Control device, fuel cell system, and method for starting a fuel cell system

Abstract

This invention provides a control device for a fuel cell system that can extend the replacement period of fuel cells until they have deteriorated further, thereby reducing the cost burden on the user. [Solution] The control device 44 of the fuel cell system 10 includes a degradation determination unit 46 that determines the degradation value of the multiple fuel cells 12 when the temperature of the multiple fuel cells 12 is below a predetermined level, and a forced low-temperature start unit 48 that performs low-temperature start control to forcibly start the fuel cell 12 with the least degradation and generate electricity.

Description

Technical Field

[0001] The present disclosure relates to a control device, a fuel cell system, and a method for starting a fuel cell system.

Background Art

[0002] A fuel cell system equipped with a plurality of fuel cells is expected to be widely used in commercial vehicles such as trucks and buses, and industrial applications such as stationary power generation devices. In such a fuel cell system, as the operating time of the fuel cell increases, the fuel cell gradually deteriorates, resulting in a decrease in output current (electric power) and the like. Therefore, it is necessary to replace the deteriorated fuel cell.

[0003] Regarding the prediction of the deterioration value of a fuel cell, for example, the method disclosed in Japanese Patent Application Laid-Open No. 2023-150885 is known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] There are variations in the lifespan of each fuel cell, and variations occur in the progress of deterioration. When the variation in the deterioration of the fuel cell becomes large, an imbalance occurs in the output of each fuel cell in the fuel cell system, making its control difficult. Therefore, it is necessary to replace the deteriorated fuel cell. However, when replacing the fuel cell, a downtime occurs during which commercial vehicles and stationary power generation devices cannot be used, imposing a significant cost burden on the user. Therefore, in a fuel cell system, it is desirable to reduce the replacement frequency of the fuel cell as much as possible.

[0006] The present disclosure aims to solve the above-described problems. [Means for solving the problem]

[0007] A first aspect of the present disclosure is a control device for controlling a plurality of fuel cells, comprising: a degradation determination unit that determines the degradation value of the plurality of fuel cells when the temperature of the plurality of fuel cells is below a predetermined level; and a forced low-temperature start unit that performs low-temperature start control to forcibly start the fuel cell with the least degradation and generate electricity.

[0008] A second aspect of this disclosure is a fuel cell system comprising a control device according to the first aspect and a plurality of fuel cells.

[0009] A third aspect of the present disclosure is a method for starting a fuel cell system comprising a plurality of fuel cells and a control device for controlling the fuel cells, wherein when the temperature of the plurality of fuel cells is below a predetermined level, a degradation determination unit of the control device determines the degradation value of the plurality of fuel cells, and a forced low-temperature start unit of the control device performs low-temperature start control to forcibly start the fuel cell with the least degradation to generate electricity. [Effects of the Invention]

[0010] According to this disclosure, the degradation of multiple fuel cells progresses evenly. Therefore, replacement of fuel cells due solely to output imbalance becomes unnecessary, and the replacement period can be extended until the fuel cells have become more degraded, thereby reducing the cost burden on the user. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a diagram showing the main components of a fuel cell system according to an embodiment. [Figure 2] Figure 2 is a block diagram showing the electrical connection relationships of the fuel cell system according to the embodiment. [Figure 3] Figure 3 is a graph showing an example of the distribution of remaining lifespan of a fuel cell at the time of its initial manufacture. [Figure 4]Figure 4 is a flowchart showing the startup method of the fuel cell system according to the embodiment. [Figure 5] Figure 5 is an explanatory diagram showing the determination of whether or not low-temperature startup control is necessary based on an example of the distribution of remaining lifespans of four fuel cells. [Modes for carrying out the invention]

[0012] As shown in Figure 1, the fuel cell system 10 according to this embodiment includes a plurality of fuel cells 12, a frame 14, a container 16, a refrigerant flow path 18, a radiator 20, an exhaust passage 22, a heat pump 28, an air conditioner 30, and a plurality of heaters 32. The plurality of fuel cells 12 are, for example, polymer electrolyte fuel cells, which generate electricity by reacting hydrogen gas supplied to the anode with air supplied to the cathode. The plurality of fuel cells 12 are mounted on the frame 14. The frame 14, which is equipped with the plurality of fuel cells 12, is housed inside the housing chamber 16a of the container 16.

