Fuel cell apparatus

Abstract

This fuel cell apparatus is provided with: a fuel cell; a raw fuel supply unit that supplies raw fuel gas having a varying methane concentration to the fuel cell; and a control device. When the operation value of the raw fuel supply unit exceeds an operation threshold, the control device changes an upper limit current value, which is the upper limit value of the power generation current value of the fuel cell.

Description

fuel cell device Cross-reference to related applications

[0001] This application claims priority to Japanese Patent Application No. 2024-125457, filed on July 31, 2024, the entire disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates to fuel cell devices.

[0003] A fuel cell device includes a pump that supplies raw fuel gas to a fuel cell. Fuel cell devices that control such pumps are known. For example, a control device described in Patent Document 1 controls a gas pump by setting a duty cycle through open-loop control based on a required gas flow rate, acquired gas temperature, and gas pressure so that gas flows through a gas flow path at a required gas flow rate required by the system.

[0004] Japanese Patent Application Laid-Open No. 2018-195438

[0005] A fuel cell device according to one embodiment of the present disclosure comprises a fuel cell, a raw fuel supply unit that supplies raw fuel gas having a fluctuating methane concentration to the fuel cell, and a control device, wherein the control device changes an upper limit current value, which is an upper limit value of the power generation current value of the fuel cell, when the operating value of the raw fuel supply unit exceeds an operating threshold value.

[0006] A fuel cell device according to one embodiment of the present disclosure comprises: a fuel cell; a raw fuel supply unit that supplies raw fuel gas having a fluctuating methane concentration to the fuel cell; and a control device, wherein the control device changes an upper limit current value, which is an upper limit value of the power generation current value of the fuel cell, when the methane concentration of the raw fuel gas is estimated to be below a concentration threshold and the power generation current value of the fuel cell exceeds a current threshold.

[0007] While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments and is not to be limited to the disclosed exemplary embodiments.

[0008] The raw fuel gas used in a fuel cell device may have a fluctuating methane concentration, such as biogas. When using such a gas as the raw fuel gas, it would be useful to be able to improve the operating efficiency of the fuel cell device based on the performance of the pump. According to one embodiment of the present disclosure, the operating efficiency of the fuel cell device can be improved.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0010] A fuel cell system 1 as shown in Fig. 1 can supply power to a group of loads 2. In Fig. 1, solid lines indicate the flow of fluids such as electric power or raw fuel gas. Dashed lines indicate the flow of control. The group of loads 2 includes at least one load device. The load device is, for example, an electrical appliance or an electronic device.

[0011] The fuel cell system 1 includes a power conversion device 10 and a fuel cell device 20. The power conversion device 10 and the fuel cell device 20 can communicate with each other via wire or wirelessly.

[0012] The power conversion device 10 is also called a "power conditioner." DC power is supplied to the power conversion device 10 from the fuel cell device 20. The power conversion device 10 converts the supplied DC power into predetermined AC power or DC power. The power conversion device 10 supplies the converted AC power or DC power to the load group 2.

[0013] The power conversion device 10 includes a current sensor 11. The current sensor 11 is capable of detecting the value of the current generated by the fuel cell device 20. The power conversion device 10 transmits the detection result of the current sensor 11 on the value of the current generated by the fuel cell device 20 to the fuel cell device 20.

[0014] A raw fuel gas with a varying methane concentration and an oxygen-containing gas are supplied to the fuel cell device 20. The fuel cell device 20 generates DC power using these gases.

[0015] In the present disclosure, "raw fuel gas with fluctuating methane concentration" refers to raw fuel gas whose methane concentration fluctuates compared to the methane concentration of a reference raw fuel gas. The reference raw fuel gas is a raw fuel gas that was used as a reference when the fuel cell device 20 was designed. In other words, the fuel cell device 20 may be designed assuming that the reference raw fuel gas will be supplied. The reference raw fuel gas is, for example, city gas. The raw fuel gas whose methane concentration fluctuates may be a raw fuel gas whose methane concentration fluctuates over time compared to the reference raw fuel gas. Alternatively, the raw fuel gas whose methane concentration fluctuates may be a gas whose methane concentration simply fluctuates compared to the methane concentration of the reference raw fuel gas. In this case, the raw fuel gas whose methane concentration fluctuates does not have to fluctuate over time. The raw fuel gas whose methane concentration fluctuates is, for example, biogas. However, the raw fuel gas whose methane concentration fluctuates is not limited to biogas, as long as it is a raw fuel gas whose methane concentration fluctuates compared to the methane concentration of the reference raw fuel gas.

[0016] In the present disclosure, the term "oxygen-containing gas" may refer to any gas that contains oxygen. In this embodiment, the oxygen-containing gas is air.

[0017] The fuel cell device 20 includes a fuel cell 21, a reforming water supply unit 30, a supply line 31, a raw fuel supply unit 32, a supply line 33, a flow sensor 34, an air supply unit 35, a supply line 36, a flow sensor 37, and a control device 40.

[0018] The fuel cell 21 is electrically connected to the power conversion device 10. The fuel cell 21 generates DC power. The fuel cell 21 supplies the generated DC power to the power conversion device 10.

[0019] An upper limit current value is set for the fuel cell 21. The upper limit current value is the upper limit of the current value generated by the fuel cell 21. In other words, the fuel cell 21 generates electricity so that the generated current value does not exceed the upper limit current value. The upper limit current value can be changed as described below. Before being changed, the upper limit current value is set to an initial value. The initial value of the upper limit current value may be set based on the generated current value of the fuel cell 21 when a reference raw fuel gas is used in the fuel cell 21.

[0020] The fuel cell 21 includes a reformer 22 , a cell stack 23 , a combustion section 24 , and a temperature sensor 25 .

[0021] The reformer 22 is supplied with reforming water from a reforming water supply unit 30 via a supply line 31. The reformer 22 is also supplied with raw fuel gas from a raw fuel supply unit 32 via a supply line 33. The reformer 22 generates fuel gas by steam reforming using the supplied reforming water and raw fuel gas. The fuel gas generated by the reformer 22 is supplied to the cell stack 23.

[0022] The cell stack 23 is, for example, a solid oxide fuel cell (SOFC). Air is supplied to the cell stack 23 from an air supply unit 35 via a supply line 36. Fuel gas is also supplied to the cell stack 23 from the reformer 22. The cell stack 23 causes an electrochemical reaction between the air supplied from the air supply unit 35 and the fuel gas supplied from the reformer 22. The cell stack 23 generates DC power by causing the electrochemical reaction. The DC power generated by the cell stack 23 is supplied to the power conversion device 10.

