WO2013099097A1 - 直接酸化型燃料電池システム - Google Patents
直接酸化型燃料電池システム Download PDFInfo
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- WO2013099097A1 WO2013099097A1 PCT/JP2012/007421 JP2012007421W WO2013099097A1 WO 2013099097 A1 WO2013099097 A1 WO 2013099097A1 JP 2012007421 W JP2012007421 W JP 2012007421W WO 2013099097 A1 WO2013099097 A1 WO 2013099097A1
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- fuel
- fuel cell
- temperature
- supply device
- oxidant
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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
- H01M8/04253—Means for solving freezing problems
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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
- H01M8/04694—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
- H01M8/04—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
- H01M8/04858—Electric variables
- H01M8/04925—Power, energy, capacity or load
- H01M8/0494—Power, energy, capacity or load 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
- H01M8/04955—Shut-off or shut-down of fuel cells
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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
- H01M8/1009—Fuel cells with solid electrolytes with one of the reactants being liquid, solid or liquid-charged
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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
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1009—Fuel cells with solid electrolytes with one of the reactants being liquid, solid or liquid-charged
- H01M8/1011—Direct alcohol fuel cells [DAFC], e.g. direct methanol fuel cells [DMFC]
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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 direct oxidation fuel cell system, and more particularly to prevention of freezing of a fuel cell in a low temperature environment.
- Fuel cells are being put into practical use as in-vehicle power sources and household cogeneration system power sources.
- portable small electronic devices such as notebook personal computers, cellular phones, and personal digital assistants (PDAs), outdoor leisure power sources, and emergency backup power sources has also been studied. Since the fuel cell can generate power continuously by replenishing fuel, it is expected that the convenience of portable small electronic devices and portable power sources can be further improved.
- PDAs personal digital assistants
- DOFC Direct Oxidation Fuel Cell
- DMFC direct methanol fuel cell
- the fuel cell includes a stack in which a plurality of cells are connected in series.
- Each cell includes a membrane-electrode assembly including an electrolyte membrane and an anode and a cathode disposed on both sides of the electrolyte membrane, an anode-side separator in contact with the anode, and a cathode-side separator in contact with the cathode.
- the anode side separator has a fuel flow path for supplying liquid fuel (fuel aqueous solution) to the anode
- the cathode side separator has an oxidant flow path for supplying oxidant to the cathode.
- the liquid fuel and the oxidant are supplied to the fuel cell by a supply device such as a pump.
- Reactions at the anode and cathode of DMFC are shown in the following formulas (11) and (12), respectively.
- the oxygen introduced into the cathode is generally taken from the atmosphere.
- methanol and water react to produce carbon dioxide.
- Fuel drainage from the anode containing carbon dioxide and unreacted fuel is sent to a tank (hereinafter referred to as a circulation tank) for circulating fuel and water in the system together with newly supplied fuel.
- a circulation tank for circulating fuel and water in the system together with newly supplied fuel.
- the cathode produces more water than is consumed at the anode.
- a part of the fluid containing the produced reaction water and unreacted oxygen is also sent to the circulation tank.
- water stored in the circulation tank and high-concentration methanol in the fuel tank are mixed and supplied to the anode of the fuel cell, and air as an oxidant is supplied to the cathode. .
- circulation pump inside the fuel cell, inside the pipe connecting the anode and the circulation tank, inside the pipe connecting the cathode and the circulation tank, and inside the pump for circulating fuel and water (hereinafter referred to as circulation pump) And the like include water-soluble fuel and water (fuel aqueous solution).
- the aqueous fuel solution may freeze in a low temperature environment, and it is conceivable that the components constituting the circulation system are damaged by the volume expansion pressure during freezing.
- Patent Document 1 proposes a method of preventing freezing due to heat generated during power generation of a fuel cell and stopping power generation when the temperature rises to a predetermined temperature. Further, Patent Document 2 proposes that the reaction product water of the fuel cell is discharged to the outside at a low temperature to prevent damage to the parts due to freezing.
- Patent Document 2 it is proposed to discharge the aqueous fuel solution in the circulation system to the outside.
- DMFC uses methanol as the fuel, it is desirable to release the aqueous solution to the outside. Absent.
