JP2004228038A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system rising the temperature of a fusel cell at cold start, capable of obtaining a prescribed output within a short period at cold start. <P>SOLUTION: In the case that the output during temperature decrease is lower than the output during temperature increase, during warming-up, a thermal medium is circulated only at a part of respective cells 10a, and the part of respective cells 10a are intensively heated up to the temperature at which the ratio of the output during the temperature increase to the output during the temperature decrease reaches over a prescribed value, afterwards, remaining part of respective cells 10a are heated. Thus, the partial portions of respective cells 10a are quickly controlled to an environment suitable for a power generation operation, and it becomes possible to execute a stable power generation with a high output density within a short period at a partial position. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell system that generates electric energy by a chemical reaction between hydrogen and oxygen, and is effective when applied to moving objects such as vehicles, ships, and portable generators.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a fuel cell system that generates power using an electrochemical reaction between hydrogen and air (oxygen) has been known. In a fuel cell, water is generated internally with power generation. In a polymer electrolyte fuel cell having a polymer electrolyte membrane, water is supplied from the outside in order to improve the conductivity of the electrolyte membrane. In a low-temperature environment such as winter, there is a problem that the moisture present in these fuel cells freezes, and the fuel cells do not start or the output decreases.
[0003]
For this reason, for example, in a fuel cell system mounted on an electric vehicle, a method of keeping the fuel cell warm by an electric heater using an external heat source (commercial power supply or the like) in advance, or a method of mounting the heater on the vehicle and A method of raising the temperature of the fuel cell and the like have been adopted.
[0004]
[Problems to be solved by the invention]
FIG. 1 shows the output characteristics of the fuel cell with respect to the temperature of the fuel cell. In FIG. 1, (1) indicates the fuel under operating conditions (temperature: 80 ° C., humidity: 100%) at which the power generation efficiency of the fuel cell becomes high. This is an output characteristic in a temperature decreasing process when the temperature is decreased after operating the battery.
[0005]
(4) in FIG. 1 indicates that the fuel cell was operated under the above-described operating conditions under which the power generation efficiency of the fuel cell was high, the running point was stopped and cooled down to 0 ° C. or less, and then the temperature of the fuel cell was increased by increasing the ambient temperature. Is the output characteristic in the process of increasing the temperature when the operation is restarted in the state where the temperature becomes 0 ° C. or higher, and this output characteristic (4) is similar to the output characteristic (1).
[0006]
Further, (2) and (3) in FIG. 1 indicate that the fuel cell is cooled down to 0 ° C. or less after the operation under the above-mentioned operating conditions under which the power generation efficiency of the fuel cell is increased, and the fuel cell is operated in a low temperature environment of 0 ° C. or less. FIG. 6 shows output characteristics in a temperature rise process when the temperature of the fuel cell is 0 ° C. or higher when the temperature is higher than 0 ° C. Incidentally, the output characteristic (2) is obtained when the entire surface of the cell is simultaneously heated, and the output characteristic (3) is obtained by intensively arranging a part of the plurality of cells to a temperature at which moisture does not freeze. This is when a warming-up method is performed in which the remaining portions of the plurality of cells are heated after the heating.
[0007]
The output of the output characteristics (2) and (3) when the temperature of the fuel cell is 0 ° C. has a large fluctuation width with respect to the output of the output characteristic (1). This is because, when power is generated in a low-temperature environment, water generated by the power generation freezes on the catalyst layer and the diffusion layer of the fuel cell, so that the diffusion of the reaction gas is inhibited and the output of the fuel cell is reduced. Further, the output of the output characteristics (2) and (3) when the temperature is raised to 0 ° C. or higher does not recover to the output of the output characteristic (1). This is to stay in the layer.
[0008]
That is, when the fuel cell generates power in a low-temperature environment, the water generated by the power generation stays in the catalyst layer and the diffusion layer, so that the output of the fuel cell decreases and the temperature has hysteresis. However, when the temperature is raised to 60 ° C. to 70 ° C. at which the saturated vapor pressure becomes high, the generated water becomes steam and the discharge is promoted, so that the hysteresis becomes small in a high temperature range.
