fuel cell system

Abstract

To appropriately adjust a humidification amount supplied to oxidant gas from a humidifier in a fuel cell system mounted on a moving body or the like.SOLUTION: A fuel cell system (12) includes: a humidifier (30) configured to humidify a fuel cell stack (18); a temperature adjustment device (26) configured to adjust stack temperature; a temperature acquisition device (76) configured to acquire stack temperature; and a control device (170) configured to acquire a humidification amount to be supplied from the humidifier (30) to the fuel cell stack (18) based on the stack temperature obtained by the temperature acquisition device (76) to control the stack temperature by the temperature adjustment device (26). The control device (170) of the fuel cell system controls the temperature adjustment device (26) so that steam in oxidant off-gas discharged from the fuel cell stack (18) is in a saturated state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system mounted on a vehicle or the like. [Background technology]

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

[0003] A fuel cell stack has a plurality of stacked power generation cells. Each power generation cell has an electrolyte membrane, a cathode electrode, and an anode electrode. The power generation cell generates electricity by reacting an oxidant gas supplied to the cathode electrode with a fuel gas supplied to the anode electrode. The oxidant gas is humidified by a humidifier before being supplied to the fuel cell stack. This prevents the electrolyte membrane from drying out.

[0004] Patent Document 1 discloses a fuel cell system that can be mounted on a vehicle or the like. In this fuel cell system, off-gas contacts one side of a water vapor permeable membrane (electrolyte membrane), and liquid water contacts the other side of the water vapor permeable membrane. This fuel cell system can lower the temperature of the oxidant off-gas by utilizing the latent heat generated when the liquid water evaporates. This fuel cell system can optimize the temperature of the oxidant off-gas supplied to the humidifier, thereby humidifying the oxidant gas. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-151062 Summary of the Invention [Problem to be solved by the invention]

[0006] In order to ensure the humidifying performance of a humidifier, it is necessary to know the amount of humidification by the humidifier. Patent Document 1 does not disclose a method for knowing the amount of humidification by the humidifier.

[0007] The present invention aims to solve the above-mentioned problems. [Means for solving the problem]

[0008] A fuel cell system according to one aspect of the present invention comprises a fuel cell stack that generates electricity using an oxidant gas and a fuel gas, a supply flow path through which the oxidant gas supplied to the fuel cell stack flows, an exhaust flow path through which oxidant off-gas discharged from the fuel cell stack flows, a humidifier connected to the supply flow path and the exhaust flow path and that keeps the fuel cell stack in a humidified state, a temperature adjustment device that adjusts the stack temperature, which is the temperature of the fuel cell stack, a temperature acquisition device that acquires the stack temperature, and a control device that acquires the amount of humidification supplied to the fuel cell stack from the humidifier device based on the stack temperature acquired by the temperature acquisition device and controls the stack temperature using the temperature adjustment device, and the control device controls the temperature adjustment device so that the vapor in the oxidant off-gas discharged from the fuel cell stack is saturated. [Effects of the Invention]

[0009] According to the present invention, since the vapor in the oxidant off-gas discharged from the fuel cell stack is saturated, it is not necessary to consider changes in the humidification amount of the oxidant off-gas that accompany changes in the operating state of the fuel cell stack, and the humidification amount supplied to the oxidant gas from the humidifier can be efficiently determined. As a result, the humidification amount supplied to the oxidant gas from the humidifier can be appropriately adjusted. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a fuel cell vehicle incorporating a fuel cell system according to the present invention. [Figure 2] Figure 2 is a psychrometric chart. [Figure 3] FIG. 3 is a flowchart showing the procedure of the humidification process. DETAILED DESCRIPTION OF THE INVENTION

[0011] [1 Configuration of fuel cell system 12] 1 is a schematic diagram of a fuel cell vehicle 10 incorporating a fuel cell system 12 according to the present invention. The fuel cell system 12 can also be incorporated into other moving objects such as ships, aircraft, and robots in addition to the fuel cell vehicle 10. The fuel cell system 12 contributes to energy efficiency.