- One aspect of the present invention is a fuel including an anode to which a water-soluble fuel is supplied, a cathode to which an oxidant is supplied, and an electrolyte membrane having water permeability interposed between the anode and the cathode.
- a fuel tank for storing the fuel;
- a first fuel supply device for supplying an aqueous fuel solution containing the fuel and water to the anode;
- a second fuel supply device for supplying fuel stored in the fuel tank to the first fuel supply device;
- An oxidant supply device for supplying an oxidant to the cathode;
- a temperature sensor for detecting a temperature FT of the fuel cell;
- a controller that controls the first fuel supply device, the second fuel supply device, and the oxidant supply device, and that controls the start and stop of power generation of the fuel cell;
- the control unit remains in a state where power generation is stopped when the fuel cell stops power generation and the temperature FT is equal to or lower than a first reference temperature related to freezing of water and equal to or higher than a second reference temperature.
- the present invention relates to a fuel cell system that executes at least a supply operation of the first fuel supply device.
- the present invention includes, for example, at least one membrane electrode assembly, a fuel inlet for introducing fuel, a fuel outlet for discharging fuel drainage, an oxidant inlet for introducing oxidant, unconsumed oxidant, and generated water.
- a fuel cell stack having a oxidant outlet for discharging a fluid containing a first fuel supply device for supplying the fuel to the fuel inlet, and an oxidant supply device for supplying the oxidant to the oxidant inlet.
- a circulation tank containing the fuel drainage and a part of the generated water, a fuel discharge path for guiding the fuel drainage to the circulation tank, and a generation for guiding at least a part of the generated water to the circulation tank
- a fuel crossover comprising: a water discharge path; and a second fuel supply device for injecting high-concentration fuel contained in the fuel tank into a path between the circulation tank and the first fuel supply device.
- the present invention provides, for example, at least one membrane electrode assembly, a fuel inlet for introducing fuel, a fuel outlet for discharging fuel drainage, an oxidant inlet for introducing an oxidant, an unconsumed oxidant and A fuel cell stack having an oxidant outlet that discharges a fluid containing product water; a first fuel supply device that supplies the fuel to the fuel inlet; and an oxidant that supplies the oxidant to the oxidant inlet.
- a supply device a circulation tank that contains the fuel drainage and a part of the generated water, a fuel discharge passage that guides the fuel drainage to the circulation tank, and at least a part of the generated water to the circulation tank.
- a second fuel supply device for injecting high-concentration fuel contained in a fuel tank into a guided water discharge path, a path between the circulation tank and the first fuel supply device, the fuel cell, First fuel supply device, A temperature detector for detecting the temperature of at least one of the second fuel supply device, the circulation tank, the fuel discharge path and the external ambient temperature (environmental temperature); and a control unit for controlling the power generation of the fuel cell; A determination unit for determining the possibility of occurrence of freezing based on a temperature detection result by the temperature detector; and a storage unit in which a temperature-necessary calorific value table is stored in advance, and the temperature stored in the storage unit in advance-
- the temperature inside the system may be increased by using heat generation by the fuel cell and fuel crossover according to the necessary heat generation amount table.
- fuel consumption can be suppressed and freezing of the fuel cell can be effectively prevented.
- FIG. 1 is a block diagram showing a schematic configuration of a direct oxidation fuel cell system according to an embodiment of the present invention. It is sectional drawing which shows an example of the fuel cell used for the system. It is a flowchart which shows the procedure of the freeze prevention process in the same system. It is a graph which shows the relationship between environmental temperature or battery temperature, and the emitted-heat amount required for the freeze prevention of a fuel cell. 3 is a graph showing a generated voltage-generated current characteristic curve of a fuel cell. It is a graph which shows the example of a setting of the emitted-heat amount by the electric power generation corresponding to environmental temperature or a battery temperature in the case of preventing freezing of a fuel cell by electric power generation.
- FIG. 1 is a block diagram showing a schematic configuration of a direct oxidation fuel cell system according to an embodiment of the present invention.
- FIG. 2 is a sectional view showing an example of a fuel cell used in the system.
- the illustrated direct oxidation fuel cell system 10 (hereinafter simply referred to as the system 10) supplies a fuel cell 12 that is a DMFC and an aqueous fuel solution containing water-soluble fuel and water to the fuel inlet of the fuel cell 12.
