Patent ID: 8426074

Claim:
A solid oxide fuel cell system comprising: a fuel cell module comprising multiple fuel cell units; a fuel supply device configured to supply fuel to the fuel cell module according to a fuel supply function which defines a relationship between a demand for output power from the solid oxide fuel cell and an amount of fuel supply to the fuel cell module for meeting the demand; an oxidation gas supply device configured to supply oxidant gas to the fuel cell module; and a controller programmed to control an amount of a fuel supply to the fuel cell module; wherein the controller comprises a degradation determining circuit programmed to determine degradation of the fuel cell module, and a fuel correction circuit programmed to correct the fuel supply function to adjust the amount of the fuel supply based on a result of determination performed by the degradation determining circuit, the fuel correction circuit is programmed to correct the fuel supply function, if the degradation determining circuit determines, before a predetermined correction switching condition is satisfied, that the fuel cell module has degraded, so as to increase the fuel supply to the fuel cell module so that a maximum rated power output from the fuel cell module is maintained, whereas the fuel correction circuit is further programmed to correct the fuel supply function, after degradation of the fuel cell module has progressed and the predetermined correction switching condition is satisfied, so as to reduce the fuel supply to the fuel cell module so that the maximum rated output power is reduced, and the predetermined correction switching condition comprises one of (a) a rise of an operation temperature of the fuel cell unit temperature to a predetermined threshold temperature or above, (b) an increase of the fuel supply to a predetermined threshold amount, (c) a decrease of an output power of the fuel cell module to a predetermined threshold power or below, and (d) a decrease of an output voltage of the fuel cell module to a predetermined threshold voltage or below.