mode 3 of the water electrolysis system 30. Detailed Description of the Invention

[0029] 1. Water Electrolysis Cell

[0030] First, the configuration of the water electrolysis cell to be cooled will be described.

[0031] Figure 1 FIG. shows a diagram for explaining the structure of the water electrolysis cell 10 related to one mode. The water electrolysis cell 10 is a unit element for decomposing pure water into hydrogen and oxygen, and a plurality of such water decomposition cells are stacked to form a water electrolysis stack described later. Figure 1 is a top view of the water electrolysis cell 10. In Figure 1 , in order to explain the internal structure of the water electrolysis cell 10, a part of the internal structure (especially the water electrolysis region) is indicated by a dotted line.

[0032] The principle of water electrolysis in the water electrolysis cell 10 is the same as that of the known one, and its outline is as follows.

[0033] Pure water (feed water for water electrolysis) is supplied from the oxygen electrode inlet hole (oxygen electrode side inlet manifold) 10b, reaches the water electrolysis region 10a, and is subjected to water electrolysis here.

[0034] In the water electrolysis region 10a, a part of the pure water is decomposed into oxygen and hydrogen by the water electrolysis membrane electrode assembly described later, and is discharged through their respective flow paths. Specifically, the generated oxygen and the remaining feed water for water electrolysis are discharged from the oxygen electrode outlet hole (oxygen electrode side outlet manifold) 10c. On the other hand, the generated hydrogen and the water move to the electrode (hydrogen electrode) on the side opposite to the electrode (oxygen electrode) through which the feed water for water electrolysis flows across the water electrolysis membrane electrode assembly, and are discharged from the hydrogen electrode outlet hole (hydrogen electrode side outlet manifold) 10d. Both the oxygen electrode and the hydrogen electrode are installed inside the water electrolysis cell 10, but outside the water electrolysis region 10a, they are separated by a sealing member (not shown) so that the generated hydrogen and oxygen do not mix to form respective separate flow paths.

[0035] In this mode, as also described later, it is configured such that the cooling fluid flows in a flow path (cooling fluid flow path 25) formed outside the oxygen electrode of the water electrolysis cell 10 when it becomes a water electrolysis stack. The cooling fluid flows in from the cooling fluid inlet hole (cooling fluid inlet manifold) 10e to cool the oxygen electrode side of the water electrolysis cell 10, and is discharged from the cooling fluid outlet hole (cooling fluid outlet manifold) 10f. Among them, the flow path for the cooling fluid to flow is also separated from the flow paths of the oxygen electrode and the hydrogen electrode, thereby being formed so as not to mix with each other.

[0036] The constitution of the water electrolysis cell 10 will be described below. Figure 2 is Figure 1 a part of the A-A cross-section of, and is a cross-section (a cross-section orthogonal to the direction of flow of each fluid) for explaining the layer constitution in the water electrolysis region 10a where water electrolysis is performed in the water electrolysis cell 10. Figure 3 is Figure 2The B-B cross-section is a cross-section (a cross-section parallel to the direction of each fluid flow) for explaining the layer structure in the water electrolysis region 10a where water electrolysis is performed.

[0037] The water electrolysis cell 10 is composed of multiple layers. With a solid polymer electrolyte membrane 11 interposed, one side becomes the oxygen electrode (anode) and the other side becomes the hydrogen electrode (cathode).

[0038] In the water electrolysis region 10a, as Figure 2 shown, on the anode side, an anode catalyst layer 12, an anode gas diffusion layer 13, and an anode separator 14 are laminated in sequence starting from the solid polymer electrolyte membrane 11 side. On the other hand, on the cathode side, a cathode catalyst layer 15, a cathode gas diffusion layer 16, and a cathode separator 17 are provided in sequence starting from the solid polymer electrolyte membrane 11 side. Here, the water electrolysis membrane electrode assembly refers to a laminate of the solid polymer electrolyte membrane 11, the anode catalyst layer 12 disposed on the anode side of the solid polymer electrolyte membrane 11, and the cathode catalyst layer 15 disposed on the cathode side of the solid polymer electrolyte membrane 11. The thickness of the water electrolysis membrane electrode assembly is typically about 0.4 mm, and the thickness of the water electrolysis cell 10 in the water electrolysis region 10a is typically about 1.3 mm.

