JP4651953B2 - Fuel cell system and method for starting fuel cell system - Google Patents

Description

The present invention relates to a fuel cell system including a solid polymer electrolyte membrane type fuel cell and a method for starting the fuel cell system .

  In a fuel cell, a solid polymer electrolyte membrane is sandwiched between an anode electrode and a cathode electrode to form a membrane electrode structure, and this membrane electrode structure is sandwiched between a pair of separators to form a cell (unit fuel cell) In this type of fuel cell, generally, a plurality of cells are stacked and used as a fuel cell stack.

  In this fuel cell, a fuel gas (for example, hydrogen gas) is supplied to the anode electrode, and an oxidant gas (for example, air containing oxygen) is supplied to the cathode electrode to perform a chemical reaction. It is taken out and used as direct current electric energy. At this time, at the cathode electrode, hydrogen ions, electrons, and oxygen react to generate water. Since this fuel cell has little influence on the environment, it has attracted attention as a driving source for vehicles.

The operating temperature of this type of fuel cell is governed by the heat resistant temperature of the solid polymer electrolyte membrane. Conventionally, a fluorine-based electrolyte material such as a perfluorosulfonic acid polymer is generally used as the solid polymer electrolyte membrane. In this case, the operating temperature of the fuel cell is about 70 ° C. to 80 ° C. Therefore, temperature control is performed by circulating a refrigerant (for example, a coolant) through a refrigerant passage provided in the fuel cell stack so that the fuel cell does not exceed the operating temperature due to heat generated during power generation during normal power generation.
In addition, when air is used as an oxidant gas, it is compressed by a compressor and supplied to the fuel cell. However, since the temperature of the air rises with the compression, the air is cooled to a predetermined temperature by a radiator and then supplied to the fuel cell. Supply.

By the way, this type of fuel cell has a problem of startability in a sub-freezing environment. That is, when the fuel cell is started in a sub-freezing environment, if the generated water generated in the cell is frozen as a result of power generation, there is a risk that power generation may be disabled.
In order to prevent the generated water from freezing, it has been considered that an external heat source is provided. However, if the external heat source is provided, the fuel cell system becomes complicated and large.
Therefore, a method of warming up the fuel cell stack itself using self-heating by power generation was considered, but in that case, the temperature rise of the cell due to self-heating due to power generation is not in time, and it occurs in the cell with power generation The generated water freezes, and the diffusion of the reaction gas is hindered by this freezing of the generated water, and the reaction gas cannot reach the solid polymer electrolyte membrane, which may cause a rapid voltage drop.

Therefore, at the time of cold start, there is a method of quickly warming up the fuel cell by supplying air heated by the compressor by bypassing the radiator and supplying it to the cathode electrode of the fuel cell without cooling. It is considered (for example, refer to Patent Document 1).
JP 2002-305013 A

Even when air compressed and heated by the compressor is supplied to the fuel cell by bypassing the radiator, it is necessary to prevent the solid polymer electrolyte membrane from being damaged by heat. It is necessary not to supply the air. Therefore, the temperature of the supplied air must be controlled by providing a flow rate control valve in a bypass passage for bypassing the radiator to adjust the flow rate, and the system becomes complicated.
Therefore, the present invention provides a fuel cell system that can be quickly warmed up only by switching the flow path of the supply air at the time of cold start, and a method for starting the fuel cell system .

