Water electrolysis hydrogen production method and water electrolysis hydrogen production apparatus

Abstract

To suppress long-term degradation of an electrolysis stack by minimizing load fluctuation on the electrolysis stack.SOLUTION: A water electrolysis hydrogen production method comprises generating hydrogen by supplying power from a power storage unit 14 to an electrolysis stack 16 in a situation where both the power obtained from a renewable energy source PS and hydrogen demand are below a predetermined threshold, and storing the obtained hydrogen in a hydrogen storage unit 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for generating hydrogen by water electrolysis and a water electrolysis hydrogen generation device.

Background Art

[0002] In recent years, considering the environment, it has been considered to use hydrogen as a fuel for power generation, automobiles, etc., and the demand for hydrogen is increasing. In addition, a water electrolysis device that generates hydrogen from electricity has attracted attention from the viewpoints of energy storage and conversion. For example, in Patent Document 1 below, a water electrolysis unit that generates hydrogen by water electrolysis using the power supplied from a power generation unit using renewable energy, a hydrogen tank that stores the hydrogen obtained in the water electrolysis unit, and a fuel cell that generates power using hydrogen are provided, and a system that converts and stores the power from the power generation unit into hydrogen is disclosed. It is characterized by coping with the unstable renewable power and absorbing the daily power fluctuations.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to generate hydrogen by water electrolysis, for example, it is possible to use a water electrolysis device having a proton exchange membrane (PEM) that can easily follow power load fluctuations. Although PEM water electrolysis is an established technology, it requires a DC power source as a characteristic. Further, since the electrolysis stack that generates hydrogen with DC power operates at a low voltage, it has a configuration in which a large number of electrolysis stacks are integrated, so it is necessary to supply a large current to the water electrolysis device. Although it is a PEM water electrolysis device that can easily follow load fluctuations, when the state of not generating hydrogen at all with the input power set to 0 and the state of performing electrolysis with power input are repeated as an operation pattern, large changes occur in the temperature of the electrolysis stack, the electric field, the state of the generated gas, etc. For this reason, since a large electrical and mechanical variable load is applied to the electrode catalyst, the electrolyte membrane, etc., which are central members of the electrolysis stack, there is a concern that it may cause long-term deterioration of the electrolysis stack.

[0005] Therefore, the present invention has been made in view of the above prior art, and an object thereof is to suppress load fluctuations on the electrolysis stack and suppress long-term deterioration of the electrolysis stack.

Means for Solving the Problems

[0006] In order to achieve the above object, a water electrolysis hydrogen generation method according to the present invention is a water electrolysis hydrogen generation method for generating hydrogen with an electrolysis stack having a solid electrolyte membrane, wherein a lower limit value of the current value applied to the electrolysis stack is provided, and in a situation where the current value from the renewable energy power source is below the lower limit value, power with a current value of the lower limit value or more is continuously supplied from a second power supply source to the electrolysis stack to generate hydrogen.

[0007] In the water electrolysis hydrogen generation method according to the present invention, an electrolysis stack having a solid electrolyte membrane generates hydrogen by receiving power from a renewable energy power source. When the amount of power supplied from the renewable energy power source is low and the current value received by the electrolysis stack falls below the lower limit value, power equal to or higher than the lower limit value is supplied to the electrolysis stack from a second power supply source. Therefore, even when the amount of power supplied from the renewable energy power source is low, hydrogen generation in the electrolysis stack is continuously performed. That is, since a current value equal to or higher than the lower limit value is supplied to the electrolysis stack, hydrogen generation in the electrolysis stack is continued. For this reason, since power capable of generating hydrogen is constantly supplied to the electrolysis stack, it is possible to prevent electrical or mechanical load fluctuations from being applied to the electrode catalyst and the solid electrolyte membrane in the electrolysis stack. Therefore, it is possible to suppress deterioration of the electrolysis stack.

