Fuel cell system, control device, control method for fuel cell system, and program

Abstract

To provide a better fuel cell system, a control device, a control method for the fuel cell system, and a program.SOLUTION: A fuel cell system 10 includes a fuel cell stack 12, a reaction exhaust gas flow path 84, a first device 86, a second device 88, a first heater 92, a second heater 94, and a heater control unit 118 that can individually control the first heater and the second heater. When the first heater and the second heater are driven at the time of starting the fuel cell system, the heater control unit drives the second heater for a driving time shorter than the driving time of the first heater.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fuel cell system, a control device, a control method for a fuel cell system, and a program. [Background technology]

[0002] In recent years, research and development into fuel cell systems that contribute to energy efficiency has been conducted in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] For example, Patent Document 1 discloses a fuel cell system equipped with a first heater for heating a hydrogen pressure regulating valve provided in a hydrogen supply path and a second heater for heating an air pressure regulating valve provided in an air supply path. The first heater heats the hydrogen pressure regulating valve when the hydrogen pressure regulating valve is not operating due to freezing. The second heater heats the oxygen pressure regulating valve when the air pressure regulating valve is not operating due to freezing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-268179 A Summary of the Invention [Problem to be solved by the invention]

[0005] There is a need for improved fuel cell systems, control devices, control methods and programs for fuel cell systems.

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

[0007] A first aspect of the present invention is a fuel cell system comprising: a fuel cell which generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas; a reaction exhaust gas flow path connected to the fuel cell and through which a reaction exhaust gas which is a fuel exhaust gas or an oxidant exhaust gas discharged from the fuel cell flows; a first device provided in the reaction exhaust gas flow path and in which liquid water may remain when the operation of the fuel cell is stopped; a second device provided in the reaction exhaust gas flow path and in which the liquid water is not expected to remain when the operation of the fuel cell is stopped and through which water vapor flows when the fuel cell system is started; a first heater which heats the first device; a second heater which heats the second device; and a heater control unit which can individually control the first heater and the second heater, wherein when the first heater and the second heater are driven when the fuel cell system is started, the heater control unit drives the second heater for a driving time shorter than the driving time of the first heater.

[0008] A second aspect of the present invention is a control device for the above-mentioned fuel cell system, the control device having the heater control unit.

[0009] A third aspect of the present invention is a control method for a fuel cell system including a fuel cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas, a reaction exhaust gas flow path connected to the fuel cell and through which a reaction exhaust gas that is a fuel exhaust gas or an oxidant exhaust gas discharged from the fuel cell flows, a first device provided in the reaction exhaust gas flow path and in which liquid water may remain when the operation of the fuel cell is stopped, a second device provided in the reaction exhaust gas flow path and in which the liquid water is not expected to remain in the operation of the fuel cell when the operation of the fuel cell is stopped and through which water vapor flows when the fuel cell system is started, a first heater that heats the first device, a second heater that heats the second device, and a heater control unit that can individually control the first heater and the second heater, wherein when the heater control unit drives the first heater and the second heater when starting up the fuel cell system, the heater control unit drives the second heater for a driving time shorter than the driving time of the first heater.

[0010] A fourth aspect of the present invention is a program for causing a computer to execute the above-mentioned fuel cell system control method. Effect of the Invention

[0011] According to the present invention, it is possible to provide a better fuel cell system, a control device, a control method for a fuel cell system, and a program. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a fuel cell system according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram for explaining a power system of a first heater and a power system of a second heater. [Diagram 3] FIG. 3 is a flowchart for explaining a control method for the fuel cell system. [Figure 4] FIG. 4 is a graph showing the temperature change of the first device and the temperature change of the fuel cell system. [Diagram 5] FIG. 5 is a graph showing the temperature change of the first device and the temperature change of the fuel cell system. [Figure 6] FIG. 6 is a graph showing the relationship between the driving time of the heater device and the power consumption. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A fuel cell system 10, a control device 18, a control method for the fuel cell system 10, and a program according to one embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a schematic diagram showing the configuration of a fuel cell system 10 according to this embodiment. The fuel cell system 10 is mounted on a fuel cell vehicle (not shown), such as a fuel cell electric vehicle. Note that the fuel cell system 10 may also be mounted on equipment other than a vehicle.

[0014] As shown in FIG. 1, a fuel cell system 10 according to this embodiment includes a fuel cell stack (fuel cell) 12, a cathode system device 14, an anode system device 16, and a control device 18.

[0015] The fuel cell stack 12 generates power through an electrochemical reaction between a fuel gas and an oxidant 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 oxidant gas is, for example, air. The oxidant gas is not limited to air as long as it is a gas containing oxygen. The fuel cell stack 12 is formed by stacking a plurality of power generation cells 20. Each power generation cell 20 has a membrane electrode assembly (MEA) 22 and a pair of separators 24a, 24b that sandwich the membrane electrode assembly 22.

[0016] The membrane electrode assembly 22 includes an electrolyte membrane 26, a cathode electrode 28, and an anode electrode 30. The electrolyte membrane 26 is sandwiched between the cathode electrode 28 and the anode electrode 30. The electrolyte membrane 26 is, for example, a solid polymer electrolyte membrane. The solid polymer electrolyte membrane is, for example, a thin film of perfluorosulfonic acid containing moisture. Although not shown in detail, each of the cathode electrode 28 and the anode electrode 30 includes an electrode catalyst layer bonded to the electrolyte membrane 26 and a gas diffusion layer laminated on the electrode catalyst layer.

[0017] One of the separators, 24a, has an oxidant gas flow path 32 formed on its surface facing the membrane electrode assembly 22. The oxidant gas flow path 32 communicates with an oxidant gas inlet port 34 and an oxidant gas outlet port 36 of the fuel cell stack 12. The other separator, 24b, has a fuel gas flow path 38 formed on its surface facing the membrane electrode assembly 22. The fuel gas flow path 38 communicates with a fuel gas inlet port 40 and a fuel gas outlet port 42 of the fuel cell stack 12. The fuel cell stack 12 may also have components other than those described above, but descriptions of these will be omitted here.