[0039] 1.1. Solid polymer electrolyte membrane

[0040] The solid polymer electrolyte membrane 11 is one form of an electrolyte membrane having proton conductivity. In this embodiment, the material (electrolyte) constituting the solid polymer electrolyte membrane 11 is a solid polymer material, and examples thereof include proton-conductive ion exchange membranes formed of fluororesins, hydrocarbon resin materials, etc. It exhibits good proton conductivity (electrical conductivity) in a wet state. More specifically, a membrane based on Nafion (registered trademark), which is a perfluorinated electrolyte, can be cited as an example.

[0041] The thickness of the solid polymer electrolyte membrane 11 is not particularly limited, but it is 200 μm or less, preferably 100 μm or less, and more preferably 30 μm or less.

[0042] 1.2. Anode catalyst layer

[0043] The anode catalyst layer (oxygen electrode catalyst layer) 12 is a catalyst layer having at least one or more catalysts including noble metal catalysts such as Pt, Ru, Ir and their oxides. As the catalyst, more specifically, Pt, iridium oxide, ruthenium oxide, iridium ruthenium oxide, or a mixture thereof can be cited.

[0044] As the iridium oxide, iridium oxide (IrO2, IrO3), iridium tin oxide, iridium zirconium oxide, etc. can be cited.

[0045] Examples of ruthenium oxides include ruthenium oxide (RuO2, Ru2O3), ruthenium tantalum oxide, ruthenium zirconium oxide, ruthenium titanium oxide, ruthenium titanium cerium oxide, etc.

[0046] Examples of iridium ruthenium oxides include iridium ruthenium cobalt oxide, iridium ruthenium tin oxide, iridium ruthenium iron oxide, iridium ruthenium nickel oxide, etc.

[0047] Here, the anode catalyst layer 12 may include an ionomer. By including an ionomer, in addition to improving coatability, the permeation of water supplied during water electrolysis can be facilitated through its hydrophilicity. Examples of the ionomer included are ionomers including perfluorinated electrolytes used as electrolytes in solid polymer electrolyte membranes.

[0048] 1.3. Anode gas diffusion layer

[0049] The anode gas diffusion layer 13 is a gas diffusion layer disposed on the anode side and can use a known gas diffusion layer, which is composed of a component having air permeability and conductivity. Specifically, examples include porous conductive components composed of sintered bodies of metal fibers (such as titanium fibers) or metal particles (titanium particles), etc.

[0050] 1.4. Anode separator

[0051] The anode separator 14 is a component (separator) having a flow path (water supply flow path for water electrolysis) 14a for pure water supplied to the anode gas diffusion layer 13 and the decomposed oxygen to flow. In this embodiment, the anode separator 14 is a component in which a plate-like component is formed into a wave shape with repeated concavities and convexities in the water electrolysis region 10a, and the water supply flow path 14a for water electrolysis is formed between the anode gas diffusion layer 13 and the convex portion 14b by arranging the concave portion 14c in contact with the anode gas diffusion layer 13.

[0052] For example, the anode separator 14 can be formed by stamping a titanium thin film, and its plate thickness is typically 0.1 mm to 0.2 mm, and the height of the concavities and convexities is typically about 0.5 mm.

[0053] Among them, the concave portion 14c forms a flow path for the cooling fluid to flow when it becomes a water electrolysis stack as described later.

[0054] In addition, as Figure 1 and as described above, the anode separator 14 has an oxygen electrode inlet hole 10b, an oxygen electrode outlet hole 10c, a hydrogen electrode outlet hole 10d, a cooling fluid inlet hole 10e, and a cooling fluid outlet hole 10f.

[0055] 1.5. Cathode catalyst layer

[0056] The cathode catalyst layer 15 is a catalyst layer including a catalyst. The catalyst included in the cathode catalyst layer 15 can be a known catalyst, such as platinum, titanium-coated platinum, carbon-supported platinum, carbon-supported palladium, cobalt glyoxime, nickel glyoxime, etc.

