JP7783232B2 - Fuel cell system, control device, control method for fuel cell system, and program - Google Patents

Description

The present invention relates to a fuel cell system, a control device, a control method for a fuel cell system, and a program.

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

For example, Patent Document 1 discloses a fuel cell system equipped with a first heater that heats a hydrogen pressure regulating valve provided in a hydrogen supply path and a second heater that heats 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 in an inoperable state due to freezing. The second heater heats the oxygen pressure regulating valve when the air pressure regulating valve is in an inoperable state due to freezing.

Japanese Patent Application Laid-Open No. 2005-268179

There is a need for better fuel cell systems, control devices, fuel cell system control methods, and programs.

The present invention aims to solve the above-mentioned problems.

A first aspect of the present invention is a fuel cell system comprising: a fuel cell that generates electricity through an electrochemical reaction between fuel gas and oxidant gas; a reaction exhaust gas flow path connected to the fuel cell and through which reaction exhaust gas, which is fuel exhaust gas or 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 fuel cell is stopped; a second device provided in the reaction exhaust gas flow path and in which liquid water is not expected to remain when 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 the fuel cell system, the heater control unit drives the second heater for a shorter drive time than the drive time of the first heater.

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.

A third aspect of the present invention is a control method for a fuel cell system including: a fuel cell that generates electricity through an electrochemical reaction between fuel gas and oxidant gas; a reaction exhaust gas flow path connected to the fuel cell and through which reaction exhaust gas, which is fuel exhaust gas or 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 fuel cell is stopped; a second device provided in the reaction exhaust gas flow path and in which liquid water is not expected to remain when 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 the fuel cell system, the heater control unit drives the second heater for a shorter drive time than the drive time of the first heater.

A fourth aspect of the present invention is a program for causing a computer to execute the above-described fuel cell system control method.

The present invention provides a better fuel cell system, control device, fuel cell system control method, and program.

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

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 the fuel cell system 10 according to this embodiment. The fuel cell system 10 is mounted, for example, 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.

As shown in FIG. 1, the 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.

The fuel cell stack 12 generates electricity 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 multiple 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.

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 water. 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.

One separator, 24a, has an oxidant gas flow channel 32 formed on its surface facing the membrane electrode assembly 22. The oxidant gas flow channel 32 is connected to an oxidant gas inlet 34 and an oxidant gas outlet 36 of the fuel cell stack 12. The other separator, 24b, has a fuel gas flow channel 38 formed on its surface facing the membrane electrode assembly 22. The fuel gas flow channel 38 is connected to a fuel gas inlet 40 and a fuel gas outlet 42 of the fuel cell stack 12. The fuel cell stack 12 may also have components other than those described above, but a description of these components will not be provided here.

The cathode system 14 includes an oxidant gas supply unit 44, an oxidant gas supply passage 46, a supply seal valve 48, an oxidant gas discharge passage 50, a discharge seal 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 include components other than these, but these will not be described here.

The oxidant gas supply unit 44 supplies 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 34 of the fuel cell stack 12. A 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.

The oxidant gas discharge flow path 50 is connected to the oxidant gas outlet 36 of the fuel cell stack 12. The oxidant exhaust gas discharged from the fuel cell stack 12 flows through the oxidant gas discharge flow path 50. The oxidant exhaust gas contains water produced 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.

The humidifier 54 humidifies the oxidant gas flowing through the oxidant gas supply passage 46 with the oxidant exhaust gas flowing through the oxidant gas discharge passage 50. The oxidant gas guided from the oxidant gas supply unit 44 to the humidifier 54 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 via the humidifier 54 to the discharge seal valve 52.

The first drain flow path 58 is connected to 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 seal valve 52. The first drain flow path 58 is a flow path that guides 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, when the fuel cell stack 12 is in an inclined state, this refers to, for example, when the fuel cell stack 12 installed in the fuel cell vehicle is stopped on a slope, causing the fuel cell vehicle to incline.

When the fuel cell stack 12 is tilted, liquid water in the oxidant gas flow path 32 of the fuel cell stack 12 may not be discharged to the oxidant gas discharge flow path 50. Even in such a case, the liquid water in the oxidant gas flow path 32 of the fuel cell stack 12 can be smoothly discharged to the oxidant gas discharge flow path 50 via the first drain flow path 58. When the fuel cell stack 12 is horizontal, liquid water in the oxidant gas flow path 32 of the fuel cell stack 12 does not flow through the first drain flow path 58, and only the oxidant exhaust gas containing water vapor flows through the first drain flow path 58. A first drain valve 60 is provided in the first drain flow path 58. The first drain valve 60 is an on-off valve that opens and closes the first drain flow path 58.

