WO2014103101A1 - 燃料電池システム及び燃料電池システムにおける燃料電池の発電性能回復方法 - Google Patents
燃料電池システム及び燃料電池システムにおける燃料電池の発電性能回復方法 Download PDFInfo
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- WO2014103101A1 WO2014103101A1 PCT/JP2013/005236 JP2013005236W WO2014103101A1 WO 2014103101 A1 WO2014103101 A1 WO 2014103101A1 JP 2013005236 W JP2013005236 W JP 2013005236W WO 2014103101 A1 WO2014103101 A1 WO 2014103101A1
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- oxidant gas
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
- H01M8/04225—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells during start-up
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
- H01M8/04228—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells during shut-down
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04291—Arrangements for managing water in solid electrolyte fuel cell systems
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
- H01M8/04302—Processes for controlling fuel cells or fuel cell systems applied during specific periods applied during start-up
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
- H01M8/04303—Processes for controlling fuel cells or fuel cell systems applied during specific periods applied during shut-down
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
- H01M8/0432—Temperature; Ambient temperature
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
- H01M8/04537—Electric variables
- H01M8/04544—Voltage
- H01M8/04552—Voltage of the individual fuel cell
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
- H01M8/04537—Electric variables
- H01M8/04544—Voltage
- H01M8/04559—Voltage of fuel cell stacks
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
- H01M8/04746—Pressure; Flow
- H01M8/04753—Pressure; Flow of fuel cell reactants
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M2008/1095—Fuel cells with polymeric electrolytes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
- H01M8/04238—Depolarisation
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- 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
- Y02E60/50—Fuel cells
Definitions
- the present invention relates to a fuel cell system, and more particularly to a technique for recovering power generation performance in the fuel cell system.
- a catalyst activity recovery means is provided for recovering the catalyst activity of the electrode catalyst in the electrode catalyst layer by passing a large current through the fuel cell and increasing the amount of water discharged from the catalyst layer to a predetermined amount or more.
- a fuel cell is known (Patent Document 1).
- This fuel cell has a problem that a large amount of fuel is consumed in order to pass a large current to recover the catalytic activity.
- impurities such as sulfate ions (SO 4 2 ⁇ ) or hydrogen sulfate ions (HSO 4 1 ⁇ ) generated from impurities in the air or decomposed by ionomers in the catalyst layer adhere to the electrode catalyst, the catalyst It has been found that only water discharged from the bed cannot sufficiently remove impurities.
- sulfate ions and hydrogen sulfate ions are collectively referred to as “sulfate ions”.
- the present invention has been made to solve at least a part of the problems described above, and can be realized as the following forms.
- a fuel cell system includes a fuel cell having a catalyst, a fuel gas supply unit that supplies a fuel gas to the fuel cell, an oxidant gas supply unit that supplies an oxidant gas to the fuel cell, and a supply of the fuel gas And a control unit that controls the supply and stop of the oxidant gas, and the power generation of the fuel cell, and the control unit stops the supply of the oxidant gas to the fuel cell.
- the oxidant gas to the fuel cell after the voltage generated by the fuel cell is lowered to a predetermined first value or less and the temperature of the fuel cell becomes a predetermined second value or less.
- the fuel cell voltage is recovered by restarting the supply of the fuel cell and restarting the fuel cell to generate power and generating water.
- the fuel cell system of this aspect by reducing the voltage generated by the fuel cell to be equal to or lower than the first value, the impurities are liberated from the catalyst, and the fuel cell is restarted at a temperature equal to or lower than the second value. A large amount of liquid water is generated. And it becomes possible to recover the power generation performance of the fuel cell system by discharging impurities released from the catalyst with this large amount of liquid water out of the stack.
- the first value may be a positive value of 0.6 V or less.
- the voltage generated by the fuel cell exceeds 0V and is equal to or less than 0.6V, so that impurities can be easily released from the catalyst.
- the oxidant gas of the fuel cell flows in the distribution of the produced water generated by the reaction of the fuel cell after the fuel cell is regenerated.
- the control unit may perform re-power generation of the fuel cell so that an amount corresponding to a relative humidity of 200% or more is obtained at the center of the agent gas flow path.
- the generated water corresponding to the relative humidity of 200% or more is condensed and becomes a large amount of liquid water, so that impurities can flow out using this large amount of liquid water. .
- the time for holding the voltage below the first value may be 10 minutes or more. According to the fuel cell system of this embodiment, since the time for setting the voltage to be equal to or lower than the first value is 10 minutes or longer, the time for releasing impurities from the catalyst can be lengthened, and the power generation performance of the fuel cell system can be recovered. Become.
- the second value may be a value of room temperature to 40 ° C.
- the relative humidity increases as the temperature decreases. According to the fuel cell system of this aspect, an increase in relative humidity due to a decrease in temperature and an increase in humidity due to generated water can be combined to make it easy for condensation to occur at a relative humidity of 200% or more.
- control unit may re power the fuel cell at a current density of 0.1 A / cm 2 or more 0.2 A / cm 2 or less of the current.
- the fuel cell is regenerated at a current density of 0.2 A / cm 2 or less, so that fuel efficiency can be improved.
- the fuel cell system further includes a back pressure adjusting unit that adjusts the back pressure of the oxidant gas at the outlet of the fuel cell, and the control unit has a back pressure of 140 kPa ( abs) or more and 200 kPa (abs) or less.
- the back pressure since the back pressure is controlled to be 140 kPa (abs) or more at the time of re-power generation, the relative humidity can be set to 200% or more to facilitate condensation.
- the oxidant gas supply unit needs to supply the oxidant gas to the fuel cell at a high pressure. Absent.
- a method for recovering power generation performance in a fuel cell system is provided.
- the step of stopping the supply of oxidant gas to the fuel cell, the voltage generated by the fuel cell is lowered to a predetermined first value or less, and the temperature of the fuel cell is predetermined.
- the supply of the oxidant gas to the fuel cell is restarted, the fuel cell restarts power generation to generate water, and the water is used to generate the water. Removing impurities adhering to the catalyst.
- the impurities are liberated from the catalyst by lowering the voltage generated by the fuel cell below the first value, and the fuel cell is restarted at a temperature below the second value.
- the fuel cell is restarted at a temperature below the second value.
- the present invention can be realized in various forms, for example, in the form of a method for recovering power generation performance in a fuel cell system, a method for releasing impurities from a catalyst in a fuel cell, in addition to a fuel cell system. be able to.
- FIG. 4 is a graph showing a relationship between a current density and a voltage recovery amount of a power generation unit of the fuel cell 10 in a startup simulation evaluation process. It is a graph which shows the relationship between the back pressure of an oxidizing agent electrode and the amount of voltage recovery in a starting simulation evaluation process. It is explanatory drawing explaining the relationship between the back pressure of an oxidizing agent, and the area satisfy
- FIG. 1 is an explanatory diagram showing a configuration of a fuel cell system according to an embodiment of the present invention.
- the fuel cell system 20 includes a fuel cell 10, a fuel tank 300, an air pump 400, a cooling water pump 500, a load 600, and a control unit 700.