[0057] Here, the cathode catalyst layer 15 may include an ionomer. By including the ionomer, improved coatability can be achieved. As the ionomer included, an ionomer composed of a perfluorinated electrolyte, which is an electrolyte used in a solid polymer electrolyte membrane, can be cited.

[0058] 1.6. Cathode gas diffusion layer

[0059] The cathode gas diffusion layer 16 is a gas diffusion layer disposed on the cathode side and can be a known gas diffusion layer, which is composed of a component having gas permeability and conductivity. Specifically, porous components such as carbon cloth and carbon paper can be cited.

[0060] 1.7. Cathode diaphragm

[0061] The cathode diaphragm 17 is a component having a flow path 17a through which hydrogen generated by the reduction of hydrogen ions and water (accompanying water) accompanying the passage of hydrogen ions through the solid polymer electrolyte membrane 11 can reach. In this embodiment, the cathode diaphragm 17 is a component in which a plate-like component is formed into a wave shape in the water electrolysis region 10a with concavities and convexities repeated, and a flow path 17a for hydrogen discharge is formed between the cathode gas diffusion layer 16 and the convex portion 17b by arranging the concave portion 17c in contact with the cathode gas diffusion layer 16.

[0062] For example, the cathode diaphragm 17 can be formed by stamping a titanium thin film, and its plate thickness is typically 0.1 mm to 0.2 mm, and the height of the concavities and convexities is typically about 0.5 mm.

[0063] In addition, as Figure 1 described above, the cathode diaphragm 17 has an oxygen electrode inlet hole 10b, an oxygen electrode outlet hole 10c, a hydrogen electrode outlet hole 10d, a cooling fluid inlet hole 10e, and a cooling fluid outlet hole 10f.

[0064] 1.8. Layer structure of the water electrolysis region

[0065] The layer structure of the water electrolysis region 10a is as Figure 2 、 Figure 3 shown. On the anode side, an anode catalyst layer 12, an anode gas diffusion layer 13, and an anode diaphragm 14 are sequentially stacked from the side of the solid polymer electrolyte membrane 11. On the other hand, on the cathode side, a cathode catalyst layer 15, a cathode gas diffusion layer 16, and a cathode diaphragm 17 are sequentially provided from the side of the solid polymer electrolyte membrane 11.

[0066] The anode separator 14 has a flow path (water supply flow path for water electrolysis) 14a through which pure water supplied to the anode gas diffusion layer 13 and the generated oxygen flow. In this embodiment, the anode separator 14 is formed by forming a plate-shaped member into a wave shape with repeated concavities and convexities in the water electrolysis region 10a, and the concave portion 14c is arranged to contact the anode gas diffusion layer 13 to form a water supply flow path 14a for water electrolysis between the anode gas diffusion layer 13 and the convex portion 14b.

[0067] The cathode separator 17 has a flow path 17a through which hydrogen generated by the reduction of hydrogen ions and water (accompanying water) accompanying the permeation of hydrogen ions through the solid polymer electrolyte membrane 11 reach. In this embodiment, the cathode separator 17 is formed by forming a plate-shaped member into a wave shape with repeated concavities and convexities in the water electrolysis region 10a, and the concave portion 17c is arranged to contact the cathode gas diffusion layer 16 to form a flow path 17a for hydrogen discharge between the cathode gas diffusion layer 16 and the convex portion 17b.

[0068] 1.9. Generation of hydrogen and oxygen

[0069] The water electrolysis cell 10 according to the present disclosure functions as follows, for example.

[0070] If water for water electrolysis is supplied from the oxygen electrode side inlet manifold 10b, the water for water electrolysis reaches the water electrolysis region 10a. In the water electrolysis region 10a, by applying an electric current between the anode and the cathode, the water for water electrolysis (H2O) supplied to the anode (oxygen electrode) from the water supply flow path 14a for water electrolysis is decomposed into oxygen, electrons, and protons (H + ) at the anode catalyst layer 12 to which a potential is applied. At this time, the protons move through the solid polymer electrolyte membrane 11 to the cathode catalyst layer 15. On the other hand, the electrons separated at the anode catalyst layer 12 reach the cathode catalyst layer 15 through an external circuit. Moreover, the protons receive electrons at the cathode catalyst layer 15 to generate hydrogen (H2), and this hydrogen (H2) reaches the cathode gas diffusion layer 16. Among them, in the cathode gas diffusion layer 16, there is accompanying water together with the generated hydrogen gas.