[0008] Further, the water electrolysis hydrogen generation method according to the present invention is a water electrolysis hydrogen generation method for generating hydrogen by a water electrolysis hydrogen generation device including an electrolysis stack having a solid electrolyte membrane, a power storage unit, and a hydrogen storage unit. In a situation where both the power obtained from the renewable energy power source and the hydrogen demand are lower than a predetermined threshold value, power is supplied from the power storage unit to the electrolysis stack to generate hydrogen, and the obtained hydrogen is stored in the hydrogen storage unit.

[0009] In the method for producing hydrogen by electrolyzing water according to the present invention, an electrolysis stack having a solid electrolyte membrane generates hydrogen by receiving power from a renewable energy power source. When the amount of power supplied from the renewable energy power source is low, power from the power storage unit is supplied to the electrolysis stack to generate hydrogen. Therefore, even when the amount of power supplied from the renewable energy power source is low, hydrogen generation in the electrolysis stack continues. For this reason, it is possible to prevent electrical or mechanical load fluctuations from being applied to the electrode catalyst and the solid electrolyte membrane in the electrolysis stack, thereby suppressing deterioration of the electrolysis stack. Moreover, since hydrogen generation continues even under a situation where hydrogen demand is low, the generated hydrogen tends to be surplus, but the obtained hydrogen is stored in the hydrogen storage unit. For this reason, even if hydrogen is continuously generated in the electrolysis stack, the hydrogen is not wasted.

[0010] The hydrogen storage unit may be composed of a hydrogen storage alloy container. In this aspect, hydrogen can be efficiently stored.

[0011] The water electrolysis hydrogen generation device according to the present invention is a water electrolysis hydrogen generation device that generates hydrogen with an electrolysis stack having a solid electrolyte membrane, the electrolysis stack, a hydrogen storage unit, and a switching unit that switches the power supply source to the electrolysis stack between a renewable energy power source and a second power supply source, and a lower limit value of the current value applied to the electrolysis stack is provided. In a situation where the current value from the renewable energy power source is below the lower limit value, the switching unit is controlled so that power having a current value equal to or higher than the lower limit value is supplied from the second power supply source to the electrolysis stack.

[0012] In the water electrolysis hydrogen generation device according to the present invention, an electrolysis stack having a solid electrolyte membrane receives electric power from a renewable energy power source, thereby generating hydrogen. When the amount of supplied electric power from the renewable energy power source is low and the current value received by the electrolysis stack falls below the lower limit value, the switching unit is switched, and electric power equal to or higher than the lower limit value is supplied from the second power supply source to the electrolysis stack. Therefore, even when the amount of supplied electric power from the renewable energy power source is low, it is possible to continuously generate hydrogen in the electrolysis stack. That is, by supplying a current value equal to or higher than the lower limit value to the electrolysis stack, it is possible to continuously generate hydrogen in the electrolysis stack. For this reason, since electric power capable of generating hydrogen is constantly supplied to the electrolysis stack, it is possible to prevent electrical or mechanical load fluctuations from being applied to the electrode catalyst and the solid electrolyte membrane in the electrolysis stack. Therefore, it is possible to suppress deterioration of the electrolysis stack.

[0013] Further, the water electrolysis hydrogen generation device according to the present invention is a water electrolysis hydrogen generation device that generates hydrogen with an electrolysis stack having a solid electrolyte membrane, the electrolysis stack, a power storage unit, a hydrogen storage unit, and a switching unit that switches the power supply source to the electrolysis stack between a renewable energy power source and the power storage unit, and a control unit that controls the switching unit so that power from the power storage unit is supplied to the electrolysis stack in a situation where both the power obtained from the renewable energy power source and the hydrogen demand are lower than a predetermined threshold value, and hydrogen obtained in the electrolysis stack is stored in the hydrogen storage unit in a situation where the hydrogen demand is lower than the predetermined threshold value.