[0009]
The present invention has been made in view of the above points, and an object of the present invention is to provide a fuel cell system that raises the temperature of a fuel cell at a low temperature start so that a predetermined output can be obtained in a short time at a low temperature start.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a fuel cell having a plurality of stacked cells (10a) and obtaining electric power by electrochemically reacting hydrogen and oxygen in the cells (10a). (10), the output of the fuel cell (10) when the temperature decreases is defined as the output when the temperature is decreased, and the output of the fuel cell (10) when the temperature is increased is defined as the output when the temperature is increased. A fuel cell system having a hysteresis in which an output during temperature rise is lower than an hourly output, and when a fuel cell (10) is warmed up, a part of all cells (10a) is partially removed. After heating intensively to a temperature at which the ratio of the output at the time of temperature rise to the output at the time of temperature decrease becomes equal to or more than a predetermined value, the remaining portions of the plurality of cells (10a) are heated.
[0011]
According to this, since a part of the cell is intensively heated to a temperature at which the ratio of the output at the time of temperature rise to the output at the time of temperature decrease becomes equal to or higher than a predetermined value, some parts are promptly placed in a favorable environment for power generation. Is controlled. Therefore, stable power generation with a high output density can be executed in a short time in some parts, and as a result, a predetermined output can be obtained in a short time at a low temperature start.
[0012]
Further, the remaining portion can be heated by utilizing self-heating generated by power generation in some portions. As a result, the amount of heat required for the warm-up operation is reduced, so that the temperature of the fuel cell can be increased in a short time by a small heat source in a low-temperature environment.
[0013]
According to the second aspect of the present invention, a fuel cell (10) having a plurality of stacked cells (10a) and obtaining electric power by electrochemically reacting hydrogen and oxygen in the cells (10a) is provided. When the output of the fuel cell (10) at the time of temperature decrease is defined as the output at the time of temperature decrease, and the output of the fuel cell (10) at the time of temperature increase is defined as the output at the time of temperature rise, the output of the fuel cell is higher than the output at the time of temperature decrease. A fuel cell system having a hysteresis whose output is lower, wherein a first setting in which moisture is not frozen in a part of all of the plurality of cells (10a) when the fuel cell (10) is warmed up. A first warm-up method of heating the remaining portions of the plurality of cells (10a) after intensively heating to a temperature, and a heating operation of the plurality of cells (10a) when the fuel cell (10) is warmed up. Some parts of everything A second warming-up method of intensively heating to a second set temperature at which the ratio of the output at the time of temperature rise to the output at the time of temperature decrease becomes equal to or more than a predetermined value, and then heating the remaining portions in the plurality of cells (10a); Is selectively executed according to conditions.
[0014]
By the way, according to the first warming-up method, the power generation possible area can be quickly expanded, and according to the second warming-up method, stable power generation with high output density can be achieved in a part of the cell in a short time. It will be possible to do it at home. By selecting one of the two warm-up methods according to the conditions, a predetermined output can be obtained in a short time at a low temperature start under various conditions.
[0015]
In carrying out the invention of claim 2, the fuel cell (10) in a state where all parts of the plurality of cells (10a) are heated to the first set temperature as in the invention of claim 3 The estimated output and the estimated output of the fuel cell (10) in a state where all the parts of all of the cells (10a) are intensively heated to the second set temperature are described. It is possible to estimate when a part of all is intensively heated to the first set temperature, and compare the two estimated outputs to select one of the two warm-up methods.
[0016]
In the invention according to claim 4, a heat medium circulation path (20) for circulating the heat medium in each of the plurality of cells (10a) and a flow rate of the heat medium circulating in the heat medium circulation path (20) are controlled. Heating medium circulating means (24), a heating means (33) for heating the heating medium, and a heating medium circulating path (20), wherein the heating medium is provided only at a part of each of the plurality of cells (10a). And a flow path control means (31) for controlling a bypass flow rate of the heat medium by circulating the fluid and bypassing other parts.
[0017]
According to this, the heating medium heated to only a part of the cell by the bypass path can be circulated to perform partial heating. Further, after the concentrated heating of a part of the fuel cell is completed, the heat generated by the power generation can be transmitted to the entire fuel cell by circulating the heat medium throughout the fuel cell, thereby heating the entire fuel cell. According to such a configuration, it is possible to partially heat the fuel cell by adding only a few components to the cooling system conventionally provided in the fuel cell system.
