WO2020008687A1 - Water electrolysis system and water electrolysis method - Google Patents

Water electrolysis system and water electrolysis method Download PDF

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Publication number
WO2020008687A1
WO2020008687A1 PCT/JP2019/010939 JP2019010939W WO2020008687A1 WO 2020008687 A1 WO2020008687 A1 WO 2020008687A1 JP 2019010939 W JP2019010939 W JP 2019010939W WO 2020008687 A1 WO2020008687 A1 WO 2020008687A1
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Prior art keywords
water electrolysis
electrolysis device
hydrogen
concentration
power
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PCT/JP2019/010939
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French (fr)
Japanese (ja)
Inventor
祐介 佐々木
祥太 小川
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日立造船株式会社
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Publication of WO2020008687A1 publication Critical patent/WO2020008687A1/en

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/02—Hydrogen or oxygen
    • C25B1/04—Hydrogen or oxygen by electrolysis of water
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B15/00—Operating or servicing cells
    • C25B15/02—Process control or regulation
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/70—Assemblies comprising two or more cells
    • C25B9/73—Assemblies comprising two or more cells of the filter-press type
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Definitions

  • the present invention relates to a water electrolysis system and a water electrolysis method.
  • a water electrolysis device can produce hydrogen by electrolyzing water.
  • the produced hydrogen is used for, for example, a fuel cell.
  • a water electrolysis device for example, a water electrolysis device (hereinafter, referred to as an alkaline water electrolysis device) disclosed in Patent Literature 1 that generates hydrogen by electrolyzing an electrolytic solution containing alkaline water is given.
  • water is electrolyzed in the vicinity of the anode to generate protons, and the obtained protons are moved to the vicinity of the cathode through an electrolyte containing a polymer, and the protons receive electrons in the vicinity of the cathode to generate hydrogen.
  • a water electrolysis device (hereinafter, referred to as a polymer type water electrolysis device) is also included.
  • Non-Patent Document 1 discloses an example of a system combining a wind power generation facility and a polymer water electrolysis device.
  • the alkaline water electrolysis apparatus has the advantage that it can be easily increased in size due to its simple structure, and can reduce the initial cost per unit hydrogen production amount, as compared with the polymer water electrolysis apparatus.
  • the alkaline water electrolysis apparatus when the electrolytic solution is electrolyzed, oxygen is generated near the anode of the electrolytic electrode, and hydrogen is generated near the cathode.
  • an alkaline water electrolysis apparatus a part of the anode becomes a cathode through the electrolytic solution and the metal member in the electrolytic cell because the electrolytic solution has conductivity, and hydrogen is generated at a place where oxygen should originally be generated, so that oxygen and oxygen are generated. A mixed gas of hydrogen is produced. Similarly, oxygen is also partially generated at the cathode. This is known as stray current and is a phenomenon unique to an alkaline water electrolysis device. In particular, when hydrogen generated on the anode side exceeds a hydrogen concentration of 4% in oxygen, the reaction between hydrogen and oxygen may be a chain reaction.
  • the electric power supplied to the water electrolysis device it is conceivable that electric power generated using natural energy such as sunlight or wind power is used.
  • the power generation amount is generally not constant and fluctuates under the influence of natural phenomena.
  • the concentration of hydrogen contained in oxygen generated at the anode increases due to the relative increase in stray current. Therefore, the reactivity between the generated oxygen and hydrogen is increased, which may affect the operation of the water electrolysis apparatus. That is, in order to operate the water electrolysis apparatus, it is desired to develop a technique for suppressing an increase in the concentration of hydrogen contained in the generated oxygen.
  • Patent Document 1 in order to maintain the purity of hydrogen gas generated in an alkaline water electrolysis apparatus, a rectifier for rectifying electricity supplied from outside the system, an electrolytic cell, and a rectifier and an electrolytic cell. A switch circuit is provided between them. Then, a technique is disclosed in which the number of electrolytic cells connected to the rectifier is adjusted by controlling the switch circuit in accordance with the supplied power. Further, the rectifier is provided with a storage battery for storing a current applied to the electrolytic cell. According to this technology, even when the power supplied from the power supply fluctuates, the power supplied to the alkaline water electrolysis device can be kept constant, and the purity of the hydrogen gas generated from the water electrolysis device can be reduced. Can be kept.
  • Patent Document 1 By diverting the technique disclosed in Patent Document 1, it is considered that an increase in the concentration of hydrogen in oxygen generated at the anode can be suppressed.
  • the structure of the water electrolysis device is complicated.
  • the switch circuit may be consumed in a short time.
  • the present application easily suppresses an increase in the concentration of hydrogen in oxygen generated from the water electrolysis device even when the power supplied from the power supply to the water electrolysis device fluctuates, and affects the operation of the water electrolysis device. It is an object of the present invention to provide a technology for suppressing the effect of
  • the present invention includes a first water electrolysis device and a second water electrolysis device, and supplies power supplied from a power supply to the first water electrolysis device and the second water electrolysis device.
  • the water electrolysis system to be distributed was decided.
  • the present invention has a first electrolytic cell having a first electrolytic electrode immersed in a first electrolytic solution and generating hydrogen and oxygen by applying a voltage between the first electrolytic electrodes.
  • the apparatus has a second electrolytic electrode immersed in a second electrolytic solution having a lower conductivity than the first electrolytic solution, and generates hydrogen by applying a voltage between the second electrolytic electrodes.
  • the second water electrolysis device and the first water electrolysis device and the second water electrolysis device according to the power supplied from the power supply outside the system so as to suppress an increase in the hydrogen concentration in oxygen generated from the first water electrolysis device.
  • a control means for controlling power supplied to the second water electrolysis device.
  • the external power supply means a power supply existing outside the water electrolysis system.
  • the first water electrolysis device oxygen is generated near the anode of the first electrolysis electrode, and hydrogen is generated near the cathode. Further, since the first electrolytic solution has higher conductivity than the second electrolytic solution, the first water electrolysis device easily generates a stray current. When the power distributed to the first water electrolysis device is small, there is a possibility that hydrogen near the anode and oxygen near the cathode may be generated due to a relatively increased stray current. That is, the concentration of hydrogen contained in oxygen generated near the anode may increase.
  • the first water electrolysis device is controlled according to the power supplied from a power supply outside the system so as to suppress the increase in the hydrogen concentration in oxygen generated from the first water electrolysis device.
  • the power supplied to the water electrolysis device can be suitably controlled. Therefore, it is suppressed that the operation of the water electrolysis system is affected.
  • an increase in the concentration of oxygen contained in hydrogen generated near the cathode of the first water electrolysis device can be suppressed.
  • the first water electrolysis device is an alkaline water electrolysis device in which the first electrolytic solution contains an alkaline aqueous solution, and the control means, when the power supplied from the power supply is equal to or less than a predetermined threshold, The supply of electric power to the first water electrolysis device may be stopped.
  • the predetermined threshold value may be electric power for rapidly increasing the concentration of hydrogen in oxygen generated from the first water electrolysis device.
  • the predetermined threshold may be electric power for generating oxygen containing hydrogen at a concentration that avoids operation of the first water electrolysis device.
  • the predetermined threshold value may be a value that allows a current of 40% of the rated current of the first water electrolysis device to flow to the first water electrolysis device.
  • the second water electrolysis device includes an electrolyte containing a polymer, and a second electrolytic electrode immersed in a second electrolyte having lower conductivity than the first electrolyte is provided with the electrolyte interposed therebetween.
  • a polymer-type water electrolysis device that generates hydrogen by applying a voltage between the second electrolysis electrodes may be used.
  • the control means may control electric power supplied to the first water electrolysis device and the second water electrolysis device according to the concentration of hydrogen contained in oxygen generated from the first water electrolysis device.
  • the control unit may include a switching unit that switches a water electrolysis device connected to a power source between the first water electrolysis device and the second water electrolysis device.
  • control means in a state where power supply to the first water electrolysis device is stopped, when the concentration of hydrogen contained in oxygen generated from the first water electrolysis device is equal to or less than the first concentration,
  • the concentration of hydrogen contained in oxygen generated from the first water electrolysis device is equal to or less than the first concentration.
  • the control means in a state where power supply to the first water electrolysis device is stopped, when the concentration of hydrogen contained in oxygen generated from the first water electrolysis device is equal to or less than the first concentration, when the power supplied from the power supply becomes larger than the first operation start threshold, the supply of power to the first water electrolysis device is restarted, and the concentration of hydrogen contained in oxygen generated from the first water electrolysis device is increased. Is greater than the first concentration, even if the power supplied from the power supply is greater than the first operation start threshold, does not restart the supply of power to the first water electrolysis device, When the supplied electric power becomes larger than the second operation start threshold larger than the first operation start threshold, the supply of electric power to the first water electrolysis device may be restarted.
  • the control means may change the predetermined threshold value according to the concentration of hydrogen contained in oxygen generated from the first water electrolysis device.
  • the present invention can also be grasped from the aspect of a method. That is, for example, a first water electrolysis device that has a first electrolytic electrode immersed in a first electrolytic solution and generates hydrogen and oxygen by applying a voltage between the first electrolytic electrodes, A second water electrolysis having a second electrolytic electrode immersed in a second electrolytic solution having lower conductivity than the one electrolytic solution, and generating hydrogen by applying a voltage between the second electrolytic electrodes.
  • Water electrolysis method which includes a control step for performing control as described above.
  • the above-described water electrolysis system can easily suppress an increase in the hydrogen concentration in oxygen generated from the water electrolysis device even when the power supplied from the power supply to the water electrolysis device fluctuates, and operate the water electrolysis device. Provide technology that suppresses the influence of
  • FIG. 1 shows an example of an outline of a water electrolysis system according to an embodiment of the present invention.
  • FIG. 2 shows an example of an outline in which, in a power plant that sells power generated by renewable energy, power that cannot be sold due to output limitation or the like is supplied to the water electrolysis system.
  • FIG. 3 shows an example in which electric power generated in the power generation facility is supplied to the water electrolysis system via a system.
  • FIG. 4 shows an example of a flowchart showing an outline of the operation of the water electrolysis system.
  • FIG. 5 shows an example of a temporal change of the power generated in the wind power generation facility.
  • FIG. 6 shows an example of the relationship between the current applied to the electrolytic electrode of the alkaline water electrolysis device and the concentration of hydrogen in oxygen.
  • FIG. 1 shows an example of an outline of a water electrolysis system according to an embodiment of the present invention.
  • FIG. 2 shows an example of an outline in which, in a power plant that sells power generated by renewable energy, power that cannot be sold
  • FIG. 7 shows an example of a comparison between the hydrogen concentration in oxygen generated from the alkaline water electrolysis device of the water electrolysis system and the hydrogen concentration in oxygen generated when only the alkaline water electrolysis device is operated. I have.
  • FIG. 8 shows a change with time of the measured value of the hydrogen concentration in oxygen generated from the alkaline water electrolysis device of the water electrolysis system.
  • FIG. 1 shows an example of an outline of a water electrolysis system 100 according to an embodiment of the present invention.
  • the water electrolysis system 100 includes an alkaline water electrolysis device 1 and a polymer water electrolysis device 2.
  • the water electrolysis system 100 is a system that simultaneously operates the alkaline water electrolysis device 1 and the polymer water electrolysis device 2.
  • the alkaline water electrolysis device 1 is, for example, a water electrolysis device having an electrolytic solution of a potassium hydroxide aqueous solution or a sodium hydroxide aqueous solution having a concentration of about 30% by weight.
  • the aqueous potassium hydroxide solution or the aqueous sodium hydroxide solution is an example of the “first electrolytic solution” of the present invention.
  • the polymer water electrolysis device 2 is a water electrolysis device having the electrolyte 5 containing a polymer.
  • the alkaline water electrolysis device 1 is an example of the “first water electrolysis device” of the present invention.
  • the polymer water electrolysis device 2 is an example of the “second water electrolysis device” of the present invention.
  • the water electrolysis system 100 includes an oxygen concentration meter that measures the concentration of oxygen in hydrogen generated from the alkaline water electrolysis device 1 and a hydrogen concentration meter that measures the concentration of hydrogen in oxygen. Although not shown, the water electrolysis system 100 also includes an oxygen concentration meter that measures the concentration of oxygen in hydrogen generated from the polymer water electrolysis device 2 and a hydrogen concentration meter that measures the concentration of hydrogen in oxygen. .
  • the water electrolysis system 100 also includes AC / DC converters 6A and 6B that convert an AC current into a DC current when the current supplied from a power source such as a solar power generation facility or a wind power generation facility is an AC current.
  • the AC / DC converters 6A and 6B have a function of rectifying an alternating current to a direct current and a function of controlling the direct current to a commanded value.
  • the alkaline water electrolysis apparatus 1 includes an electrolytic electrode including an anode 3A and a cathode 3B.
  • the anode 3A and the cathode 3B are examples of the “first electrolytic electrode” of the present invention.
  • the direct current converted by the AC / DC converter 6A is supplied to the anode 3A and the cathode 3B of the alkaline water electrolysis device 1.
  • the polymer type water electrolysis device 2 includes an electrolytic electrode including an anode 4A and a cathode 4B provided with the electrolyte 5 interposed therebetween.
  • the anode 4A and the cathode 4B are an example of the “second electrolytic electrode” of the present invention.
  • the surfaces of the anode 4A and the cathode 4B are immersed in pure water.
  • pure water is an example of the “second electrolytic solution” of the present invention, and has lower conductivity than the first electrolytic solution of the alkaline water electrolysis device 1.
  • the DC current converted by the AC / DC converter 6B is supplied to the anode 4A and the cathode 4B of the polymer water electrolysis device 2.
  • the water electrolysis system 100 controls the AC / DC converters 6A and 6B in accordance with the power supplied from the power supply to the water electrolysis system 100, and adjusts the distribution of power supplied from the power supply to each water electrolysis device (PLC). (Programmable Logic Controller) 7.
  • PLC Process Control Logic Controller
  • the PLC 7 controls the AC / DC converters 6A and 6B
  • the water electrolysis device connected to the power source can be switched between the alkaline water electrolysis device 1 and the polymer water electrolysis device 2.
  • the AC / DC converters 6A and 6B and the PLC 7 are examples of the "control means” and the "switching means” of the present invention.
  • the PLC 7 can control the AC / DC converters 6A and 6B according to the measurement values of the oxygen concentration meter or the hydrogen concentration meter, and adjust the distribution of the power supplied from the power supply to each water electrolysis device.
  • the water electrolysis system 100 also includes a hydrogen tank 8 for storing hydrogen generated in the alkaline water electrolysis device 1 and the polymer water electrolysis device 2.
  • the hydrogen stored in the hydrogen tank 8 is used for, for example, a fuel cell.
  • the water electrolysis system 100 releases oxygen generated from the alkaline water electrolysis device 1 or the polymer water electrolysis device 2 into the atmosphere, but it goes without saying that oxygen may be stored and used.
  • the alkaline water electrolysis apparatus 1 since the electrolytic solution has high conductivity, a part of the anode 3A becomes a cathode through the electrolytic solution and the metal member in the electrolytic cell, and hydrogen is generated in a place where oxygen should be generated. The hydrogen mixes with the oxygen at. Similarly, oxygen is also partially generated in the cathode 3B, and oxygen is mixed with the generated hydrogen. This is known as stray current and is a phenomenon unique to an alkaline water electrolysis device.
  • the concentration of hydrogen contained in oxygen generated at the anode 3A increases due to the relative increase of the stray current.
  • the reaction between hydrogen and oxygen may be a chain reaction as described above. Therefore, when hydrogen is generated using the alkaline water electrolysis apparatus 1, it is necessary to adjust the power supplied to the alkaline water electrolysis apparatus 1 so that the above-described chemical reaction between hydrogen and oxygen does not form a chain reaction. is there. Normally, the operation of the system or the device is prohibited in the region of the hydrogen concentration where the chemical reaction between hydrogen and oxygen may become a chain reaction, and is also treated as the operation prohibited region in the present embodiment.
  • a region where the hydrogen concentration in oxygen is lower than 2% and in which the hydrogen concentration in oxygen sharply increases is treated as a driving caution region.
  • the oxygen concentration in the hydrogen generated on the cathode 3B side increases as compared with the steady state described later, in the same manner as the hydrogen concentration in the oxygen generated on the anode 3A side increases.
  • the purity of the hydrogen produced is reduced. Therefore, the operation of the water electrolysis system 100 may be affected.
  • the operation region excluding the operation prohibition region, the operation avoidance region, and the operation caution region is an operation region used as a steady state. During operation in such a region, sufficient power is supplied to the alkaline water electrolysis apparatus 1. When the operation is performed in such a region, oxygen in a state where the hydrogen concentration in oxygen is low is generated, so that the hydrogen concentration at the anode can be reduced. Therefore, such a steady state can be regarded as a concentration recovery region.
  • the electrolyte 5 containing a polymer is provided between the anode 4A and the cathode 4B.
  • a voltage is applied between the anode 4A and the cathode 4B, and pure water is caused to flow in the vicinity of the anode 4A, so that protons and oxygen molecules are generated in the vicinity of the anode 4A.
  • the generated protons move to the cathode 4B via the electrolyte 5.
  • protons receive electrons, and hydrogen molecules are generated.
  • the polymer water electrolysis apparatus 2 has a function of reducing the amount of hydrogen contained in the generated oxygen even when the current supplied to the polymer water electrolysis apparatus 2 fluctuates. Concentrations fall in the range of hundreds to thousands of ppm and do not rise sharply. This is because the polymer type water electrolysis apparatus uses pure water, and generation of a problematic stray current is suppressed.
  • FIG. 2 shows an example of an outline in which in a power plant that sells power generated by renewable energy such as sunlight or wind power, power that cannot be sold due to output limitation or the like is supplied to the water electrolysis system 100.
