JP2024037203A - fuel cell unit - Google Patents

Abstract

To stabilize a power generation of a fuel cell stack under an environment where an oxygen concentration of an air supplied to the fuel cell stack is easily deteriorated.SOLUTION: A fuel cell unit FCU is configured to comprise: an air compressor ACP that supplies an air in the fuel cell unit FCU to a fuel cell stack FCS; a fun F; an oxygen concentration detection part OCD that detects the oxygen concentration of a suction air of the fuel cell unit FCU; and a control part CNT. In the case where an oxygen stoichiometric which is obtained by multiplying air stoichiometry and a value obtained by dividing the oxygen concentration detected by the oxygen concentration detection part OCD with a standard oxygen concentration is smaller than a target oxygen stoichiometric, the control part CNT executes at least one of processing for increasing a flow amount of the air supplied to the fuel cell stack FCS by controlling an operation of the air compressor ACP, and processing for performing ventilation in the fuel cell unit FCU by controlling the operation of the fun F.SELECTED DRAWING: Figure 1

Description

The present invention relates to a fuel cell unit including a fuel cell stack.

Some fuel cell units are installed in vehicles and generators.

By the way, if the air supply port is not provided at the front of the vehicle, if the vehicle speed is relatively slow, or if the fuel cell unit is installed in a stationary generator, the wind from the vehicle will not enter the vehicle or generator. Therefore, outside air cannot be actively taken into the fuel cell unit, and the oxygen concentration of the air within the fuel cell unit may decrease, leading to a risk that the voltage of the fuel cell stack may decrease.

In addition, if air whose oxygen concentration has decreased due to power generation is not discharged from the fuel cell stack to the outside of the fuel cell unit but is discharged into the fuel cell unit, that air is again supplied from the air compressor to the fuel cell stack and fuel There is a risk that the voltage of the battery stack will drop.

Therefore, one idea is to supply air to the fuel cell stack so that the flow rate of air supplied to the fuel cell stack matches the target flow rate calculated using the oxygen concentration of the air inside the fuel cell unit. It will be done. A related technique is Patent Document 1.

Japanese Patent Application Publication No. 2004-273162

An object of one aspect of the present invention is to stabilize power generation of a fuel cell stack in an environment where the oxygen concentration of air supplied to the fuel cell stack tends to decrease.

A fuel cell unit according to one embodiment of the present invention includes a fuel cell stack, an air compressor that supplies air within the fuel cell unit to the fuel cell stack, and a ventilation section that ventilates the inside of the fuel cell unit. The fuel cell unit includes an oxygen concentration detection section that detects the oxygen concentration of intake air of the fuel cell unit, and a control section that controls operations of the air compressor and the ventilation section.

When the oxygen stoichiometric value, which is a value obtained by multiplying the air stoichiometric of the fuel cell stack by the value obtained by dividing the oxygen concentration detected by the oxygen concentration detection unit by the standard oxygen concentration, is smaller than the target oxygen stoichiometric, At least one of a process of increasing the flow rate of air supplied to the fuel cell stack by controlling the operation of the air compressor, and a process of ventilating the inside of the fuel cell unit by controlling the operation of the ventilation section. Execute one process.

As a result, when the oxygen stoichiometric value is smaller than the target oxygen stoichiometric value, at least one of the following processes can be performed: increasing the flow rate of air supplied to the fuel cell stack, and ventilating the inside of the fuel cell unit. , it is possible to increase the oxygen concentration of the air supplied to the fuel cell stack, and it is possible to suppress a drop in the voltage of the fuel cell stack.

The control unit also controls the flow rate of air supplied to the fuel cell stack, which is necessary to increase the oxygen stoichiometric to the target oxygen stoichiometric when the oxygen stoichiometric is smaller than the target oxygen stoichiometric. may be configured to perform a process of increasing the flow rate of air when the flow rate of air supplied to the fuel cell stack is less than or equal to an upper limit of an allowable range of the flow rate of air.

As a result, when the oxygen stoichiometric value is smaller than the target oxygen stoichiometric value, and the flow rate of air supplied to the fuel cell stack, which is necessary to increase the oxygen stoichiometric value to the target oxygen stoichiometric value, is greater than the upper limit value, the fuel Since the flow rate of air supplied to the cell stack can be prevented from increasing, the load on the air compressor can be reduced, and drying inside the fuel cell stack can be suppressed.