[0071] The hydrogen gas and the accompanying water present in the cathode gas diffusion layer 16 reach the cathode separator 17, flow in the flow path 17a, and are discharged from the hydrogen electrode side outlet manifold 10d (hydrogen electrode outlet hole).

[0072] On the other hand, the oxygen and the remaining water that have not been used generated at the anode catalyst layer 12 return to the anode separator 14 and are discharged from the oxygen electrode outlet manifold 10c through the hydrogen supply flow path 14a.

[0073] 2. Water electrolysis stack

[0074] 2.1. Basic structure of the water electrolysis stack

[0075] The water electrolysis stack 20 is a component formed by overlapping a plurality (about 50 to 400 sheets) of the above-described water electrolysis cells 10, and electricity is applied to the plurality of water electrolysis cells 10 to generate hydrogen and oxygen. Figure 4 The schematic configuration thereof is shown. The water electrolysis stack 20 includes a stack housing 21, end plates 22, a plurality of water electrolysis cells 10, and a biasing member 23.

[0076] The stack housing 21 is a box that houses the plurality of overlapping water electrolysis cells 10 and the biasing member 23 inside. In this embodiment, the stack housing 21 has a quadrilateral cylindrical shape, is open at one end and closed at the other end, and a plate-like piece protrudes from the edge of the opening toward the side opposite to the opening to form a flange 21a.

[0077] The end plate 22 is a plate-like member that closes the opening of the stack housing 21. The end plate 22 is fixed to the stack housing 21 in such a manner that the overlapping portion with the flange 21a of the stack housing 21 is covered by bolts and nuts or the like.

[0078] The water electrolysis cell 10 is as described above. A plurality of such water electrolysis cells 10 are overlapped. Here, in this embodiment, it can be seen from Figure 4 that the water electrolysis cells 10 are configured to be overlapped in the horizontal direction. In each water electrolysis cell 10, as Figure 1 shown, the water supply flow path 14a and the flow path 17a are arranged in the vertical direction.

[0079] The biasing member 23 is housed inside the stack housing 21 and applies a pressing force to the stack of water electrolysis cells 10 in the stacking direction. Examples of the biasing member include a disc spring.

[0080] 2.2. Stacking structure of water electrolysis cells in the water electrolysis stack

[0081] As described above, in the water electrolysis stack 20, a plurality of water electrolysis cells 10 are stacked. In Figure 5 , three of the stacked water electrolysis cells 10 are taken out to show a cross section of a part (a part of the water electrolysis region 10a). In addition, Figure 6 shows a cross-sectional view along the line C-C in Figure 5 .

[0082] From Figure 5 , Figure 6It can be seen that in the electrolytic water chambers 10 adjacent to each other when the electrolytic water chambers 10 are stacked, the anode diaphragm 14 of one electrolytic water chamber 10 overlaps with the cathode diaphragm 17 of another electrolytic water chamber 10. More specifically, the convex portion 14b of the anode diaphragm 14 of one electrolytic water chamber 10 contacts and overlaps with the convex portion 17b of the cathode diaphragm 17 of another electrolytic water chamber 10. Similarly, the concave portion 14c of the anode diaphragm 14 configured as one electrolytic water chamber 10 overlaps with the concave portion 17c of the cathode diaphragm 17 of another electrolytic water chamber 10, and a cooling fluid flow path 25 is formed here.

[0083] That is, in the electrolytic water stack 20 of this embodiment, the electrolytic water chamber 10 includes a laminate for electrolytic water (a laminate formed by a solid polymer electrolyte membrane 11, an anode catalyst layer 12, an anode gas diffusion layer 13, a cathode catalyst layer 15, and a cathode gas diffusion layer 16) and diaphragms 14 and 17. The flat diaphragms 14 and 17 have a first surface on the side in contact with the laminate for electrolytic water and a second surface on the opposite side. On the first surface side, there are provided a supply water for electrolytic water, the generated oxygen, hydrogen, and a first flow path (electrolytic water supply flow path 14a, flow path 17a) for water flow. On the second surface, there is provided a second flow path (cooling fluid flow path) for the cooling fluid (refrigerant, liquid or gas) for cooling the electrolytic water chamber to flow.