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 equipped with components other than these, but these will not be described here.

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, and other components (not shown). The fuel gas supply passage 64 is connected to the fuel gas inlet 40 of the fuel cell stack 12.

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 water produced by the power generation of the fuel cell stack 12. A 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 recycled as fuel gas by flowing into the fuel gas supply flow path 64 via the ejector.

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 positioned directly below the second gas-liquid separator 68. The second drain valve 74 opens and closes the second drain flow path 72.

The third drain flow path 76 is connected to 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 that guides 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.

When the fuel cell stack 12 is tilted, 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 horizontal, 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. A third drain valve 78 is provided in the third drain flow path 76. The third drain valve 78 is an on-off valve that opens and closes the third drain flow path 76.

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.

The fuel exhaust gas and oxidant gas introduced through the bleed flow path 80 are mixed in the first gas-liquid separator 56. The resulting mixture of oxidant gas and fuel exhaust gas is introduced into the oxidant gas flow path 32 of the fuel cell stack 12. In the fuel cell stack 12, the fuel exhaust gas and oxidant gas in the mixture react exothermically in the electrode catalyst layer of the cathode electrode 28 to produce water. This allows the fuel cell stack 12 to be efficiently warmed up, for example, when the fuel cell system 10 is started in a low-temperature environment (e.g., below freezing). Furthermore, because 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. A bleed valve 82 is provided in the bleed flow path 80. The bleed valve 82 is an on-off valve that opens and closes the bleed flow path 80.

The fuel cell system 10 is equipped with a cooling system (not shown). The cooling system circulates a cooling medium through the fuel cell stack 12. Examples of cooling mediums include pure water, ethylene glycol, and oil.

In this embodiment, the fuel exhaust gas or oxidant exhaust gas may be referred to as a reaction exhaust gas. Furthermore, the 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.

A first device 86 and a second device 88 are provided in the reaction exhaust gas flow path 84. The first device 86 and the second device 88 are, for example, positioned relatively far from the fuel cell stack 12. In other words, the first device 86 and the second device 88 are less susceptible to heat generated by the fuel cell stack 12 when the fuel cell system 10 is started.

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. 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, making it easy for liquid water to remain when the fuel cell stack 12 is in an operation-stopped state. In addition, because the second drain valve 74 is located directly below the second gas-liquid separator 68, liquid water that has flowed downward from the second gas-liquid separator 68 is likely to remain. Liquid water remaining in the first device 86 may freeze in a low-temperature environment (e.g., an environment below the freezing point).

The second device 88 is a device through which liquid water is not expected to remain when the fuel cell stack 12 is not operating, 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 (e.g., an environment below the freezing point).

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. Furthermore, 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.

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.

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

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, for example, the temperature of a housing (not shown) of the fuel cell system 10. 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, for example, the temperature of the cooling medium circulating within the fuel cell stack 12.

The control device 18 has a calculation unit 110 and a memory unit 112. The calculation unit 110 is composed of a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). In other words, the calculation unit 110 is composed of processing circuitry.

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

At least a portion of the control unit 114, temperature acquisition unit 116, heater control unit 118, freeze determination unit 120, and thaw determination unit 122 may be implemented using an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field-Programmable Gate Array). Also, at least a portion of the control unit 114, temperature acquisition unit 116, heater control unit 118, freeze determination unit 120, and thaw determination unit 122 may be implemented using electronic circuits including discrete devices.

The storage unit 112 is composed of volatile memory (not shown) and non-volatile memory (not shown). Examples of volatile memory include RAM (Random Access Memory). Volatile memory is used as working memory for the processor, and temporarily stores data necessary for processing or calculations. Examples of non-volatile memory include ROM (Read Only Memory) and flash memory. Non-volatile memory is used as storage memory, and stores programs, tables, maps, etc. At least a portion of the storage unit 112 may be provided in the processor, integrated circuit, etc. described above.

The control unit 114 is responsible for overall control of the fuel cell system 10. The temperature acquisition unit 116 can determine 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 unit 18. The temperature acquisition unit 116 can determine 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 unit 18.

The heater control unit 118 controls the first heater 92 and the second heater 94 individually. 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.