- the fuel cell 10 includes a fuel cell stack 100, current collector plates 200 and 201, insulating plates 210 and 211, end plates 230 and 231, a tension rod 240, and a nut 250.
- the fuel cell stack 100 includes a plurality of power generation units 110. Each power generation unit 110 is a single cell. The power generation units 110 are stacked and connected in series to form the fuel cell stack 100, and generate a high voltage. The current collector plates 200 and 201 are disposed on both sides of the fuel cell stack 100, and are used to extract the voltage and current generated by the fuel cell stack 100 to the outside of the fuel cell stack 100. The voltage and current generated by the fuel cell stack 100 are supplied to the load 600.
- the load 600 includes additional devices such as a motor of a fuel cell vehicle and an air conditioner.
- the insulating plates 210 and 211 are disposed further outside the current collecting plates 200 and 201, respectively, and between the current collecting plates 200 and 201 and other members such as the end plates 230 and 231 and the tension rod 240. Insulate so that no current flows.
- End plates 230 and 231 are disposed on the outer sides of the insulating plates 210 and 211, respectively.
- the end plate 231 is disposed at a predetermined distance from the end plate 230 by the tension rod 240 and the nut 250.
- the fuel tank 300 is connected to the fuel cell 10 by a fuel gas supply pipe 310.
- the fuel gas supply pipe 310 is provided with a valve 320 for adjusting the flow rate of the fuel gas.
- a fuel gas exhaust pipe 330 is connected to the downstream side of the fuel cell 10, and a fuel gas exhaust valve 340 and a pressure gauge 350 are arranged in the fuel gas exhaust pipe 330.
- the fuel gas exhaust valve 340 adjusts the back pressure of the fuel exhaust gas.
- the fuel gas exhaust pipe 330 is connected to the fuel gas supply pipe 310 by a fuel gas recovery pipe 360.
- the fuel gas recovery pipe 360 is provided with a pump 370 for sending the fuel exhaust gas to the fuel gas supply pipe 310.
- hydrogen gas is used as the fuel gas.
- the air pump 400 is connected to the fuel cell 10 by an oxidant gas supply pipe 410.
- the oxidant gas supply pipe 410 is provided with a valve 420 for adjusting the flow rate of the oxidant gas.
- An oxidant gas exhaust pipe 430 is connected to the downstream side of the fuel cell 10, and an oxidant gas exhaust valve 440 and a pressure gauge 450 are arranged in the oxidant gas exhaust pipe 430.
- the oxidant gas exhaust valve 440 adjusts the back pressure of the oxidant exhaust gas. For example, air is used as the oxidizing gas.
- the cooling water pump 500 is connected to the fuel cell 10 by a cooling water pipe 510.
- the cooling water pipe 510 is provided with a radiator 520 and a thermometer 530.
- the radiator 520 cools the cooling water discharged from the fuel cell 10.
- the thermometer 530 measures the temperature of the cooling water discharged from the fuel cell 10.
- the control unit 700 opens and closes the valves 320 and 420, the fuel gas exhaust valve 340, and the oxidant gas exhaust valve 440 based on the power generation amount of the fuel cell 10, the power consumption amount in the load 600, the temperature of the fuel cell 10, and the back pressure. In addition, the opening degree thereof is controlled, and the operation of the fuel cell 10 is controlled.
- FIG. 2 is an explanatory diagram schematically showing the configuration of the power generation unit 110.
- the power generation unit 110 includes a membrane electrode assembly 120, gas diffusion layers 132 and 133, porous body gas flow paths 142 and 143, separator plates 152 and 153, and a seal gasket 160.
- the membrane electrode assembly 120 includes an electrolyte membrane 121 and catalyst layers 122 and 123.
- the catalyst layer 122 functions as a fuel electrode
- the catalyst layer 123 functions as an oxidant electrode. Therefore, the catalyst layer 122 is also called an anode catalyst layer 122 or a fuel electrode 122, and the catalyst layer 123 is also called a cathode catalyst layer 123 or an oxidant electrode 123.
- the power generation unit 110 is configured as a solid polymer fuel cell.
- the electrolyte membrane 121 for example, a proton conductive ion exchange membrane made of a fluorine resin such as perfluorocarbon sulfonic acid polymer or a hydrocarbon resin is used.
- the catalyst layers 122 and 123 are formed on each surface of the electrolyte membrane 121, respectively.
- the catalyst layers 122 and 123 are formed of, for example, a platinum catalyst or catalyst-carrying particles (for example, carbon particles) that carry a platinum alloy catalyst made of platinum and another metal and an electrolyte (ionomer).
- Nafion registered trademark
- DuPont is used as a perfluorocarbon sulfonic acid polymer or an ionomer.
- the gas diffusion layers 132 and 133 are disposed on the outer surfaces of the catalyst layers 122 and 123, respectively.
- carbon cloth or carbon paper using a carbon nonwoven fabric can be used as the gas diffusion layers 132 and 133.
- the porous gas channels 142 and 143 are disposed on the outer surfaces of the gas diffusion layers 132 and 133, respectively.
- Separator plates 152 and 153 are disposed on the outer surfaces of porous gas flow paths 142 and 143, respectively.
- a cooling water channel 155 is formed between the separator plate 152 and the separator plate 153 of the adjacent power generation unit 110.
- the seal gasket 160 is formed so as to surround the outer edges of the membrane electrode assembly 120, the gas diffusion layers 132 and 133, and the porous body gas flow paths 142 and 143.
- the seal gasket 160 is formed integrally with the membrane electrode assembly 120 by, for example, injection molding. Thereafter, gas diffusion layers 132 and 133 and porous body gas flow paths 142 and 143 are sequentially disposed on both surfaces of the membrane electrode assembly 120.
- FIG. 3 is an explanatory diagram showing a cycle of a voltage recovery simulation test of the fuel cell system.
- One cycle of the voltage recovery simulation test includes a generation potential fluctuation endurance process, an IV characteristic evaluation process (1), a stop simulation evaluation process, a stop state simulation evaluation process, a start simulation evaluation process, and an IV characteristic evaluation process (2 ) And have.
- Next to the IV characteristic evaluation step (2) is a generation potential fluctuation endurance step of the next cycle.
- the control unit 700 first executes a generated potential fluctuation endurance process.
- the control unit 700 supplies hydrogen to the fuel electrode 122 of the fuel cell 10 and supplies air to the oxidant electrode 123.
- the controller 700 sets the temperature of the fuel cell 10 to 70 ° C., and sets the voltage of the oxidizer electrode 123 to the fuel electrode 122 of the power generation unit 110 of the fuel cell 10 (hereinafter referred to as “cell voltage”) to 0.
- the first cycle of power generation at 0.9 V and the second cycle of power generation at a cell voltage of 0.6 V are alternately performed.
- Such voltage variation between two voltages alternately is also referred to as rectangular wave potential variation.