In order to solve the above-mentioned problems, the invention according to claim 1 is directed to an anode electrode (for example, an anode in an embodiment described later) on both sides of a solid polymer electrolyte membrane (for example, a solid polymer electrolyte membrane 2a in an embodiment described later). Electrode 2b) and a cathode electrode (for example, cathode electrode 2c in the embodiments described later) have a power generation by an electrochemical reaction between fuel gas supplied to the anode electrode and oxygen in the air supplied to the cathode electrode. A fuel cell (for example, a fuel cell 2 in an embodiment to be described later), a fuel supply means for supplying fuel to the anode electrode (for example, a fuel supply means 20 in an embodiment to be described later), and a compressor for compressing air (for example, A main passage (for example, a compressor 6 in an embodiment described later) and a radiator (for example, a radiator 7 in an embodiment described later) An air passage (for example, a main passage 32 in an embodiment to be described later) and a bypass passage (for example, a bypass passage 33 in an embodiment to be described later) that bypasses the radiator to guide the air compressed by the compressor to the cathode , An air passage 31 in an embodiment to be described later), temperature detecting means for detecting or estimating the temperature of the fuel cell (for example, a temperature sensor 8 in an embodiment to be described later), and cooling the fuel cell to A fuel cell cooling means for controlling the operating temperature, and when the temperature detected or estimated by the temperature detection means is equal to or lower than a reference temperature, it is determined that the engine is cold starting, and when the temperature is determined to be cold, the fuel cell cooling is The cooling of the fuel cell by means is weakened, and the air compressed by the compressor is not circulated through the main passage but is circulated through the bypass passage. Control means (e.g., on-off valve in the embodiment described below V2 to V4, ECU 10) and, wherein the solid polymer electrolyte membrane, the temperature of the inflection point of the tensile storage modulus, the compression at the cold start It is a fuel cell system characterized by being formed of a material higher than the maximum value of the air temperature on the machine outlet side.
With this configuration, when the fuel cell is started at a low temperature below the reference temperature, air can be circulated through the bypass passage without being circulated through the main passage, and the air that has been compressed and heated by the compressor is cooled by the radiator. It becomes possible to supply to the cathode of a fuel cell without doing. Moreover, since the solid polymer electrolyte membrane is extremely excellent in heat resistance, even if the air flowing through the bypass passage is supplied to the fuel cell without special temperature control, the solid polymer electrolyte membrane is It is not damaged by heat.
At the same time, the cooling of the fuel cell by the fuel cell cooling means can be weakened.
The invention according to claim 2 is the invention according to claim 1, characterized in that the solid polymer electrolyte membrane is a polyarylene-based electrolyte material.
By comprising in this way, the heat resistance of a solid polymer electrolyte membrane can be made high.
According to the third aspect of the present invention, an anode electrode (for example, an anode electrode 2b in an embodiment to be described later) and a cathode electrode (for example, an anode electrode 2b in an embodiment to be described later) are provided on both sides of a solid polymer electrolyte membrane (for example, the polymer electrolyte membrane 2a in an embodiment to be described later). A fuel cell having a cathode electrode 2c in an embodiment described later and generating power by an electrochemical reaction between a fuel gas supplied to the anode electrode and oxygen in the air supplied to the cathode electrode (for example, an embodiment described later) Fuel cell 2 in the example, fuel supply means for supplying fuel to the anode electrode (for example, fuel supply means 20 in the embodiment described later), and a compressor for compressing air (for example, compressor 6 in the embodiment described later) ) And a radiator (e.g., radiator 7 in the embodiment described later) Path 32) and an air passage (for example, an embodiment to be described later) that has a bypass passage (for example, a bypass passage 33 in an embodiment to be described later) bypassing the radiator and guides the air compressed by the compressor to the cathode electrode. Air passage 31), temperature detecting means for detecting or estimating the temperature of the fuel cell (for example, temperature sensor 8 in an embodiment described later), and cooling the fuel cell to control the operating temperature of the fuel cell. Fuel cell cooling means and control means for switching the air passage to either the main passage or the bypass passage based on the temperature detected or estimated by the temperature detection means (for example, on-off valves V2 to V4 in the embodiments described later) ECU 10), and the solid polymer electrolyte membrane has a temperature at the inflection point of the tensile storage elastic modulus during the low temperature start. Supplying the fuel gas and the air to the fuel cell when the fuel cell system is started, in a fuel cell system formed of a material higher than the maximum air temperature at the compressor outlet side; Detecting or estimating the temperature of the fuel cell by the temperature detection means, comparing the detected or estimated temperature with a reference temperature and determining a low temperature start when the temperature is equal to or lower than the reference temperature, and the low temperature start When the control means switches to the bypass passage, the cooling of the fuel cell by the fuel cell cooling means is weakened. And a step of switching in order.
The invention according to claim 4 is characterized in that, in the invention according to claim 3, when the low temperature start is determined, the fuel cell is set in a power generation state and the generated power is supplied to a load.