Further, the ventilation section may be a fan that increases the heat radiation amount of a radiator that exchanges heat with air between a refrigerant warmed by heat generated by the fuel cell stack.

As a result, if the fuel cell unit is already equipped with a fan that increases the amount of heat dissipated from the radiator, that fan can be used as a ventilation section, making it possible to suppress an increase in the manufacturing cost of the fuel cell unit. .

Further, the fuel cell unit includes a notification section, and the control section is configured to control the case where the oxygen concentration detected by the oxygen concentration detection section is lower than a predetermined concentration after performing a process of ventilating the inside of the fuel cell unit. The fuel cell unit may be configured such that the notification section notifies the outside of the fuel cell unit that the oxygen concentration of the air outside the fuel cell unit is decreasing.

This makes it possible to notify the outside of the fuel cell unit when the oxygen concentration in the air surrounding the fuel cell unit is decreasing, so it is possible to notify the outside of the fuel cell unit when the oxygen concentration in the air around the fuel cell unit is decreasing. It is possible to notify a user that the oxygen concentration of the air around the fuel cell unit is decreasing.

In addition, since the configuration determines whether the oxygen concentration is lower than a predetermined concentration after executing the process of ventilating the inside of the fuel cell unit, the oxygen concentration may be affected by the noise contained in the oxygen concentration detected by the oxygen concentration detection section. It is possible to prevent the concentration from being erroneously determined to be lower than the predetermined concentration, and it is possible to prevent erroneous notification from being sent outside the fuel cell unit.

According to the present invention, the power generation of the fuel cell stack can be stabilized in an environment where the oxygen concentration of the air supplied to the fuel cell stack is relatively low.

It is a figure showing an example of application of a fuel cell unit of an embodiment. FIG. 7 is a diagram showing another application example of the fuel cell unit of the embodiment. 5 is a flowchart illustrating an example of the operation of a control unit in Example 1. FIG. 7 is a flowchart illustrating an example of the operation of a control unit in Example 2. FIG.

Embodiments will be described in detail below based on the drawings.

FIG. 1 is a diagram showing an example of application of the fuel cell unit of the embodiment.

In the application example of the fuel cell unit shown in FIG. 1, the fuel cell unit FCU is provided in the vehicle Ve. For example, the vehicle Ve is an industrial vehicle such as a forklift. Further, it is assumed that the vehicle Ve is equipped with a load Lo such as an inverter that drives a driving motor, and electric power is supplied to the load Lo from the fuel cell unit FCU. Furthermore, since the vehicle Ve is not provided with an air supply port (not shown) at the front of the vehicle Ve, or even if the air supply port is provided at the front of the vehicle Ve, the running speed of the vehicle Ve is relatively low. Because of the slow speed, it is assumed that it is difficult to ventilate the inside of the fuel cell unit FCU due to the running wind.

Moreover, FIG. 2 is a diagram showing another application example of the fuel cell unit of the embodiment. Note that the fuel cell unit FCU shown in FIG. 2 is similar to the fuel cell unit FCU shown in FIG. 1.

In the application example of the fuel cell unit FCU shown in FIG. 2, the fuel cell unit FCU is provided in a stationary generator Sg. For example, the fuel cell unit FCU supplies power to a load Lo provided outside the stationary generator Sg in cooperation with a commercial power source, a solar power generator, or the like. Furthermore, since the stationary generator Sg is installed at a fixed location and does not move from that location, it is difficult to ventilate the inside of the fuel cell unit FCU due to the wind while the generator is running. Furthermore, if the stationary generator Sg is installed in a building with few windows or in a room without a ventilation system, it will be even more difficult to ventilate the fuel cell unit FCU.

That is, it is assumed that the fuel cell unit FCU shown in FIG. 1 or 2 is in an environment where the oxygen concentration of the air supplied to the fuel cell stack FCS is relatively low.

The fuel cell unit FCU shown in FIG. 1 or 2 also includes a fuel cell stack FCS, a fuel tank Tk, a main stop valve SV, an injector INJ, a gas-liquid separator GLS, a hydrogen circulation pump HP, and an exhaust gas. It includes a drain valve EDV, a diluter DIL, an air compressor ACP, an air pressure regulating valve ARV, and an air shut valve ASV.