- a circulation pump 48 constituting the first fuel supply device
- a fuel pump 60 constituting a second fuel supply device for supplying high concentration fuel from the fuel tank 56 to the suction side of the circulation pump 48
- an air pump 62 constituting an oxidant supply device for supplying the oxidant to the air pump.
- the fuel outlet of the fuel cell 12 (discharge port for unused fuel etc.) is connected to the circulation tank 50, and the oxidant outlet (discharge port for unused oxidizer etc.) of the fuel cell 12 is also connected to the circulation tank 50. .
- the circulation tank 50 is connected to the suction side of the circulation pump 48.
- the outputs (discharge flow rates) of the circulation pump 48, the fuel pump 60, and the air pump 62 are controlled by the control unit 58.
- a microcomputer including a calculation unit 58a, a determination unit 58b, and a storage unit 58c is used.
- the storage unit 58c stores various data such as a first temperature T1, a second temperature T2, a third temperature T3, and a battery temperature-necessary heat generation amount table that are set in advance.
- the output power of the fuel cell 12 is output to the outside through the DC / DC converter 52, for example.
- the DC / DC converter 52 can be controlled by the control unit 58.
- the storage battery 54 may be included in the system 10 by connecting a storage battery 54 that stores the generated power of the fuel cell 12 to the output side of the DC / DC converter 52.
- the system 10 includes a temperature sensor 64 that detects the temperature FT of the fuel cell 12 (hereinafter referred to as cell temperature FT) or the internal temperature of the circulation system, which will be described later.
- the battery temperature FT detected by the temperature sensor 64 is input to the control unit 58.
- the battery temperature FT can also be detected indirectly by detecting the temperature of any part of the circulation system.
- the temperature of each part of the circulation system can be indirectly detected by detecting the battery temperature FT.
- the battery temperature FT can be indirectly detected by detecting the environmental temperature.
- the environmental temperature can be indirectly detected by detecting the battery temperature FT. Therefore, instead of the battery temperature FT or in order to detect the battery temperature FT, it is possible to detect the environmental temperature or the temperature of any part of the circulation system.
- the fuel cell 12 includes a fuel inlet (not shown) for introducing a water-soluble fuel, a fuel outlet for discharging a fuel drain, an oxidant inlet for introducing an oxidant, a fluid containing unconsumed oxidant and reaction product water. And an oxidant outlet for discharging (exhaust fluid).
- the main body of a fuel cell generally includes a stack in which two or more cells are electrically connected in series.
- FIG. 2 schematically shows the structure of the cell with a cross-sectional view.
- the cell 15 is a direct methanol fuel cell, and includes a polymer electrolyte membrane 17 and an anode 14 and a cathode 16 disposed so as to sandwich the polymer electrolyte membrane 17 therebetween.
- the polymer electrolyte membrane 17 has hydrogen ion conductivity.
- Methanol as a fuel is supplied to the anode 14.
- Air that is an oxidant is supplied to the cathode 16.
- an anode side separator 26 is stacked on the anode 14, and an end plate 46 ⁇ / b> A is disposed above the anode side separator 26.
- a cathode separator 36 is laminated on the cathode 16 (downward in the drawing), and an end plate 46B is disposed further above the cathode separator 36.
- the end plates 46A and 46B are not provided for each cell, but are arranged one by one at both ends in the stacking direction of the cell stack.
- Each end plate functions as a current collecting plate that relays power sent to the output terminals 12a and 12b of the fuel cell.
- the power generated by the fuel cell is sent to an external load (not shown) or the storage battery 54 via the DC / DC converter 52.
- a gasket 42 is disposed between the anode side separator 26 and the polymer electrolyte membrane 17 so as to surround the anode 14, and between the cathode side separator 36 and the polymer electrolyte membrane 17, so as to surround the cathode 16.
- a gasket 44 is disposed. Gaskets 42 and 44 prevent fuel and oxidant from leaking out of anode 14 and cathode 16, respectively.
- the two end plates 46A and 46B are fastened to each other so as to pressurize each separator and MEA (Membrane ⁇ Electrode Assembly: membrane-electrode assembly) with bolts and springs (not shown) to constitute the cell 15. .