[0013] Each fuel cell 12 is connected to a refrigerant flow path 18. The refrigerant flow path 18 has a forward path 18a that supplies coolant from the radiator 20 to the fuel cell 12, and a return path 18b that returns coolant from the fuel cell 12 to the radiator 20. The forward path 18a branches off and connects to the inlet port 12a of each fuel cell 12. The return path 18b connects to the outlet port 12b of each fuel cell 12. The return path 18b merges with the radiator 20 and returns to the radiator 20. The refrigerant flow path 18 forms a flow path that circulates coolant between the radiator 20 and the fuel cell 12.

[0014] An exhaust passage 22 extends from each fuel cell 12. The exhaust passage 22 mainly carries exhaust gas from the cathode. The exhaust passage 22 carries air that was not used in the reaction in the fuel cell 12 (cathode off gas), hydrogen gas purged from the anode side, and water vapor. Since the fuel cell 12 is supplied with pressurized air by the air compressor contained in the auxiliary equipment 12d (see Figure 2), the exhaust gas that flows through the exhaust passage 22 is at a pressure higher than atmospheric pressure.

[0015] A branch passage 26 is connected to the exhaust passage 22 via a valve 24. The branch passage 26 is connected to the exhaust passage 22 downstream of the valve 24 via a heat pump 28. The heat pump 28 constitutes part of the warming device 29 of this embodiment. The heat pump 28 is driven by exhaust gas supplied from the exhaust passage 22. The high-temperature part 28a of the heat pump 28 is in thermal contact with the forward passage 18a of the refrigerant passage 18. The heat pump 28 heats the coolant flowing through the forward passage 18a with heat recovered from a predetermined heat source, such as the exhaust gas of the fuel cell 12, thereby warming multiple fuel cells 12 through the coolant when starting from a low temperature.

[0016] The containment chamber 16a of the container 16 is equipped with an air conditioner 30, which is part of the warming device 29. When starting from a low temperature, the air conditioner 30 supplies warm air to the inside of the containment chamber 16a, thereby warming the fuel cells 12 housed in the containment chamber 16a. In addition, each fuel cell 12 is fitted with a heater 32, which is part of the warming device 29. The heater 32 is equipped with a resistance heating element or the like, and warms the fuel cell 12 from the casing when starting from a low temperature. Note that either the air conditioner 30 or the heater 32 may be omitted.

[0017] As shown in Figure 2, the fuel cell system 10 further comprises connection wiring 34, power wiring 36, an auxiliary battery 38, a fuel cell control unit 40 (FCECU), a valve control unit 42, and a control device 44. The connection wiring 34 is wiring that extends from the output terminal 12c of each fuel cell 12 and connects the output terminal 12c of the fuel cell 12 to the power wiring 36. Each connection wiring 34 is provided with a reverse current prevention circuit 34a. The reverse current prevention circuit 34a prevents current from flowing back into the fuel cell 12 when the fuel cell 12 is not running, thereby preventing the application of high voltage to the power generation cell.

[0018] The power distribution line 36 is connected to the output terminals 12c of a plurality of fuel cells 12 via the connection wiring 34. The power generated by the fuel cells 12 is output to devices or facilities that consume power through the output section 36a of the power distribution line 36. Also, an auxiliary battery 38 and a heater 32 are connected to the power distribution line 36. Further, the auxiliary machines 12d of each fuel cell 12 are also connected to the power distribution line 36 via a path different from the connection wiring 34.

[0019] The auxiliary battery 38 is connected to the power distribution line 36. The auxiliary battery 38 supplies the power necessary for the operation of the auxiliary machine 12d at the time of startup or the like. Also, the auxiliary battery 38 supplies power to the air conditioner 30 and the heater 32 when performing a heating operation. The auxiliary battery 38 is charged through the power distribution line 36 during the operation of the fuel cell 12.

[0020] The fuel cell control unit 40 is provided in each fuel cell 12. The fuel cell control unit 40 controls the operation of starting, stopping, and adjusting the output of the fuel cell 12 by controlling the auxiliary machine 12d. Also, the fuel cell control unit 40 detects and stores the number of uses of each auxiliary machine component of the auxiliary machine 12d, the number of startups of the fuel cell 12, and the cumulative operation time of the fuel cell 12.

[0021] The valve control unit 42 controls the operation of the valve 24 (three-way valve) provided in the exhaust passage 22. When low-temperature startup control is performed, the valve control unit 42 drives the heat pump 28 by guiding the exhaust gas in the exhaust passage 22 to the heat pump 28.

