JP4533604B2 - Low temperature startup method for fuel cells - Google Patents

Description

  The present invention relates to a fuel cell for starting a polymer electrolyte fuel cell in which an electrolyte membrane / electrode structure having a solid polymer electrolyte membrane disposed between a pair of electrodes and a separator are laminated at a temperature below freezing point. Relates to the cold start method.

  Generally, a polymer electrolyte fuel cell is an electrolyte membrane / electrode structure in which an anode side electrode and a cathode side electrode are disposed on both sides of an electrolyte membrane made of a polymer ion exchange membrane (solid polymer electrolyte membrane), respectively. Is sandwiched between separators. This type of fuel cell is normally used as a fuel cell stack by alternately stacking a predetermined number of electrolyte membrane / electrode structures and separators.

  In this fuel cell, a fuel gas supplied to the anode side electrode, for example, a gas mainly containing hydrogen (hereinafter also referred to as a hydrogen-containing gas) is ionized with hydrogen on an electrode catalyst, and is cathoded through an electrolyte membrane. Move to the side electrode side. Electrons generated during that time are taken out to an external circuit and used as direct current electric energy. The cathode side electrode is supplied with an oxidant gas, for example, a gas mainly containing oxygen or air (hereinafter also referred to as an oxygen-containing gas). And oxygen reacts to produce water.

  By the way, in this type of fuel cell, in order to maintain ionic conductivity, it is necessary to appropriately humidify the electrolyte membrane made of the polymer ion exchange membrane. Furthermore, water generated by the reaction is present at the cathode side electrode as described above. For this reason, it has been pointed out that if the fuel cell is started below the freezing point (below the freezing temperature of water), the water in the fuel cell is likely to be frozen and the electrochemical reaction is difficult to occur in the fuel cell. Yes.

  Therefore, for example, in Patent Document 1, an electrolyte membrane such as NAFION (registered trademark) manufactured by Dupont and an experimental membrane manufactured by Dow (product number XUX 13204.10) has a temperature of −20 ° C. It is disclosed that it is sufficiently ionically conductive to allow an electrochemical reaction in the fuel cell.

  This Patent Document 1 discloses a method for starting the operation of the fuel cell power generator from a temperature lower than the solidification temperature of water by using the above electrolyte membrane. The power generator includes a fuel cell stack that can be connected to the external electrical circuit to supply current to the external electrical circuit. The deposit includes at least one fuel cell, and the fuel cell includes a membrane electrode assembly including a positive electrode, a negative electrode, and a water-permeable ion exchange membrane inserted therebetween, The temperature of at least a part of the membrane electrode assembly is lower than the solidification temperature of water. The method includes a step of supplying a current from the deposit to the external electric circuit so that the temperature of a part of the membrane electrode assembly exceeds the solidification temperature of water.

JP 2000-512068A (FIG. 3)

  However, in Patent Document 1 described above, although the fuel cell can be operated even when the temperature is below the solidification temperature of water, the ionic conductivity of the electrolyte membrane is remarkably lowered when the fuel cell is started at a predetermined temperature or lower, and the desired value is obtained. There is a problem that it is difficult to quickly shift to the starting state.

  More specifically, there is a temperature characteristic in the ionic conductivity of a solid polymer electrolyte membrane usually used in a polymer electrolyte fuel cell, and the water inside the cluster responsible for proton transfer is, for example, It is confirmed that the ionic conductivity of the solid polymer electrolyte membrane is remarkably lowered by freezing in the range of -10 ° C to -30 ° C. For this reason, when starting the fuel cell from a temperature below the temperature at which the water inside the cluster starts to freeze, there is a problem that the current necessary for warming up the fuel cell cannot be taken out from the fuel cell itself.