- the control unit 700 sets the temperature of the fuel cell 10 to 65 ° C., draws a predetermined current from the power generation unit 110 of the fuel cell 10, and oxidizes the fuel electrode 122 of the power generation unit 110. The voltage of the agent electrode 123 was measured. At this time, the controller 700 gradually decreased the current drawn from the power generation unit 110 of the fuel cell 10 from 2.4 A / cm 2 to 0 A / cm 2 .
- control unit 700 lowered the temperature of the fuel cell 10 from 65 ° C. to 35 ° C. in 10 minutes while generating power at the current 0.05 A / cm 2 .
- the control unit 700 stopped supplying air at a temperature of 35 ° C. of the fuel cell 10 and stopped supplying hydrogen after stopping the supply of air.
- the control unit 700 stops the supply of hydrogen after stopping the supply of air, but may continue to supply without stopping the supply of hydrogen after stopping the supply of air. Thereafter, the control unit 700 kept the temperature of the fuel cell 10 at 35 ° C.
- the control unit 700 supplies hydrogen to the fuel electrode 122 of the fuel cell 10 and supplies dry air to the oxidant electrode 123 to resume power generation.
- the control unit 700 sets the current from the power generation unit 110 of the fuel cell 10 at this time to 0.2 A / cm 2 and raises the temperature of the fuel cell 10 from 35 ° C. to 60 ° C. in 5 minutes.
- the controller 700 sets the temperature of the fuel cell 10 to 65 ° C. and draws a predetermined current from the power generation unit 110 of the fuel cell 10. Then, the voltage of the fuel cell 10 was measured. At this time, the controller 700 gradually reduced the current drawn from the power generation unit 110 of the fuel cell 10 from 2.4 A / cm 2 to 0 A / cm 2 , as in the IV characteristic evaluation step (1).
- FIG. 4 is a graph showing the results of IV characteristic evaluation.
- the horizontal axis is the current drawn from the power generation unit 110 of the fuel cell 10, and the vertical axis is the cell voltage of the fuel cell 10. Since hydrogen gas is supplied to the fuel electrode, the cell voltage is equal to (oxidant electrode potential vs. RHE).
- RHE reversible hydrogen electrode
- RHE means a hydrogen electrode (reversible hydrogen electrode) using an electrolyte solution having the same pH value as that of the solution containing the electrode to be measured.
- aH + in other words, pH
- the electrode potentials of the reversible hydrogen electrode (RHE) and the standard hydrogen electrode (SHE) do not match.
- the same electrolyte as that used in the catalyst layer to be measured can be used, there is an advantage that there is no need to consider the potential difference between the liquids.
- the cell potential is the potential of the oxidant electrode 123 with respect to the fuel electrode 122, it is experimentally convenient to use the fuel electrode 122 as a reversible hydrogen electrode in the fuel cell.
- the control unit 700 gradually reduces the current drawn from the power generation unit 110 of the fuel cell 10 from 2.4 A / cm 2 to 0 A / cm 2 .
- the cell voltage in the IV characteristic evaluation step (2) is greater than the cell voltage in the IV characteristic evaluation step (1). Is also 5-20 mV larger.
- the cell voltage in the IV characteristic evaluation step (2) is higher than the cell voltage in the IV characteristic evaluation step (1), and the cell voltage is recovered correspondingly. That is, the difference portion between the cell voltage in the IV characteristic evaluation step (2) and the cell voltage in the IV characteristic evaluation step (1) is not recovered only by setting the oxidizer electrode 123 to a low potential.
- the potential of the oxidizer electrode 123 is 0.3 Vvs. When it becomes RHE or less, the oxide film of the oxidizer electrode 123 is removed.
- the cell voltage becomes 0.3 V or less, and the oxidizing agent Since the oxide film on the electrode 123 is considered to be removed, it is considered that a reversible (recoverable) voltage drop in the IV characteristic evaluation step (1) is caused by factors other than the oxide film on the oxidant electrode 123. It is done.
- FIG. 5 is a graph showing the relationship between the stop time and the cell voltage in the stop state simulation process.
- the horizontal axis is the stop time in the stop state simulation process
- the vertical axis is the cell voltage of the power generation unit 110.
- OCV open circuit voltage
- FIG. 6 is an explanatory diagram showing the relationship between the stop state simulation time and the voltage recovery amount.
- the voltage recovery amount V3 is calculated using the following equation (2).
- V1 is a generated voltage when the current is subtracted at 2.0 A / cm 2 in the IV characteristic evaluation step (this generated voltage is a value after IR correction is performed.
- the IR correction means correction for excluding the influence of the internal resistance R of the power generation unit 110.
- V2 is a current of 2.0 A / cm 2 in the IV characteristic evaluation step (2). This is the generated voltage when subtracted by.
- V3 V2-V1 (2)
- FIG. 7 is a graph showing changes in cell voltage in the startup simulation evaluation process.
- the horizontal axis is the elapsed time in the startup simulation evaluation process, and the vertical axis is the cell voltage of the power generation unit 110.
- the control unit 700 sets the stoichiometric ratio of the oxidant electrode 123 to 1.5, the back pressure of the oxidant electrode 123 to 140 kPa (abs), and the pressure of the inlet of the oxidant electrode 123 to 150 kPa (abs) (back Pressure +10 kPa (abs)), and the current drawn from the power generation unit 110 of the fuel cell 10 was 0.2 A / cm 2 .
- the stoichiometric ratio means a value obtained by dividing the actual supply amount of the reaction gas (fuel gas or oxidant gas) by the theoretical amount of the reaction gas necessary for power generation.
- the cell voltage immediately after the start simulation evaluation started was about 0.8 V, the cell voltage slightly decreased with the passage of time, and the cell voltage decreased to about 0.78 V after 350 seconds. However, the cell voltage did not drop significantly from 0.8V.
- the control unit 700 first sets the voltage of the oxidizer electrode 123 to 0.8 V (voltage at 1 minute in FIG. 5), and then changes the cell voltage to This is a result of performing power generation with a large amount of generated water (running water) by setting the current drawn from the power generation unit 110 of the fuel cell 10 to about 0.8 V and 0.2 A / cm 2 .
- the control unit 700 first sets the voltage of the oxidizer electrode 123 to 0.1 V (the voltage at 10 minutes in FIG.
- the perfluorocarbon sulfonic acid polymer for example, Nafion
- the electrolyte membrane 121 or the Nafion used as the electrolyte of the fuel electrode 122 and the oxidant electrode 123 is used.
- system ionomers chemically degrade to produce sulfate ions and hydrogen sulfate ions (sulfate ions, etc.).
- sulfate ions and the like are adsorbed and poisoned by platinum (pt) used for the oxidant electrode 123 to reduce the power generation performance of the fuel cell.
- the applicant of the present application considered adsorption poisoning of sulfate ions or the like to Pt as a cause of a decrease in the power generation performance of the fuel cell after the power generation potential fluctuation durability process.
- the applicant of the present application sets the cell temperature of the fuel cell 10 to 70 ° C. after the generation potential fluctuation endurance process, supplies hydrogen gas having a dew point temperature of 70 ° C. to the fuel electrode 122 at 1 NL / min, and nitrogen gas having a dew point temperature of 70 ° C. to 2 NL.