[0018] The cathode system 14 has an oxidant gas supply unit 44, an oxidant gas supply passage 46, a supply stop valve 48, an oxidant gas discharge passage 50, a discharge stop valve 52, a humidifier 54, a first gas-liquid separator 56, a first drain passage 58, and a first drain valve 60. The cathode system 14 may also be provided with components other than these components, but the description thereof will be omitted here.

[0019] The oxidant gas supply unit 44 supplies the oxidant gas to the fuel cell stack 12 via an oxidant gas supply passage 46. Examples of the oxidant gas supply unit 44 include an air pump or an air compressor. The oxidant gas supply passage 46 is connected to the oxidant gas inlet portion 34 of the fuel cell stack 12. The supply stop valve 48 is provided in the oxidant gas supply passage 46. The supply stop valve 48 opens and closes the oxidant gas supply passage 46.

[0020] The oxidant gas discharge flow path 50 is connected to the oxidant gas outlet portion 36 of the fuel cell stack 12. The oxidant gas discharge flow path 50 passes through the oxidant gas exhaust gas discharged from the fuel cell stack 12. The oxidant exhaust gas contains water generated by the power generation of the fuel cell stack 12. The oxidant gas discharge flow path 50 discharges the oxidant exhaust gas to the outside of the fuel cell system 10. The discharge seal valve 52 is provided in the oxidant gas discharge flow path 50. The discharge seal valve 52 opens and closes the oxidant gas discharge flow path 50.

[0021] The humidifier 54 humidifies the oxidant gas flowing through the oxidant gas supply flow passage 46 with the oxidant exhaust gas flowing through the oxidant gas discharge flow passage 50. The oxidant gas guided to the humidifier 54 from the oxidant gas supply unit 44 via the supply seal valve 48 is humidified by the humidifier 54 and then supplied to the first gas-liquid separator 56. The first gas-liquid separator 56 separates the oxidant gas humidified by the humidifier 54 into gas and liquid. The oxidant exhaust gas discharged from the oxidant gas outlet 36 is guided to the discharge seal valve 52 via the humidifier 54.

[0022] The first drain flow path 58 communicates with the oxidant gas flow path 32 of the fuel cell stack 12. The first drain flow path 58 is connected to a portion of the oxidant gas discharge flow path 50 that is located downstream of the discharge stop valve 52. The first drain flow path 58 is a flow path for guiding liquid water in the oxidant gas flow path 32 of the fuel cell stack 12 to the oxidant gas discharge flow path 50 when the fuel cell stack 12 is in an inclined state. Here, a case where the fuel cell stack 12 is in an inclined state refers to a case where the fuel cell stack 12 provided in the fuel cell vehicle is inclined, for example, because the fuel cell vehicle is stopped on a slope or the like.

[0023] When the fuel cell stack 12 is inclined, the liquid water in the oxidizing gas flow path 32 of the fuel cell stack 12 may not be discharged to the oxidizing gas discharge flow path 50. Even in such a case, the liquid water in the oxidizing gas flow path 32 of the fuel cell stack 12 can be smoothly discharged to the oxidizing gas discharge flow path 50 via the first drain flow path 58. When the fuel cell stack 12 is in a horizontal state, the liquid water in the oxidizing gas flow path 32 of the fuel cell stack 12 does not flow through the first drain flow path 58, and only the oxidizing exhaust gas containing water vapor flows through the first drain flow path 58. The first drain valve 60 is provided in the first drain flow path 58. The first drain valve 60 is an opening / closing valve that opens and closes the first drain flow path 58.

[0024] The anode system device 16 has a fuel gas supply unit 62, a fuel gas supply flow path 64, a fuel gas discharge flow path 66, a second gas-liquid separator 68, a circulation flow path 70, a second drain flow path 72, a second drain valve 74, a third drain flow path 76, a third drain valve 78, a bleed flow path 80, and a bleed valve 82. The anode system device 16 may also be provided with components other than these components, but the description thereof will be omitted here.

[0025] The fuel gas supply unit 62 supplies fuel gas to the fuel cell stack 12 via a fuel gas supply passage 64. The fuel gas supply unit 62 includes an injector, an ejector, etc. (not shown). The fuel gas supply passage 64 is connected to the fuel gas inlet portion 40 of the fuel cell stack 12.

[0026] The fuel exhaust gas discharged from the fuel cell stack 12 flows through the fuel gas discharge flow path 66. The fuel exhaust gas contains product water generated by the power generation of the fuel cell stack 12. The second gas-liquid separator 68 is provided in the fuel gas discharge flow path 66. The second gas-liquid separator 68 separates the fuel exhaust gas into gas and liquid. The second gas-liquid separator 68 can store liquid water separated from the fuel exhaust gas. The circulation flow path 70 guides the fuel exhaust gas that has flowed through the second gas-liquid separator 68 to an ejector (not shown) of the fuel gas supply unit 62. The fuel exhaust gas flowing through the circulation flow path 70 is reused as fuel gas by flowing into the fuel gas supply flow path 64 via the ejector.

[0027] The second drain flow path 72 connects the second gas-liquid separator 68 and the oxidant gas discharge flow path 50. The second drain flow path 72 guides the liquid water stored in the second gas-liquid separator 68 to the oxidant gas discharge flow path 50 together with the fuel exhaust gas. The fuel exhaust gas flowing through the second drain flow path 72 is diluted by the oxidant exhaust gas flowing through the oxidant gas discharge flow path 50 and discharged to the outside of the fuel cell system 10. The second drain valve 74 is provided in the second drain flow path 72. The second drain valve 74 is disposed directly below the second gas-liquid separator 68. The second drain valve 74 opens and closes the second drain flow path 72.

[0028] The third drain flow path 76 communicates with the fuel gas flow path 38 of the fuel cell stack 12. The third drain flow path 76 is connected to a portion of the second drain flow path 72 that is located downstream of the second drain valve 74. The third drain flow path 76 is a flow path for guiding liquid water in the fuel gas flow path 38 of the fuel cell stack 12 to the fuel gas discharge flow path 66 when the fuel cell stack 12 is in an inclined state.

