JP2005150025A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of maintaining water balance in a good condition by suppressing water discharged outside. <P>SOLUTION: In this fuel cell system, water contained in the discharged air discharged from an air outlet of the fuel cell stack 1A is transferred to compressed air supplied to an air inlet of the fuel cell stack 1A by a membrane type humidifier 4 when fuel gas and oxidation gas are supplied to a fuel cell by controlling oxidation gas pressure and fuel gas pressure according to an output required by a fuel cell stack 1A generating using hydrogen gas and air. A discharged air temperature is detected, and an output limiting circuit 21 performs output limiting, so that the higher the temperature of the discharge air is, the lower the maximum output of the fuel cell stack 1A is. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell system that supplies fuel gas and oxidant gas to a fuel cell to generate power.

  Conventionally, as described in Patent Document 1 below, a humidifier (WRD (Water Recovery Device)) having a water-permeable hollow fiber membrane is provided in a gas supply side pipe and a gas discharge side pipe of a fuel cell. Fuel cell systems are known.

In the system described in Patent Document 1, moisture is moved by a humidifier to move the moisture from the high-humidity gas discharged from the fuel cell to the low-humidity gas directed to the fuel cell, thereby humidifying the fuel cell. ing.
JP 2002-216815 A

  However, in the conventional technology described above, when the amount of power generated by the fuel cell increases and the temperature of the fuel cell rises, the amount of water vapor contained in the cathode offgas, which is the oxidant gas discharged from the fuel cell, increases. Moisture contained in the cathode off gas cannot be completely collected by the humidifier. Therefore, the conventional technique has a problem that the amount of water discarded to the outside in the state of being included in the cathode off gas increases, and the water balance of the entire system is deteriorated.

  Therefore, the present invention has been proposed in view of the above-described circumstances, and an object of the present invention is to provide a fuel cell system that can suppress water discharged to the outside and maintain a water balance in a good state. And

  In the fuel cell system according to the present invention, the oxidant gas pressure and the fuel gas pressure supplied to the fuel cell are adjusted by the gas supply means according to the output required for the fuel cell that generates power using the fuel gas and the oxidant gas. When fuel gas and oxidant gas are supplied to the fuel cell under control, the moisture contained in the oxidant gas discharged from the oxidant gas outlet of the fuel cell by the humidifier is supplied to the fuel cell by the gas supply means. It moves to the oxidizing gas supplied to the oxidizing gas inlet.

  At this time, the fuel cell system according to the present invention detects the temperature of the oxidant gas discharged from the oxidant gas outlet of the fuel cell by the oxidant gas temperature detection means, and the oxidant gas temperature detection means by the output limiting means. The above-mentioned problem is solved by performing output restriction that lowers the maximum output of the fuel cell as the oxidant gas temperature detected by (1) increases.

  According to the fuel cell system of the present invention, the output is limited so that the maximum output of the fuel cell is lowered as the temperature of the exhaust oxidant gas of the fuel cell is higher. The moisture sent from the battery to the humidifier can be reduced. Therefore, according to this fuel cell system, it is possible to suppress moisture that passes through the humidifier and is discharged to the outside, and the water balance can be maintained in a good state.

  Hereinafter, first to third embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
The present invention is applied to the fuel cell system according to the first embodiment configured as shown in FIG. 1, for example.

[Configuration of fuel cell system]
As shown in FIG. 1, the fuel cell system includes a fuel cell main body 1 that generates electric power when supplied with a fuel gas and an oxidant gas. The fuel cell main body 1 includes a fuel cell structure in which a fuel cell structure in which an air electrode and a hydrogen electrode are opposed to each other with a solid polymer electrolyte membrane interposed therebetween is sandwiched between separators, and a plurality of cell structures are stacked. 1A. In this example, a fuel cell system in which the fuel cell stack 1A supplies hydrogen gas as a fuel gas for generating a power generation reaction to the hydrogen electrode and supplies air containing oxygen as an oxidant gas to the air electrode will be described. .

  The fuel cell body 1 humidifies air supplied to the fuel cell stack 1A using moisture stored in a pure water tank 13 described later, and air and hydrogen gas discharged from the fuel cell stack 1A. The gas-liquid separator 1 </ b> B (PSS) that has a mechanism for removing a part of the water contained in the water and sends condensed water to the pure water tank 13 is provided. The fuel cell main body 1 is configured by integrating a fuel cell stack 1A and a gas-liquid separator 1B.

  In this fuel cell system, an air supply system that supplies humidified air to the air electrode of the fuel cell stack 1A, a hydrogen supply system that supplies hydrogen gas to the hydrogen electrode of the fuel cell stack 1A, and air supplied to the fuel cell stack 1A. A pure water circulation system is provided for humidification. In such a fuel cell system, the state of each part to be described later is read into the output control circuit 21 and controlled by the output control circuit 21 and the vehicle controller 22.

  In the air supply system, a compressor 2, an aftercooler 3 and a membrane humidifier (WRD) 4 are provided in an air supply pipe L1 connected to an air inlet 1a of the fuel cell main body 1, and an air outlet 1b of the fuel cell main body 1 is provided. A membrane type humidifier 4 is provided in the connected air discharge pipe L2, and an air pressure adjusting valve 5 and an actuator 6 are provided in the external discharge pipe L3. The membrane humidifier 4 collects moisture contained in the discharged air discharged from the fuel cell main body 1, and moves the collected moisture to compressed air that supplies the fuel cell stack 1A. Thus, the membrane humidifier 4 increases the humidity of the compressed air supplied to the fuel cell stack 1A.

  In such an air supply system, the air is introduced into the compressed air inlet 4 a of the membrane humidifier 4 after the atmosphere is pressurized by the compressor 2 and cooled by the aftercooler 3. The air introduced into the compressed air inlet 4a is humidified by moisture and then discharged from the compressed air outlet 4b and sent to the gas-liquid separator 1B.

  The gas-liquid separator 1 </ b> B is supplied with compressed air, and pure water is circulated from the pure water tank 13 through a pure water circulation pipe constituting a pure water supply system. When the compressed air is supplied, the gas-liquid separator 1B humidifies the compressed air with pure water from the pure water tank 13 to further increase the humidity and supplies it to the fuel cell stack 1A.