  • the power plant includes a power generation facility 50 that generates power using renewable energy such as sunlight or wind power.
  • the power generation equipment 50 is in the same site as the water electrolysis system 100. Then, in the example of FIG. 2, of the power generated by the power generation facility 50, surplus power that cannot be sold to the power system is supplied to the water electrolysis system 100.
  • the above-mentioned power plant may have a load facility such as a factory in the same premises as the power generation facility 50 without being connected to the power system. Then, in a closed environment that is not connected to the power system, the surplus power that cannot be consumed by the load equipment may be supplied to the water electrolysis system 100.
  • the water electrolysis system 100 may obtain electric power from an external power supply outside the premises via a power system.
  • FIG. 3 illustrates an example in which the power generation facility 50 is not located on the same site as the water electrolysis system 100, and the power generated in the power generation facility 50 is supplied to the water electrolysis system 100 via a system.
  • the power command information which is the value of the power supplied to the water electrolysis system 100, may be obtained from any location.
  • FIG. 4 shows an example of a flowchart showing an outline of the operation of the water electrolysis system 100.
  • Step S101 power supply for electrolysis in the water electrolysis system 100 is started.
  • power generated by a power source such as a solar power generation facility or a wind power generation facility is supplied to the water electrolysis system 100.
  • FIG. 5 shows an example of a temporal change of the power generated in the wind power generation facility.
  • the power generation by wind power is not constant but fluctuates. That is, in power generation using natural energy such as a solar power generation facility or a wind power generation facility, the power fluctuates, and such fluctuated power is supplied to the water electrolysis system 100.
  • the PLC 7 acquires the value of the power supplied to the water electrolysis system 100 from the power supply.
  • Step S102 the PLC 7 determines whether the power supplied from the power supply is larger than a predetermined value.
  • FIG. 6 shows an example of the relationship between the current flowing into the electrolytic electrode of the alkaline water electrolysis apparatus 1 and the concentration of hydrogen contained in oxygen generated at the anode 3A of the electrolytic electrode.
  • the rated current of the alkaline water electrolysis device 1 is 0.6 Acm ⁇ 2 .
  • the hydrogen concentration in the region where the supplied current is large is not shown, it is constant at substantially the same concentration as that of the right end of the portion shown.
  • the current density of 0.18 Acm ⁇ 2 is power corresponding to a current of 30% of the rated current of the alkaline water electrolysis device 1 of the first operation example.
  • the predetermined value is set to electric power corresponding to 30% of the rated current of the alkaline water electrolysis device 1.
  • the predetermined value in the concentration recovery region By setting the predetermined value in the concentration recovery region in this manner, when sufficient power is supplied to the water electrolysis system 100, the alkaline water electrolysis apparatus 1 is positively operated, and the hydrogen in oxygen on the anode 4A side is hydrogen.
  • the concentration can be reduced. That is, the predetermined value serves as an operation start threshold value for restoring the hydrogen concentration of the anode.
  • reducing the concentration of hydrogen in oxygen on the side of the anode 4A may be referred to as recovery.
  • Step S103 In step S103, if it is determined in step S102 that the power supplied from the power supply is larger than the predetermined value, the PLC 7 determines power supply to the alkaline water electrolysis device 1. When power supply to the alkaline water electrolysis device 1 is determined, the supply current to the alkaline water electrolysis device 1 is determined from the internal state (mainly voltage) of the alkaline water electrolysis device 1.
  • Step S104 if it is determined in step S102 that the power supplied from the power supply is equal to or less than the predetermined value, the PLC 7 determines whether the concentration of hydrogen in oxygen generated in the alkaline water electrolysis device 1 is higher than the predetermined concentration value. Is determined.
  • the predetermined concentration value may be appropriately determined, but is set to a concentration at which a chemical reaction between at least generated oxygen and hydrogen contained in oxygen does not form a chain reaction.
  • the concentration may be set to 20,000 ppm, which is half the concentration of 40,000 ppm at which the chemical reaction between hydrogen and oxygen becomes a chain reaction, or may be set to 11,000 ppm, which is smaller.
  • 20,000 ppm or more and less than 40000 ppm correspond to the hydrogen concentration in the operation avoidance region
  • 11,000 ppm or more and less than 20,000 ppm correspond to the hydrogen concentration in the operation caution region.
  • Step S105 In step S105, if it is determined in step S104 that the hydrogen concentration in oxygen is higher than the predetermined concentration value, the PLC 7 determines not to supply a current to the alkaline water electrolysis device 1.
  • Step S106 In step S106, if it is determined in step S104 that the hydrogen concentration in oxygen is equal to or lower than the predetermined concentration value, the PLC 7 determines whether a predetermined period has elapsed from the time when the hydrogen concentration was determined to be higher than the predetermined concentration value. It is determined whether or not it is.
  • step S106 If it is determined in step S106 that the certain period has not elapsed from the time when the hydrogen concentration is determined to be higher than the predetermined concentration value, the process of step S105 is performed, and the PLC 7 performs the processing in the alkaline water electrolysis apparatus 1. Decide not to supply current to
  • Step S107 when it is determined in step S106 that the certain period has elapsed from the time in which the hydrogen concentration is determined to be higher than the predetermined concentration value, the PLC 7 determines whether the alkaline water electrolysis apparatus 1 is operating. Is determined.
  • Step S108 when it is determined in step S107 that the alkaline water electrolysis apparatus 1 is operating, the PLC 7 determines whether or not the power supplied from the power supply is larger than the operation continuation threshold of the alkaline water electrolysis apparatus 1. Is determined.
  • the operation continuation threshold value is set to a value such that when the supplied electric power becomes equal to or less than this value, the concentration of hydrogen contained in oxygen generated from the alkaline water electrolysis apparatus 1 sharply increases. That is, the value is set in the driving caution area described above. Therefore, the operation continuation threshold value is lower than the predetermined value in step S102.
  • a threshold value of the electric power at which the concentration of hydrogen contained in oxygen generated from the alkaline water electrolysis device 1 rapidly increases for example, in FIG.
  • a current value that increases the concentration (current density of 0.18 Acm ⁇ 2 ) may be employed. Further, a lower current value may be employed. By employing a lower current value in the driving caution region, the alkaline water electrolysis apparatus 1 can be used for a longer time.
  • a power value corresponding to 0.06 Acm ⁇ 2 is set as such an operation continuation threshold. This is power corresponding to 10% of the rated current of the alkaline water electrolysis device 1.
  • step S108 If it is determined in step S108 that the power supplied from the power supply is larger than the operation continuation threshold, the process of step S103 is performed, and the supply current from the AC / DC converter 6A to the alkaline water electrolysis device 1 is determined. .
  • step S108 If it is determined in step S108 that the power supplied from the power supply is equal to or less than the operation continuation threshold, the process of step S105 is performed, and the PLC 7 determines not to supply a current to the alkaline water electrolysis apparatus 1.
  • Step S109 when it is determined in step S107 that the alkaline water electrolysis apparatus 1 is not operating, it is determined whether the power supplied from the power supply is larger than the operation start threshold value of the alkaline water electrolysis apparatus 1.
  • the operation start threshold is a value provided for the purpose of preventing frequent ON / OFF switching that may occur when ON / OFF control of the operation of the alkaline water electrolysis apparatus 1 is performed only with the operation continuation threshold. is there. For this reason, although it is set to a value slightly higher than the operation continuation threshold, it is set to a value close to the operation continuation threshold.
  • step S103 when it is determined that the power supplied from the power supply is larger than the operation start threshold value of the alkaline water electrolysis device 1, the process of step S103 is executed, and the AC / DC converter 6A transfers the alkaline water electrolysis device 1 to the alkaline water electrolysis device 1. Is determined.
  • step S105 when it is determined that the electric power supplied from the power supply is equal to or less than the operation start threshold value of the alkaline water electrolysis device 1, the process of step S105 is executed, and the PLC 7 supplies a current to the alkaline water electrolysis device 1. Decide not to.
  • Step S110 the process in step S105 is performed, and after determining that the PLC 7 does not supply current to the alkaline water electrolysis device 1, the PLC 7 determines whether the polymer water electrolysis device 2 is operating. I do.
  • Step S111 In step S111, when it is determined in step S110 that the polymer water electrolysis device 2 is operating, the PLC 7 determines whether the power supplied from the power supply is larger than the operation continuation threshold of the polymer water electrolysis device 2. It is determined whether or not it is. In the polymer water electrolysis apparatus 2 of the first operation example, since pure water is used as the electrolytic solution, the operation continuation threshold of the polymer water electrolysis apparatus 2 is set to almost zero.
  • Step S112 if it is determined in step S111 that the power supplied from the power supply is larger than the operation continuation threshold of the polymer water electrolysis device 2, the PLC 7 supplies a current to the polymer water electrolysis device 2. To determine. Further, the PLC 7 determines a supply current to the polymer-type water electrolysis device 2.
  • Step S113 In step S113, if it is determined in step S111 that the power supplied from the power supply is equal to or less than the operation continuation threshold value of the polymer water electrolysis device 2, the PLC 7 does not supply a current to the polymer water electrolysis device 2. To determine.
  • step S113 The above-described processing in step S113 is also executed after the supply of current to the alkaline water electrolysis apparatus 1 is determined in step S103.
  • Step S114 In step S114, when it is determined in step S110 that the polymer water electrolysis device 2 is not in operation, the PLC 7 determines whether the power supplied from the power supply is larger than the operation start threshold value of the polymer water electrolysis device 2. It is determined whether or not it is.
  • step S114 When it is determined in step S114 that the power supplied from the power supply is greater than the operation start threshold value of the polymer water electrolysis device 2, the process of step S112 is executed, and the polymer water electrolysis is performed by the AC / DC converter 6B. The supply current to the device 2 is determined.
  • step S114 When it is determined in step S114 that the power supplied from the power supply is equal to or less than the operation start threshold value of the polymer water electrolysis device 2, the process of step S113 is executed, and the PLC 7 Decide not to supply current to Note that the operation start threshold value of the polymer water electrolysis device 2 of Operation Example 1 is set to be slightly higher than the operation continuation threshold value of the polymer water electrolysis device 2.
  • Step S115 the current command values created by the PLC 7 are transmitted to the AC / DC converters 6A and 6B, respectively.
  • the AC / DC converters 6A and 6B convert the power supplied from the power supply into a predetermined DC current based on the received current command value. Then, the current is output to the alkaline water electrolysis device 1 and the polymer water electrolysis device 2, respectively.
  • the power supplied from the power supply is changed to a power value corresponding to a current value of 10% of the rated current of the alkaline water electrolysis apparatus 1. It is determined whether it is greater than or equal to.
  • the process of step S105 is executed to thereby execute the alkaline water electrolysis device. The supply of current to 1 is stopped. Then, a current is supplied to the polymer-type water electrolysis device 2 by performing the process of step S112.
  • the threshold value for controlling the operation of the alkaline water electrolysis apparatus 1 may be set to an electric power value corresponding to the concentration at which the hydrogen concentration in the generated oxygen is relatively high. It becomes possible.
  • the polymer-type water electrolysis device 2 includes an electrolyte 5 containing a polymer, and an anode 4A and a cathode 4B immersed in pure water are provided with the electrolyte 5 interposed therebetween. Then, when current flows into the anode 4A and the cathode 4B, protons and oxygen are generated from pure water near the anode 4A, the protons are moved to the vicinity of the cathode 4B via the electrolyte 5, and hydrogen is removed from the vicinity of the cathode 4B. Is occurring. In such a polymer water electrolysis device 2, generation of stray current is suppressed even when the device is operated at a low load.
  • FIG. 7 shows the concentration of hydrogen contained in oxygen generated from the anode 3A of the alkaline water electrolysis apparatus 1 when the water electrolysis system 100 is actually operated as in Operation Example 1, and only the alkaline water electrolysis apparatus. 5 shows an example of comparison with the concentration of hydrogen contained in oxygen generated from the anode when the device is operated. As shown in FIG. 7, the power supplied from the wind power generation equipment to the water electrolysis device is fluctuating.
  • the hydrogen concentration in oxygen generated from the alkaline water electrolysis device 1 of the water electrolysis system 100 is from 9000 ppm to 10000 ppm, and the hydrogen concentration in oxygen generated when only the alkaline water electrolysis device is operated (11000 ppm) From 12000 ppm). That is, from FIG. 7, it is recognized that the water electrolysis system 100 can suppress an increase in the concentration of hydrogen in oxygen generated from the alkaline water electrolysis apparatus 1 even when the power supplied from the power supply fluctuates. Therefore, when the water electrolysis system 100 is operated as in the operation example 1, the operation of the water electrolysis system 100 is not affected. Note that there is a point where the hydrogen concentration is significantly increased at the beginning of the operation period. However, this is a portion generated to increase the current from zero, and is excluded when verifying the effect.
  • the operation continuation threshold value of the alkaline water electrolysis apparatus 1 in step S108 and the operation start threshold value of the alkaline water electrolysis apparatus 1 in step S109 are set to about 10% of the rated current of the alkaline water electrolysis apparatus 1. May be passed to the alkaline water electrolysis apparatus 1.
  • the present invention is not limited to this, and may be appropriately set in the range of 10% to 30% of the rated current of the alkaline water electrolysis device 1 corresponding to the above-mentioned driving caution region.
  • a lower value it is possible to widen the range of supply power that the alkaline water electrolysis apparatus 1 can operate.
  • a higher value it is possible to further prevent an increase in the hydrogen concentration on the anode 4A side.
  • the rated current of the alkaline water electrolysis apparatus 1 corresponding to the driving avoidance region may be employed instead of the driving caution region. By performing such operation, the operation range of the alkaline water electrolysis device 1 can be expanded.
  • the power value corresponding to the concentration recovery region is not limited to the operation caution region, and may be set as the operation continuation threshold value of the alkaline water electrolysis apparatus 1 in step S108 or the operation start threshold value in step S109. With this setting, although the range of power supply for operating the alkaline water electrolysis apparatus 1 is narrowed, it is possible to keep the concentration of hydrogen in oxygen generated on the anode 4A side low.
  • the predetermined value used for the determination in step S102 is a value that allows 30% of the rated current of the alkaline water electrolysis device 1 to flow to the alkaline water electrolysis device 1.
  • the power value is not limited to this, and may be a power value that allows a current of 40% to flow to the alkaline water electrolysis apparatus 1.
  • the relationship between the current density and the hydrogen concentration illustrated in FIG. 6 changes depending on conditions such as the concentration of the electrolytic solution, the capacity of the electrolytic device, and the number of cells in the electrolytic cell. For this reason, the value of the current density that distinguishes the operation region corresponding to the hydrogen concentration described above is not limited to the numerical value described above. Further, the hydrogen concentration in oxygen corresponding to the current is obtained by plotting an actually measured value measured in a steady state. Therefore, when the current changes, the hydrogen concentration in oxygen does not always match the hydrogen concentration corresponding to the current density shown in FIG. 6, and a time lag may occur in following.
  • the AC / DC converters 6A, 6B and the PLC 7, which are examples of the control means in the embodiment of the present invention, are configured such that the water electrolysis device connected to the power supply is the same as the alkaline water electrolysis device 1 which is an example of the first water electrolysis device. And the polymer water electrolysis device 2 which is an example of the second water electrolysis device.
  • the electrolysis apparatus connected to the power supply is raised. It is possible to quickly switch to the molecular water electrolysis device 2. Therefore, the relative increase in the stray current in the alkaline water electrolysis device 1 is quickly suppressed, and as a result, the mixing of hydrogen with oxygen generated from the anode 3A of the alkaline water electrolysis device 1 is quickly suppressed. You. Similarly, in the cathode 3B, the mixing of oxygen with the generated hydrogen is quickly suppressed.
  • the water electrolysis system 100 formed from the AC / DC converters 6A and 6B and the PLC 7 does not have a complicated structure. That is, an increase in the concentration of hydrogen contained in oxygen generated at the anode 3A and an increase in the concentration of oxygen contained in hydrogen generated at the cathode 3B are easily suppressed.
  • the water electrolysis system 100 as described above determines whether or not the concentration of hydrogen contained in oxygen generated in the alkaline water electrolysis device 1 is equal to or higher than a predetermined concentration value by performing the determination process in step S104. The determination is made that the supply of the current to the alkaline water electrolysis apparatus 1 is stopped by performing the processing of step S105 when the concentration is equal to or higher than the predetermined concentration value. That is, in the water electrolysis system 100 as described above, the AC / DC converters 6A and 6B and the PLC 7 distribute the power supplied from the power supply to the alkaline water electrolysis apparatus 1 and the polymer water electrolysis apparatus 2 by using a power supply.
  • Such a water electrolysis system 100 also adjusts the power distributed to the alkaline water electrolysis device 1 by determining the concentration of hydrogen contained in oxygen, and converts hydrogen from the anode 3A of the alkaline water electrolysis device 1 to hydrogen. Generation of oxygen containing much can be suppressed.
  • ⁇ Operation example 2> In the above-described operation example 1, when the hydrogen concentration on the anode 4A side is high, the predetermined value is set and controlled in step S102 for the purpose of reducing the hydrogen concentration in the oxygen on the anode 4A side. Had gone.
  • the operation continuation threshold value in step S108 and the operation start threshold value in step S109 are changed according to the hydrogen concentration on the anode 4A side. Has become.
  • step S102 is omitted, and instead, a flow is added in which the operation continuation threshold value in step S108 and the operation start threshold value in step S109 are changed according to the hydrogen concentration.
  • the other configurations have many points in common with the operation example 1, and a description of the common configurations will be omitted.
  • the operation continuation threshold value in step S108 and the operation start threshold value in step S109 are set to an electric power value corresponding to 10% of the rated current of the alkaline water electrolysis device 1. Then, the predetermined value of the concentration of hydrogen in oxygen used at the time of executing the processing of step S104 is set to 11000 ppm or the like.
