Patent ID: 7816045

Claim:
A fuel cell system comprising: a fuel cell stack which is supplied with a fuel aqueous solution and generates electric energy by electro-chemical reaction; a concentration detector arranged to detect a concentration of the fuel aqueous solution to be supplied to the fuel cell stack; a temperature detector arranged to detect a temperature of the fuel cell stack; a central processing unit programmed to control the fuel cell system; a memory arranged to store data including a first correspondence data which indicates a correspondence between the temperature of the fuel cell stack and a target concentration of the fuel aqueous solution; the central processing unit and the memory together defining an input amount determining device programmed to determine an amount of fuel to be inputted to the fuel aqueous solution based on the concentration of the fuel aqueous solution detected by the concentration detector and the temperature of the fuel cell stack detected by the temperature detector; and an input device arranged to input the determined amount of the fuel to the fuel aqueous solution; wherein the central processing unit further includes: a target concentration determining device programmed to determine a target concentration of the fuel aqueous solution by making reference to the first correspondence data in the memory and based on the temperature of the fuel cell stack detected by the temperature detector; an input fuel amount determining device programmed to determine an amount of fuel to be input based on the concentration of the fuel aqueous solution detected by the concentration detector and the target concentration determined by the target concentration determining device; and a target temperature raise time setting device programmed to set a target temperature raise time which indicates a time that is necessary for increasing the fuel cell stack to a predetermined temperature; wherein the data in the memory further includes a second correspondence data which indicates a correspondence between the temperature of the fuel cell stack, the target temperature raise time, and the target concentration; and the target concentration determining device determines the target concentration of the fuel aqueous solution by making reference to the second correspondence data and based on the temperature of the fuel cell stack detected by the temperature detector and the target temperature raise time set by the target temperature raise time setting device.