The fuel cell unit FCU shown in FIG. 1 or 2 also includes a radiator R, a fan F (ventilation section), a water pump WP, an intercooler IC, a DC/DC converter CNV, a power storage device B, and a voltage sensor Svb. , a current sensor Sib, a voltage sensor Svf, a current sensor Sif, an oxygen concentration detection section OCD, a storage section STR, and a control section CNT.

A fuel cell stack FCS is a fuel cell configured by stacking a plurality of fuel cells, and generates electricity through an electrochemical reaction between hydrogen contained in hydrogen gas and oxygen contained in air. In general, the voltage of a fuel cell is a voltage obtained by subtracting three types of overvoltage: resistance overvoltage, activation overvoltage, and concentration overvoltage from the theoretical electromotive force. Therefore, if at least one of the resistance overvoltage, activation overvoltage, and concentration overvoltage increases, the voltage of the fuel cell stack FCS will decrease. Note that the resistance overvoltage is a voltage resulting from the difficulty of moving electrons and platons within the fuel cell. The activation overvoltage is a voltage derived from the difficulty of hydrogen oxidation reaction at the anode of the fuel cell and oxygen reduction reaction at the cathode of the fuel cell. The concentration overvoltage is a voltage resulting from the difficulty of diffusion of hydrogen gas and air within the fuel cell.

The fuel tank Tk is a storage container for hydrogen gas. Hydrogen gas stored in the fuel tank Tk is supplied to the fuel cell stack FCS via the main stop valve SV and the injector INJ.

The main stop valve SV is composed of a solenoid valve or the like, and supplies hydrogen gas to the injector INJ. Moreover, the main stop valve SV cuts off the supply of hydrogen gas to the injector INJ under the operation control of the control unit CNT.

The injector INJ adjusts the flow rate of hydrogen gas so that the pressure of the hydrogen gas supplied to the fuel cell stack FCS is constant. Note that when the fuel cell unit FCU is included in the vehicle Ve, the fuel tank Tk, the main stop valve SV, and the injector INJ are provided inside the vehicle Ve. When the fuel cell unit FCU is included in the stationary generator Sg, the fuel tank Tk, main stop valve SV, and injector INJ are provided outside the stationary generator Sg.

The gas-liquid separator GLS separates hydrogen gas and liquid water discharged from the fuel cell stack FCS.

The hydrogen circulation pump HP resupplies the hydrogen gas separated by the gas-liquid separator GLS to the fuel cell stack FCS.

The exhaust drain valve EDV sends the liquid water separated by the gas-liquid separator GLS to the diluter DIL. The liquid water sent to the diluter DIL accumulates in a tank (not shown) within the diluter DIL. In addition, the air discharged from the fuel cell stack FCS via the air pressure regulating valve ARV joins the hydrogen gas discharged from the exhaust drain valve EDV at the diluter DIL, and the air is transferred from the diluter DIL into the fuel cell unit FCU. is discharged. In this way, the air discharged from the diluter DIL has oxygen consumed by the power generation of the fuel cell stack FCS, so compared to the air outside the fuel cell unit FCU (vehicle Ve and stationary generator Sg). , it is assumed that the oxygen concentration is decreasing.

Air compressor ACP compresses air within fuel cell unit FCU and supplies the compressed air to fuel cell stack FCS via intercooler IC and air shut valve ASV. It is assumed that as the load on the air compressor ACP (the number of rotations of the motor) increases, the flow rate of air supplied from the air compressor ACP to the fuel cell stack FCS increases.

The intercooler IC exchanges heat with air heated to high temperature by compression by the air compressor ACP with a refrigerant such as cooling water flowing through the intercooler IC.

The air shut valve ASV shuts off the supply of air to the fuel cell stack FCS under the operation control of the control unit CNT.

The air pressure regulating valve ARV regulates the pressure of air supplied to the fuel cell stack FCS under the operation control of the control unit CNT.

The radiator R exchanges heat with the refrigerant warmed by the heat generated by the fuel cell stack FCS with the air inside the fuel cell unit FCU.