- a hydrogen / nitrogen purge to be supplied to the oxidant electrode 123 at a rate of / min was performed.
- sulfate ions and the like were detected in the waste water drained from the oxidizer electrode 123, and it was confirmed that the cell voltage of the IV characteristic after the hydrogen / nitrogen purge was recovered.
- FIG. 8 is a graph showing the relationship between the potential of the oxidizer electrode and the amount of adsorption of sulfate ions or the like on the Pt electrode.
- This graph shows the scale of the horizontal axis of Figure 6 of A. Kolics and A. Wieckowski J. Phys. Chem. B 2001, 105, 2588-2595 from the silver / silver chloride electrode standard to the reversible hydrogen electrode standard (vs. RHE). It is a graph changed to.
- the numerical value of the voltage on the basis of the reversible hydrogen electrode is equal to the cell voltage that is the value of the voltage of the oxidant electrode 123 with respect to the fuel electrode 122. Therefore, the horizontal axis may be referred to as the cell voltage.
- the cell voltage when the cell voltage is 0.0 V or more and 0.7 V or less, the amount of adsorption of sulfate ions or the like to Pt decreases. In other words, by setting the cell voltage to 0.7 V or less, sulfate ions and the like can be released from the Pt electrode.
- the cell voltage is preferably 0.6 V or less, and more preferably 0.3 V or less.
- a history of lowering the voltage of the oxidizer electrode 123 is given to release sulfate ions and the like from the Pt electrode.
- a large amount of liquid water is generated by generating a large amount of flowing water with the voltage of the oxidizer electrode 123 set to a high voltage (0.8 V).
- the cell voltage of the power generation unit 110 of the fuel cell 10 can be recovered by discharging sulfate ions and the like released from the Pt electrode from the oxidizer electrode 123 using this large amount of liquid water.
- FIG. 9 is an explanatory diagram schematically showing a mechanism for discharging sulfate ions and the like in the present embodiment.
- the control unit 700 executes the power generation potential fluctuation endurance process, as shown in the process (a), sulfate ions or the like are adsorbed and poisoned by Pt, and the cell voltage of the power generation unit 110 (FIG. 1) of the fuel cell 10 decreases. To do.
- step (b) when the controller 700 stops supplying the oxidant (air) to the oxidant electrode 123 and two minutes or more have elapsed, the power generation unit 110 of the fuel cell 10 is shown in FIG. Cell voltage drops to 0.6V or less.
- step (c) the control unit 700 resumes the supply of the oxidant (air) to the oxidant electrode 123, draws the power generation unit 110 of the fuel cell 10 with a current of 0.2 A / cm 2 , Generate liquid water. And the control part 700 discharge
- the control unit 700 stops supplying the oxidant (air) to the oxidant electrode 123 and gives a history of setting the potential of the oxidant electrode to 0.6 or less. . Thereafter, the control unit 700 draws the power generation unit 110 of the fuel cell 10 with a current of 0.2 A / cm 2 to generate a large amount of liquid water. And the control part 700 can discharge
- FIG. 10 is a graph showing the relationship between the current density in the startup simulation evaluation process and the voltage recovery amount of the power generation unit 110 of the fuel cell 10.
- the voltage recovery amount was compared for two cases where the current density was 0.2 A / cm 2 and 0.05 A / cm 2 .
- the same values as those in the first example were used for parameters other than the current density in power generation in the startup simulation evaluation process.
- the voltage recovery amount averaged about 0.05 mV
- the voltage recovery amount averaged 17.5 mV. It was about.
- the amount of generated water in the startup simulation evaluation process is proportional to the current density.
- the voltage can be recovered when the controller 700 draws a current with a current density of 0.05 A / cm 2 to 0.2 A / cm 2 . Moreover, if the current density in the startup simulation evaluation process is high, the voltage is likely to recover. However, too high a current density, since the fuel consumption is deteriorated, the control unit 700 from the viewpoint of fuel economy, subtracting the current current density by the magnitude of 0.1A / cm 2 ⁇ 0.2A / cm 2 Is more preferable.
- FIG. 11 is a graph showing the relationship between the back pressure of the oxidant electrode and the voltage recovery amount in the startup simulation evaluation step.
- the voltage recovery amount was compared in two cases where the back pressure of air (oxidant gas) was 140 kPa (abs) and 200 kPa (abs).
- the inlet pressure of the power generation unit 110 of the fuel cell 10 is set to back pressure + 10 kPa (abs).
- the same values as those in the first embodiment are used for parameters other than the back pressure and the inlet pressure in power generation in the oxidant gas supply start simulation evaluation step.
- FIG. 12 is an explanatory diagram for explaining the relationship between the back pressure of the oxidizing agent and the area filled with liquid water.
- FIG. 12 schematically shows the power generation unit 110, where the left side of FIG. 12 is the inlet side of the oxidant electrode 123, and the right side is the outlet side of the oxidant electrode 123.
- the generated water generated by power generation moves from left to right by the flow of the oxidant gas.
- the region (A) on the left side of FIG. 12 the amount of generated water generated by power generation is small.
- the liquid water flow amount integrated value means a value obtained by integrating the amount of generated water generated upstream of the point.
- the pressure pressure in the power generation unit 110
- the distribution of liquid water in the region (A) on the left side of FIG. 12, the pressure is high but the amount of generated water is small. It is difficult to become liquid water and the amount of liquid water is small.
- the pressure is about the back pressure, but the amount of generated water is large, so that the generated water easily becomes liquid water, and the amount of liquid water is large.
- the back pressure increases to 200 kPa (abs)
- the high pressure range spreads to the left side, so that the generated water easily becomes liquid water even in the region (B) near the center in FIG.
- the area filled with liquid water increases when the back pressure is 200 kPa (abs) compared to when the back pressure is 140 kPa (abs).
- the control unit 700 sets the back pressure to 140 kPa (abs) to 200 kPa (abs), so that the power generation unit 110 of the fuel cell 10 is filled with liquid water. Can be increased.
- the pressure at the inlet of the power generation unit 110 is increased depending on the back pressure.
- the output of the air pump 400 (FIG. 1) is increased.
- the back pressure may be 200 kPa (abs) or less.
- FIG. 13 is an explanatory diagram showing the relationship between the temperature (cell temperature) of the power generation unit 110 of the fuel cell 10 and the relative humidity at the outlet of the power generation unit 110 in the startup simulation evaluation step.
- the results of the fourth to seventh examples are calculated values assuming that power is generated uniformly in the plane and there is no movement of water between the anode and the cathode.
- the horizontal axis is the cell temperature
- the vertical axis is the relative humidity at the outlet of the power generation unit 110.
- the relative humidity at the outlet of the power generation unit 110 was compared by changing the cell temperature.
- the stoichiometric ratio of the oxidant gas is 2.0
- the back pressure of the oxidant gas is 100 kPa (abs)
- the relative humidity at the outlet of the power generation unit 110 was increased.
- the absolute water vapor pressure is proportional to the liquid water flow rate integrated value.