[0022] The control device 44 controls each part of the fuel cell system 10 including the fuel cell control unit 40, the air conditioner 30, the heater 32, and the valve control unit 42. The control device 44 includes a deterioration determination unit 46, a forced low-temperature startup unit 48, and a heating control unit 50. When the temperature of the fuel cell 12 falls below a predetermined minimum startup temperature, the control device 44 causes the deterioration determination unit 46 to determine the deterioration values of the plurality of fuel cells 12.

[0023] The degradation value is determined based on, for example, the number of times the auxiliary components of the auxiliary equipment 12d of the fuel cell 12 are used, the number of times the fuel cell 12 is started, the cumulative operating time of the fuel cell 12, or the voltage value when a predetermined specified current value is output to the fuel cell 12. The degradation determination unit 46 determines the degradation value as, for example, an estimated value of the operating time (remaining lifespan) until the fuel cell 12 can no longer generate sufficient power. Details of the method for estimating the remaining lifespan of the fuel cell 12 are described in Japanese Patent Application Publication No. 2023-150885, etc.

[0024] Furthermore, the degradation determination unit 46 determines the degree of variation in the degradation values ​​of multiple fuel cells 12. The remaining lifespan of the fuel cells 12 at the time of shipment shows the distribution shown in Figure 3. Note that the remaining lifespan on the horizontal axis of Figure 3 is an example for the sake of explanation. The remaining lifespan of the fuel cells 12 generally follows a normal distribution as shown in the figure. Therefore, the memory unit 44b, which will be described later, stores the value of the standard deviation σ obtained from the distribution of the remaining lifespan of the fuel cells 12 at the time of shipment. The degradation determination unit 46 determines the degree of variation in the degradation values ​​of the fuel cells 12 by reading the value of the standard deviation σ from the memory unit 44b. Furthermore, the degradation determination unit 46 detects fuel cells 12 that have a remaining lifespan that is above the standard deviation σ of the average remaining lifespan of multiple fuel cells 12 as targets for low-temperature startup control.

[0025] As another example, the degradation determination unit 46 may determine the degree of variation in the degradation values ​​of the multiple fuel cells 12 by taking the standard deviation σ1 of the remaining lifespan of the multiple fuel cells 12 installed, instead of the standard deviation σ of the remaining lifespan at the time of shipment. In the example shown in Figures 1 and 2, the degradation determination unit 46 calculates the average value and the standard deviation σ1 from the remaining lifespan of each of the four fuel cells 12. The degradation determination unit 46 may also detect fuel cells 12 having a remaining lifespan that exceeds the value of the standard deviation σ1 relative to the average value as targets for low-temperature startup control.

[0026] As another example, the degradation determination unit 46 may detect the fuel cell 12 with the longest remaining lifespan among the multiple fuel cells 12 installed as the target for low-temperature startup control.

[0027] The forced low-temperature startup unit 48 performs low-temperature startup control on fuel cells 12 that the degradation determination unit 46 has detected as targets for low-temperature startup control. Low-temperature startup control is a control that starts power generation of the fuel cell 12 at a temperature lower than a predetermined minimum startup temperature. When the FC stack 12e (fuel cell stack) generates power at a temperature lower than the predetermined minimum startup temperature, degradation of the electrolyte membrane, catalyst, etc. progresses. Therefore, in normal startup, the warming device 29 heats multiple fuel cells 12 to suppress the progression of degradation of the fuel cells 12. In this embodiment, the forced low-temperature startup unit 48 performs low-temperature startup control on fuel cells 12 whose degradation value is lower than a predetermined value, thereby actively promoting the degradation of the fuel cell 12.

[0028] Depending on the design of the FC stack 12e, but not limited to, the minimum start temperature may be set to an appropriate temperature in the range of, for example, -5°C to 5°C. To more effectively reduce the remaining lifespan of the fuel cell 12 subject to low-temperature start control, the forced low-temperature start unit 48 may perform low-temperature start control only when the temperature of the fuel cell 12 is below, for example, -5°C.

[0029] When low-temperature startup control is performed, the control device 44 switches the valve 24 (Figure 1) via the valve control unit 42 to supply exhaust gas to the heat pump 28.

[0030] The heating control unit 50 controls the air conditioner 30 and the heater 32 to heat the fuel cell 12, which is normally started up, to a predetermined temperature that exceeds the minimum start temperature.