  • the operation continuation threshold value of step S108 and the operation continuation threshold value of step S109 The operation start threshold is changed for a certain period of time to a value such that sufficient oxygen can be generated and the power can be reduced such that the hydrogen concentration on the anode 3A side can be reduced by continuing the operation.
  • the power is set to 30% of the rated current of the alkaline water electrolysis device 1. (Hereinafter, referred to as density abnormal mode). This period may be determined based on the hydrogen concentration on the anode 4A side, or may be a predetermined time. For this reason, during the abnormal concentration mode, the alkaline water electrolysis apparatus 1 is operated only when electric power capable of diluting high-concentration hydrogen existing in oxygen is supplied. Then, after a certain period of time, the abnormal density mode ends.
  • FIG. 8 shows a temporal change in the measured value of the hydrogen concentration in oxygen generated from the alkaline water electrolysis apparatus 1 when the water electrolysis system 100 operates as described above.
  • a temporal change of a current value supplied from the power supply to the water electrolysis system 100 is also shown.
  • the current value is expressed as a ratio to the rated current of the alkaline water electrolysis device 1. As shown in FIG. 8, it is recognized that the current supplied from the power supply is fluctuating.
  • the operation continuation threshold and the operation start threshold are set to electric power values corresponding to 10% of the rated current. For this reason, when the electric power supplied from the power supply is fluctuating, the alkaline water electrolysis apparatus 1 is allowed to be operated even in a low load operation caution area. At this time, it can be seen from FIG. 8 that the concentration of hydrogen contained in oxygen does not increase rapidly and the operation at a low load is continued for a while.
  • the concentration of hydrogen generated from the alkaline water electrolysis apparatus 1 becomes 11000 ppm about 10 minutes after the start of operation. Then, since the hydrogen concentration has reached 11000 ppm, it is determined that the hydrogen concentration has reached the predetermined value, and the operation of the water electrolysis system 100 is temporarily stopped. Thereafter, the operation mode has been changed to the abnormal concentration mode.
  • the threshold value is raised to a power value corresponding to 30% of the rated current of the alkaline water electrolysis device 1, so that the alkaline water electrolysis device 1 has an electric power capable of reducing the hydrogen concentration on the anode 4A side. It will work when supplied. Then, in the water electrolysis system 100, after the elapse of the predetermined period, the concentration abnormal mode ends. Needless to say, in the abnormal concentration mode, when the power capable of lowering the hydrogen concentration on the anode 4A side is not supplied, the operation of the alkaline water electrolysis apparatus 1 is stopped.
  • the operation continuation threshold and the operation start threshold are set to values higher than those in the first operation example.
  • the power value is set to a power value corresponding to a current value of 40% of the rated current of the alkaline water electrolysis device 1 corresponding to the hydrogen concentration in the concentration recovery region.
  • the power supplied from the power supply is made larger than the power value corresponding to a current value of 40% of the rated current of the alkaline water electrolysis device 1 by performing the processing of steps S108 and S109. It is determined whether it is larger.
  • step S105 When the power supplied from the power supply is equal to or less than the power value corresponding to a current value of 40% of the rated current of the alkaline water electrolysis apparatus 1, the processing in step S105 is executed to execute the processing in step S105. The supply of current to 1 is stopped. Then, a current is supplied to the polymer-type water electrolysis device 2 by performing the process of step S112. As described above, since the alkaline water electrolysis apparatus 1 is operated with the power corresponding to the hydrogen concentration in the concentration recovery region, it is possible to avoid a state where the hydrogen concentration in the oxygen on the anode 3A side is high.
  • the operation continuation threshold and the operation start threshold may be set to electric power corresponding to the hydrogen concentration in oxygen in the operation caution area.
  • the power is set to a value corresponding to 20% of the rated current.
  • the water electrolysis system 100 can operate as in the three operation examples described above. Further, in the above embodiment, as an example of the “first water electrolysis device” of the present invention, an alkaline water electrolysis having an electrolyte of a potassium hydroxide aqueous solution or a sodium hydroxide aqueous solution having a weight concentration of about 30%.
  • the device 1 has been exemplified.
  • the polymer water electrolysis device 2 in which the cathode 4B is provided with the electrolyte 5 interposed therebetween has been illustrated.
  • the combination of the first water electrolysis device and the second water electrolysis device is not limited to the example of the above embodiment.
  • both the first water electrolysis device and the second water electrolysis device may be water electrolysis devices having an electrolyte solution containing an aqueous alkaline solution.
  • the alkaline aqueous solution of the second water electrolyzer is diluted in weight concentration of the alkali compound so as to be an aqueous solution having lower conductivity than the alkaline aqueous solution of the first water electrolyzer.
  • the stray current generated in the alkaline aqueous solution of the second water electrolysis device is smaller than the stray current generated in the alkaline aqueous solution of the first water electrolysis device because the alkali concentration of the aqueous solution is low. Therefore, even in such a water electrolysis system, when the electric power supplied from the power supply is distributed to the first water electrolysis device and the second water electrolysis device in the same manner as in the above-described embodiment, this occurs.
  • pure water is exemplified as an example of the second electrolytic solution of the second water electrolyzer, but the second electrolytic solution is different from the first electrolytic solution of the first water electrolyzer.
  • any electrolytic solution having low conductivity may be used.

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Abstract

Provided is a water electrolysis system provided with: a first water electrolysis device which has first electrolysis electrodes immersed in a first electrolyte and which generates hydrogen and oxygen by applying a voltage between the first electrolysis electrodes; a second water electrolysis device which has second electrolysis electrodes immersed in a second electrolyte having a conductivity lower than the first electrolyte and which generates hydrogen by applying a voltage between the second electrolysis electrodes; and a control means for controlling the power to be supplied to the first water electrolysis device and the second water electrolysis device according to the power supplied from the power supply provided outside the system, such that the elevation of the hydrogen concentration in oxygen generated from the first water electrolysis device is suppressed.

Description

水電解システム及び水電解方法Water electrolysis system and water electrolysis method
　本発明は、水電解システム及び水電解方法に関する。 The present invention relates to a water electrolysis system and a water electrolysis method.
　水電解装置は、水を電気分解することによって水素を製造することができる。製造された水素は、例えば燃料電池等に使用される。従来の水電解装置として、例えば特許文献１に開示されている、アルカリ水を含む電解液を電気分解することによって水素を発生させる水電解装置（以下、アルカリ型水電解装置という）が挙げられる。また、陽極近傍で水を電気分解してプロトンを発生させ、得られたプロトンを、高分子を含む電解質を介して陰極近傍へ移動させ、陰極近傍においてプロトンが電子を受け取ることによって水素を発生させる水電解装置（以下、高分子型水電解装置という）も挙げられる。また、非特許文献１では、風力発電設備と高分子型水電解装置とを組み合わせたシステムの一例が開示されている。 A water electrolysis device can produce hydrogen by electrolyzing water. The produced hydrogen is used for, for example, a fuel cell. As a conventional water electrolysis device, for example, a water electrolysis device (hereinafter, referred to as an alkaline water electrolysis device) disclosed in Patent Literature 1 that generates hydrogen by electrolyzing an electrolytic solution containing alkaline water is given. In addition, water is electrolyzed in the vicinity of the anode to generate protons, and the obtained protons are moved to the vicinity of the cathode through an electrolyte containing a polymer, and the protons receive electrons in the vicinity of the cathode to generate hydrogen. A water electrolysis device (hereinafter, referred to as a polymer type water electrolysis device) is also included. Non-Patent Document 1 discloses an example of a system combining a wind power generation facility and a polymer water electrolysis device.
特開２０１７－１７９５５７号公報JP 2017-179557 A
　アルカリ型水電解装置は、高分子型水電解装置と比較して、装置の構造が単純であることから大型化しやすく、単位水素製造量当たりの初期コストを低減することができる利点を有する。アルカリ型水電解装置は、その電解液が電気分解される場合、電解電極の陽極近傍において酸素が発生し、陰極近傍において水素が発生する。 (4) The alkaline water electrolysis apparatus has the advantage that it can be easily increased in size due to its simple structure, and can reduce the initial cost per unit hydrogen production amount, as compared with the polymer water electrolysis apparatus. In the alkaline water electrolysis apparatus, when the electrolytic solution is electrolyzed, oxygen is generated near the anode of the electrolytic electrode, and hydrogen is generated near the cathode.
　しかしながら、アルカリ型水電解装置においては、電解液が導電性を持つため電解槽内の電解液および金属部材を通じて陽極の一部分が陰極となり、本来酸素が生じるべき場所で水素が発生することで酸素と水素の混合ガスが生じる。また、陰極でも同様に部分的に酸素が生じる。これは、迷走電流として知られ、アルカリ型水電解装置特有の現象である。特に、陽極側において発生した水素が酸素中の水素濃度４％を超える場合には、水素と酸素の反応は連鎖反応となる虞がある。 However, in an alkaline water electrolysis apparatus, a part of the anode becomes a cathode through the electrolytic solution and the metal member in the electrolytic cell because the electrolytic solution has conductivity, and hydrogen is generated at a place where oxygen should originally be generated, so that oxygen and oxygen are generated. A mixed gas of hydrogen is produced. Similarly, oxygen is also partially generated at the cathode. This is known as stray current and is a phenomenon unique to an alkaline water electrolysis device. In particular, when hydrogen generated on the anode side exceeds a hydrogen concentration of 4% in oxygen, the reaction between hydrogen and oxygen may be a chain reaction.
　ここで、水電解装置に供給される電力には、例えば太陽光や風力といった自然エネルギーを利用して発電された電力が使用されることが考えられる。しかしながら、これら自然エネルギーを利用した発電は、その発電量が概して一定でなく自然現象の影響を受けて変動することとなる。そして、アルカリ型水電解装置は、電気分解に使用される電力が小さい場合、迷走電流が相対的に増加することによって陽極において発生する酸素に含まれる水素の濃度は高くなる。よって、生成される酸素と水素との反応性が高まり、水電解装置の運用に影響が及ぶ虞が考えられる。つまり、水電解装置を運用するためには、発生する酸素に含まれる水素の濃度の上昇を抑制する技術を開発することが望まれる。 Here, as the electric power supplied to the water electrolysis device, it is conceivable that electric power generated using natural energy such as sunlight or wind power is used. However, in the power generation using these natural energies, the power generation amount is generally not constant and fluctuates under the influence of natural phenomena. In the alkaline water electrolyzer, when the electric power used for electrolysis is small, the concentration of hydrogen contained in oxygen generated at the anode increases due to the relative increase in stray current. Therefore, the reactivity between the generated oxygen and hydrogen is increased, which may affect the operation of the water electrolysis apparatus. That is, in order to operate the water electrolysis apparatus, it is desired to develop a technique for suppressing an increase in the concentration of hydrogen contained in the generated oxygen.
　特許文献１に開示の技術では、アルカリ型水電解装置において生成される水素ガスの純度を維持するために、系外から供給される電気を整流する整流器、電解セル、そして整流器と電解セルとの間にスイッチ回路が設けられている。そして、供給電力に合わせてスイッチ回路を制御することにより、整流器と接続する電解セルの数を調整する技術が開示されている。また、整流器には、電解セルへ印加される電流を蓄える蓄電池が設けられている。当該技術によれば、電源から供給される電力が変動した場合であっても、アルカリ型水電解装置へ供給する電力を一定に保つことができ、水電解装置から生成される水素ガスの純度を保つことができる。このような特許文献１に開示の技術を転用すれば、陽極において発生する酸素中の水素濃度の上昇を抑制することが可能と考えられる。しかしながら、特許文献１に開示の技術では、水電解装置の構造が複雑となる。また、スイッチ回路が短期間に消耗する虞も考えられる。 According to the technology disclosed in Patent Document 1, in order to maintain the purity of hydrogen gas generated in an alkaline water electrolysis apparatus, a rectifier for rectifying electricity supplied from outside the system, an electrolytic cell, and a rectifier and an electrolytic cell. A switch circuit is provided between them. Then, a technique is disclosed in which the number of electrolytic cells connected to the rectifier is adjusted by controlling the switch circuit in accordance with the supplied power. Further, the rectifier is provided with a storage battery for storing a current applied to the electrolytic cell. According to this technology, even when the power supplied from the power supply fluctuates, the power supplied to the alkaline water electrolysis device can be kept constant, and the purity of the hydrogen gas generated from the water electrolysis device can be reduced. Can be kept. By diverting the technique disclosed in Patent Document 1, it is considered that an increase in the concentration of hydrogen in oxygen generated at the anode can be suppressed. However, in the technology disclosed in Patent Document 1, the structure of the water electrolysis device is complicated. In addition, the switch circuit may be consumed in a short time.
　そこで、本願は、電源から水電解装置へ供給される電力が変動した場合であっても、水電解装置から発生する酸素中の水素濃度の上昇を簡易に抑制し、水電解装置の運用に影響を及ぼすことを抑制する技術を提供することを課題とする。 Therefore, the present application easily suppresses an increase in the concentration of hydrogen in oxygen generated from the water electrolysis device even when the power supplied from the power supply to the water electrolysis device fluctuates, and affects the operation of the water electrolysis device. It is an object of the present invention to provide a technology for suppressing the effect of
　上記課題を解決するため、本発明は、第一の水電解装置と、第二の水電解装置とを備え、電源から供給される電力を第一の水電解装置と第二の水電解装置へ配分する水電解システムとすることとした。 In order to solve the above problems, the present invention includes a first water electrolysis device and a second water electrolysis device, and supplies power supplied from a power supply to the first water electrolysis device and the second water electrolysis device. The water electrolysis system to be distributed was decided.
　詳細には、本発明は、第一の電解液に浸される第一の電解電極を有し、第一の電解電極間に電圧を印加することによって水素と酸素を発生させる第一の水電解装置と、第一の電解液よりも導電性の低い第二の電解液に浸される第二の電解電極を有し、第二の電解電極間に電圧を印加することによって水素を発生させる第二の水電解装置と、第一の水電解装置から発生する酸素中の水素濃度の上昇を抑制するように、系外の電源から供給される電力に応じて、第一の水電解装置及び第二の水電解装置への供給電力を制御する制御手段と、を備える、水電解システムである。 In detail, the present invention has a first electrolytic cell having a first electrolytic electrode immersed in a first electrolytic solution and generating hydrogen and oxygen by applying a voltage between the first electrolytic electrodes. The apparatus has a second electrolytic electrode immersed in a second electrolytic solution having a lower conductivity than the first electrolytic solution, and generates hydrogen by applying a voltage between the second electrolytic electrodes. The second water electrolysis device and the first water electrolysis device and the second water electrolysis device according to the power supplied from the power supply outside the system so as to suppress an increase in the hydrogen concentration in oxygen generated from the first water electrolysis device. And a control means for controlling power supplied to the second water electrolysis device.
　ここで、系外の電源とは、水電解システムの外部に存在する電源のことをいう。 Here, the external power supply means a power supply existing outside the water electrolysis system.
　第一の水電解装置では、第一の電解電極の陽極近傍で酸素が発生し、陰極近傍で水素が発生する。また、第一の電解液は、第二の電解液よりも導電性が高いため、第一の水電解装置は、迷走電流を生じさせやすい。そして、第一の水電解装置へ配分される電力が小さい場合には、迷走電流が相対的に増加することによって陽極近傍で水素が、陰極近傍で酸素が発生する虞がある。すなわち、陽極近傍で発生する酸素に含まれる水素濃度は、上昇する虞がある。 で は In the first water electrolysis device, oxygen is generated near the anode of the first electrolysis electrode, and hydrogen is generated near the cathode. Further, since the first electrolytic solution has higher conductivity than the second electrolytic solution, the first water electrolysis device easily generates a stray current. When the power distributed to the first water electrolysis device is small, there is a possibility that hydrogen near the anode and oxygen near the cathode may be generated due to a relatively increased stray current. That is, the concentration of hydrogen contained in oxygen generated near the anode may increase.
　しかしながら、このような水電解システムであれば、第一の水電解装置から発生する酸素中の水素濃度の上昇を抑制するように、系外の電源から供給される電力に応じて、第一の水電解装置への供給電力は好適に制御可能である。よって、水電解システムの運用に影響が及ぶことは抑制される。また、第一の水電解装置の陰極近傍で発生する水素に含まれる酸素濃度の上昇も抑制することができる。 However, with such a water electrolysis system, the first water electrolysis device is controlled according to the power supplied from a power supply outside the system so as to suppress the increase in the hydrogen concentration in oxygen generated from the first water electrolysis device. The power supplied to the water electrolysis device can be suitably controlled. Therefore, it is suppressed that the operation of the water electrolysis system is affected. In addition, an increase in the concentration of oxygen contained in hydrogen generated near the cathode of the first water electrolysis device can be suppressed.
　また、このような水電解システムは、第一の水電解装置あるいは第二の水電解装置の何れか一方の水電解装置への電力の供給を停止した場合であっても、他方の水電解装置から水素の発生を継続することができる。よって、可用性の高いシステムである。 Further, such a water electrolysis system, even when the supply of power to one of the first water electrolysis device or the second water electrolysis device is stopped, the other water electrolysis device , The generation of hydrogen can be continued. Therefore, it is a highly available system.
　また、第一の水電解装置は、第一の電解液がアルカリ水溶液を含むアルカリ型水電解装置であって、制御手段は、電源から供給される電力が、所定の閾値以下である場合に、電力を第一の水電解装置へ供給することを停止してもよい。 Further, the first water electrolysis device is an alkaline water electrolysis device in which the first electrolytic solution contains an alkaline aqueous solution, and the control means, when the power supplied from the power supply is equal to or less than a predetermined threshold, The supply of electric power to the first water electrolysis device may be stopped.
