Patent ID: 7740963

Claim:
A liquid fuel type fuel cell system comprising: a unit cell or a cell stack having a plurality of the unit cells, the unit cell or cell stack provided with an anode and a cathode opposite to each other and an electrolyte of proton-conductive solid polymer membrane interposed between the anode and the cathode, and the unit cell or cell stack provided with means for supplying a liquid fuel to the anode and means for supplying an oxidant gas to the cathode; a fuel tank storing a methanol aqueous solution having a methanol concentration of 1-8 wt % as the liquid fuel to be supplied to the unit cell or cell stack; an antifreeze tank storing a high concentration methanol aqueous solution having a methanol concentration of 8-60 wt % as antifreeze, wherein the methanol concentration of the antifreeze stored in the antifreeze tank is greater than the methanol concentration of the methanol aqueous solution stored in the fuel tank; and means for injecting said antifreeze into and holding said antifreeze in at least said cathode side and said anode side of said unit cell or said cell stack upon stand-by operation of the liquid fuel type fuel cell system.