[0029] When the fuel cell stack 12 is in an inclined state, the liquid water in the fuel gas flow path 38 of the fuel cell stack 12 may not be discharged to the fuel gas discharge flow path 66. Even in such a case, the liquid water in the fuel gas flow path 38 of the fuel cell stack 12 can be smoothly discharged to the oxidant gas discharge flow path 50 via the third drain flow path 76 and the second drain flow path 72. When the fuel cell stack 12 is in a horizontal state, the liquid water in the fuel gas flow path 38 of the fuel cell stack 12 does not flow through the third drain flow path 76, and only the fuel exhaust gas containing water vapor flows through the third drain flow path 76. The third drain valve 78 is provided in the third drain flow path 76. The third drain valve 78 is an opening / closing valve that opens and closes the third drain flow path 76.

[0030] The bleed flow path 80 connects the circulation flow path 70 and the first gas-liquid separator 56. The bleed flow path 80 guides the fuel exhaust gas that has flowed through the second gas-liquid separator 68 to the first gas-liquid separator 56. The fuel exhaust gas flowing through the bleed flow path 80 is separated into gas and liquid in the first gas-liquid separator 56. That is, the first gas-liquid separator 56 separates the oxidant gas and the fuel exhaust gas into gas and liquid. The first gas-liquid separator 56 can store liquid water separated from the oxidant gas and the fuel exhaust gas. The liquid water stored in the first gas-liquid separator 56 can be discharged to the oxidant gas discharge flow path 50, for example, via a flow path not shown.

[0031] The fuel exhaust gas and the oxidant gas introduced from the bleed flow passage 80 are mixed in the first gas-liquid separator 56. The mixed gas obtained by mixing the oxidant gas and the fuel exhaust gas is introduced to the oxidant gas flow passage 32 of the fuel cell stack 12. In the fuel cell stack 12, the fuel exhaust gas and the oxidant gas in the mixed gas exothermically react with each other in the electrode catalyst layer of the cathode electrode 28 to generate water. This allows the fuel cell stack 12 to be efficiently warmed up when the fuel cell system 10 is started in a low temperature (for example, below freezing point) environment, for example. In addition, since the fuel exhaust gas can be consumed in the fuel cell stack 12, the total amount of fuel exhaust gas discharged from the fuel cell system 10 to the outside can be reduced. The bleed valve 82 is provided in the bleed flow passage 80. The bleed valve 82 is an opening / closing valve that opens and closes the bleed flow passage 80.

[0032] The fuel cell system 10 includes a cooling system (not shown) that circulates a cooling medium through the fuel cell stack 12. Examples of the cooling medium include pure water, ethylene glycol, and oil.

[0033] In this embodiment, the fuel exhaust gas or the oxidant exhaust gas may be referred to as a reaction exhaust gas. Also, a flow path connected to the fuel cell stack 12 and through which the reaction exhaust gas flows may be referred to as a reaction exhaust gas flow path 84. The reaction exhaust gas flow path 84 includes an oxidant gas discharge flow path 50, a first drain flow path 58, a fuel gas discharge flow path 66, a circulation flow path 70, a second drain flow path 72, a third drain flow path 76, and a bleed flow path 80.

[0034] The reaction exhaust gas flow path 84 is provided with a first device 86 and a second device 88. The first device 86 and the second device 88 are disposed, for example, relatively far away from the fuel cell stack 12. That is, the first device 86 and the second device 88 are less susceptible to heat generated from the fuel cell stack 12 when the fuel cell system 10 is started up.

[0035] The first device 86 is a device in which liquid water may remain when the fuel cell stack 12 is in an operation stopped state in which the operation of the fuel cell stack 12 is stopped. The first device 86 includes, for example, a second gas-liquid separator 68 and a second drain valve 74. The second gas-liquid separator 68 can store liquid water separated from the fuel exhaust gas, so liquid water is likely to remain in the second gas-liquid separator 68 when the operation of the fuel cell stack 12 is in an operation stopped state. In addition, the second drain valve 74 is located directly below the second gas-liquid separator 68, so liquid water that has flowed downward from the second gas-liquid separator 68 is likely to remain in the second drain valve 74. The liquid water remaining in the first device 86 may freeze in a low temperature environment (for example, an environment below the freezing point).

[0036] The second device 88 is a device in which liquid water is not expected to remain when the fuel cell stack 12 is out of operation, and through which water vapor flows when the fuel cell system 10 is started. The second device 88 includes, for example, a first drain valve 60, a third drain valve 78, and a bleed valve 82. Oxidant exhaust gas containing water vapor flows through the first drain valve 60. Fuel exhaust gas containing water vapor flows through the third drain valve 78 and the bleed valve 82. Water vapor flowing through the second device 88 may freeze in a low temperature environment (for example, an environment below the freezing point).

[0037] When the fuel cell stack 12 is in a horizontal position, liquid water in the oxidant gas flow path 32 of the fuel cell stack 12 does not flow through the first drain valve 60. Also, when the fuel cell stack 12 is in a horizontal position, liquid water in the fuel gas flow path 38 of the fuel cell stack 12 does not flow through the third drain valve 78. Therefore, in this embodiment, the first drain valve 60 and the third drain valve 78 are included in the second device 88.

[0038] The first device 86 and the second device 88 are not limited to the above-mentioned configuration. When the fuel cell stack 12 is in a tilted state, liquid water may flow through the first drain valve 60 and the third drain valve 78. Therefore, the first drain valve 60 and the third drain valve 78 may be included in the first device 86, not in the second device 88. The first device 86 may include the first gas-liquid separator 56. Furthermore, the second device 88 may include the exhaust seal valve 52.

[0039] The fuel cell system 10 further includes a heater device 90. The heater device 90 includes a first heater 92 that heats the first device 86 and a second heater 94 that heats the second device 88. As shown in Fig. 1, the first heater 92 heats the second gas-liquid separator 68 and the second drain valve 74. The second heater 94 heats the first drain valve 60, the third drain valve 78, and the bleed valve 82.