The fan F increases the amount of heat dissipated from the radiator R. That is, the air generated by the fan F being driven hits the radiator R, thereby lowering the temperature of the radiator R. Further, the fan F is a ventilation section that takes air outside the fuel cell unit FCU into the fuel cell unit FCU and exhausts air inside the fuel cell unit FCU to the outside of the fuel cell unit FCU. Functions as a ventilation section to ventilate the air. Note that the ventilation section is not limited to the fan F, and may also employ a fan (not shown) for cooling auxiliary equipment such as the power storage device B. When fan F is used as the ventilation section, there is no need to newly provide a ventilation section in the fuel cell unit FCU, and fan F can be used as the ventilation section, thereby suppressing an increase in the manufacturing cost of the fuel cell unit FCU. can do.

Water pump WP supplies refrigerant cooled by radiator R to fuel cell stack FCS via intercooler IC.

The DCDC converter CNV is connected to the latter stage of the fuel cell stack FCS, and converts the voltage output from the fuel cell stack FCS into a predetermined voltage. Further, the electric power output from the DCDC converter CNV is supplied to the load Lo and auxiliary machines such as the hydrogen circulation pump HP, the air compressor ACP, and the water pump WP.

Power storage device B is configured with a lithium ion capacitor or the like, and is connected between DCDC converter CNV and load Lo.

If the supplied power corresponding to the difference between the power output from the DC-DC converter CNV and the total value of the power supplied to the auxiliary equipment is greater than the required power requested from the load Lo, the required power of the supplied power The electric power corresponding to is supplied to the load Lo, and the remaining electric power is supplied to the power storage device B. When power is supplied from the DC/DC converter CNV to the power storage device B, the power storage device B is charged and the charge amount Ch of the power storage device B increases. In addition, if the supplied power corresponding to the difference between the power output from the DCDC converter CNV and the total value of the power supplied to the auxiliary equipment is smaller than the required power requested from the load Lo, the supplied power is At the same time, the insufficient power is supplied from power storage device B to load Lo. When power is supplied from power storage device B to load Lo, power storage device B is discharged and the amount of charge Ch of power storage device B decreases. Note that the charge amount Ch is the charging rate [%] of the power storage device B (the ratio of the remaining capacity to the fully charged capacity of the power storage device B), or the voltage of the power storage device B when no current is flowing through the power storage device B. Vb [V], voltage Vb [V] of power storage device B when current is flowing through power storage device B, or integrated value [Ah] of current Ib flowing through power storage device B, or the like.

Voltage sensor Svb is configured with a plurality of voltage dividing resistors and the like, detects voltage Vb of power storage device B, and sends the detected voltage Vb to control unit CNT.

Current sensor Sib is configured with a shunt resistor, a Hall element, etc., detects current Ib flowing through power storage device B, and sends the detected current Ib to control unit CNT.

The voltage sensor Svf is constituted by a plurality of voltage dividing resistors, etc., detects the voltage Vf of the entire fuel cell stack FCS, and sends the detected voltage Vf to the control unit CNT.

The current sensor Sif is composed of a shunt resistor, a Hall element, etc., detects the current If flowing from the fuel cell stack FCS to the DCDC converter CNV, and sends the detected current If to the control unit CNT.

The oxygen concentration detection unit OCD is, for example, an oxygen concentration meter, detects the oxygen concentration OC of the intake air of the fuel cell unit FCU, and sends the detected oxygen concentration OC to the control unit CNT.

The storage unit STR is composed of RAM (Random Access Memory), ROM (Read Only Memory), and the like. Note that the storage unit STR stores a target oxygen stoichiometric value, an upper limit value, etc., which will be described later.

The control unit CNT is constituted by a microcomputer or the like, and changes the target generated power Pt in stages according to the charge amount Ch of the power storage device B when controlling the power generation of the fuel cell stack FCS.

Furthermore, when controlling the power generation of the fuel cell stack FCS, the control unit CNT controls the operation of the auxiliary equipment so that the generated power P (the product of the current If and the voltage Vf) of the fuel cell stack FCS follows the target generated power Pt. Control. For example, when the fuel cell stack FCS is generating power, the control unit CNT uses PI (Proportional-Integral) control so that the difference between the generated power P of the fuel cell stack FCS and the target generated power Pt becomes zero. Controls the operation of auxiliary equipment.