  On the other hand, the fuel cell generates water by power generation, and water is always present inside the fuel cell. Therefore, when the internal temperature is lowered after the fuel cell is stopped and the water existing in the vicinity of the electrode catalyst layer is frozen, the effective area of the catalyst is lowered and the applicable current is reduced. At that time, it is known that the freezing temperature of water present in the extremely small pores such as the electrode catalyst layer fluctuates to 0 ° C. or less depending on the pore diameter. Therefore, when starting the fuel cell from below this freezing temperature, there is a possibility that the current required for warming up the fuel cell cannot be taken out from the fuel cell itself.

  Furthermore, if the temperature is higher than both the freezing temperature of the water inside the cluster and the freezing temperature of the water in the electrode pores, an initial load can be applied, but as the power generation proceeds, the generated water becomes the electrode. Easily freezes in the diffusion layer. As a result, there is a problem that the gas diffusibility is lowered and the cell voltage is lowered.

  The present invention solves this type of problem, and can perform a quick and reliable start even in an environment below the freezing temperature of water, and can effectively reduce the fuel consumption to enable efficient operation. It is an object of the present invention to provide a method for starting a battery at a low temperature.

  In the low temperature start-up method for a fuel cell according to the present invention, when it is detected that the temperature of the fuel cell is below freezing and below the reference temperature, the fuel cell is heated using an external heat source. Here, the reference temperature means that freezing of water inside the cluster of the solid polymer electrolyte membrane, freezing of water in the electrode catalyst layer, freezing of water in the electrode diffusion layer, etc. is likely to occur. The temperature at which self-warming by power generation becomes difficult. When the temperature of the fuel cell is equal to or lower than the reference temperature, the temperature of the fuel cell is increased by heating the fuel cell from the outside with an external heat source.

  Next, when the temperature of the fuel cell reaches the reference temperature, the heating by the external heat source is stopped and the fuel cell is heated only by the power generation of the fuel cell itself. Therefore, only the self-warming of the fuel cell is performed from the reference temperature. For example, when the fuel cell is used for in-vehicle use, traveling from 0 ° C. or less is started. This is because the output (electric power) obtained by the power generation of the fuel cell itself can be supplied to the traveling motor.

  Further, in the first temperature raising step, heating with only an external heat source may be performed in a state where power generation of the fuel cell is stopped, or heating with an external heat source may be performed while generating power with the fuel cell. Good.

  Further, the reference temperature is the freezing temperature of water stored in the cluster constituting the electrolyte membrane / electrode structure, the freezing temperature of water in the pores of the electrode catalyst layer constituting the electrolyte membrane / electrode structure, and It is preferable that the temperature is set to the highest temperature among the freezing temperatures of water determined by the heat capacity of the fuel cell and the generated water retention capacity of the electrolyte membrane / electrode structure.

  Furthermore, it is preferable to heat the entire fuel cell with an external heat source. Specifically, the fuel cell is configured by stacking a plurality of power generation cells, and is heated for each of the power generation cells by an external heat source, or is heated for each of the two or more power generation cells. The fuel cell may be configured by stacking a plurality of power generation cells, and may heat the power generation cells disposed at both ends in the stacking direction by an external heat source.

  Furthermore, it is preferable to heat the fuel cell by supplying a cooling medium heated by an external heat source to the fuel cell. Furthermore, the fuel cell is heated by an electric heater that is an external heat source, and the electric heater is supplied with electric power from the fuel cell, supplied with electric power from a battery, or supplied with electric power from a capacitor. preferable.

  Moreover, it is preferable to heat a fuel cell with the heating plate which is an external heat source, or to heat the fuel cell with the hydrogen combustion catalyst which is the external heat source. As the heating plate, for example, a configuration in which a liquid heating medium is sealed inside, a configuration in which a combustion catalyst is accommodated, or the like can be adopted.

  Further, the temperature of the fuel cell is obtained by measuring the coolant outlet temperature or coolant inlet temperature of the fuel cell, or by measuring the oxidant gas outlet temperature or oxidant gas inlet temperature of the fuel cell. In the fuel cell, one or more thermometers for measuring the temperature of the fuel cell are preferably incorporated.