According to the first to fourth aspects of the invention, when the fuel cell is started at a low temperature below the reference temperature, air can be circulated through the bypass passage without being circulated through the main passage. It is possible to supply the air to the cathode of the fuel cell without cooling it with a radiator. At the same time, the cooling of the fuel cell by the fuel cell cooling means can be weakened. As a result, it is possible to reliably prevent the generated water from freezing due to power generation at the time of low temperature start (at the time of warming below freezing point ) , and to quickly warm up the fuel cell.
Moreover, since the solid polymer electrolyte membrane can supply air to the fuel cell without temperature control due to flow control of air flowing through the bypass communication path is not damaged by heat, the control system is simplified .

Embodiments of a fuel cell system according to the present invention will be described below with reference to the drawings of FIGS. Note that the fuel cell system in this embodiment is an embodiment mounted on a fuel cell vehicle.
FIG. 1 is a schematic configuration diagram of a fuel cell system 1.
The fuel cell 2 is a stack formed by laminating a plurality of cells formed by sandwiching a solid polymer electrolyte membrane 2a made of polyarylene-based electrolyte material between an anode electrode 2b and a cathode electrode 2c (in FIG. 1, a single cell). When hydrogen gas as a fuel gas is supplied to the anode electrode 2b and air containing oxygen as an oxidant is supplied to the cathode electrode 2c, the hydrogen ions generated by the catalytic reaction at the anode electrode 2b become solid high. It passes through the molecular electrolyte membrane 2a and moves to the cathode electrode 2c, and generates an electric power by causing an electrochemical reaction with oxygen at the cathode electrode 2c, thereby generating water. A part of the generated water passes through the solid polymer electrolyte membrane 2a and also moves to the anode electrode 2b side.

  The hydrogen gas stored in the high-pressure hydrogen tank 3 flows through the hydrogen supply passage 21 and is supplied to the anode electrode 2b of each cell through the anode-side gas passage 2d in the fuel cell 2. The hydrogen supply passage 21 is provided with a pressure adjustment valve V1 that depressurizes the hydrogen gas in the high-pressure hydrogen tank 3 to adjust the pressure to a predetermined pressure.

Of the hydrogen gas supplied to the anode electrode 2 b of the fuel cell 2, the hydrogen gas that has not been used for power generation, that is, unreacted hydrogen is discharged from the fuel cell 1 as an anode offgas, passes through the anode offgas passage 22, and the ejector 4. The fresh hydrogen gas supplied from the high-pressure hydrogen tank 3 is joined to the anode electrode 2b of the fuel cell 2 again.
In this embodiment, the high-pressure hydrogen tank 3, the ejector 4, the hydrogen supply passage 21, the anode offgas passage 22, and the pressure adjustment valve V 1 constitute the fuel supply means 20.

  On the other hand, after the air is purified through the filter 5, it is compressed by the compressor (compressor) 6, flows through the air passage 31 and is introduced into the cathode gas passage 2 e in the fuel cell 2, and the cathode electrode of each cell. 2c. The air passage 31 includes a radiator 7 and a main passage 32 having opening / closing valves V2 and V3 before and after the radiator 7, and a bypass passage 33 that bypasses the radiator 7 and is connected in parallel to the main passage 32. The bypass passage 33 is also provided with an on-off valve V4. The on-off valves V2 to V4 constitute switching means for switching whether the compressed air flows to the main passage 32 or the bypass passage 33 by opening or closing these valves. The air passage 31 passes the air compressed by the compressor 6 The light is guided to the cathode electrode 2 c through one of the main passage 32 and the bypass passage 33.

After the air supplied to the cathode electrode 2c is used for power generation, it is discharged from the fuel cell 2 to the cathode offgas passage 34 as the cathode offgas, and is discharged through the pressure control valve V5. The supply air flow rate to the fuel cell 2 is mainly controlled by the rotational speed of the compressor 6, and the supply air pressure is mainly controlled by the opening degree of the pressure control valve V5.
A temperature sensor 8 for detecting the temperature of the cathode offgas is installed in the cathode offgas passage 34 at a portion upstream of the pressure control valve V5 and close to the outlet of the cathode gas passage 2e of the fuel cell 2. . The temperature of the cathode offgas immediately after flowing out from the outlet of the cathode side gas passage 2e is substantially equal to the internal temperature of the fuel cell 2. Therefore, the temperature sensor 8 determines the temperature of the fuel cell 2 from the temperature of the cathode offgas discharged from the fuel cell 2. It can be said that the temperature detecting means estimates the temperature.