[0012] The fuel cell vehicle 10 is composed of a fuel cell system 12, an ECU 15, and an output unit 16. The ECU 15 controls the entire fuel cell vehicle 10. The ECU 15 may be divided into two or more units rather than one. The output unit 16 is electrically connected to the fuel cell system 12.

[0013] The fuel cell system 12 includes a fuel cell stack 18, a hydrogen tank 20, an oxidizing gas supply device 22, a fuel gas supply device 24, and a coolant supply device (temperature adjustment device) .

[0014] The oxidant gas supply device 22 includes a compressor (CP) 28 and a humidifier (HUM) 30.

[0015] The fuel gas supply device 24 includes an injector (INJ) 32, an ejector 34, and a gas-liquid separator 36. The injector 32 may be replaced with a pressure reducing valve.

[0016] The coolant supply system 26 includes a coolant pump (WP) 38 and a radiator 40 .

[0017] The output unit 16 includes a drive unit 42, a high-voltage electricity storage device 44, and a motor 46. The load of the drive unit 42 includes the motor 46, which is the main engine, as well as the compressor 28, which is an auxiliary engine, and other vehicle accessories such as an air conditioner. The fuel cell vehicle 10 runs using the driving force generated by the motor 46.

[0018] A plurality of power generating cells 50 are stacked in the fuel cell stack 18. The power generating cell 50 includes a membrane electrode assembly 52 and separators 53 and 54 that sandwich the membrane electrode assembly 52.

[0019] The membrane electrode assembly 52 has a solid polymer electrolyte membrane 55 (also simply referred to as the electrolyte membrane 55), a cathode electrode 56, and an anode electrode 57. The electrolyte membrane 55 is, for example, a thin film of perfluorosulfonic acid containing water. The cathode electrode 56 and the anode electrode 57 sandwich the electrolyte membrane 55. The cathode electrode 56 and the anode electrode 57 have gas diffusion layers made of carbon paper or the like. An electrode catalyst layer is formed by uniformly applying porous carbon particles to the surface of the gas diffusion layer. A platinum alloy is supported on the surface of the porous carbon particles. The electrode catalyst layers are formed on both sides of the electrolyte membrane 55.

[0020] A cathode flow channel 58 is formed on the surface of one separator 53 facing the membrane electrode assembly 52. ​​The cathode flow channel 58 connects the oxidant gas inlet communication port 101 and the oxidant gas outlet communication port .

[0021] An anode flow channel 59 is formed on the surface of the other separator 54 facing the membrane electrode assembly 52. ​​The anode flow channel 59 connects the fuel gas inlet communication port 103 and the fuel gas outlet communication port 104.

[0022] At the anode electrode 57, when fuel gas (hydrogen) is supplied, hydrogen ions are generated from hydrogen molecules through a catalytic electrode reaction, and the hydrogen ions permeate the solid polymer electrolyte membrane 55 and move to the cathode electrode 56, while electrons are released from the hydrogen molecules.

[0023] The electrons released from the hydrogen molecules move from the negative terminal 106 through a load such as the drive unit 42 and the motor 46, and via the positive terminal 108 to the cathode electrode 56.

[0024] At the cathode electrode 56, the hydrogen ions and electrons react with the oxygen contained in the supplied oxidant gas due to the action of the catalyst to produce water.

[0025] A voltage sensor 110 is provided between the wiring connecting the positive terminal 108 and the drive unit 42 and the wiring connecting the negative terminal 106 and the drive unit 42. The voltage sensor 110 detects the voltage generated by the fuel cell stack 18. Furthermore, a current sensor 112 that detects the current generated by the fuel cell stack 18 is provided on the wiring connecting the positive terminal 108 and the drive unit 42.