- MEA Membrane ⁇ Electrode Assembly: membrane-electrode assembly
- the anode 14 includes an anode catalyst layer 18 and an anode diffusion layer 20.
- the anode catalyst layer 18 is in contact with the polymer electrolyte membrane 17.
- the anode diffusion layer 20 includes an anode porous substrate 24 that has been subjected to a water-repellent treatment, and an anode water-repellent layer 22 that is formed on the surface and is made of a highly water-repellent material.
- the anode water repellent layer 22 and the anode porous substrate 24 are laminated in this order on the surface of the anode catalyst layer 18 opposite to the surface in contact with the polymer electrolyte membrane 17.
- the cathode 16 includes a cathode catalyst layer 28 and a cathode diffusion layer 30.
- the cathode catalyst layer 28 is in contact with the surface of the polymer electrolyte membrane 17 opposite to the surface with which the anode catalyst layer 18 is in contact.
- the cathode diffusion layer 30 includes a cathode porous substrate 34 that has been subjected to water repellent treatment, and a cathode water repellent layer 32 that is formed on the surface thereof and is made of a highly water repellent material.
- the cathode water repellent layer 32 and the cathode porous substrate 34 are laminated in this order on the surface of the cathode catalyst layer 28 opposite to the surface in contact with the polymer electrolyte membrane 17.
- a laminate composed of the polymer electrolyte membrane 17, the anode catalyst layer 18 and the cathode catalyst layer 28 is responsible for power generation of the fuel cell and is called CCM (Catalyst Coated Membrane).
- the MEA is a laminate composed of the CCM, the anode diffusion layer 20 and the cathode diffusion layer 30.
- the anode diffusion layer 20 and the cathode diffusion layer 30 are responsible for the uniform dispersion of the fuel and oxidant supplied to the anode 14 and the cathode 16 and the smooth discharge of water and carbon dioxide as products.
- the anode-side separator 26 has a fuel flow path 38 for supplying fuel to the anode 14 on the contact surface with the anode porous substrate 24.
- the fuel flow path 38 is formed of, for example, a recess or groove formed on the contact surface and opening toward the anode porous substrate 24.
- the fuel flow path communicates with the fuel inlet and the fuel outlet of the fuel cell 12.
- the cathode side separator 36 has an oxidant channel 40 for supplying an oxidant (air) to the cathode 16 on the contact surface with the cathode porous substrate 34.
- the oxidant channel 40 is also formed of, for example, a recess or groove formed on the contact surface and opening toward the cathode porous substrate 34.
- the oxidant flow path communicates with the oxidant inlet and the oxidant outlet of the fuel cell.
- the circulation pump 48 is connected to the circulation tank 50 and the fuel pump 60.
- the fuel pump 60 is connected to a fuel tank 56 that stores high-concentration fuel.
- the high-concentration fuel is injected into the pipe 3 a that connects the suction part of the circulation pump 48 and the circulation tank 50.
- the mixture of water and high-concentration fuel (fuel aqueous solution) from the circulation tank 50 is introduced into the fuel cell 12 through the pipe 3b connecting the fuel inlet of the fuel cell and the circulation pump 48.
- the aqueous fuel solution introduced into the fuel cell 12 is introduced from the fuel inlet of the fuel cell 12 into the internal fuel flow path.
- the fuel flowing through the fuel flow path passes through the flow path while being consumed by power generation.
- the aqueous fuel solution is discharged from the fuel outlet of the fuel cell 12 as fuel drainage containing carbon dioxide.
- the fuel concentration in the fuel drainage is decreasing, it contains unreacted fuel. For this reason, the fuel drainage is reused after being separated from carbon dioxide. Therefore, the fuel drainage liquid is collected in the circulation tank 50 through the pipe 3 c that connects the fuel outlet of the fuel cell 12 and the circulation tank 50.
- the method for separating carbon dioxide from the fuel effluent is not particularly limited. For example, by providing a window portion in the circulation tank 50 and closing the window portion with a gas-liquid separation membrane that allows carbon dioxide to pass through, it can be discharged to the outside.
- the air pump 62 takes in air from the outside and plays a role of leading to the oxidant inlet of the fuel cell 12 as an oxidant.
- the oxidant supply device includes at least an air pump 62.
- the part which controls the air pump 62 in the control part 58 can also be interpreted as a part of oxidant supply apparatus.
