Patent ID: 8110313

Claim:
A fuel cell system comprising: a fuel cell assembly having a plurality of fuel cell sets in electrical communication, each fuel cell set generating power through an electrochemical reaction between a fuel gas and an oxidant gas; a plurality of cell-set voltage sensors, each voltage sensor associated with a fuel cell set to detect a cell-set voltage at the fuel cell set and to further transmit each cell-set voltage as a signal; a coolant circulation system for supplying a coolant to the fuel cell sets of the fuel cell assembly; a coolant inlet temperature sensor positioned along the circulation system that detects an inflow temperature of the coolant flowing into the fuel cell assembly and transmits the inflow temperature as a signal; and a control unit programmed to receive the signals transmitted from the voltage and temperature sensors, to estimate a cell-set temperature difference of each fuel cell set according to the inflow temperature and a respective cell-set voltage and to control the circulation of coolant through the coolant circulation system according to the cell-set temperature difference, wherein the cell-set temperature difference is a difference in temperature between the coolant being delivered to an associated fuel cell set and that of the coolant being exhausted from the fuel cell assembly.