[0031] The control device 44 described above is composed of an arithmetic unit 44a and a storage unit 44b. The arithmetic unit 44a may be composed of a processor, i.e., a processing circuit, such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit).

[0032] The calculation unit 44a includes a degradation determination unit 46, a forced low-temperature startup unit 48, and a heating control unit 50. The degradation determination unit 46, the forced low-temperature startup unit 48, and the heating control unit 50 can be realized by the calculation unit 44a executing a program stored in the storage unit 44b.

[0033] Furthermore, at least a portion of the degradation determination unit 46, the forced low-temperature startup unit 48, and the heating control unit 50 may be implemented by an integrated circuit such as an ASIC (Application Specific Integrated Circuit). Also, at least a portion of the degradation determination unit 46, the forced low-temperature startup unit 48, and the heating control unit 50 may be configured by an electronic circuit including discrete devices.

[0034] The storage unit 44b may consist of volatile memory and non-volatile memory. Examples of volatile memory include RAM (Random Access Memory). This volatile memory is used as the working memory of the processor and temporarily stores data necessary for processing or calculations. Examples of non-volatile memory include ROM (Read Only Memory) and flash memory. This non-volatile memory is used as storage memory and stores programs, tables, maps, etc. At least a part of the storage unit 44b may be provided in the processor, integrated circuit, etc. as described above.

[0035] The fuel cell system 10 of this embodiment is configured as described above. The operation of the fuel cell system 10 during startup will be described below.

[0036] As shown in Figure 4, the fuel cell system 10 receives a power generation instruction in step S10. Upon receiving the power generation instruction, the control device 44 proceeds to step S12 to start the multiple fuel cells 12.

[0037] In step S12, the control device 44 checks the status of each part of the fuel cell system 10. For example, the control device 44 confirms that there are no malfunctions in each part of the fuel cell system 10 and that the power wiring 36 is maintained at a predetermined voltage.

[0038] Next, the control device 44 performs a startup determination (step S14). In the startup determination (step S14), the control device 44 determines whether the temperature of the fuel cell 12 is below a predetermined minimum startup temperature. The minimum startup temperature in the startup determination (step S14) can be, for example, -5°C. The fuel cell 12 deteriorates relatively quickly when started at a temperature below -5°C. If the control device 44 determines that the temperature of the fuel cell 12 is above the predetermined minimum startup temperature (for example, -5°C), it proceeds to step S16.

[0039] In step S16, the control device 44 performs a normal startup on all fuel cells 12 installed in the fuel cell system 10. That is, the control device 44 outputs a startup command to the fuel cell control unit 40 installed in each fuel cell 12. Upon receiving the startup command, the fuel cell control unit 40 activates the auxiliary equipment 12d to supply air to the cathode of the FC stack 12e and hydrogen gas to the anode. The control device 44 also drives the pump of the radiator 20 to circulate the coolant in the refrigerant passage 18. As a result, multiple fuel cells 12 are started, power generation by multiple fuel cells 12 begins, and the startup process is completed. Since the startup of the fuel cells 12 in this manner is started at a temperature above a predetermined minimum startup temperature, the reduction in the remaining lifespan of the FC stack 12e and auxiliary equipment 12d is relatively small.

[0040] On the other hand, if the control device 44 determines in the startup determination step (step S14) that the temperature of the fuel cell 12 is below a predetermined minimum startup temperature, the process proceeds to step S18.

[0041] In step S18, the degradation determination unit 46 of the control device 44 determines the degradation value of the multiple fuel cells 12 installed in the fuel cell system 10. In this embodiment, the degradation determination unit 46 obtains the remaining lifespan of each fuel cell 12 as a degradation value from the fuel cell control unit 40, based on the cumulative operating time of each fuel cell 12, the number of times the fuel cell 12 has been started, and the number of times the auxiliary components included in the auxiliary equipment 12d of the fuel cell 12 have been used.

[0042] Here, the cumulative operating time and number of starts of the fuel cell 12 are parameters that mainly reflect the degree of degradation of the catalyst and electrolyte membrane contained in the FC stack 12e. As these times or numbers increase, the degradation of the FC stack 12e progresses, and the remaining lifespan of the fuel cell 12 shortens. In addition, auxiliary components, such as sealing members like valves, deteriorate with increasing usage, so an increase in the number of uses of auxiliary components also shortens the remaining lifespan of the fuel cell 12 until failure. The degradation determination unit 46 determines the remaining lifespan of the fuel cell 12 as a degradation value based on the element with the shortest remaining lifespan among the above determination factors. Note that the remaining lifespan is one indicator value of the degradation value. The degradation determination unit 46 may also handle the degradation value of the fuel cell 12 using parameters other than the remaining lifespan.