The freezing determination unit 120 determines whether the liquid water remaining in the first device 86 is frozen. The freezing determination unit 120 determines whether the water vapor flowing through the reaction exhaust gas flow path 84 is expected to freeze in the second device 88. The thawing determination unit 122 determines whether the frozen material in the first device 86 has thawed.

Figure 3 is a flowchart illustrating a control method for the fuel cell system 10.

In step S1, the control unit 114 stops 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 operation of the fuel cell system 10. It is common for a certain amount of time to elapse between step S1 and step S2 (described below), but this is not limited to this.

In step S2, the control unit 114 starts the fuel cell system 10. Specifically, for example, when the user turns on the power switch, the control unit 114 starts the fuel cell system 10. When the fuel cell system 10 starts, 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 electricity through an electrochemical reaction between the fuel gas and the oxidant gas. After step S2, the process proceeds to step S3.

In step S3, the freezing determination unit 120 determines whether 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 if 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 if 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.

If the freezing determination unit 120 determines that the liquid water remaining in the first device 86 is not frozen (NO in step S3), the process shown in FIG. 3 is completed. That is, the fuel cell system 10 is started without driving the first heater 92 and the second heater 94. If 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.

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. Then, the process proceeds to step S5.

When the fuel cell stack 12 generates electricity, water is generated inside the fuel cell stack 12. The generated water flows as water vapor into the reaction exhaust gas flow path 84 together with the reaction exhaust gas. As a result, the water vapor that flows into the reaction exhaust gas flow path 84 may freeze in the second device 88.

In this embodiment, therefore, in step S5, the freezing determination unit 120 determines whether water vapor is expected to freeze in the second device 88. Specifically, if 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. If the temperature of the fuel cell stack 12 is below the freezing point, the freezing determination unit 120 determines that water vapor is expected to freeze in the second device 88.

If the freezing determination unit 120 determines that 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 water vapor is expected to freeze in the second device 88 (YES in step S5), the process proceeds to step S6.

When the fuel cell stack 12 begins generating electricity, the electrolyte membrane 26 absorbs the water produced 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 water vapor contained in the reaction exhaust gas is unlikely to freeze in the second device 88. 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. As a result, the amount of water vapor contained in the reaction exhaust gas increases. Therefore, the water vapor in the reaction exhaust gas is likely to freeze in the second device 88.

In step S6, the freezing determination unit 120 determines whether water vapor is able to flow through the second device 88. Specifically, the freezing determination unit 120 determines that water vapor is able to flow through the second device 88 if the time elapsed since the start of power generation in the fuel cell stack 12 reaches a predetermined water vapor flow start time. The freezing determination unit 120 determines that water vapor is not able to flow through the second device 88 if the time elapsed since the start of power generation in the fuel cell stack 12 has not reached the predetermined water vapor flow start time.

The water vapor flow start time can be set, for example, to the time from when power generation by the fuel cell stack 12 begins until the amount of water produced and absorbed by the electrolyte membrane 26 reaches the upper limit of the amount of water that can be absorbed by the electrolyte membrane 26. The freeze determination unit 120 may also determine whether water vapor can flow through the second device 88 based on, for example, the output signal of a water vapor sensor provided in the second device 88.

If the freezing 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 freezing 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.

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. Then, the process proceeds to step S8.

In step S8, the freezing determination unit 120 determines whether water vapor is no longer expected to freeze in the second device 88. Specifically, 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 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 predetermined temperature can be set as appropriate, 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, approximately 20°C. The freeze determination unit 120 may also determine whether water vapor is no longer expected to freeze in the second device 88 based on the elapsed time since the fuel cell stack 12 began startup.

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

In step S9, the heater control unit 118 stops driving the second heater 94. Then, the process proceeds to step S10.

In step S10, the thawing determination unit 122 determines whether the frozen item in the first device 86 has thawed. Specifically, the thawing determination unit 122 determines that the frozen item in the first device 86 has thawed if the temperature of the first device 86 is higher than the freezing point. The thawing determination unit 122 determines that the frozen item in the first device 86 has not thawed if the temperature of the first device 86 is below the freezing point.

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

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.

In step S11, the heater control unit 118 stops driving the first heater 92. This completes the process shown in Figure 3.

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

As shown in FIG. 4, for example, when the control unit 114 stops 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 faster rate 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.

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

If the fuel cell system 10 is started after time t2 but before time t3, the temperature of the first device 86 will be below 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 will be above freezing point, and the temperature of the reaction exhaust gas discharged from the fuel cell stack 12 will also be above freezing point. Therefore, even if the temperature of the second device 88 is below freezing point, the water vapor contained in the reaction exhaust gas is unlikely to freeze in the second device 88.