- the control unit 700 can reduce the cell temperature to increase the amount of liquid water, facilitate the flow of sulfate ions and the like, and facilitate the recovery of the voltage of the power generation unit 110.
- the cell temperature is the same at both the inlet and outlet of the power generation unit 110. If the power generation amount per unit area does not change at any position of the power generation unit 110, the amount of generated water per unit area does not change at any position of the power generation unit 110.
- the cell temperature is 45 ° C.
- the relative humidity at the outlet of the power generation unit 110 is 200%.
- the relative humidity becomes 100% at the center of the power generation unit 110, and the downstream side from the substantially center of the power generation unit 110 is filled with liquid water.
- the cell temperature is 40 ° C.
- the relative humidity at the outlet of the power generation unit 110 is 260%. Therefore, in order to fill the downstream side from the substantially center of the power generation unit 110 with liquid water, the cell temperature may be 45 ° C. or lower, and more preferably 40 ° C. or lower.
- the control unit 700 sets the cell temperature in the startup simulation evaluation process to room temperature (25 ° C.) or higher and 45 ° C. or lower, so that the downstream side from the substantially center of the power generation unit 110 is liquid water. It is possible to increase the amount of liquid water, to facilitate the flow of sulfate ions and the like, and to easily recover the voltage of the power generation unit 110.
- the cell temperature may be 25 ° C. or higher and 40 ° C. or lower.
- the power generation unit can be filled with liquid water more.
- FIG. 14 is an explanatory diagram showing the relationship between the current density in the startup simulation evaluation process and the relative humidity at the outlet of the power generation unit 110.
- the horizontal axis is the current density of the current drawn from the power generation unit 110 of the fuel cell 10
- the vertical axis is the relative humidity at the outlet of the power generation unit 110.
- the stoichiometric ratio of the oxidant gas is 2.0
- the back pressure of the oxidant gas is 100 kPa (abs)
- the current density of the current drawn from the power generation unit 110 of the fuel cell 10 in the startup simulation evaluation process Is 0.2 A / cm 2 . From the results shown in FIG.
- the current density may be any of 0.05 A / cm 2 to 0.5 A / cm 2 .
- the amount of power generation can be increased, and the liquid water flowing water integrated value can be increased. Therefore, when the current density is increased, free sulfate ions and the like can be quickly discharged.
- FIG. 15 is an explanatory diagram showing the relationship between the stoichiometric ratio of the oxidant gas and the relative humidity at the outlet of the power generation unit 110 in the startup simulation evaluation process.
- the horizontal axis is the position in the power generation unit 110, the left end is the oxidant gas inlet in the power generation unit 110, and the right end is the oxidant gas outlet in the power generation unit.
- the vertical axis is relative humidity.
- the cell temperature is 35 ° C.
- the back pressure of the oxidant gas is 100 kPa (abs)
- the current density of the current drawn from the power generation unit 110 of the fuel cell 10 in the startup simulation evaluation process is 0.2 A / cm 2 .
- an oxidant gas containing almost no moisture was used with the dew point of the oxidant gas set to -40 ° C.
- the flow rate of the dried oxidant gas is decreased, so that the relative humidity at the outlet of the power generation unit 110 can be increased.
- the power generation unit 110 is filled with liquid water in a region where the relative humidity is 200% or more
- the stoichiometric ratio is 2.0
- a region of about 45% downstream is filled with liquid water
- the stoichiometric ratio is In the case of 1.2
- about 55% of the downstream area is filled with liquid water. Therefore, if the stoichiometric ratio is reduced, the area where sulfate ions and the like can be discharged can be increased.
- the controller 700 is more likely to fill the power generation unit 110 with liquid water when the stoichiometric ratio of the oxidant gas in the startup simulation evaluation process is reduced.
- FIG. 16 is an explanatory diagram showing the relationship between the back pressure of the oxidant gas and the relative humidity at the outlet of the power generation unit 110 in the startup simulation evaluation step.
- the horizontal axis is the position in the power generation unit 110, the left end is the oxidant gas inlet in the power generation unit 110, and the right end is the oxidant gas outlet in the power generation unit.
- the vertical axis is relative humidity.
- the cell temperature is 35 ° C.
- the oxidant gas stoichiometric ratio is 2.0
- the current density of the current drawn from the power generation unit 110 of the fuel cell 10 in the startup simulation evaluation process is 0.2 A / cm 2. Yes.
- an oxidant gas containing almost no moisture was used with the dew point of the oxidant gas set to -40 ° C.
- the power generation unit 110 is filled with liquid water in a region where the relative humidity is 200% or more.
- an intersection of a line with a back pressure of 200 kPa (abs) and a line with a relative humidity of 200% is defined as P1.
- the region from the inlet to P1 (30% of the total) is not filled with liquid water because the relative humidity is less than 200%, but the region from P1 to the outlet (70% of the total) is filled with liquid water because the relative humidity is 200% or more.
- the region from the inlet to P2 (40% of the total) is liquid water.
- the area from P2 to the outlet (60% of the whole) is filled with liquid water.
- P3 be the intersection of a line with a back pressure of 100 kPa (abs) and a line with a relative humidity of 200%.
- the region from the inlet to P3 (60% of the whole) is not filled with liquid water, but the region from P3 to the outlet (40% of the whole) is filled with liquid water.
- the back pressure is preferably 150 kPa (abs) to 200 kPa (abs).
- the power generation unit 110 is filled with liquid water in a region where the relative humidity is 200% or more. However, if the relative humidity is 100% or more, water vapor that exceeds the relative humidity of 100% is used. Will condense into liquid water. Therefore, it may be assumed that the power generation unit 110 is filled with liquid water at a value that is not relative humidity 200% but relative humidity is 100% or more and less than 200%.
- the controller 700 can easily fill the power generation unit 110 with liquid water when the back pressure of the oxidant gas in the startup simulation evaluation process is increased.
- This result is the same as the result of the third example in which a back pressure of 140 kPa (abs) to 200 kPa (abs) is preferable.
- the back pressure is more preferably 150 kPa (abs) to 200 kPa (abs).
- FIG. 17 is a control flowchart of voltage recovery of the power generation unit.
- the control unit 700 stops supplying the oxidant gas to the power generation unit 110.
- the cell voltage decreases.
- the reaction of the fuel cell is an exothermic reaction, and when the supply of the oxidant gas is stopped, power generation is not performed, and the temperature of the power generation unit (cell temperature) decreases.
- step S110 the control unit 700 determines whether or not the potential of the oxidizer electrode 123 has dropped below a predetermined value.
- the predetermined value may be 0.6 V, for example. By this step, it is possible to give a history that the oxidant electrode 123 becomes a low voltage to the oxidant electrode 123.
- step S120 control unit 700 determines whether or not the temperature of power generation unit 110 (cell) has dropped below a predetermined value. As described above, the predetermined value may be 40 ° C. or 35 ° C., for example.
- the control part 700 may reverse the order of determination of step S110 and step S120.