  According to the present invention, when it is detected that the temperature of the fuel cell is below the freezing point and below the reference temperature, the fuel cell is heated using the external heat source. For this reason, the fuel cell is quickly and reliably heated to a temperature exceeding the reference temperature while preventing freezing of water.

  Next, when the temperature of the fuel cell reaches the reference temperature, heating by the external heat source is stopped, and the fuel cell is heated only by power generation of the fuel cell itself. Therefore, since only the fuel cell is self-warmed from the reference temperature, the amount of heat consumed by the external heat source is greatly reduced, which is economical. In addition, the external heat source can be easily reduced in size and weight, and efficient low-temperature startup can be performed.

  Furthermore, since the heating by the external heat source is stopped when the temperature of the fuel cell reaches the reference temperature, when the fuel cell is used for in-vehicle use, the temperature of the fuel cell is 0 ° C. or less. Can also start running. As a result, it is possible to start traveling immediately after the low temperature startup.

  FIG. 1 is an explanatory diagram of a schematic configuration of a fuel cell system 10 according to a first embodiment used in a method for starting a fuel cell at a low temperature according to the present invention.

  The fuel cell system 10 is mounted on a vehicle such as an automobile, and includes a solid polymer fuel cell 12. In the fuel cell 12, a plurality of power generation cells 14 are stacked in the direction of arrow A, and end plates 16a and 16b are disposed at both ends in the stacking direction with terminal plates 15a and 15b interposed therebetween. The end plates 16a and 16b are fastened in the stacking direction by fastening bolts (not shown).

  The power generation cell 14 includes an electrolyte membrane / electrode structure 24 in which a cathode-side electrode 20 and an anode-side electrode 22 are disposed on both sides of a solid polymer electrolyte membrane 18, and a pair of separators that sandwich the electrolyte membrane / electrode structure 24 26, 28. The separator 26 is formed with an oxidant gas flow path 30 for supplying, for example, air containing oxygen as the oxidant gas to the cathode side electrode 20. For example, a fuel gas passage 32 for supplying a hydrogen-containing gas as a fuel gas to the anode-side electrode 22 is formed on one surface of the separator 28, and between the power generation cells 14 on the other surface. A cooling medium flow path 34 for supplying the cooling medium is formed.

  The cooling medium flow path 34 communicates with the cooling medium supply system 36. The cooling medium supply system 36 includes a refrigerant tank 38 for storing the cooling medium and a circulation path 40, and the circulation path 40 communicates with the refrigerant tank 38 and the cooling medium flow path 34 of the fuel cell 12. Circulating the cooling medium. The refrigerant tank 38 is equipped with an electric heater (external heat source) 42 for heating the cooling medium.

  A power supply unit 44 is electrically connected to the terminal plates 15 a and 15 b constituting the fuel cell 12. The power supply unit 44 includes, for example, a load, a battery, a capacitor, and the like, and is electrically connected to the electric heater 42. The power supply unit 44 and the electric heater 42 are connected to a controller 46, and the controller 46 includes a first thermometer 48 provided in the fuel cell 12 and a second thermometer disposed in the refrigerant tank 38. Each temperature detection signal is input from 50.

  A plurality of the first thermometers 48 are arranged along the stacking direction of the power generation cells 14, and the coolant outlet temperature, coolant inlet temperature, oxidant gas outlet temperature, or oxidant gas inlet temperature of the fuel cell 12. Measure. Among the temperatures detected by the first thermometers 48, the lowest temperature is detected as the internal temperature of the fuel cell 12.

  Although not shown, the fuel cell 12 is connected to an oxidant gas supply system that supplies oxidant gas to the oxidant gas flow path 30 and a fuel gas supply system that supplies fuel gas to the fuel gas flow path 32. Has been.

  The operation of the fuel cell system 10 configured as described above will be described below along the flowchart shown in FIG.

