Patent ID: 8859156

Claim:
A solid oxide fuel cell system comprising: a fuel cell module comprising multiple fuel cell units; a fuel supply device that supplies 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 system and an amount of fuel supply to the fuel cell module for meeting the demand; an oxidation gas supply device that supplies oxidation gas to the fuel cell module; and a controller programmed to control an amount of fuel supplied from the fuel supply device; wherein the controller comprises a degradation determining circuit that determines whether the fuel cell module has degraded to a predetermined degree of degradation, and a fuel correction circuit that corrects the fuel supply function to adjust the amount of the fuel supply, based on a result of determination performed by the degradation determining circuit; and wherein the fuel correction circuit is programmed to perform correction of the fuel supply function, if the degradation circuit determines that the fuel cell module has degraded to the predetermined degree, in such a way that if a predetermined correction switching condition is not satisfied, the fuel correction circuit corrects the fuel supply function to decrease the fuel supply to the fuel cell module to thereby reduce a maximum rated power output from the fuel cell module, and if the predetermined correction switching condition is satisfied, the fuel correction circuit corrects the fuel supply function to increase the fuel supply to the fuel module to thereby prevent the maximum rated output power of the fuel cell module from further decreasing, and further wherein the predetermined correction switching condition is satisfied when one of the following is found true: (a) a rise of an operation temperature of the fuel cell units to a predetermined threshold temperature or above; (b) a decrease of the fuel supply to a predetermined threshold amount or below; (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.