- the part that controls the circulation pump 48 in the control unit 58 may be interpreted as a part of the first fuel supply device, or the part that controls the fuel pump 60 in the control unit 58 may be a part of the second fuel supply device. It can also be interpreted as a part.
- Air is introduced from the oxidant inlet of the fuel cell 12 into the oxidant flow path.
- the air passes through the flow path while oxygen is consumed.
- the air is discharged from the oxidant outlet of the fuel cell 12 as an exhaust fluid containing water vapor (reaction product water).
- the exhaust fluid is guided to the circulation tank 50 by the pressure from the air pump 62 through the piping 3 d that connects the oxidant outlet of the fuel cell 12 and the circulation tank 50.
- the circulation tank 50 separates and collects a part of the reaction product water from the exhaust fluid and discharges the remainder to the outside.
- methanol is used as the fuel, theoretically, for every 1 mol of water consumed at the anode, 3 mol of water is produced at the cathode. Therefore, the amount of water in the system can theoretically be maintained substantially constant by recovering the amount of water corresponding to 1 mole of the reaction product water. The remaining 2 moles of water are discharged to the outside of the circulation tank 50. The separated reaction product water is collected in the circulation tank 50.
- the fuel and the oxidant can be supplied to the fuel cell 12 to generate electricity.
- the temperature of the fuel cell rises due to the heat generation, and a temperature above a certain level is maintained.
- the fuel cell 12 the circulation tank 50 and the circulation pump 48, and the pipes 3a to 3d connecting them (hereinafter, these parts are generically referred to).
- water remaining inside the circulation system There is a possibility that water remaining inside the circulation system) will freeze. If water freezes, each part of the circulation system may be damaged by the expansion pressure.
- the heat generated by the crossover of the fuel is used to prevent water from freezing, thereby preventing each part of the circulation system from being damaged.
- FIG. 3 is a flowchart showing the flow of the freeze prevention process.
- first to third anti-freezing operations are executed according to the temperature of the fuel cell.
- FIG. 4 is a graph showing the relationship between the environmental temperature or the temperature of the fuel cell and the calorific value necessary for preventing freezing.
- the battery temperature FT it is determined whether the temperature FT of the fuel cell 12 (hereinafter referred to as the battery temperature FT) is equal to or lower than a first temperature T1 that is a reference temperature when the first antifreezing operation is performed (ST1). This determination is performed by the determination unit 58b in the control unit 58. If the battery temperature FT exceeds the first temperature T1 (Yes in ST1), there is no particular problem, so after performing a predetermined time (for example, 0.1 second) without performing any anti-freezing operation, The determination procedure of ST1 is executed again. The determination procedure of ST1 is repeatedly executed until the battery temperature FT becomes equal to or lower than the first temperature T1.
- a predetermined time for example, 0.1 second
- the battery temperature FT is further a second temperature T2 (T2 ⁇ T1) that is a reference temperature for performing the second antifreezing operation. ) It is determined whether or not (ST2). This determination is performed by the determination unit 58b in the control unit 58. Here, if the battery temperature FT exceeds the second temperature T2 (Yes in ST2), T2 ⁇ FT ⁇ T1, and the control unit 58 performs the first freezing in order to prevent the fuel cell 12 from freezing.
- the circulation pump 48 is operated at a predetermined flow rate F1 so as to start the prevention operation (ST3).
- the remaining fuel aqueous solution (methanol aqueous solution) having the first concentration FC1 in the circulation tank 50 is supplied to the fuel cell 12, a fuel crossover occurs, and the fuel cell 12 generates heat.
- FC1 methanol aqueous solution
- each part of the circulation system specifically, the fuel cell 12, the circulation pump 48, the circulation tank 50, the pipe 3a connecting the circulation pump 48 and the circulation tank 50, and the circulation pump 48 and the fuel cell 12 are connected.
- the first temperature T1 is preferably set to a temperature within the range of 0 to 5 ° C. Accordingly, the first freeze prevention operation can be started while the temperature of each part of the circulation system exceeds 0 ° C.
- the circulation pump 48 is operated, so that the aqueous fuel solution having the first concentration FC1 remaining in each part of the circulation system (mainly inside the circulation tank 50) is supplied to the anode of the fuel cell 12. Supplied.
