Fuel cell system

Abstract

A fuel cell system (10) comprises: a plurality of fuel cell units (12); and a control device (14) capable of controlling the plurality of fuel cell units. When an air pump (50) of one fuel cell unit (12a) from among the plurality of fuel cell units is started and the rotation speed of the air pump reaches a predetermined set rotation speed during a startup process of the fuel cell system, the control device starts an air pump of another fuel cell unit (12b) from among the plurality of fuel cell units.

Description

Fuel cell system

[0001] The present disclosure relates to a fuel cell system.

[0002] In recent years, technical development on fuel cell systems that contribute to energy efficiency has been carried out to enable more people to secure access to affordable, reliable, sustainable and advanced energy.

[0003] A fuel cell system includes, for example, a plurality of fuel cell units. Each fuel cell unit includes a fuel cell having: a membrane-electrode assembly formed by disposing electrodes on both sides of an electrolyte membrane; an oxidant gas flow path for supplying oxidant gas to the electrolyte membrane; and a fuel gas flow path for supplying fuel gas to the electrolyte membrane. In each fuel cell unit, at least a part of the fuel gas discharged from the fuel cell is discharged to the outside in a state diluted with the oxidant gas discharged from an air pump.

[0004] Japanese Patent No. 7354981 discloses a fuel cell system including a plurality of fuel cell units. In this fuel cell system, when a predetermined waiting time has elapsed after starting the activation of one fuel cell unit, the activation of the other fuel cell unit is started. This suppresses the concentration of hydrogen gas discharged from the fuel cell system (exhaust fuel gas concentration) during the activation process of the fuel cell system.

[0005] There is a long-felt need for a better fuel cell system.

[0006] An object of the present disclosure is to solve the above-mentioned problem.

[0007] One aspect of the present disclosure is a fuel cell system comprising a plurality of fuel cell units and a control device capable of controlling the plurality of fuel cell units, wherein each of the plurality of fuel cell units comprises a fuel cell having a membrane electrode assembly formed by sandwiching an electrolyte membrane between a cathode electrode and an anode electrode, an oxidant gas flow path for supplying an oxidant gas to the electrolyte membrane, and a fuel gas flow path for supplying a fuel gas to the electrolyte membrane; an air pump; an oxidant gas supply path for supplying oxidant gas discharged from the air pump to the oxidant gas flow path of the fuel cell; and an oxidant gas discharge path for discharging the oxidant gas led from the oxidant gas flow path of the fuel cell, wherein at least a portion of the fuel gas discharged from the fuel cell is discharged to the outside in a diluted state by the oxidant gas discharged from the air pump, and the control device, in the startup process of the fuel cell system, starts the air pump of one of the plurality of fuel cell units, and when the rotational speed of the air pump reaches a predetermined set rotational speed, starts the air pump of the other of the plurality of fuel cell units.

[0008] Another aspect of the present invention is a fuel cell system comprising a plurality of fuel cell units and a control device capable of controlling the plurality of fuel cell units, wherein each of the plurality of fuel cell units comprises a fuel cell having a membrane electrode assembly formed by sandwiching an electrolyte membrane between a cathode electrode and an anode electrode, an oxidant gas flow path for supplying an oxidant gas to the electrolyte membrane, and a fuel gas flow path for supplying a fuel gas to the electrolyte membrane, an air pump, an oxidant gas supply path for supplying oxidant gas discharged from the air pump to the oxidant gas flow path of the fuel cell, and an oxidant gas discharge path for discharging the oxidant gas led from the oxidant gas flow path of the fuel cell, wherein at least a portion of the fuel gas discharged from the fuel cell is discharged to the outside in a diluted state by the oxidant gas discharged from the air pump, and the control device, in the startup process of the fuel cell system, starts the air pump of one of the plurality of fuel cell units, and when the rotation speed of the air pump reaches a predetermined set rotation speed, it permits the start of the air pump of the other of the plurality of fuel cell units.

[0009] According to the present invention, a better fuel cell system can be provided.

[0010] Figure 1 is a block diagram of the fuel cell system. Figure 2 is a schematic configuration diagram of the fuel cell unit. Figure 3 is a block diagram of the cooling device of the fuel cell system. Figure 4 is an explanatory diagram showing a part of the circuit configuration of the fuel cell system. Figure 5 is a block diagram of the control device of the fuel cell system. Figure 6 is a flowchart of the fuel cell unit startup process. Figure 7 is an explanatory diagram of the fuel cell system startup process.

[0011] In the aforementioned Japanese Patent Publication No. 7354981, one fuel cell unit is started, and then the other fuel cell unit is started after a predetermined waiting time has elapsed. In a fuel cell unit, the time from when the fuel cell unit is started until the fuel gas present in the oxidizer gas flow path of the fuel cell unit is discharged to the outside of the fuel cell system varies due to manufacturing variations and disturbances. Therefore, in such a fuel cell system, it is necessary to set a relatively long waiting time so that the exhaust fuel gas concentration does not change significantly due to manufacturing variations and disturbances. In this case, the time required for the fuel cell system startup process may become longer.

[0012] This disclosure provides a fuel cell system that can suppress the concentration of exhaust fuel gases during the startup process of a fuel cell system while keeping the time required for the startup process of the fuel cell system from becoming too long.

[0013] A fuel cell system 10 according to one embodiment of the present invention will be described below with reference to the drawings. Figure 1 is a block diagram of the fuel cell system 10. The fuel cell system 10 according to this embodiment is mounted on a mobile vehicle, for example. The fuel cell system 10 is not limited to the example of being mounted on a mobile vehicle, but may also be a stationary fuel cell system.

[0014] As shown in Figure 1, the fuel cell system 10 comprises a plurality of fuel cell units 12 and a control device 14. In this embodiment, the fuel cell system 10 comprises two fuel cell units 12, but it may also comprise three or more fuel cell units 12. Hereinafter, one of the plurality of fuel cell units 12 may be referred to as "one fuel cell unit 12a," and the other of the two fuel cell units 12 may be referred to as "the other fuel cell unit 12b."