Therefore, if 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 reduces 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.

If the fuel cell system 10 is started after time t3, the temperature of both the fuel cell stack 12 and the first device 86 will be below freezing. The control of the fuel cell system 10 in this case will be explained with reference to Figures 5 and 6.

Figure 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 Figure 5 shows the temperature change of the first device 86, and line segment L4 shows the temperature change of the fuel cell stack 12. Figure 6 is a graph showing the relationship between the drive time of the first heater 92 and the second heater 94 and the power consumption. In Figure 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 by the battery 96.

In the example shown in Figures 5 and 6, at time t4, the fuel cell system 10 is started and the first heater 92 begins operating. Note that the second heater 94 has not yet begun operating at time t4.

As shown in FIG. 5, when the fuel cell stack 12 begins generating electricity following startup of the fuel cell system 10, the fuel cell stack 12 generates heat. As a result, the temperature of the fuel cell stack 12 rises at a rate greater than the rate of increase in the temperature of the first device 86.

Furthermore, when the fuel cell stack 12 begins generating power, the electrolyte membrane 26 absorbs the water produced 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. As a result, the amount of water vapor contained in the reaction exhaust gas increases at time t5. In other words, at time t5, the water vapor contained in the reaction exhaust gas is more likely to freeze in the second device 88. Note that between time t4 and time t5, the amount of water vapor contained in the reaction exhaust gas is negligibly small.

For this reason, as shown in Figures 5 and 6, at time t5, the second heater 94 begins to be driven. This prevents the water vapor contained in the reaction exhaust gas from freezing in the second device 88.

Then, 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 operation of the second heater 94 is stopped. In this case, as shown in FIG. 6, the operation time of the second heater 94 is the period from time t5 to time t6. In other words, the heater control unit 118 starts operation of the first heater 92, and then starts operation of the second heater 94.

At time t6, the temperature of the reaction exhaust gas discharged from the fuel cell stack 12 becomes relatively high. This reduces the likelihood that the water vapor contained in the reaction exhaust gas will freeze in the second device 88. The second heater 94 may be stopped from operating when the temperature of the fuel cell stack 12 reaches a predetermined temperature (e.g., 20°C) that is higher than the freezing point. In this case, the temperature of the reaction exhaust gas is sufficiently high, further reducing the risk of the water vapor contained in the reaction exhaust gas freezing in the second device 88.

Then, 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 driving the second heater 94.

As such, 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 less than the maximum power supply 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 less than the power consumption P1 of the first heater 92. The power consumption P3 of the heater device 90 is less than the maximum power supply 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 drive time of the second heater 94 is shorter than the drive time of the first heater 92.

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 when both the first heater 92 and the second heater 94 are continuously driven between time t4 and time t7.

In this embodiment, when the heater control unit 118 drives the first heater 92 and the second heater 94 when starting the fuel cell system 10, it drives the second heater 94 for a shorter drive time than the drive time of the first heater 92. This allows the fuel cell system 10 to be started while suppressing the power consumption of the heater device 90. This makes it possible to obtain a better fuel cell system 10, control device 18, control method and program for the fuel cell system 10.

The following additional information is provided in relation to the above disclosure:

(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 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 the fuel cell system, the heater control unit drives the second heater for a driving time that is shorter than the driving time of the first heater.

This configuration allows the fuel cell system to be started while reducing the power consumption of the heater device equipped with the first heater and second heater. This results in a better fuel cell system.

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

This configuration makes it easy to shorten the drive time of the second heater.

(Appendix 3)
In the fuel cell system described in Supplementary Note 1 or 2, the heater control unit may stop driving the first heater after stopping driving the second heater.

This configuration makes it easy to shorten the drive time of the second heater.

(Appendix 4)
In the fuel cell system described in any one of Appendices 1 to 3, the system may further include a freeze 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 freeze determination unit determines that the liquid water remaining in the first device is frozen.

With this configuration, the first heater can be driven when the liquid water remaining in the first device freezes, ensuring reliable start-up of the fuel cell system.

(Appendix 5)
In the fuel cell system described in Appendix 4, a thawing determination unit (122) may be further provided that determines whether the frozen material in 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 material in the first device has thawed.

This configuration allows the first heater's driving time to be shortened.

(Appendix 6)
In the fuel cell system described in Supplementary Note 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 below freezing.

This configuration makes it easy to determine whether the first device is frozen.