[0018]
In addition, the code | symbol in the parenthesis of each said means shows the correspondence with the concrete means described in embodiment mentioned later.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. The fuel cell system according to the first embodiment is applied to an electric vehicle (fuel cell vehicle) that runs using a fuel cell as a power source.
[0020]
FIG. 2 shows the overall configuration of the fuel cell system according to the first embodiment. As shown in FIG. 2, the fuel cell system according to the first embodiment includes a fuel cell 10, a hydrogen supply device 12, an air supply device 13, heating and cooling systems 20 to 33, a control unit 40, and the like.
[0021]
The fuel cell (FC stack) 10 generates electric power using an electrochemical reaction between hydrogen and oxygen. In the first embodiment, a solid polymer electrolyte fuel cell is used as the fuel cell 10, and a plurality of cells 10a serving as basic units are stacked. Each cell 10a has a configuration in which an electrolyte membrane is sandwiched between a pair of electrodes. In the fuel cell 10, the supply of hydrogen and air (oxygen) causes the following electrochemical reaction between hydrogen and oxygen to generate electric energy.
(Hydrogen electrode ^{_{side) H 2 → 2H + + 2e}} -
(Oxygen electrode side) 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O
The fuel cell 10 is provided with current collecting plates 10b and 10c for taking out the generated power. The generated power is used for driving a driving motor (not shown) via an inverter (power conversion unit) 11 or for charging a secondary battery (not shown).
[0022]
The fuel cell 10 is configured so that hydrogen is supplied from a hydrogen supply device 12 and air containing oxygen is supplied from an air supply device 13. As the hydrogen supply device 12, for example, a reforming device or a hydrogen storage tank can be used, and as the air supply device 13, for example, an air compressor that is an adiabatic compressor can be used. Unreacted air not used for the reaction among the air supplied to the fuel cell 10 is discharged from the fuel cell 10 as exhaust gas. Unreacted hydrogen not used for the reaction among the hydrogen supplied to the fuel cell 10 is circulated and reused, although not shown.
[0023]
Due to a chemical reaction during power generation, the electrolyte membrane inside the fuel cell 10 needs to be in a state containing moisture. For this reason, hydrogen and air previously humidified by a humidifier (not shown) or the like are supplied to the fuel cell 10, and the electrolyte membrane in the fuel cell 10 is humidified.
[0024]
In the fuel cell 10, moisture and heat are generated by a chemical reaction during power generation. The fuel cell 10 needs to be maintained at a predetermined temperature (for example, about 80 ° C.) during operation in order to obtain high power generation efficiency. For this reason, the fuel cell system is provided with cooling systems 20 to 26 that release heat generated in the fuel cell 10 to the outside of the system by using a heat medium. In the first embodiment, antifreeze cooling water that does not freeze in a low-temperature environment is used as the heat medium.
[0025]
The cooling system is provided with a heat medium circulation path 20 for circulating cooling water through the fuel cell 10 and a radiator 21 as heat exchange means for cooling the cooling water. The cooling water that has passed through the fuel cell 10 circulates through the heat medium flow path 20 to the radiator 21, where it exchanges heat with outside air (atmosphere) and is cooled. The cooling water is configured to circulate inside each cell 10a constituting the fuel cell 10.
[0026]
The cooling system also includes a radiator bypass path 22 for bypassing the radiator 21 with the cooling water, a three-way valve 23 for switching the cooling water flow path to the radiator 21 or the radiator bypass path 22, and a heat medium for circulating the cooling water. A first water pump 24 as a circulating means, a first temperature sensor 25 for detecting a temperature of the cooling water flowing into the fuel cell 10 (hereinafter, referred to as an inlet temperature), and a temperature of the cooling water passing through the fuel cell 10 (hereinafter, an outlet) A second temperature sensor 26 for detecting the temperature. The second temperature sensor 26 can indirectly detect the entire temperature of the fuel cell 10.
[0027]
Further, in the fuel cell system of the first embodiment, heating systems 30 to 33 for raising the temperature of the fuel cell 10 for early start of the fuel cell 10 in a low temperature environment are provided. The heating system according to the first embodiment is provided integrally with the cooling system.
[0028]
The heat medium circulation path 20, which is a main path, includes a bypass path 30 that circulates cooling water only to a part of all the cells 10a (hereinafter, referred to as a local part of the cell 10a) and bypasses other parts. Is provided.