  In the compressed air supplied to the fuel cell stack 1A, oxygen is used for the power generation reaction, the temperature is increased by the heat generated in the fuel cell stack 1A, the saturated water vapor amount is increased, and the humidity is further increased. The air is sent to the gas-liquid separator 1B. And exhaust air is cooled with the gas-liquid separator 1B, and temperature falls, and saturated water vapor | steam amount falls. Thereby, the gas-liquid separator 1B collects the condensed water generated by condensing a part of the moisture contained in the discharged air in the pure water tank 13 through the pure water circulation pipe.

  The exhaust air from which part of the moisture has been removed in this way is introduced into the exhaust air inlet 4c of the membrane humidifier 4 via the air outlet 1b and the air exhaust pipe L2, and the moisture remaining in the membrane humidifier 4 Is recovered and discharged from the membrane humidifier 4 d to the external discharge pipe L 3 and discharged to the outside via the air pressure adjustment valve 5.

  The hydrogen supply system includes a hydrogen tank 7, a hydrogen heater 8, and an ejector 9 provided in a hydrogen supply pipe L 4 connected to the hydrogen inlet 1 c of the fuel cell main body 1, and a hydrogen circulation connected to the hydrogen outlet 1 d of the fuel cell main body 1. A separator tank 10 and an ejector 9 are provided in the pipe L5, and a separator tank 10, a purge valve 11 and an actuator 12 are provided in a gas discharge pipe L6 for releasing hydrogen gas.

  In such a hydrogen supply system, hydrogen gas is introduced from the state stored in the hydrogen tank 7 into the hydrogen inlet 8a of the hydrogen heater 8 through the hydrogen outlet 7a, and the hydrogen heater 8 generates power in the fuel cell stack 1A. The temperature is set to a temperature suitable for the discharge from the hydrogen outlet 8 b and supplied to the ejector 9. The ejector 9 normally mixes the hydrogen gas from the hydrogen heater 8 and the gas from the hydrogen outlet 1d of the fuel cell stack 1A and supplies the mixed gas to the hydrogen inlet 1c of the fuel cell stack 1A. Here, the gas discharged from the hydrogen outlet 1d of the fuel cell stack 1A includes not only hydrogen but also nitrogen and water vapor. Therefore, the hydrogen supply system mixes the dry hydrogen gas that has passed through the hydrogen heater 8 and the gas that has passed through the fuel cell stack 1A and has become wet into the fuel cell stack. Supply to 1A.

  In the hydrogen gas supplied to the fuel cell stack 1A, hydrogen is used for the power generation reaction, the temperature rises due to heat generation in the fuel cell stack 1A, the saturated water vapor amount rises, and the humidity further rises. It is sent to the liquid separator 1B. Then, the hydrogen gas is cooled by the gas-liquid separator 1B, whereby the temperature is lowered and the saturated water vapor amount is lowered. As a result, the gas-liquid separator 1B causes the pure water tank 13 to collect the condensed water generated by the condensation of a part of the moisture contained in the hydrogen gas via the pure water circulation pipe.

  Thus, the hydrogen gas that has passed through the gas-liquid separator 1B is discharged from the hydrogen outlet 1d of the fuel cell stack 1A and sent to the hydrogen inlet 10a of the separator tank 10. The separator tank 10 generates condensed water by cooling the hydrogen gas sent from the hydrogen outlet 1d, collects a part of the water contained in the hydrogen gas, and passes from the hydrogen outlet 10b to the ejector 9 as a circulating gas. send.

  In this hydrogen supply system, the actuator 12 is controlled so that the purge valve 11 is opened when impurities other than hydrogen, such as nitrogen and water vapor, accumulate in the gas circulated in the fuel cell stack 1A. As a result, the hydrogen supply system supplies the gas circulated to the fuel cell stack 1A to the combustor, the fan, and the like via the separator tank 10 and the purge valve 11 and discharges them to the outside.

  Furthermore, the pure water circulation system includes a pure water pump (not shown) and the like, and drives the pure water pump to introduce pure water stored in the pure water tank 13 into the pure water inlet 1e of the gas-liquid separator 1B. Then, the pure water is circulated to the gas-liquid separator 1B, or the condensed water removed from the air and hydrogen gas that has passed through the fuel cell stack 1A by the gas-liquid separator 1B is collected in the pure water tank 13 from the pure water outlet 1f.

  In such a fuel cell system, the gas / liquid separator 1B and the membrane humidifier 4 sufficiently recover the moisture contained in the air and hydrogen gas, so that the moisture discarded outside via the air pressure regulating valve 5 is removed. The output control circuit 21 executes an output restriction process for restricting the maximum output value of the fuel cell stack 1A in order to suppress the water balance in the entire system and improve the water balance. The output control circuit 21 stores a program describing a processing procedure for executing the output restriction process in an internal ROM (Read Only Memory) or the like, and executes the program by a CPU (Central Processing Unit) or the like.

  In order to perform the output restriction process in this way, the fuel cell system includes various sensors for detecting the state of each part by the output control circuit 21. Specifically, the fuel cell system includes an air pressure sensor 31 and an air temperature sensor 32 provided in an air discharge pipe L2 connecting the gas-liquid separator 1B and the membrane humidifier 4, a fuel cell stack 1A, and a separator tank. 10 is provided with a hydrogen temperature sensor 33 provided in a hydrogen circulation pipe L5 connecting to the water 10, a water level sensor 34 provided in the pure water tank 13, and an output sensor 35 for detecting the power generation amount (output) of the fuel cell body 1. The output control circuit 21 performs processing for reading various sensor signals. The detailed contents of this output restriction process will be described later.

[Output restriction processing]
Next, in the fuel cell system configured as described above, the output control circuit 21 limits the maximum output of the fuel cell stack 1A in order to improve the water balance of the entire system by the output control circuit 21. Will be described with reference to the flowchart shown in FIG.

  In this output limiting process, the maximum output is set according to the amount of power generation required for the fuel cell stack 1A, the air pressure, the air flow rate, the hydrogen pressure and the hydrogen flow rate are adjusted, and the air and hydrogen gas are supplied to the fuel cell stack 1A. For example, it is executed every predetermined period when the power generation reaction is performed.

  First, in step S1, the sensor signal from the air temperature sensor 32 and the sensor signal from the output sensor 35 are read by the output control circuit 21, and the exhaust air temperature of the fuel cell body 1 and the output value of the fuel cell body 1 are calculated. To detect.