- the fuel concentration (methanol concentration, that is, FC1) of the aqueous fuel solution remaining in each part of the circulation system is usually about 0.2 to 0.5 mol / L, which is a very low concentration.
- At least a part of the fuel supplied to the anode passes through the polymer electrolyte membrane and reaches the cathode, and is oxidized by oxygen remaining in the cathode. This phenomenon is called fuel crossover.
- the first antifreezing operation is performed as a preparatory operation for the second antifreezing operation that is activated when the temperature of the fuel cell system 10 further decreases, rather than preventing the fuel cell system 10 from freezing.
- the first freeze prevention operation is performed for the purpose of preheating water remaining in the circulation system before the temperature of each part of the circulation system becomes 0 ° C. or less. Thereby, even if the temperature of each part of a circulation system becomes 0 degrees C or less, it can prevent that the water of the inside freezes.
- the operation of the circulation pump 48 is started, and when a predetermined time (for example, 0.1 second) elapses, the process returns to ST1.
- a predetermined time for example, 0.1 second
- the steps ST1, ST2 and ST3 are repeatedly executed. That is, during that period, the first freeze prevention operation is continuously executed.
- the battery temperature FT is a third temperature that is a reference temperature for performing the third antifreezing operation. It is determined whether the temperature is equal to or lower than T3 (ST4). This determination is performed by the determination unit 58b in the control unit 58.
- the control unit 58 performs the predetermined flow rate F2 so as to execute the second antifreezing operation.
- the fuel pump 60 is operated (ST5).
- the operation of the circulation pump 48 is also continued.
- a high concentration (for example, 50% by mass or more) aqueous fuel (methanol) solution is supplied from the fuel tank 56 to the circulation system, and the second concentration FC2 aqueous solution having a concentration higher than the first concentration FC1 is the fuel cell. 12 is supplied.
- the amount of fuel crossover increases, and the amount of heat generated by the fuel cell 12 also increases compared to the first antifreezing operation.
- the second concentration FC2 is desirably 0.5 to 4 mol / L.
- the second concentration FC2 is less than 0.5 mol / L, sufficient fuel heat generation cannot be expected because the fuel crossover is small.
- the power generated by the fuel cell 12 when the operation shifts to the third antifreezing operation described later is extremely reduced, and sufficient heat generation cannot be expected.
- the second concentration FC2 exceeds 4 mol / L, it is considered that the amount of fuel crossover increases, leading to deterioration of MEA and reduction of generated power.
- the second anti-freezing operation is such that the temperature of each part of the circulation system is 0 ° C.
- heat generation amount the amount of heat generated by the fuel crossover to raise the temperature of the circulation system
- FIG. 4 is a graph showing the relationship between the required heat value and the environmental temperature or battery temperature.
- the required heat generation amount increases as the environmental temperature decreases. Therefore, as the environmental temperature decreases, it becomes impossible to prevent the fuel cell from freezing only by heat generated by fuel crossover. Therefore, the third temperature T3 is set to a temperature slightly higher than the lower limit temperature at which the fuel cell can be prevented from freezing due to heat generated by the fuel crossover.
- the fuel cell is prevented from freezing by the second freeze prevention operation or the first freeze prevention operation. As a result, the fuel cell can be prevented from freezing with the minimum amount of fuel consumption, and the amount of fuel consumed can be saved.
- the operation of the fuel pump 60 is started, and when a predetermined time (for example, 0.1 second) elapses, the process returns to ST1. While T3 ⁇ FT ⁇ T2, the steps ST1, ST2, ST4 and ST5 are repeatedly executed. That is, during that period, the second freeze prevention operation is continuously executed. On the other hand, when it is determined in ST4 that the battery temperature FT is equal to or lower than the third temperature T3 (No in ST4), the control unit 58 supplies air by the air pump 62 so as to execute the third anti-freezing operation. The operation is started to cause the fuel cell 12 to start power generation (ST6).
- a predetermined time for example, 0.1 second
- the operation of the circulation pump 48 and the fuel pump 60 is also continued, and for example, the aqueous fuel solution having the second concentration FC2 is supplied to the fuel cell 12.
- the amount of heat generated by the fuel cell 12 is also larger than that in the second freeze prevention operation.