[0029]
The bypass path 30 is provided with a second water pump 31 for circulating cooling water. By controlling the rotation speed of the second water pump 31, the flow rate of the cooling water circulating in the bypass path 30, that is, the bypass flow rate can be controlled, and the second water pump 31 corresponds to the flow path control means of the present invention. .
[0030]
A third temperature sensor 32 that detects the temperature of the cooling water that has passed through the fuel cell 10 is provided near the outlet of the fuel cell 10 in the bypass path 30. By detecting the temperature of the cooling water by the third temperature sensor 32, the temperature of the portion of the fuel cell 10 heated by the heated cooling water, that is, the local temperature of the cell 10a (hereinafter referred to as the local temperature) is indirectly measured. Can be detected.
[0031]
The radiator bypass path 22 is provided with a heater 33 for heating the cooling water. The heater 33 corresponds to the heating means of the present invention, and an electric heater or a combustion heater can be used.
[0032]
The fuel cell system according to the first embodiment is provided with a control unit 40 that performs various controls. Sensor signals are input to the control unit 40 from the three temperature sensors 25, 26, and 32, and the inverter 11, the hydrogen supply device 12, the air supply device 13, the three-way valve 23, the first water pump 24, and the second water pump 31 , And outputs a control signal to the heater 33.
[0033]
Next, an operation (a warm-up operation method) of the fuel cell system having the above configuration at the time of starting in a low-temperature environment will be described with reference to a flowchart of FIG.
[0034]
First, the outlet temperature is detected by the second temperature sensor 26 (Step S10), and it is determined whether the outlet temperature is lower than the first set temperature (Step S11). Incidentally, the first set temperature is a temperature at which the fuel cell 10 can generate power without freezing of moisture, and is set to 0 ° C. in the first embodiment. When the outlet temperature is lower than the first set temperature, the fuel cell 10 is in a state in which power generation is not possible, so that a local warm-up operation for intensively raising the local temperature of the cell 10a is performed.
[0035]
First, the first water pump 24 and the second water pump 31 are operated to circulate the cooling water through the fuel cell 10 (step S12), and the heater 33 is operated to heat the cooling water (step S13). The fuel cell 10 is warmed up.
[0036]
Next, the local temperature is detected by the third temperature sensor 32 (Step S14). Further, the cooling water flow rate at which the inlet temperature detected by the first temperature sensor 25 reaches the target inlet temperature of 0 ° C. is calculated based on the temperature difference between the local temperature and the target inlet temperature and the amount of heating by the heater 33. The cooling water flow rate is controlled based on the calculation result (step S15).
[0037]
At this time, by controlling the rotation speeds of the two water pumps 24 and 31 so that the cooling water circulation amount of the heat medium circulation passage 20 and the cooling water circulation amount of the bypass passage 30 are matched, the heater 33 is heated. All the cooling water flows to the bypass path 30. Thus, in each of the cells 10a constituting the fuel cell 10, the cooling water can be circulated through only a part of the power generation surface, and only the local portion of the cell 10a can be intensively heated. In the first embodiment, the cooling water circulates only inside the fuel cell 10 on the upper side in FIG. As a result, it is possible to intensively raise the temperature only in the vicinity of the portion of the fuel cell 10 where the cooling water circulates.
[0038]
Next, the local temperature is detected by the third temperature sensor 32 (Step S16), and it is determined whether or not the local temperature is higher than the first set temperature (Step S17). Steps are performed until the local temperature reaches the first set temperature. S16 and S17 are repeated.
[0039]
Next, when the local temperature reaches the first set temperature, a second set temperature Tt of the local temperature detected by the third temperature sensor 32 is set (Step S18). Incidentally, when the output of the fuel cell 10 when the temperature decreases is the output at the time of temperature decrease, and when the output of the fuel cell 10 at the time of the temperature increase is the output at the time of temperature rise, the output at the time of temperature increase is lower than the output at the time of temperature decrease. However, the second set temperature Tt is a temperature at which the ratio of the output at the time of temperature rise to the output at the time of temperature decrease becomes equal to or higher than a predetermined value, and is set to 80 ° C. in the first embodiment.