[0084] From Figure 5 , Figure 6 it can be seen that the cooling fluid flow path 25 becomes a flow path parallel to the electrolytic water supply flow path 14a with the anode diaphragm 14 therebetween. For the cooling fluid flow path 25, one end thereof communicates with a cooling fluid introduction hole (cooling fluid inlet manifold) 10e, and the other end communicates with a cooling fluid discharge hole (cooling fluid outlet manifold) 10f (refer to Figure 1 ), the cooling fluid is supplied from the cooling fluid introduction hole 10e, the cooling fluid flows in the cooling fluid flow path 25, and is discharged from the cooling fluid discharge hole 10f.

[0085] In the electrolytic water stack 20, as described above, inside the electrolytic water chamber 10, the water supplied from the oxygen electrode introduction hole 10b is decomposed into hydrogen and oxygen, and the generated oxygen and the remaining water flow in the electrolytic water supply flow path 14a along the Figure 1 , Figure 3 direction indicated by the arrow P in the figure and are discharged from the oxygen electrode discharge hole 10c.

[0086] On the other hand, the cooling fluid supplied from the cooling fluid introduction hole 10e flows along the Figure 1 , Figure 3 , Figure 6It flows in the direction indicated by arrow Q to cool the oxygen electrode. On the discharge side of the oxygen electrode from the water electrolysis cell, along with the generation of oxygen, the proportion of oxygen relative to the water supply for water electrolysis increases, and the cooling effect brought by the supply water is lower than that on the inlet side. It cannot be said that the suppression of the temperature rise of the water electrolysis cell is sufficient. If the temperature of the water electrolysis cell rises excessively, the water electrolysis performance will decrease. In contrast, in this method, since the cooling fluid flows as described above, cooling that meets the requirements can be achieved, and the water electrolysis performance can be maintained.

[0087] In this method, the flow of the fluid in the water electrolysis supply flow path 14a and the flow of the fluid in the cooling fluid flow path 25 form a countercurrent flow, but it is not limited to this, and a parallel flow can also be used. In the case of a parallel flow, in Figure 1 it, it is only necessary to change the positions of the cooling water inlet hole 10e and the cooling water outlet hole 10f.

[0088] In addition, all surfaces of the flat water electrolysis cell can be cooled through the cooling fluid flow path, or it can also be configured to cool a part of the area. For the cooling inside the water electrolysis cell, it is preferable to cool the outlet area of the oxygen electrode more than the inlet area.

[0089] 3. Water electrolysis system

[0090] 3.1. Basic configuration of the water electrolysis system

[0091] First, the basic configuration of the water electrolysis system will be described. The basic configuration of the water electrolysis system is the same as that of the known one, Figure 7 and the water electrolysis system 30 including this basic configuration is schematically shown in. The water electrolysis system 30 has the above-mentioned water electrolysis stack 20, a water supply side path (oxygen side path) 31, and a hydrogen side path 41. In the water electrolysis system 30, water for water electrolysis is supplied to the water electrolysis cell 12 of the water electrolysis stack 20 from the water supply side path 31, and electricity is applied using the power supply 30a to decompose the water into hydrogen and oxygen, and hydrogen is obtained and discharged to the hydrogen side path 41.

[0092] The power supply 10a is a DC power supply device that applies a voltage to the water electrolysis cell 10 as described above to perform water electrolysis, and a power supply equipped in a known water electrolysis system can be applied.

[0093] [Water supply side path (oxygen side path)]

[0094] The water supply side path (oxygen side path) 31 is a path including pipes for supplying water for water electrolysis to the water electrolysis cell 10 of the water electrolysis stack 20 to obtain oxygen.

[0095] In this method, in the water supply path 31, the pure water for electrolyzing water stored in the pure water tank 32 is supplied to the water electrolysis stack 20 by the power of the pump 33. A cooler for cooling water and an ion exchanger for removing ions contained in the water may be arranged between the pump 33 and the water electrolysis stack 20 as required.