[0023] The combustion unit 24 combusts unreacted fuel gas in the fuel cell 21. In this embodiment, the combustion unit 24 combusts unreacted fuel gas in the cell stack 23 using unreacted air. When the unreacted fuel gas and the like are combusted, heat is generated in the combustion unit 24. The combustion unit 24 may use this generated heat to heat the reformer 22.

[0024] The temperature sensor 25 is capable of detecting the temperature of the combustion section 24. The temperature sensor 25 includes, for example, a thermocouple. The temperature sensor 25 outputs the detection result of the temperature of the combustion section 24 to the control device 40.

[0025] The reforming water supply unit 30 supplies reforming water to the reformer 22 via a supply line 31. The reforming water supply unit 30 generates reforming water using, for example, water recovered from the exhaust gas of the cell stack 23 as a raw material. The reforming water supply unit 30 includes, for example, a pump. The reforming water supply unit 30 controls the flow rate of the reforming water supplied to the reformer 22 based on a control signal received from the control device 40.

[0026] The supply line 31 connects the reforming water supply unit 30 and the reformer 22. The supply line 31 includes, for example, piping, valves, and the like.

[0027] The raw fuel supply unit 32 supplies raw fuel gas to the reformer 22 via a supply line 33. As described above, this raw fuel gas is a gas whose methane concentration fluctuates. The raw fuel supply unit 32 includes, for example, a pump. This pump is, for example, a pump controlled by current, a pump controlled by rotation speed, or a pump controlled by the number of shots. When the raw fuel supply unit 32 includes a pump controlled by current, the flow rate of the raw fuel supply unit 32 can be changed by changing the duty ratio of the current flowing through this pump. The raw fuel supply unit 32 controls the flow rate of the raw fuel gas supplied to the reformer 22 based on a control signal received from the control device 40.

[0028] Here, the operation value of the raw fuel supply unit 32 indicates a value related to the operation of the raw fuel supply unit 32. The operation value of the fuel supply unit 32 may be given by an element that can change the flow rate of the raw fuel supply unit 32. The operation value of the raw fuel supply unit 32 may be expressed depending on the type of the pump included in the raw fuel supply unit 32. For example, the operation value of the raw fuel supply unit 32 may be expressed by a duty ratio in the case of a pump controlled by current, by the number of rotations in the case of a pump controlled by the number of rotations, or by the number of shots in the case of a pump controlled by the number of shots. Furthermore, the operation value of the raw fuel supply unit 32 may also mean the operation rate of the raw fuel supply unit 32.

[0029] The supply line 33 connects the raw fuel supply unit 32 and the reformer 22. The supply line 33 includes, for example, pipes and valves.

[0030] The flow rate sensor 34 is attached to the supply line 33. The flow rate sensor 34 detects the flow rate of the raw fuel gas flowing through the supply line 33. The flow rate sensor 34 outputs the detection result of the flow rate of the raw fuel gas to the control device 40.

[0031] The air supply unit 35 supplies air to the cell stack 23 via a supply line 36. The air supply unit 35 includes, for example, a blower. The air supply unit 35 controls the flow rate of air supplied to the cell stack 23 based on a control signal received from the control device 40.

[0032] The air supply unit 35 may preliminarily heat air taken in from the outside and supply it to the cell stack 23 .

[0033] The supply line 36 connects the air supply unit 35 and the cell stack 23. The supply line 36 includes, for example, piping and valves.

[0034] The flow rate sensor 37 is attached to the supply line 36. The flow rate sensor 37 detects the flow rate of air flowing through the supply line 36. The flow rate sensor 37 outputs the detection result of the air flow rate to the control device 40.

[0035] The control device 40 controls the operation of the fuel cell device 20 based on a control signal from the power conversion device 10. The control device 40 includes a communication unit 41, a storage unit 42, and a control unit 43.

[0036] The communication unit 41 includes at least one communication module that can communicate with the power conversion device 10. The communication module is a module that complies with the standard for communication between the power conversion device 10 and the fuel cell device 20.

[0037] The storage unit 42 is configured to include at least one semiconductor memory, at least one magnetic memory, at least one optical memory, or a combination of at least two of these. The storage unit 42 may function as a main storage device, an auxiliary storage device, or a cache memory. The storage unit 42 stores data used in the operation of the control device 40 and data obtained by the operation of the control device 40. The storage unit 42 may also store a program executed by the control unit 43.

[0038] The control unit 43 is configured to include at least one processor, at least one dedicated circuit, or a combination of these. The processor is, for example, a general-purpose processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), or a dedicated processor specialized for specific processing. The dedicated circuit is, for example, an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). The control unit 43 controls each part of the control device 40 and executes processing related to the operation of the control device 40.

[0039] The control unit 43 can acquire the current value of the current generated by the fuel cell 21. In this embodiment, the control unit 43 acquires the current value of the current generated by the fuel cell 21 by receiving, from the power conversion device 10, the detection result of the current sensor 11 of the current value of the current generated by the fuel cell device 20 via the communication unit 41.

[0040] The control unit 43 is capable of acquiring the current power generation value of the fuel cell 21. In this embodiment, the control unit 43 receives the detection result of the generated current value of the fuel cell device 20 by the current sensor 11 from the power conversion device 10 via the communication unit 41, and calculates the current generated power value of the fuel cell device 20 based on the received generated current value. The control unit 43 acquires the current generated power value of the fuel cell 21 by calculating the current generated power value of the fuel cell device 20.

[0041] The control unit 43 can adjust the flow rate of the raw fuel gas supplied to the fuel cell 21 by the raw fuel supply unit 32 by sending a control signal to the raw fuel supply unit 32 based on the detection result of the flow rate of the raw fuel gas by the flow rate sensor 34 to adjust the operation value of the raw fuel supply unit 32. However, the control unit 43 may simply adjust the operation value of the raw fuel supply unit 32 by sending a control signal to the raw fuel supply unit 32.

[0042] The control unit 43 can adjust the flow rate of air supplied to the fuel cell 21 by the air supply unit 35 by sending a control signal to the air supply unit 35 based on the detection result of the air flow rate by the flow rate sensor 37.