- step S130 the control unit 700 resumes the supply of the oxidant gas to the power generation unit 110.
- step S ⁇ b> 140 the control unit 700 executes power generation with a large liquid water flow rate over a wide range of the power generation unit 110. Specifically, the control unit 700 executes power generation so that the accumulated liquid water flow integrated value of the generated water corresponds to 200% relative humidity over a wide range of the power generation unit 110.
- step S110 since the history that the oxidant electrode 123 becomes low voltage is given in step S110, the control unit 700 releases sulfate ions and the like from Pt of the oxidant electrode 123. Easy to make. Then, in step S140, the control unit 700 can recover the power generation of the power generation unit 110 by generating a large amount of generated water and causing the sulfate ions and the like released by the generated water to flow out.
- Modified example of voltage recovery control of power generation unit 110 (1) In the control flowchart shown in FIG. 17, the controller 700 may shut off the load 600 before stopping the oxidant gas in step S100. (2) The control unit 700 may block the load 600 between Step S110 and Step S120. (3) The control unit 700 may connect a fixed resistor instead of the load 600 after the load 600 is interrupted in (1). (4) In (3), the controller 700 may connect the fixed resistor after the supply of the oxidant is stopped in step S100. (5) In (3), the control unit 700 may connect an external load instead of connecting a fixed resistor. (6) In (5), similarly to (4), the controller 700 may connect the external load after the supply of the oxidizing agent is stopped in step S100. (7) In the control flowchart shown in FIG. 17, the controller 700 may shut off the load 600 before stopping the oxidant gas in step S100. (2) The control unit 700 may block the load 600 between Step S110 and Step S120. (3) The control unit 700 may connect a fixed resistor instead of the load 600 after the load 600 is interrupted in
- control unit 700 may stop the recovery process when the cell temperature does not fall below a predetermined value in step S120. In FIG. 17, the control unit 700 may stop the recovery process even when step S120 is performed before step S110, when the cell temperature does not fall below a predetermined value.
- the control unit 700 may cool the power generation unit 110 of the fuel cell 10 by natural cooling or forced cooling. The controller 700 can forcibly cool the power generation unit 110 by supplying a larger amount of cooling water with the cooling water pump 500.
- a PtCo catalyst was supported on carbon particles, and Nafion was mixed to prepare a cathode catalyst ink. Further, a Pt catalyst was supported on carbon particles, and Nafion was mixed to prepare an anode catalyst ink.
- Cathode catalyst ink and anode catalyst ink were applied to a substrate and dried to form a cathode catalyst layer 123 and an anode catalyst layer 122. Thereafter, the cathode catalyst layer and the anode catalyst layer were transferred to the electrolyte membrane 121 (Nafion-based electrolyte membrane) by hot pressing to form a membrane electrode assembly MEA 120 (FIG. 2).
- the area of the MEA 120 is 200 cm 2 or more. Thereafter, the MEA 120 was sandwiched between the gas diffusion layers 132 and 133 to form a module of the power generation unit 110.
- FIG. 18 is a graph showing the relationship between the history time of the oxidant electrode potential of 0.6 V or less and the voltage recovery amount in the eighth example.
- the generated potential fluctuation endurance step, the IV characteristic evaluation step (1), the stop simulation evaluation step, the stop state simulation evaluation step, and the start simulation evaluation step The IV characteristic evaluation step (2) is defined as one cycle.
- the influence of the time for holding the oxidizer electrode at a low potential in the stop state simulation evaluation step was measured.
- the voltage recovery amount was about 17.5 mV or more, and the voltage recovery amount was larger as the holding time was longer. As described in FIG.
- the cell voltage (potential of the oxidant electrode) to 0.7 V or less, it is possible to release sulfate ions and the like from the Pt electrode. If this low potential holding time is lengthened, more sulfate ions and the like can be liberated.
- the time for maintaining the potential of the oxidant electrode at 0.6 V or less is set to 10 minutes or more. However, if the voltage recovery amount is about 10 mV, the potential of the oxidant electrode is set to 0.6 V or less. The holding time may be several minutes.
- FIG. 19 is an explanatory diagram simply showing a configuration for maintaining the potential of the oxidizer electrode at 0.6 V or less for a long time.
- FIG. 19 shows a simplified configuration shown in FIG.
- the configuration shown in FIG. 19 is different from the configuration shown in FIG. 1 in that a check valve 460 is provided downstream of the oxidant gas exhaust valve 440. Thereby, it is suppressed that oxidant gas flows backward from the exhaust system downstream and the potential of the oxidant electrode rises.
- FIG. 20 is a control flowchart of voltage recovery of the power generation unit in the eighth embodiment. Differences from the voltage recovery control flowchart shown in FIG. 17 will be described.
- step S110 of FIG. 17 it is determined only whether or not the potential of the oxidizer electrode has become a predetermined value or less.
- step S115 of FIG. 20 the history of the potential of the oxidizer electrode being 0.6 V or less. The difference is that the holding time is also determined whether (holding time) is 10 or more.
- the determination temperature is 45 ° C., but is substantially the same as step S120 in FIG.
- step S145 is the same as S140 of step in FIG.
- steps S115 and S125 in FIG. 20 may be determined first.