[0040] FIG. 2 is a schematic diagram for explaining the power system of the first heater 92 and the power system of the second heater 94. As shown in FIG. 2, the first heater 92 and the second heater 94 are supplied with power from one battery 96. The voltage of the battery 96 is, for example, 12 V. The first heaters 92 are electrically connected to the battery 96 via a first wiring 98. The first wiring 98 is provided with a first switch 100 for turning the first wiring 98 on and off. The second heaters 94 are electrically connected to the battery 96 via a second wiring 102. The second wiring 102 is provided with a second switch 104 for turning the second wiring 102 on and off.

[0041] As shown in FIG. 1, a first temperature sensor 106 and a second temperature sensor 108 are connected to the control device 18. The first temperature sensor 106 sequentially measures a temperature corresponding to the temperature of the first device 86. Specifically, the first temperature sensor 106 sequentially measures the temperature of a housing (not shown) of the fuel cell system 10, for example. The second temperature sensor 108 sequentially measures a temperature corresponding to the temperature of the fuel cell stack 12. Specifically, the second temperature sensor 108 sequentially measures the temperature of a cooling medium circulating inside the fuel cell stack 12, for example.

[0042] The control device 18 includes a calculation unit 110 and a storage unit 112. The calculation unit 110 is configured by a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). That is, the calculation unit 110 is configured by a processing circuitry.

[0043] The calculation unit 110 has a control unit 114, a temperature acquisition unit 116, a heater control unit 118, a freezing determination unit 120, and a thawing determination unit 122. The control unit 114, the temperature acquisition unit 116, the heater control unit 118, the freezing determination unit 120, and the thawing determination unit 122 can be realized by the calculation unit 110 executing a program stored in the memory unit 112.

[0044] At least a part of the control unit 114, the temperature acquisition unit 116, the heater control unit 118, the freezing determination unit 120, and the thawing determination unit 122 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). Also, at least a part of the control unit 114, the temperature acquisition unit 116, the heater control unit 118, the freezing determination unit 120, and the thawing determination unit 122 may be configured by an electronic circuit including a discrete device.

[0045] The storage unit 112 is composed of a volatile memory (not shown) and a non-volatile memory (not shown). An example of the volatile memory is a random access memory (RAM). The volatile memory is used as a working memory of the processor, and temporarily stores data and the like required for processing or calculation. An example of the non-volatile memory is a read only memory (ROM) or a flash memory. The non-volatile memory is used as a storage memory, and stores programs, tables, maps, and the like. At least a part of the storage unit 112 may be provided in the processor, integrated circuit, and the like described above.

[0046] The control unit 114 is responsible for the overall control of the fuel cell system 10. The temperature acquisition unit 116 can grasp the temperature of the first device 86 based on a signal supplied from the first temperature sensor 106. The first temperature sensor 106 sequentially outputs a signal corresponding to the temperature of the first device 86 to the control device 18. The temperature acquisition unit 116 can grasp the temperature of the fuel cell stack 12 based on a signal supplied from the second temperature sensor 108. The second temperature sensor 108 sequentially outputs a signal corresponding to the temperature of the fuel cell stack 12 to the control device 18.

[0047] The heater control unit 118 individually controls the first heater 92 and the second heater 94. The heater control unit 118 controls the first switch 100 to start and stop driving the first heater 92. The heater control unit 118 controls the second switch 104 to start and stop driving the second heater 94.

[0048] The freezing determination unit 120 determines whether or not the liquid water remaining in the first device 86 is frozen. The freezing determination unit 120 determines whether or not the water vapor flowing through the reactive exhaust gas flow path 84 is expected to freeze in the second device 88. The thawing determination unit 122 determines whether or not the frozen material in the first device 86 has thawed.

[0049] FIG. 3 is a flowchart for explaining a control method for the fuel cell system 10. As shown in FIG.

[0050] In step S1, the control unit 114 stops the operation of the fuel cell system 10. Specifically, for example, when a user turns off a power switch (not shown), the control unit 114 stops the operation of the fuel cell system 10. Generally, a certain amount of time elapses between step S1 and step S2 (described later), but this is not limited to the above.

[0051] In step S2, the control unit 114 starts up the fuel cell system 10. Specifically, for example, when the user turns on the power switch, the control unit 114 starts up the fuel cell system 10. When the fuel cell system 10 starts up, fuel gas is supplied from the fuel gas supply unit 62 to the fuel gas flow path 38 of the fuel cell stack 12 via the fuel gas supply flow path 64. In addition, oxidant gas is supplied from the oxidant gas supply unit 44 to the oxidant gas flow path 32 of the fuel cell stack 12 via the oxidant gas supply flow path 46. The fuel cell stack 12 generates power by an electrochemical reaction between the fuel gas and the oxidant gas. After step S2, the process proceeds to step S3.

[0052] In step S3, the freezing determination unit 120 determines whether or not the liquid water remaining in the first device 86 is frozen. The freezing determination unit 120 determines that the liquid water remaining in the first device 86 is frozen when the temperature of the first device 86 is below the freezing point. The freezing determination unit 120 determines that the liquid water remaining in the first device 86 is not frozen when the temperature of the first device 86 is higher than the freezing point. The temperature of the first device 86 is acquired by the temperature acquisition unit 116.

[0053] 3 is completed when the freezing determination unit 120 determines that the liquid water remaining in the first device 86 is not frozen (NO in step S3). That is, the fuel cell system 10 is started without driving the first heater 92 and the second heater 94. When the freezing determination unit 120 determines that the liquid water remaining in the first device 86 is frozen (YES in step S3), the process proceeds to step S4.

[0054] In step S4, the heater control unit 118 starts driving the first heater 92. As a result, the first device 86 is heated by the first heater 92. After that, the process proceeds to step S5.

[0055] When the fuel cell stack 12 generates power, water is generated inside the fuel cell stack 12. The generated water flows as water vapor together with the reaction exhaust gas into the reaction exhaust gas flow path 84. Then, the water vapor flowing into the reaction exhaust gas flow path 84 may freeze in the second device 88.