[0014] In the water electrolysis hydrogen generation device according to the present invention, an electrolysis stack having a solid electrolyte membrane can generate hydrogen by receiving power from a renewable energy power source. When the amount of power supplied from the renewable energy power source is low, the switching unit is switched, and the power from the power storage unit is supplied to the electrolysis stack. Thereby, hydrogen is generated in the electrolysis stack. That is, even when the amount of power supplied from the renewable energy power source is low, it is possible to continuously generate hydrogen in the electrolysis stack. For this reason, it is possible to prevent electrical or mechanical load fluctuations from being applied to the electrode catalyst and the solid electrolyte membrane in the electrolysis stack, and thereby suppress deterioration of the electrolysis stack. Moreover, since hydrogen generation is continued even under a situation where hydrogen demand is low, the generated hydrogen tends to be surplus, but the obtained hydrogen is stored in the hydrogen storage unit. For this reason, even if hydrogen is continuously generated in the electrolysis stack, hydrogen is not wasted.

[0015] The hydrogen storage unit may be composed of a hydrogen storage alloy container.

[0016] The electrolysis stack and the hydrogen storage alloy container may be connected to a common cooling mechanism. In this aspect, the cooling water from the cooling mechanism can be supplied to both the electrolysis stack and the hydrogen storage alloy container. Therefore, an increase in component parts can be suppressed.

Advantages of the Invention

[0017] As described above, according to the present invention, it is possible to suppress long-term deterioration of the electrolysis stack by suppressing load fluctuations on the electrolysis stack.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

[0020] (First Embodiment) As shown in FIG. 1, a water electrolysis hydrogen production device 10 according to the first embodiment is configured to generate hydrogen by water electrolysis using electric power from a renewable energy power source PS and supply the generated hydrogen to a demand destination D. Also, surplus hydrogen can be stored. That is, it is configured to convert renewable energy into hydrogen, supply it to the demand destination D, and store surplus hydrogen. Specifically, the water electrolysis hydrogen production device 10 includes a power supply line 12 connected to the renewable energy power source PS, a power storage unit 14, an electrolysis stack 16, a hydrogen line 18, an oxygen line 19, and a hydrogen storage unit 20.

[0021] As the renewable energy power source PS, any type of generator capable of generating renewable energy such as a solar cell or a wind turbine generator may be used as long as it generates electric power using renewable energy. Since the amount of electric power obtained from the renewable energy power source PS is likely to fluctuate, the power storage unit 14 is provided for the case when the electric power supplied from the renewable energy power source PS decreases.

[0022] The power storage unit 14 may be configured to store the electric power when the electric power from the renewable energy power source PS is equal to or greater than a threshold value. Also, the power storage unit 14 may be configured to store the electric power received from another power source.

[0023] The power storage unit 14 is connected to the power supply line 12 via a switching unit 22. Since the power supply line 12 is connected to the electrolysis stack 16, the electric power from the renewable energy power source PS or the power storage unit 14 is supplied to the electrolysis stack 16.

[0024] The switching unit 22 is configured to be able to switch the power supply source to the electrolytic stack 16 between the renewable energy power source PS and the power storage unit 14. That is, the switching unit 22 can selectively take the normal state in which the power from the renewable energy power source PS is input to the electrolytic stack 16 and the auxiliary state in which the power is input to the electrolytic stack 16 from the power storage unit 14.

[0025] The operation of the switching unit 22 is controlled by the control unit 24. Without receiving a switching command from the control unit 24, the switching unit 22 is in the normal state. The control unit 24 is communicably connected to an ammeter 26 disposed at a site upstream of the switching unit 22 in the power supply line 12, and controls the switching unit 22 based on the measured value by this ammeter 26.

[0026] Specifically, the control unit 24 stores a lower limit value of the current value to be applied to the electrolytic stack 16. This lower limit value is the lower limit value of the current value required to continuously cause electrolysis in the electrolytic stack 16, produce the gas (hydrogen and oxygen) after electrolysis, discharge it from the electrolytic stack 16 at a stable pressure, and keep the pressure applied to the components of the electrolytic stack 16 from changing significantly. When the measured value by the ammeter 26 is equal to or greater than this stored lower limit value, the control unit 24 does not issue a switching command. On the other hand, when the measured value falls below this lower limit value, the control unit 24 issues a switching command. When receiving this switching command, the switching unit 22 switches from the normal state to the auxiliary state. Also, when the measured value returns from a situation where it is below the lower limit value to a value equal to or greater than the lower limit value, the control unit 24 issues a return command. Thereby, the switching unit 22 switches from the auxiliary state to the normal state.