[0015] The control device 14 controls a plurality of fuel cell units 12. The control device 14 comprises a plurality of fuel cell control units (FCECUs) 16 and a management control unit (MGECU) 18. Each of the plurality of fuel cell units 12 is provided with a fuel cell control unit 16. The fuel cell control unit 16 can control the fuel cell units 12.

[0016] The management control device 18 is a higher-level control device that controls multiple fuel cell control devices 16. The management control device 18 can receive information from each of the multiple fuel cell control devices 16. The management control device 18 can transmit information to each of the multiple fuel cell control devices 16. In other words, the multiple fuel cell control devices 16 can communicate with each other via the management control device 18.

[0017] Figure 2 is a schematic diagram of the fuel cell unit 12. As shown in Figure 2, the fuel cell unit 12 comprises a fuel cell 20, a cathode system device 22, and an anode system device 24. In this embodiment, the fuel cell 20 is a fuel cell stack in which a plurality of power generation cells 26 are stacked on top of each other. However, the fuel cell 20 may be formed by a single power generation cell 26.

[0018] The fuel cell 20 generates electricity through an electrochemical reaction between a fuel gas and an oxidizer gas. The fuel gas is, for example, hydrogen gas. The fuel gas is not particularly limited as long as it is a gas containing hydrogen. The oxidizer gas is, for example, air. The oxidizer gas is not limited to air as long as it is a gas containing oxygen. The power generation cell 26 has a membrane electrode assembly (MEA) 28 and a pair of separators 30a and 30b that sandwich the membrane electrode assembly 28.

[0019] The membrane electrode assembly 28 comprises an electrolyte membrane 32, a cathode electrode 34, and an anode electrode 36. The electrolyte membrane 32 is sandwiched between the cathode electrode 34 and the anode electrode 36. The electrolyte membrane 32 is, for example, a solid polymer electrolyte membrane. The solid polymer electrolyte membrane is, for example, a thin film of perfluorosulfonic acid containing water. Although detailed illustrations are omitted, each of the cathode electrode 34 and the anode electrode 36 includes an electrode catalyst layer bonded to the electrolyte membrane 32 and a gas diffusion layer laminated on the electrode catalyst layer.

[0020] One separator 30a has an oxidizer gas flow path 38 formed on the surface facing the membrane electrode assembly 28. The oxidizer gas flow path 38 communicates with the oxidizer gas inlet 40 and the oxidizer gas outlet 42 of the fuel cell 20. The other separator 30b has a fuel gas flow path 44 formed on the surface facing the membrane electrode assembly 28. The fuel gas flow path 44 communicates with the fuel gas inlet 46 and the fuel gas outlet 48 of the fuel cell 20. The fuel cell 20 may also be equipped with components other than those described above, but their description is omitted here.

[0021] The cathode system device 22 includes an air pump 50, an oxidizer gas supply passage 52, an oxidizer gas discharge passage 54, an inlet-side on-off valve 56, an outlet-side on-off valve 58, a bypass passage 59, and a bypass valve 61. The cathode system device 22 may also include components other than those listed above, but these will not be described here.

[0022] The air pump 50 discharges an oxidizing gas (air). As shown in Figure 5, the air pump 50 has a rotating shaft portion 50a and a fluid dynamic bearing 50b. The fluid dynamic bearing 50b is a hydrodynamic air bearing (air bearing) that uses pressurized air to rotatably support the rotating shaft portion 50a. The fluid dynamic bearing 50b utilizes fluid pressurized by the rotation of the rotating shaft portion 50a. When the rotational speed of the rotating shaft portion 50a of the air pump 50 exceeds the levitation speed, it levitates from the fluid dynamic bearing 50b. In this way, because the air pump 50 has a fluid dynamic bearing 50b, there is no need to separately provide a device to supply pressurized fluid to the air pump 50 to levitate the rotating shaft portion 50a. Therefore, the fuel cell unit 12 can be configured compactly.

[0023] The air pump 50 may have a fluid hydrostatic bearing (for example, a hydrostatic air bearing) instead of the fluid hydrostatic bearing 50b. Alternatively, the air pump 50 may have a rolling bearing instead of the fluid hydrostatic bearing 50b.

[0024] As shown in Figure 2, the oxidizer gas supply passage 52 supplies the oxidizer gas discharged from the air pump 50 to the oxidizer gas flow path 38 of the fuel cell 20. The oxidizer gas supply passage 52 connects the air pump 50 to the oxidizer gas inlet 40 of the fuel cell 20. The oxidizer gas discharge passage 54 discharges the oxidizer exhaust gas led from the oxidizer gas flow path 38 of the fuel cell 20 to the outside of the fuel cell system 10.

[0025] The inlet valve 56 is a sealing valve (solenoid valve) provided in the oxidizer gas supply passage 52. The inlet valve 56 opens and closes the oxidizer gas supply passage 52. The outlet valve 58 is a sealing valve (solenoid valve) provided in the oxidizer gas discharge passage 54. The outlet valve 58 opens and closes the oxidizer gas discharge passage 54. Each of the inlet valve 56 and the outlet valve 58 may be configured to allow adjustment of the opening degree. Examples of the inlet valve 56 and the outlet valve 58 include, but are not limited to, butterfly valves.

[0026] The bypass passage 59 connects the upstream side of the inlet valve 56 in the oxidizer gas supply passage 52 to the downstream side of the outlet valve 58 in the oxidizer gas discharge passage 54. The bypass valve 61 opens and closes the bypass passage 59.

[0027] The anode system 24 includes a fuel gas supply unit 60, a fuel gas supply passage 62, a fuel gas discharge passage 64, a gas-liquid separator 66, a circulation passage 68, a drain passage 70, and a drain valve 72. The anode system 24 may also include other components, but these will not be described here.

[0028] The fuel gas supply unit 60 supplies fuel gas to the fuel gas supply passage 62. The fuel gas supply unit 60 includes injectors and ejectors (not shown). The fuel gas supply passage 62 connects the fuel gas supply unit 60 to the fuel gas inlet 46 of the fuel cell 20. The fuel gas supply passage 62 supplies fuel gas to the fuel gas flow path 44 of the fuel cell 20.