[0043] As described above, the fuel cell device 20 is supplied with raw fuel gas whose methane concentration fluctuates. Such raw fuel gas may have a lower methane concentration than a reference raw fuel gas, such as city gas. When the methane concentration is low, in order to make the fuel cell 21 generate electricity while maintaining a constant upper limit current value of the fuel cell 21, the operating value of the raw fuel supply unit 32 must be increased compared to when the reference raw fuel gas is used. However, the operating value of the raw fuel supply unit 32 has an upper limit. Therefore, when the operating value of the raw fuel supply unit 32 is increased, the fuel cell device 20 may not operate efficiently.

[0044] Therefore, when the operation value of the raw fuel supply unit 32 exceeds the operation threshold, the control unit 43 changes the upper limit current value of the fuel cell 21. The operation threshold may be set based on the upper limit of the operation value of the raw fuel supply unit 32. By changing the upper limit current value of the fuel cell 21 in this way when the operation value of the raw fuel supply unit 32 exceeds the operation threshold, the fuel cell device 20 can be operated efficiently even when the methane concentration of the raw fuel gas is low.

[0045] In some cases, the methane concentration of the raw fuel gas can be estimated. For example, an estimated value of the methane concentration of the raw fuel gas can be obtained in advance from a vendor that sells the raw fuel gas. In other cases, the methane concentration of the raw fuel gas can be estimated based on, for example, the temperature of the combustion unit 24 and the fuel utilization rate of the fuel cell 21. The fuel utilization rate of the fuel cell 21 is the proportion of the raw fuel gas supplied to the fuel cell 21 that is used to generate electricity in the fuel cell 21. One method for estimating the methane concentration of the raw fuel gas, for example, is to first measure the power generation current value of the fuel cell 21 and the temperature of the combustion unit 24. Next, a reference raw fuel such as city gas is used in advance to investigate the relationship between the temperature of the combustion unit 24 and the amount of fuel used in the combustion unit 24, i.e., the fuel utilization rate. Furthermore, the methane concentration can be estimated by comparing the amount of hydrogen required to output the measured power generation current value and the amount of methane required for combustion, measured from the temperature of the combustion unit 24, with the total amount of raw fuel supplied from the raw fuel supply unit 32. The amount of hydrogen required to output the measured power generation current value is converted into the amount of methane.

[0046] Therefore, when it is estimated that the methane concentration of the raw fuel gas is below the concentration threshold, the control unit 43 changes the upper limit current value of the fuel cell 21 if the power generation value of the fuel cell 21 exceeds the power threshold. The concentration threshold may be set based on the methane concentration of the reference raw fuel gas. The power threshold may be set based on the initial value of the upper limit current value of the fuel cell 21. When it is estimated that the methane concentration of the raw fuel gas is below the concentration threshold, if the fuel cell 21 is to generate power while maintaining the upper limit current value of the fuel cell 21 constant, the operating value of the raw fuel supply unit 32 must be increased compared to when the reference raw fuel gas is used. However, the operating value of the raw fuel supply unit 32 has an upper limit. Therefore, when it is estimated that the methane concentration of the raw fuel gas is below the concentration threshold and the power generation value of the fuel cell 21 exceeds the power threshold, the fuel cell device 20 can be operated efficiently by changing the upper limit current value of the fuel cell 21.

[0047] 2 and 3 are flowcharts showing an example of the operation of the fuel cell device 20 shown in FIG. 1 . The control unit 43 of the control device 40 starts the process of step S1 shown in FIG. 2 after the start-up of the fuel cell 21 is completed. The control unit 43 may start the process of step S1 shown in FIG. 2 when the methane concentration of the raw fuel gas is estimated to be below the concentration threshold by the above-mentioned method. Here, the method of estimating the methane concentration of the raw fuel gas described above may be executed by the control unit 43 separately from the flow shown in FIGS. 2 and 3 . Alternatively, this method of estimating the methane concentration of the raw fuel gas may be executed by a device other than the control device 40. In this case, the control unit 43 may obtain an estimated value of the methane concentration of the raw fuel gas from a different device via the communication unit 41. That is, the control unit 43 may obtain an estimated value of the methane concentration of the raw fuel gas in advance from a supplier, or may obtain it by the control unit 43 executing the above-mentioned methane concentration of the raw fuel gas measurement, or may obtain it from a different device. The control unit 43 may start the process of step S1 when determining that the acquired estimated value of the methane concentration of the raw fuel gas is below the concentration threshold value.

[0048] In the process of step S1, the control unit 43 acquires information on the current setting change of the upper limit current value of the fuel cell device 20 and information on the current setting change of the raw fuel gas. Furthermore, the control unit 43 acquires the current power generation current value of the fuel cell 21. Based on this information, the control unit 43 determines whether there are no restrictions on the current setting change of the upper limit current value and the current setting change of the raw fuel gas, and whether the acquired power generation current value of the fuel cell 21 is below the first current threshold. A case where there is a restriction on the setting change of the current upper limit current value is when a change of the current upper limit current value is not permitted. Furthermore, a case where there is a restriction on the setting change of the current raw fuel gas setting is when a change of the current flow rate of the raw fuel gas is not permitted. For example, if the process of step S3 described below has already been executed, there is a restriction on the setting change of the current upper limit current value, and there is a restriction on the current setting change of the raw fuel gas. The first current threshold may be set based on the power generation current value of the fuel cell 21 when power is generated using raw fuel gas, such as biogas, whose methane concentration fluctuates. The first current threshold is, for example, approximately two-thirds of the initial value of the upper limit current value. If the control unit 43 determines that there are no restrictions on changing the current upper limit current value or the current setting of the raw fuel gas, and that the acquired generated current value of the fuel cell 21 is not below the first current threshold (step S1: NO), the control unit 43 proceeds to the processing of step S2. If the control unit 43 determines that there are no restrictions on changing the current upper limit current value or the current setting of the raw fuel gas, and that the acquired generated current value of the fuel cell 21 is below the first current threshold (step S1: YES), the control unit 43 ends the processing shown in FIG.