  In the next step S2, whether the air temperature detected in step S1 by the output control circuit 21 is higher than the water balance establishment upper limit temperature that changes according to the output value of the fuel cell body 1 detected in step S1. Determine whether or not. At this time, the output control circuit 21 refers to an output restriction table describing the relationship between the output of the fuel cell stack 1A and the water balance establishment upper limit temperature as shown in FIG.

  This water balance establishment upper limit temperature varies depending on the output value of the fuel cell stack 1A, that is, the amount of heat generated according to the amount of power generated in the fuel cell stack 1A. That is, this water balance establishment upper limit temperature is a state in which moisture released from the membrane humidifier 4 to the outside through the air pressure adjustment valve 5 is suppressed, and the water balance discharged from the air pressure adjustment valve 5 is small. The air temperature between the state in which the air pressure is positive and the state in which the amount of water discharged from the air pressure adjustment valve 5 is large and the water balance is negative has been obtained in advance by experiments or the like.

  Thereby, the output control circuit 21 obtains the water balance establishment upper limit temperature according to the current output value of the fuel cell main body 1, and when it is determined that the current air temperature is not higher than the water balance establishment upper limit temperature, When the water balance is positive, it is determined that there is not much pure water to be discharged and the water balance is established, and the process returns to step S1. On the other hand, if the output control circuit 21 determines that the current air temperature is higher than the water balance establishment upper limit temperature, there is a large amount of pure water to be discharged, and the water balance is negative, so that the entire system may run out of pure water. The process proceeds to step S3.

  In step S3, the output control circuit 21 limits the maximum output of the fuel cell main body 1 so that the temperature of the exhaust air of the fuel cell main body 1 detected by the air temperature sensor 32 is lower than the water balance establishment upper limit temperature. To do.

  At this time, in the output control circuit 21, the vehicle controller 22 lowers the opening of the air pressure adjustment valve 5 to lower the air pressure and the air flow rate in the fuel cell stack 1A, and the purge valve 11 is opened. A process of limiting the hydrogen pressure and the hydrogen flow rate in the fuel cell stack 1A is performed. Thereby, in the output control circuit 21, the temperature of the fuel cell stack 1A is lowered by lowering the maximum output of the fuel cell main body 1, and the temperature of the exhaust air of the fuel cell main body 1 is lowered.

[Effect of the first embodiment]
As described above in detail, according to the fuel cell system according to the first embodiment to which the present invention is applied, the maximum output value of the fuel cell stack 1A is lowered as the temperature of the exhaust air from the fuel cell body 1 is higher. Thus, the amount of heat generated from the fuel cell stack 1A can be suppressed, and the moisture sent from the fuel cell stack 1A to the gas-liquid separator 1B can be reduced. Therefore, according to this fuel cell system, moisture that passes through the membrane humidifier 4 and is discharged to the outside can be suppressed, and consumption of pure water stored in the pure water tank 13 is increased. Without deteriorating the water balance. Further, according to this fuel cell system, by limiting the maximum output of the fuel cell stack 1A, it is possible to reduce the amount of water generated by the power generation reaction of the fuel cell stack 1A.

  Here, the fuel cell system described above controls the output value of the fuel cell stack 1A by uniquely controlling the air pressure and the air flow rate according to the output value required for the fuel cell stack 1A. By making use of the fact that the air temperature range in which the water balance is established for the output value of 1A is uniquely determined, the water balance in the entire system can be established reliably.

  On the other hand, when the maximum output of the fuel cell stack is limited by the cooling medium temperature such as LLC, the influence of the deviation between the air temperature discharged from the fuel cell stack and the cooling medium temperature is taken into consideration. It is necessary to provide an allowance for the cooling medium temperature when the output restriction of the fuel cell stack is executed. Therefore, according to the fuel cell system according to the first embodiment, it is possible to directly measure the exhaust air temperature of the fuel cell main body 1 and limit the maximum output of the fuel cell stack 1A. By comparing the water balance establishment upper limit temperature that minimizes the margin of the starting air temperature with the current air temperature, the output limit can be accurately and minimized.

[Second Embodiment]
Next, a fuel cell system according to a second embodiment will be described. In addition, about the part similar to the above-mentioned 1st Embodiment, the detailed description is abbreviate | omitted by attaching | subjecting the same code | symbol. Moreover, since the structure of the fuel cell system according to the second embodiment is the same as that of the first embodiment, the description thereof is also omitted.

  The fuel cell system according to the second embodiment performs processing as shown in FIGS. 4 and 6 in the output restriction processing, so that not only the exhaust air temperature of the fuel cell body 1 but also the water balance in the entire system is related. This is different from the fuel cell system according to the first embodiment in that the limitation of the maximum output of the fuel cell stack 1A is executed using other parameters.

  This output restriction process is performed, for example, every predetermined period when power generation is performed in the fuel cell stack 1A. First, the output control circuit 21 detects the sensor signal from the air temperature sensor 32 in step S11 shown in FIG. Is detected, and the exhaust air temperature of the fuel cell body 1 is detected by reading the sensor signal from the air pressure sensor 31 in step S12.

  In the next step S13, the output control circuit 21 calculates the amount of water vapor contained in the exhaust air of the fuel cell body 1 using the air pressure and air temperature detected in steps S11 and S12. At this time, the output control circuit 21 calculates the amount of water vapor contained in the air by obtaining the saturated water vapor amount based on the exhaust air temperature and obtaining the water vapor partial pressure based on the air pressure within the range of the saturated water vapor amount. . Further, the output control circuit 21 detects a power generation amount (current value) of the fuel cell stack 1A by reading a sensor signal from the output sensor 35, and calculates a generated water amount of the fuel cell stack 1A corresponding to the current value. . Then, the output control circuit 21 collects the difference water amount obtained by subtracting the water vapor amount discharged together with the air from the generated water amount in the fuel cell stack 1A by the gas-liquid separator 1B in the pure water tank 13. Water recovery water amount A (= tank recovery amount A).

  In the next step S14, the map data as shown in FIG. 5 prepared in advance is referred to by the output control circuit 21 from the air flow rate supplied to the fuel cell main body 1 based on the rotational speed of the compressor 2, for example. Then, the water recovery amount B (= WRD recovery amount B) in the membrane humidifier 4 is obtained. Here, the map data shown in FIG. 5 is set to data in which the water recovery amount of the membrane humidifier 4 increases linearly as the air flow rate supplied to the membrane humidifier 4 increases. It is required by experiments when designing the fuel cell system.