[0029] Fuel exhaust gas discharged from the fuel gas passage 44 of the fuel cell 20 flows through the fuel gas discharge passage 64. The fuel exhaust gas contains water generated by the power generation of the fuel cell 20. A gas-liquid separator 66 is provided in the fuel gas discharge passage 64. The gas-liquid separator 66 separates the fuel exhaust gas into gas and liquid. The gas-liquid separator 66 can store the liquid water separated from the fuel exhaust gas. The circulation passage 68 guides the fuel exhaust gas that has flowed through the gas-liquid separator 66 to an ejector (not shown) of the fuel gas supply unit 60. The fuel exhaust gas flowing through the circulation passage 68 is reused as fuel gas by flowing into the fuel gas supply passage 62 via the ejector.

[0030] The drain passage 70 connects the gas-liquid separator 66 and the oxidizer gas discharge passage 54. The drain passage 70 guides the liquid water stored in the gas-liquid separator 66, along with the fuel exhaust gas, to the oxidizer gas discharge passage 54. The fuel exhaust gas flowing through the drain passage 70 is diluted by the oxidizer exhaust gas flowing through the oxidizer gas discharge passage 54 and then discharged to the outside of the fuel cell system 10. A drain valve 72 is provided in the drain passage 70. The drain valve 72 opens and closes the drain passage 70.

[0031] Figure 3 is a block diagram illustrating the cooling device 74 of the fuel cell system 10. As shown in Figure 3, the fuel cell system 10 further comprises a cooling device 74. The cooling device 74 circulates a cooling medium to each fuel cell unit 12. Examples of cooling mediums include pure water, ethylene glycol, and oil. The cooling device 74 has a cooling channel 76, a plurality of cooling pumps 78, and a tank 80. The cooling device 74 may also be equipped with components other than those listed above, but their description is omitted here.

[0032] A cooling medium for cooling the fuel cell 20 flows through the cooling passage 76. A cooling pump 78 circulates the cooling medium through the cooling passage 76. The cooling medium is stored in the tank 80. Multiple cooling pumps 78 are provided in each fuel cell unit 12. The multiple cooling pumps 78 are arranged in parallel with each other. The cooling passage 76 includes a first cooling passage 82, a branch passage 84, a second cooling passage 86, a merging passage 88, and a third cooling passage 90.

[0033] The first cooling channel 82 is connected to the tank 80. The cooling medium stored in the tank 80 is guided into the first cooling channel 82. The branching channel 84 connects the first cooling channel 82 to the multiple cooling pumps 78. The second cooling channel 86 connects each of the multiple cooling pumps 78 to each of the multiple fuel cells 20. That is, the second cooling channel 86 is provided in each fuel cell unit 12. The confluence channel 88 connects the multiple fuel cells 20 to the third cooling channel 90. The third cooling channel 90 returns the cooling medium to the tank 80. That is, the cooling channels 76 are in communication with each other downstream of the multiple cooling pumps 78 (confluence channel 88).

[0034] In such a cooling system 74, when multiple cooling pumps 78 are started, the cooling medium stored in the tank 80 flows through the first cooling channel 82, the branching channel 84, the multiple cooling pumps 78, the multiple second cooling channels 86, the multiple fuel cells 20, the converging channel 88, and the third cooling channel 90.

[0035] Figure 4 is an explanatory diagram showing a part of the circuit configuration of the fuel cell system 10. As shown in Figure 4, the fuel cell system 10 further comprises a power supply system 92. The power supply system 92 includes a first battery 94, a plurality of DC / DC converters 96, a plurality of second batteries 98, and a plurality of relay boxes 100. The power supply system 92 may also include components other than those listed above, but these will not be described here.

[0036] The output voltage of the first battery 94 is higher than the output voltage of the second battery 98. The output voltage of the second battery 98 is, for example, 12V. The first battery 94 may be charged by power supplied from another high-voltage battery (not shown). Alternatively, the first battery 94 may be charged by power generated by the fuel cells 20 of a plurality of fuel cell units 12.

[0037] The DC / DC converter 96 is provided between each of the multiple fuel cell units 12 and the first battery 94. The DC / DC converter 96 can step down the voltage supplied from the first battery 94.

[0038] The second battery 98 and relay box 100 may be provided in each of the multiple fuel cell units 12. The second battery 98 can be charged by power supplied from the first battery 94 via the DC / DC converter 96. The second battery 98 can supply power to the fuel cell control device 16, the inlet valve 56, the outlet valve 58, the drain valve 72, and the fuel gas supply unit 60 via the relay box 100. In addition, the second battery 98 of one of the fuel cell units 12a can supply power to the management control device 18. Power is supplied to the air pump 50 from a high-voltage battery (not shown).

[0039] Figure 5 is a block diagram illustrating the control device 14 of the fuel cell system 10. As shown in Figure 5, the fuel cell system 10 includes a rotation speed sensor 102 for detecting the rotation speed of the air pump 50. The rotation speed sensor 102 is provided in each of the multiple fuel cell units 12. The detection signal from the rotation speed sensor 102 is transmitted to the fuel cell control device 16.

[0040] The fuel cell control device 16 comprises a calculation unit 104 and a storage unit 106. The calculation unit 104 is composed of a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). In other words, the calculation unit 104 is composed of processing circuitry.

[0041] The calculation unit 104 includes an air pump control unit 108, a cooling pump control unit 110, a valve control unit 112, a determination unit 114, and a fuel gas control unit 116. The air pump control unit 108, the cooling pump control unit 110, the valve control unit 112, the determination unit 114, and the fuel gas control unit 116 can be realized by the calculation unit 104 executing a program stored in the storage unit 106.

[0042] Furthermore, at least a portion of the air pump control unit 108, the cooling pump control unit 110, the valve control unit 112, the determination unit 114, and the fuel gas control unit 116 may be implemented using integrated circuits such as ASICs (Application Specific Integrated Circuits) and FPGAs (Field-Programmable Gate Arrays). Alternatively, at least a portion of the air pump control unit 108, the cooling pump control unit 110, the valve control unit 112, the determination unit 114, and the fuel gas control unit 116 may be configured using electronic circuits including discrete devices.