　また、所定の閾値は、第一の水電解装置から発生する酸素中の水素濃度を急激に上昇させる電力であってもよい。 The predetermined threshold value may be electric power for rapidly increasing the concentration of hydrogen in oxygen generated from the first water electrolysis device.
　また、所定の閾値は、第一の水電解装置の運転を回避する濃度の水素を含む酸素を発生させる電力であってもよい。 The predetermined threshold may be electric power for generating oxygen containing hydrogen at a concentration that avoids operation of the first water electrolysis device.
　また、所定の閾値は、第一の水電解装置の定格電流の４０％の電流を第一の水電解装置へ流すことのできる値であってもよい。 The predetermined threshold value may be a value that allows a current of 40% of the rated current of the first water electrolysis device to flow to the first water electrolysis device.
　また、第二の水電解装置は、高分子を含む電解質を含み、第一の電解液よりも導電性の低い第二の電解液に浸される第二の電解電極が、電解質を挟んで設けられ、第二の電解電極間に電圧を印加することによって水素を発生させる、高分子型水電解装置であってもよい。 In addition, the second water electrolysis device includes an electrolyte containing a polymer, and a second electrolytic electrode immersed in a second electrolyte having lower conductivity than the first electrolyte is provided with the electrolyte interposed therebetween. Alternatively, a polymer-type water electrolysis device that generates hydrogen by applying a voltage between the second electrolysis electrodes may be used.
　また、制御手段は、第一の水電解装置および第二の水電解装置に供給する電力を、第一の水電解装置から発生する酸素に含まれる水素の濃度に応じて制御してもよい。 The control means may control electric power supplied to the first water electrolysis device and the second water electrolysis device according to the concentration of hydrogen contained in oxygen generated from the first water electrolysis device.
　また、制御手段は、電源と接続する水電解装置を第一の水電解装置と第二の水電解装置との間で切り替える切り替え手段を備えてもよい。 The control unit may include a switching unit that switches a water electrolysis device connected to a power source between the first water electrolysis device and the second water electrolysis device.
　また、制御手段は、第一の水電解装置への電力の供給が停止した状態において、第一の水電解装置から発生する酸素に含まれる水素の濃度が第一の濃度以下である場合に、電源から供給される電力が第一の運転開始閾値よりも大きくなると、第一の水電解装置に対して電力の供給を再開し、第一の水電解装置から発生する酸素に含まれる水素の濃度が第一の濃度より大きい場合には、電源から供給される電力が第一の運転開始閾値よりも大きくなっても、第一の水電解装置に対して電力の供給を再開せず、電源から供給される電力が第一の運転開始閾値よりも大きな第二の運転開始閾値よりも大きくなると、第一の水電解装置に対して電力の供給を再開してもよい。 Further, the control means, in a state where power supply to the first water electrolysis device is stopped, when the concentration of hydrogen contained in oxygen generated from the first water electrolysis device is equal to or less than the first concentration, When the power supplied from the power supply becomes larger than the first operation start threshold, the supply of power to the first water electrolysis device is restarted, and the concentration of hydrogen contained in oxygen generated from the first water electrolysis device is increased. Is greater than the first concentration, even if the power supplied from the power supply is greater than the first operation start threshold, does not restart the supply of power to the first water electrolysis device, When the supplied electric power becomes larger than the second operation start threshold larger than the first operation start threshold, the supply of electric power to the first water electrolysis device may be restarted.
　また、制御手段は、第一の水電解装置から発生する酸素に含まれる水素の濃度に応じて所定の閾値を変更してもよい。 The control means may change the predetermined threshold value according to the concentration of hydrogen contained in oxygen generated from the first water electrolysis device.
　また、本発明は、方法の側面から捉えることもできる。すなわち、例えば、第一の電解液に浸される第一の電解電極を有し、第一の電解電極間に電圧を印加することによって水素と酸素を発生させる第一の水電解装置と、第一の電解液よりも導電性の低い第二の電解液に浸される第二の電解電極を有し、第二の電解電極間に電圧を印加することによって水素を発生させる第二の水電解装置と、への系外の電源から供給される電力の配分を、系外の電源から供給される電力に応じて、第一の水電解装置から発生する酸素中の水素濃度の上昇を抑制するように制御する制御ステップを備える、水電解方法であってもよい。 本 The present invention can also be grasped from the aspect of a method. That is, for example, a first water electrolysis device that has a first electrolytic electrode immersed in a first electrolytic solution and generates hydrogen and oxygen by applying a voltage between the first electrolytic electrodes, A second water electrolysis having a second electrolytic electrode immersed in a second electrolytic solution having lower conductivity than the one electrolytic solution, and generating hydrogen by applying a voltage between the second electrolytic electrodes. Apparatus, and the distribution of power supplied from the external power supply to the, according to the power supplied from the external power supply, to suppress the increase in the hydrogen concentration in oxygen generated from the first water electrolysis apparatus Water electrolysis method, which includes a control step for performing control as described above.
　上記の水電解システムは、電源から水電解装置へ供給される電力が変動した場合であっても、水電解装置から発生する酸素中の水素濃度の上昇を簡易に抑制し、水電解装置の運用に影響を及ぼすことを抑制する技術を提供する。 The above-described water electrolysis system can easily suppress an increase in the hydrogen concentration in oxygen generated from the water electrolysis device even when the power supplied from the power supply to the water electrolysis device fluctuates, and operate the water electrolysis device. Provide technology that suppresses the influence of
図１は、本発明の実施形態にかかる水電解システムの概要の一例を示している。FIG. 1 shows an example of an outline of a water electrolysis system according to an embodiment of the present invention. 図２は、再生可能エネルギーによる発電電力を売電する発電所において、出力制限などにより売電できない分の電力が水電解システムへ供給される概要の一例を示している。FIG. 2 shows an example of an outline in which, in a power plant that sells power generated by renewable energy, power that cannot be sold due to output limitation or the like is supplied to the water electrolysis system. 図３は、発電設備において発電された電力が系統を介して水電解システムへ供給される一例を示している。FIG. 3 shows an example in which electric power generated in the power generation facility is supplied to the water electrolysis system via a system. 図４は、水電解システムの動作の概要を示すフローチャートの一例を示している。FIG. 4 shows an example of a flowchart showing an outline of the operation of the water electrolysis system. 図５は、風力発電設備において発電された電力の経時変化の一例を示している。FIG. 5 shows an example of a temporal change of the power generated in the wind power generation facility. 図６は、アルカリ型水電解装置の電解電極に印加される電流と酸素中の水素濃度との関係の一例を示している。FIG. 6 shows an example of the relationship between the current applied to the electrolytic electrode of the alkaline water electrolysis device and the concentration of hydrogen in oxygen. 図７は、水電解システムのアルカリ型水電解装置から発生する酸素中の水素濃度と、アルカリ型水電解装置のみを稼働させた場合に発生する酸素中の水素濃度との比較の一例を示している。FIG. 7 shows an example of a comparison between the hydrogen concentration in oxygen generated from the alkaline water electrolysis device of the water electrolysis system and the hydrogen concentration in oxygen generated when only the alkaline water electrolysis device is operated. I have. 図８は、水電解システムのアルカリ型水電解装置から発生する酸素中の水素濃度の計測値の経時変化を示している。FIG. 8 shows a change with time of the measured value of the hydrogen concentration in oxygen generated from the alkaline water electrolysis device of the water electrolysis system.
　以下、本発明の実施形態について説明する。以下に示す実施形態は、本発明の実施形態の一例であり、本発明の技術的範囲を以下の態様に限定するものではない。 Hereinafter, embodiments of the present invention will be described. The embodiment shown below is an example of an embodiment of the present invention, and does not limit the technical scope of the present invention to the following aspects.
　＜装置構成＞
　図１は、本発明の実施形態にかかる水電解システム１００の概要の一例を示している。図１に示されるように水電解システム１００は、アルカリ型水電解装置１と高分子型水電解装置２とを備える。そして、水電解システム１００は、アルカリ型水電解装置１および高分子型水電解装置２を同時に運用するシステムである。アルカリ型水電解装置１は、例えば、濃度が約３０重量％程度の水酸化カリウム水溶液又は水酸化ナトリウム水溶液の電解液を有する水電解装置である。ここで、水酸化カリウム水溶液又は水酸化ナトリウム水溶液は、本発明の「第一の電解液」の一例である。一方で、高分子型水電解装置２は、高分子を含む電解質５を有する水電解装置である。ここで、アルカリ型水電解装置１は、本発明の「第一の水電解装置」の一例である。また、高分子型水電解装置２は、本発明の「第二の水電解装置」の一例である。 <Apparatus configuration>
FIG. 1 shows an example of an outline of a water electrolysis system 100 according to an embodiment of the present invention. As shown in FIG. 1, the water electrolysis system 100 includes an alkaline water electrolysis device 1 and a polymer water electrolysis device 2. The water electrolysis system 100 is a system that simultaneously operates the alkaline water electrolysis device 1 and the polymer water electrolysis device 2. The alkaline water electrolysis device 1 is, for example, a water electrolysis device having an electrolytic solution of a potassium hydroxide aqueous solution or a sodium hydroxide aqueous solution having a concentration of about 30% by weight. Here, the aqueous potassium hydroxide solution or the aqueous sodium hydroxide solution is an example of the “first electrolytic solution” of the present invention. On the other hand, the polymer water electrolysis device 2 is a water electrolysis device having the electrolyte 5 containing a polymer. Here, the alkaline water electrolysis device 1 is an example of the “first water electrolysis device” of the present invention. The polymer water electrolysis device 2 is an example of the “second water electrolysis device” of the present invention.
　また、水電解システム１００は、図示しないが、アルカリ型水電解装置１から発生する水素中の酸素の濃度を計測する酸素濃度計、及び酸素中の水素の濃度を計測する水素濃度計を備える。また、水電解システム１００は、図示しないが、高分子型水電解装置２から発生する水素中の酸素の濃度を計測する酸素濃度計、及び酸素中の水素の濃度を計測する水素濃度計も備える。 水 Although not shown, the water electrolysis system 100 includes an oxygen concentration meter that measures the concentration of oxygen in hydrogen generated from the alkaline water electrolysis device 1 and a hydrogen concentration meter that measures the concentration of hydrogen in oxygen. Although not shown, the water electrolysis system 100 also includes an oxygen concentration meter that measures the concentration of oxygen in hydrogen generated from the polymer water electrolysis device 2 and a hydrogen concentration meter that measures the concentration of hydrogen in oxygen. .
　また、水電解システム１００は、太陽光発電設備や風力発電設備等の電源から供給される電流が交流電流である場合に、交流電流を直流電流へ変換するＡＣ／ＤＣコンバータ６Ａ、６Ｂを備える。ＡＣ／ＤＣコンバータ６Ａ、６Ｂは、交流電流を直流電流へ整流する機能と直流電流を指令された値に制御する機能を備える。また、アルカリ型水電解装置１は、陽極３Ａ、陰極３Ｂを含む電解電極を備える。ここで、陽極３Ａ及び陰極３Ｂは、本発明の「第一の電解電極」の一例である。そして、ＡＣ／ＤＣコンバータ６Ａによって変換された直流電流は、アルカリ型水電解装置１の陽極３Ａ及び陰極３Ｂへ供給される。一方、高分子型水電解装置２は、電解質５を挟んで設けられる陽極４Ａ、陰極４Ｂを含む電解電極を備える。ここで、陽極４Ａ及び陰極４Ｂは、本発明の「第二の電解電極」の一例である。陽極４Ａ及び陰極４Ｂの表面は、純水に浸される。ここで、純水は、本発明の「第二の電解液」の一例であって、アルカリ型水電解装置１の第一の電解液よりも導電性は低い。そして、ＡＣ／ＤＣコンバータ６Ｂによって変換された直流電流は、高分子型水電解装置２の陽極４Ａ及び陰極４Ｂへ供給される。 The water electrolysis system 100 also includes AC / DC converters 6A and 6B that convert an AC current into a DC current when the current supplied from a power source such as a solar power generation facility or a wind power generation facility is an AC current. The AC / DC converters 6A and 6B have a function of rectifying an alternating current to a direct current and a function of controlling the direct current to a commanded value. Further, the alkaline water electrolysis apparatus 1 includes an electrolytic electrode including an anode 3A and a cathode 3B. Here, the anode 3A and the cathode 3B are examples of the “first electrolytic electrode” of the present invention. The direct current converted by the AC / DC converter 6A is supplied to the anode 3A and the cathode 3B of the alkaline water electrolysis device 1. On the other hand, the polymer type water electrolysis device 2 includes an electrolytic electrode including an anode 4A and a cathode 4B provided with the electrolyte 5 interposed therebetween. Here, the anode 4A and the cathode 4B are an example of the “second electrolytic electrode” of the present invention. The surfaces of the anode 4A and the cathode 4B are immersed in pure water. Here, pure water is an example of the “second electrolytic solution” of the present invention, and has lower conductivity than the first electrolytic solution of the alkaline water electrolysis device 1. The DC current converted by the AC / DC converter 6B is supplied to the anode 4A and the cathode 4B of the polymer water electrolysis device 2.
　また、水電解システム１００は、電源から水電解システム１００へ供給される電力に応じてＡＣ／ＤＣコンバータ６Ａ、６Ｂを制御し、電源から各水電解装置へ供給する電力の配分を調整するＰＬＣ（Ｐｒｏｇｒａｍｍａｂｌｅ　Ｌｏｇｉｃ　Ｃｏｎｔｒｏｌｌｅｒ）７を備える。ＰＬＣ７がＡＣ／ＤＣコンバータ６Ａ、６Ｂを制御することにより、電源と接続する水電解装置をアルカリ型水電解装置１と高分子型水電解装置２との間で切り替えることが可能となる。ここでＡＣ／ＤＣコンバータ６Ａ、６Ｂ及びＰＬＣ７は、本発明の「制御手段」及び「切り替え手段」の一例である。また、ＰＬＣ７は、酸素濃度計又は水素濃度計の計測値に応じてＡＣ／ＤＣコンバータ６Ａ、６Ｂを制御し、電源から供給される電力の各水電解装置への配分を調整することもできる。 In addition, the water electrolysis system 100 controls the AC / DC converters 6A and 6B in accordance with the power supplied from the power supply to the water electrolysis system 100, and adjusts the distribution of power supplied from the power supply to each water electrolysis device (PLC). (Programmable Logic Controller) 7. When the PLC 7 controls the AC / DC converters 6A and 6B, the water electrolysis device connected to the power source can be switched between the alkaline water electrolysis device 1 and the polymer water electrolysis device 2. Here, the AC / DC converters 6A and 6B and the PLC 7 are examples of the "control means" and the "switching means" of the present invention. Further, the PLC 7 can control the AC / DC converters 6A and 6B according to the measurement values of the oxygen concentration meter or the hydrogen concentration meter, and adjust the distribution of the power supplied from the power supply to each water electrolysis device.
　また、水電解システム１００は、アルカリ型水電解装置１や高分子型水電解装置２において発生した水素を貯蔵する水素タンク８を備える。水素タンク８に貯蔵された水素は、例えば燃料電池などに利用される。また、水電解システム１００は、アルカリ型水電解装置１又は高分子型水電解装置２から発生した酸素を大気中に放出させるが、貯蔵して利用してもよいことは言うまでもない。 The water electrolysis system 100 also includes a hydrogen tank 8 for storing hydrogen generated in the alkaline water electrolysis device 1 and the polymer water electrolysis device 2. The hydrogen stored in the hydrogen tank 8 is used for, for example, a fuel cell. Further, the water electrolysis system 100 releases oxygen generated from the alkaline water electrolysis device 1 or the polymer water electrolysis device 2 into the atmosphere, but it goes without saying that oxygen may be stored and used.
　アルカリ型水電解装置１においては、陽極３Ａと陰極３Ｂとの間に電圧が印加されることにより、陰極３Ｂの近傍では、電解液から水素分子と水酸化物イオンが生成される。一方、陽極３Ａの近傍では、電解液中に含まれる水酸化物イオンから水分子と酸素分子が生成される。 In the alkaline water electrolysis apparatus 1, when a voltage is applied between the anode 3A and the cathode 3B, hydrogen molecules and hydroxide ions are generated from the electrolyte near the cathode 3B. On the other hand, near the anode 3A, water molecules and oxygen molecules are generated from hydroxide ions contained in the electrolytic solution.
　しかしながら、アルカリ型水電解装置１においては、電解液が高い導電性を持つため電解槽内の電解液および金属部材を通じて陽極３Ａの一部分が陰極となり、本来酸素が生じるべき場所で水素が発生することで酸素に水素が混合する。また、陰極３Ｂでも同様に部分的に酸素が生じ、発生する水素に酸素が混合する。これは、迷走電流として知られ、アルカリ型水電解装置特有の現象である。 However, in the alkaline water electrolysis apparatus 1, since the electrolytic solution has high conductivity, a part of the anode 3A becomes a cathode through the electrolytic solution and the metal member in the electrolytic cell, and hydrogen is generated in a place where oxygen should be generated. The hydrogen mixes with the oxygen at. Similarly, oxygen is also partially generated in the cathode 3B, and oxygen is mixed with the generated hydrogen. This is known as stray current and is a phenomenon unique to an alkaline water electrolysis device.
　ところで、アルカリ型水電解装置１から発生する水素と酸素は、下記の式（１）から式（３）のように化学反応する場合がある。
Ｈ＋Ｏ２→ＯＨ＋Ｏ・・・（１）
Ｏ＋Ｈ２→ＯＨ＋Ｈ・・・（２）
ＯＨ＋Ｈ２→Ｈ２Ｏ＋Ｈ・・・（３） By the way, hydrogen and oxygen generated from the alkaline water electrolysis apparatus 1 may undergo a chemical reaction as in the following equations (1) to (3).