[0043] Next, the process proceeds to step S20, where the degradation determination unit 46 determines whether or not a low-temperature start-up is necessary for the fuel cell 12. Here, the degradation determination unit 46 calculates the degree of variation based on the distribution of degradation values ​​of the fuel cell 12. For example, as shown in Figure 3, the storage unit 44b may store the value of the standard deviation σ of the distribution of the remaining lifespan of the fuel cell 12 at the time of manufacture, which has been determined in advance, as the degree of variation. The degradation determination unit 46 can obtain the degree of variation of degradation values ​​by reading this standard deviation σ of the remaining lifespan from the storage unit 44b.

[0044] The degradation determination unit 46 may also determine the degree of variation by using the value of the standard deviation σ1 obtained from the remaining life times of multiple fuel cells 12 installed in the fuel cell system 10.

[0045] In step S20, the degradation determination unit 46 determines whether low-temperature startup control is necessary. In step S20, the degradation determination unit 46 determines whether there are any fuel cells 12 whose degradation value is small and deviates from the previously determined degree of variation, based on the average value of the degradation values ​​of the multiple fuel cells 12. That is, the degradation determination unit 46 determines whether there are any fuel cells 12 whose remaining lifespan is longer than the standard deviation σ, σ1, based on the average value of the remaining lifespan of the multiple fuel cells 12.

[0046] For example, consider the case shown in Figure 5, where the remaining lifespans of four fuel cells 12, numbered 1 to 4, are 1550 hours, 1500 hours, 1600 hours, and 2000 hours, respectively, and the standard deviation σ is 300 hours. In this case, the average of the remaining lifespans of the four fuel cells 12 is 1662.5 hours. The value obtained by adding the standard deviation σ to the average is 1962.5 hours. Therefore, fuel cell 4 12 is determined to require low-temperature start control because its remaining lifespan exceeds this value.

[0047] In step S20 of Figure 4, if the degradation determination unit 46 detects a fuel cell 12 with a degradation value that deviates from the variation degree and is small (YES), the control device 44 proceeds to step S22. That is, if it is determined to be YES in step S20, low-temperature startup control is performed. On the other hand, if the degradation determination unit 46 does not detect a fuel cell 12 with a degradation value that deviates from the variation degree and is small (NO), the control device 44 proceeds to step S24. That is, if it is determined in step S20 that there are no fuel cells 12 with low degradation that deviates from the variation degree (NO), low-temperature startup control is not performed.

[0048] In this way, by using the degree of variation as a threshold for whether or not to perform low-temperature startup control, the frequency of low-temperature startup control can be suppressed, and excessive deterioration of multiple fuel cells 12 can be prevented. If such a threshold is not set, the fuel cell 12 with the smallest deterioration value will be replaced, and low-temperature startup control will be repeatedly performed, leading to excessive deterioration.

[0049] Furthermore, from the perspective of preventing excessive degradation, the threshold for whether or not to perform low-temperature startup control is not limited to the degree of variation in the degradation value (remaining lifespan). In this embodiment, the degradation determination unit 46 may determine whether or not low-temperature startup control is necessary (step S20) based on whether or not there is a fuel cell 12 having a remaining lifespan that exceeds a predetermined threshold appropriately set with respect to the average value of the remaining lifespan, instead of the degree of variation in the remaining lifespan.

[0050] In step S22, the forced low-temperature start unit 48 of the control device 44 performs low-temperature start control on fuel cells 12 whose degradation values ​​are less than the normal variation. Low-temperature start control forces the fuel cell 12 to start generating electricity without waiting for the temperature of the fuel cell 12 to rise due to warm-up. Specifically, the forced low-temperature start unit 48 operates the auxiliary equipment 12d at a temperature below the minimum start temperature to supply air and hydrogen gas to the FC stack 12e of the fuel cell 12 and start generating electricity.

[0051] If the fuel cell 12 is started at a temperature below the predetermined minimum starting temperature, the degradation of the FC stack 12e will progress. As a result, the degradation value of the FC stack 12e that has a remaining lifespan exceeding the variation rate will increase, and the remaining lifespan of the fuel cell 12 will be shortened. When low-temperature starting control is initiated, the control device 44 operates a circulation pump (not shown) without rotating the fan of the radiator 20 to circulate the coolant inside the refrigerant passage 18.