[0043] The air pump control unit 108 controls the air pump 50 to drive and stop it. The cooling pump control unit 110 controls the cooling pump 78 to drive and stop it. The valve control unit 112 controls the inlet valve 56, the outlet valve 58, and the drain valve 72. The determination unit 114 determines whether the rotational speed of the air pump 50 has reached a predetermined set rotational speed. The fuel gas control unit 116 controls the fuel gas supply unit 60 to control the supply and stop of fuel gas.

[0044] The storage unit 106 is constituted by a volatile memory (not shown) and a non-volatile memory (not shown). Examples of the volatile memory include RAM (Random Access Memory). The volatile memory is used as a working memory for a processor, and temporarily stores data and the like required for processing or arithmetic operations. Examples of the non-volatile memory include ROM (Read Only Memory), flash memory, and the like. The non-volatile memory is used as a storage memory, and stores programs, tables, maps, and the like. At least part of the storage unit 106 may be provided in the processor, integrated circuit, or the like described above.

[0045] Next, an example of a method for starting up the fuel cell system 10 will be described. Note that when the fuel cell system 10 is stopped, nitrogen gas remains in the oxidant gas flow path 38 in each fuel cell unit 12. Furthermore, while the fuel cell system 10 is stopped, a trace amount of the fuel gas remaining in the fuel gas flow path 44 permeates through the membrane electrode assembly 28 into the oxidant gas flow path 38 in each fuel cell unit 12. In the fuel cell system 10, for example, a startup process is started when a startup switch (ignition switch, not shown) is turned on.

[0046] First, the startup process (startup sequence) performed by each fuel cell unit 12 will be described. FIG. 6 is a flowchart showing the startup process for the fuel cell unit 12. As shown in FIG. 6, in step S1, the fuel cell control device 16 performs device connection processing. Specifically, the fuel cell control device 16 controls the relay box 100 to electrically connect the second battery 98 and the plurality of devices. The plurality of devices include an inlet-side opening / closing valve 56, an outlet-side opening / closing valve 58, a drain valve 72, and a fuel gas supply unit 60. After this, the process transitions to step S2.

[0047] In step S2, the valve control unit 112 performs valve opening control processing. Specifically, after the management control device 18 activates the DC / DC converter 96 to bring it into a state where a plurality of devices can be reliably driven, the fuel cell control device 16 opens the inlet-side on-off valve 56 and the outlet-side on-off valve 58, and brings the drain valve 72 into a closed state. After this, the process proceeds to step S3.

[0048] In step S3, the air pump control unit 108 performs activation processing of the air pump 50. That is, the air pump control unit 108 permits activation of the air pump 50. Thereafter, the valve control unit 112 opens the bypass valve 61 and closes the inlet-side on-off valve 56 and the outlet-side on-off valve 58. Accordingly, the oxidant gas discharged from the air pump 50 is discharged to the oxidant gas discharge path 54 via the bypass flow path 59. That is, in step S3, the oxidant gas discharged from the air pump 50 is not supplied to the fuel cell 20.

[0049] Further, in step S4, the cooling pump control unit 110 performs activation processing of the cooling pump 78 in a state where the inlet-side on-off valve 56 is closed. That is, the cooling pump control unit 110 permits activation of the cooling pump 78 before the oxidant gas is supplied to the fuel cell 20. Accordingly, the cooling medium flows through the fuel cell 20. Note that although the process of step S4 is incorporated in the startup sequence of one fuel cell unit 12a, it is not incorporated in the startup sequence of the other fuel cell unit 12b. The management control device 18 can control the cooling pump 78 of the other fuel cell unit 12b. That is, the activation of the cooling pump 78 of the other fuel cell unit 12b is performed by the management control device 18 separately from the activation sequence of the other fuel cell unit 12b. After step S3 and step S4, the process proceeds to step S5. Further, in step S4, the cooling pump control unit 110 only needs to activate the cooling pump 78 before the oxidant gas is supplied to the fuel cell 20, and may activate the cooling pump 78 before activating the air pump 50.

[0050] In step S5, the determination unit 114 determines whether the rotational speed of the air pump 50 has reached the levitation rotational speed. The levitation rotational speed is the minimum rotational speed at which the rotating shaft portion 50a of the air pump 50 levitates relative to the fluid dynamic pressure bearing 50b. The levitation rotational speed is predetermined and stored in the storage unit 106. If the determination unit 114 determines that the rotational speed of the air pump 50 has not reached the levitation rotational speed (NO in step S5), step S5 is repeated. If the determination unit 114 determines that the rotational speed of the air pump 50 has reached the levitation rotational speed (YES in step S5), the process proceeds to step S6.

[0051] In step S6, the fuel gas control unit 116 performs the fuel gas supply start process. Specifically, the fuel gas control unit 116 controls the fuel gas supply unit 60 to supply fuel gas to the fuel gas flow path 44. After this, the process proceeds to step S7.

[0052] In step S7, the process of starting the supply of oxidant gas to the fuel cell 20 is performed. Specifically, the valve control unit 112 closes the bypass valve 61 and opens the inlet valve 56 and the outlet valve 58. As a result, the oxidant gas discharged from the air pump 50 flows through the oxidant gas supply passage 52 and the oxidant gas flow path 38 to the oxidant gas discharge passage 54. The fuel cell 20 starts generating electricity through an electrochemical reaction between the oxidant gas in the oxidant gas flow path 38 and the fuel gas in the fuel gas flow path 44. After this, the process proceeds to step S8.

[0053] In step S8, the determination unit 114 performs a startup completion determination process. Specifically, the determination unit 114 determines that the startup of the fuel cell 20 is complete when the output voltage of the fuel cell 20 exceeds a preset voltage threshold. The voltage threshold is predetermined and stored in the storage unit 106. After this, the process shown in Figure 6 is completed.