[0026] Compressor 28 is composed of a mechanical supercharger or the like driven by a motor (not shown). Electric power from a power storage device 44 is supplied to the motor of compressor 28 through drive unit 42. Compressor 28 has functions such as drawing in air from outside air intake 113, pressurizing the air, and supplying the air to fuel cell stack 18 through humidifier 30.

[0027] The humidifier 30 has a flow path 31A and a flow path 31B. High-temperature, dry air (oxidant gas) discharged from the compressor 28 flows through the flow path 31A. Exhaust gas discharged from the oxidant gas outlet communication port 102 of the fuel cell stack 18 flows through the flow path 31B.

[0028] Here, when a bleed valve 70 (described later) is closed, the exhaust gas becomes a wet oxidizer off-gas. , B When the reed valve 70 is open, wet exhaust gas (off-gas) containing a mixture of wet oxidant off-gas and fuel off-gas flows.

[0029] The humidifier 30 has a function of humidifying the oxidant gas supplied from the compressor 28. That is, the humidifier 30 humidifies the oxidant gas by transferring moisture contained in the exhaust gas (off-gas) from the flow path 31B to the flow path 31A via the internal porous membrane, and supplies the humidified oxidant gas to the fuel cell stack 18.

[0030] An oxidant gas supply channel (supply channel) 60 is provided between the outside air intake 113 and the oxidant gas inlet manifold 101. The oxidant gas supply channel 60 has an oxidant gas supply channel 60A on the upstream side and an oxidant gas supply channel 60B on the downstream side, with a connection to a bypass channel 64 (described later) as the boundary. The oxidant gas supply channel 60A is provided with, in this order from upstream to downstream, an outside air intake 113, a shutoff valve 114, an air flow sensor (AFS) 116, and a compressor 28. The oxidant gas supply channel 60B is provided with, in this order from upstream to downstream, a supply-side shutoff valve 118 and a humidifier 30. Note that channels such as the oxidant gas supply channel 60 depicted with double lines are formed by piping (the same applies hereinafter).

[0031] The shutoff valve 114 is opened or closed to allow or block the intake of air into the oxidant gas supply passage 60 .

[0032] The airflow sensor 116 measures the flow rate of the oxidant gas supplied to the fuel cell stack 18 through the compressor 28 .

[0033] The supply-side shutoff valve 118 opens and closes the oxidizing gas supply channel 60A.

[0034] An oxidant gas discharge flow path (discharge flow path) 62 is provided between the oxidant gas outlet communication port 102 and the junction flow path 99. The oxidant gas discharge flow path 62 has an oxidant gas discharge flow path 62A on the upstream side and an oxidant gas discharge flow path 62B on the downstream side, with the connection to a bypass flow path 64 (described later) as the boundary. A humidifier 30 and a discharge-side seal valve 120 are provided in the oxidant gas discharge flow path 62A, in this order from upstream to downstream. The discharge-side seal valve 120 also functions as a backpressure valve.

[0035] A bypass flow path 64 is provided between the inlet of the supply-side seal valve 118 and the outlet of the discharge-side seal valve 120. The bypass flow path 64 connects the oxidant gas supply flow path 60 and the oxidant gas discharge flow path 62. A bypass valve 124 that opens and closes the bypass flow path 64 is provided in the bypass flow path 64. The bypass valve 124 adjusts the flow rate of the oxidant gas that bypasses the fuel cell stack 18.

[0036] The hydrogen tank 20 is a container equipped with an electromagnetically operated shutoff valve and stores high-purity hydrogen compressed at high pressure.

[0037] The fuel gas discharged from the hydrogen tank 20 passes through the injector 32 and ejector 34 provided in the fuel gas supply passage 72, and is supplied to the inlet of the anode passage 59 of the fuel cell stack 18 via the fuel gas inlet communication port 103.

[0038] The outlet of the anode flow channel 59 is connected to the inlet 151 of the gas-liquid separator 36 via the fuel gas outlet communication port 104 and the fuel off-gas flow channel 74 for fuel gas. The fuel off-gas, which is a hydrogen-containing gas, is supplied from the anode flow channel 59 to the gas-liquid separator 36.

