Technical Field
The present invention relates to an electric power supply system.
Background Art
Heretofore, there has been proposed an electric power supply system in which a direct current power supply such as a battery and fuel cell mounted on an electric vehicle such as an electric automobile and a fuel cell automobile is used to supply electricity to household electrical devices (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2006-325392).
The electric power supply system disclosed in Japanese Unexamined Patent Application, First Publication No. 2006-325392 comprises: a vehicle having a means for supplying electric power to the outside of the vehicle; a stationary fuel cell system provided with an inverter; a load device that receives electric power supply from the stationary fuel cell system; and a system power supply that supplies electric power to the stationary fuel cell system. In the event of a power outage, this electric power supply system connects the vehicle and the stationary fuel cell system, and supplies electric power from the vehicle to the load device via the inverter of the stationary fuel cell system.
As a fuel cell, there is known a fuel cell stack in which a membrane electrode assembly is formed by arranging an anode electrode and a cathode electrode on either side of a solid polymer electrolyte membrane (hereunder, referred to as “electrolyte membrane”), arranging a pair of separators on either side of this membrane electrode assembly to form a flat unit fuel cell (hereunder, referred to as “unit cell”), and then stacking a plurality of these unit cells together to form a fuel cell stack. In this fuel cell, hydrogen ions produced by a catalytic reaction at the anode pass through the electrolyte membrane and move toward the cathode. There, they react with the oxygen in the air, giving rise to an electrochemical reaction and the generation of electric power.
The fuel cell described above generates heat as electric power generation is performed, and therefore, the generated water produced as a result of the electric power generation in the fuel cell is likely to vaporize. The generated water that has vaporized (water vapor) is discharged together with cathode off-gas and anode off-gas, and as a result, the electrolyte membrane of the fuel cell becomes dry. If the fuel cell becomes excessively dry (hereunder, referred to as “dry-up condition”), there is a problem in that the power generation performance of the fuel cell becomes reduced, and this consequently leads to deterioration in the electrolyte membrane.
Therefore, the fuel cell system is provided with a cooling device for cooling the fuel cell which generates heat as power generation is performed. The cooling device is formed with a coolant that circulates in the fuel cell and absorbs heat, a radiator for releasing heat from the coolant, and a radiator fan that blows air to the radiator.
Incidentally, in general, cooling devices of fuel cells and control thereof are designed in consideration of a vehicle in a state of traveling.
Specifically, they are designed such that in those cases where the traveling speed of the vehicle is high and the amount of electric power being generated by the fuel cell is high, traveling air stream is introduced into the radiator and the radiator fan is rotated at a high rotation speed, to release the heat of the coolant flowing through the radiator. Moreover, they are designed such that in those cases where the traveling speed of the vehicle is low and the amount of electric power being generated by the fuel cell is low, traveling air stream is introduced into the radiator and the radiator fan is rotated at a low rotation speed, to release the heat of the coolant flowing through the radiator. As a result of this, the fuel cell is appropriately cooled to suit the traveling state of the vehicle (to suit the electric power generation state of the fuel cell), and it is therefore possible to prevent the electrolyte membrane from becoming dry when the vehicle is traveling.
Furthermore, the fuel cell system is designed so that rotation of the radiator fan stops when the vehicle is stopped and the electric power generation of the fuel cell is stopped. As a result, wasteful electric power consumption by the radiator fan can be prevented.