  First, when a drive signal is input to the controller 46 (step S1), the process proceeds to step S2, and the internal temperature of the fuel cell (FC) 12 is measured via the first thermometer 48. The controller 46 receives temperature detection signals from a plurality of first thermometers 48, and the controller 46 uses the lowest temperature among the temperatures detected by the first thermometers 48 to use the fuel cell. The internal temperature of 12 is calculated (step S3).

  Next, whether the calculated internal temperature is below a freezing point (0 ° C. at 1 atm), that is, whether the fuel cell 12 is started in an environment where the internal temperature of the fuel cell 12 is below the freezing point of water. Is determined (step S4). If the internal temperature is below freezing (YES in step S4), the process proceeds to step S5, and it is determined whether or not the internal temperature is lower than the reference temperature.

  Here, the reference temperature is set to a predetermined temperature below the freezing point based on the requirements described below. First, the relationship between the internal temperature of the fuel cell 12 and the current value that can be extracted from the fuel cell 12 by power generation is shown in FIG. Accordingly, there is a temperature characteristic that the current value decreases as the internal temperature of the fuel cell 12 decreases, and the current value rapidly decreases at a certain temperature below freezing point. A certain temperature below the freezing point is the reference temperature, and in order to use the fuel cell 12 stably, it is necessary to raise the internal temperature of the fuel cell 12 to the reference temperature or higher.

  Next, when setting the reference temperature, the ionic conductivity of the solid polymer electrolyte membrane 18, the gas diffusibility of the electrolyte membrane / electrode structure 24, and the heat capacity of the fuel cell 12 are taken into consideration.

  In the solid polymer electrolyte membrane 18, as shown in FIG. 4, when the internal temperature of the fuel cell 12 reaches a temperature below the freezing point (reference temperature), the resistance overvoltage rapidly rises and power generation becomes difficult. As shown in FIG. 5, the water inside the cluster of the solid polymer electrolyte membrane 18 has a peak endothermic temperature at a temperature below the freezing point (reference temperature), for example, in the range of −10 ° C. to −30 ° C. This is because the water taken into the solid polymer electrolyte membrane 18 is frozen and the ionic conductivity is remarkably lowered.

On the other hand, water generated by power generation of the fuel cell 12 is present inside the electrolyte membrane / electrode structure 24. When the water present in the electrode catalyst layer is frozen, the effective catalyst area is remarkably lowered and the gas is reduced. Diffusivity decreases. At that time, the freezing temperature of water present in the micropores such as the electrode catalyst layer fluctuates to 0 ° C. or less depending on the pore diameter. this is,
[Delta] T _f (melting point drop ^{_{rate) = 2V m T f 0 σ}} / (ΔH f r)
r: capillary radius V _m : molar volume of water (18 cm ³ / mol)
T _f ⁰ : Freezing point of bulk water (273K)
σ: Ice-water interface free energy ΔH _f : Ice melting heat (79.4 cal / g = 6000 J / mol)
From this relationship, the gas diffusivity is significantly reduced below the freezing temperature of water.

  Furthermore, the temperature rise characteristic due to the difference in the heat capacity of the fuel cell 12 has the relationship shown in FIG. When the heat capacity of the fuel cell 12 is large, self-warming becomes difficult due to freezing of the produced water. In other words, it is difficult to self-warm the fuel cell 12 at a temperature lower than the limit temperature determined by the heat capacity of the power generation cell 14 and the generated water retention capacity of the electrolyte membrane / electrode structure 24.

  Therefore, as described above, the water freezing temperature inside the cluster of the solid polymer electrolyte membrane 18, the water freezing temperature inside the pores in the electrode catalyst layer of the electrolyte membrane / electrode structure 24, the heat capacity of the power generation cell 14 and the above-mentioned The highest temperature among the water freezing temperatures determined by the generated water holding capacity of the electrolyte membrane / electrode structure 24 is set as the reference temperature.