[0054] In this embodiment, after starting the air pump 50, the bypass valve 61 is opened and the inlet valve 56 and outlet valve 58 are closed. Subsequently, fuel gas is supplied from the fuel gas supply unit 60 to the fuel cell 20 to suppress deterioration of the membrane electrode assembly 28 (cathode electrode 34). After supplying fuel gas to the fuel cell 20, the inlet valve 56 and outlet valve 58 are opened. This suppresses deterioration of the membrane electrode assembly 28 during the startup process of the fuel cell system 10 and allows the fuel gas to be discharged to the outside of the fuel cell system 10 while appropriately diluting hydrogen.

[0055] Next, regarding the startup process of the fuel cell system 10, we will explain in particular the timing of the startup process performed by the multiple fuel cell units 12. Figure 7 is an explanatory diagram of the startup process of the fuel cell system 10. As shown in Figure 7, in the startup process of the fuel cell system 10, the startup process (startup sequence) described above is basically performed sequentially in each fuel cell unit 12.

[0056] Specifically, for one fuel cell unit 12a, the device connection process is performed at time t1. After this, at time t2, the valve opening control process is performed. After this, at time t3, the start-up process for the air pump 50 and the start-up process for the cooling pump 78 are performed. As described above, the start timing of the start-up process for the air pump 50 may be simultaneous with the start-up process for the cooling pump 78, or it may be before or after the start timing of the start-up process for the cooling pump 78. During the start-up process for the air pump 50, the oxidizer gas discharged from the air pump 50 is discharged to the oxidizer gas discharge passage 54 via the bypass passage 59, and therefore does not flow into the oxidizer gas passage 38 of the fuel cell 20. After this, at time t4, the fuel gas supply start process is performed. After this, at time t5, the supply start process for the oxidizer gas to the fuel cell 20 is started.

[0057] Next, in one of the fuel cell units 12a, the fluid in the oxidizer gas flow path 38 (nitrogen gas and a small amount of fuel gas) is replaced with oxidizer gas. Also in the other fuel cell unit 12a, the fluid in the fuel gas flow path 44 is replaced with fuel gas. After this, a startup completion determination process is performed in the other fuel cell unit 12a.

[0058] For the other fuel cell unit 12b, the device connection process is performed at time t1. After that, the valve opening control process is performed at time t2. After that, the cooling pump 78 is started at time t3. In this embodiment, the device connection process, the valve opening control process, and the cooling pump 78 start process may be performed simultaneously in multiple fuel cell units 12.

[0059] When starting the cooling pumps 78 in multiple fuel cell units 12, the management control device 18 transmits a start command for the cooling pumps 78 to the fuel cell control device 16 of one of the fuel cell units 12a. Upon receiving the start command for the cooling pumps 78, the fuel cell control device 16 of one of the fuel cell units 12a transmits a start command to the cooling pumps 78. As a result, the cooling pumps 78 of one of the fuel cell units 12a are started. The fuel cell control device 16 of one of the fuel cell units 12a transmits the start status of the cooling pumps 78 to the management control device 18.

[0060] The management control device 18 transmits a start signal to the cooling pump 78 of the other fuel cell unit 12b. This starts the cooling pump 78 of the other fuel cell unit 12b. In other words, the management control device 18 directly transmits a start instruction to the cooling pump 78 of the other fuel cell unit 12b without going through the fuel cell control device 16 of the other fuel cell unit 12b. This makes it possible to synchronize the start timing of the cooling pump 78 of the other fuel cell unit 12b with the start timing of the cooling pump 78 of the one fuel cell unit 12a, even if the start sequence of the other fuel cell unit 12b does not include the start processing of the cooling pump 78. Alternatively, the management control device 18 may receive a completion signal for the valve opening control processing in the fuel cell 20 of the one fuel cell unit 12a. In this case, based on the receipt of the completion signal, the management control device 18 can simultaneously perform the start processing of the cooling pump 78 of the one fuel cell unit 12a and the start processing of the cooling pump 78 of the other fuel cell unit 12b.

[0061] However, if the cooling pump 78 of one fuel cell unit 12a starts up before the cooling pump 78 of the other fuel cell unit 12b, the cooling medium discharged from the cooling pump 78 of one fuel cell unit 12a may flow back into the other fuel cell unit 12b via the confluence channel 88. However, in this embodiment, since multiple cooling pumps 78 are started simultaneously, such backflow of the cooling medium can be suppressed. In addition, since each fuel cell unit 12 has a cooling pump 78, drying of the fuel cell 20 in each fuel cell unit 12 can be prevented and it can be cooled appropriately.

[0062] In this embodiment, at time t3, the air pump 50 of one fuel cell unit 12a is started. Then, at time t4, the air pump 50 start-up process is completed, and the fuel gas supply start process begins. In the air pump 50 start-up process, it is determined that the air pump 50 start-up process is complete when the rotational speed of the air pump 50 reaches the levitation rotational speed. Then, at time t5, the inlet valve 56 and the outlet valve 58 are opened, and the supply process of oxidizer gas to the fuel cell 20 begins. On the other hand, in the other fuel cell unit 12b, the air pump 50 start-up process has not yet been performed even at time t5. That is, from time t1 to time t5, the fuel cell control device 16 of the other fuel cell unit 12b prohibits the driving of the air pump 50.

[0063] When the fuel gas supply initiation process is performed in one fuel cell unit 12a, the fuel gas from that fuel cell unit 12a begins to be discharged to the outside of the fuel cell system 10. Specifically, in one fuel cell unit 12a, the fuel gas begins to be discharged to the outside of the fuel cell system 10 in a state diluted with oxidizer gas. Therefore, the concentration of fuel gas discharged from one fuel cell unit 12a gradually increases from time t6. Also, at this point, the fuel gas supply initiation process has not yet been performed in the other fuel cell unit 12b, so no fuel gas is discharged from the other fuel cell unit 12b. Thus, the concentration of discharged fuel gas can be suppressed during the startup process of the fuel cell system 10.

[0064] Furthermore, at time t3 or t4 or later, the determination unit 114 of one of the fuel cell units 12a determines whether the rotational speed of the air pump 50 has reached a preset rotational speed. If the determination unit 114 determines that the rotational speed of the air pump 50 has not reached the preset rotational speed, this process is repeated. If the determination unit 114 determines that the rotational speed of the air pump 50 has reached the preset rotational speed, the other fuel cell unit 12b performs the start-up process for the air pump 50 (see time t7).