- the third freeze prevention operation will be described in more detail.
- the third anti-freezing operation is performed when the fuel cell 12 is further cooled and the freezing cannot be prevented by the second anti-freezing operation.
- the fuel cell 12 According to the battery temperature-necessary calorific value table stored in advance in the storage unit 58c in the control unit 58, the fuel cell 12 within a range where the calorific value generated by the power generation of the fuel cell 12 exceeds the necessary calorific value according to the battery temperature FT. To generate electricity. Thereby, the temperature of each part of the circulation system can be raised to exceed 0 ° C. by heat generated by the power generation of the fuel cell 12 to prevent freezing.
- the battery temperature-necessary calorific value table is a group of discrete data on the relationship between battery temperature (or environmental temperature) and necessary calorific value as shown in the graph of FIG. 4 in a table format. It is a thing.
- the storage unit 12c stores a relational expression indicating the relationship between the battery temperature (or environmental temperature) and the required heat generation as shown by the graph in FIG. 4 instead of the battery temperature-necessary heat generation table. Also good. Next, heat generation by power generation of the fuel cell will be described in detail.
- Fuel cells have a characteristic that loss increases as the generated current increases.
- the breakdown of loss is cathode reaction resistance, anode reaction resistance, polymer electrolyte membrane resistance, and the like. All of these losses turn into heat.
- the calorific value of the fuel cell is obtained by adding the calorific value due to the fuel crossover described above to the calorific value due to these losses. Therefore, in the power generation for preventing freezing, the point Psht obtained by shifting the point Pmax at which the maximum power generation efficiency is obtained in the fuel cell generated current-generated voltage characteristic curve shown in FIG. It is preferable to generate power from the fuel cell.
- the power generation amount of the fuel cell 12 may be constant over a predetermined temperature range in a range where the heat generation amount FGH due to power generation of the fuel cell 12 exceeds the required heat generation amount NHG. That is, the amount of power generation may be increased stepwise in response to changes in environmental temperature or battery temperature.
- the process proceeds to ST6 to execute the third anti-freezing operation while executing the second anti-freezing operation. If the battery temperature FT is not lowered, the third freeze prevention operation is not executed, the process proceeds to ST5, and the second freeze prevention operation is continued as it is.
- the storage amount of the storage battery 54 is monitored, and when the storage amount becomes equal to or less than the predetermined amount, the fuel cell 12
- the storage battery 54 may be charged by executing power generation.
- the remaining oxygen amount of the cathode may be reduced. Once activated, a sufficient amount of air may be sent to the cathode for heat generation due to fuel crossover.
- the system that performs all the first to third anti-freezing operations has been described.
- a system that executes only the first anti-freezing operation or the second anti-freezing operation respectively.
- a system that executes a combination of the first anti-freezing operation and the third anti-freezing operation or a system that executes a combination of the second anti-freezing operation and the third anti-freezing operation may be used.
- a system that executes a combination of the first anti-freezing path and the second anti-freezing operation can be used.
- the fuel cell when the temperature of the fuel cell falls below the reference value related to freezing of water while the power generation of the fuel cell is stopped, the fuel cell does not generate power without causing the fuel cell to generate power. Supply. As a result, fuel crossover occurs, and the fuel cell can be heated by the generated heat. Therefore, freezing of the fuel cell can be effectively prevented with a small amount of fuel consumption. In addition, if the fuel cell cannot be prevented from freezing only by the heat generated by the fuel crossover, the fuel cell is caused to generate power and thereby generate heat, so that the fuel cell can be more reliably prevented from freezing. it can.
- the fuel cell system of the present invention is useful, for example, as a power source for portable small electronic devices such as notebook personal computers, mobile phones, and personal digital assistants (PDAs), and for outdoor leisure and emergency backup power sources. Further, the fuel cell system of the present invention can be applied to uses such as a power source for electric scooters.
- portable small electronic devices such as notebook personal computers, mobile phones, and personal digital assistants (PDAs)
- PDAs personal digital assistants
- the fuel cell system of the present invention can be applied to uses such as a power source for electric scooters.