[0052] Furthermore, the control device 44 switches the valve 24 shown in Figure 1 via the valve control unit 42 to guide the exhaust gas from the fuel cell 12 to the heat pump 28. The exhaust gas from the fuel cell 12 undergoing low-temperature startup control is guided to the heat pump 28, and the heat pump 28 is driven by the pressure of the exhaust gas. The heat pump 28 heats the coolant flowing through the refrigerant passage 18 and supplies the heated coolant to each fuel cell 12. This warms up the fuel cells 12 that are not undergoing low-temperature startup control.

[0053] In other words, in the low-temperature startup control (step S22) shown in Figure 4, the exhaust gas from the fuel cell 12 undergoing low-temperature startup control is used to warm up the other fuel cells 12. However, this embodiment is not limited to this, and under the control of the heating control unit 50, the air conditioner 30 or heater 32 may be driven to warm up the fuel cells 12 that are not undergoing low-temperature startup. This can speed up the startup of the other fuel cells 12.

[0054] Next, in step S26, the forced low-temperature startup unit 48 determines whether the temperature conditions meet predetermined conditions. The forced low-temperature startup unit 48 may, for example, determine whether the coolant temperature is 0°C or higher. Alternatively, the forced low-temperature startup unit 48 may determine whether the temperature of the FC stack 12e of the fuel cell 12 is above a predetermined temperature, such as 5°C or higher. In step S26, if the forced low-temperature startup unit 48 determines that either the coolant temperature or the FC stack 12e temperature, or both, are below the predetermined temperature (NO), it returns to step S18 and determines the degradation value of the fuel cell 12 again.

[0055] In other words, in this embodiment, the degradation value (remaining lifespan) of the fuel cell 12 undergoing low-temperature startup is continuously detected even while low-temperature startup control is being performed. This degradation value can be evaluated, for example, by referring to a map that shows the correlation between the current-voltage characteristics and the degradation value. If the remaining lifespan of the fuel cell 12 undergoing low-temperature startup falls below a predetermined degree of variation in step S20 (NO in step S20), the process moves to step S24 and the low-temperature startup control is stopped. This prevents excessive degradation of the fuel cell 12.

[0056] If the remaining lifespan of the fuel cell 12 undergoing low-temperature startup exceeds the predetermined variation in step S20 (YES in step S20), the low-temperature startup control is continued.

[0057] In step S26, if the forced low-temperature startup unit 48 determines that either the coolant temperature or the temperature of the FC stack 12e, or both, are above a predetermined temperature (YES), it terminates the low-temperature startup control and proceeds to step S28.

[0058] In step S28, the control device 44 performs a normal startup of the other fuel cells 12 that have not been started. Here, a normal startup is a control that starts power generation of the fuel cells 12 at a temperature higher than a predetermined minimum startup temperature. In this embodiment, the temperature at which a normal startup is started is set to a temperature even higher than the minimum startup temperature. With a normal startup, the degradation of the FC stack 12e of the fuel cell 12 is minimized, and the fuel cell 12 can be started while suppressing a decrease in the remaining lifespan of the FC stack 12e. With this, the startup control of the fuel cell 12 when low-temperature startup control is performed is completed.

[0059] On the other hand, if the degradation determination unit 46 determines in step S20 that low-temperature start control is unnecessary (NO), the process proceeds to step S24 to perform normal warm-up control. That is, under the control of the heating control unit 50, the control device 44 drives the air conditioner 30 and the heater 32 using power supplied from the auxiliary battery 38 in Figure 2. This heats all the fuel cells 12 in the fuel cell system 10. The control device 44 also starts circulating the coolant without rotating the fan of the radiator 20 as needed. The circulation of the coolant suppresses temperature variations among the multiple fuel cells 12. The control device 44 then proceeds to step S30.

[0060] In step S30, the control device 44 determines whether the temperature conditions meet predetermined conditions. The control device 44 may, for example, determine whether the coolant temperature is above a predetermined temperature, such as 0°C or higher. The control device 44 may also determine whether the temperature of the FC stack 12e of the fuel cell 12 is above a predetermined temperature, such as 5°C or higher. In step S30, if the control device 44 determines that either the coolant temperature or the FC stack 12e temperature, or both, are below the predetermined temperature (NO), it returns to step S24 and continues normal warm-up control.