[0039] Gas-liquid separator 36 separates the fuel off-gas into a gas component and a liquid component (liquid water). The gas component (fuel exhaust gas) of the fuel off-gas is discharged from gas outlet 152 of gas-liquid separator 36 and supplied to the suction port of ejector 34 through circulation flow path 77. On the other hand, when bleed valve 70 is opened, fuel off-gas is also supplied to oxidant gas supply flow path 60B through connection flow path 78 and bleed valve 70.

[0040] The liquid component of the fuel exhaust gas flows from the liquid outlet 160 of the gas-liquid separator 36 through a drain flow path 162 provided with a drain valve 164 as a second opening / closing valve, mixes with the exhaust gas discharged from the oxidant gas discharge flow path 62B, and is discharged to the outside air through the confluence flow path 99 and the discharge port 168.

[0041] A portion of the fuel off-gas (hydrogen-containing gas) is discharged together with the liquid component to the drain passage 162. In order to dilute the hydrogen gas in the fuel off-gas and discharge it to the outside, a portion of the oxidant gas discharged from the compressor 28 is supplied to the oxidant gas discharge passage 62B through the bypass passage 64.

[0042] The circulation flow path 77 and the oxidant gas supply flow path 60B are connected by a connection flow path 78. A bleed valve 70 is provided in the connection flow path 78. When the bleed valve 70 is opened, the fuel off-gas discharged from the fuel cell stack 18 flows into the cathode flow path 58 via the fuel off-gas flow path 74, the gas-liquid separator 36, the circulation flow path 77, the connection flow path 78, the oxidant gas supply flow path 60B, and the oxidant gas inlet manifold 101.

[0043] The fuel gas in the fuel off-gas that flows through the cathode flow path 58 is converted into hydrogen ions through a catalytic reaction at the cathode electrode 56, and the hydrogen ions react with the oxidant gas to produce water. The remaining unreacted fuel off-gas (consisting of nitrogen gas and a small amount of unreacted hydrogen gas) is discharged from the fuel cell stack 18 as oxidant off-gas and flows through the oxidant gas discharge flow path 62.

[0044] The oxidant off-gas (including the remaining unreacted fuel off-gas) flowing through the oxidant gas discharge flow path 62 is mixed with the oxidant gas supplied through the bypass flow path 64. In this way, the oxidant off-gas in which the concentration of fuel off-gas (including fuel gas) in the oxidant off-gas is diluted flows through the oxidant gas discharge flow path 62B.

[0045] The oxidizing gas discharge channel 62B joins with the drain channel 162. The oxidizing gas discharge channel 62B and the drain channel 162 communicate with the joining channel 99.

[0046] In the junction flow path 99, the oxidant off-gas from the oxidant gas discharge flow path 62B dilutes the fuel gas in the mixed fluid of liquid water and fuel off-gas discharged from the drain flow path 162. The diluted gas is discharged to the outside of the fuel cell vehicle 10 through the discharge port 168.

[0047] The refrigerant supply device 26 has a refrigerant flow path 138 that circulates the refrigerant. The refrigerant flow path 138 has a refrigerant supply flow path 140, a refrigerant discharge flow path 142, and a refrigerant bypass flow path 144. The refrigerant supply flow path 140 supplies the refrigerant to the fuel cell stack 18. The refrigerant discharge flow path 142 discharges the refrigerant from the fuel cell stack 18. A radiator 40 is connected to the refrigerant supply flow path 140 and the refrigerant discharge flow path 142. The radiator 40 cools the refrigerant. A refrigerant pump 38 is provided in the refrigerant supply flow path 140. A refrigerant bypass flow path 144 is connected to the refrigerant supply flow path 140 and the refrigerant discharge flow path 142. The refrigerant bypass flow path 144 is connected to a portion of the refrigerant supply flow path 140 between the refrigerant pump 38 and the radiator 40. A refrigerant bypass valve 146 that opens and closes the refrigerant bypass flow path 144 is provided in the refrigerant bypass flow path 144.