H + O 2 → OH + O (1)
O + H 2 → OH + H (2)
OH + H 2 → H 2 O + H (3)
　そして、例えば酸素に含まれる水素濃度が所定値よりも高い場合、式（１）から式（３）に示されるように、Ｈラジカル、Ｏラジカル、そしてＯＨラジカルといった活性種が多く生成されることとなる。よって、式（１）から式（３）の化学反応は連鎖反応となり、水素と酸素の反応が急激に進行することとなる。 For example, when the concentration of hydrogen contained in oxygen is higher than a predetermined value, active species such as H radicals, O radicals, and OH radicals are generated as shown in Formulas (1) to (3). It becomes. Therefore, the chemical reaction of the formulas (1) to (3) becomes a chain reaction, and the reaction between hydrogen and oxygen proceeds rapidly.
　ここで、アルカリ型水電解装置１へ供給される電力が小さい場合には、迷走電流が相対的に増加することによって、陽極３Ａにおいて発生する酸素に含まれる水素の濃度が上昇する。特に、陽極３Ａ側で発生した水素が酸素中の水素濃度４％を超える場合には、上述のように水素と酸素の反応は連鎖反応となる虞がある。このため、アルカリ型水電解装置１を使用して水素を生成する場合、上記の水素と酸素の化学反応が連鎖反応とならないように、アルカリ型水電解装置１へ供給する電力を調整する必要がある。なお、通常このような水素と酸素の化学反応が連鎖反応となる虞がある水素濃度の領域ではシステムや装置の運転が禁止されており、本実施形態においても、運転禁止領域として扱う。 Here, when the electric power supplied to the alkaline water electrolysis device 1 is small, the concentration of hydrogen contained in oxygen generated at the anode 3A increases due to the relative increase of the stray current. In particular, when the hydrogen generated on the anode 3A side exceeds a hydrogen concentration of 4% in oxygen, the reaction between hydrogen and oxygen may be a chain reaction as described above. Therefore, when hydrogen is generated using the alkaline water electrolysis apparatus 1, it is necessary to adjust the power supplied to the alkaline water electrolysis apparatus 1 so that the above-described chemical reaction between hydrogen and oxygen does not form a chain reaction. is there. Normally, the operation of the system or the device is prohibited in the region of the hydrogen concentration where the chemical reaction between hydrogen and oxygen may become a chain reaction, and is also treated as the operation prohibited region in the present embodiment.
　また、酸素中の水素濃度が４％よりも低い場合であっても、システムや装置を運転する際には禁止領域に対して余裕をもって運転することが一般的である。本実施例では、酸素中の水素濃度が２％～４％の場合は、このような運転を回避した方がよい領域に相当するものとし、これを運転回避領域として扱う。 In addition, even when the hydrogen concentration in oxygen is lower than 4%, it is general to operate the system or apparatus with a margin with respect to the prohibited area. In this embodiment, when the hydrogen concentration in oxygen is 2% to 4%, it is assumed that such an operation should be avoided, and this region is treated as an operation avoidance region.
　さらに、酸素中の水素濃度が２％よりも低い場合であって、酸素中の水素濃度が急激に上昇するような領域を運転注意領域として扱う。運転注意領域で運転すると、陽極３Ａ側で生成される酸素中の水素濃度が上昇するのと同様に、陰極３Ｂ側で生成される水素中の酸素濃度が後述の定常状態よりも上昇し、生成される水素の純度が低下する。このため、水電解システム１００の運用に影響が及ぶ虞がある。 Furthermore, a region where the hydrogen concentration in oxygen is lower than 2% and in which the hydrogen concentration in oxygen sharply increases is treated as a driving caution region. When the operation is performed in the operation caution region, the oxygen concentration in the hydrogen generated on the cathode 3B side increases as compared with the steady state described later, in the same manner as the hydrogen concentration in the oxygen generated on the anode 3A side increases. The purity of the hydrogen produced is reduced. Therefore, the operation of the water electrolysis system 100 may be affected.
　なお、このような運転禁止領域、運転回避領域、運転注意領域を除いた運転領域が定常状態として用いられる運転領域となる。このような領域での運転時には、アルカリ型水電解装置１には十分な電力が供給されていることになる。また、このような領域で運転すると、酸素中の水素濃度が低い状態の酸素が発生するため、陽極における水素濃度を低下させることができる。このため、このような定常状態を濃度回復領域とみなすこともできる。 運 転 Note that the operation region excluding the operation prohibition region, the operation avoidance region, and the operation caution region is an operation region used as a steady state. During operation in such a region, sufficient power is supplied to the alkaline water electrolysis apparatus 1. When the operation is performed in such a region, oxygen in a state where the hydrogen concentration in oxygen is low is generated, so that the hydrogen concentration at the anode can be reduced. Therefore, such a steady state can be regarded as a concentration recovery region.
　一方、高分子型水電解装置２では、陽極４Ａと陰極４Ｂとの間に、高分子を含む電解質５が設けられている。高分子型水電解装置２では、陽極４Ａと陰極４Ｂとの間に電圧が印加され、陽極４Ａの近傍に純水が流入させられることにより、陽極４Ａの近傍においてプロトン及び酸素分子が生成される。そして生成されたプロトンは、電解質５を介して陰極４Ｂへ移動する。陰極４Ｂの近傍では、プロトンが電子を受け取り、水素分子が生成される。しかしながら、高分子型水電解装置２では、アルカリ型水電解装置１とは異なり、高分子型水電解装置２へ供給される電流が変動した場合であっても、発生する酸素に含まれる水素の濃度は、数百から数千ｐｐｍの範囲に収まり、急激に上昇することはない。これは、高分子型水電解装置が純水を用いており、問題となるような迷走電流の発生が抑制されているためである。 On the other hand, in the polymer-type water electrolysis device 2, the electrolyte 5 containing a polymer is provided between the anode 4A and the cathode 4B. In the polymer water electrolysis device 2, a voltage is applied between the anode 4A and the cathode 4B, and pure water is caused to flow in the vicinity of the anode 4A, so that protons and oxygen molecules are generated in the vicinity of the anode 4A. . The generated protons move to the cathode 4B via the electrolyte 5. In the vicinity of the cathode 4B, protons receive electrons, and hydrogen molecules are generated. However, unlike the alkaline water electrolysis apparatus 1, the polymer water electrolysis apparatus 2 has a function of reducing the amount of hydrogen contained in the generated oxygen even when the current supplied to the polymer water electrolysis apparatus 2 fluctuates. Concentrations fall in the range of hundreds to thousands of ppm and do not rise sharply. This is because the polymer type water electrolysis apparatus uses pure water, and generation of a problematic stray current is suppressed.
　次に水電解システム１００へ供給される電力について説明を行う。図２は、太陽光や風力といった再生可能エネルギーによる発電電力を売電する発電所において、出力制限などにより売電できない分の電力が水電解システム１００へ供給される概要の一例を示している。図２に示されるように、発電所は、太陽光や風力といった再生可能エネルギーを利用して発電を行う発電設備５０を備える。そして、発電設備５０は、水電解システム１００と同敷地内にある。そして、図２の例では、発電設備５０において発電された電力のうち、電力系統へ売電できない余った電力が水電解システム１００へ供給される。 Next, the power supplied to the water electrolysis system 100 will be described. FIG. 2 shows an example of an outline in which in a power plant that sells power generated by renewable energy such as sunlight or wind power, power that cannot be sold due to output limitation or the like is supplied to the water electrolysis system 100. As shown in FIG. 2, the power plant includes a power generation facility 50 that generates power using renewable energy such as sunlight or wind power. And the power generation equipment 50 is in the same site as the water electrolysis system 100. Then, in the example of FIG. 2, of the power generated by the power generation facility 50, surplus power that cannot be sold to the power system is supplied to the water electrolysis system 100.
　また、上記の発電所は、電力系統に接続せず、発電設備５０と同敷地内に工場などの負荷設備を有してもよい。そして、電力系統に接続しない閉じられた環境下において負荷設備で消費しきれず余った電力が水電解システム１００へ供給されてもよい。 The above-mentioned power plant may have a load facility such as a factory in the same premises as the power generation facility 50 without being connected to the power system. Then, in a closed environment that is not connected to the power system, the surplus power that cannot be consumed by the load equipment may be supplied to the water electrolysis system 100.
　また、図２に示される例とは異なり、水電解システム１００は、敷地外の外部電源から電力系統を介して電力を得てもよい。図３は、発電設備５０が、水電解システム１００と同敷地内になく、発電設備５０において発電された電力が系統を介して水電解システム１００へ供給される一例を示している。なお、図２及び図３に示される例では、水電解システム１００に供給する電力の値である電力指令情報は、どこから得てもよい。 Also, unlike the example shown in FIG. 2, the water electrolysis system 100 may obtain electric power from an external power supply outside the premises via a power system. FIG. 3 illustrates an example in which the power generation facility 50 is not located on the same site as the water electrolysis system 100, and the power generated in the power generation facility 50 is supplied to the water electrolysis system 100 via a system. In the examples shown in FIGS. 2 and 3, the power command information, which is the value of the power supplied to the water electrolysis system 100, may be obtained from any location.
　＜動作例１＞
　次に、水電解システム１００の動作の一例を説明する。図４は、水電解システム１００の動作の概要を示すフローチャートの一例を示している。 <Operation example 1>
Next, an example of the operation of the water electrolysis system 100 will be described. FIG. 4 shows an example of a flowchart showing an outline of the operation of the water electrolysis system 100.
　（ステップＳ１０１）
　ステップＳ１０１では、水電解システム１００において電解のための電力供給が開始される。まず、太陽光発電設備や風力発電設備といった電源において発電された電力が水電解システム１００へ供給される。図５は、風力発電設備において発電された電力の経時変化の一例を示している。図５に示されるように、風力による発電は、発電量が一定ではなく変動している。つまり、太陽光発電設備や風力発電設備といった自然エネルギーを利用した発電では、電力は変動し、そのような変動した電力が水電解システム１００へ供給されることとなる。このとき、ＰＬＣ７は、電源から水電解システム１００に供給される電力の値を取得する。 (Step S101)
In step S101, power supply for electrolysis in the water electrolysis system 100 is started. First, power generated by a power source such as a solar power generation facility or a wind power generation facility is supplied to the water electrolysis system 100. FIG. 5 shows an example of a temporal change of the power generated in the wind power generation facility. As shown in FIG. 5, the power generation by wind power is not constant but fluctuates. That is, in power generation using natural energy such as a solar power generation facility or a wind power generation facility, the power fluctuates, and such fluctuated power is supplied to the water electrolysis system 100. At this time, the PLC 7 acquires the value of the power supplied to the water electrolysis system 100 from the power supply.
　（ステップＳ１０２）
　ステップＳ１０２では、ＰＬＣ７は、電源からの供給電力が所定値よりも大きいか否かの判定を行う。ここで、図６は、アルカリ型水電解装置１の電解電極に流入する電流と、当該電解電極の陽極３Ａにおいて発生する酸素に含まれる水素の濃度との関係の一例を示している。なお、アルカリ型水電解装置１の定格電流は０．６Ａｃｍ－２である。また、供給される電流が大きな領域の水素濃度は図示されていないが、図示される部分の右端部とほぼ同じ濃度で一定となっている。 (Step S102)
In step S102, the PLC 7 determines whether the power supplied from the power supply is larger than a predetermined value. Here, FIG. 6 shows an example of the relationship between the current flowing into the electrolytic electrode of the alkaline water electrolysis apparatus 1 and the concentration of hydrogen contained in oxygen generated at the anode 3A of the electrolytic electrode. The rated current of the alkaline water electrolysis device 1 is 0.6 Acm −2 . Although the hydrogen concentration in the region where the supplied current is large is not shown, it is constant at substantially the same concentration as that of the right end of the portion shown.
　図６に示されるように、電解電極に流入する電流の電流密度が０．１８Ａｃｍ－２よりも小さい場合、酸素に含まれる水素の濃度が電流の減少に伴い上昇することが認められる。これは先に説明した運転注意領域に相当する。また、この電流密度０．１８Ａｃｍ－２は、本動作例１のアルカリ型水電解装置１の定格電流の３０％の電流に相当する電力である。 As shown in FIG. 6, when the current density of the current flowing into the electrolytic electrode is smaller than 0.18 Acm −2, it is recognized that the concentration of hydrogen contained in oxygen increases as the current decreases. This corresponds to the driving caution area described above. The current density of 0.18 Acm −2 is power corresponding to a current of 30% of the rated current of the alkaline water electrolysis device 1 of the first operation example.
　逆の見方をすれば、この定格電流の３０％の電流以上の電流をアルカリ型水電解装置１に供給すると酸素中の水素濃度が低い酸素が生成されることとなる。これにより、陽極４Ａ側の水素濃度が高い状態になっていた場合には、酸素で希釈することとなり、相対的に陽極４Ａ側の水素濃度を低下させることができる。すなわちこれは先に説明した濃度回復領域に相当する。そこで、本動作例では、所定値をアルカリ型水電解装置１の定格電流の３０％の電流に相当する電力に設定する。このように濃度回復領域に所定値を設定することで、十分な電力が水電解システム１００に供給される際にアルカリ型水電解装置１を積極的に動作させ、陽極４Ａ側の酸素中の水素濃度を低下させることができる。すなわち、この所定値は、陽極の水素濃度を回復させるための運転開始閾値の役割を果たす。なお、本実施形態において、陽極４Ａ側の酸素中の水素濃度を低下させることを回復と表現することがある。 In other words, if a current equal to or more than 30% of the rated current is supplied to the alkaline water electrolysis apparatus 1, oxygen having a low hydrogen concentration in oxygen will be generated. Thereby, when the hydrogen concentration on the anode 4A side is high, the hydrogen concentration is diluted with oxygen, and the hydrogen concentration on the anode 4A side can be relatively reduced. That is, this corresponds to the density recovery region described above. Therefore, in this operation example, the predetermined value is set to electric power corresponding to 30% of the rated current of the alkaline water electrolysis device 1. By setting the predetermined value in the concentration recovery region in this manner, when sufficient power is supplied to the water electrolysis system 100, the alkaline water electrolysis apparatus 1 is positively operated, and the hydrogen in oxygen on the anode 4A side is hydrogen. The concentration can be reduced. That is, the predetermined value serves as an operation start threshold value for restoring the hydrogen concentration of the anode. In the present embodiment, reducing the concentration of hydrogen in oxygen on the side of the anode 4A may be referred to as recovery.
　（ステップＳ１０３）
　ステップＳ１０３では、ステップＳ１０２において電源からの供給電力が所定値よりも大きいと判定された場合、ＰＬＣ７は、アルカリ型水電解装置１への電力供給を決定する。アルカリ型水電解装置１に電力の供給が決定すると、アルカリ型水電解装置１の内部状態（主に電圧）から、アルカリ型水電解装置１への供給電流が決定する。 (Step S103)
In step S103, if it is determined in step S102 that the power supplied from the power supply is larger than the predetermined value, the PLC 7 determines power supply to the alkaline water electrolysis device 1. When power supply to the alkaline water electrolysis device 1 is determined, the supply current to the alkaline water electrolysis device 1 is determined from the internal state (mainly voltage) of the alkaline water electrolysis device 1.
　（ステップＳ１０４）
　ステップＳ１０４では、ステップＳ１０２において電源からの供給電力が所定値以下であると判定された場合、ＰＬＣ７は、アルカリ型水電解装置１において発生した酸素中の水素濃度が所定濃度値よりも高いか否かの判定を行う。所定濃度値は、適宜定めてよいが、少なくとも発生した酸素と、酸素に含まれる水素との化学反応が連鎖反応とならないような濃度に設定する。例えば、水素と酸素の化学反応が連鎖反応となる濃度である４００００ｐｐｍの半分となる２００００ｐｐｍに設定してもよく、さらに小さい１１０００ｐｐｍに設定してもよい。なお、２００００ｐｐｍ以上４００００ｐｐｍ未満は運転回避領域の水素濃度に対応し、１１０００ｐｐｍ以上２００００ｐｐｍ未満は運転注意領域の水素濃度に対応する。 (Step S104)
In step S104, if it is determined in step S102 that the power supplied from the power supply is equal to or less than the predetermined value, the PLC 7 determines whether the concentration of hydrogen in oxygen generated in the alkaline water electrolysis device 1 is higher than the predetermined concentration value. Is determined. The predetermined concentration value may be appropriately determined, but is set to a concentration at which a chemical reaction between at least generated oxygen and hydrogen contained in oxygen does not form a chain reaction. For example, the concentration may be set to 20,000 ppm, which is half the concentration of 40,000 ppm at which the chemical reaction between hydrogen and oxygen becomes a chain reaction, or may be set to 11,000 ppm, which is smaller. In addition, 20,000 ppm or more and less than 40000 ppm correspond to the hydrogen concentration in the operation avoidance region, and 11,000 ppm or more and less than 20,000 ppm correspond to the hydrogen concentration in the operation caution region.
　（ステップＳ１０５）
　ステップＳ１０５では、ステップＳ１０４において、酸素中の水素濃度が所定濃度値よりも高いと判定された場合、ＰＬＣ７は、アルカリ型水電解装置１へ電流を供給しないことを決定する。 (Step S105)
In step S105, if it is determined in step S104 that the hydrogen concentration in oxygen is higher than the predetermined concentration value, the PLC 7 determines not to supply a current to the alkaline water electrolysis device 1.
　（ステップＳ１０６）
　ステップＳ１０６では、ステップＳ１０４において、酸素中の水素濃度が所定濃度値以下であると判定された場合、ＰＬＣ７は、当該水素濃度が所定濃度値より高いと判定された時間から一定期間経過しているか否かの判定を行う。 (Step S106)
In step S106, if it is determined in step S104 that the hydrogen concentration in oxygen is equal to or lower than the predetermined concentration value, the PLC 7 determines whether a predetermined period has elapsed from the time when the hydrogen concentration was determined to be higher than the predetermined concentration value. It is determined whether or not it is.