Further, the control unit CNT executes the oxygen stoichiometric reduction avoidance process at regular intervals. For example, when executing the oxygen stoichiometric reduction avoidance process, if the oxygen stoichiometric is smaller than the target oxygen stoichiometric, the control unit CNT increases the flow rate of air supplied to the fuel cell stack FCS by controlling the operation of the air compressor ACP. At least one of the process of ventilating the inside of the fuel cell unit FCU by controlling the operation of the fan F is executed. When the oxygen concentration OC of the air in the fuel cell unit FCU is equal to or approximately equal to the standard oxygen concentration OCs, increasing the flow rate of the air supplied to the fuel cell stack FCS increases the amount of air supplied to the fuel cell stack FCS. It is assumed that the oxygen concentration increases and the oxygen stoichiometry increases. In addition, when the oxygen concentration of the air outside the fuel cell unit FCU (vehicle Ve or stationary generator Sg) is equal or approximately equal to the standard oxygen concentration OCs, if the inside of the fuel cell unit FCU is ventilated, the fuel cell stack FCS Assume that the oxygen concentration of the air supplied to the tank increases, and the oxygen stoichiometric value increases. Note that the target oxygen stoichiometric value is a value that varies depending on the characteristics of the fuel cell, and is, for example, 1.0 to 1.3. Further, the target oxygen stoichiometric value is the oxygen stoichiometric value calculated using the oxygen concentration OC detected by the oxygen concentration detection unit OCD when the generated power P of the fuel cell stack FCS becomes equal to the target generated power Pt.

For example, the control unit CNT sets the oxygen stoichiometric value to a value obtained by multiplying the air stoichiometric value of the fuel cell stack FCS by the value obtained by dividing the oxygen concentration OC detected by the oxygen concentration detection unit OCD by the standard oxygen concentration OCs. That is, the control unit CNT sets the result of calculating the following equation 1 as the oxygen stoichiometric value. It is assumed that the air stoichiometry and standard oxygen concentration OCs are stored in advance in the storage section STR. In addition, air stoichiometry refers to the flow rate of air supplied from the air compressor ACP to the fuel cell stack FCS when the generated power P of the fuel cell stack FCS becomes equal to the target generated power Pt. It is a percentage of the actual flow rate of air supplied. Further, the standard oxygen concentration OCs is defined as the oxygen concentration OC detected by the oxygen concentration detection unit OCD when the fuel cell stack FCS is sufficiently ventilated. In addition, the oxygen stoichiometry is an index of the oxygen concentration of the air supplied to the fuel cell stack FCS.

Oxygen stoichiometric = Air stoichiometric x Oxygen concentration OC ÷ Standard oxygen concentration OCs ... Formula 1

<Example 1>
FIG. 3 is a flowchart showing an example of the operation of the control unit CNT in the first embodiment.

First, when the control unit CNT starts the oxygen stoichiometric reduction avoidance process, it acquires the oxygen concentration OC detected by the oxygen concentration detection unit OCD (step S1), and uses the oxygen concentration OC acquired in step S1 to control the oxygen stoichiometric reduction. Calculate (step S2).

Next, if the oxygen stoichiometric calculated in step S2 is equal to or higher than the target oxygen stoichiometric (step S3: No), the control unit CNT ends the current oxygen stoichiometric reduction avoidance process.

On the other hand, if the oxygen stoichiometric calculated in step S2 is smaller than the target oxygen stoichiometric (step S3: Yes), the control unit CNT calculates the required air flow rate (step S4). Note that the required air flow rate is the flow rate of air supplied to the fuel cell stack FCS, which is necessary to increase the oxygen stoichiometric value to the target oxygen stoichiometric value. For example, if the air stoichiometric value is 1.5, the target oxygen stoichiometric value is 1.2, the oxygen concentration OC detected by the oxygen concentration detection unit OCD is 13 [%], and the standard oxygen concentration OCs is 21 [%], then the air stoichiometric value is 1 and the flow rate of air supplied to the fuel cell stack FCS is 100 [NL/min], the control unit CNT first calculates 1.5 × 13 [%] ÷ 21 [%]. By doing this, we calculate 0.92 as the oxygen stoichiometric value, then calculate 1.95 as the new air stoichiometric value by calculating 1.5 x 1.2 ÷ 0.92, and then calculate 1.95 x 100[ NL/min], 195 [NL/min] is calculated as the required air flow rate.