[0056] Therefore, in this embodiment, in step S5, the freezing determination unit 120 determines whether or not water vapor is expected to freeze in the second device 88. Specifically, when the temperature of the fuel cell stack 12 is higher than the freezing point, the freezing determination unit 120 determines that water vapor is not expected to freeze in the second device 88. When the temperature of the fuel cell stack 12 is equal to or lower than the freezing point, the freezing determination unit 120 determines that water vapor is expected to freeze in the second device 88.

[0057] If the freezing determination unit 120 determines that the water vapor is not expected to freeze in the second device 88 (NO in step S5), the process proceeds to step S10. If the freezing determination unit 120 determines that the water vapor is expected to freeze in the second device 88 (YES in step S5), the process proceeds to step S6.

[0058] When the fuel cell stack 12 starts generating power, the electrolyte membrane 26 absorbs the water generated in the fuel cell stack 12. While the electrolyte membrane 26 is absorbing the water, the amount of water vapor contained in the reaction exhaust gas is negligibly small. Therefore, the possibility that the water vapor contained in the reaction exhaust gas freezes in the second device 88 is low. When the amount of water absorbed by the electrolyte membrane 26 reaches the upper limit of the amount of water that the electrolyte membrane 26 can absorb, the electrolyte membrane 26 can no longer absorb the water. Therefore, the amount of water vapor contained in the reaction exhaust gas increases. Therefore, the possibility that the water vapor in the reaction exhaust gas freezes in the second device 88 increases.

[0059] In step S6, the freezing determination unit 120 determines whether or not water vapor is in a state where it can flow through the second device 88. Specifically, the freezing determination unit 120 determines that water vapor is in a state where it can flow through the second device 88 when the time that has elapsed since the start of power generation of the fuel cell stack 12 reaches a predetermined water vapor flow start time. The freezing determination unit 120 determines that water vapor is not in a state where it can flow through the second device 88 when the time that has elapsed since the start of power generation of the fuel cell stack 12 has not reached the predetermined water vapor flow start time.

[0060] The water vapor flow start time can be set, for example, to the time from when power generation of the fuel cell stack 12 starts until the amount of generated water absorbed by the electrolyte membrane 26 reaches an upper limit of the amount of generated water that can be absorbed by the electrolyte membrane 26. Note that the freezing determination unit 120 may determine whether or not water vapor can flow through the second device 88 based on, for example, an output signal of a water vapor sensor provided in the second device 88.

[0061] If the freeze determination unit 120 determines that the state is not such that water vapor can circulate through the second device 88 (NO in step S6), step S6 is repeated. If the freeze determination unit 120 determines that the state is such that water vapor can circulate through the second device 88 (YES in step S6), the process proceeds to step S7.

[0062] In step S7, the heater control unit 118 starts driving the second heater 94. As a result, the second device 88 is heated by the second heater 94. After that, the process proceeds to step S8.

[0063] In step S8, the freezing determination unit 120 determines whether or not water vapor is no longer expected to freeze in the second device 88. Specifically, when the temperature of the fuel cell stack 12 is higher than a predetermined temperature, the freezing determination unit 120 determines that water vapor is no longer expected to freeze in the second device 88. When the temperature of the fuel cell stack 12 is equal to or lower than a predetermined temperature, the freezing determination unit 120 determines that water vapor is expected to freeze in the second device 88.

[0064] The predetermined temperature can be set appropriately, for example, to the freezing point (0° C.). The predetermined temperature may also be set to a temperature higher than the freezing point, for example, about 20° C. The freeze determination unit 120 may also determine whether or not water vapor is no longer expected to freeze in the second device 88, based on the elapsed time since the fuel cell stack 12 has begun to start up.

[0065] When the freezing determination unit 120 determines that the water vapor is expected to freeze in the second device 88 (NO in step S8), step S8 is repeated. When the freezing determination unit 120 determines that the water vapor is no longer expected to freeze in the second device 88 (YES in step S8), the process proceeds to step S9.

[0066] In step S9, the heater control unit 118 stops driving the second heater 94. After that, the process proceeds to step S10.

[0067] In step S10, the thawing determination unit 122 determines whether the frozen object in the first device 86 has thawed. Specifically, the thawing determination unit 122 determines that the frozen object in the first device 86 has thawed when the temperature of the first device 86 is higher than the freezing point. The thawing determination unit 122 determines that the frozen object in the first device 86 has not thawed when the temperature of the first device 86 is equal to or lower than the freezing point.

[0068] The thawing determination unit 122 may determine that the frozen object in the first device 86 has thawed when the time that has elapsed since the start of driving the first heater 92 reaches a predetermined thawing time. In this case, the thawing determination unit 122 determines that the frozen object in the first device 86 has not thawed when the time that has elapsed since the start of driving the first heater 92 is shorter than the predetermined thawing time. The thawing time may be set to a time required to thaw the frozen object in the first device 86 when the maximum amount of liquid water remains and freezes in the first device 86, for example.

[0069] If the thawing determination unit 122 determines that the frozen item in the first device 86 has not thawed (NO in step S10), step S10 is repeated. If the thawing determination unit 122 determines that the frozen item in the first device 86 has thawed (YES in step S10), the process proceeds to step S11.

[0070] In step S11, the heater control unit 118 stops driving the first heater 92. In this way, the process shown in FIG.

[0071] 4 is a graph showing the temperature change of the first device 86 and the fuel cell system 10 in a sub-freezing environment. Line segment L1 in FIG. 4 shows the temperature change of the first device 86, and line segment L2 shows the temperature change of the fuel cell stack 12.

[0072] As shown in FIG. 4, for example, when the control unit 114 stops the operation of the fuel cell system 10 at time t1, the temperature of the first device 86 and the temperature of the fuel cell stack 12 decrease. The heat capacity of the first device 86 is smaller than the heat capacity of the fuel cell stack 12. Therefore, the temperature of the first device 86 decreases at a rate greater than the rate at which the temperature of the fuel cell stack 12 decreases. The temperature of the first device 86 reaches the freezing point (0° C.) at time t2. When the temperature of the first device 86 falls below the freezing point, the liquid water remaining in the first device 86 freezes. Note that, at time t2, the temperature of the fuel cell stack 12 is higher than the freezing point. Thereafter, the temperature of the fuel cell stack 12 reaches the freezing point at time t3.