[0049] In the process of step S2, the control unit 43 uses the information on the change in the current upper limit current value setting and the information on the current change in the raw fuel gas setting acquired in the process of step S1. Based on this information, the control unit 43 determines whether or not there are restrictions on the change in the current upper limit current value setting and the current change in the raw fuel gas setting of the fuel cell device 20. If the control unit 43 does not determine that there are restrictions on the change in the current upper limit current value setting and the current change in the raw fuel gas setting of the fuel cell device 20 (step S2: NO), the control unit 43 proceeds to the process of step S3. If the control unit 43 determines that there are restrictions on the change in the current upper limit current value setting and the current change in the raw fuel gas setting of the fuel cell device 20 (step S2: YES), the control unit 43 proceeds to the process of step S4.

[0050] In the process of step S3, if there is no limit on changing the current upper limit current value, the control unit 43 acquires the current power generation current value of the fuel cell 21 and sets the upper limit current value to the current power generation current value. By setting the current power generation current value of the fuel cell 21 to the upper limit current value, the fuel cell 21 can generate power at the maximum power generation value, with the current power generation current value as the upper limit. However, the control unit 43 may set the current upper limit current value to a power generation current value that is preset based on the configuration of the fuel cell device 20, instead of the current power generation current value.

[0051] In the processing of step S3, if there is no limit on changing the current setting of the raw fuel gas, the control unit 43 sets the flow rate of the raw fuel gas supplied from the raw fuel supply unit 32 to the reformer 22 to a set amount. The set amount is smaller than the maximum flow rate of the raw fuel gas that the raw fuel supply unit 32 can supply. The set amount may be set based on the flow rate of the raw fuel gas at which the raw fuel supply unit 32 can stably supply the raw fuel gas to the reformer 22. Here, if the raw fuel supply unit 32 attempts to supply the raw fuel gas to the reformer 22 at the maximum flow rate, fluctuations may occur in the flow rate of the raw fuel gas from the raw fuel supply unit 32. Therefore, by setting the flow rate of the raw fuel gas supplied from the raw fuel supply unit 32 to the set amount, the possibility of fluctuations in the flow rate of the raw fuel gas from the raw fuel supply unit 32 can be reduced.

[0052] After executing the process of step S3, the control unit 43 proceeds to the process of step S4.

[0053] In the process of step S4, the control unit 43 determines whether or not the operation value of the raw fuel supply unit 32 exceeds the operation threshold. If the control unit 43 determines that the operation value of the raw fuel supply unit 32 exceeds the operation threshold (step S4: YES), the control unit 43 proceeds to the process of step S7 shown in Fig. 3. If the control unit 43 determines that the operation value of the raw fuel supply unit 32 is equal to or less than the operation threshold (step S4: NO), the control unit 43 proceeds to the process of step S5.

[0054] In the process of step S5, the control unit 43 determines whether the flow rate of the raw fuel gas has been reduced in order to lower the temperature of the combustion unit 24. For example, if step S13 described below has already been executed, the flow rate of the raw fuel gas has been reduced in order to lower the temperature of the combustion unit 24. If the control unit 43 does not determine that the flow rate of the raw fuel gas has been reduced in order to lower the temperature of the combustion unit 24 (step S5: NO), the control unit 43 proceeds to the process of step S6. If the control unit 43 determines that the flow rate of the raw fuel gas has been reduced in order to lower the temperature of the combustion unit 24 (step S5: YES), the control unit 43 proceeds to the process of step S7 shown in FIG. 3.

[0055] In the process of step S6, the control unit 43 increases the flow rate of the raw fuel gas supplied by the raw fuel supply unit 32 to the reformer 22 of the fuel cell 21. The degree to which the flow rate of the raw fuel gas is increased may be set based on the configuration of the raw fuel supply unit 32. After executing the process of step S6, the control unit 43 proceeds to the process of step S7 shown in FIG.

[0056] In the process of step S7 shown in Fig. 3, the control unit 43 obtains the current temperature of the combustion unit 24 by obtaining the detection result of the current temperature of the combustion unit 24 from the temperature sensor 25. The control unit 43 determines whether the obtained temperature of the combustion unit 24 is equal to or lower than a third temperature. The third temperature is lower than a first temperature, which will be described later. The third temperature may be set based on the temperature at which the combustion unit 24 may misfire.

[0057] If the control unit 43 determines that the acquired temperature of the combustion unit 24 is equal to or lower than the third temperature (step S7: YES), the control unit 43 proceeds to the process of step S8. If the control unit 43 determines that the acquired temperature of the combustion unit 24 exceeds the third temperature (step S7: NO), the control unit 43 proceeds to the process of step S11.

[0058] In the processing of step S8, the control unit 43 reduces the current upper limit current value. The degree to which the upper limit current value is reduced may be set based on the configuration of the combustion unit 24 or the configuration of the cell stack 23. By reducing the upper limit current value, the power generation value of the fuel cell 21 can be reduced. By reducing the power generation value of the fuel cell 21, the amount of unreacted fuel gas in the fuel cell 21 can be increased. By increasing the amount of unreacted fuel gas in the fuel cell 21, the temperature of the combustion unit 24 can be raised. After performing the processing of step S8, the control unit 43 proceeds to the processing of step S9.

[0059] In the processing of step S9, the control unit 43 obtains the current temperature of the combustion unit 24 by obtaining the detection result of the current temperature of the combustion unit 24 from the temperature sensor 25. The control unit 43 determines whether the obtained temperature of the combustion unit 24 is equal to or higher than a first temperature. The first temperature may be lower than a target temperature of the combustion unit 24. The target temperature of the combustion unit 24 is a temperature that should be set as a target for the combustion unit 24 in order to stably operate the fuel cell 21. The degree to which the first temperature is lowered from the target temperature of the combustion unit 24 may be set based on the configuration of the combustion unit 24. The first temperature may be set based on the configuration of the combustion unit 24.

[0060] If the control unit 43 determines that the acquired temperature of the combustion unit 24 is lower than the first temperature (step S9: NO), the control unit 43 proceeds to the process of step S10. If the control unit 43 determines that the acquired temperature of the combustion unit 24 is equal to or higher than the first temperature (step S9: YES), the control unit 43 ends the process shown in Fig. 3. However, the control unit 43 may repeat the process of step S9 at predetermined time intervals. The predetermined time may be set based on the configuration of the combustion unit 24.

[0061] In the process of step S10, the control unit 43 reduces the current upper limit current value. The degree to which the upper limit current value is reduced may be set based on the configuration of the combustion unit 24 or the configuration of the cell stack 23. By reducing the upper limit current value, it is possible to increase the amount of unreacted fuel gas in the fuel cell 21. An increase in unreacted fuel gas increases the temperature of the combustion unit 24, reducing the possibility of the combustion unit 24 misfiring. After performing the process of step S10, the control unit 43 performs the process of step S9 again.

