Fuel cell system and control method thereof

A fuel cell system comprising:

• a power generation unit including an anode, a cathode and an electrolytic film provided between the anode and the cathode, the anode being supplied with a mixture fuel with a concentration, the cathode being exposed to air, power being generated by electrochemical reaction between the anode and the cathode, a discharge liquid containing an unreacted mixture fuel being discharged from the anode, the power generation unit producing heat as a result of the electrochemical reaction;
• a power adjustment unit which adjusts power supplied from the power generation unit;
• a fuel supply unit which supplies a raw fuel or a highly concentrated fuel;
• a mixing tank provided across a fuel circulation path which permits the discharge liquid from the power generation unit to be circulated to the anode, the mixing tank containing the mixture fuel, the mixture fuel being a mixture of the raw fuel or the highly concentrated fuel and the discharge liquid;
• a fuel circulation unit which circulates the mixture fuel from the mixing tank to the anode;
• and
• a volume sensor which detects a volume of the mixture fuel contained in the mixing tank;
• a control unit programmed to control temperature of the power generation unit in accordance with the volume of the mixture fuel in the mixing tank, wherein the control unit is programmed to decrease the temperature of the power generation unit when the volume of the mixture fuel is lower than a preset volume range, the control unit is programmed to maintain the temperature of the power generation unit unchanged when the volume of the mixture fuel falls within the preset volume range, and the control unit is programmed to increase the temperature of the power generation unit when the volume of the mixture fuel exceeds the preset volume range.