[0073] If the timing to start up the fuel cell system 10 is before time t2, the temperature of the first device 86 is higher than the freezing point, so the heater control unit 118 does not drive the first heater 92 and the second heater 94.

[0074] If the fuel cell system 10 is started after time t2 and before time t3, the temperature of the first device 86 will be below the freezing point, causing the liquid water remaining in the first device 86 to freeze. In this case, the temperature of the fuel cell stack 12 is higher than the freezing point, and therefore the temperature of the reaction exhaust gas discharged from the fuel cell stack 12 is also higher than the freezing point. In this case, even if the temperature of the second device 88 is below the freezing point, the water vapor contained in the reaction exhaust gas is unlikely to freeze in the second device 88.

[0075] Therefore, when the timing to start the fuel cell system 10 is after time t2 and before time t3, the heater control unit 118 drives only the first heater 92 and does not drive the second heater 94. This makes it possible to reduce the power consumption of the heater device 90 compared to when both the first heater 92 and the second heater 94 are driven. Therefore, the power of the battery 96 can be supplied to devices other than the first heater 92 and the second heater 94.

[0076] If the fuel cell system 10 is started after time t3, the temperatures of the fuel cell stack 12 and the first device 86 will both be below the freezing point. Control of the fuel cell system 10 in this case will be described with reference to Figures 5 and 6.

[0077] Fig. 5 is a graph showing the temperature change of the fuel cell stack 12 and the temperature change of the first device 86. Line segment L3 in Fig. 5 shows the temperature change of the first device 86, and line segment L4 shows the temperature change of the fuel cell stack 12. Fig. 6 is a graph showing the relationship between the drive time and the power consumption of the first heater 92 and the second heater 94. In Fig. 6, P1 is the power consumption per unit time of the first heater 92, P2 is the power consumption per unit time of the second heater 94, P3 is the sum of the power consumption P1 and the power consumption P2, and P4 is the maximum power that can be supplied per unit time of the battery 96.

[0078] 5 and 6, at time t4, the fuel cell system 10 is started and the first heater 92 starts to be driven. At time t4, the second heater 94 has not yet started to be driven.

[0079] 5, when the fuel cell stack 12 starts generating power following the start-up of the fuel cell system 10, the fuel cell stack 12 generates heat. As a result, the temperature of the fuel cell stack 12 increases at a rate greater than the rate of increase in the temperature of the first device 86.

[0080] Furthermore, when the fuel cell stack 12 starts generating power, the electrolyte membrane 26 absorbs water generated in the fuel cell stack 12. Thereafter, at time t5, the amount of water absorbed by the electrolyte membrane 26 reaches the upper limit of the amount of water that the electrolyte membrane 26 can absorb. Therefore, at time t5, the amount of water vapor contained in the reaction exhaust gas increases. In other words, at time t5, the possibility that the water vapor contained in the reaction exhaust gas freezes in the second device 88 increases. Note that, between time t4 and time t5, the amount of water vapor contained in the reaction exhaust gas is negligibly small.

[0081] 5 and 6, the second heater 94 starts to be driven at time t5. This makes it possible to prevent the water vapor contained in the reaction exhaust gas from freezing in the second device 88.

[0082] Thereafter, as shown in Fig. 5, at time t6, the temperature of the fuel cell stack 12 exceeds the freezing point. At this time t6, the driving of the second heater 94 is stopped. In this case, as shown in Fig. 6, the driving time of the second heater 94 is the period from time t5 to time t6. In other words, the heater control unit 118 starts driving the first heater 92, and then starts driving the second heater 94.

[0083] At time t6, the temperature of the reaction exhaust gas discharged from the fuel cell stack 12 becomes relatively high. Therefore, the possibility that the water vapor contained in the reaction exhaust gas freezes in the second device 88 becomes low. The driving of the second heater 94 may be stopped when the temperature of the fuel cell stack 12 reaches a predetermined temperature (e.g., 20°C) higher than the freezing point. In this case, since the temperature of the reaction exhaust gas is sufficiently high, the water vapor contained in the reaction exhaust gas can be further prevented from freezing in the second device 88.

[0084] Thereafter, as shown in Fig. 5, at time t7, the temperature of the first device 86 exceeds the freezing point. At this time t7, the driving of the first heater 92 is stopped. In this case, as shown in Fig. 6, the driving time of the first heater 92 is the period from time t4 to time t7. In other words, the heater control unit 118 stops driving the first heater 92 after stopping the driving of the second heater 94.

[0085] In this way, the power consumption per unit time of the heater device 90 from time t4 to time t5 is the power consumption P1 of the first heater 92. The power consumption P1 of the first heater 92 is smaller than the maximum power supplyable power P4 of the battery 96. The power consumption P3 of the heater device 90 from time t5 to time t6 is the sum of the power consumption P1 of the first heater 92 and the power consumption P2 of the second heater 94. The power consumption P2 of the second heater 94 is smaller than the power consumption P1 of the first heater 92. The power consumption P3 of the heater device 90 is smaller than the maximum power supplyable power P4 of the battery 96. The power consumption per unit time of the heater device 90 from time t6 to time t7 is the power consumption P1 of the first heater 92. The driving time of the second heater 94 is shorter than the driving time of the first heater 92.

[0086] In this embodiment, the driving of the second heater 94 is stopped between time t4 and time t5 and between time t6 and time t7, thereby reducing the power consumption of the heater device 90. In other words, in this embodiment, the power consumption of the heater device 90 can be reduced compared to the case where both the first heater 92 and the second heater 94 are continuously driven from time t4 to time t7.

[0087] In this embodiment, when driving the first heater 92 and the second heater 94 when starting up the fuel cell system 10, the heater control unit 118 drives the second heater 94 for a driving time shorter than the driving time of the first heater 92. This makes it possible to start up the fuel cell system 10 while suppressing the power consumption of the heater device 90. Therefore, it is possible to obtain a better fuel cell system 10, a control device 18, and a control method and program for the fuel cell system 10.

[0088] In addition to the above disclosure, the following notes are also disclosed.