[0040]
Next, the local temperature is detected by the third temperature sensor 32 (Step S19). Further, the cooling water flow rate at which the second set temperature Tt becomes 80 ° C. is calculated based on the temperature difference between the local temperature and the second set temperature Tt and the amount of heating by the heater 33, and based on the calculation result, The flow rate is controlled (Step S20).
[0041]
Next, the local temperature is detected by the third temperature sensor 32 (step S21), and it is determined whether the local temperature is higher than the second set temperature Tt (step S22), and the local temperature exceeds the second set temperature Tt. Steps S21 and S22 are repeated until the above. A portion of the fuel cell 10 where the local temperature exceeds the second set temperature Tt is a favorable environment for power generation, and stable power generation with a high output density is performed at that portion.
[0042]
The above steps S10 to S22 are the local warm-up operation. When the local temperature exceeds the second set temperature Tt, the local warm-up operation is terminated, and the chain warm-up operation is performed in step S23. Incidentally, the chain warm-up operation is to heat the remaining portion of the cell 10a after intensively raising the temperature of the cell 10a in the local warm-up operation.
[0043]
In step S23, the rotation speed of the first water pump 24 is increased, and the rotation speed of the second water pump 31 is reduced. Thereby, the amount of circulation of the cooling water in the heat medium circulation path 20 increases, and the amount of circulation of the cooling water in the bypass path 30 decreases. Therefore, the cooling water flows to a part other than the local part of the cell 10a, and the entire cell 10a is warmed up. . At this time, the heat generated by the power generation is transmitted to the entire cell 10a by the cooling water circulating inside the fuel cell 10. As a result, the entire cell 10a can be warmed up by effectively utilizing the self-heating accompanying the power generation in the local area of the cell 10a.
[0044]
After the entire cell 10a has been warmed up, the flow rate and temperature of the cooling water circulating in the heat medium circulation path 20 are controlled to maintain the fuel cell 10 at a predetermined temperature (about 70 to 80 ° C.) with good power generation efficiency. I do.
[0045]
According to the first embodiment, since a part of the cell 10a is intensively heated to a temperature at which the ratio of the output at the time of temperature rise to the output at the time of temperature decrease becomes equal to or more than a predetermined value. Is quickly controlled to a favorable environment. Therefore, stable power generation with a high output density can be executed in a short time in some parts, and as a result, a predetermined output can be obtained in a short time at a low temperature start.
[0046]
Further, the remaining portion can be heated by utilizing self-heating generated by power generation in some portions. As a result, the amount of heat required for the warm-up operation is reduced, so that the temperature of the fuel cell can be increased in a short time by a small heat source in a low-temperature environment.
[0047]
(2nd Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment differs from the first embodiment in the warm-up operation method, and the overall configuration of the fuel cell system is the same as the first embodiment.
[0048]
The operation at the time of starting (warm-up operation method) in a low-temperature environment according to the second embodiment will be described with reference to the flowchart of FIG. In FIG. 4, steps S10 to S17 are the same as in the first embodiment, and only the local part of the cell 10a is intensively heated until the local temperature of the fuel cell 10 reaches the first set temperature (0 ° C.).
[0049]
Next, the control unit 40 calculates the output of the fuel cell 10 when the local temperature reaches the first set temperature (step S31). Next, from the output calculated in step S31 and the temperature-output characteristic map stored in the control unit 40 in advance, a first estimated output P1 when the entire surface of the cell 10a becomes 0 ° C. is calculated (step S31). S32) Further, a second estimated output P2 when only the local portion of the cell 10a is heated to the second set temperature Tt is calculated (step S33).
[0050]
Next, the two estimated outputs P1 and P2 are compared (step S34), and if the first estimated output P1 is larger, the first warm-up method is executed (step S35), and the second estimated output P2 is larger. In this case, the second warming-up method is executed (Step S36).
[0051]
Incidentally, the first warming-up method shifts from the local warming-up operation to the chain warming-up operation when the local temperature of the fuel cell 10 reaches the first set temperature. According to the first warming-up method, The possible area can be quickly expanded. On the other hand, the second warming-up method shifts from the local warming-up operation to the chain warming-up operation when the local temperature of the fuel cell 10 reaches the second set temperature. It is possible to execute stable power generation with a high output density in a short time in a part of the portion 10a.
[0052]
According to the second embodiment, by selecting and executing the warming-up method having the larger estimated output, a predetermined output can be obtained in a short time at a low temperature start under various conditions.