Further, if the required air flow rate calculated in step S4 is less than or equal to the upper limit of the allowable range of air flow rate supplied to the fuel cell stack FCS (step S5: Yes), the control unit CNT operates the air compressor ACP. The flow rate of air supplied to the fuel cell stack FCS is increased by controlling (step S6), and the process proceeds to step S8. For example, the control unit CNT controls the operation of the air compressor ACP so that the flow rate of air supplied to the fuel cell stack FCS approaches the required air flow rate calculated in step S4. In this way, by increasing the flow rate of air supplied to the fuel cell stack FCS, the air stoichiometric capacity increases, and therefore, an increase in the oxygen stoichiometric capacity can be expected. Note that the upper limit value is a value that can be determined in advance by conducting experiments, simulations, etc. using the noise level of the air compressor ACP and the degree of dryness of the air flow path in the fuel cell stack FCS.

On the other hand, if the required air flow rate calculated in step S4 is larger than the upper limit value (step S5: No), the control unit CNT does not change the flow rate of air supplied to the fuel cell stack FCS (step S7), and in step S8 Proceed to processing.

Next, in step S8, the control unit CNT acquires the oxygen concentration OC detected by the oxygen concentration detection unit OCD, and calculates the oxygen stoichiometric value using the oxygen concentration OC acquired in step S8 (step S9).

Next, if the oxygen stoichiometric calculated in step S9 is equal to or higher than the target oxygen stoichiometric (step S10: No), the control unit CNT ends the current oxygen stoichiometric reduction avoidance process.

On the other hand, if the oxygen stoichiometric calculated in step S9 is smaller than the target oxygen stoichiometric (step S10: Yes), the control unit CNT ventilates the inside of the fuel cell unit by controlling the operation of the fan F (step S11). The oxygen stoichiometric reduction avoidance process ends. In addition, in step S11, when the fan F is already driven, the control unit CNT may be configured to increase the rotation speed of the fan F as the difference between the target oxygen stoichiometric and the oxygen stoichiometric becomes larger. In this way, by controlling the operation of the fan F to ventilate the inside of the fuel cell unit FCU, the air outside the fuel cell unit FCU is taken into the fuel cell unit FCU, and the air inside the fuel cell unit FCU is used as fuel. Since it can be discharged outside the battery unit FCU, the oxygen concentration of the air taken into the air compressor ACP can be increased, and the oxygen concentration of the air supplied to the fuel cell stack FCS can be increased. An increase in oxygen stoichiometry can be expected.

According to the first embodiment, the oxygen stoichiometric reduction avoidance process is repeatedly executed at regular intervals, thereby making it possible to bring the oxygen stoichiometric value closer to the target oxygen stoichiometric value.

Further, according to the first embodiment, when the oxygen stoichiometric value is smaller than the target oxygen stoichiometric value and the required air flow rate is greater than the upper limit value, the flow rate of air supplied to the fuel cell stack FCS is not increased. Therefore, the load on the air compressor ACP can be reduced, and drying inside the fuel cell stack FCS can be suppressed.

<Example 2>
FIG. 4 is a flowchart showing an example of the operation of the control unit CNT in the second embodiment. Note that steps S1 to S11 in the flowchart shown in FIG. 4 are the same as steps S1 to S11 in the flowchart shown in FIG. 3, so their explanation will be omitted. Further, in the second embodiment, it is assumed that the fuel cell unit FCU shown in FIG. 1 or 2 is equipped with a notification section (not shown) including a warning light, a buzzer, and the like.

In step S11, the control unit CNT ventilates the inside of the fuel cell unit FCU, and then acquires the oxygen concentration OC detected by the oxygen concentration detection unit OCD (step S12), and uses the oxygen concentration OC acquired in step S12. The oxygen concentration is compared with a predetermined oxygen concentration threshold (step S13). The threshold value is a predetermined concentration used to issue a warning.

Next, when the oxygen concentration OC acquired in step S12 is equal to or higher than the threshold value (step S13: No), the control unit CNT ends the current oxygen stoichiometric drop avoidance process.

On the other hand, if the oxygen concentration OC acquired in step S12 is smaller than the threshold value (step S13: Yes), the control unit CNT informs that the oxygen concentration of the air outside the fuel cell unit FCU is lower than at least the standard oxygen concentration. The notification unit notifies the outside of the fuel cell unit FCU (vehicle Ve and stationary generator Sg) (step S14), and the current oxygen stoichiometric reduction avoidance process is ended.