[0096] In the water supply path 31, the oxygen generated in the water electrolysis stack 20 and the remaining unused water are also discharged from the water electrolysis stack 20 and supplied to the gas-liquid separator 34. In the gas-liquid separator 34, water and oxygen are separated, the separated oxygen is discharged, and the water is returned to the pure water tank 32. In addition, the insufficient water is supplied from the pump 35 to the pure water tank 32.

[0097] The above-mentioned various devices are connected by pipes to form a fluid path. In addition to the above-mentioned devices, known devices are arranged in the water supply path 31 as required.

[0098] [Hydrogen side path]

[0099] The hydrogen side path 41 is a path including a pipe for taking out hydrogen generated in the water electrolysis stack 20. In the hydrogen side path 41, the hydrogen discharged from the water electrolysis cell 10 of the water electrolysis stack 20 and the accompanying water are supplied to the gas-liquid separator 42. In the gas-liquid separator 42, water (accompanying water) and hydrogen are separated. The hydrogen separated by the gas-liquid separator 42 is dehumidified, etc. and stored in a tank. The water separated by the gas-liquid separator 42 is transported by the pump 43 to the pure water tank 32 in the water supply path 31 and reused. At this time, an ion separator may also be arranged as required before reaching the pure water tank 32.

[0100] In the hydrogen side path, these various devices are connected by pipes. In addition to the above-mentioned devices, known devices are arranged in the hydrogen side path 41 as required.

[0101] 3.2. Method 1

[0102] In the water electrolysis system 30 according to Method 1, in addition to the above basic configuration, as Figure 7 shown, a cooling fluid path 50 is further provided. The cooling fluid path 50 is a path for supplying a cooling fluid to the above-mentioned cooling fluid flow path 25 of the water electrolysis cell 10. The flow pattern and effect of the cooling fluid in the water electrolysis cell 10 are as described above.

[0103] The cooling fluid path 50 uses a pump 51 to convey the cooling fluid to a cooler 52. The cooling fluid whose temperature has been adjusted by the cooler 52 is conveyed to the cooling fluid inlet hole 10e of the water electrolysis cell 10. The cooling fluid used for cooling is collected from the cooling fluid outlet hole 10f of the water electrolysis cell 10 and returned to the pump 51. In the cooling fluid path 50, these devices are connected by pipes. In addition to the above arrangements, devices such as a temperature sensor and a flow sensor are also arranged as required in the cooling fluid path 50.

[0104] The adjustment of the cooling capacity of the cooling fluid can be carried out by adjusting the temperature based on the cooler 52 and adjusting the flow rate based on the pump 51. In addition, in this mode, the cooling fluid can be pure water or a refrigerant including ethylene glycol, propylene glycol, etc. Thus, since freezing can be prevented, applications in cold regions can also be realized.

[0105] 3.3. Mode 2

[0106] In the water electrolysis system 30 according to Mode 2, in addition to the above basic configuration, as Figure 8 shown, it also has a cooling fluid path 60.

[0107] The cooling fluid path 60 is a path for supplying the cooling fluid to the above-mentioned cooling fluid flow path 25 of the water electrolysis cell 10. The flow pattern and effect of the cooling fluid in the water electrolysis cell 10 are as described above.

[0108] The cooling fluid path 60 uses a pump 61 to convey the cooling fluid from the pure water tank 32 to a cooler 62. The cooling fluid whose temperature has been adjusted by the cooler 62 is conveyed to the cooling fluid inlet hole 10e of the water electrolysis cell 10. The cooling fluid used for cooling is collected from the cooling fluid outlet hole 10f of the water electrolysis cell 10 and discharged. In the cooling fluid path 60, these devices are connected by pipes. In addition to the above devices, devices such as a temperature sensor and a flow sensor are also arranged as required in the cooling fluid path 60.

[0109] The adjustment of the cooling capacity of the cooling fluid can be carried out by adjusting the temperature based on the cooler 62 and adjusting the flow rate based on the pump 61.

[0110] In addition, here the cooling fluid after being used for cooling is discharged (discarded), but it is not limited to this, and it can also be returned to the pure water tank 32 for reuse.