  Therefore, as shown in FIG. 2, when it is determined that the internal temperature of the fuel cell 12 is equal to or lower than the reference temperature (YES in step S5), the process proceeds to step S6 and shifts to the external warm-up mode. In the external warm-up mode, as shown in FIG. 1, electric power is supplied to the electric heater 42 from a battery or a capacitor constituting the power supply unit 44, and the electric heater 42 is heated.

  For this reason, the temperature of the cooling medium stored in the refrigerant tank 38 is raised, and this cooling medium is supplied to the cooling medium flow path 34 between the power generation cells 14 constituting the fuel cell 12 via the circulation path 40. Accordingly, each power generation cell 14 is heated by the heated cooling medium, and the controller 46 detects the temperature of the power generation cell 14 via the first thermometer 48 (step S2).

  As described above, when each power generation cell 14 is warmed up by the cooling medium heated by the electric heater 42 and the internal temperature of the fuel cell 12 exceeds the reference temperature (NO in step S5), step S7 is performed. The low-temperature mode power generation is started. In this low-temperature mode power generation, the fuel cell 12 generates power under power generation conditions that take into account the low-temperature startability of the fuel cell 12. Specifically, for example, air containing oxygen is supplied to the oxidant gas flow path 30 of each power generation cell 14 as an oxidant gas, and fuel gas is supplied to the fuel gas flow path 32 as, for example, A hydrogen-containing gas is supplied.

  Thus, in each power generation cell 14, oxygen-containing air is supplied to the cathode side electrode 20, while hydrogen-containing gas is supplied to the anode side electrode 22 to generate power, and the power generation cells 14 are stacked at both ends in the stacking direction. Power is supplied to the power supply unit 44 from the arranged terminal plates 15a and 15b. At that time, electric power is supplied to a load constituting the power supply unit 44 or a travel motor (not shown), and only the self-warming of the fuel cell 12 is performed. When the internal temperature of the fuel cell 12 becomes 0 ° C. or higher (NO in step S4), the mode shifts to normal mode power generation (step S8). In this normal mode power generation, the operation of the fuel cell 12 is performed under power generation conditions in consideration of fuel consumption and the like.

  In this case, in the first embodiment, when the internal temperature of the fuel cell 12 is below freezing and below the reference temperature, the fuel cell 12 is heated using the power supply unit 44. That is, below the reference temperature, it is difficult for the fuel cell 12 to start up by self-heating, so that heating by an external heat source is performed. Accordingly, the temperature of the fuel cell 12 is quickly and reliably increased while effectively preventing freezing of water by the cooling medium heated under the urging action of the electric heater 42 that is an external heat source.

  Next, when the internal temperature of the fuel cell 12 exceeds the reference temperature, heating by the electric heater 42 is stopped, while the fuel cell 12 generates power and the fuel cell 12 is heated only by self-warming. As a result, when the internal temperature of the fuel cell 12 reaches below the freezing point and above the reference temperature, only the self-warming of the fuel cell 12 is performed, so that the amount of heat consumed by the electric heater 42 as an external heat source is greatly reduced. And is economical.

  In addition, an external heat source such as the electric heater 42 can be easily reduced in size and weight, and an efficient low-temperature function can be performed. Further, when the internal temperature of the fuel cell 12 reaches the reference temperature, heating by the electric heater 42 is stopped. Thereby, when the fuel cell 12 is used for in-vehicle use, electric power can be reliably supplied to a traveling motor (not shown) even if the internal temperature of the fuel cell 12 is 0 ° C. or lower. Therefore, it is possible to start traveling immediately after the low temperature startup, and there is an advantage that the fuel cell system 10 can be shifted to the traveling mode as quickly as possible.

  FIG. 7 is a flowchart for explaining a second embodiment of the fuel cell low-temperature startup method according to the present invention.

  In this second embodiment, as in steps S1 to S5 in the first embodiment, the internal temperature of the fuel cell 12 is detected along steps S11 to S15, and this internal temperature is below the freezing point and below the reference temperature. When it is detected (YES in step S15), the process proceeds to step S16 and step S17, and the external warm-up mode and the low-temperature mode power generation are performed.