[0027] The electrolysis stack 16 is composed of a polymer electrolyte water electrolysis device. That is, the electrolysis stack 16 has a structure in which a plurality of cells are connected in series, each cell including a polymer electrolyte membrane (PEM) with a catalyst layer (electrode catalyst) joined to both sides, an electrode (anode) located on one catalyst layer side, and an electrode (cathode) located on the other catalyst layer side. In the electrolysis stack 16, when DC power is supplied through the power supply line 12 and pure water is supplied through the water supply line 28, electrolysis of water is carried out to generate hydrogen and oxygen.

[0028] The generated oxygen may be exhausted through the oxygen line 19. On the other hand, the generated hydrogen is sent to the hydrogen demand destination D through the hydrogen line 18. However, since a branch line 30 provided with a hydrogen storage unit 20 is connected to the hydrogen line 18, at least a part of the hydrogen flowing through the hydrogen line 18 can be stored in the hydrogen storage unit 20 according to the hydrogen demand.

[0029] A switching mechanism 32 for switching the hydrogen supply destination from the demand destination D to the hydrogen storage unit 20 is provided in the hydrogen line 18 and the branch line 30. The switching mechanism 32 is configured to switch the hydrogen supply destination from the demand destination D to the hydrogen storage unit 20 based on a command from the control unit 24. This command is issued when the demand amount by the hydrogen demand destination D is lower than the threshold value. For example, when the control unit 24 detects that the pressure of the hydrogen flowing through the hydrogen line 18 has decreased when the demand from the demand destination D is strong, or when it belongs to a time zone when the hydrogen demand amount by the demand destination D decreases, the control unit 24 issues a command. Upon receiving this command, the switching mechanism 32 switches the state where the hydrogen generated in the electrolysis stack 16 is sent to the demand destination D to the state where it flows into the hydrogen storage unit 20.

[0030] The hydrogen storage unit 20 is composed of a hydrogen storage alloy container. That is, the hydrogen storage unit 20 includes a hydrogen storage alloy and a container that houses this hydrogen storage alloy, and is configured such that hydrogen is adsorbed by the hydrogen storage alloy and stored when the pressure inside the container reaches or exceeds the equilibrium pressure.

[0031] On the one hand, when the hydrogen storage alloy absorbs heat from the outside air, it releases the adsorbed hydrogen. Therefore, the hydrogen storage unit 20 is configured to be cooled by cooling water (cooling fluid). The cooling water is supplied from the cooling mechanism 34.

[0032] The cooling mechanism 34 is connected to a cooling circuit 36 that circulates the cooling water. The cooling circuit 36 includes a main flow path 36a, a first flow path 36b and a second flow path 36c that branch off from the main flow path 36a. The main flow path 36a is connected to the cooling mechanism 34. Both ends of the first flow path 36b are connected to the main flow path 36a, and the intermediate portion is connected to the electrolysis stack 16. Both ends of the second flow path 36c are connected to the main flow path 36a, and the intermediate portion is connected to the hydrogen storage unit 20. Therefore, the cooling water cooled by the cooling mechanism 34 flows through both the electrolysis stack 16 and the hydrogen storage unit 20 (hydrogen storage alloy container). That is, the electrolysis stack 16 and the hydrogen storage alloy container are connected to a common cooling mechanism 34.

[0033] Flow rate adjustment mechanisms are provided in the first flow path 36b and the second flow path 36c to adjust the ratio of dividing the flow rate of the cooling water cooled by the cooling mechanism 34 into the flow rate flowing through the electrolysis stack 16 and the flow rate flowing through the hydrogen storage unit 20. This flow rate adjustment mechanism includes valves 37 and flow meters 38 provided in the first flow path 36b and the second flow path 36c respectively for adjusting the flow rate. The valve 37 may be a manual valve. In this case, the flow rate distributed to the first flow path 36b and the second flow path 36c can be adjusted using the flow meter 38. For example, the flow rate adjustment mechanism can be adjusted according to the temperature of the electrolysis stack 16 and the temperature of the hydrogen storage unit 20.