- Fuel gas exhaust valve 350 Pressure gauge 360 ... Fuel gas recovery pipe 370 ... Pump 400 ... Air pump 410 ... Oxidant gas supply pipe 420 ... Valve 430 ...Oxidant Gas exhaust pipe 440 ... Oxidant gas exhaust valve 450 ... Pressure gauge 460 ... Check valve 500 ... Cooling water pump 510 ... Cooling water piping 520 ... Radiator 530 ... Thermometer 600 ... Load 700 ... Control unit
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Abstract
Description
O2 + 4H+ + 4e- → 2H2O …(1)
図3は、燃料電池システムの電圧回復模擬試験のサイクルを示す説明図である。電圧回復模擬試験の1サイクルは、発電電位変動耐久工程と、IV特性評価工程(1)と、停止模擬評価工程と、停止状態模擬評価工程と、起動模擬評価工程と、IV特性評価工程(2)と、有する。IV特性評価工程(2)の次は、次サイクルの発電電位変動耐久工程となる。
V3=V2-V1 …(2)
図10は、起動模擬評価工程における電流密度と、燃料電池10の発電ユニット110の電圧回復量との関係を示すグラフである。第2の実施例は、起動模擬評価工程において、電流密度を0.2A/cm2としたた場合と0.05A/cm2とした場合の2つケースについて電圧回復量を比較した。起動模擬評価工程の発電における電流密度以外のパラメータについては、第1の実施例と同じ値を用いた。電流密度が0.05A/cm2の場合は、電圧回復量は平均0.05mV程度であったのに対し、電流密度が0.2A/cm2の場合は、電圧回復量は平均17.5mV程度であった。起動模擬評価工程における生成水の量は、電流密度の大きさに比例する。起動模擬評価工程における電流密度が大きくなると、発電量が増え、流水量が増加する。その結果、硫酸イオン等の系外への排出速度が大きくなり、酸化剤極123の硫酸イオン等の吸着量が少なくなって燃料電池10の発電ユニット110の電圧が回復し易くなったと考えられる。
図11は、起動模擬評価工程における酸化剤極の背圧と電圧回復量との関係を示すグラフである。第3の実施例は、起動模擬評価工程において、空気(酸化剤ガス)の背圧を140kPa(abs)とした場合と200kPa(abs)とした場合の2つケースについて電圧回復量を比較した。なお、第3の実施例では、燃料電池10の発電ユニット110の入口圧力を、背圧+10kPa(abs)とした。また、第3の実施例では、酸化剤ガスの供給起動模擬評価工程の発電における背圧と入口圧力以外のパラメータについては、第1の実施例と同じ値を用いた。背圧が140kPa(abs)の場合には、電圧回復量は平均17.5mVで有ったのに対し、背圧が200kPa(abs)の場合には、電圧回復量は平均22.0mVであり、背圧が大きい方が、電圧回復量が大きかった。
図13は、起動模擬評価工程における燃料電池10の発電ユニット110の温度(セル温度)と発電ユニット110の出口における相対湿度との関係を示す説明図である。なお、第4の実施例から第7の実施例の結果は、面内で均一に発電し、アノードとカソードとの間の水の移動が無いと仮定して算出した計算値である。横軸がセル温度であり、縦軸が発電ユニット110の出口における相対湿度である。第4の実施例では、セル温度を変化させて、発電ユニット110の出口における相対湿度を比較した。なお、第4の実施例では、酸化剤ガスのストイキ比を2.0、酸化剤ガスの背圧を100kPa(abs)、起動模擬評価工程において燃料電池10の発電ユニット110から引く電流の電流密度を0.2A/cm2としている。セル温度を低くすると、発電ユニット110の出口における相対湿度は大きくなる結果が得られた。セル温度が高くなると、飽和水蒸気圧が高くなるので、相対湿度(%)(=絶対水蒸気圧[Pa]/飽和水蒸気圧[Pa]×100)が小さくなる。なお、絶対水蒸気圧は、液水流水量積算値に比例する。このように、制御部700は、セル温度を低くすることにより、液水の量を増大させ、硫酸イオン等を流しやすくして、発電ユニット110の電圧を回復させ易くすることが可能となる。
図14は、起動模擬評価工程における電流密度と発電ユニット110の出口における相対湿度との関係を示す説明図である。横軸が燃料電池10の発電ユニット110から引かれる電流の電流密度であり、縦軸が発電ユニット110の出口における相対湿度である。なお、第5の実施例では、酸化剤ガスのストイキ比を2.0、酸化剤ガスの背圧を100kPa(abs)、起動模擬評価工程において燃料電池10の発電ユニット110から引く電流の電流密度を0.2A/cm2としている。図14に示す結果からは、起動模擬評価工程における電流密度を大きくしても、発電ユニット110の出口における相対湿度には有意差が見られなかった。なお、出口における相対湿度が200%以上の時に、十分な流水量があるとすると、電流密度は、0.05A/cm2から0.5A/cm2のいずれであっても良い。電流密度を大きくすると、発電量を大きくすることが出来、液水流水量積算値を大きくすることが可能となる。したがって、電流密度を大きくすると、遊離した硫酸イオン等を迅速に排出することができる。
図15は、起動模擬評価工程における酸化剤ガスのストイキ比と発電ユニット110の出口における相対湿度との関係を示す説明図である。横軸は、発電ユニット110中の位置であり、左端が発電ユニット110における酸化剤ガス入口、右端が発電ユニットにおける酸化剤ガス出口である。縦軸は、相対湿度である。なお、第6の実施例では、セル温度を35℃、酸化剤ガスの背圧を100kPa(abs)、起動模擬評価工程において燃料電池10の発電ユニット110から引く電流の電流密度を0.2A/cm2としている。また、第6の実施例では、酸化剤ガスの露点を-40℃として、ほとんど水分を含まない酸化剤ガスを用いた。
図16は、起動模擬評価工程における酸化剤ガスの背圧と発電ユニット110の出口における相対湿度との関係を示す説明図である。図15と同様に、横軸は、発電ユニット110中の位置であり、左端が発電ユニット110における酸化剤ガス入口、右端が発電ユニットにおける酸化剤ガス出口である。縦軸は、相対湿度である。第7の実施例では、セル温度を35℃、酸化剤ガスのストイキ比を2.0、起動模擬評価工程において燃料電池10の発電ユニット110から引く電流の電流密度を0.2A/cm2としている。また、第6の実施例では、酸化剤ガスの露点を-40℃として、ほとんど水分を含まない酸化剤ガスを用いた。
図17は、発電ユニットの電圧回復の制御フローチャートである。ステップS100では、制御部700は、発電ユニット110への酸化剤ガスの供給を停止する。図5に示されるように、セル電圧は下がっていく。また、燃料電池の反応は発熱反応であり、酸化剤ガスの供給が停止されると、発電が行われなくなり、発電ユニットの温度(セル温度)は下がっていく。
(1)図17に示した制御フローチャートにおいて、制御部700は、ステップS100の酸化剤ガスを停止する前に、負荷600を遮断してもよい。
(2)制御部700は、負荷600の遮断を、ステップS110とステップS120との間に行っても良い。
(3)制御部700は、(1)において、負荷600を遮断した後、負荷600の代わりに固定抵抗を接続しても良い。
(4)(3)において、制御部700は、固定抵抗の接続をステップS100の酸化剤の供給停止の後に行っても良い。
(5)(3)において、制御部700は、固定抵抗を接続する代わりに外部負荷を接続しても良い。
(6)(5)において、制御部700は、(4)と同様に、外部負荷の接続をステップS100の酸化剤の供給停止の後に行っても良い。
(7)図17に示した制御フローチャートにおいて、制御部700は、ステップS120において、セル温度が所定の値以下に下がらなかった場合には、回復処理を停止しても良い。なお、図17において、制御部700は、ステップS120をステップS110の前に行う場合であっても、セル温度が所定の値以下に下がらなかった場合には、回復処理を停止しても良い。
(8)図17に示した制御フローチャートのステップS120において、制御部700は、燃料電池10の発電ユニット110の冷却を自然冷却で行っても良く、強制冷却で行っても良い。制御部700は、冷却水ポンプ500により、より大量の冷却水を供給することにより、発電ユニット110を強制冷却することが可能である。