  That is, as shown in FIG. 1, air containing oxygen and a hydrogen-containing gas are supplied to the fuel cell 12 to generate power, and power is supplied from the power supply unit 44 to the electric heater 42 to heat the cooling medium. Is called. Accordingly, the temperature of the fuel cell 12 is raised through the cooling medium heated under the urging action of the electric heater 42 that is an external heat source, and the fuel cell 12 is self-warmed by power generation.

  Next, when the internal temperature of the fuel cell 12 is below the freezing point and equal to or higher than the reference temperature (NO in step S15), the process proceeds to step S18 where low-temperature mode power generation is performed and heating by the electric heater 42, which is an external heat source, is stopped. The Further, when the internal temperature of the fuel cell 12 becomes 0 ° C. or higher (NO in step S14), the process proceeds to step S19, and normal mode power generation is performed.

  As described above, in the second embodiment, when the internal temperature of the fuel cell 12 is equal to or lower than the reference temperature, heating by the external heat source (electric heater 42) and self-warming by the power generation of the fuel cell 12 itself are performed. Done. For this reason, the internal temperature of the fuel cell 12 can be quickly raised to a reference temperature or more, and the effect that the low-temperature start-up of the fuel cell system 10 can be performed more efficiently is obtained.

  FIG. 8 is an explanatory diagram of a schematic configuration of the fuel cell system 60 of the third embodiment used in the fuel cell low-temperature activation method according to the present invention. The same components as those of the fuel cell system 10 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Similarly, in the fourth and fifth embodiments described below, detailed description thereof is omitted.

  The fuel cell system 60 includes a heater heating unit 62 connected to the power supply unit 44, and a plurality of heat plates (heating plates) 64 are connected to the heater heating unit 62. As shown in FIG. 9, a liquid 66 as a heating medium is accommodated inside each heat plate 64, and a flow path 66 that circulates up and down is provided. The heat plate 64 has a heat input portion 68a at a joint portion with the heater heating portion 62, and a heat radiating portion 68b is provided at an end opposite to the heat input portion 68a. The heat plate 64 is disposed between the power generation cells 14.

  In the third embodiment configured as described above, the low-temperature startup is performed according to the flowchart shown in FIG. 2 (first embodiment) or the flowchart shown in FIG. 7 (second embodiment). At that time, when the internal temperature of the fuel cell 12 is equal to or lower than the reference temperature, electric power is supplied to the heater heating unit 62 via the power supply unit 44. Therefore, in each heat plate 64, the liquid inside is vaporized by the heat input part 68a, moves to the heat radiating part 68b through the flow path 66, and is radiated to each power generation cell 14 by this heat radiating part 68b.

  For this reason, the power generation cell 14 is heated via the heat plate 64 which is a heat conduction plate using the latent heat of the liquid. Then, when the internal temperature of the fuel cell 12 becomes equal to or higher than the reference temperature, the supply of electric power to the heater heating unit 62 is stopped, while the power generation of the fuel cell 12 is performed.

  As a result, the fuel cell 12 can be quickly and reliably heated to a temperature exceeding the reference temperature while preventing freezing of water, and the amount of heat consumed by the heater heating unit 62 is greatly reduced, which is economical. The same effects as those of the first and second embodiments can be obtained.

  In addition, in 3rd Embodiment, although the heat plate 64 is interposed for every power generation cell 14, it is not limited to this. For example, in the fuel cell system 60a shown in FIG. 10, the heat plate 64 is arranged for every two or more power generation cells 14, and in the fuel cell system 60b shown in FIG. A heat plate 64 is disposed in contact therewith.

  FIG. 12 is an explanatory diagram of a schematic configuration of a fuel cell system 70 of the fourth embodiment used in the fuel cell cold start method according to the present invention.