[0065] In this embodiment, the set rotation speed is the rotation speed at which the power consumption of the air pump 50 is maximized. In this case, it is possible to avoid multiple air pumps 50 rotating at maximum power consumption at the same time, thereby suppressing the maximum power consumption (peak value of power consumption) of the fuel cell system 10. Note that the set rotation speed does not have to be the rotation speed at which the power consumption of the air pump 50 is maximized.

[0066] The fuel cell control device 16 of one fuel cell unit 12a and the fuel cell control device 16 of the other fuel cell unit 12b can communicate with each other via the management control device 18. Therefore, information that the rotational speed of the air pump 50 of one fuel cell unit 12a has reached a set rotational speed can be transmitted to the fuel cell control device 16 of the other fuel cell unit 12b via the management control device 18. This allows the air pump 50 of the other fuel cell unit 12b to be started at the optimal timing.

[0067] The air pump 50 of the other fuel cell unit 12b is started when a predetermined waiting time Δt has elapsed since the air pump 50 of the other fuel cell unit 12a was started. Alternatively, the air pump 50 of the other fuel cell unit 12b may be started based on the elapsed time since the air pump 50 of the other fuel cell unit 12a was started.

[0068] After the air pump 50 of the other fuel cell unit 12b is started, the fuel gas supply is initiated, and then the inlet valve 56 and outlet valve 58 are opened, initiating the supply of oxidizer gas to the fuel cell 20. When the fuel gas supply is initiated in the other fuel cell unit 12b, the fuel gas from the other fuel cell unit 12b begins to be discharged to the outside of the fuel cell system 10. Specifically, in the other fuel cell unit 12b, the fuel gas begins to be discharged to the outside of the fuel cell system 10 in a state diluted by the oxidizer gas. Therefore, the concentration of fuel gas discharged from the other fuel cell unit 12b gradually increases from time t8. In this case, during the startup process of the fuel cell system 10, the peak value of the fuel gas concentration discharged from one fuel cell unit 12a and the peak value of the fuel gas concentration discharged from the other fuel cell unit 12b are out of sync. This makes it possible to suppress the exhaust fuel gas concentration during the startup process of the fuel cell system 10.

[0069] In the other fuel cell unit 12b, after the fuel gas supply start process is performed, the fluid in the oxidizer gas flow path 38 is replaced with oxidizer gas, the fluid in the fuel gas flow path 44 is replaced with fuel gas, and the startup completion determination process is performed.

[0070] According to this embodiment, when the air pump 50 of one fuel cell unit 12a is started and its rotational speed reaches a set rotational speed, the air pump 50 of the other fuel cell unit 12b is started. This makes it possible to suppress the exhaust fuel gas concentration during the startup process of the fuel cell system 10. Furthermore, even if the time from the start of the air pump 50 of one fuel cell unit 12a to the air pump 50 reaching a set rotational speed changes due to manufacturing variations or disturbances, the waiting time Δt of the air pump 50 can be kept to a minimum. Therefore, it is possible to suppress the time required for the startup process of the fuel cell system 10 from becoming long.

[0071] This embodiment is not limited to the configuration described above. In the fuel cell system 10, there may be multiple other fuel cell units 12b. In this case, the control device 14 may sequentially start the air pumps 50 of the multiple other fuel cell units 12b. This makes it possible to suppress the exhaust fuel gas concentration during the startup process of the fuel cell system 10, even when there are multiple other fuel cell units 12b.

[0072] Furthermore, when sequentially starting the air pumps 50 of multiple other fuel cell units 12b, the next air pump 50 may be started in each of the multiple other fuel cell units 12b when the rotational speed of the air pump 50 that has been started reaches a set rotational speed. This makes it possible to further reduce the exhaust fuel gas concentration during the startup process of the fuel cell system 10, even when multiple other fuel cell units 12b are provided.

[0073] In a fuel cell system 10, if multiple other fuel cell units 12b are provided, the air pumps 50 of the multiple other fuel cell units 12b may be started simultaneously when the rotational speed of the air pump 50 of one fuel cell unit 12a reaches a set rotational speed. Even in such a case, the timing of fuel gas discharge from one fuel cell unit 12a and the timing of fuel gas discharge from the multiple other fuel cell units 12b can be staggered. Therefore, the exhaust fuel gas concentration can be suppressed during the startup process of the fuel cell system 10. In addition, because the air pumps 50 of the multiple other fuel cell units 12b are started simultaneously, the time required for the startup process of the fuel cell system 10 can be further reduced.

[0074] In addition to the disclosures mentioned above, the following further notes are made:

[0075] (Note 1) The fuel cell system (10) of the present disclosure is a fuel cell system comprising a plurality of fuel cell units (12) and a control device (14) capable of controlling the plurality of fuel cell units, wherein each of the plurality of fuel cell units is a fuel cell (20) having a membrane electrode assembly (28) formed by sandwiching an electrolyte membrane (32) between a cathode electrode (34) and an anode electrode (36), an oxidant gas flow path (38) for supplying oxidant gas to the electrolyte membrane, and a fuel gas flow path (44) for supplying fuel gas to the electrolyte membrane, an air pump (50), and a device that supplies the oxidant gas discharged from the air pump to the oxidant gas flow path of the fuel cell. The fuel cell system includes an oxidizer gas supply passage (52) and an oxidizer gas discharge passage (54) for discharging the oxidizer gas introduced from the oxidizer gas flow path of the fuel cell, wherein at least a portion of the fuel gas discharged from the fuel cell is discharged to the outside in a diluted state by the oxidizer gas discharged from the air pump, and the control device, in the startup process of the fuel cell system, starts the air pump of one of the fuel cell units (12a) of the plurality of fuel cell units, and when the rotation speed of the air pump reaches a predetermined set rotation speed, starts the air pump of the other fuel cell unit (12b) of the plurality of fuel cell units.