　そして、ステップＳ１０６において、水素濃度が所定濃度値よりも高いと判定された時間から一定期間経過していないと判定された場合、ステップＳ１０５の処理が実行され、ＰＬＣ７は、アルカリ型水電解装置１へ電流を供給しないことを決定する。 If it is determined in step S106 that the certain period has not elapsed from the time when the hydrogen concentration is determined to be higher than the predetermined concentration value, the process of step S105 is performed, and the PLC 7 performs the processing in the alkaline water electrolysis apparatus 1. Decide not to supply current to
　（ステップＳ１０７）
　ステップＳ１０７では、ステップＳ１０６において、水素濃度が所定濃度値よりも高いと判定された時間から一定期間経過していると判定された場合、ＰＬＣ７は、アルカリ型水電解装置１が運転されているか否かの判定を行う。 (Step S107)
In step S107, when it is determined in step S106 that the certain period has elapsed from the time in which the hydrogen concentration is determined to be higher than the predetermined concentration value, the PLC 7 determines whether the alkaline water electrolysis apparatus 1 is operating. Is determined.
　（ステップＳ１０８）
　ステップＳ１０８では、ステップＳ１０７においてアルカリ型水電解装置１が運転されていると判定された場合、ＰＬＣ７は、電源からの供給電力が、アルカリ型水電解装置１の運転継続閾値よりも大きいか否かの判定を行う。ここで、運転継続閾値は、供給される電力がこの値以下となるとアルカリ型水電解装置１から発生する酸素に含まれる水素の濃度が急激に上昇するような値に設定される。すなわち、先に説明した運転注意領域に設定される値である。そのため、運転継続閾値はステップＳ１０２の所定値よりも低い値となる。アルカリ型水電解装置１から発生する酸素に含まれる水素の濃度が急激に上昇する電力の閾値として、例えば図６において、アルカリ型水電解装置１に流れる電流の低下に伴い発生する酸素中の水素濃度が上昇するような電流値である（電流密度０．１８Ａｃｍ－２）を採用してもよい。また、これよりも低い電流値を採用してもよい。運転注意領域内でより低い電流値を採用することにより、より長くアルカリ型水電解装置１を使用することができる。本動作例１では、このような運転継続閾値として、０．０６Ａｃｍ－２に対応する電力値を設定する。これは、アルカリ型水電解装置１の定格電流の１０％に相当する電力である。 (Step S108)
In step S108, when it is determined in step S107 that the alkaline water electrolysis apparatus 1 is operating, the PLC 7 determines whether or not the power supplied from the power supply is larger than the operation continuation threshold of the alkaline water electrolysis apparatus 1. Is determined. Here, the operation continuation threshold value is set to a value such that when the supplied electric power becomes equal to or less than this value, the concentration of hydrogen contained in oxygen generated from the alkaline water electrolysis apparatus 1 sharply increases. That is, the value is set in the driving caution area described above. Therefore, the operation continuation threshold value is lower than the predetermined value in step S102. As a threshold value of the electric power at which the concentration of hydrogen contained in oxygen generated from the alkaline water electrolysis device 1 rapidly increases, for example, in FIG. 6, hydrogen in oxygen generated due to a decrease in current flowing through the alkaline water electrolysis device 1 A current value that increases the concentration (current density of 0.18 Acm −2 ) may be employed. Further, a lower current value may be employed. By employing a lower current value in the driving caution region, the alkaline water electrolysis apparatus 1 can be used for a longer time. In the first operation example, a power value corresponding to 0.06 Acm −2 is set as such an operation continuation threshold. This is power corresponding to 10% of the rated current of the alkaline water electrolysis device 1.
　そして、ステップＳ１０８において電源からの供給電力が運転継続閾値よりも大きいと判定された場合、ステップＳ１０３の処理が実行され、ＡＣ／ＤＣコンバータ６Ａからアルカリ型水電解装置１への供給電流を決定する。 If it is determined in step S108 that the power supplied from the power supply is larger than the operation continuation threshold, the process of step S103 is performed, and the supply current from the AC / DC converter 6A to the alkaline water electrolysis device 1 is determined. .
　また、ステップＳ１０８において電源からの供給電力が運転継続閾値以下であると判定された場合、ステップＳ１０５の処理が実行され、ＰＬＣ７は、アルカリ型水電解装置１へ電流を供給しないことを決定する。 If it is determined in step S108 that the power supplied from the power supply is equal to or less than the operation continuation threshold, the process of step S105 is performed, and the PLC 7 determines not to supply a current to the alkaline water electrolysis apparatus 1.
　（ステップＳ１０９）
　ステップＳ１０９では、ステップＳ１０７においてアルカリ型水電解装置１が運転されていないと判定された場合、電源から供給される電力が、アルカリ型水電解装置１の運転開始閾値よりも大きいか否かの判定を行う。ここで、運転開始閾値は、運転継続閾値のみでアルカリ型水電解装置１の運転をＯＮ／ＯＦＦ制御した場合に生じる可能性がある頻繁なＯＮ／ＯＦＦの切り替わりを防止する目的で設けられる値である。このため、運転継続閾値よりもやや高い値に設定されるものであるが、運転継続閾値と近い値に設定される。 (Step S109)
In step S109, when it is determined in step S107 that the alkaline water electrolysis apparatus 1 is not operating, it is determined whether the power supplied from the power supply is larger than the operation start threshold value of the alkaline water electrolysis apparatus 1. I do. Here, the operation start threshold is a value provided for the purpose of preventing frequent ON / OFF switching that may occur when ON / OFF control of the operation of the alkaline water electrolysis apparatus 1 is performed only with the operation continuation threshold. is there. For this reason, although it is set to a value slightly higher than the operation continuation threshold, it is set to a value close to the operation continuation threshold.
　そして、電源から供給される電力が、アルカリ型水電解装置１の運転開始閾値よりも大きいと判定された場合、ステップＳ１０３の処理が実行され、ＡＣ／ＤＣコンバータ６Ａからアルカリ型水電解装置１への供給電流を決定する。 Then, when it is determined that the power supplied from the power supply is larger than the operation start threshold value of the alkaline water electrolysis device 1, the process of step S103 is executed, and the AC / DC converter 6A transfers the alkaline water electrolysis device 1 to the alkaline water electrolysis device 1. Is determined.
　一方、電源から供給される電力が、アルカリ型水電解装置１の運転開始閾値以下であると判定された場合、ステップＳ１０５の処理が実行され、ＰＬＣ７は、アルカリ型水電解装置１へ電流を供給しないことを決定する。 On the other hand, when it is determined that the electric power supplied from the power supply is equal to or less than the operation start threshold value of the alkaline water electrolysis device 1, the process of step S105 is executed, and the PLC 7 supplies a current to the alkaline water electrolysis device 1. Decide not to.
　（ステップＳ１１０）
　ステップＳ１１０では、ステップＳ１０５の処理が実行され、ＰＬＣ７がアルカリ型水電解装置１へ電流を供給しないことを決定した後、ＰＬＣ７は高分子型水電解装置２が運転中であるか否かの判定を行う。 (Step S110)
In step S110, the process in step S105 is performed, and after determining that the PLC 7 does not supply current to the alkaline water electrolysis device 1, the PLC 7 determines whether the polymer water electrolysis device 2 is operating. I do.
　（ステップＳ１１１）
　ステップＳ１１１では、ステップＳ１１０において高分子型水電解装置２が運転中であると判定された場合に、ＰＬＣ７は、電源からの供給電力が高分子型水電解装置２の運転継続閾値よりも大きいか否かの判定を行う。なお、本動作例１の高分子型水電解装置２では、電解液として純水を用いているため、この高分子型水電解装置２の運転継続閾値はほぼゼロに設定される。 (Step S111)
In step S111, when it is determined in step S110 that the polymer water electrolysis device 2 is operating, the PLC 7 determines whether the power supplied from the power supply is larger than the operation continuation threshold of the polymer water electrolysis device 2. It is determined whether or not it is. In the polymer water electrolysis apparatus 2 of the first operation example, since pure water is used as the electrolytic solution, the operation continuation threshold of the polymer water electrolysis apparatus 2 is set to almost zero.
　（ステップＳ１１２）
　ステップＳ１１２では、ステップＳ１１１において、電源からの供給電力が高分子型水電解装置２の運転継続閾値よりも大きいと判定された場合、ＰＬＣ７は、高分子型水電解装置２へ電流を供給することを決定する。また、ＰＬＣ７は、高分子型水電解装置２への供給電流を決定する。 (Step S112)
In step S112, if it is determined in step S111 that the power supplied from the power supply is larger than the operation continuation threshold of the polymer water electrolysis device 2, the PLC 7 supplies a current to the polymer water electrolysis device 2. To determine. Further, the PLC 7 determines a supply current to the polymer-type water electrolysis device 2.
　（ステップＳ１１３）
　ステップＳ１１３では、ステップＳ１１１において、電源からの供給電力が高分子型水電解装置２の運転継続閾値以下であると判定された場合、ＰＬＣ７は、高分子型水電解装置２へ電流を供給しないことを決定する。 (Step S113)
In step S113, if it is determined in step S111 that the power supplied from the power supply is equal to or less than the operation continuation threshold value of the polymer water electrolysis device 2, the PLC 7 does not supply a current to the polymer water electrolysis device 2. To determine.
　また、上記のステップＳ１１３の処理は、ステップＳ１０３において、アルカリ型水電解装置１への電流の供給が決定された後にも実行される。 {Circle around (2)} The above-described processing in step S113 is also executed after the supply of current to the alkaline water electrolysis apparatus 1 is determined in step S103.
　（ステップＳ１１４）
　ステップＳ１１４では、ステップＳ１１０において高分子型水電解装置２が運転中ではないと判定された場合に、ＰＬＣ７は、電源からの供給電力が高分子型水電解装置２の運転開始閾値よりも大きいか否かの判定を行う。 (Step S114)
In step S114, when it is determined in step S110 that the polymer water electrolysis device 2 is not in operation, the PLC 7 determines whether the power supplied from the power supply is larger than the operation start threshold value of the polymer water electrolysis device 2. It is determined whether or not it is.
　ステップＳ１１４において、電源からの供給電力が高分子型水電解装置２の運転開始閾値よりも大きいと判定された場合、ステップＳ１１２の処理が実行され、ＡＣ／ＤＣコンバータ６Ｂから、高分子型水電解装置２への供給電流が決定される。 When it is determined in step S114 that the power supplied from the power supply is greater than the operation start threshold value of the polymer water electrolysis device 2, the process of step S112 is executed, and the polymer water electrolysis is performed by the AC / DC converter 6B. The supply current to the device 2 is determined.
　また、ステップＳ１１４において、電源からの供給電力が高分子型水電解装置２の運転開始閾値以下であると判定された場合、ステップＳ１１３の処理が実行され、ＰＬＣ７は、高分子型水電解装置２へ電流を供給しないことを決定する。なお、本動作例１の高分子型水電解装置２の運転開始閾値は、高分子型水電解装置２の運転継続閾値よりもやや高く設定される。 When it is determined in step S114 that the power supplied from the power supply is equal to or less than the operation start threshold value of the polymer water electrolysis device 2, the process of step S113 is executed, and the PLC 7 Decide not to supply current to Note that the operation start threshold value of the polymer water electrolysis device 2 of Operation Example 1 is set to be slightly higher than the operation continuation threshold value of the polymer water electrolysis device 2.
　（ステップＳ１１５）
　ステップＳ１１５では、ＰＬＣ７で作成した各電流指令値がＡＣ／ＤＣコンバータ６Ａ、６Ｂへそれぞれ送信される。ＡＣ／ＤＣコンバータ６Ａ、６Ｂは、受信した電流指令値に基づいて、電源から供給される電力を所定の直流電流に変換する。そして、当該電流は、アルカリ型水電解装置１、及び高分子型水電解装置２へそれぞれ出力される。 (Step S115)
In step S115, the current command values created by the PLC 7 are transmitted to the AC / DC converters 6A and 6B, respectively. The AC / DC converters 6A and 6B convert the power supplied from the power supply into a predetermined DC current based on the received current command value. Then, the current is output to the alkaline water electrolysis device 1 and the polymer water electrolysis device 2, respectively.
　＜作用・効果＞
　上記のような水電解システム１００では、図５に示されるように、電源からの供給電力が変動すると、システムに供給される電流が変動する。この際、アルカリ型水電解装置１に対する制御を行わないシステムでは、供給電力が低下すると、陽極３Ａにおいて酸素生成量が減少し、迷走電流が相対的に増加する。その結果陽極３Ａから発生する酸素中に水素が多く含まれることとなる。よって、水電解システム１００の運用に影響が及ぶ虞がある。 <Action / Effect>
In the water electrolysis system 100 as described above, as shown in FIG. 5, when the power supplied from the power supply fluctuates, the current supplied to the system fluctuates. At this time, in a system that does not control the alkaline water electrolysis device 1, when the supply power decreases, the amount of oxygen generated at the anode 3A decreases, and the stray current relatively increases. As a result, oxygen generated from the anode 3A contains a large amount of hydrogen. Therefore, the operation of the water electrolysis system 100 may be affected.
　そこで、上記の動作例１では、ステップＳ１０８，Ｓ１０９の処理が実行されることにより、電源から供給される電力が、アルカリ型水電解装置１の定格電流の１０％の電流値に相当する電力値よりも大きいか否かが判定される。そして、電源から供給される電力が、アルカリ型水電解装置１の定格電流の１０％の電流値に相当する電力値以下である場合、ステップＳ１０５の処理が実行されることによってアルカリ型水電解装置１へ電流の供給が停止される。そして、ステップＳ１１２の処理が実行されることによって高分子型水電解装置２へ電流が供給される。 Therefore, in the above-described operation example 1, by performing the processing of steps S108 and S109, the power supplied from the power supply is changed to a power value corresponding to a current value of 10% of the rated current of the alkaline water electrolysis apparatus 1. It is determined whether it is greater than or equal to. When the power supplied from the power supply is equal to or less than the power value corresponding to a current value of 10% of the rated current of the alkaline water electrolysis device 1, the process of step S105 is executed to thereby execute the alkaline water electrolysis device. The supply of current to 1 is stopped. Then, a current is supplied to the polymer-type water electrolysis device 2 by performing the process of step S112.
　加えて、ステップＳ１０２の処理が実行されることにより、陽極４Ａ側の水素濃度が高い状態となったとしても、陽極４Ａ側の水素濃度を低下させることができる。このように水素濃度の回復機能を備えるため、アルカリ型水電解装置１の運転を制御するための閾値を、発生する酸素中の水素濃度が比較的高い濃度に対応する電力値に設定することが可能となる。 In addition, by performing the process of step S102, even if the hydrogen concentration on the anode 4A side becomes high, the hydrogen concentration on the anode 4A side can be reduced. In order to provide the hydrogen concentration recovery function as described above, the threshold value for controlling the operation of the alkaline water electrolysis apparatus 1 may be set to an electric power value corresponding to the concentration at which the hydrogen concentration in the generated oxygen is relatively high. It becomes possible.
　一方、高分子型水電解装置２は、高分子を含む電解質５を含み、純水に浸される陽極４Ａ及び陰極４Ｂが電解質５を挟んで設けられている。そして、陽極４Ａ及び陰極４Ｂに、電流が流入することにより、陽極４Ａ近傍で純水からプロトン及び酸素を発生させ、プロトンを陰極４Ｂ近傍へ電解質５を介して移動させ、陰極４Ｂ近傍から水素を発生させている。このような高分子型水電解装置２では、低負荷で運転した場合であっても迷走電流の発生は抑制される。よって、高分子型水電解装置２から発生する酸素に含まれる水素の濃度が上昇することは抑制される。また、高分子型水電解装置２へ配分される電流が変動した場合であっても、高分子型水電解装置２から発生する酸素に含まれる水素の濃度が上昇することは抑制される。 On the other hand, the polymer-type water electrolysis device 2 includes an electrolyte 5 containing a polymer, and an anode 4A and a cathode 4B immersed in pure water are provided with the electrolyte 5 interposed therebetween. Then, when current flows into the anode 4A and the cathode 4B, protons and oxygen are generated from pure water near the anode 4A, the protons are moved to the vicinity of the cathode 4B via the electrolyte 5, and hydrogen is removed from the vicinity of the cathode 4B. Is occurring. In such a polymer water electrolysis device 2, generation of stray current is suppressed even when the device is operated at a low load. Therefore, an increase in the concentration of hydrogen contained in oxygen generated from the polymer water electrolysis device 2 is suppressed. Further, even when the current distributed to the polymer water electrolysis device 2 fluctuates, an increase in the concentration of hydrogen contained in oxygen generated from the polymer water electrolysis device 2 is suppressed.