  The fuel cell system 70 includes an electric heater (external heat source) 72 connected to the power supply unit 44, and the electric heater 72 is disposed between the power generation cells 14. In addition, the electric heater 72 may be arrange | positioned for every 2 or more power generation cells 14, and may be arrange | positioned in contact with the power generation cells 14 arrange | positioned at the lamination direction both ends. Furthermore, although the electric heater 72 obtains electric power from the power supply unit 44 including a battery or a capacitor, the electric heater 72 may be configured to obtain electric power from the fuel cell 12.

  FIG. 13 is an explanatory diagram of a schematic configuration of a fuel cell system 80 according to a fifth embodiment used in the fuel cell cold start method according to the present invention.

  The fuel cell system 80 includes a hydrogen combustion heater plate 82 interposed in the fuel cell 12. The hydrogen combustion heater plate 82 incorporates a hydrogen combustion catalyst (not shown), and the hydrogen supply pipe 84 and the air supply pipe 86 are connected to the same end side, while the exhaust pipe 88 is different. Connected to the part. The hydrogen combustion heater plate 82 is disposed for each power generation cell 14, but is not limited thereto, and may be disposed for each of the two or more power generation cells 14, or at both ends in the stacking direction. You may arrange | position in contact with this electric power generation cell 14 arrange | positioned.

  In the fifth embodiment configured as described above, as in the first to fourth embodiments, when it is determined that the internal temperature of the fuel cell 12 is equal to or lower than the reference temperature, the hydrogen combustion heater that is an external heat source The power generation cell 14 is heated by the plate 82. Specifically, hydrogen is supplied from the hydrogen supply pipe 84 into each hydrogen combustion heater plate 82, and air is supplied from the air supply pipe 86 into the hydrogen combustion heater plate 82. For this reason, in the hydrogen combustion heater plate 82, a hydrogen combustion reaction is caused through the hydrogen combustion catalyst, and the temperature of each hydrogen generating heater plate 14 is increased by raising the temperature of the hydrogen combustion heater plate 82 itself.

  As a result, the fuel cell 12 is quickly and reliably heated above the reference temperature while preventing freezing of water, and is also heated to 0 ° C. only by self-warming by the power generation of the fuel cell 12. The same effect as in the fourth embodiment can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration explanatory diagram of a fuel cell system according to a first embodiment used in a fuel cell low-temperature startup method according to the present invention. It is a flowchart explaining the said low temperature starting method. FIG. 3 is an explanatory diagram of a relationship between an internal temperature of the fuel cell and an applicable current. FIG. 3 is an explanatory diagram of a relationship between an internal temperature of the fuel cell and a resistance overvoltage. It is explanatory drawing of the thermal characteristic of a solid polymer electrolyte membrane. It is explanatory drawing of the temperature rising characteristic by the difference in heat capacity. It is a flowchart of 2nd Embodiment explaining the low temperature starting method of the fuel cell which concerns on this invention. It is a schematic block diagram explaining the fuel cell system of 3rd Embodiment used for the low temperature starting method of the fuel cell which concerns on this invention. It is a partial perspective explanatory view of the heat plate and heater heating part which constitute the fuel cell system. It is explanatory drawing of the state by which the said heat plate was arrange | positioned for every some electric power generation cell. It is explanatory drawing of the state by which the said heat plate was arrange | positioned corresponding to the said power generation cell of the lamination direction both ends. It is a schematic block diagram explaining the fuel cell system of 4th Embodiment used for the low-temperature starting method of the fuel cell which concerns on this invention. FIG. 6 is a schematic configuration explanatory diagram of a fuel cell system according to a fifth embodiment used in the fuel cell low-temperature startup method according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 60, 60a, 60b, 70, 80 ... Fuel cell system 12 ... Fuel cell 14 ... Power generation cell 15a, 15b ... Terminal plate 16a, 16b ... End plate 18 ... Solid polymer electrolyte membrane 20 ... Cathode side electrode 22 ... Anode Side electrode 24 ... Electrolyte membrane / electrode structure 26, 28 ... Separator 30 ... Oxidant gas passage 32 ... Fuel gas passage 34 ... Cooling medium passage 36 ... Cooling medium supply system 38 ... Refrigerant tank 40 ... Circuit passage 42, 72 ... Electric heater 44 ... Power supply unit 46 ... Controller 48, 50 ... Thermometer 62 ... Heater heating unit 64 ... Heat plate 66 ... Channel 82 ... Hydrogen combustion heater plate 84 ... Hydrogen supply pipe 86 ... Air supply pipe 88 ... Exhaust pipe