[0076] With this configuration, the air pump of one fuel cell unit is started, and when its rotational speed reaches a set speed, the air pump of the other fuel cell unit is started. This allows for minimizing the waiting time of the air pumps while suppressing the exhaust fuel gas concentration, even if the time it takes for one fuel cell unit's air pump to reach the set speed varies due to manufacturing variations or disturbances. Therefore, the time required for the fuel cell system startup process can be reduced. Consequently, a better fuel cell system can be provided.

[0077] (Note 2) The fuel cell system described in Note 1, wherein the control device includes a plurality of fuel cell control devices (16) provided in each of the plurality of fuel cell units, and a management control device (18) capable of communicating with the plurality of fuel cell control devices, each of the plurality of fuel cell control devices controls the air pump of the fuel cell unit in which the fuel cell control device is provided, and the plurality of fuel cell control devices may communicate with each other via the management control device.

[0078] With this configuration, information that the rotational speed of the air pump in one fuel cell unit has reached a set rotational speed can be transmitted to the fuel cell control unit of the other fuel cell unit via the management control unit. This allows the air pump of the other fuel cell unit to be started at the optimal timing.

[0079] (Note 3) In the fuel cell system described in Note 1 or 2, the air pump may have a rotating shaft portion (50a) and a fluid dynamic bearing (50b) that rotatably supports the rotating shaft portion.

[0080] With this configuration, since the air pump has a fluid dynamic bearing, there is no need to provide a separate device for supplying pressurized fluid to the air pump to levitate the rotating shaft. Therefore, the fuel cell unit can be made compact.

[0081] (Note 4) The fuel cell system described in Note 3, wherein each of the plurality of fuel cell units has a fuel gas supply passage (62) for supplying fuel gas to the fuel gas passage of the fuel cell, and the control device may start supplying fuel gas from the fuel gas supply passage to the fuel gas passage of the fuel cell after the rotating shaft portion has been levitated by the fluid dynamic bearing.

[0082] With this configuration, the fuel gas discharged from the fuel cell can be diluted with an oxidizer gas discharged from an air pump.

[0083] (Note 5) The fuel cell system described in Note 4, wherein the set rotational speed may be greater than the minimum rotational speed of the rotating shaft at which the rotating shaft floats.

[0084] With this configuration, the concentration of exhaust fuel gas can be further reduced during the startup process of the fuel cell system.

[0085] (Note 6) A fuel cell system according to any one of Notes 1 to 5, wherein each of the plurality of fuel cell units may include a cooling channel (76) through which a cooling medium for cooling the fuel cell flows, and a cooling pump (78) for circulating the cooling medium through the cooling channel.

[0086] With this configuration, each fuel cell unit has a cooling pump, allowing for efficient cooling of the fuel cell in each unit.

[0087] (Note 7) The fuel cell system described in Note 6, wherein the plurality of cooling channels are in communication with each other downstream of the plurality of cooling pumps, and the control device may start the plurality of cooling pumps simultaneously.

[0088] With this configuration, for example, by activating only the cooling pump of one fuel cell unit, it is possible to suppress the backflow of the cooling medium discharged from that cooling pump to the other fuel cell unit.

[0089] (Note 8) A fuel cell system as described in Note 4 or 5, wherein each of the plurality of fuel cell units comprises an inlet-side shut-off valve (56) for opening and closing the oxidizer gas supply passage, an outlet-side shut-off valve (58) for opening and closing the oxidizer gas discharge passage, a bypass passage (59) connecting the upstream side of the oxidizer gas supply passage beyond the inlet-side shut-off valve and the downstream side of the oxidizer gas discharge passage beyond the outlet-side shut-off valve, and a bypass valve (61) for opening and closing the bypass passage, wherein the control device may start supplying fuel gas to the fuel gas passage while controlling the inlet-side shut-off valve and the outlet-side shut-off valve to close the oxidizer gas supply passage and the oxidizer gas discharge passage, and controlling the bypass valve to open the bypass passage.

[0090] With this configuration, the oxidizer gas discharged from the air pump can be prevented from flowing into the fuel gas, while the fuel gas emitted from the fuel cell can be diluted with the oxidizer gas. This makes it possible to suppress the degradation of the fuel cell while reducing the concentration of the emitted fuel gas.

[0091] (Note 9) A fuel cell system according to any one of Notes 1 to 8, wherein the other fuel cell unit is provided in multiple quantities, and the control device may sequentially start the air pumps of the multiple other fuel cell units.

[0092] With this configuration, even if multiple fuel cell units are provided, the exhaust fuel gas concentration can be suppressed during the startup process of the fuel cell system.

[0093] (Note 10) In the fuel cell system described in Note 9, the control device may start the air pump of the next fuel cell unit when the rotational speed of the air pump that has been started in the other fuel cell unit reaches the set rotational speed.

[0094] With this configuration, even when multiple fuel cell units are provided, the concentration of exhaust fuel gases can be further reduced during the startup process of the fuel cell system.

[0095] (Note 11) The fuel cell system of the present disclosure is a fuel cell system comprising a plurality of fuel cell units and a control device capable of controlling the plurality of fuel cell units, each of the plurality of fuel cell units comprising: a fuel cell having a membrane electrode assembly formed by sandwiching an electrolyte membrane between a cathode electrode and an anode electrode; an oxidant gas flow path for supplying an oxidant gas to the electrolyte membrane; a fuel cell having an oxidant gas flow path for supplying a fuel gas to the electrolyte membrane; an air pump; an oxidant gas supply path for supplying an oxidant gas discharged from the air pump to the oxidant gas flow path of the fuel cell; and an oxidant gas discharge path for discharging an oxidant gas led from the oxidant gas flow path of the fuel cell, wherein at least a portion of the fuel gas discharged from the fuel cell is discharged to the outside in a diluted state by the oxidant gas discharged from the air pump, and the control device, in the startup process of the fuel cell system, starts the air pump of one of the plurality of fuel cell units, and when the rotation speed of the air pump reaches a predetermined set rotation speed, it permits the start of the air pump of the other of the plurality of fuel cell units.