  In the next step S15, the gas temperature discharged from the hydrogen outlet 1d of the fuel cell stack 1A is detected by reading the sensor signal from the hydrogen temperature sensor 33 by the output control circuit 21.

  In the next step S16, the output control circuit 21 calculates the amount of water vapor contained in the gas discharged from the hydrogen outlet 1d of the fuel cell stack 1A using the hydrogen gas temperature detected in step S15, and the previous purge. From the elapsed time from the time when the valve 11 is opened, the concentration of gas other than hydrogen of the gas discharged from the hydrogen outlet 1d of the fuel cell stack 1A and the calculated water vapor is obtained. Here, when obtaining the gas concentration other than hydrogen, the output control circuit 21 uses data indicating the accumulation degree of the gas other than hydrogen according to the elapsed time after purging obtained in advance through experiments or the like. The output control circuit 21 then changes the accumulated amount of the gas concentration other than hydrogen, the next time when the purge valve 11 is opened and the gas other than hydrogen is discharged, and the time when the purge valve 11 is opened, that is, the gas The discharge time is obtained, and the amount of water discharged from the purge valve 11 (= discharged water amount C) is calculated from the discharge time and the calculated water vapor amount.

  Next, the output control circuit 21 proceeds to the output restriction determination process shown in FIG. In this output limiting process, first, in step S21, the output control circuit 21 detects the current water level of the pure water tank 13 by reading a sensor signal from the water level sensor 34, and the water level is equal to or higher than a preset specified value. It is determined whether or not. When the output control circuit 21 determines that the water level is equal to or higher than the specified value, the fuel cell is in a state where the amount of water discharged through the air pressure adjustment valve 5 is large and the water balance is not established. The process ends without limiting the output of the stack 1A. On the other hand, when the output control circuit 21 determines that the water level is not equal to or higher than the specified value and the amount of pure water accumulated in the pure water tank 13 is small, the process proceeds to step S22 in order to limit the output by the water balance. .

  In step S22, the output control circuit 21 determines whether or not the output of the fuel cell stack 1A can be limited from the traveling state of the vehicle on which the fuel cell system detected by the vehicle controller 22 is mounted. If the output control circuit 21 determines that output restriction is possible, the process proceeds to step S23. If the output control circuit 21 determines that output restriction is not possible, the output control circuit 21 proceeds to step S24.

  In step S24, the output control circuit 21 obtains the pressure of exhaust air that establishes the water balance. In step S25, the air pressure adjustment valve 5 is opened so that the exhaust air pressure that establishes the obtained water balance is obtained. Adjust the degree and end the process. Here, the output control circuit 21 controls the air pressure adjusting valve 5 so as to be higher than the current air pressure in step S24. As a result, the output control circuit 21 reduces the amount of water vapor discharged together with the discharged air by reducing the flow rate of air discharged from the air pressure regulating valve 5, thereby reducing the pure water in the pure water tank 13. Suppress.

  On the other hand, in step S23 when the output control circuit 21 determines that the output can be limited in step S22, the discharged water amount C calculated in step S16 is calculated in the tank recovery amount A calculated in step S13 and in step S14. By determining whether or not the total water amount obtained by adding the WRD recovery amount B added is greater than the amount of pure water to be discharged, it is determined whether or not the water balance is not established. The output control circuit 21 proceeds to step S26 when determining that the water balance is not established, and proceeds to step S27 when determining that the water balance is not established.

  In step S27, the output control circuit 21 calculates the temperature of the exhaust air from the fuel cell main body 1 in order to perform output restriction for recovering until the water level in the pure water tank 13 exceeds a specified value. At this time, as shown in FIG. 7, the output control circuit 21 provides an upper limit value of the exhaust air temperature of the fuel cell main body 1 according to the output value of the fuel cell stack 1A prepared for each determination result in step S23. Refer to the output restriction table indicating. And the output control circuit 21 detects the present output value from the output sensor 35, and calculates | requires the upper limit of air temperature from the said output value and the determination result (C <A + B) in step S23.

  On the other hand, in step S26, the exhaust air temperature of the fuel cell main body 1 is calculated in order to perform output restriction for establishing a water balance. At this time, the output control circuit 21 detects the current output value from the output sensor 35, refers to the output restriction table as shown in FIG. 7, and responds to the output value and the determination result in step S23 (C> A + B). The upper limit of the air temperature is obtained.

  Furthermore, in step S26 and step S27, the output control circuit 21 does not use the output restriction table as shown in FIG. 7, and the tank recovery amount A is large and the air temperature is more likely to be C <A + B. The upper limit value may be set higher, the WRD recovery amount B is larger, and the higher the possibility that C <A + B, the higher the upper limit value of the air temperature may be set, the larger the discharged water amount C, and C> A + B. The upper limit value of the air temperature may be set lower as the possibility becomes higher.

  Furthermore, in step S26, the output control circuit 21 sets the upper limit value of the air temperature to be lower as the water amount obtained by subtracting the total recovered amount obtained by adding the tank recovered amount A and the WRD recovered amount B from the discharged water amount C is increased. You may do it.

  As a result, as shown in FIG. 8, the output control circuit 21 determines that the current air temperature is T1 and the current output value of the fuel cell stack 1A is P1, and that the water balance is negative in step S23. In this case, by setting the output value P2 of the fuel cell stack 1A to be the upper limit temperature of the characteristic “C> A + B” in FIG. 7, the air temperature is set to the upper limit temperature T2 lower than the current air temperature T1. To do. As a result, the output control circuit 21 sets the maximum output of the fuel cell stack 1A so that the amount of moisture discharged to the outside is reduced and the water balance becomes positive.

  Thus, when it is determined in step S23 that the water balance is not established, the upper limit of the air temperature lower than the upper limit value of the air temperature obtained in step S27 when the water balance is established. Setting the value increases the degree of output restriction.

  In the next step S28, the output control circuit 21 determines whether or not the current exhaust air temperature of the fuel cell body 1 exceeds the upper limit value of the air temperature calculated in step S26 or step S27. If so, the maximum output of the fuel cell stack 1A is limited so as to be the upper limit value of the calculated air temperature. That is, the output control circuit 21 takes out the condensed water from the gas containing a large amount of water vapor by lowering the calorific value of the fuel cell stack 1A so as to lower the air temperature, so that the gas-liquid separator 1B The total amount of the pure water recovery amount and the pure water recovery amount of the membrane humidifier 4 is set to be substantially the same as the discharge amount from the purge valve 11.