[0053]
(Other embodiments)
In the above embodiments, the third temperature sensor 32 that detects the temperature of the cooling water is configured to indirectly detect the local temperature of the cell 10a. However, the present invention is not limited to this. A temperature sensor may be provided at a portion that is intensively heated during operation, and the local temperature of the cell 10a may be directly detected.
[0054]
Further, in each of the above embodiments, the heater 33 is provided in the radiator bypass path 22, but is not limited thereto, and may be provided on the heat medium circulation path 20 or the bypass path 30.
[0055]
Further, even if a four-way valve is arranged at the intersection of the heat medium circulation path 20 and the bypass path 30 instead of the second water pump 31, the same operation and effect as in the above embodiment can be achieved. That is, the flow rate can be distributed by opening and closing the four-way valve, and therefore, the same operation and effect as when the second water pump 31 is used can be achieved.
[Brief description of the drawings]
FIG. 1 is a diagram showing the relationship between the temperature of a fuel cell and output characteristics.
FIG. 2 is a conceptual diagram showing the entire configuration of the fuel cell system according to the first embodiment.
FIG. 3 is a flowchart showing the operation of the fuel cell system according to the first embodiment.
FIG. 4 is a flowchart showing the operation of the fuel cell system according to the second embodiment.
[Explanation of symbols]
10: fuel cell, 10a: cell, 33: heater (heating means).

Claims (4)

A fuel cell (10) having a plurality of stacked cells (10a) and obtaining electric power by electrochemically reacting hydrogen and oxygen in the cells (10a);
When the output of the fuel cell (10) at the time of temperature decrease is defined as the output at the time of temperature decrease, and the output of the fuel cell (10) at the time of temperature increase is defined as the output at the time of temperature rise, the output is lower than the output at the time of temperature decrease. A fuel cell system having hysteresis in which the output at the time of temperature rise is lower,
During the warm-up operation of the fuel cell (10), a part of all of the plurality of cells (10a) is set to a temperature at which the ratio of the output at the time of temperature rise to the output at the time of temperature decrease becomes a predetermined value or more. The fuel cell system according to claim 1, further comprising heating the remaining portions of the plurality of cells (10a) after intensive heating. A fuel cell (10) having a plurality of stacked cells (10a) and obtaining electric power by electrochemically reacting hydrogen and oxygen in the cells (10a);
When the output of the fuel cell (10) at the time of temperature decrease is defined as the output at the time of temperature decrease, and the output of the fuel cell (10) at the time of temperature increase is defined as the output at the time of temperature rise, the output is lower than the output at the time of temperature decrease. A fuel cell system having hysteresis in which the output at the time of temperature rise is lower,
When warming up the fuel cell (10), after intensively heating a part of all of the plurality of cells (10a) to a first set temperature at which moisture does not freeze, the plurality of cells (10a) are heated. A first warming-up method for heating the remaining part in 10a), and a temperature reduction in a part of all of the plurality of cells (10a) during the warm-up operation of the fuel cell (10). A second warming-up method of heating the remaining portion of the plurality of cells (10a) after intensively heating to a second set temperature at which the ratio of the temperature rise output to the hourly output becomes a predetermined value or more. And a fuel cell system selectively executed according to conditions. The estimated output of the fuel cell (10) in a state where all parts of the plurality of cells (10a) are heated to the first set temperature, and a part of all parts of the plurality of cells (10a) are The estimated output of the fuel cell (10) in a state where the fuel cell (10) is intensively heated to the second set temperature is obtained by partially arranging some of the plurality of cells (10a) to the first set temperature. 3. The fuel cell system according to claim 2, wherein the estimation is performed at the time of heating, and the two estimated outputs are compared to select one of the two warm-up methods. 4. A heat medium circulation path (20) for circulating a heat medium in each of the plurality of cells (10a);
A heat medium circulating means (24) for controlling a flow rate of the heat medium circulating in the heat medium circulation path (20);
Heating means (33) for heating the heat medium;
A bypass path (30) provided in the heat medium circulation path (20), for circulating the heat medium only in a part of each of the plurality of cells (10a) and bypassing other parts;
The fuel cell system according to any one of claims 1 to 3, further comprising a flow path control unit (31) for controlling a bypass flow rate of the heat medium.

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