[0048] A temperature sensor (temperature acquisition device) 76 is provided in the coolant discharge flow path 142. There is a correlation between the temperature of the coolant flowing through the coolant discharge flow path 142 and the temperature inside the fuel cell stack 18. In this embodiment, the temperature of the cooling medium (coolant outlet temperature) detected by the temperature sensor 76 is detected (acquired) as the temperature inside the fuel cell stack 18. The temperature inside the fuel cell stack 18 is referred to as a stack temperature Ts.

[0049] The ECU 15 has a control device 170 and a storage device 172. The control device 170 has a processing circuit. The processing circuit may be a processor such as a CPU. The processing circuit may be an integrated circuit such as an ASIC or an FPGA. The processor is capable of performing various processes by executing programs stored in the storage device 172. At least some of the processes may be performed by electronic circuits including discrete devices.

[0050] The control device 170 controls the operation of the fuel cell system 12. For example, the control device 170 receives signals transmitted from various sensors. Based on the received detection signals, the control device 170 outputs control signals for controlling each valve, the compressor 28, the injector 32, the refrigerant pump 38, etc. Each valve, the compressor 28, the injector 32, the refrigerant pump 38, etc. operates in response to the control signals.

[0051] The storage device 172 has a volatile memory and a non-volatile memory. Examples of the volatile memory include RAM. The volatile memory is used as a working memory for the processor. The volatile memory temporarily stores data required for processing or calculation. Examples of the non-volatile memory include ROM and flash memory. The non-volatile memory is used as a storage memory. The non-volatile memory stores programs, tables, maps, etc. At least a portion of the storage device 172 may be provided in the processor, integrated circuit, etc. described above.

[0052] The nonvolatile memory stores a table (or map) that associates the power generation current of the fuel cell stack 18 with a temperature upper limit value Tuplim. This table is referred to as the first table. The temperature upper limit value Tuplim is a temperature that ensures that the vapor in the off-gas is saturated. In other words, the temperature upper limit value Tuplim is the temperature at which the relative humidity of the off-gas at the oxidant gas outlet manifold 102 is 100% or higher, i.e., the temperature at which condensation occurs. The nonvolatile memory also stores a table (or map) that associates the saturated vapor pressure of the fuel cell stack 18 with the amount of humidification. This table is referred to as the second table. The nonvolatile memory also stores a saturated vapor pressure curve.

[0053] [2 Operation of fuel cell stack 18 regarding humidification] As described above, the humidifier 30 humidifies the oxidant gas by transferring moisture in the off-gas discharged from the cathode flow path 58 from flow path 31B to flow path 31A. In other words, the amount of humidification by the humidifier 30 depends on the amount of moisture in the off-gas discharged from the fuel cell stack 18. Therefore, by determining the amount of moisture in the off-gas, it is possible to determine the amount of humidification by the humidifier 30. In this embodiment, the moisture (vapor) in the off-gas is saturated as a method for determining the amount of moisture in the off-gas. More specifically, the off-gas is brought to a state where condensation occurs.

[0054] FIG. 2 is a psychrometric chart. When the amount of steam in the off-gas is constant, condensation occurs when the temperature of the off-gas enters a temperature region 174 below a dew-point temperature T corresponding to the amount of steam. The temperature region 174 is a low-temperature region (including the saturation line 176) with a saturation line 176 as its boundary. In FIG. 2, the temperature region 174 is the hatched region. The control device 170 controls the temperature of the fuel cell stack 18 so that the temperature of the off-gas is below the dew-point temperature T corresponding to the amount of steam.

[0055] There is a correlation between the amount of water generated inside the fuel cell stack 18 and the amount of power generation. For this reason, in this embodiment, when obtaining the temperature upper limit value Tuplim, the control device 170 uses the power generation current of the fuel cell stack 18 instead of the amount of water.