[0061] On the other hand, in step S30, if the control device 44 determines that either the coolant temperature or the temperature of the FC stack 12e, or both, are above a predetermined temperature (YES), it terminates the normal warm-up control and proceeds to step S32.

[0062] In step S32, the control device 44 performs a normal startup of all fuel cells 12. This completes the startup control of the fuel cells 12 when low-temperature startup control is not performed.

[0063] As described above, the starting method of the fuel cell system 10 in this embodiment can suppress variations in the degradation values ​​of multiple fuel cells 12 by reducing the degradation of the FC stack 12e associated with starting at low temperatures. As a result, the fuel cell system 10 can reduce the frequency of replacing fuel cells 12 solely due to variations in their degradation values.

[0064] With regard to the above embodiments, the following additional information is disclosed.

[0065] (Note 1) This disclosure relates to a control device (44) for controlling a plurality of fuel cells (12), comprising: a degradation determination unit (46) for determining the degradation value of the plurality of fuel cells when the temperature of the plurality of fuel cells is below a predetermined level; and a forced low-temperature start unit (48) for executing low-temperature start control to forcibly start the fuel cell with the least degradation and generate electricity.

[0066] The control device described above can actively degrade fuel cells with low degradation values ​​by performing low-temperature startup control. This allows for the degradation of multiple fuel cells to progress evenly, thereby reducing the frequency of fuel cell replacements due solely to variations in fuel cell degradation.

[0067] (Note 2) The control device described in Appendix 1 may include a degradation determination unit that determines the degree of variation in the degradation values ​​of a plurality of fuel cells, and a forced low-temperature start unit that executes the low-temperature start control when the determined degree of variation is greater than or equal to a predetermined value. This control device can prevent excessive degradation of the fuel cells by reducing the frequency of low-temperature start control by not performing low-temperature start control up to a predetermined degree of variation.

[0068] (Note 3) The control device described in Appendix 2, wherein the degradation determination unit continues to determine the degree of variation even while the low-temperature startup control is being performed, and the forced low-temperature startup unit may stop the low-temperature startup control if the degree of variation falls below a predetermined value. This control device can minimize the progression of degradation of the fuel cell due to low-temperature startup control and prevent excessive degradation of the fuel cell.

[0069] (Note 4) The control device described in Appendix 2 may have a degradation determination unit that determines the degradation value of the fuel cell based on the cumulative operating time of the fuel cell, the number of times the fuel cell has been started, or the number of times the auxiliary components of the fuel cell have been used. This control device can evaluate the degradation value of the fuel cell including not only the FC stack but also the auxiliary components, and can evaluate a degradation value that is in line with the actual replacement timing.

[0070] (Note 5) The control device described in Appendix 2 may include a heating control unit (50) that heats the fuel cells that are not subjected to the low-temperature startup control when the temperatures of the multiple fuel cells are below a predetermined level and the determined degree of variation is equal to or greater than a predetermined value. This control device can shorten the startup time of the multiple fuel cells by heating the fuel cells that are not subjected to the low-temperature startup control.

[0071] (Note 6) In the control device described in Appendix 1, the forced low-temperature startup unit may perform the low-temperature startup control when the degradation value of the fuel cell with the least degradation is more than a predetermined distance from the average value of the degradation values ​​of the multiple fuel cells. This control device can reduce the frequency of low-temperature startup control even when the degree of variation is not required.

[0072] (Note 7) The fuel cell system (10) of this disclosure comprises a control device described in any one of appendices 1 to 6 and a plurality of fuel cells. This fuel cell system reduces the frequency of fuel cell replacement because the degradation of the fuel cells progresses evenly.

[0073] (Note 8) The fuel cell system described in Appendix 7 comprises an exhaust passage (22) for discharging exhaust gas from a plurality of fuel cells, a refrigerant passage (18) for circulating coolant to the plurality of fuel cells, and a heat pump (28) attached to the refrigerant passage and driven by the exhaust gas flowing through the exhaust passage to heat the coolant in the refrigerant passage, wherein the heat pump may be driven by the exhaust gas of the fuel cell performing the low-temperature start control to heat the coolant. This fuel cell system is excellent in terms of operational efficiency during startup because it can use the exhaust gas of the fuel cell performing the low-temperature start control to warm up other fuel cells.