Abstract
Description
アノード:CH3OH+H2O → CO2+6H++6e- (11)
カソード:(3/2)O2+6H++6e- → 3H2O (12)
前記燃料を貯蔵する燃料タンクと、
前記燃料および水を含む燃料水溶液を前記アノードに供給する第1燃料供給装置と、
前記第1燃料供給装置に前記燃料タンクに貯蔵された燃料を供給する第2燃料供給装置と、
前記カソードに酸化剤を供給する酸化剤供給装置と、
前記燃料電池の温度FTを検出する温度センサと、
前記第1燃料供給装置、前記第2燃料供給装置、および前記酸化剤供給装置を制御するとともに、前記燃料電池の発電の開始および停止を制御する制御部とを備え、
前記制御部は、前記燃料電池が発電を停止した状態で、前記温度FTが水の凍結に関する第1基準温度以下であり、かつ第2基準温度以上であると、発電を停止した状態のままで、少なくとも前記第1燃料供給装置の供給動作を実行させる、燃料電池システムに関する。
Claims (6)
- 水溶性の燃料が供給されるアノード、酸化剤が供給されるカソード、および前記アノードと前記カソードとの間に介在される、水透過性を有する電解質膜、を含む燃料電池と、
前記燃料を貯蔵する燃料タンクと、
前記燃料および水を含む燃料水溶液を前記アノードに供給する第1燃料供給装置と、
前記第1燃料供給装置に前記燃料タンクに貯蔵された燃料を供給する第2燃料供給装置と、
前記カソードに酸化剤を供給する酸化剤供給装置と、
前記燃料電池の温度FTを検出する温度センサと、
前記第1燃料供給装置、前記第2燃料供給装置、および前記酸化剤供給装置を制御するとともに、前記燃料電池の発電の開始および停止を制御する制御部とを備え、
前記制御部は、前記燃料電池が発電を停止した状態で、前記温度FTが水の凍結に関する第1基準温度以下であり、かつ第2基準温度を超えているとき、発電を停止した状態のままで、少なくとも前記第1燃料供給装置の供給動作を実行させる、燃料電池システム。 - 前記第1基準温度が、0℃を超え、かつ5℃以下の第1温度T1であり、前記第2基準温度が、-5℃を超え、かつ-2℃以下の第3温度T3である、請求項1記載の燃料電池システム。
- 前記燃料がメタノールを含み、前記第1燃料供給装置が、0.2~0.5mol/Lの第1濃度FC1のメタノール水溶液を前記アノードに供給する、請求項2記載の燃料電池システム。
- 前記第1基準温度が、-2℃を超え、かつ0℃以下の第2温度T2であり、前記第2基準温度が、-5℃を超え、かつ-2℃以下の第3温度T3であり、
前記制御部は、前記温度FTが前記第1基準温度以下であると、前記第1燃料供給装置および前記第2燃料供給装置の両方の供給動作を実行させる、請求項1記載の燃料電池システム。 - 前記燃料がメタノールを含み、前記第1燃料供給装置が、0.5~4mol/Lの第2濃度FC2のメタノール水溶液を前記アノードに供給する、請求項4記載の燃料電池システム。
- 前記制御部は、前記温度FTが、前記第2基準温度以下になると、前記第1燃料供給装置、前記第2燃料供給装置、および前記酸化剤供給装置に供給動作を実行させて、前記燃料電池を発電させる、請求項1~5のいずれか1項に記載の燃料電池システム。
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US14/007,297 US20140057190A1 (en) | 2011-12-28 | 2012-11-19 | Direct oxidation type fuel cell system |
DE112012001552.5T DE112012001552T5 (de) | 2011-12-28 | 2012-11-19 | Direktoxidationsbrennstoffzellensystem |
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JP2011288446 | 2011-12-28 |
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JP2018006033A (ja) * | 2016-06-28 | 2018-01-11 | ダイハツ工業株式会社 | 燃料電池システム |
JP2021190248A (ja) * | 2020-05-28 | 2021-12-13 | トヨタ自動車株式会社 | 燃料電池システム |
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JP6743774B2 (ja) | 2017-06-29 | 2020-08-19 | トヨタ自動車株式会社 | 燃料電池システム |
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- 2012-11-19 DE DE112012001552.5T patent/DE112012001552T5/de not_active Withdrawn
- 2012-11-19 US US14/007,297 patent/US20140057190A1/en not_active Abandoned
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