[0062] In the process of step S11, the control unit 43 obtains the current temperature of the combustion unit 24 by obtaining the detection result of the current temperature of the combustion unit 24 from the temperature sensor 25. The control unit 43 determines whether the obtained temperature of the combustion unit 24 is equal to or higher than a fourth temperature. The fourth temperature is higher than a second temperature, which will be described later. The fourth temperature may be set based on an upper limit value of the temperature of the combustion unit 24 for stable operation of the fuel cell 21.

[0063] If the control unit 43 determines that the acquired temperature of the combustion unit 24 is equal to or higher than the fourth temperature (step S11: YES), the control unit 43 proceeds to the process of step S12. If the control unit 43 determines that the acquired temperature of the combustion unit 24 is lower than the fourth temperature (step S11: NO), the control unit 43 ends the process shown in FIG.

[0064] In the process of step S12, the control unit 43 acquires the current power generation value of the fuel cell 21. The control unit 43 determines whether the acquired power generation value of the fuel cell 21 is equal to or greater than a first power value. If the control unit 43 determines that the acquired power generation value of the fuel cell 21 is equal to or greater than the first power value (step S12: YES), the control unit 43 proceeds to the process of step S13. If the control unit 43 determines that the acquired power generation value of the fuel cell 21 is lower than the first power value (step S12: NO), the control unit 43 proceeds to the process of step S14. The first power value may be set based on the rated power value of the fuel cell 21.

[0065] In the processing of step S13, the control unit 43 reduces the flow rate of the raw fuel gas supplied to the reformer 22 of the fuel cell 21 by the raw fuel supply unit 32. The degree to which the flow rate of the raw fuel gas is reduced may be set based on the configuration of the combustion unit 24 or the configuration of the cell stack 23. By reducing the flow rate of the raw fuel gas in this manner, it is possible to reduce the amount of unreacted fuel gas in the fuel cell 21. By reducing the amount of unreacted fuel gas in the fuel cell 21, it is possible to lower the temperature of the combustion unit 24. As a result, it is possible to operate the fuel cell 21 stably. After executing the processing of step S13, the control unit 43 proceeds to the processing of step S17.

[0066] In the process of step S14, the control unit 43 determines whether the current upper limit current value is equal to or less than the determination threshold value. The determination threshold value may be smaller than the maximum value of the upper limit current value by a predetermined value. The predetermined value may be set based on the design margin of the fuel cell 21, etc. The predetermined value may be set appropriately, for example, within a range of less than 5% of the upper limit current value. If the control unit 43 determines that the current upper limit current value is equal to or less than the determination threshold value (step S14: YES), the control unit 43 proceeds to the process of step S15. If the control unit 43 determines that the current upper limit current value exceeds the determination threshold value (step S14: NO), the control unit 43 proceeds to the process of step S16.

[0067] In the processing of step S15, the control unit 43 increases the current upper limit current value. The degree to which the upper limit current value is increased may be set based on the configuration of the combustion unit 24 or the configuration of the cell stack 23. By increasing the upper limit current value in this manner, the power generation current value of the fuel cell 21 can be increased. By increasing the power generation current value of the fuel cell 21, the amount of unreacted fuel gas in the fuel cell 21 can be reduced. As a result of the reduction in the amount of unreacted fuel gas in the fuel cell 21, the fuel cell 21 can be operated stably. After executing the processing of step S15, the control unit 43 proceeds to the processing of step S17.

[0068] In the process of step S16, the control unit 43 sets the current upper limit current value to the maximum upper limit current value. However, if the current upper limit current value is already the maximum upper limit current value, the control unit 43 leaves the current upper limit current value as the maximum upper limit current value. When the upper limit current value is the maximum upper limit current value, the power generation current value of the fuel cell 21 can be increased. By increasing the power generation current value of the fuel cell 21, the amount of unreacted fuel gas in the fuel cell 21 can be reduced. By reducing the amount of unreacted fuel gas in the fuel cell 21, the temperature of the combustion unit 24 can be lowered. As a result, the fuel cell 21 can be operated stably. After executing the process of step S16, the control unit 43 proceeds to the process of step S17.

[0069] In the process of step S17, the control unit 43 obtains the current temperature of the combustion unit 24 by obtaining the detection result of the current temperature of the combustion unit 24 from the temperature sensor 25. The control unit 43 determines whether the obtained temperature of the combustion unit 24 is equal to or lower than a second temperature. The second temperature is higher than the target temperature of the combustion unit 24. The degree to which the second temperature is to be increased from the target temperature of the combustion unit 24 may be set based on the configuration of the combustion unit 24. The second temperature may be set based on the configuration of the combustion unit 24.

[0070] If the control unit 43 determines that the acquired temperature of the combustion unit 24 is equal to or lower than the second temperature (step S17: YES), the control unit 43 ends the process shown in Fig. 3. If the control unit 43 determines that the acquired temperature of the combustion unit 24 exceeds the second temperature (step S17: NO), the control unit 43 proceeds to the process of step S12 again.

[0071] 2 or 3, when a predetermined time has elapsed, the control unit 43 may restart the process from step S1. The predetermined time may be set based on the configuration of the fuel cell device 20.

[0072] Furthermore, when the fuel cell device 20 is executing a predetermined control, the control unit 43 does not need to execute the processes shown in Figures 2 and 3. The predetermined control is, for example, control to change the upper limit current value. One example of process control is water self-sustaining control. Water self-sustaining control is control to change the upper limit current value in order to recover reforming water when the amount of reforming water supplied to the reformer 22 is equal to or less than a reference amount. For example, reducing the upper limit current value increases the amount of recovered reforming water.

[0073] Furthermore, in the processing of step S2, the control unit 43 may determine whether there are restrictions on changing the current upper limit current value of the fuel cell device 20 and the current setting of the raw fuel gas (step S2: YES) or whether there are no restrictions on changing the current upper limit current value of the fuel cell device 20 and the current setting of the raw fuel gas (step S2: NO). In this case, if the control unit 43 determines that there are restrictions on changing the current upper limit current value of the fuel cell device 20 and the current setting of the raw fuel gas (step S2: YES), the control unit 43 proceeds to the processing of step S4. If the control unit 43 determines that there are no restrictions on changing the current upper limit current value of the fuel cell device 20 and the current setting of the raw fuel gas (step S2: NO), the control unit 43 proceeds to the processing of step S3.