[0034] The flow rate adjustment mechanism is not limited to being composed of the manually operated valve 37. For example, the valve 37 may be controlled for its opening degree by a controller or a control unit 24 (not shown). In this case, for example, when a measuring instrument for measuring the temperature of the electrolysis stack 16 is provided, if the measured temperature becomes higher than a specified value, the controller or the control unit 24 may perform control to increase the opening degree of the valve 37 disposed in the first flow path 36b. By this control, the temperature of the electrolysis stack 16 can be made closer to the specified value. Further, when a measuring instrument for measuring the temperature of the hydrogen storage unit 20 is provided, if the measured temperature becomes higher than a specified value, the controller or the control unit 24 may perform control to increase the opening degree of the valve 37 disposed in the second flow path 36c. Also, when the measured temperature becomes lower than the specified value, the controller or the control unit 24 may perform control to decrease the opening degree of the valve 37 disposed in the second flow path 36c. By these controls, the temperature of the hydrogen storage unit 20 can be maintained within a certain range.

[0035] Subsequently, a method for generating hydrogen by water electrolysis performed by the water electrolysis hydrogen generator 10 configured as described above will be described with reference to FIG. 2.

[0036] When receiving power supply from the renewable energy power source PS (step ST11), water electrolysis is performed in the electrolysis stack 16, and the hydrogen generated in the electrolysis stack 16 is supplied to the demand destination D. At this time, the ammeter 26 measures the value of the current flowing through the power supply line 12 toward the electrolysis stack 16 (step ST12). Then, the control unit 24 determines whether or not the measured current value is equal to or greater than the lower limit value stored in the control unit 24 (step ST13). If the measured value of the current is equal to or greater than the lower limit value stored in the control unit 24, the switching unit 22 is maintained in the normal state, so that the power from the renewable energy power source PS is supplied to the electrolysis stack 16.

[0037] On the one hand, when the measured value of the current, that is, the current value of the power supplied from the renewable energy power source PS, falls below the stored lower limit value, in response to this detection result, the control unit 24 issues a switching command. This command is input to the switching unit 22. When receiving the switching command, the switching unit 22 switches from the normal state to the auxiliary state (step ST14). As a result, the power supply source to the electrolytic stack 16 switches from the renewable energy power source PS to the power storage unit 14, and the power from the power storage unit 14 is supplied to the electrolytic stack 16. At this time, a current value equal to or higher than the lower limit value stored in the control unit 24 is supplied to the electrolytic stack 16. That is, in a situation where the power obtained from the renewable energy power source PS is lower than a predetermined threshold value, power is supplied from the power storage unit 14 to the electrolytic stack 16. In this way, when the power generation amount of the renewable energy power source PS decreases, by supplying power from the power storage unit 14 to the electrolytic stack 16, a current equal to or higher than the lower limit value is continuously supplied to the electrolytic stack 16. Therefore, in the electrolytic stack 16, since water electrolysis is constantly performed, hydrogen generation is continuously carried out.

[0038] The generated hydrogen is supplied to the hydrogen demand destination D through the hydrogen line 18. However, when a command for switching the switching mechanism 32 is issued from the control unit 24, the switching mechanism 32 is controlled so that the supply destination of the generated hydrogen changes (step ST15). As a result, the generated hydrogen is not sent to the demand destination D but is supplied to the hydrogen storage unit 20 and stored in the hydrogen storage unit 20. That is, in a situation where the hydrogen demand is lower than a predetermined threshold value, the obtained hydrogen is stored in the hydrogen storage unit 20. When a command for switching the switching mechanism 32 is issued again from the control unit 24, the switching mechanism 32 is switched again, so that the generated hydrogen is sent to the demand destination D again.