As described above, according to the second embodiment, the oxygen concentration OC does not exceed the threshold value even though the flow rate of air supplied to the fuel cell stack FCS is increased or the inside of the fuel cell unit FCU is ventilated. In this case, since the configuration is configured to notify the outside of the fuel cell unit FCU that the oxygen concentration of the air outside the fuel cell unit FCU is decreasing, the vehicle near the vehicle Ve equipped with the fuel cell unit FCU or the stationary generator Sg It is possible to notify a user in the room that the oxygen concentration of the air around the fuel cell unit FCU is decreasing.

Further, according to the second embodiment, since the configuration is such that it is determined whether the oxygen concentration OC obtained after executing the process of ventilating the inside of the fuel cell unit FCU is smaller than the threshold value, the oxygen concentration detection unit OCD detects the oxygen concentration OC. It is possible to suppress erroneously determining that the oxygen concentration OC is smaller than a threshold value due to the influence of noise contained in the oxygen concentration OC, and to suppress erroneous notification from being sent outside the fuel cell unit FCU. Can be done.

Further, in the flowchart shown in FIG. 3 or 4, when the oxygen stoichiometric value is smaller than the target oxygen stoichiometric value, the flow rate of air supplied to the fuel cell stack FCS is increased, and then the inside of the fuel cell unit FCU is ventilated. However, after the inside of the fuel cell unit FCU is ventilated, the flow rate of air supplied to the fuel cell stack FCS may be increased. That is, the configuration may be such that steps S1 to S7 are executed after steps S8 to S11 are executed. The priority order of the process of increasing the flow rate of air supplied to the fuel cell stack FCS and the process of ventilating the inside of the fuel cell unit FCU is from the start of control of the air compressor ACP or fan F by the control unit CNT to It may be determined based on the time required to start the operation of the ACP or the fan F or the amount of increase per unit time in the oxygen stoichiometry accompanying the operation of the air compressor ACP or the fan F. For example, if the time required from the start of control of the air compressor ACP by the control unit CNT to the start of operation of the air compressor ACP is shorter than the time required from the start of control of the fan F by the control unit CNT to the start of operation of the fan F, the fuel cell The process of increasing the flow rate of air supplied to the stack FCS is given priority over the process of ventilating the inside of the fuel cell unit FCU. In addition, if the amount of increase per unit time in the oxygen stoichiometry due to the operation of fan F is larger than the amount of increase per unit time in the oxygen stoichiometry due to the operation of air compressor ACP, the process of ventilating the inside of the fuel cell unit FCU is performed. Priority is given to processing that increases the flow rate of air supplied to the fuel cell stack FCS.

In addition, in the flowchart shown in FIG. 3 or 4, when the oxygen stoichiometric state continues to be smaller than the target oxygen stoichiometric state, a process is performed to increase the flow rate of air supplied to the fuel cell stack FCS, and to increase the flow rate inside the fuel cell unit FCU. The configuration executes two processes: ventilation process, but if the oxygen stoichiometry is smaller than the target oxygen stoichiometry, a process to increase the flow rate of air supplied to the fuel cell stack FCS, and a process to ventilate the inside of the fuel cell unit FCU. The configuration may be such that one of two processes is executed.

By the way, if the fuel cell unit FCU is provided in a vehicle Ve that does not have an air supply port on the front or a vehicle Ve that travels at a relatively slow speed, or if the fuel cell unit FCU is provided in a stationary generator Sg. In this case, outside air cannot be actively taken into the fuel cell unit FCU, and the oxygen concentration of the air supplied from the air compressor ACP to the fuel cell stack FCS becomes relatively low, resulting in an increase in concentration overvoltage. There is a possibility that the voltage Vf of the fuel cell stack FCS will decrease.

Additionally, if the temperature of the refrigerant passing through the radiator R is relatively low and there is no need to drive the fan F, outside air cannot be actively taken into the fuel cell unit FCU, and is supplied from the air compressor ACP to the fuel cell stack FCS. Since the oxygen concentration of the air is relatively low, the concentration overvoltage may increase and the voltage Vf of the fuel cell stack FCS may decrease.

Further, when the power required from the load Lo to the fuel cell unit FCU is relatively large, there is a possibility that the concentration overvoltage increases and the voltage Vf of the fuel cell stack FCS decreases.