The electric power obtained by the power generation of the fuel cell 2 is supplied to and consumed by a load 9 such as a vehicle driving motor.
The fuel cell system 1 includes an electronic control unit (ECU) 10, and an output signal from the temperature sensor 8 is input to the ECU 10, and the ECU 10 adjusts the compressor 6, the load 9, and the pressure adjustment according to the operating state of the fuel cell 2. The valve V1, the on-off valves V2 to V4, and the pressure control valve V5 are controlled.

In this fuel cell system 1, during steady power generation, control is performed so that the on-off valve V 4 of the bypass passage 33 is closed and the on-off valves V 2, V 3 of the main passage 32 are opened. Thus, during steady power generation, the air compressed by the compressor 6 flows through the main passage 32, is controlled at a predetermined air temperature by the radiator 7, and is supplied to the cathode electrode 2 c of the fuel cell 2.
Although not shown, the fuel cell 2 is provided with a refrigerant passage so that the coolant can be circulated as necessary, so that the fuel cell 2 does not exceed the operating temperature due to heat generated by power generation. Temperature controlled.
The fuel cell 2 uses a polyarylene-based electrolyte material for the solid polymer electrolyte membrane 2a. However, the temperature control range of the supply air during normal power generation is set to 70 to 95 ° C., and the operation of the fuel cell 2 is performed. The temperature is also set to 70-95 ° C.

In this fuel cell system 1, when the fuel cell 2 is started at a low temperature below a reference temperature (for example, 0 ° C.), the on-off valves V2 and V3 of the main passage 32 are closed and bypassed before the normal warm-up operation. Control is performed to open the on-off valve V4 of the passage 33, and the sub-freezing warm-up operation is performed. Thereby, the air compressed and heated by the compressor 6 flows through the bypass passage 33 and is supplied to the cathode electrode 2 c of the fuel cell 2. That is, at the time of warming up below the freezing point, air does not flow through the main passage 32, so that it is not cooled by the radiator 7, but is supplied to the cathode electrode 2c while being heated.
Therefore, high temperature air is supplied to the cathode electrode 2c at the time of warming up below freezing point. However, since the solid polymer electrolyte membrane 2a of the fuel cell 2 is formed of a polyarylene-based electrolyte material having excellent heat resistance, The molecular electrolyte membrane 2a is not damaged by heat. And the cell which comprises the fuel cell 2 can be heated by supplying high temperature air to the cathode electrode 2c, and the fuel cell 2 can be warmed up rapidly.

Further, at the time of warming up below freezing point, high-temperature air is supplied to the cathode electrode 2c via the bypass passage 33, and hydrogen is supplied to the anode electrode 2b of the fuel cell 2 to generate power in the fuel cell 2, and from the fuel cell 2 When the electric power is taken out, the cell can be warmed also by self-heating due to power generation, so that the warm-up can be further accelerated.
When power generation is performed at the time of warming up below freezing point, generated water is generated along with the power generation, but since the hot air is circulated through the cathode side gas passage 2e and warmed up, the generated water is not frozen. Therefore, it is possible to reliably prevent the generated water from freezing that accompanies power generation, and to quickly warm up even at a low temperature start.

Next, the cold start control in this embodiment will be described with reference to the flowchart of FIG. Note that when the ignition switch of the fuel cell vehicle is turned off, the on-off valves V2 and V3 are closed and the on-off valve V4 is open.
When the ignition switch of the fuel cell vehicle is turned on in step S11, the ECU 10 proceeds to step S12, supplies hydrogen gas from the high-pressure hydrogen tank 3 to the anode side gas passage 2d of the fuel cell 2, and operates the compressor 6. Then, the compressed air is supplied to the cathode electrode 2 c of the fuel cell 2 through the bypass passage 33. It should be noted that the supply air flow rate and supply air pressure at this time are very small and minute compared to the case where the normal warm-up operation is used as the reference flow rate and reference pressure. Further, the coolant is not circulated through the fuel cell 2.