[0056] If the amount of vapor in the off-gas is accurately known, the dew-point temperature T can be accurately determined. However, in this embodiment, the upper temperature limit Tuplim is estimated based on the current value. This estimation includes an error. Therefore, in order to reliably saturate the vapor in the off-gas, it is preferable to set the upper temperature limit Tuplim lower than the dew-point temperature T.

[0057] 3 is a flowchart showing the procedure of the humidification process. The control device 170 repeatedly executes the humidification process shown in FIG.

[0058] In step S1, the control device 170 calculates the upper temperature limit value Tuplim corresponding to the current value. For example, the control device 170 acquires the detection value of the current sensor 112. Furthermore, the control device 170 acquires the upper temperature limit value Tuplim corresponding to the detection value of the current sensor 112 using a first table stored in the storage device 172. Note that the control device 170 may calculate the upper temperature limit value Tuplim using a predetermined arithmetic expression instead of using the first table. After executing step S1, the process proceeds to step S2.

[0059] In step S2, the control device 170 acquires the stack temperature Ts. For example, the control device 170 acquires the detection value of the temperature sensor 76. The detection value of the temperature sensor 76 corresponds to the stack temperature Ts. In this embodiment, the temperature of the refrigerant flowing through the refrigerant discharge flow path 142 is detected as the stack temperature Ts. Alternatively, the temperature of the off-gas flowing through the oxidant gas discharge flow path 62 between the fuel cell stack 18 and the humidifier 30 may be detected as the stack temperature Ts. Alternatively, the temperature inside the fuel cell stack 18 may be directly detected as the stack temperature Ts. After step S2 is executed, the process proceeds to step S3.

[0060] In step S3, the control device 170 compares the upper temperature limit Tuplim acquired in step S1 with the stack temperature Ts acquired in step S2. If the stack temperature Ts is less than the upper temperature limit Tuplim (step S3: YES), the process proceeds to step S4. In this case, the steam in the off-gas discharged from the fuel cell stack 18 is saturated. On the other hand, if the stack temperature Ts is equal to or greater than the upper temperature limit Tuplim (step S3: NO), the process proceeds to step S7. In this case, the steam in the off-gas discharged from the fuel cell stack 18 is unsaturated.

[0061] When the process proceeds from step S3 to step S4, the control device 170 calculates the saturated vapor pressure. For example, the control device 170 obtains the saturated vapor pressure corresponding to the stack temperature Ts using a saturated vapor pressure curve stored in the storage device 172. After executing step S4, the process proceeds to step S5.

[0062] In step S5, the control device 170 estimates the humidification amount of the humidifier 30. The control device 170 uses a second table stored in the storage device 172 to obtain the humidification amount corresponding to the saturated vapor pressure obtained in step S4. Note that the control device 170 may calculate the humidification amount using a predetermined arithmetic expression instead of using the second table. After step S5 is executed, the process proceeds to step S6.

[0063] In step S6, the control device 170 controls the operation of the fuel cell stack 18 in accordance with the humidification amount of the humidifier 30. For example, if the humidification amount of the humidifier 30 is appropriate, the control device 170 may maintain the operation of the fuel cell stack 18. On the other hand, if the humidification amount of the humidifier 30 is insufficient, dry oxidant gas is supplied to the fuel cell stack 18. This may cause the electrolyte membrane 55 to dry out. The electrolyte membrane 55 deteriorates due to drying. If the humidification amount of the humidifier 30 is insufficient, the control device 170 controls the operation of the fuel cell stack 18 to suppress deterioration of the electrolyte membrane 55.