Generally, the oxygen concentration in the atmosphere (the oxygen concentration in the air outside the vehicle Ve and the oxygen concentration in the air outside the building covering the stationary generator Sg) is about 21%, but the fuel cell stack FCS Since the oxygen contained in the air inside the fuel cell stack is consumed during power generation, the oxygen concentration of the air discharged from the fuel cell stack FCS is lower than the oxygen concentration in the atmosphere. Therefore, when the air compressor ACP sucks the air discharged from the fuel cell stack FCS, the oxygen concentration of the air supplied from the air compressor ACP to the fuel cell stack FCS becomes relatively low, so the concentration overvoltage increases and the fuel cell There is a possibility that the voltage Vf of the stack FCS will decrease.

When these conditions overlap, the possibility that the voltage Vf of the fuel cell stack FCS will decrease further increases.

Therefore, in the fuel cell unit FCU of the embodiment, when the oxygen stoichiometric value, which is an index of the oxygen concentration of the air supplied to the fuel cell stack FCS, is smaller than the target oxygen stoichiometric value, the fuel cell stack FCS is supplied from the air compressor ACP to the fuel cell stack FCS. This configuration executes at least one of a process of increasing the flow rate of air and a process of ventilating the inside of the fuel cell unit FCU. When the process of increasing the flow rate of air supplied to the fuel cell stack FCS or the process of ventilating the inside of the fuel cell unit FCU is executed, the oxygen concentration of the air supplied to the fuel cell stack FCS can be increased. can. Thereby, when the oxygen stoichiometric value is smaller than the target oxygen stoichiometric value, the oxygen concentration of the air supplied to the fuel cell stack can be increased, and the voltage of the fuel cell stack can be prevented from decreasing. That is, according to the fuel cell unit FCU of the embodiment, the power generation of the fuel cell stack FCS can be stabilized in an environment where the oxygen concentration of the air supplied to the fuel cell stack FCS tends to decrease.

Note that the present invention is not limited to the above-described embodiments, and various improvements and changes can be made without departing from the gist of the present invention.

FCU Fuel cell unit STR Storage unit CNT Control unit Ve Vehicle Lo Load Sg Stationary generator FCS Fuel cell stack Tk Fuel tank SV Main stop valve INJ Injector GLS Gas-liquid separator HP Circulation pump EDV Exhaust drain valve DIL Diluter ACP Air compressor ARV Air pressure regulating valve ASV Air shutoff valve R Radiator F Fan WP Water pump IC Intercooler CNV DCDC converter B Power storage device Svf Voltage sensor Sif Current sensor Svb Voltage sensor Sib Current sensor OCD Oxygen concentration detection section

Claims (4)

In the fuel cell unit,
fuel cell stack,
an air compressor that supplies air within the fuel cell unit to the fuel cell stack;
a ventilation section that ventilates the interior of the fuel cell unit;
an oxygen concentration detection section that detects the oxygen concentration of intake air of the fuel cell unit;
a control unit that controls operations of the air compressor and the ventilation unit;
Equipped with
When the oxygen stoichiometric value, which is a value obtained by multiplying the air stoichiometric of the fuel cell stack by the value obtained by dividing the oxygen concentration detected by the oxygen concentration detection unit by the standard oxygen concentration, is smaller than the target oxygen stoichiometric, At least one of a process of increasing the flow rate of air supplied to the fuel cell stack by controlling the operation of the air compressor, and a process of ventilating the inside of the fuel cell unit by controlling the operation of the ventilation section. A fuel cell unit characterized by executing one process. The fuel cell unit according to claim 1,
The control unit controls, when the oxygen stoichiometric is smaller than the target oxygen stoichiometric, the flow rate of air supplied to the fuel cell stack required to increase the oxygen stoichiometric to the target oxygen stoichiometric; A fuel cell unit characterized in that, when the flow rate of air supplied to the fuel cell stack is below an upper limit value of an allowable range, a process of increasing the flow rate of the air is executed. The fuel cell unit according to claim 1,
The fuel cell unit is characterized in that the ventilation section is a fan that increases the heat radiation amount of a radiator that exchanges heat with air between the refrigerant warmed by the heat generated by the fuel cell stack. The fuel cell unit according to claim 1,
Equipped with a notification section,
If the oxygen concentration detected by the oxygen concentration detection section is lower than a predetermined concentration after executing the process of ventilating the inside of the fuel cell unit, the control section may control the oxygen concentration of the air outside the fuel cell unit to A fuel cell unit, characterized in that the notification section notifies the outside of the fuel cell unit that the fuel cell temperature has decreased.

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