　ここで、水電解システム１００を動作例１のように動作させた場合、発生する酸素中の水素濃度の急激な上昇が実際に抑制されるか確認を行った。図７は、水電解システム１００を動作例１のように実際に動作させた場合における、アルカリ型水電解装置１の陽極３Ａから発生する酸素に含まれる水素の濃度と、アルカリ型水電解装置のみを稼働させた場合に陽極から発生する酸素に含まれる水素の濃度との比較の一例を示している。図７に示されるように、風力発電設備から水電解装置へ供給される電力は変動している。しかしながら、水電解システム１００のアルカリ型水電解装置１から発生する酸素中の水素濃度は、９０００ｐｐｍから１００００ｐｐｍであり、アルカリ型水電解装置のみを稼働させた場合に発生する酸素中の水素濃度（１１０００ｐｐｍから１２０００ｐｐｍ）よりも定常的に低い。すなわち、図７より、電源からの供給電力が変動した場合であっても、水電解システム１００は、アルカリ型水電解装置１から発生する酸素中の水素濃度の上昇を抑制できることが認められる。よって、水電解システム１００を動作例１のように動作させた場合、水電解システム１００の運用に影響が及ぶことは抑制される。なお、運転期間の初期に水素濃度が著しく上昇している点があるが、これは電流をゼロから上昇させるために生じた部分であるため、効果を検証する際には除外している。 Here, when the water electrolysis system 100 was operated as in the operation example 1, it was confirmed whether the rapid increase in the hydrogen concentration in the generated oxygen was actually suppressed. FIG. 7 shows the concentration of hydrogen contained in oxygen generated from the anode 3A of the alkaline water electrolysis apparatus 1 when the water electrolysis system 100 is actually operated as in Operation Example 1, and only the alkaline water electrolysis apparatus. 5 shows an example of comparison with the concentration of hydrogen contained in oxygen generated from the anode when the device is operated. As shown in FIG. 7, the power supplied from the wind power generation equipment to the water electrolysis device is fluctuating. However, the hydrogen concentration in oxygen generated from the alkaline water electrolysis device 1 of the water electrolysis system 100 is from 9000 ppm to 10000 ppm, and the hydrogen concentration in oxygen generated when only the alkaline water electrolysis device is operated (11000 ppm) From 12000 ppm). That is, from FIG. 7, it is recognized that the water electrolysis system 100 can suppress an increase in the concentration of hydrogen in oxygen generated from the alkaline water electrolysis apparatus 1 even when the power supplied from the power supply fluctuates. Therefore, when the water electrolysis system 100 is operated as in the operation example 1, the operation of the water electrolysis system 100 is not affected. Note that there is a point where the hydrogen concentration is significantly increased at the beginning of the operation period. However, this is a portion generated to increase the current from zero, and is excluded when verifying the effect.
　また、上記の動作例では、ステップＳ１０８におけるアルカリ型水電解装置１の運転継続閾値、ステップＳ１０９におけるアルカリ型水電解装置１の運転開始閾値を、アルカリ型水電解装置１の定格電流の約１０％の電流をアルカリ型水電解装置１へ流してもよいこととした。しかし、これに限らず、先の述べた運転注意領域に相当する、アルカリ型水電解装置１の定格電流の１０％～３０％の範囲で適宜設定してもよい。より低い値を採用することで、アルカリ型水電解装置１が運用できる供給電力の範囲を広げることが可能となる。一方、より高い値を採用することで、陽極４Ａ側の水素濃度が高くなることをより防ぐことができる。 In the above operation example, the operation continuation threshold value of the alkaline water electrolysis apparatus 1 in step S108 and the operation start threshold value of the alkaline water electrolysis apparatus 1 in step S109 are set to about 10% of the rated current of the alkaline water electrolysis apparatus 1. May be passed to the alkaline water electrolysis apparatus 1. However, the present invention is not limited to this, and may be appropriately set in the range of 10% to 30% of the rated current of the alkaline water electrolysis device 1 corresponding to the above-mentioned driving caution region. By adopting a lower value, it is possible to widen the range of supply power that the alkaline water electrolysis apparatus 1 can operate. On the other hand, by adopting a higher value, it is possible to further prevent an increase in the hydrogen concentration on the anode 4A side.
　さらに、運転注意領域に限らず、運転回避領域に相当するアルカリ型水電解装置１の定格電流を採用してもよい。このような運用を行えば、アルカリ型水電解装置１の運用範囲を広げることが可能となる。 Furthermore, the rated current of the alkaline water electrolysis apparatus 1 corresponding to the driving avoidance region may be employed instead of the driving caution region. By performing such operation, the operation range of the alkaline water electrolysis device 1 can be expanded.
　また、運転注意領域に限らず、濃度回復領域に相当する電力の値をステップＳ１０８におけるアルカリ型水電解装置１の運転継続閾値やステップＳ１０９の運転開始閾値に設定してもよい。このように設定すれば、アルカリ型水電解装置１を運用する供給電力の範囲は狭くなるもの、陽極４Ａ側で発生する酸素中の水素濃度を低い状態でし続けることが可能となる。 Further, the power value corresponding to the concentration recovery region is not limited to the operation caution region, and may be set as the operation continuation threshold value of the alkaline water electrolysis apparatus 1 in step S108 or the operation start threshold value in step S109. With this setting, although the range of power supply for operating the alkaline water electrolysis apparatus 1 is narrowed, it is possible to keep the concentration of hydrogen in oxygen generated on the anode 4A side low.
　加えて、上記の動作例では、ステップＳ１０２において判定に使用される所定値を、アルカリ型水電解装置１の定格電流の３０％の電流をアルカリ型水電解装置１へ流すことのできる値とした。しかし、これに限らず、４０％の電流をアルカリ型水電解装置１へ流すことのできる電力値としてもよい。濃度回復領域の運転開始の所定値を高くすることにより、より高い供給電力から水素濃度の回復運転を開始することが可能となる。なお、濃度回復領域の開始の所定値を高くすると、発生する酸素の量が増加することとなる。このため、酸素中の水素濃度を確実に低下することができ、また酸素中の水素濃度を低下させる速度を早くすることができる。 In addition, in the above operation example, the predetermined value used for the determination in step S102 is a value that allows 30% of the rated current of the alkaline water electrolysis device 1 to flow to the alkaline water electrolysis device 1. . However, the power value is not limited to this, and may be a power value that allows a current of 40% to flow to the alkaline water electrolysis apparatus 1. By increasing the predetermined value of the operation start in the concentration recovery region, it is possible to start the hydrogen concentration recovery operation from higher supply power. It should be noted that increasing the predetermined value at the start of the concentration recovery region increases the amount of generated oxygen. For this reason, the hydrogen concentration in oxygen can be reliably reduced, and the speed at which the hydrogen concentration in oxygen can be reduced can be increased.
　なお、図６に例示される電流密度と水素濃度との関係は、電解液の濃度、電解装置の容量、電解槽のセル数等の条件により変化するものである。このため、上述で説明した水素濃度に対応した運転の領域を区別した電流密度の値は、説明した数値に限定されるものではない。また、電流に対応する酸素中水素濃度は定常状態において計測された実測値をプロットしたものである。このため、電流が変化した場合には、酸素中の水素濃度は図６に示される電流密度に対応する水素濃度に常に一致するわけではなく、追従にタイムラグが生じることがある。 The relationship between the current density and the hydrogen concentration illustrated in FIG. 6 changes depending on conditions such as the concentration of the electrolytic solution, the capacity of the electrolytic device, and the number of cells in the electrolytic cell. For this reason, the value of the current density that distinguishes the operation region corresponding to the hydrogen concentration described above is not limited to the numerical value described above. Further, the hydrogen concentration in oxygen corresponding to the current is obtained by plotting an actually measured value measured in a steady state. Therefore, when the current changes, the hydrogen concentration in oxygen does not always match the hydrogen concentration corresponding to the current density shown in FIG. 6, and a time lag may occur in following.
　また、本発明の実施形態における制御手段の一例であるＡＣ／ＤＣコンバータ６Ａ、６Ｂ及びＰＬＣ７は、電源と接続する水電解装置を第一の水電解装置の一例であるアルカリ型水電解装置１と、第二の水電解装置の一例である高分子型水電解装置２との間で切り替えることができる。 Further, the AC / DC converters 6A, 6B and the PLC 7, which are examples of the control means in the embodiment of the present invention, are configured such that the water electrolysis device connected to the power supply is the same as the alkaline water electrolysis device 1 which is an example of the first water electrolysis device. And the polymer water electrolysis device 2 which is an example of the second water electrolysis device.
　上記のような水電解システム１００であれば、電源とアルカリ型水電解装置１とが接続している場合であって、電源から供給される電力が低下した場合、電源と接続する電解装置を高分子型水電解装置２へ素早く切り替えることができる。よって、アルカリ型水電解装置１において迷走電流が相対的に増加することは素早く抑制され、その結果、アルカリ型水電解装置１の陽極３Ａから発生する酸素に水素が混合されることは素早く抑制される。また、陰極３Ｂにおいても同様に、発生する水素に酸素が混合されることは素早く抑制される。また、ＡＣ／ＤＣコンバータ６Ａ、６ＢやＰＬＣ７から形成される水電解システム１００は、複雑な構造ではない。すなわち、陽極３Ａにおいて発生する酸素に含まれる水素の濃度の上昇、及び陰極３Ｂにおいて発生する水素に含まれる酸素の濃度の上昇は、簡易に抑制される。 In the case of the water electrolysis system 100 as described above, when the power supply is connected to the alkaline water electrolysis apparatus 1 and the power supplied from the power supply decreases, the electrolysis apparatus connected to the power supply is raised. It is possible to quickly switch to the molecular water electrolysis device 2. Therefore, the relative increase in the stray current in the alkaline water electrolysis device 1 is quickly suppressed, and as a result, the mixing of hydrogen with oxygen generated from the anode 3A of the alkaline water electrolysis device 1 is quickly suppressed. You. Similarly, in the cathode 3B, the mixing of oxygen with the generated hydrogen is quickly suppressed. In addition, the water electrolysis system 100 formed from the AC / DC converters 6A and 6B and the PLC 7 does not have a complicated structure. That is, an increase in the concentration of hydrogen contained in oxygen generated at the anode 3A and an increase in the concentration of oxygen contained in hydrogen generated at the cathode 3B are easily suppressed.
　また、上記のような水電解システム１００は、ステップＳ１０４の判定処理の実行により、アルカリ型水電解装置１において発生する酸素に含まれる水素の濃度が所定濃度値以上であるか否かの判定が行われ、所定濃度値以上である場合にステップＳ１０５の処理が実行されることにより、アルカリ型水電解装置１への電流の供給が停止される判断が行われる。すなわち、上記のような水電解システム１００は、ＡＣ／ＤＣコンバータ６Ａ、６ＢやＰＬＣ７が、電源から供給される電力をアルカリ型水電解装置１及び高分子型水電解装置２への配分を、電源から供給される電力に加えて第一の水電解装置から発生する酸素に含まれる水素の濃度に応じても制御している。このような水電解システム１００は、酸素に含まれる水素の濃度を判定することによっても、アルカリ型水電解装置１へ配分される電力を調整し、アルカリ型水電解装置１の陽極３Ａから水素を多く含む酸素の発生を抑制することができる。 In addition, the water electrolysis system 100 as described above determines whether or not the concentration of hydrogen contained in oxygen generated in the alkaline water electrolysis device 1 is equal to or higher than a predetermined concentration value by performing the determination process in step S104. The determination is made that the supply of the current to the alkaline water electrolysis apparatus 1 is stopped by performing the processing of step S105 when the concentration is equal to or higher than the predetermined concentration value. That is, in the water electrolysis system 100 as described above, the AC / DC converters 6A and 6B and the PLC 7 distribute the power supplied from the power supply to the alkaline water electrolysis apparatus 1 and the polymer water electrolysis apparatus 2 by using a power supply. Is controlled according to the concentration of hydrogen contained in oxygen generated from the first water electrolysis device in addition to the electric power supplied from the first water electrolysis device. Such a water electrolysis system 100 also adjusts the power distributed to the alkaline water electrolysis device 1 by determining the concentration of hydrogen contained in oxygen, and converts hydrogen from the anode 3A of the alkaline water electrolysis device 1 to hydrogen. Generation of oxygen containing much can be suppressed.
　＜動作例２＞
　上記の動作例１では、陽極４Ａ側の水素濃度が高い状態になっていた場合に、陽極４Ａ側の酸素中の水素濃度を低下させることを目的として、ステップＳ１０２において所定値を設定して制御を行っていた。本動作例２では、図４に示されるフロー図において、ステップＳ１０２を設ける代わりに、陽極４Ａ側の水素濃度に応じて、ステップＳ１０８の運転継続閾値、ステップＳ１０９の運転開始閾値を変更する構成となっている。換言すると、図４に示すフロー図において、ステップＳ１０２が省略され、代わりにステップＳ１０８の運転継続閾値とステップＳ１０９の運転開始閾値が、水素濃度に応じて変更するフローが追加される。他の構成は動作例１と共通する点が多いため、共通する構成の説明は省略する。 <Operation example 2>
In the above-described operation example 1, when the hydrogen concentration on the anode 4A side is high, the predetermined value is set and controlled in step S102 for the purpose of reducing the hydrogen concentration in the oxygen on the anode 4A side. Had gone. In the second operation example, in the flowchart shown in FIG. 4, instead of providing step S102, the operation continuation threshold value in step S108 and the operation start threshold value in step S109 are changed according to the hydrogen concentration on the anode 4A side. Has become. In other words, in the flowchart shown in FIG. 4, step S102 is omitted, and instead, a flow is added in which the operation continuation threshold value in step S108 and the operation start threshold value in step S109 are changed according to the hydrogen concentration. The other configurations have many points in common with the operation example 1, and a description of the common configurations will be omitted.
　通常、ステップＳ１０８の運転継続閾値、及びステップＳ１０９の運転開始閾値は、アルカリ型水電解装置１の定格電流の１０％に相当する電力値に設定される。そして、ステップＳ１０４の処理の実行の際に使用される酸素中の水素の濃度所定値は１１０００ｐｐｍなどに設定される。 Usually, the operation continuation threshold value in step S108 and the operation start threshold value in step S109 are set to an electric power value corresponding to 10% of the rated current of the alkaline water electrolysis device 1. Then, the predetermined value of the concentration of hydrogen in oxygen used at the time of executing the processing of step S104 is set to 11000 ppm or the like.
　ここで、ステップＳ１０４の処理を実行した結果、アルカリ型水電解装置１から発生する酸素中の水素濃度が１１０００ｐｐｍより高い濃度であることが判明した場合、ステップＳ１０８の運転継続閾値、及びステップＳ１０９の運転開始閾値は、酸素を十分に発生させることができ、運転を継続することによって陽極３Ａ側の水素濃度を低下させることができるような電力となるような値に一定期間変更される。一例として、本動作例ではアルカリ型水電解装置１の定格電流の３０％に相当する電力に設定される。（以下、濃度異常モードという）。なお、この期間は、陽極４Ａ側の水素濃度により定めてもよく、あらかじめ定めた時間としてもよい。このため、濃度異常モード中は、アルカリ型水電解装置１は酸素中に存在している高濃度の水素を希釈することができる電力が供給される場合のみ運転されることとなる。そして、一定期間経過後、濃度異常モードは終了する。 Here, as a result of executing the processing of step S104, when it is determined that the concentration of hydrogen in oxygen generated from the alkaline water electrolysis device 1 is higher than 11000 ppm, the operation continuation threshold value of step S108 and the operation continuation threshold value of step S109 The operation start threshold is changed for a certain period of time to a value such that sufficient oxygen can be generated and the power can be reduced such that the hydrogen concentration on the anode 3A side can be reduced by continuing the operation. As an example, in this operation example, the power is set to 30% of the rated current of the alkaline water electrolysis device 1. (Hereinafter, referred to as density abnormal mode). This period may be determined based on the hydrogen concentration on the anode 4A side, or may be a predetermined time. For this reason, during the abnormal concentration mode, the alkaline water electrolysis apparatus 1 is operated only when electric power capable of diluting high-concentration hydrogen existing in oxygen is supplied. Then, after a certain period of time, the abnormal density mode ends.
　図８は、水電解システム１００が上記のように動作した場合のアルカリ型水電解装置１から発生する酸素中の水素濃度の計測値の経時変化を示している。また、電源から水電解システム１００へ供給される電流値の経時変化も重ねて示している。ただし、電流値は、アルカリ型水電解装置１の定格電流に対する割合で表されている。図８に示されるように、電源から供給される電流は変動していることが認められる。 FIG. 8 shows a temporal change in the measured value of the hydrogen concentration in oxygen generated from the alkaline water electrolysis apparatus 1 when the water electrolysis system 100 operates as described above. In addition, a temporal change of a current value supplied from the power supply to the water electrolysis system 100 is also shown. However, the current value is expressed as a ratio to the rated current of the alkaline water electrolysis device 1. As shown in FIG. 8, it is recognized that the current supplied from the power supply is fluctuating.
　水電解システム１００は、運転開始当初、運転継続閾値や運転開始閾値が定格電流の１０％に相当する電力値に設定されている。このため、電源から供給される電力が変動している場合に、アルカリ型水電解装置１が低負荷の運転注意領域であっても運転されることを許容する。このとき、酸素に含まれる水素の濃度は急激に上昇せず、低負荷での運転がしばらく継続されていることが図８より認められる。 In the water electrolysis system 100, at the beginning of the operation, the operation continuation threshold and the operation start threshold are set to electric power values corresponding to 10% of the rated current. For this reason, when the electric power supplied from the power supply is fluctuating, the alkaline water electrolysis apparatus 1 is allowed to be operated even in a low load operation caution area. At this time, it can be seen from FIG. 8 that the concentration of hydrogen contained in oxygen does not increase rapidly and the operation at a low load is continued for a while.
　その後、アルカリ型水電解装置１から発生する水素濃度は、運転開始から１０分程度経過すると１１０００ｐｐｍとなる。そして、水素濃度が１１０００ｐｐｍとなったため、水素濃度が所定値に達したと判断し、水電解システム１００の運転は、一旦停止される。その後、運転モードは、濃度異常モードへと変更されている。 Thereafter, the concentration of hydrogen generated from the alkaline water electrolysis apparatus 1 becomes 11000 ppm about 10 minutes after the start of operation. Then, since the hydrogen concentration has reached 11000 ppm, it is determined that the hydrogen concentration has reached the predetermined value, and the operation of the water electrolysis system 100 is temporarily stopped. Thereafter, the operation mode has been changed to the abnormal concentration mode.