[0074] Furthermore, in the processing of step S4, if the control unit 43 determines that the operation value of the raw fuel supplying unit 32 exceeds the operation threshold value (step S4: YES), the control unit 43 may change the operation value of the raw fuel supplying unit 32 to a set value. The set value is smaller than the maximum operation value of the raw fuel supplying unit 32. The set value may be set based on the configuration of the raw fuel supplying unit 32. After changing the operation value of the raw fuel supplying unit 32 to the set value, the control unit 43 may proceed to the processing of step S7.

[0075] As described above, the fuel cell device 20 according to this embodiment includes a fuel cell 21, a raw fuel supply unit 32 that supplies raw fuel gas with a fluctuating methane concentration to the fuel cell 21, and a control device 40. When the operation value of the raw fuel supply unit 32 exceeds the operation threshold, the control device 40 changes the upper limit current value of the power generation current of the fuel cell 21. For example, when the control unit 43 determines that the operation value of the raw fuel supply unit 32 exceeds the operation threshold (step S4: YES), the control unit 43 proceeds to step S7. In the processes from step S7 onward, for example, in steps S8, S10, S15, and S16, the control unit 43 changes the upper limit current value of the power generation current of the fuel cell 21. As described above, raw fuel gas with a fluctuating methane concentration may have a lower methane concentration than a reference raw fuel gas such as city gas. When the methane concentration is low, in order to generate power from the fuel cell 21 while maintaining the upper limit current value of the fuel cell 21 constant, the operation value of the raw fuel supply unit 32 must be increased compared to when reference raw fuel gas is used. In contrast, in this embodiment, when the operation value of the raw fuel supply unit 32 exceeds the operation threshold value, the control unit 43 changes the upper limit current value of the power generation current value of the fuel cell 21. With this configuration, even when the methane concentration of the raw fuel gas is low, there is no need to increase the operation value of the raw fuel supply unit 32. With this configuration, the operating efficiency of the fuel cell device 20 can be improved.

[0076] Furthermore, in the fuel cell device 20 according to this embodiment, when the methane concentration in the raw fuel gas is estimated to be below the concentration threshold and the power generation current value of the fuel cell 21 exceeds the current threshold, the control device 40 changes the upper limit current value of the fuel cell 21. For example, when this current threshold is a first current threshold, the control unit 43 proceeds to the process of step S3 when it determines that the power generation current value of the fuel cell 21 is equal to or greater than the first current threshold (step S2: NO). In the processes from step S3 onward, for example, in the processes of steps S8, S10, S15, and S16, the control unit 43 changes the upper limit current value of the power generation current value of the fuel cell 21. As described above, when the methane concentration in the raw fuel gas is estimated to be below the concentration threshold, if the fuel cell 21 is to generate power while the upper limit current value of the fuel cell 21 is kept constant, the operating value of the raw fuel supply unit 32 must be increased compared to when a reference raw fuel gas is used. In response to this, when the methane concentration of the raw fuel gas is estimated to be below the concentration threshold and the power generation current value of the fuel cell 21 exceeds the current threshold, the control unit 43 changes the upper limit current value of the fuel cell 21. With this configuration, even when the methane concentration of the raw fuel gas is low, there is no need to increase the operating value of the raw fuel supply unit 32. As a result, the operating efficiency of the fuel cell device 20 can be improved.

[0077] Furthermore, when changing the upper limit current value of the fuel cell 21, the control device 40 according to this embodiment may change the upper limit current value of the fuel cell 21 to the current power generation value of the fuel cell 21. For example, in the process of step S3, the control unit 43 acquires the current power generation value of the fuel cell 21 and sets the upper limit current value to the current power generation value. With this configuration, the fuel cell 21 can generate power at the maximum power generation value, with the current power generation current value as the upper limit.

[0078] Furthermore, the control device 40 according to this embodiment may change the operation value of the raw fuel supply unit 32 to a set value when the operation value of the raw fuel supply unit 32 exceeds the operation threshold. The set value may be smaller than the maximum operation value of the raw fuel supply unit 32. For example, when the control unit 43 determines that the operation value of the raw fuel supply unit 32 exceeds the operation threshold (step S4: YES), the control unit 43 may change the operation value of the raw fuel supply unit 32 to the set value. Here, if the raw fuel supply unit 32 attempts to supply raw fuel gas to the reformer 22 at the maximum operation value, fluctuations in the flow rate of the raw fuel gas from the raw fuel supply unit 32 may occur. By changing the operation value of the raw fuel supply unit 32 to a set value smaller than the maximum operation value, the possibility of fluctuations in the flow rate of the raw fuel gas from the raw fuel supply unit 32 can be reduced. As a result, the fuel cell 21 can operate stably.

[0079] Furthermore, the control device 40 according to this embodiment may change the flow rate of the raw fuel gas supplied to the fuel cell 21 by the raw fuel supply unit 32 so that it becomes a set amount. For example, in the process of step S3, the control unit 43 sets the flow rate of the raw fuel gas supplied from the raw fuel supply unit 32 to the reformer 22 to the set amount. The set amount is smaller than the maximum flow rate of the raw fuel gas that can be supplied by the raw fuel supply unit 32. With this configuration, as described above, it is possible to reduce the possibility of fluctuations in the flow rate of the raw fuel gas from the raw fuel supply unit 32. As a result, the fuel cell 21 can operate stably.

[0080] Furthermore, the control device 40 according to this embodiment may increase the flow rate of the raw fuel gas supplied to the fuel cell 21 by the raw fuel supply unit 32 when the operation value of the raw fuel supply unit 32 is below the operation threshold. For example, when the control unit 43 determines that the operation value of the fuel supply unit 32 is equal to or lower than the operation threshold (step S4: NO), the control unit 43 increases the flow rate of the raw fuel gas supplied to the reformer 22 of the fuel cell 21 by the raw fuel supply unit 32 in the processing of step S6. With this configuration, when the operation value of the raw fuel supply unit 32 is below the operation threshold, the flow rate of the raw fuel gas supplied to the fuel cell 21 can be increased. As a result, the fuel cell 21 can operate stably.