[0089] (Appendix 1) The fuel cell system (10) comprises a fuel cell (12) that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas, a reaction exhaust gas flow path (84) connected to the fuel cell and through which a reaction exhaust gas, which is a fuel exhaust gas or an oxidant exhaust gas discharged from the fuel cell, flows, a first device (86) provided in the reaction exhaust gas flow path and in which liquid water may remain when the operation of the fuel cell is stopped, a second device (88) provided in the reaction exhaust gas flow path and in which the liquid water is not expected to remain when the operation of the fuel cell is stopped and through which water vapor flows when the fuel cell system is started, a first heater (92) that heats the first device, a second heater (94) that heats the second device, and a heater control unit (118) that can individually control the first heater and the second heater, and when the heater control unit drives the first heater and the second heater when starting up the fuel cell system, the heater control unit drives the second heater for a drive time shorter than a drive time of the first heater.

[0090] With this configuration, the fuel cell system can be started up while suppressing the power consumption of the heater device including the first heater and the second heater, thereby providing a better fuel cell system.

[0091] (Appendix 2) In the fuel cell system described in Supplementary Note 1, the heater control section may start driving the second heater after starting driving the first heater.

[0092] With this configuration, the driving time of the second heater can be easily shortened.

[0093] (Appendix 3) In the fuel cell system according to Supplementary Note 1 or 2, the heater control section may stop driving the first heater after stopping driving the second heater.

[0094] With this configuration, the driving time of the second heater can be easily shortened.

[0095] (Appendix 4) In the fuel cell system described in any one of Appendices 1 to 3, the system may further include a freezing determination unit (120) that determines whether the liquid water remaining in the first device is frozen, and the heater control unit may start driving the first heater when the freezing determination unit determines that the liquid water remaining in the first device is frozen.

[0096] According to this configuration, since the first heater can be driven when the liquid water remaining in the first device freezes, the fuel cell system can be started up reliably.

[0097] (Appendix 5) In the fuel cell system described in Appendix 4, the system may further include a thawing determination unit (122) that determines whether the frozen object of the first device has thawed, and the heater control unit may stop driving the first heater when the thawing determination unit determines that the frozen object of the first device has thawed.

[0098] With this configuration, the driving time of the first heater can be shortened.

[0099] (Appendix 6) In the fuel cell system according to claim 4 or 5, the freeze determination unit may determine that the liquid water remaining in the first device is frozen when the temperature of the first device is equal to or lower than the freezing point.

[0100] With this configuration, it is possible to easily determine whether or not the first device is frozen.

[0101] (Appendix 7) In the fuel cell system described in any one of Appendices 1 to 6, the system may further include a freeze determination unit that determines whether the water vapor circulating through the reaction exhaust gas flow path is expected to freeze in the second device, and the heater control unit may start driving the second heater when the freeze determination unit determines that the water vapor circulating through the reaction exhaust gas flow path is expected to freeze in the second device.

[0102] According to this configuration, the second heater starts to be driven when it is expected that water vapor will freeze in the second device, so that the fuel cell system can be started up reliably.

[0103] (Appendix 8) In the fuel cell system described in Appendix 7, the freeze determination unit may determine whether or not the water vapor is in a state in which it can flow to the second device, and the heater control unit may start driving the second heater when the freeze determination unit determines that the water vapor is in a state in which it can flow to the second device.

[0104] According to this configuration, the second heater starts to be driven only after the water vapor is in a state capable of flowing through the second device, so that the driving time of the second heater can be shortened.

[0105] (Appendix 9) In the fuel cell system described in Appendix 7 or 8, the heater control unit may stop driving the second heater when the freeze determination unit determines that the water vapor circulating through the reaction exhaust gas flow path is no longer expected to freeze in the second device after starting to drive the second heater.

[0106] With this configuration, the driving time of the second heater can be shortened.

[0107] (Appendix 10) In the fuel cell system described in any one of Appendices 7 to 9, the freeze determination unit may determine that the water vapor circulating through the reaction exhaust gas flow path is expected to freeze in the second device when the temperature of the fuel cell is below the freezing point.

[0108] When the temperature of the fuel cell is below the freezing point, the temperature of the reaction exhaust gas discharged from the fuel cell is relatively low, so there is a possibility that the water vapor contained in the reaction exhaust gas will freeze in the second device. With this configuration, it is possible to suppress the freezing of the water vapor in the second device.

[0109] (Appendix 11) In the fuel cell system described in any one of Appendices 1 to 10, the reaction exhaust gas flow path may include a fuel gas discharge flow path (66) through which the fuel exhaust gas flows, and the first device may include a gas-liquid separator (68) provided in the fuel gas discharge flow path, capable of separating the fuel exhaust gas into gas and liquid and storing the separated liquid water.

[0110] With this configuration, even if the liquid water remaining in the gas-liquid separator provided in the fuel gas exhaust flow path freezes when the fuel cell system is stopped, the first heater can thaw the frozen material in the gas-liquid separator when the fuel cell system is started.

[0111] (Appendix 12) In the fuel cell system described in Appendix 11, the reaction exhaust gas flow path may include a drain flow path (72) for discharging the liquid water stored in the gas-liquid separator, and the first device may include a drain valve (74) for opening and closing the drain flow path.

[0112] With this configuration, even if liquid water flows from a gas-liquid separator provided in the fuel gas exhaust flow path to the drain valve and freezes, the first heater can thaw the frozen material in the drain valve when the fuel cell system is started.

[0113] (Appendix 13) In the fuel cell system according to any one of Supplementary Notes 1 to 12, the second device may include an on-off valve (60, 78, 82) that opens and closes the reaction exhaust gas flow path.

[0114] With this configuration, it is possible to prevent water vapor from freezing in the on-off valve when starting up the fuel cell system.

[0115] (Appendix 14) The control device (18) is a control device in a fuel cell system according to any one of Supplementary Notes 1 to 13, and the control device includes the heater control unit.