In step S13, the temperature of the air discharged from the cathode gas passage 2e of the fuel cell 2 (hereinafter referred to as air outlet temperature) is detected by the temperature sensor 8.
In step S14, it is determined whether the air outlet temperature detected by the temperature sensor 8 exceeds a reference temperature (for example, 0 ° C.).
If the determination result in step S14 is “NO” (air outlet temperature ≦ 0 ° C.), the process proceeds to step S15 to hold the open state of the on-off valve V4 and to set the on-off valves V2 and V3 to the closed state. Hold. That is, in this case, since it is a cold start, the main passage 32 is shut off so that air does not flow through the radiator 7 and compressed by the compressor 6 in order to perform the sub-freezing warm-up operation prior to the normal warm-up operation. The heated high-temperature air is circulated through the bypass passage 33 and supplied to the cathode-side gas passage 2e of the fuel cell 2. Thereby, the cell which comprises the fuel cell 2 can be heated with the high temperature air which distribute | circulates the cathode side gas channel | path 2e, and the fuel cell 2 can be warmed up rapidly. The supply air flow rate during the sub-freezing warm-up operation is increased compared to the normal warm-up operation, and the supply air pressure during the sub-freezing warm-up operation is increased compared to the normal warm-up operation. Further, a very small amount of coolant is circulated through the fuel cell 2.

  And it progresses to step S16 from step S15, the fuel cell 2 is made into an electric power generation state by turning ON the load 9, and the obtained electric power is consumed with the load 9. FIG. Thereby, a cell can be warmed also by the self-heating by electric power generation. And it returns to step S13 from step S16, and repeats the process of steps S13-S16 until the determination result in step S14 becomes "YES".

  If the determination result in step S14 is “YES” (air outlet temperature> 0 ° C.), the process proceeds to step S17, and the on-off valve V4 is closed and the on-off valves V2, V3 are opened. That is, in this case, since it is not a low temperature start, the bypass passage 33 is shut off, the main passage 32 is opened, the air compressed and heated by the compressor 6 is passed through the radiator 7 and the temperature is controlled to a predetermined temperature, and the fuel is It is supplied to the cathode side gas passage 2e of the battery 2.

And it progresses to step S18 from step S17, and transfers to normal warm-up operation. In this embodiment, the normal warm-up operation is an operation in which hydrogen and air are supplied to the fuel cell 2 at a reference flow rate at a reference pressure to generate power, and the coolant circulation in the fuel cell 2 is also performed at the reference flow rate.
In this embodiment, the on-off valves V2 to V4 and the control means for switching the flow of air to the main passage 32 or the bypass passage 33 are realized by the ECU 10 executing a series of steps S13 to S17. Is done.

FIG. 3 shows a polyarylene-based electrolyte material, which is a material of the solid polymer electrolyte membrane 2a used in this embodiment, and a fluorine-based electrolyte material conventionally used as a material for a solid polymer electrolyte membrane (for example, It is a figure which compares and shows the measurement result of the tensile storage elastic modulus of a (perfluorosulfonic acid polymer).
In addition, the measuring method of the tensile storage elastic modulus is based on “JIS K 7244-4”, a strip-like film of 5 mm × 22 mm is used as a sample, a dynamic viscoelasticity measuring device is used, and the sample is less sag in a jig. The measurement was performed under the following measurement conditions.
[Measurement condition]
Frequency: 10Hz,
Strain: 0.05%
Initial Temp: Room temperature (+1 to 2 ° C)
Final Temp: 250 ° C
Ramp Rate: 2 ° C / min
The measurement was performed after confirming that the temperature was in a steady state, and the inflection point of the tensile storage elastic modulus E ′ was obtained from the measurement result.
From this measurement result, the temperature of the inflection point of the fluorine-based electrolyte material is about 80 ° C, whereas the temperature of the inflection point of the polyarylene-based electrolyte material is about 190 ° C. It can be seen that the heat resistance is extremely high.

  FIG. 4 is a graph showing an example of a change in actual gas temperature at the outlet of the compressor 6 when the cold start control is executed as described above. In this example, since the actual gas temperature at the outlet of the compressor 6 reaches about 90 ° C. at maximum, air close to 90 ° C. may be supplied to the fuel cell 2 even temporarily. Here, when the solid polymer electrolyte membrane is made of a fluorine-based electrolyte material, there is a risk that the solid polymer electrolyte membrane may be thermally damaged when air at around 90 ° C. is supplied. In the case of the fuel cell 2 of the example, the solid polymer electrolyte membrane 2a is formed of a polyarylene-based electrolyte material, and the temperature of the inflection point of the polyarylene-based electrolyte material is about 190 ° C. Even if air is supplied to the cathode electrode 2c, the solid polymer electrolyte membrane 2a is not thermally damaged.