(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 flowing 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 flowing through the reaction exhaust gas flow path is expected to freeze in the second device.

With this configuration, the second heater begins operating when it is expected that water vapor will freeze in the second device, ensuring reliable start-up of the fuel cell system.

(Appendix 8)
In the fuel cell system described in Appendix 7, the freeze determination unit may determine whether the water vapor is in a state where 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 where it can flow to the second device.

With this configuration, the second heater begins to operate only after water vapor is able to flow through the second device, thereby shortening the operating time of the second heater.

(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 freezing 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.

This configuration allows the second heater to be driven for a shorter time.

(Appendix 10)
In the fuel cell system described in any one of Appendices 7 to 9, the freezing 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 freezing point.

When the temperature of the fuel cell is below freezing, the temperature of the reaction exhaust gas discharged from the fuel cell is relatively low, and there is a possibility that the water vapor contained in the reaction exhaust gas will freeze in the second device. This configuration can prevent the water vapor from freezing in the second device.

(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, which separates the fuel exhaust gas into gas and liquid and is capable of storing the separated liquid water.

With this configuration, even if the liquid water remaining in the gas-liquid separator installed in the fuel gas discharge flow path freezes while the fuel cell system is stopped, the first heater can thaw the frozen liquid in the gas-liquid separator when the fuel cell system is started.

(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.

With this configuration, even if liquid water flows from the gas-liquid separator installed in the fuel gas discharge flow path into the drain valve and freezes, the first heater can thaw the frozen material in the drain valve when the fuel cell system is started.

(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.

This configuration prevents water vapor from freezing in the on-off valve when starting the fuel cell system.

(Appendix 14)
A 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 has the heater control unit.

(Appendix 15)
A control method for a fuel cell system includes: 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 and through which reaction exhaust gas, which is fuel exhaust gas or 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 fuel cell is in an operation-stopped state; a second device provided in the reaction exhaust gas flow path and in which liquid water is not expected to remain when the fuel cell is in an operation-stopped state 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 the fuel cell system, the heater control unit drives the second heater for a driving time that is shorter than the driving time of the first heater.

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

The present invention is not limited to the above disclosure, and various configurations may be adopted without departing from the spirit of the present invention.

10... fuel cell system 12... fuel cell stack (fuel cell)
18...Control device 58...First drain flow path 60...First drain valve (on/off valve) 66...Fuel gas discharge flow path 68...Second gas-liquid separator (gas-liquid separator) 72...Second drain flow path (drain flow path)
74... Second drain valve (drain valve) 76... Third drain flow path 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... Freezing determination unit 122... Thawing determination unit

Claims (18)