[0039] At this time as well, since the current value is constantly measured by the ammeter 26, it is determined whether the measured current value is equal to or greater than the lower limit value stored in the control unit 24 (step ST16). When it is determined that the current value has returned to the lower limit value or more, the control unit 24 issues a return command. As a result, the switching unit 22 switches from the auxiliary state to the normal state (step ST17), and the renewable energy power supply PS is supplied to the electrolytic stack 16.

[0040] As described above, in the present embodiment, the electrolytic stack 16 having the solid electrolyte membrane generates hydrogen by receiving power from the renewable energy power supply PS. When the amount of power supplied from the renewable energy power supply PS is low, the power from the power storage unit 14 is supplied to the electrolytic stack 16 to generate hydrogen. Therefore, even when the amount of power supplied from the renewable energy power supply PS is low, hydrogen generation is continuously performed in the electrolytic stack 16. For this reason, it is possible to prevent electrical or mechanical load fluctuations from being applied to the electrode catalyst and the solid electrolyte membrane in the electrolytic stack 16, thereby suppressing deterioration of the electrolytic stack 16. Moreover, since hydrogen generation is continued even under a situation where hydrogen demand is low, the generated hydrogen tends to be surplus, but the obtained hydrogen is stored in the hydrogen storage unit 20. For this reason, even if hydrogen is continuously generated in the electrolytic stack 16, the hydrogen is not wasted.

[0041] Also, in the present embodiment, since the hydrogen storage unit 20 is composed of a hydrogen storage alloy container, hydrogen can be efficiently stored.

[0042] Also, in the present embodiment, the cooling water from the cooling mechanism 34 can be supplied to both the electrolytic stack 16 and the hydrogen storage unit 20 (hydrogen storage alloy container). Therefore, an increase in components can be suppressed.

[0043] (Second Embodiment) As shown in FIG. 3, in the second embodiment, the power storage unit 14 is omitted, and the power supply line 12 is linked to the commercial power system CP. Also, the hydrogen storage unit 20 is omitted. Here, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

[0044] In the second embodiment, when the current value from the renewable energy power source PS falls below the lower limit value and the switching unit 22 is switched to the auxiliary state, the electrolysis stack 16 receives power from the commercial power system CP. That is, the commercial power system CP is an example of the second power supply source. However, since the power from the commercial power system CP is AC power, the switching unit 22 is connected to the commercial power system CP via a conversion unit 42 that converts AC to DC.

[0045] In the second embodiment, when the current value of the power supplied from the renewable energy power source PS falls below the lower limit value stored in the control unit 24, the switching unit 22 switches from the normal state to the auxiliary state (step ST14). As a result, the power from the commercial power system CP is converted to DC power and then supplied to the electrolysis stack 16. At this time, a current value equal to or higher than the lower limit value stored in the control unit 24 is supplied to the electrolysis stack 16. The hydrogen generated by the electrolysis stack 16 is supplied to the hydrogen demand destination D through the hydrogen line 18. In this embodiment, since the hydrogen storage unit 20 is omitted, step ST15 is omitted.

[0046] When it is determined that the current value measured by the ammeter 26 has returned to a value equal to or higher than the lower limit value, the control unit 24 issues a return command. As a result, the switching unit 22 switches from the auxiliary state to the normal state (step ST17), and the renewable energy power source PS is supplied to the electrolysis stack 16.

[0047] Therefore, in the present embodiment, the electrolysis stack 16 having a solid electrolyte membrane generates hydrogen by receiving power from the renewable energy power source PS. When the amount of power supplied from the renewable energy power source PS is low and the current value received by the electrolysis stack 16 falls below the lower limit value, power equal to or higher than the lower limit value is supplied to the electrolysis stack 16 from the commercial power grid CP. Therefore, even when the amount of power supplied from the renewable energy power source PS is low, hydrogen generation in the electrolysis stack 16 continues. That is, since a current value equal to or higher than the lower limit value is supplied to the electrolysis stack 16, hydrogen generation in the electrolysis stack 16 continues. For this reason, since power capable of generating hydrogen is constantly supplied to the electrolysis stack 16, electrical or mechanical load fluctuations are prevented from being applied to the electrode catalyst and the solid electrolyte membrane in the electrolysis stack 16. Therefore, deterioration of the electrolysis stack 16 can be suppressed.