[0081] Furthermore, the fuel cell device 20 according to this embodiment may further include a combustion unit 24 that combusts unreacted fuel gas in the fuel cell 21. The control device 40 may acquire the current temperature of the combustion unit 24 when the operation value of the raw fuel supply unit 32 exceeds the operation threshold. For example, when the control unit 43 determines that the drive rate of the raw fuel supply unit 32 exceeds the drive threshold (step S4: YES), the control unit 43 proceeds to the process of step S7. In the processes after step S7, for example, in the processes of steps S9, S11, and S17, the control unit 43 acquires the current temperature of the combustion unit 24 by acquiring the detection result of the current temperature of the combustion unit 24 from the temperature sensor 25. By acquiring the temperature of the combustion unit 24, it is possible to control the raw fuel supply unit 32 and then execute appropriate processing according to the temperature of the combustion unit 24.

[0082] Furthermore, the control device 40 according to this embodiment may reduce the upper limit current value of the fuel cell 21 when the temperature of the combustion unit 24 falls below the first temperature. For example, when the control unit 43 determines that the temperature of the combustion unit 24 falls below the first temperature (step S9: NO), it reduces the upper limit current value in the processing of step S10. As described above, reducing the upper limit current value can increase the amount of unreacted fuel gas in the fuel cell 21. This increase in unreacted fuel gas increases the temperature of the combustion unit 24, reducing the possibility of the combustion unit 24 misfiring. As a result, the fuel cell 21 can be operated stably.

[0083] Furthermore, the control device 40 according to this embodiment may acquire the current power generation value of the fuel cell 21 when the temperature of the combustion unit 24 is equal to or higher than the second temperature. For example, when the control unit 43 determines that the temperature of the combustion unit 24 exceeds the second temperature (step S17: NO), it acquires the current power generation value of the fuel cell 21 in the processing of step S12. By acquiring the current power generation value of the fuel cell 21 when the temperature of the combustion unit 24 is equal to or higher than the second temperature, the control unit 43 can execute appropriate processing according to the power generation value of the fuel cell 21.

[0084] Furthermore, the control device 40 according to this embodiment may reduce the flow rate of the raw fuel gas supplied to the fuel cell 21 by the raw fuel supply unit 32 when the acquired power generation value of the fuel cell 21 is equal to or greater than the first power value. For example, when the control unit 43 determines that the power generation value of the fuel cell 21 is equal to or greater than the first power value (step S12: YES), the control unit 43 reduces the flow rate of the raw fuel gas supplied to the reformer 22 of the fuel cell 21 by the raw fuel supply unit 32 in the processing of step S13. As described above, by reducing the flow rate of the raw fuel gas, the amount of unreacted fuel gas in the fuel cell 21 can be reduced. By reducing the amount of unreacted fuel gas in the fuel cell 21, the temperature of the combustion unit 24 can be lowered. As a result, the fuel cell 21 can be operated stably.

[0085] Furthermore, the control device 40 according to this embodiment may reduce the upper limit current value when the temperature of the combustion unit 24 is equal to or lower than a third temperature. For example, when the control unit 43 determines that the temperature of the combustion unit 24 is equal to or lower than the third temperature (step S7: YES), the control unit 43 reduces the upper limit current value in the processing of step S8. By reducing the upper limit current value, as described above, the power generation value of the fuel cell 21 can be reduced, and the amount of unreacted fuel gas in the fuel cell 21 can be increased. By increasing the amount of unreacted fuel gas in the fuel cell 21, the temperature of the combustion unit 24 can be increased. As a result, the fuel cell 21 can be operated stably.

[0086] Furthermore, the control device 40 according to this embodiment may operate the fuel cell 21 in its current state if the temperature of the combustion unit 24 is equal to or higher than the fourth temperature, the acquired power generation value of the fuel cell 21 is below the first power value, and the upper limit current value is equal to or higher than the determination threshold. For example, if the temperature of the combustion unit 24 is equal to or higher than the fourth temperature (step S11: YES) and the control unit 43 determines that the power generation value of the fuel cell 21 is below the first power value (step S12: NO), the control unit 43 executes the process of step S14. If the control unit 43 determines that the upper limit current value exceeds the determination threshold (step S14: NO), and the upper limit current value is already at its maximum value, the control unit 43 leaves the upper limit current value at its maximum value. In such a case, operating the fuel cell 21 in its current state allows the fuel cell 21 to operate stably.

[0087] For example, an embodiment is also possible in which a general-purpose computer functions as at least one of the power conversion device 10 and the fuel cell device 20 according to the above-described embodiments. Specifically, a program describing the processing content for realizing each function of at least one of the power conversion device 10 and the fuel cell device 20 according to the above-described embodiments is stored in the memory of the general-purpose computer, and the program is read and executed by a processor. Therefore, the present disclosure can also be realized as a program executable by a processor, or a non-transitory computer-readable medium storing the program.

[0088] In one embodiment, (1) a fuel cell device includes: a fuel cell; a raw fuel supply unit that supplies raw fuel gas having a fluctuating methane concentration to the fuel cell; and a control device, wherein the control device changes an upper limit current value, which is an upper limit value of the power generation current value of the fuel cell, when the operation value of the raw fuel supply unit exceeds an operation threshold value.

[0089] In one embodiment, (2) a fuel cell device includes: a fuel cell; a raw fuel supply unit that supplies raw fuel gas having a fluctuating methane concentration to the fuel cell; and a control device, wherein the control device changes an upper limit current value, which is an upper limit value of the power generation current value of the fuel cell, when the methane concentration of the raw fuel gas is estimated to be below a concentration threshold and the power generation current value of the fuel cell exceeds a current threshold.

[0090] (3) In the fuel cell device described in (1) or (2) above, when changing the upper limit current value, the control device may change the upper limit current value to a current value currently generated by the fuel cell.

[0091] (4) In the fuel cell device described in (1) above, when the operating value of the raw fuel supply unit exceeds the operating threshold, the control device changes the operating value of the raw fuel supply unit to a set value, and the set value may be smaller than the maximum operating value of the raw fuel supply unit.

[0092] (5) In the fuel cell device described in (2) or (3) above, the control device changes the flow rate of the raw fuel gas supplied to the fuel cell by the raw fuel supply unit to a set amount, and the set amount may be smaller than the maximum flow rate of the raw fuel gas that can be supplied by the raw fuel supply unit.

