Patent ID: 7179555

Claim:
A fuel cell system comprising: a fuel cell stack including a plurality of fuel cells stacked in a stack direction, for generating electric power by introduction of a fuel gas, wherein: each fuel cell has therein a plurality of thermal medium passages, each thermal medium passage being independent from each other thermal medium passage such that a thermal medium independently flows through each of the thermal medium passages; the thermal medium passages include portions which are arranged independent of each other in a plurality of lines, parallel to each other in a direction approximately perpendicular to the stack direction; a thermal medium passage of each fuel cell communicates with a thermal medium passage in an adjacent fuel cell in the stack direction; a heating device for heating the thermal medium; a thermal medium circulation device for circulating the thermal medium through the thermal medium passages; a temperature detection device disposed at an outlet of each thermal medium passage for detecting a temperature of the thermal medium a controller for controlling the thermal medium circulation device based on the temperature detected by each of the temperature detection devices; and an opening/closing member which selectively opens and closes a respective thermal medium passage based on the temperature detected by each of the temperature detecting members such that the temperature of the thermal medium at the outlets of the thermal medium passages stays within a predetermined range; wherein when the controller determines that the temperature of the thermal medium detected by one of said temperature detection devices is lower than a predetermined temperature, the controller outputs a first operation signal to the thermal medium circulation device and the opening/closing member so as to circulate the thermal medium heated by the heating device into a part of the thermal medium passages; and when the controller determines that the temperature of the thermal medium detected by one of said temperature detection devices is higher than the predetermined temperature, the controller outputs a second operation signal to the thermal medium circulation device and the opening/closing member so as to circulate the thermal medium heated by the heating device into the fuel cell from the part of the thermal medium passages to all of the thermal medium passages.