[0064] The control device 170 may cool the fuel cell stack 18 as the deterioration suppression control for the electrolyte membrane 55. As a specific example, the control device 170 may increase the flow rate of the coolant by increasing the rotational speed of the coolant pump 38. Alternatively, the control device 170 may increase the amount of coolant supplied to the radiator 40 by narrowing the opening of the coolant bypass valve 146. The control device 170 may reduce the amount of oxidant gas supplied to the fuel cell stack 18 as the deterioration suppression control for the electrolyte membrane 55. As a specific example, the control device 170 may reduce the discharge flow rate of the oxidant gas by the compressor 28. The control device 170 may reduce the power generation load of the fuel cell stack 18 as the deterioration suppression control for the electrolyte membrane 55. As a specific example, the control device 170 may limit the rotational speed of the motor 46. When step S6 is executed, the processing of this cycle ends.

[0065] When the process proceeds from step S3 to step S7, the control device 170 calculates a stack target temperature Tt such that the stack temperature Ts is less than the temperature upper limit value Tuplim. For example, the control device 170 may calculate the stack target temperature Tt by subtracting a predetermined temperature from the temperature upper limit value Tuplim acquired in step S1. Alternatively, the correspondence relationship between the temperature upper limit value Tuplim and the stack target temperature Tt may be determined in advance. After executing step S7, the process proceeds to step S8.

[0066] In step S8, the control device 170 controls the temperature of the fuel cell stack 18 based on the stack target temperature Tt. The control device 170 controls the coolant supply device 26 so that the stack temperature Ts is equal to or lower than the stack target temperature Tt. For example, the control device 170 may increase the flow rate of the coolant by increasing the rotation speed of the coolant pump 38. Alternatively, the control device 170 may increase the amount of coolant supplied to the radiator 40 by narrowing the opening of the coolant bypass valve 146. When step S8 is executed, the processing of this cycle ends.

[0067] [3 Inventions Obtained from the Embodiments] The invention that can be understood from the above embodiment will be described below.

[0068] A fuel cell system (12) according to an embodiment of the present invention comprises a fuel cell stack (18) that generates electricity using an oxidant gas and a fuel gas, a supply flow path (60) through which the oxidant gas supplied to the fuel cell stack flows, an exhaust flow path (62) through which oxidant off-gas discharged from the fuel cell stack flows, a humidifier (30) connected to the supply flow path and the exhaust flow path and that humidifies the fuel cell stack, a temperature adjustment device (26) that adjusts a stack temperature (Ts) that is the temperature of the fuel cell stack, a temperature acquisition device (76) that acquires the stack temperature, and a control device (170) that acquires the amount of humidification supplied to the fuel cell stack from the humidifier based on the stack temperature acquired by the temperature acquisition device and controls the stack temperature using the temperature adjustment device, and the control device controls the temperature adjustment device so that the vapor in the oxidant off-gas discharged from the fuel cell stack is saturated.

[0069] With the above configuration, since the steam in the off-gas discharged from the fuel cell stack is saturated, it is not necessary to consider changes in the humidification amount of the off-gas due to changes in the operating state of the fuel cell stack, etc., and it is possible to efficiently grasp the humidification amount supplied to the oxidant gas from the humidifier, thereby making it possible to appropriately adjust the humidification amount supplied to the oxidant gas from the humidifier.

[0070] In an aspect of the present invention, the temperature acquisition device may acquire the temperature at an outlet (102) of the fuel cell stack located upstream of the humidifier in the exhaust flow path.

[0071] According to the above configuration, the humidification state inside the fuel cell stack can be properly grasped.

[0072] In an aspect of the present invention, the control device may set the temperature at which the vapor in the oxidant off-gas becomes saturated at the outlet of the fuel cell stack as a stack target temperature (Tt) based on the power generation state of the fuel cell stack, and the temperature adjustment device may adjust the stack temperature to be equal to or lower than the stack target temperature.

[0073] According to the above configuration, the off-gas can be controlled to be in an appropriate humidified state.

[0074] In one aspect of the present invention, the control device may set the temperature at which the vapor in the oxidant off-gas becomes saturated at the outlet of the fuel cell stack and condensation occurs within the fuel cell stack or in the exhaust flow path as the stack target temperature based on the power generation state of the fuel cell stack, and the temperature adjustment device may adjust the stack temperature to be below the stack target temperature.