[Effects of Second Embodiment]
As described above in detail, according to the fuel cell system according to the second embodiment to which the present invention is applied, the output limit table as shown in FIG. 7 is used, and the higher the output of the fuel cell stack 1A, The upper limit temperature of the exhaust air of the fuel cell main body 1 is set low, and the maximum output of the fuel cell stack 1A is limited when the temperature of the exhaust air exceeds the upper limit temperature. Reduction and suppression of the heat generation amount of the fuel cell stack 1A can be performed, and the water balance can be established by reducing the amount of moisture discharged to the outside.

  Therefore, according to this fuel cell system, it is possible to perform the necessary minimum output restriction more accurately than in the case where the output restriction is performed by determining only the temperature of the exhaust air, and the output restriction and the output restriction margin are reduced. For example, it is possible to reduce the influence on the vehicle running due to the output restriction.

  Further, according to this fuel cell system, the amount of water vapor contained in the exhaust air of the fuel cell main body 1 is calculated and the amount of generated water based on the output of the fuel cell stack 1A is calculated, and the difference between the calculated amount of water vapor and the amount of generated water The higher the temperature, the higher the upper limit temperature of the exhaust air, so it is possible to more accurately grasp the current water balance and limit the maximum output, and to suppress the reduction margin of the maximum output to the minimum .

  Furthermore, according to this fuel cell system, the amount of water vapor contained in the hydrogen gas discharged from the fuel cell body 1 is calculated, and the amount of water discharged from the purge valve 11 is calculated using the amount of water vapor. As the amount of water discharged from the purge valve 11 increases, the upper limit temperature of the discharged air is set lower. Therefore, the water balance is more reliably established as compared with the case where the output is limited by determining only the discharged air temperature. It is possible to determine whether the current water balance is more accurate and limit the maximum output, and to suppress the reduction margin of the maximum output to a minimum.

  Furthermore, according to this fuel cell system, the water recovery amount of the membrane humidifier 4 is calculated, and the higher the water recovery amount, the higher the upper limit temperature of the exhaust air of the fuel cell body 1 is set. Compared to the case where only the temperature is determined and the output is limited, it is possible to determine whether the water balance is established more reliably, and the current water balance can be grasped more accurately to limit the maximum output. This can be done, and the reduction margin of the maximum output can be minimized.

  Furthermore, according to this fuel cell system, the greater the amount of water obtained by subtracting the amount of water obtained by adding the WRD recovery amount B and the tank recovery amount A from the discharge water amount C discharged from the purge valve 11, Since the upper limit temperature of the discharged air is set low, it can be determined whether the water balance is established based on the water discharge amount and the water recovery amount in the entire system. Further, according to this fuel cell system, when the water balance is established, the output is limited in order to recover the water level of the pure water tank 13 to a specified value or more, and the pure water is always set to a specified value or more. On the other hand, when the water balance is not established, the output limit can be made stricter than when the water balance is established, and the water balance can be quickly recovered.

  Furthermore, according to this fuel cell system, the tank recovery amount A is obtained and the upper limit value of the exhaust air temperature is changed to limit the output of the fuel cell stack 1A. The water balance can be established by accurately controlling the output and controlling the output reduction by limiting the output of the fuel cell body 1 to a minimum.

  Furthermore, according to this fuel cell system, as shown in FIG. 7, the output limit table is set so that the discharged water amount C is equal to the water recovery amount in the gas-liquid separator 1B and the membrane humidifier 4. You can change the output limit.

  Furthermore, according to this fuel cell system, when the output of the fuel cell stack 1A cannot be restricted due to the traveling state of the vehicle, the air pressure supplied to the fuel cell main body 1 is increased. The limitation of output can be suppressed, the deterioration of vehicle drivability can be minimized, and the deterioration of water balance can be suppressed by increasing the air pressure. Specifically, it is detected by the vehicle controller 22 that the vehicle is traveling at a high load such as uphill traveling, for example, an output restriction release signal for prohibiting output restriction is transmitted from the vehicle controller 22 to the output control circuit 21. When output limitation by the output control circuit 21 cannot be performed, the water balance can be established by increasing the operation pressure by the output limitation circuit 21 even in an operation situation in which output limitation cannot be performed.

  Furthermore, according to this fuel cell system, the higher the water level of the pure water tank 13 is, the higher the output of the fuel cell stack 1A is, so that the output is limited. The output required for the fuel cell stack 1A can be realized as much as possible by utilizing the fact that the depletion of pure water occurs even if the water level is somewhat deteriorated. Furthermore, the water level of the pure water tank 13 is lower than the specified value. There is no need to limit the output in the period until it becomes, and the frequency of output limitation can be suppressed.

[Third Embodiment]
Next, a fuel cell system according to a second embodiment will be described. Note that parts similar to those in the above-described embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 9, the fuel cell system according to the third embodiment includes a navigation device 41 mounted on a vehicle. Based on information from the navigation device 41, the output of the fuel cell stack 1A is provided. This is different from the fuel cell system described above in that the value is controlled by the output control circuit 42. Such a fuel cell system limits the output of the fuel cell stack 1A by transmitting information obtained by the navigation device 41 to the output control circuit 42 when the vehicle is traveling.

  In this fuel cell system, the navigation device 41 acquires, as navigation information, the future travel distance and travel time until the vehicle arrives at the destination from the current position, road conditions, road gradient, altitude, ambient temperature, ambient humidity. Then, it is transmitted to the output control circuit 42.

  As shown in FIG. 10, in the output limiting process, in step S31, the output control circuit 42 first reads the sensor signal from the air temperature sensor 32 and the sensor signal from the water level sensor 34, thereby making the fuel cell body 1 The discharge air temperature and the water level of the pure water tank 13 are detected. The output control circuit 42 compares the water level of the pure water tank 13 detected last time with the current water level of the pure water tank 13 to determine whether the pure water has increased or decreased. Advances the process to step S32, and advances the process to step S33 if determined to be decreasing.