第8の実施例では、PtCo触媒をカーボン粒子に担持し、ナフィオンを混合してカソード触媒インクを作成した。また、Pt触媒をカーボン粒子に担持し、ナフィオンを混合してアノード触媒インクを作成した。カソード触媒インク、アノード触媒インクを基板に塗布乾燥して、カソード触媒層123、アノード触媒層122を形成した。その後、カソード触媒層、アノード触媒層を電解質膜121(ナフィオン系電解質膜)に熱プレスにより転写して膜電極接合体MEA120(図2)を作成した。第8の実施例では、MEA120の面積を、200cm2以上とした。その後、MEA120をガス拡散層132、133で挟み込んで発電ユニット110のモジュールを形成した。
20…燃料電池システム
100…燃料電池スタック
110…発電ユニット
120…膜電極接合体
121…電解質膜
122…アノード触媒層、燃料極
123…カソード触媒層、酸化剤極
132、133…ガス拡散層
142、143…多孔体ガス流路
152、153…セパレータプレート
155…冷却水流路
160…シールガスケット
200…集電板
210…絶縁板
230、231…エンドプレート
240…テンションロッド
250…ナット
300…燃料タンク
310…燃料ガス供給管
320…バルブ
330…燃料ガス排気管
340…燃料ガス排気バルブ
350…圧力計
360…燃料ガス回収管
370…ポンプ
400…エアポンプ
410…酸化剤ガス供給管
420…バルブ
430…酸化剤ガス排気管
440…酸化剤ガス排気バルブ
450…圧力計
460…逆止弁
500…冷却水ポンプ
510…冷却水配管
520…ラジエーター
530…温度計
600…負荷
700…制御部
Claims (14)
- 燃料電池システムであって、
触媒を有する燃料電池と、
前記燃料電池に燃料ガスを供給する燃料ガス供給部と、
前記燃料電池に酸化剤ガスを供給する酸化剤ガス供給部と、
前記燃料ガスの供給及び停止と、前記酸化剤ガスの供給及び停止と、前記燃料電池の発電と、を制御する制御部と、
を備え、
前記制御部は、
前記燃料電池への前記酸化剤ガスの供給を停止させ、
前記燃料電池が発生させる電圧が予め定められた第1の値以下まで下がり、前記燃料電池の温度が予め定められた第2の値以下となった後に、前記燃料電池への前記酸化剤ガスの供給を再開させて、前記燃料電池に発電を再開させて水を生成させることによって前記燃料電池の電圧を回復させる、燃料電池システム。 - 請求項1に記載の燃料電池システムにおいて、
前記第1の値は、0.6V以下の正の値である、燃料電池システム。 - 請求項1または2に記載の燃料電池システムにおいて、
前記燃料電池の再発電時後の前記燃料電池の反応により生成する生成水の前記燃料電池内の分布について、前記燃料電池の前記酸化剤ガスが流れる酸化剤ガス流路の中央において、相対湿度200%以上に相当する量となるように、前記制御部は、前記燃料電池の再発電を実行する、燃料電池システム。 - (追加)
請求項1~3のいずれか一項に記載の燃料電池システムにおいて、
前記電圧を前記第1の値以下に保持する時間を10分以上とする、燃料電池システム。 - 請求項1~4のいずれか一項に記載の燃料電池システムにおいて、
前記第2の値は、室温以上40℃以下の値である、燃料電池システム。 - 請求項1~5のいずれか一項に記載の燃料電池システムにおいて、
前記制御部は、前記燃料電池を電流密度0.1A/cm2以上0.2A/cm2以下の電流で再発電させる、燃料電池システム。 - 請求項1~6のいずれか一項に記載の燃料電池システムにおいて、さらに、
前記燃料電池の出口における前記酸化剤ガスの背圧を調整する背圧調整部を備え、
前記制御部は、再発電時に前記背圧が140kPa(abs)以上200kPa(abs)以下となるように制御する、燃料電池システム。 - 燃料電池システムにおける燃料電池の発電性能回復方法であって、
燃料電池への酸化剤ガスの供給を停止させる工程と、
前記燃料電池が発生させる電圧が予め定められた第1の値以下まで下がり、前記燃料電池の温度が予め定められた第2の値以下となった後に、前記燃料電池への前記酸化剤ガスの供給を再開させて、前記燃料電池に発電を再開させて水を生成させることによって前記燃料電池の電圧を回復させる工程と、
を有する、発電性能回復方法。 - (追加)
請求項8に記載の発電性能回復方法において、
前記第1の値は、0.6V以下の正の値である、発電性能回復方法。 - (追加)
請求項8または9に記載の発電性能回復方法において、
前記燃料電池の再発電時後の前記燃料電池の反応により生成する生成水の前記燃料電池内の分布について、前記燃料電池の前記酸化剤ガスが流れる酸化剤ガス流路の中央において、相対湿度200%以上に相当する量となるように前記燃料電池の再発電が実行される、発電性能回復方法。 - (追加)
請求項8~10のいずれか一項に記載の発電性能回復方法において、
前記電圧が前記第1の値以下に保持される時間は10分以上である、発電性能回復方法。 - 請求項8~11のいずれか一項に記載の発電性能回復方法において、
前記第2の値は、室温以上40℃以下の値である、発電性能回復方法。 - 請求項8~12のいずれか一項に記載の発電性能回復方法において、
前記燃料電池は、電流密度0.1A/cm2以上0.2A/cm2以下の電流で再発電される、発電性能回復方法。 - 請求項8~13のいずれか一項に記載の発電性能回復方法において、
再発電時に酸化剤ガスの背圧が140kPa(abs)以上200kPa(abs)以下となるように制御される、発電性能回復方法。
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US14/654,960 US20150333349A1 (en) | 2012-12-26 | 2013-09-04 | Fuel cell system and power generation performance recovery method of a fuel cell in a fuel cell system |
DE112013006226.7T DE112013006226T5 (de) | 2012-12-26 | 2013-09-04 | Brennstoffzellensystem und Leistungserzeugungseffizienzwiederherstellungsverfahen einer Brennstoffzelle in einem Brennstoffzellensystem |
CN201380067827.8A CN104885277A (zh) | 2012-12-26 | 2013-09-04 | 燃料电池系统以及燃料电池系统中燃料电池的发电性能恢复方法 |
JP2014554071A JPWO2014103101A1 (ja) | 2012-12-26 | 2013-09-04 | 燃料電池システム及び燃料電池システムにおける燃料電池の発電性能回復方法 |
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JP2016035910A (ja) * | 2014-08-01 | 2016-03-17 | 本田技研工業株式会社 | 燃料電池システムの運転方法 |
DE102015117740B4 (de) | 2014-11-07 | 2019-08-14 | Toyota Jidosha Kabushiki Kaisha | Verfahren zum Herstellen einer Membranelektrodenanordnung |
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US10069160B2 (en) | 2016-07-27 | 2018-09-04 | GM Global Technology Operations LLC | Stack voltage control for recovery mode using boost converter |
CN108390078B (zh) * | 2018-02-28 | 2021-08-03 | 广东国鸿氢能科技有限公司 | 一种恢复燃料电池电堆性能的方法及装置 |
CN111682245B (zh) * | 2020-05-12 | 2022-03-08 | 广东国鸿氢能科技有限公司 | 一种燃料电池电堆性能恢复方法 |
CN114914487B (zh) * | 2022-05-10 | 2024-05-17 | 西安交通大学 | 一种氢燃料电池测试台供气湿度测量装置及测量方法 |
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DE102015117740B4 (de) | 2014-11-07 | 2019-08-14 | Toyota Jidosha Kabushiki Kaisha | Verfahren zum Herstellen einer Membranelektrodenanordnung |
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