[0075] According to the above configuration, since the off-gas is condensed, the vapor in the off-gas can be saturated even if there is variation in the power generation state of the fuel cell stack or the amount of humidification by the humidifier, and therefore the above configuration contributes to improving robustness against control variation.

[0076] In an aspect of the present invention, when the stack temperature acquired by the temperature acquisition device is lower than the stack target temperature, the control device may calculate a saturated vapor pressure based on the stack temperature, and acquire the humidification amount to be supplied from the humidifier to the fuel cell stack based on the saturated vapor pressure.

[0077] With this configuration, the fuel cell stack can be kept in a saturated vapor state at all times. As a result, the vapor of the off-gas discharged from the cathode flow path inside the fuel cell stack is saturated, and the amount of humidification by the humidifier can be easily determined. [Explanation of symbols]

[0078] 12...Fuel cell system 18...Fuel cell stack 26... Refrigerant supply device (temperature adjustment device) 30... Humidifier (humidifying device) 60...oxidant gas supply channel (supply channel) 62...oxidant gas discharge flow path (discharge flow path) 76...Temperature sensor (temperature acquisition device) 102...oxidizer gas outlet communication port (outlet) 170...control device

Claims

1. a fuel cell stack that generates electricity using an oxidant gas and a fuel gas; a supply flow path through which the oxidant gas supplied to the fuel cell stack flows; an exhaust flow path through which oxidant off-gas discharged from the fuel cell stack flows; a humidifying device connected to the supply flow path and the discharge flow path, for humidifying the fuel cell stack; a temperature adjustment device that adjusts a stack temperature, which is the temperature of the fuel cell stack; a control device that determines whether the vapor in the oxidant off-gas discharged from the fuel cell stack is saturated, and if the vapor in the oxidant off-gas is not saturated, controls the stack temperature by controlling the temperature adjustment device so that the vapor in the oxidant off-gas becomes saturated, and if the vapor in the oxidant off-gas becomes saturated, performs control according to an estimated value of the humidification amount supplied from the humidifier to the fuel cell stack; Equipped with Fuel cell system.

2. 2. The fuel cell system according to claim 1, the control device sets a temperature at which the vapor in the oxidant off-gas becomes saturated at an outlet of the fuel cell stack as a stack target temperature based on a power generation state of the fuel cell stack; The temperature adjustment device adjusts the stack temperature to be equal to or lower than the stack target temperature. Fuel cell system.

3. 2. The fuel cell system according to claim 1, the control device sets, based on a power generation state of the fuel cell stack, a temperature at which the vapor in the oxidant off-gas becomes saturated at an outlet of the fuel cell stack and condensation occurs within the fuel cell stack or in the exhaust flow path, as a stack target temperature; The temperature adjustment device adjusts the stack temperature to be equal to or lower than the stack target temperature. Fuel cell system.

4. 4. The fuel cell system according to claim 2 or 3, a temperature acquisition device for acquiring the stack temperature, When the stack temperature acquired by the temperature acquisition device is equal to or lower than the stack target temperature, the control device calculates a saturated vapor pressure corresponding to the stack temperature based on a saturated vapor pressure curve, and uses the calculated saturated vapor pressure when estimating the amount of humidification to be supplied from the humidifier to the fuel cell stack. Fuel cell system.

5. 5. The fuel cell system according to claim 4, the temperature acquisition device acquires the temperature of an outlet of the fuel cell stack located upstream of the humidifier in the exhaust flow path. Fuel cell system.

6. The fuel cell system according to any one of claims 1 to 5, When the vapor in the oxidant off-gas is saturated, the control device acquires a saturated vapor pressure corresponding to the stack temperature, acquires a humidification amount corresponding to the acquired saturated vapor pressure, and performs at least one of controlling the temperature adjustment device, controlling a compressor for supplying the oxidant gas to the fuel cell stack, and suppressing a power generation load of the fuel cell system according to the acquired humidification amount. Fuel cell system.

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