CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2020-152810 filed on Sep. 11, 2020, incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a fuel cell system.

2. Description of Related Art

Japanese Unexamined Patent Application Publication No. 2019-207802 (JP 2019-207802 A) discloses a fuel cell system that includes a plurality of fuel cell stacks, a plurality of air supply devices serving to supply air by a reciprocating motion of a mechanical portion, and a plurality of supply pipes and discharges exhaust gas from the plurality of fuel cell stacks together. A control unit of the fuel cell system controls the mechanical portions of the air supply devices such that the superimposed amplitude of pressure waves which are generated due to the reciprocating motions of the mechanical portions of the air supply devices decreases.

SUMMARY

However, in the fuel cell system disclosed in Japanese Unexamined Patent Application Publication No. 2019-207802 (JP 2019-207802 A), problems which are caused when some of the plurality of fuel cell stacks and the plurality of air supply devices are operating and the others are not operating have not been satisfactorily studied. For example, since exhaust pipes of the fuel cell stacks are connected in parallel, there is a possibility that exhaust gas discharged from an operating fuel cell stack flows into the exhaust pipe of a non-operating fuel cell stack.

The present disclosure can be embodied in the following configurations.

According to an aspect of the present disclosure, there is provided a fuel cell system. The fuel cell system includes: a plurality of fuel cell units of which each includes a fuel cell, an air supply pipe connected to the fuel cell, an air supply device provided in the air supply pipe, an air discharge pipe configured to discharge exhaust gas including fuel exhaust gas and air exhaust gas from the fuel cell, and a control unit configured to control operation of the fuel cell; and an exhaust pipe that is connected to the plurality of air discharge pipes and configured to discharge the exhaust gas to the outside of the fuel cell system. The control units of the plurality of fuel cell units are configured such that, when one or more fuel cell units included in the plurality of fuel cell units are operating to generate electric power and each of the remainder of the plurality of fuel cell units is not operating to generate electric power, the control unit of the fuel cell unit that is not operating to generate electric power activates the air supply device of the corresponding fuel cell unit. According to this aspect, since the control unit of the fuel cell unit that is not operating to generate electric power activates the air supply device of the fuel cell unit to discharge air to the air discharge pipe of the fuel cell unit, it is possible to curb a backflow of exhaust gas of the fuel cell unit that is operating to generate electric power to the air discharge pipe of the fuel cell unit that is not operating to generate electric power.

In the fuel cell system according to the aspect, each of the plurality of fuel cell units may include: a bypass pipe that is configured to connect the air discharge pipe and the air supply pipe and configured to form a bypass passage that bypasses the fuel cell; and a bypass valve that is provided in the bypass pipe and configured to control a flow rate of air in the bypass pipe. The control unit of the fuel cell unit that is not operating to generate electric power may be configured to open the bypass valve. According to this aspect, air is not supplied to a fuel cell that is not operating to generate electric power.

In the fuel cell system according to the aspect, the control unit of the fuel cell unit that is not operating to generate electric power may be configured to cause the air supply device of the corresponding fuel cell unit to supply air at a minimum flow rate and to fully open the bypass valve of the corresponding fuel cell unit. According to this aspect, it is possible to decrease power consumption in the air supply device of the fuel cell unit that is not operating to generate electric power.

In the fuel cell system according to the aspect, the control unit of the fuel cell unit that is not operating to generate electric power may be configured to cause the air supply device of the corresponding fuel cell unit to start supply of air at a timing at which a predetermined time has elapsed after supply of air by the air supply device of the fuel cell unit that is operating to generate electric power has been started. Exhaust gas of the fuel cell unit that is operating to generate electric power does not flow back to the fuel cell unit that is not operating to generate electric power for a predetermined time. According to this aspect, it is possible to further decrease power consumption in the air supply device in comparison with a case in which supply of air in the fuel cell unit that is not operating to generate electric power is started at the same time as starting supply of air by the air supply device in the fuel cell unit that is operating to generate electric power.

In the fuel cell system according to the aspect, lengths of the air discharge pipes of the plurality of fuel cell units may be different, and the control unit of the fuel cell unit that is not operating to generate electric power may be configured to cause the air supply device of the corresponding fuel cell unit to start supply of air with a time delay corresponding to a time until exhaust gas in the fuel cell unit that is operating to generate electric power reaches the air discharge pipe of the fuel cell unit that is not operating to generate electric power via the exhaust pipe. According to this aspect, it is possible to curb a backflow of exhaust gas due to a difference in power-generating operation timings between the power generation units. It is also possible to decrease power consumption in the air supply device.

The fuel cell system according to the aspect may further include: a housing configured to accommodate the plurality of fuel cell units therein; a ventilation device provided in the housing and configured to ventilate the inside of the housing; and a ventilation control unit configured to increase a ventilation rate of the ventilation device when each of one or more fuel cell units included in the plurality of fuel cell units is not able to be supplied with air by the air supply device in comparison with a case in which air is able to be supplied by all of the air supply devices. According to this aspect, even when exhaust gas including fuel exhaust gas flows backward, it is possible to discharge the exhaust gas including fuel exhaust gas in the housing to the outside of the housing using the ventilation device.