[0096] (Note 12) A fuel cell system as described in any one of Notes 1 to 11, wherein the set rotation speed is the rotation speed that results in the maximum power consumption of the air pump from the start to the completion of the startup process of the fuel cell system.

[0097] This configuration prevents multiple air pumps from rotating at their maximum power consumption at the same time, thereby reducing the maximum power consumption (peak power consumption) of the fuel cell system.

[0098] This configuration produces the same effect as described in Appendix 1.

[0099] 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.

[0100] 10...Fuel cell system 12, 12a, 12b...Fuel cell unit 14...Control device 16...Fuel cell control device 18...Management control device 20...Fuel cell 28...Membrane electrode assembly 32...Electrolyte membrane 34...Cathode electrode 36...Anode electrode 38...Oxidizer gas flow path 44...Fuel gas flow path 50...Air pump 50a...Rotating shaft 50b...Fluid dynamic bearing 52...Oxidizer gas supply path 54...Oxidizer gas discharge path 56...Inlet valve 58...Outlet valve 62...Fuel gas supply path 76...Cooling path 78...Cooling pump

Claims

1. A fuel cell system (10) comprising a plurality of fuel cell units (12) and a control device (14) capable of controlling the plurality of fuel cell units, wherein each of the plurality of fuel cell units comprises: a fuel cell (20) having a membrane electrode assembly (28) formed by sandwiching an electrolyte membrane (32) between a cathode electrode (34) and an anode electrode (36), an oxidant gas flow path (38) for supplying oxidant gas to the electrolyte membrane, and a fuel gas flow path (44) for supplying fuel gas to the electrolyte membrane; an air pump (50); an oxidant gas supply path (52) for supplying oxidant gas discharged from the air pump to the oxidant gas flow path of the fuel cell; and an oxidant gas discharge path (54) for discharging oxidant gas led from the oxidant gas flow path of the fuel cell, wherein at least a portion of the fuel gas discharged from the fuel cell is discharged to the outside in a diluted state by the oxidant gas discharged from the air pump. The control device, in the startup process of the fuel cell system, starts the air pump of one of the fuel cell units (12a) and when the rotation speed of the air pump reaches a predetermined set rotation speed, starts the air pump of the other fuel cell unit (12b) among the multiple fuel cell units.

2. A fuel cell system according to claim 1, wherein the control device includes a plurality of fuel cell control devices (16) provided in each of the plurality of fuel cell units, and a management control device (18) capable of communicating with the plurality of fuel cell control devices, each of the plurality of fuel cell control devices controls the air pump of the fuel cell unit to which the fuel cell control device is provided, and the plurality of fuel cell control devices can communicate with each other via the management control device.

3. A fuel cell system according to claim 1, wherein the air pump comprises a rotating shaft portion (50a) and a fluid dynamic bearing (50b) that rotatably supports the rotating shaft portion.

4. A fuel cell system according to claim 3, wherein each of the plurality of fuel cell units has a fuel gas supply passage (62) for supplying fuel gas to the fuel gas passage of the fuel cell, and the control device starts supplying fuel gas from the fuel gas supply passage to the fuel gas passage of the fuel cell after the rotating shaft portion has been levitated by the fluid dynamic bearing.

5. A fuel cell system according to claim 4, wherein the set rotational speed is greater than the minimum rotational speed of the rotating shaft at which the rotating shaft levitates.

6. A fuel cell system according to claim 1, wherein each of the plurality of fuel cell units comprises a cooling channel (76) through which a cooling medium for cooling the fuel cell flows, and a cooling pump (78) for circulating the cooling medium through the cooling channel.

7. A fuel cell system according to claim 6, wherein the plurality of cooling channels are in communication with each other downstream of the plurality of cooling pumps, and the control device starts the plurality of cooling pumps simultaneously.

8. A fuel cell system according to claim 4, wherein each of the plurality of fuel cell units comprises: an inlet-side shut-off valve (56) for opening and closing the oxidizer gas supply passage; an outlet-side shut-off valve (58) for opening and closing the oxidizer gas discharge passage; a bypass passage (59) connecting the upstream side of the oxidizer gas supply passage beyond the inlet-side shut-off valve and the downstream side of the oxidizer gas discharge passage beyond the outlet-side shut-off valve; and a bypass valve (61) for opening and closing the bypass passage, wherein the control device controls the inlet-side shut-off valve and the outlet-side shut-off valve to close the oxidizer gas supply passage and the oxidizer gas discharge passage, and controls the bypass valve to open the bypass passage, and starts supplying fuel gas to the fuel gas passage.

9. A fuel cell system according to claim 1, wherein a plurality of the other fuel cell units are provided, and the control device sequentially activates the air pumps of the plurality of the other fuel cell units.

10. A fuel cell system according to claim 9, wherein the control device starts the air pump of the next fuel cell unit when the rotational speed of the air pump that has been started in the other fuel cell unit reaches the set rotational speed.

11. A fuel cell system comprising a plurality of fuel cell units and a control device capable of controlling the plurality of fuel cell units, wherein each of the plurality of fuel cell units comprises: a fuel cell having a membrane electrode assembly formed by sandwiching an electrolyte membrane between a cathode electrode and an anode electrode, an oxidant gas flow path for supplying an oxidant gas to the electrolyte membrane, and a fuel gas flow path for supplying fuel gas to the electrolyte membrane; an air pump; an oxidant gas supply path for supplying oxidant gas discharged from the air pump to the oxidant gas flow path of the fuel cell; and an oxidant gas discharge path for discharging oxidant gas led from the oxidant gas flow path of the fuel cell, wherein at least a portion of the fuel gas discharged from the fuel cell is discharged to the outside in a diluted state by the oxidant gas discharged from the air pump; and the control device, in the startup process of the fuel cell system, starts the air pump of one of the plurality of fuel cell units, and when the rotational speed of the air pump reaches a predetermined set rotational speed, it permits the start of the air pump of the other of the plurality of fuel cell units.

12. A fuel cell system according to any one of claims 1 to 11, wherein the set rotational speed is the rotational speed at which the air pump consumes the maximum power from the start to the completion of the startup process of the fuel cell system.

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