a fuel cell that generates electricity through an electrochemical reaction between a fuel gas and an oxidant gas;
a fluid flow path connected to the fuel cell and through which a fluid discharged from the fuel cell flows;
a first device and a second device provided in the fluid flow path;
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 fuel cell system comprising :
The fluid flow path is
a fuel gas discharge flow path through which a fuel exhaust gas discharged from the fuel cell flows;
an oxidizing gas discharge flow path through which oxidizing exhaust gas discharged from the fuel cell flows;
a drain passage communicating with the oxidant gas passage of the fuel cell, for guiding liquid water in the oxidant gas passage to the oxidant gas discharge passage when the fuel cell is in an inclined state;
and
a gas-liquid separator that separates the fuel exhaust gas into gas and liquid and stores the separated liquid water is provided in the fuel gas discharge flow path;
The drain passage is provided with a drain valve that opens and closes the drain passage,
When the fuel cell is in a horizontal position, an oxidizing exhaust gas containing water vapor flows through the drain passage,
the first device includes the gas-liquid separator;
the second device includes the drain valve;
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 that is shorter than the driving time of the first heater. 2. The fuel cell system according to claim 1,
The heater control unit starts driving the second heater after starting driving the first heater. 2. The fuel cell system according to claim 1,
The heater control unit stops driving the first heater after stopping driving the second heater. 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. 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 in the first device has thawed. 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 below freezing. 2. The fuel cell system according to claim 1,
a freeze determination unit that determines whether the water vapor flowing through the fluid flow path is expected to freeze in the second device;
The heater control unit starts driving the second heater when the freezing determination unit determines that the water vapor circulating through the fluid flow path is expected to freeze in the second device. 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 it can circulate 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 where it can circulate through the second device. 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 fluid flow path is no longer expected to freeze in the second device after starting to drive the second heater. 8. The fuel cell system according to claim 7,
The freeze determination unit determines that the water vapor flowing through the fluid flow path is likely to freeze in the second device when the temperature of the fuel cell is below freezing. 2. The fuel cell system according to claim 1,
the fluid flow path connects the gas-liquid separator and the oxidant gas discharge flow path, and includes a flow path that guides the liquid water stored in the gas-liquid separator together with the fuel exhaust gas to the oxidant gas discharge flow path,
an on-off valve for opening and closing the flow path is provided in the flow path;
The first device includes the on-off valve . 2. The fuel cell system according to claim 1 ,
an oxidant gas supply channel for supplying an oxidant gas to the fuel cell;
a first gas-liquid separator provided in the oxidant gas supply channel for separating the oxidant gas into gas and liquid;
Furthermore,
the fluid flow path has a bleed flow path that guides the fuel exhaust gas that has flowed through a second gas-liquid separator that is the gas-liquid separator to the first gas-liquid separator,
the fuel exhaust gas flowing through the bleed flow path contains the water vapor that was not removed by the second gas-liquid separator,
a bleed valve that opens and closes the bleed flow path is provided in the bleed flow path,
The first device includes the bleed valve . a fuel cell that generates electricity through an electrochemical reaction between a fuel gas and an oxidant gas;
a fluid flow path connected to the fuel cell and through which a fluid discharged from the fuel cell flows;
a first device and a second device provided in the fluid flow path;
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 fuel cell system comprising:
The fluid flow path is
a fuel gas discharge flow path through which a fuel exhaust gas discharged from the fuel cell flows;
an oxidizing gas discharge flow path through which oxidizing exhaust gas discharged from the fuel cell flows;
a drain passage communicating with a fuel gas passage of the fuel cell, for guiding liquid water in the fuel gas passage to the oxidant gas discharge passage when the fuel cell is in an inclined state;
and
a gas-liquid separator that separates the fuel exhaust gas into gas and liquid and stores the separated liquid water is provided in the fuel gas discharge flow path;
The drain passage is provided with a drain valve that opens and closes the drain passage,
When the fuel cell is in a horizontal position, fuel gas containing water vapor flows through the drain passage,
the first device includes the gas-liquid separator;
the second device includes the drain valve;
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 that is shorter than the driving time of the first heater . 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. a fuel cell that generates electricity through an electrochemical reaction between a fuel gas and an oxidant gas;
a fluid flow path connected to the fuel cell and through which a fluid discharged from the fuel cell flows;
a first device and a second device provided in the fluid flow path;
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:
The fluid flow path is
a fuel gas discharge flow path through which a fuel exhaust gas discharged from the fuel cell flows;
an oxidizing gas discharge flow path through which oxidizing exhaust gas discharged from the fuel cell flows;
a drain passage communicating with the oxidant gas passage of the fuel cell, for guiding liquid water in the oxidant gas passage to the oxidant gas discharge passage when the fuel cell is in an inclined state;
and
a gas-liquid separator that separates the fuel exhaust gas into gas and liquid and stores the separated liquid water is provided in the fuel gas discharge flow path;
The drain passage is provided with a drain valve that opens and closes the drain passage,
When the fuel cell is in a horizontal position, an oxidizing exhaust gas containing water vapor flows through the drain passage,
the first device includes the gas-liquid separator;
the second device includes the drain valve;
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 the driving time of the first heater. a fuel cell that generates electricity through an electrochemical reaction between a fuel gas and an oxidant gas;
a fluid flow path connected to the fuel cell and through which a fluid discharged from the fuel cell flows;
a first device and a second device provided in the fluid flow path;
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:
The fluid flow path is
a fuel gas discharge flow path through which a fuel exhaust gas discharged from the fuel cell flows;
an oxidizing gas discharge flow path through which oxidizing exhaust gas discharged from the fuel cell flows;
a drain passage communicating with a fuel gas passage of the fuel cell, for guiding liquid water in the fuel gas passage to the oxidant gas discharge passage when the fuel cell is in an inclined state;
and
a gas-liquid separator that separates the fuel exhaust gas into gas and liquid and stores the separated liquid water is provided in the fuel gas discharge flow path;
The drain passage is provided with a drain valve that opens and closes the drain passage,
When the fuel cell is in a horizontal position, fuel gas containing water vapor flows through the drain passage,
the first device includes the gas-liquid separator;
the second device includes the drain valve;
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 the driving time of the first heater. A program for causing a computer to execute the fuel cell system control method described in claim 15. A program for causing a computer to execute the fuel cell system control method according to claim 16.