  Next, in step S32, the output control circuit 42 sets an output restriction table that loosens the output restriction by reducing the output reduction margin of the fuel cell stack 1A due to the output restriction, for example, as described in FIG. In step S33, an output restriction table that makes output restriction stricter is set by increasing the output reduction margin of the fuel cell stack 1A due to output restriction. As a result, the output fluctuation of the fuel cell stack 1A is reduced by changing to the output limit table indicating the maximum output according to the exhaust air temperature of the fuel cell main body 1 according to the water level of the pure water tank 13, and the fuel Prevent depletion of pure water in the battery system.

  Specifically, the output control circuit 42 performs output restriction based on the water level of the pure water tank 13 according to the maximum output characteristic a of the fuel cell stack 1A as shown in FIG. 11 in the initial state. That is, the output control circuit 42 gradually increases the maximum output of the fuel cell stack 1A within a range that is equal to or less than the rated output as it increases from the limit water level and approaches the specified value, and when the water level is the specified value, the fuel cell. The maximum output of the stack 1A is set equal to or higher than the rated output.

  On the other hand, when it is determined in step S31 that the water level has increased, in step S32, as shown in FIG. 12, even if the water level is lower than the specified value, the maximum output of the fuel cell stack 1A is the rated output. By setting the maximum output characteristic b as described above or the maximum output characteristic c that makes the maximum output of the fuel cell stack 1A at the limit water level higher than the maximum output characteristic a, the output restriction is made gentle. If it is determined in step S31 that the water level has decreased, in step S33, as shown in FIG. 13, even if the water level is higher than the specified value, the maximum output of the fuel cell stack 1A is lower than the rated output. The output limit is tightened by setting the maximum output characteristic d.

  Next, the output control circuit 42 acquires navigation information from the navigation device 41 in step S34, and in the subsequent steps S35 to S50, the maximum output characteristic b or the maximum output characteristic c is set in step S32 or set in step S33. By changing the maximum output characteristic d, the process proceeds to a process of changing the output restriction table.

  First, in step S35, the output control circuit 42 determines whether the remaining travel distance is long by determining whether the travel distance until the vehicle arrives at the destination is greater than or equal to a predetermined value. It is determined whether or not the water level in the tank 13 is lower than a specified value. If the output control circuit 42 determines that the remaining travel distance is long, the process proceeds to step S37. If the output control circuit 42 determines that the remaining travel distance is not long, the output limit table loosens the output limit in step S36. Change to That is, when the current maximum output characteristic is the maximum output characteristic d, for example, the output control circuit 42 changes the output restriction table so that the maximum output characteristic is any one of the maximum output characteristics a to c. Thereby, when the remaining travel distance is short, even if the water level of the pure water tank 13 is low, the output fluctuation due to frequent output restriction is suppressed without affecting the travel.

  Next, in step S37, the output control circuit 42 determines whether the remaining travel time is long by determining whether the travel time until the vehicle arrives at the destination is greater than or equal to a predetermined value. It is determined whether or not the water level in the pure water tank 13 is lower than a specified value. If the output control circuit 42 determines that the remaining travel time is long, the process proceeds to step S39. If the output control circuit 42 determines that the remaining travel time is not long, the output limit table loosens the output limit in step S38. Change to As a result, when the remaining traveling time is short, even if the water level of the pure water tank 13 is low, the traveling is not affected, and output fluctuation due to frequent output restriction is suppressed.

  Next, in step S39, the output control circuit 42 determines whether or not there is a traffic jam in the road conditions on which the vehicle travels to arrive at the destination, so that the water level of the pure water tank 13 is the specified value. It is determined whether it becomes lower than. If the output control circuit 42 determines that no traffic jam has occurred, the process proceeds to step S41. If the output control circuit 42 determines that the traffic jam has occurred, the output control circuit 42 tightens the output limit in step S40. Change to a table. That is, when the current maximum output characteristic is, for example, the maximum output characteristic b, the output control circuit 42 changes the output restriction table so that the maximum output characteristic becomes either the maximum output characteristic a or the maximum output characteristic d. To do. Thereby, when the remaining travel distance is short, even if the water level of the pure water tank 13 is low, the output fluctuation due to frequent output restriction is suppressed without affecting the travel. As a result, when traffic congestion occurs, output fluctuations required for the fuel cell stack 1A frequently occur, and deterioration of water balance due to depletion of pure water is prevented.

  Next, in step S41, the output control circuit 42 determines whether or not there is a steep slope on the road on which the vehicle travels in order to reach the destination, so that the water level of the pure water tank 13 is less than the specified value. It is determined whether or not it becomes lower. If the output control circuit 42 determines that there is no steep slope, the process proceeds to step S43. If it is determined that there is a steep slope, the output control circuit 42 changes to an output limit table that tightens the output limit in step S42. To do. As a result, when there is a steep slope, the output required for the fuel cell stack 1A increases, and the fluctuation of the vehicle speed frequently occurs to prevent the water balance from deteriorating due to depletion of pure water.

  Next, in step S43, the output control circuit 42 determines whether or not the road on which the vehicle travels to reach the destination is a highland, so that the water level of the pure water tank 13 is lower than the specified value. It is determined whether or not. If the output control circuit 42 determines that it is not a high altitude, the process proceeds to step S45. If it is determined that the output control circuit 42 is a high altitude, the output control circuit 42 changes to an output limit table that tightens the output limit in step S44. As a result, when traveling on high altitudes, the heat balance and the water balance are prevented from deteriorating due to the low air concentration and the reduced power usage efficiency of the entire system.

  Next, in step S45, the output control circuit 42 determines whether or not the ambient temperature at which the vehicle travels to reach the destination is high, so that the water level in the pure water tank 13 is lower than the specified value. Judge whether or not to lower. When the output control circuit 42 determines that the ambient temperature is not high, the output control circuit 42 proceeds to step S47 to change to an output limit table that tightens the output limit, and when it is determined that the ambient temperature is high, step S46. Change to the output limit table that loosens the output limit at. Thus, when the ambient temperature is high, this corresponds to the expectation of deterioration of the heat balance and water balance, and when the ambient temperature is low, this corresponds to a margin in the heat balance and water balance.

  Next, in step S48, the output control circuit 42 determines whether or not the ambient humidity in which the vehicle travels to reach the destination is high, so that the water level in the pure water tank 13 is lower than the specified value. Judge whether or not to lower. If the output control circuit 42 determines that the ambient humidity is not high, the output control circuit 42 proceeds to step S50 to change to an output limit table that tightens the output limit, and if it is determined that the ambient humidity is high, step S49. Change to the output limit table that loosens the output limit at. Accordingly, when the ambient humidity is high, it corresponds to the expectation of deterioration of the heat balance and the water balance, and when the ambient humidity is low, it corresponds to a margin in the heat balance and the water balance.