[0093] (6) In the fuel cell device described in (5) above, the control device may increase the flow rate of the raw fuel gas supplied to the fuel cell by the raw fuel supply unit when the operating value of the raw fuel supply unit is below an operating threshold value.

[0094] (7) In the fuel cell device described in (4) or (6) above, the device further includes a combustion unit that combusts unreacted fuel gas in the fuel cell, and the control device may acquire the current temperature of the combustion unit when the operation value of the raw fuel supply unit exceeds the operation threshold value.

[0095] (8) In the fuel cell device described in (7) above, the control device may reduce the upper limit current value when the acquired temperature of the combustion section is equal to or lower than a third temperature.

[0096] (9) In the fuel cell device described in (7) or (8) above, the control device may reduce the upper limit current value when the acquired temperature of the combustion section is lower than a first temperature.

[0097] (10) In the fuel cell device described in any one of (7) to (9) above, the control device may determine whether the current upper limit current value exceeds a determination threshold value when the acquired temperature of the combustion section is equal to or higher than a fourth temperature and the acquired current power generation value of the fuel cell is lower than a first power value.

[0098] (11) In the fuel cell device described in (10) above, the control device may increase the current upper limit current value when the current upper limit current value is equal to or less than a determination threshold value.

[0099] (12) In the fuel cell device described in (10) above, when the current upper limit current value exceeds a determination threshold, the control device may set the current upper limit current value to a maximum value.

[0100] (13) In the fuel cell device described in any one of (7) to (12) above, the control device may reduce the flow rate of the raw fuel gas supplied to the fuel cell by the raw fuel supply unit when the acquired temperature of the combustion unit is equal to or higher than a fourth temperature and the acquired current power generation value of the fuel cell is equal to or higher than a first power value.

[0101] (14) In the fuel cell device described in any one of (7) to (13) above, the control device may acquire a current power generation value of the fuel cell when the acquired temperature of the combustion section is equal to or higher than a second temperature, and determine whether the acquired power generation value is equal to or higher than the first power value.

[0102] In this disclosure, descriptions such as "first" and "second" are identifiers for distinguishing the configuration. In this disclosure, the configurations distinguished by descriptions such as "first" and "second" can have their numbers interchanged. For example, the first temperature can have its identifiers "first" and "second" interchanged with the second temperature. The identifiers are interchanged simultaneously. The configurations remain distinguished even after the identifiers are interchanged. Identifiers may be deleted. A configuration from which an identifier has been deleted is distinguished by a symbol. The identifiers "first" and "second" in this disclosure should not be used solely to interpret the order of the configurations or to justify the existence of an identifier with a smaller number.

[0103] 1: fuel cell system, 2: load group, 10: power conversion device, 11: current sensor, 20: fuel cell device, 21: fuel cell, 22: reformer, 23: cell stack, 24: combustion section, 25: temperature sensor, 30: reforming water supply section, 31: supply line, 32: raw fuel supply section, 33: supply line, 34: flow rate sensor, 35: air supply section, 36: supply line, 37: flow rate sensor, 40: control device, 41: communication section, 42: memory section, 43: control section

Claims

1. A fuel cell device comprising: a fuel cell; a raw fuel supply unit that supplies raw fuel gas having a fluctuating methane concentration to the fuel cell; and a control device, wherein the control device changes an upper limit current value, which is an upper limit value of the power generation current value of the fuel cell, when the operation value of the raw fuel supply unit exceeds an operation threshold value.

2. A fuel cell device comprising: a fuel cell; a raw fuel supply unit that supplies raw fuel gas having a fluctuating methane concentration to the fuel cell; and a control device, wherein the control device changes an upper limit current value that is an upper limit of the power generation current value of the fuel cell when the methane concentration of the raw fuel gas is estimated to be below a concentration threshold and the power generation current value of the fuel cell exceeds a current threshold.

3. The fuel cell device according to claim 1 or 2, wherein when the control device changes the upper limit current value, the control device changes the upper limit current value to the current value of the current generated by the fuel cell.

4. The fuel cell device according to claim 1, wherein the control device changes the operating value of the raw fuel supply unit to a set value when the operating value of the raw fuel supply unit exceeds the operating threshold value, and the set value is smaller than the maximum operating value of the raw fuel supply unit.

5. A fuel cell device as described in claim 2 or 3, wherein the control device changes the flow rate of the raw fuel gas supplied to the fuel cell by the raw fuel supply unit to a set amount, and the set amount is smaller than the maximum flow rate of the raw fuel gas that can be supplied by the raw fuel supply unit.

6. A fuel cell device according to claim 5, wherein the control device increases the flow rate of the raw fuel gas supplied to the fuel cell by the raw fuel supply unit when the operating value of the raw fuel supply unit is equal to or lower than an operating threshold value.

7. A fuel cell device as described in claim 4 or 6, further comprising a combustion unit that combusts unreacted fuel gas in the fuel cell, wherein the control device acquires the current temperature of the combustion unit when the operating value of the raw fuel supply unit exceeds the operating threshold value.

8. The fuel cell device according to claim 7, wherein the control device reduces the upper limit current value when the acquired temperature of the combustion section is equal to or lower than a third temperature.

9. The fuel cell device according to claim 7 or 8, wherein the control device reduces the upper limit current value when the acquired temperature of the combustion section falls below a first temperature.

10. A fuel cell device described in any one of claims 7 to 9, wherein the control device determines whether the current upper limit current value exceeds a judgment threshold when the acquired temperature of the combustion section is equal to or higher than a fourth temperature and the acquired current power generation value of the fuel cell is lower than a first power value.

11. The fuel cell device according to claim 10, wherein the control device increases the current upper limit current value when the current upper limit current value is equal to or less than a determination threshold value.

12. The fuel cell device according to claim 10, wherein the control device sets the current upper limit current value to a maximum value when the current upper limit current value exceeds a determination threshold value.

13. A fuel cell device described in any one of claims 7 to 12, wherein the control device reduces the flow rate of the raw fuel gas supplied to the fuel cell by the raw fuel supply unit when the acquired temperature of the combustion unit is equal to or higher than a fourth temperature and the acquired current power generation value of the fuel cell is equal to or higher than a first power value.

14. A fuel cell device described in any one of claims 7 to 13, wherein the control device, when the acquired temperature of the combustion section is equal to or higher than a second temperature, acquires the current power generation value of the fuel cell, and determines whether the acquired power generation value is equal to or higher than the first power value.

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