　濃度異常モードでは、閾値がアルカリ型水電解装置１の定格電流の３０％に相当する電力値に引き上げられるため、アルカリ型水電解装置１は陽極４Ａ側の水素濃度を低下させることができる電力が供給される場合に動作することになる。そして、水電解システム１００は、所定期間経過後、濃度異常モードは終了する。なお言うまでもないが、濃度異常モードでは、陽極４Ａ側の水素濃度を低下させることができる電力が供給されない場合、アルカリ型水電解装置１は動作を停止した状態となる。 In the abnormal concentration mode, the threshold value is raised to a power value corresponding to 30% of the rated current of the alkaline water electrolysis device 1, so that the alkaline water electrolysis device 1 has an electric power capable of reducing the hydrogen concentration on the anode 4A side. It will work when supplied. Then, in the water electrolysis system 100, after the elapse of the predetermined period, the concentration abnormal mode ends. Needless to say, in the abnormal concentration mode, when the power capable of lowering the hydrogen concentration on the anode 4A side is not supplied, the operation of the alkaline water electrolysis apparatus 1 is stopped.
　上記のような水電解システム１００であれば、電源から供給される電力が低下した場合であっても、動作例１と同様の効果が得られる。 で あ れ ば With the water electrolysis system 100 as described above, the same effects as in Operation Example 1 can be obtained even when the power supplied from the power supply is reduced.
　＜動作例３＞
　上記の動作例１および動作例２では、陽極３Ａ側の水素濃度が高い状態になっていた場合に、陽極３Ａ側の酸素中の水素濃度を低下させるための制御を行っていた。本動作例３は、陽極３Ａ側の酸素中の水素濃度を低下させるための制御を有しない最も簡単な構成の動作例である。すなわち、図４に示されるフロー図において、ステップＳ１０２を行わない構成となっている。他の構成は動作例１と共通する点が多いため、共通する構成や動作の説明は省略する。 <Operation example 3>
In the above-described operation examples 1 and 2, when the hydrogen concentration on the anode 3A side is in a high state, control is performed to reduce the hydrogen concentration in oxygen on the anode 3A side. This operation example 3 is an operation example of the simplest configuration having no control for lowering the hydrogen concentration in oxygen on the anode 3A side. That is, in the flowchart shown in FIG. 4, the configuration is such that step S102 is not performed. Since other configurations have many points in common with Operation Example 1, description of common configurations and operations will be omitted.
　本実施例では酸素中の水素濃度を低下させるための制御を有しないため、運転継続閾値および運転開始閾値を上記の動作例１よりも高い値に設定することが好ましい。例えば、濃度回復領域の水素濃度に対応する、アルカリ型水電解装置１の定格電流の４０％の電流値に相当する電力値に設定する。このように設定すれば、ステップＳ１０８，Ｓ１０９の処理が実行されることにより、電源から供給される電力が、アルカリ型水電解装置１の定格電流の４０％の電流値に相当する電力値よりも大きいか否かが判定される。そして、電源から供給される電力が、アルカリ型水電解装置１の定格電流の４０％の電流値に相当する電力値以下である場合、ステップＳ１０５の処理が実行されることによってアルカリ型水電解装置１へ電流の供給が停止される。そして、ステップＳ１１２の処理が実行されることによって高分子型水電解装置２へ電流が供給される。このように、アルカリ型水電解装置１を濃度回復領域の水素濃度に対応する電力で動作させるため、陽極３Ａ側の酸素中の水素濃度が高い状態になることを回避することができる。 In this embodiment, since there is no control for reducing the hydrogen concentration in oxygen, it is preferable to set the operation continuation threshold and the operation start threshold to values higher than those in the first operation example. For example, the power value is set to a power value corresponding to a current value of 40% of the rated current of the alkaline water electrolysis device 1 corresponding to the hydrogen concentration in the concentration recovery region. With this setting, the power supplied from the power supply is made larger than the power value corresponding to a current value of 40% of the rated current of the alkaline water electrolysis device 1 by performing the processing of steps S108 and S109. It is determined whether it is larger. When the power supplied from the power supply is equal to or less than the power value corresponding to a current value of 40% of the rated current of the alkaline water electrolysis apparatus 1, the processing in step S105 is executed to execute the processing in step S105. The supply of current to 1 is stopped. Then, a current is supplied to the polymer-type water electrolysis device 2 by performing the process of step S112. As described above, since the alkaline water electrolysis apparatus 1 is operated with the power corresponding to the hydrogen concentration in the concentration recovery region, it is possible to avoid a state where the hydrogen concentration in the oxygen on the anode 3A side is high.
　なお、本動作例３において、運転継続閾値および運転開始閾値は運転注意領域の酸素中の水素濃度の対応する電力に設定してもよい。例えば、定格電流の２０％に相当する電力の値に設定する。ただし、本動作例では回復運転を行わないため、運転回避領域の酸素中の水素濃度に対応する電力は運転継続閾値および運転開始閾値に設定することを避けることが好ましい。 In the third operation example, the operation continuation threshold and the operation start threshold may be set to electric power corresponding to the hydrogen concentration in oxygen in the operation caution area. For example, the power is set to a value corresponding to 20% of the rated current. However, in this operation example, since the recovery operation is not performed, it is preferable to avoid setting the electric power corresponding to the hydrogen concentration in oxygen in the operation avoidance region to the operation continuation threshold and the operation start threshold.
　以上のような３つの動作例のように、水電解システム１００は動作可能である。また、上記の実施形態では、本発明の「第一の水電解装置」の一例して、重量濃度が約３０％程度の水酸化カリウム水溶液又は水酸化ナトリウム水溶液の電解液を有するアルカリ型水電解装置１を例示した。そして、本発明の「第二の水電解装置」の一例として、高分子を含む電解質５を含み、アルカリ型水電解装置１の電解液よりも導電性の低い純水に浸される陽極４Ａ及び陰極４Ｂが、電解質５を挟んで設けられる高分子型水電解装置２を例示した。しかし、第一の水電解装置と第二の水電解装置の組み合わせは、上記の実施形態の例に限られないのは勿論のことである。例えば、第一の水電解装置、及び第二の水電解装置ともに、アルカリ水溶液を含む電解液を有する水電解装置としてもよい。ただし、第二の水電解装置のアルカリ水溶液は、第一の水電解装置のアルカリ水溶液よりも導電性の低い水溶液とするべく、アルカリ化合物の重量濃度を希薄にする。第二の水電解装置のアルカリ水溶液中において発生する迷走電流は、水溶液のアルカリ濃度が希薄であるため、第一の水電解装置のアルカリ水溶液中において発生する迷走電流よりも少ないこととなる。よって、このような水電解システムであっても、電源から供給される電力を、第一の水電解装置と第二の水電解装置とへ、上記の実施形態と同様に配分する場合、発生する酸素に含まれる水素の濃度の上昇は抑制される同様の効果を奏する。また、上記の実施形態では、第二の水電解装置の第二の電解液の一例として純水を例示したが、第二の電解液は、第一の水電解装置の第一の電解液よりも導電性が低い電解液であれば何でもよいことは勿論のことである。 水 The water electrolysis system 100 can operate as in the three operation examples described above. Further, in the above embodiment, as an example of the “first water electrolysis device” of the present invention, an alkaline water electrolysis having an electrolyte of a potassium hydroxide aqueous solution or a sodium hydroxide aqueous solution having a weight concentration of about 30%. The device 1 has been exemplified. As an example of the “second water electrolysis device” of the present invention, an anode 4A including an electrolyte 5 containing a polymer and immersed in pure water having lower conductivity than the electrolyte of the alkaline water electrolysis device 1; The polymer water electrolysis device 2 in which the cathode 4B is provided with the electrolyte 5 interposed therebetween has been illustrated. However, it goes without saying that the combination of the first water electrolysis device and the second water electrolysis device is not limited to the example of the above embodiment. For example, both the first water electrolysis device and the second water electrolysis device may be water electrolysis devices having an electrolyte solution containing an aqueous alkaline solution. However, the alkaline aqueous solution of the second water electrolyzer is diluted in weight concentration of the alkali compound so as to be an aqueous solution having lower conductivity than the alkaline aqueous solution of the first water electrolyzer. The stray current generated in the alkaline aqueous solution of the second water electrolysis device is smaller than the stray current generated in the alkaline aqueous solution of the first water electrolysis device because the alkali concentration of the aqueous solution is low. Therefore, even in such a water electrolysis system, when the electric power supplied from the power supply is distributed to the first water electrolysis device and the second water electrolysis device in the same manner as in the above-described embodiment, this occurs. The same effect is obtained that the increase in the concentration of hydrogen contained in oxygen is suppressed. Further, in the above embodiment, pure water is exemplified as an example of the second electrolytic solution of the second water electrolyzer, but the second electrolytic solution is different from the first electrolytic solution of the first water electrolyzer. Of course, any electrolytic solution having low conductivity may be used.
　また、以上のような３つの動作例では、アルカリ型水電解装置１を動作させる場合には、高分子型水電解装置２の動作を停止するとした。しかし、アルカリ型水電解装置１を動作させる場合に高分子型水電解装置２を動作させてもよい。 In addition, in the above three operation examples, when the alkaline water electrolysis apparatus 1 is operated, the operation of the polymer water electrolysis apparatus 2 is stopped. However, when the alkaline water electrolysis device 1 is operated, the polymer water electrolysis device 2 may be operated.
１・・アルカリ型水電解装置；２・・高分子型水電解装置；３Ａ・・陽極；３Ｂ・・陰極；４Ａ・・陽極；４Ｂ・・陰極；５・・電解質；６Ａ、６Ｂ・・ＡＣ／ＤＣコンバータ；７・・ＰＬＣ；８・・水素タンク；５０・・発電設備；１００；水電解システム
  1 ·· Alkaline water electrolysis device; 2 ·· Polymer water electrolysis device; 3A ·· Anode; 3B ·· Cathode; 4A ·· Anode; 4B ·· Cathode; 5 ·· Electrolyte; 6A, 6B ·· AC / DC converter; 7 PLC; 8 hydrogen tank; 50 power generation equipment; 100; water electrolysis system

Claims (11)

  1. 　第一の電解液に浸される第一の電解電極を有し、前記第一の電解電極間に電圧を印加することによって水素と酸素を発生させる第一の水電解装置と、
    　前記第一の電解液よりも導電性の低い第二の電解液に浸される第二の電解電極を有し、前記第二の電解電極間に電圧を印加することによって水素を発生させる第二の水電解装置と、
    　前記第一の水電解装置から発生する酸素中の水素濃度の上昇を抑制するように、系外の電源から供給される電力に応じて、前記第一の水電解装置及び前記第二の水電解装置への供給電力を制御する制御手段と、を備える、
    　水電解システム。     A first water electrolysis device that has a first electrolytic electrode immersed in a first electrolytic solution and generates hydrogen and oxygen by applying a voltage between the first electrolytic electrodes,
    A second electrolytic electrode having a second electrolytic electrode immersed in a second electrolytic solution having a lower conductivity than the first electrolytic solution, and generating a hydrogen by applying a voltage between the second electrolytic electrodes. Water electrolysis device,
    The first water electrolysis device and the second water electrolysis according to electric power supplied from a power supply outside the system so as to suppress an increase in the concentration of hydrogen in oxygen generated from the first water electrolysis device. Control means for controlling the power supplied to the device,
    Water electrolysis system.
  2. 　前記第一の水電解装置は、前記第一の電解液がアルカリ水溶液を含むアルカリ型水電解装置であって、
    　前記制御手段は、前記電源から供給される電力が、所定の閾値以下である場合に、前記電力を前記第一の水電解装置へ供給することを停止する、
    　請求項１に記載の水電解システム。     The first water electrolysis apparatus is an alkaline water electrolysis apparatus in which the first electrolyte contains an aqueous alkaline solution,
    The control means, when the power supplied from the power supply is equal to or less than a predetermined threshold, stops supplying the power to the first water electrolysis device,
    The water electrolysis system according to claim 1.
  3. 　前記所定の閾値は、前記第一の水電解装置から発生する酸素中の水素濃度を急激に上昇させる電力である、
    　請求項２に記載の水電解システム。     The predetermined threshold value is power for rapidly increasing the hydrogen concentration in oxygen generated from the first water electrolysis device,
    The water electrolysis system according to claim 2.
  4. 　前記所定の閾値は、前記第一の水電解装置の運転を回避する濃度の水素を含む酸素を発生させる電力である、
    　請求項２または３に記載の水電解システム。     The predetermined threshold is power for generating oxygen containing hydrogen at a concentration that avoids operation of the first water electrolysis device,
    The water electrolysis system according to claim 2.
  5. 　前記所定の閾値は、前記第一の水電解装置の定格電流の４０％の電流を前記第一の水電解装置へ流すことのできる値である、
    　請求項２に記載の水電解システム。     The predetermined threshold value is a value that allows a current of 40% of the rated current of the first water electrolysis device to flow through the first water electrolysis device.
    The water electrolysis system according to claim 2.
  6. 　前記第二の水電解装置は、
    　　高分子を含む電解質を含み、
    　　前記第一の電解液よりも導電性の低い第二の電解液に浸される第二の電解電極が、前記電解質を挟んで設けられ、
    　　前記第二の電解電極間に電圧を印加することによって水素を発生させる、高分子型水電解装置である、
    　請求項１から５のうち何れか１項に記載の水電解システム。     The second water electrolysis device,
    Including an electrolyte containing a polymer,
    A second electrolytic electrode immersed in a second electrolytic solution having a lower conductivity than the first electrolytic solution is provided with the electrolyte interposed therebetween,
    Generating hydrogen by applying a voltage between the second electrolytic electrodes, a polymer water electrolysis device,
    The water electrolysis system according to any one of claims 1 to 5.
  7. 　前記制御手段は、前記第一の水電解装置および前記第二の水電解装置に供給する電力を、前記第一の水電解装置から発生する酸素に含まれる水素の濃度に応じて制御する、
    　請求項１から６のうち何れか１項に記載の水電解システム。     The control unit controls the power supplied to the first water electrolysis device and the second water electrolysis device according to the concentration of hydrogen contained in oxygen generated from the first water electrolysis device,
    The water electrolysis system according to any one of claims 1 to 6.
  8. 　前記制御手段は、前記電源と接続する水電解装置を前記第一の水電解装置と前記第二の水電解装置との間で切り替える切り替え手段を備える、
    　請求項１から７のうち何れか１項に記載の水電解システム。     The control unit includes a switching unit that switches a water electrolysis device connected to the power supply between the first water electrolysis device and the second water electrolysis device,
    The water electrolysis system according to claim 1.
  9. 　前記制御手段は、
    　前記第一の水電解装置への前記電力の供給が停止した状態において、
    　前記第一の水電解装置から発生する酸素に含まれる水素の濃度が第一の濃度以下である場合に、
    　　前記電源から供給される電力が第一の運転開始閾値よりも大きくなると、前記第一の水電解装置に対して前記電力の供給を再開し、
    　前記第一の水電解装置から発生する酸素に含まれる水素の濃度が第一の濃度より大きい場合には、
    　　前記電源から供給される電力が前記第一の運転開始閾値よりも大きくなっても、前記第一の水電解装置に対して前記電力の供給を再開せず、
    　　前記電源から供給される電力が前記第一の運転開始閾値よりも大きな第二の運転開始閾値よりも大きくなると、前記第一の水電解装置に対して前記電力の供給を再開する、
    　請求項２から８のうち何れか１項に記載の水電解システム。     The control means includes:
    In a state where the supply of the power to the first water electrolysis device is stopped,
    When the concentration of hydrogen contained in oxygen generated from the first water electrolysis device is not more than the first concentration,
    When the power supplied from the power supply is larger than a first operation start threshold, the supply of the power to the first water electrolysis device is restarted,
    When the concentration of hydrogen contained in oxygen generated from the first water electrolysis device is higher than the first concentration,
    Even if the power supplied from the power supply is larger than the first operation start threshold, the supply of the power to the first water electrolysis device is not restarted,
    When the power supplied from the power supply is larger than a second operation start threshold larger than the first operation start threshold, the supply of the electric power to the first water electrolysis device is restarted,
    The water electrolysis system according to any one of claims 2 to 8.
  10. 　前記制御手段は、前記第一の水電解装置から発生する酸素に含まれる水素の濃度に応じて前記所定の閾値を変更する、
    　請求項２から５のうち何れか１項に記載の水電解システム。     The control means changes the predetermined threshold value according to the concentration of hydrogen contained in oxygen generated from the first water electrolysis device,
    The water electrolysis system according to any one of claims 2 to 5.
  11. 　第一の電解液に浸される第一の電解電極を有し、前記第一の電解電極間に電圧を印加することによって水素と酸素を発生させる第一の水電解装置と、前記第一の電解液よりも導電性の低い第二の電解液に浸される第二の電解電極を有し、前記第二の電解電極間に電圧を印加することによって水素を発生させる第二の水電解装置と、への系外の電源から供給される電力の配分を、系外の電源から供給される電力に応じて、前記第一の水電解装置から発生する酸素中の水素濃度の上昇を抑制するように制御する制御ステップを備える、
    　水電解方法。     A first water electrolysis device having a first electrolytic electrode immersed in a first electrolytic solution, and generating hydrogen and oxygen by applying a voltage between the first electrolytic electrodes; and A second water electrolysis device having a second electrolytic electrode immersed in a second electrolytic solution having lower conductivity than the electrolytic solution and generating hydrogen by applying a voltage between the second electrolytic electrodes And the distribution of the electric power supplied from the external power supply to the power supply apparatus according to the electric power supplied from the external power supply to suppress an increase in the hydrogen concentration in oxygen generated from the first water electrolysis device. Comprising a control step of controlling
    Water electrolysis method.
PCT/JP2019/010939 2018-07-06 2019-03-15 Water electrolysis system and water electrolysis method WO2020008687A1 (en)

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