  Next, in step S51, the output control circuit 42 obtains the upper limit temperature of the exhaust air corresponding to the current output of the fuel cell stack 1A using the output restriction table set by performing the processing of steps S31 to S50. Then, it is determined whether the current exhaust air temperature of the fuel cell body 1 is equal to or higher than the upper limit temperature. When the output control circuit 42 determines that the current exhaust air temperature is not equal to or higher than the upper limit temperature, the output control circuit 42 does not need to perform output restriction, so the process is terminated, and the current exhaust air temperature is equal to or higher than the upper limit temperature. If it is determined, in step S52, the output of the fuel cell stack 1A is limited so that the exhaust air temperature becomes the upper limit temperature, and the process is terminated.

[Effect of the third embodiment]
As described above in detail, according to the fuel cell system according to the third embodiment to which the present invention is applied, whether or not the water level of the pure water tank 13 is lower than a predetermined value based on the remaining travel distance of the vehicle. When the prediction is made and the water level of the pure water tank 13 is predicted not to be lower than the predetermined value, the maximum output of the fuel cell stack 1A set based on the water level of the pure water tank 13 is changed to be high, so the remaining travel distance is short In some cases, the output limit can be changed loosely to generate the output required for the fuel cell stack 1A. Moreover, according to this fuel cell system, even if the future travel distance is long, it is possible to suppress the shortage of pure water even if the water balance deteriorates thereafter.

  Further, according to this fuel cell system, when it is predicted that the water level of the pure water tank 13 will not be lower than a predetermined value based on the remaining traveling time of the vehicle, the fuel cell set based on the water level of the pure water tank 13 Since the maximum output of the stack 1A is changed to a high value, when the remaining travel time is short, the output limit can be changed loosely to generate the output required for the fuel cell stack 1A.

  Further, according to this fuel cell system, when traffic congestion is expected from the road conditions on which the vehicle is traveling, the maximum output of the fuel cell stack 1A set based on the water level of the pure water tank 13 is changed to be low. By strictly changing the output limit, the water level of pure water can be raised before traveling on a congested road, and in preparation for the water level of pure water being lowered by performing idling operation, Pure water depletion in the fuel cell system can be prevented.

  Furthermore, according to this fuel cell system, when the water level of the pure water tank 13 is predicted to be lower than a predetermined value based on the slope of the road on which the vehicle travels, the fuel cell system is set based on the water level of the pure water tank 13. Since the maximum output of the fuel cell stack 1A is changed to a lower value, if the water balance is predicted to deteriorate due to the output of the fuel cell stack 1A when traveling on a slope road in the future, the vehicle speed, and the airflow to the radiator, the output limit is set. By changing strictly, the level of pure water can be increased before traveling on a slope road, and depletion of pure water in the fuel cell system can be prevented. Therefore, according to this fuel cell system, it is possible to prevent the output of the fuel cell stack 1A from being lowered due to the depletion of pure water, and the vehicle speed from being lowered during traveling on the climbing road.

  Furthermore, according to this fuel cell system, when the water level of the pure water tank 13 is predicted to be lower than a predetermined value based on the altitude of the road on which the vehicle is traveling, the fuel cell system is set based on the water level of the pure water tank 13. When the maximum output of the fuel cell stack 1A is changed to be low, the power consumption and power usage efficiency of the compressor 2 required by altitude are predicted, and when the hot water balance is predicted to deteriorate due to the lower power usage efficiency. By strictly changing the output restriction, the level of pure water can be increased before traveling on a high altitude road, and depletion of pure water in the fuel cell system can be prevented.

  Furthermore, according to this fuel cell system, when the deterioration of the hot water balance is predicted from the ambient temperature of the road on which the vehicle is traveling, the output limit is strictly changed, so that the pure water before traveling in the low temperature zone is changed. The water level can be kept high, and depletion of pure water in the fuel cell system can be prevented.

  Furthermore, according to this fuel cell system, when the hot water balance is expected to deteriorate due to the ambient humidity of the road on which the vehicle is traveling, the output limit is changed severely, so that the pure water before traveling in the low-humidity zone is changed. The water level can be kept high, and depletion of pure water in the fuel cell system can be prevented.

  The above-described embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and various modifications can be made depending on the design and the like as long as the technical idea according to the present invention is not deviated from this embodiment. Of course, it is possible to change.

It is a block diagram which shows the structure of the fuel cell system which concerns on 1st Embodiment to which this invention is applied. It is a flowchart which shows the process sequence of the output restriction | limiting process of the fuel cell system which concerns on 1st Embodiment to which this invention is applied. An output restriction table describing the relationship between the output of the fuel cell stack and the water balance establishment upper limit temperature is referenced. It is a flowchart which shows the process sequence of the process which calculates the parameter for performing output restriction | limiting in the output restriction | limiting process of the fuel cell system which concerns on 2nd Embodiment to which this invention is applied. It is a figure which shows the relationship between the exhaust air flow rate of a fuel cell main body, and the water recovery amount of a membrane type humidifier. It is a flowchart which shows the process sequence of the output restriction | limiting determination process in the output restriction | limiting process of the fuel cell system which concerns on 2nd Embodiment to which this invention is applied. According to the output value of the fuel cell stack, the relationship between the upper limit value of the exhaust air temperature of the fuel cell main body and the relationship between the amount of water discharged from the purge valve and the added water amount of the tank recovery amount and the WRD recovery amount FIG. It is a figure which shows the relationship between the exhaust air temperature of a fuel cell main body, and the output value of a fuel cell stack in case water balance is changed from minus. It is a block diagram which shows the structure of the fuel cell system which concerns on 3rd Embodiment to which this invention is applied. It is a flowchart which shows the process sequence of the output restriction | limiting process of the fuel cell system which concerns on 3rd Embodiment to which this invention is applied. It is a figure which shows the relationship between the water level of the pure water tank in the initial state of an output control process, and the maximum output of a fuel cell stack. It is a figure which shows the relationship with the maximum output of a fuel cell stack in the case of loosening an output restriction. It is a figure which shows the relationship with the maximum output of a fuel cell stack in the case of making output restrictions severe.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell main body 1A Fuel cell stack 1B Gas-liquid separator 2 Compressor 3 After cooler 4 Membrane type humidifier 5 Air pressure adjustment valve 6 Actuator 7 Hydrogen tank 8 Hydrogen heater 9 Ejector 10 Separator tank 11 Purge valve 12 Actuator 13 Pure water tank DESCRIPTION OF SYMBOLS 21 Output control circuit 22 Vehicle controller 31 Air pressure sensor 32 Air temperature sensor 33 Hydrogen temperature sensor 34 Water level sensor 35 Output sensor 41 Navigation apparatus 42 Output control circuit L1 Air supply piping L2 Air discharge piping L3 External discharge piping L4 Hydrogen supply piping L5 Hydrogen circulation piping L6 Gas exhaust piping