[0074] (Note 9) The fuel cell system described in Appendix 7 may also include a warming device (29) for heating a plurality of fuel cells, and an auxiliary battery (38) for supplying power to the warming device. This fuel cell system can warm the fuel cells without putting a burden on them when the fuel cell temperature is low.

[0075] (Note 10) The fuel cell system described in Appendix 9 has a housing chamber (16a) for housing a plurality of fuel cells, and the warming device may be an air conditioner (30) that heats the housing chamber or a heater (32) attached to the fuel cell. This fuel cell system can efficiently heat the fuel cells.

[0076] (Note 11) The fuel cell system startup method of the present disclosure is a method for starting a fuel cell system comprising a plurality of fuel cells and a control device for controlling the fuel cells, wherein when the temperature of the plurality of fuel cells is below a predetermined level, a degradation determination unit of the control device determines the degradation value of the plurality of fuel cells, and a forced low-temperature startup unit of the control device performs low-temperature startup control to forcibly start the fuel cell with the least degradation to generate electricity. With this fuel cell system startup method, the degradation of the fuel cells progresses evenly, so the frequency of fuel cell replacement due to variations in fuel cell degradation alone can be suppressed.

[0077] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. [Explanation of Symbols]

[0078] 10…Fuel cell system 12…Fuel cell 12d...Auxiliary equipment 16a...Accommodation chamber 18...Refrigerant flow path 22...Exhaust passage 28... Heat pump 29... Warming device 30...Air conditioner 32...Heater 38...Auxiliary battery 44...Control unit 46...Deterioration determination section 48...Forced low temperature startup section 50…Heating control unit

Claims

1. A control device for controlling multiple fuel cells, A degradation determination unit that determines the degradation value of the multiple fuel cells when the temperature of the multiple fuel cells is below a predetermined level, A control device comprising: a forced low-temperature start unit that performs low-temperature start control to forcibly start the fuel cell with the least degradation and generate electricity.

2. A control device according to claim 1, The degradation determination unit determines the degree of variation in the degradation values ​​of the multiple fuel cells, The forced low-temperature startup unit is a control device that executes the low-temperature startup control when the determined degree of variation is greater than or equal to a predetermined value.

3. A control device according to claim 2, The degradation determination unit continues to determine the degree of variation even while the low-temperature startup control is being performed. The forced low-temperature startup unit is a control device that stops the low-temperature startup control when the degree of variation falls below a predetermined value.

4. A control device according to claim 2, The deterioration determination unit is a control device that determines the deterioration value of the fuel cell based on the cumulative operating time of the fuel cell, the number of times the fuel cell has been started, or the number of times the auxiliary components of the fuel cell have been used.

5. A control device according to claim 2, A control device having a heating control unit that heats the fuel cells that are not subjected to the low-temperature startup control when the temperatures of multiple fuel cells are below a predetermined level and the determined degree of variation is greater than or equal to a predetermined value.

6. A control device according to claim 1, The forced low-temperature startup unit is a control device that executes the low-temperature startup control when the degradation value of the fuel cell with the least degradation is more than a predetermined distance from the average value of the degradation values ​​of the multiple fuel cells.

7. A control device according to any one of claims 1 to 6, A fuel cell system comprising a plurality of the aforementioned fuel cells.

8. A fuel cell system according to claim 7, An exhaust passage for discharging exhaust gas from multiple fuel cells, A refrigerant flow path for circulating coolant to multiple fuel cells, The system includes a heat pump attached to the refrigerant flow path, which is driven by exhaust gas flowing through the exhaust passage to heat the coolant in the refrigerant flow path, The heat pump is driven by the exhaust gas of the fuel cell that performs the low-temperature startup control to heat the coolant in a fuel cell system.

9. A fuel cell system according to claim 7, A warming device for heating multiple fuel cells, A fuel cell system comprising an auxiliary battery that supplies power to the aforementioned warming device.

10. A fuel cell system according to claim 9, It has a housing chamber for housing a plurality of the fuel cells, The heating device is an air conditioner that heats the containment chamber or a heater attached to the fuel cell, in a fuel cell system.

11. A method for starting a fuel cell system comprising a plurality of fuel cells and a control device for controlling the fuel cells, When the temperature of the multiple fuel cells is below a predetermined level, the degradation determination unit of the control device determines the degradation value of the multiple fuel cells. A method for starting a fuel cell system, wherein the forced low-temperature startup unit of the control device performs low-temperature startup control to forcibly start the fuel cell with the least degradation and generate electricity.

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