[0048] In addition, in the second embodiment, a hydrogen storage unit 20 may also be provided. In that case, step ST15 will also be performed. Although descriptions of other configurations, operations, and effects are omitted, the description of the first embodiment can be incorporated into the second embodiment.

[0049] (Other Embodiments) It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The present invention is not limited to the above-described embodiments, and various changes, improvements, etc. are possible without departing from the gist thereof. For example, in the above-described embodiment, the hydrogen storage unit 20 is configured by a hydrogen storage alloy container, but it is not limited thereto. The hydrogen storage unit 20 may be configured by a hollow accumulator capable of storing hydrogen gas inside.

[0050] Also, in the above-described embodiment, cooling water is supplied from a common cooling mechanism 34 to the electrolysis stack 16 and the hydrogen storage alloy container. Instead of this, dedicated cooling mechanisms 34 may be provided for the electrolysis stack 16 and the hydrogen storage alloy container, respectively. Further, when the hydrogen storage unit 20 is configured by an accumulator, it is not necessary to supply cooling water to the hydrogen storage unit 20.

Description of Symbols

[0051] 10: Water electrolysis hydrogen generation device 14: Power storage unit 16: Electrolysis stack 20: Hydrogen storage unit No. 22: Switching unit No. 24: Control unit No. 34: Cooling mechanism PS: Renewable energy power source

Claims

1. A method for generating hydrogen by electrolyzing water using an electrolysis stack having a solid electrolyte membrane, wherein a lower limit value of the current value applied to the electrolysis stack is provided, and in a situation where the current value from the renewable energy power source is lower than the lower limit value, power with a current value equal to or higher than the lower limit value is continuously supplied from a second power source to the electrolysis stack to generate hydrogen.

2. A method for generating hydrogen by an electrolytic hydrogen generation apparatus including an electrolysis stack having a solid electrolyte membrane, a power storage unit, and a hydrogen storage unit, wherein in a situation where both the power obtained from the renewable energy power source and the hydrogen demand are lower than a predetermined threshold value, power is supplied from the power storage unit to the electrolysis stack to generate hydrogen, and the obtained hydrogen is stored in the hydrogen storage unit.

3. The method for generating hydrogen by electrolyzing water according to claim 2, wherein the hydrogen storage unit is composed of a hydrogen storage alloy container.

4. An electrolytic hydrogen generation apparatus for generating hydrogen using an electrolysis stack having a solid electrolyte membrane, comprising the electrolysis stack, a hydrogen storage unit, a switching unit for switching the power supply source to the electrolysis stack between a renewable energy power source and a second power source, and a control unit provided with a lower limit value of the current value applied to the electrolysis stack, and controlling the switching unit so that power with a current value equal to or higher than the lower limit value is supplied from the second power source to the electrolysis stack in a situation where the current value from the renewable energy power source is lower than the lower limit value. An electrolytic hydrogen generation apparatus.

5. An electrolytic hydrogen generation apparatus for generating hydrogen using an electrolysis stack having a solid electrolyte membrane, comprising the electrolysis stack, a power storage unit, a hydrogen storage unit, a switching unit for switching the power supply source to the electrolysis stack between a renewable energy power source and the power storage unit, and a control unit for controlling the switching unit so that power from the power storage unit is supplied to the electrolysis stack in a situation where both the power obtained from the renewable energy power source and the hydrogen demand are lower than a predetermined threshold value. The electrolytic hydrogen generation apparatus further comprises a hydrogen storage unit for storing hydrogen obtained by the electrolysis stack in a situation where the hydrogen demand is lower than the predetermined threshold value.

6. The electrolytic hydrogen generation apparatus according to claim 5, wherein the hydrogen storage unit is composed of a hydrogen storage alloy container.

7. The water electrolysis hydrogen generation device according to claim 6, wherein the electrolysis stack and the hydrogen storage alloy container are connected to a common cooling mechanism.

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