[0111] According to this mode, the water on the water supply side path can be utilized, and there is no need to prepare additional cooling fluid.

[0112] 3.4. Mode 3

[0113] In the water electrolysis system 30 according to Mode 3, in addition to the above basic configuration, as Figure 9 shown, a cooling fluid path 70 is further provided.

[0114] The cooling fluid path 70 is a path for supplying cooling fluid to the above-mentioned cooling fluid flow path 25 of the water electrolysis cell 10. The flow pattern and effect of the cooling fluid in the water electrolysis cell 10 are as described above.

[0115] The cooling fluid path 70 uses a pump 71 to transport the cooling fluid from the gas-liquid separator 42 in the hydrogen-side path to the cooler 72. The cooling fluid whose temperature has been adjusted by the cooler 72 is transported to the cooling fluid introduction hole 10e of the water electrolysis cell 10. The cooling fluid used for cooling is collected from the cooling fluid discharge hole 10f of the water electrolysis cell 10 and discharged. In the cooling fluid path 70, these various devices are connected by piping. In addition to the above-mentioned devices, devices such as a temperature sensor and a flow sensor are also arranged in the cooling fluid path 70 as needed.

[0116] The adjustment of the cooling capacity of the cooling fluid can be carried out by temperature adjustment based on the cooler 72 and flow adjustment based on the pump 71.

[0117] In addition, although the cooling fluid after being used for cooling is discharged (discarded) here, it is not limited to this, and it can also be returned to the pure water tank 32 for reuse.

[0118] According to this mode, it is possible to utilize the accompanying water on the hydrogen generation electrode side without preparing additional cooling fluid.

[0119] 3.5. Others

[0120] In addition, all surfaces of the flat water electrolysis cell can be cooled through the cooling fluid flow path, or a configuration for cooling a part of the area can also be adopted. For the cooling inside the water electrolysis cell, it is preferable to cool the outlet area of the oxygen electrode more than the inlet area.

[0121] Explanation of Reference Numerals

[0122] 10…Water electrolysis cell; 10a…Water electrolysis region; 10b…Oxygen electrode inlet hole; 10c…Oxygen electrode outlet hole; 10d…Hydrogen electrode outlet hole; 10e…Cooling fluid inlet hole; 10f…Cooling fluid outlet hole; 11…Solid polymer electrolyte membrane (electrolyte membrane); 12…Anode catalyst layer (catalyst layer); 13…Anode gas diffusion layer (oxygen electrode gas diffusion layer); 14…Anode separator (oxygen electrode separator); 14a…Water supply flow path for water electrolysis; 15…Cathode catalyst layer (catalyst layer); 16…Cathode gas diffusion layer (hydrogen electrode gas diffusion layer); 17…Cathode separator (hydrogen electrode separator); 20…Water electrolysis stack; 25…Cooling fluid flow path; 30…Water electrolysis system; 50, 60, 70…Cooling fluid paths.

Claims

1. A water electrolysis system that obtains hydrogen from a hydrogen electrode by supplying water to an oxygen electrode of a water electrolysis cell and applying a voltage to the water electrolysis cell, wherein, it has a cooling fluid path that supplies a cooling fluid different from the water to the water electrolysis cell through a second flow path different from a first flow path that supplies water to the oxygen electrode.

2. The water electrolysis system according to claim 1, wherein, the direction in which the cooling fluid flows is in a countercurrent relationship with respect to the direction in which the water flows.

3. The water electrolysis system according to claim 1 or 2, wherein, the cooling fluid is accompanying water discharged from the hydrogen electrode.

4. The water electrolysis system according to claim 1 or 2, wherein, the cooling fluid is water branched off from a path for supplying water to the oxygen electrode.

5. The water electrolysis system according to claim 1 or 2, wherein, the cooling fluid is water supplied from a gas-liquid separator provided on the hydrogen electrode side.

6. The water electrolysis system according to claim 1 or 2, wherein, the water electrolysis cell has a diaphragm at the oxygen electrode, the first flow path is formed on a first surface of the diaphragm, and the second flow path is formed on a second surface opposite to the first surface.

7. The water electrolysis system according to claim 1 or 2, wherein, the first flow path extends parallel to the second flow path.

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