  According to the fuel cell system 1 of this embodiment, at a low temperature start time, hydrogen is supplied to the fuel cell 2 and the compressor 6 is operated to control the opening / closing of the on-off valves V2 to V4. The fuel cell 2 can be quickly warmed up while preventing the generated water 2 from freezing. That is, it is not necessary to control the temperature by controlling the flow rate of the air flowing through the bypass passage 33, and the control is simplified.

[Other Examples]
The present invention is not limited to the embodiment described above.
For example, the temperature detection means may be constituted by a temperature sensor that directly detects the internal temperature of the fuel cell 2.
The on-off valves V2 to V4 constituting a part of the control means can be replaced with a switching valve provided at the connection portion between the main passage and the bypass passage 33.

It is a block diagram in one Example of the fuel cell system which concerns on this invention. It is a flowchart which shows the cold start control in the said Example. It is a figure which shows the heat resistance characteristic of a solid polymer electrolyte membrane material. It is a figure which shows the change of the air temperature of a compressor exit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 2 Fuel cell 2a Solid polymer electrolyte membrane 2b Anode electrode 2c Cathode electrode 6 Compressor
7 Radiator 8 Temperature sensor (temperature detection means)
10 ECU (control means)
20 Fuel supply means 31 Air passage 32 Main passage 33 Bypass passage V2 to V4 On-off valve (control means)

Claims (4)

A fuel cell that has an anode electrode and a cathode electrode on both sides of a solid polymer electrolyte membrane, and generates electricity by an electrochemical reaction between a fuel gas supplied to the anode electrode and oxygen in the air supplied to the cathode electrode;
Fuel supply means for supplying fuel to the anode electrode;
A compressor for compressing air;
An air passage having a main passage having a radiator and a bypass passage bypassing the radiator, and guiding the air compressed by the compressor to the cathode electrode;
Temperature detecting means for detecting or estimating the temperature of the fuel cell;
Fuel cell cooling means for cooling the fuel cell and controlling the operating temperature of the fuel cell;
When the temperature detected or estimated by the temperature detection means is below a reference temperature, it is determined that the engine is cold starting, and when it is determined that the engine is cold starting, the cooling of the fuel cell by the fuel cell cooling means is weakened, Control means for circulating the air compressed by the compressor through the bypass passage without flowing through the main passage ;
The solid polymer electrolyte membrane is formed of a material having a temperature at the inflection point of the tensile storage elastic modulus higher than the maximum value of the air temperature at the compressor outlet side at the time of the cold start. A fuel cell system.   The fuel cell system according to claim 1, wherein the solid polymer electrolyte membrane is a polyarylene-based electrolyte material. A fuel cell that has an anode electrode and a cathode electrode on both sides of a solid polymer electrolyte membrane, and generates electricity by an electrochemical reaction between a fuel gas supplied to the anode electrode and oxygen in the air supplied to the cathode electrode;
Fuel supply means for supplying fuel to the anode electrode;
A compressor for compressing air;
An air passage having a main passage having a radiator and a bypass passage bypassing the radiator, and guiding the air compressed by the compressor to the cathode electrode;
Temperature detecting means for detecting or estimating the temperature of the fuel cell;
Fuel cell cooling means for controlling the operating temperature of the fuel cell by cooling the fuel cell;
Control means for switching the air passage to either the main passage or the bypass passage based on the temperature detected or estimated by the temperature detection means;
And the solid polymer electrolyte membrane is made of a material whose temperature at the inflection point of the tensile storage elastic modulus is higher than the maximum value of the air temperature at the compressor outlet side at the time of cold start In the system,
At startup of the fuel cell system,
Supplying the fuel gas and the air to the fuel cell;
Detecting or estimating the temperature of the fuel cell by the temperature detecting means;
Comparing the detected or estimated temperature with a reference temperature and determining a low temperature start when the detected temperature is equal to or lower than the reference temperature;
When the low temperature start is determined, the control means switches to the bypass passage and the cooling of the fuel cell by the fuel cell cooling means is weakened. Switching to the main passage;
Are sequentially implemented. A method for starting a fuel cell system. 4. The method of starting a fuel cell system according to claim 3, wherein, when it is determined that the start is at a low temperature, the power generated by the fuel cell being in a power generation state is supplied to a load. 5.

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