[0116] (Appendix 15) A control method for a fuel cell system includes a fuel cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas, a reaction exhaust gas flow path connected to the fuel cell and through which reaction exhaust gas, which is a fuel exhaust gas or an oxidant exhaust gas discharged from the fuel cell, flows, a first device provided in the reaction exhaust gas flow path and in which liquid water may remain when the operation of the fuel cell is stopped, a second device provided in the reaction exhaust gas flow path and in which the liquid water is not expected to remain in the operation stopped state of the fuel cell and through which water vapor flows when the fuel cell system is started, a first heater that heats the first device, a second heater that heats the second device, and a heater control unit that can individually control the first heater and the second heater, wherein when the heater control unit drives the first heater and the second heater when starting up the fuel cell system, the heater control unit drives the second heater for a driving time shorter than a driving time of the first heater.

[0117] (Appendix 16) The program causes a computer to execute the fuel cell system control method described in Supplementary Note 15.

[0118] The present invention is not limited to the above disclosure, and various configurations can be adopted without departing from the gist of the present invention. [Explanation of symbols]

[0119] 10...Fuel cell system 12...Fuel cell stack (fuel cell) 18...Control device 58...First drain passage 60: First drain valve (on-off valve) 66: Fuel gas exhaust passage 68... second gas-liquid separator (gas-liquid separator) 72... second drain passage (drain passage) 74...Second drain valve (drain valve) 76...Third drain passage 78...Third drain valve (on-off valve) 80...Bleed flow path 82... Bleed valve (on-off valve) 84... Reaction exhaust gas flow path 86...First device 88...Second device 90... Heater device 92... First heater 94... second heater 118... heater control unit 120...Freeze judgment section 122...Thaw judgment section

Claims

1. a fuel cell that generates electricity through an electrochemical reaction between a fuel gas and an oxidant gas; a reaction exhaust gas flow path connected to the fuel cell, through which a reaction exhaust gas, which is a fuel exhaust gas or an oxidizer exhaust gas discharged from the fuel cell, flows; a first device that is provided in the reaction exhaust gas flow path and in which liquid water may remain when the fuel cell is in an operation stopped state; a second device provided in the reaction exhaust gas flow path, in which the liquid water is not expected to remain when the fuel cell is in the stopped state, and through which water vapor flows when the fuel cell system is started; a first heater for heating the first device; a second heater for heating the second device; a heater control unit capable of individually controlling the first heater and the second heater; Equipped with A fuel cell system, wherein when the heater control unit drives the first heater and the second heater when starting the fuel cell system, the heater control unit drives the second heater for a driving time shorter than a driving time of the first heater.

2. 2. The fuel cell system according to claim 1, The heater control unit starts driving the second heater after starting driving the first heater.

3. 2. The fuel cell system according to claim 1, The heater control unit stops driving the first heater after stopping driving the second heater.

4. 2. The fuel cell system according to claim 1, a freezing determination unit that determines whether the liquid water remaining in the first device is frozen, The heater control unit starts driving the first heater when the freeze determination unit determines that the liquid water remaining in the first device is frozen.

5. 5. The fuel cell system according to claim 4, A thawing determination unit that determines whether the frozen object in the first device has thawed, The heater control unit stops driving the first heater when the thaw determination unit determines that the frozen object of the first device has thawed.

6. 5. The fuel cell system according to claim 4, The freeze determination unit determines that the liquid water remaining in the first device is frozen when the temperature of the first device is equal to or lower than the freezing point.

7. 2. The fuel cell system according to claim 1, a freeze determination unit that determines whether or not the water vapor flowing through the reaction exhaust gas flow path is expected to freeze in the second device, A fuel cell system, wherein the heater control unit starts operating the second heater when the freeze determination unit determines that the water vapor circulating through the reaction exhaust gas flow path is expected to freeze in the second device.

8. 8. The fuel cell system according to claim 7, the freezing determination unit determines whether or not the water vapor is in a state in which the water vapor can flow through the second device; The heater control unit starts driving the second heater when the freeze determination unit determines that the water vapor is in a state in which it can flow through the second device.

9. 8. The fuel cell system according to claim 7, The heater control unit stops driving the second heater when the freeze determination unit determines that the water vapor circulating through the reaction exhaust gas flow path is no longer expected to freeze in the second device after starting to drive the second heater, a fuel cell system.

10. 8. The fuel cell system according to claim 7, The freeze determination unit determines that the water vapor flowing through the reaction exhaust gas flow passage is expected to freeze in the second device when the temperature of the fuel cell is equal to or lower than the freezing point.

11. 2. The fuel cell system according to claim 1, the reaction exhaust gas flow path includes a fuel gas discharge flow path through which the fuel exhaust gas flows, The first device is a fuel cell system including a gas-liquid separator provided in the fuel gas discharge flow path, capable of separating the fuel exhaust gas into gas and liquid and storing the separated liquid water.

12. 12. The fuel cell system according to claim 11, the reaction exhaust gas flow path includes a drain flow path for discharging the liquid water stored in the gas-liquid separator, The first device includes a drain valve that opens and closes the drain passage.

13. 2. The fuel cell system according to claim 1, The second device includes an on-off valve that opens and closes the reaction exhaust gas flow path.

14. A control device for a fuel cell system according to any one of claims 1 to 13, The control device includes the heater control unit.

15. a fuel cell that generates electricity through an electrochemical reaction between a fuel gas and an oxidant gas; a reaction exhaust gas flow path connected to the fuel cell, through which a reaction exhaust gas, which is a fuel exhaust gas or an oxidizer exhaust gas discharged from the fuel cell, flows; a first device that is provided in the reaction exhaust gas flow path and in which liquid water may remain when the fuel cell is in an operation stopped state; a second device provided in the reaction exhaust gas flow path, in which the liquid water is not expected to remain when the fuel cell is in the stopped state, and through which water vapor flows when the fuel cell system is started; a first heater for heating the first device; a second heater for heating the second device; a heater control unit capable of individually controlling the first heater and the second heater; A control method for a fuel cell system comprising: A control method for a fuel cell system, wherein when the heater control unit drives the first heater and the second heater when starting the fuel cell system, the heater control unit drives the second heater for a driving time shorter than a driving time of the first heater.

16. A program for causing a computer to execute the method for controlling a fuel cell system according to claim 15.

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