Claims (17)

Low temperature start-up method of a fuel cell for starting a polymer electrolyte fuel cell in which an electrolyte membrane / electrode structure having a solid polymer electrolyte membrane disposed between a pair of electrodes and a separator are laminated at a temperature below freezing point Because
A first temperature raising step of heating the fuel cell using an external heat source when it is detected that the temperature of the fuel cell is below the freezing point and below a reference temperature lower than the freezing point ;
When the temperature of the fuel cell reaches the reference temperature, a second temperature raising step of stopping heating by the external heat source and heating the fuel cell only by power generation of the fuel cell itself;
A method for starting a fuel cell at a low temperature, comprising:   2. The low-temperature start-up method according to claim 1, wherein in the first temperature raising step, heating is performed only by the external heat source in a state where power generation of the fuel cell is stopped.   2. The low-temperature start-up method according to claim 1, wherein in the first temperature raising step, heating by the external heat source is performed while generating power in the fuel cell.   The low temperature starting method according to any one of claims 1 to 3, wherein the reference temperature is a freezing temperature of water stored in the cluster of the solid polymer electrolyte membrane, and constitutes the electrolyte membrane / electrode structure. Is set to the highest temperature among water freezing temperatures determined by the freezing temperature of water in the pores of the electrode catalyst layer and the heat capacity of the fuel cell and the water retention capacity of the electrolyte membrane / electrode structure. A method for starting a fuel cell at a low temperature. 2. The cold start method according to claim 1 , wherein the fuel cell is configured by stacking a plurality of power generation cells, and each of the power generation cells is heated by the external heat source. Method. 2. The low temperature start-up method according to claim 1 , wherein the fuel cell is configured by stacking a plurality of power generation cells, and is heated by the external heat source for every two or more power generation cells. Cold start method.   2. The cold start method according to claim 1, wherein the fuel cell is configured by stacking a plurality of power generation cells and heating the power generation cells disposed at both ends in the stacking direction by the external heat source. To start the fuel cell at low temperature.   2. The low temperature start-up method according to claim 1, wherein a cooling medium heated by the external heat source is supplied into the fuel cell to heat the fuel cell.   2. The cold start method according to claim 1, wherein the fuel cell is heated by an electric heater as the external heat source. 10. The low-temperature start-up method according to claim 9 , wherein electric power is supplied from the fuel cell to the electric heater. 10. The cold start method according to claim 9 , wherein electric power is supplied from a battery to the electric heater. 10. The cold start method according to claim 9 , wherein electric power is supplied to the electric heater from a capacitor.   2. The low temperature start-up method according to claim 1, wherein the fuel cell is heated by a heating plate as the external heat source.   2. The low-temperature startup method according to claim 1, wherein the fuel cell is heated by a hydrogen combustion catalyst as the external heat source.   2. The cold start method according to claim 1, wherein the temperature of the fuel cell is obtained by measuring a coolant outlet temperature or a coolant inlet temperature of the fuel cell.   2. The low-temperature start-up method according to claim 1, wherein the temperature of the fuel cell is obtained by measuring an oxidant gas outlet temperature or an oxidant gas inlet temperature of the fuel cell.   2. The cold start method according to claim 1, wherein a thermometer for measuring the temperature of the fuel cell is provided in the fuel cell.

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