Claims (14)

A fuel cell that generates power using fuel gas and oxidant gas;
Gas supply means for controlling the oxidant gas pressure and the fuel gas pressure supplied to the fuel cell according to the output required for the fuel cell, and supplying the fuel gas and the oxidant gas to the fuel cell;
A humidifier for moving moisture contained in the oxidant gas discharged from the oxidant gas outlet of the fuel cell to an oxidant gas supplied to the oxidant gas inlet of the fuel cell by the gas supply means;
Oxidant gas temperature detection means for detecting the temperature of the oxidant gas discharged from the oxidant gas outlet of the fuel cell;
The fuel cell system further comprising: an output limiting unit that performs output limitation that lowers the maximum output of the fuel cell as the oxidant gas temperature detected by the oxidant gas temperature detection unit increases.   The output limiting means sets the upper limit temperature of the oxidant gas discharged from the fuel cell to be lower as the output of the fuel cell is higher, and the oxidant gas temperature discharged from the fuel cell exceeds the upper limit temperature. 2. The fuel cell system according to claim 1, wherein the maximum output of the fuel cell is limited so that the temperature of the oxidant gas discharged from the fuel cell is equal to or lower than the upper limit temperature. A water tank for storing water;
The output limiting means calculates the amount of water vapor contained in the oxidant gas discharged from the fuel cell and calculates the amount of generated water based on the output of the fuel cell, and the difference between the calculated amount of water vapor and the amount of generated water 3. The fuel cell system according to claim 2, wherein the upper limit temperature of the oxidant gas discharged from the fuel cell is set to be higher as the amount of gas increases. A purge valve for discharging a gas containing the fuel gas discharged from the fuel cell;
The output limiting means calculates the amount of water vapor contained in the fuel gas discharged from the fuel cell, calculates the amount of water discharged from the purge valve using the amount of water vapor, and discharges from the calculated purge valve 3. The fuel cell system according to claim 2, wherein the upper limit temperature of the oxidant gas discharged from the fuel cell is set lower as the amount of water to be discharged is larger.   The output limiting means is configured to reduce a water recovery amount transferred from the oxidant gas discharged from the oxidant gas outlet of the fuel cell to the oxidant gas supplied to the oxidant gas inlet of the fuel cell by the humidifier. 3. The fuel cell system according to claim 2, wherein the upper limit temperature of the oxidant gas discharged from the fuel cell is set higher as the water recovery amount is calculated. A water tank for storing water;
A purge valve for discharging a gas containing the fuel gas discharged from the fuel cell,
The output limiting means calculates the amount of water vapor contained in the fuel gas discharged from the fuel cell, and the amount of water discharged from the purge valve based on the amount of water vapor, and the oxidant gas of the fuel cell by the humidifier The amount of water recovered from the oxidant gas discharged from the outlet to the oxidant gas supplied to the oxidant gas inlet of the fuel cell, the amount of water vapor contained in the oxidant gas discharged from the fuel cell, and the fuel The amount of water obtained by calculating the amount of condensed water recovered in the water tank, which is a difference from the amount of generated water based on the output of the battery, and adding the amount of recovered water and the amount of condensed water from the amount of water discharged from the purge valve The fuel cell system according to claim 2, wherein the upper limit temperature of the oxidant gas discharged from the fuel cell is set to be lower as the amount of water obtained by subtracting the amount of water is larger. A fuel cell system mounted on a vehicle that travels using the output of the fuel cell,
The gas supply means is controlled to increase the pressure of the oxidant gas supplied to the fuel cell when the output of the fuel cell cannot be limited due to the running state of the vehicle. The fuel cell system described. A water tank for storing water;
2. The fuel cell system according to claim 1, wherein the output limiting unit sets the maximum output of the fuel cell to be higher as the level of water stored in the water tank is higher. .   9. The output restriction unit according to claim 8, wherein the output restriction unit performs the output restriction by setting the maximum output of the fuel cell to be lower as the decrease rate of the water level stored in the water tank is faster. Fuel cell system.   The output limiting means predicts whether or not the water level of the water tank is lower than a predetermined value based on the remaining travel distance of the vehicle, and predicts that the water level of the water tank is not lower than a predetermined value. The fuel cell system according to claim 8, wherein the maximum output of the fuel cell set based on the water level of the water tank is changed to be high.   The output limiting means predicts whether or not the water level of the water tank is lower than a predetermined value based on the remaining travel time of the vehicle, and predicts that the water level of the water tank does not become lower than a predetermined value. The fuel cell system according to claim 8, wherein the maximum output of the fuel cell set based on the water level of the water tank is changed to be high.   The output limiting means predicts whether or not the water level of the water tank is lower than a predetermined value based on a road condition where the vehicle is traveling, and predicts that the water level of the water tank is lower than a predetermined value. 9. The fuel cell system according to claim 8, wherein the maximum output of the fuel cell set based on the water level of the water tank is changed to be low.   The output limiting means predicts whether or not the water level of the water tank is lower than a predetermined value based on a gradient or altitude as a road condition on which the vehicle is traveling, and predicts that the water level of the water tank is lower than a predetermined value The fuel cell system according to claim 12, wherein the maximum output of the fuel cell set based on the water level of the water tank is changed to be low. The output limiting means predicts whether or not the water level of the water tank is lower than a predetermined value based on the ambient temperature or ambient humidity of the road on which the vehicle is traveling, and predicts that the water level of the water tank is lower than the predetermined value. In this case, the fuel cell system according to claim 8, wherein the maximum output of the fuel cell set based on the water level of the water tank is changed to be low.

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