Patent ID: 8748048

Claim:
A fuel cell system comprising: a fuel cell to generate power utilizing an electrochemical reaction between oxidant gas and fuel gas which are supplied to the fuel cell; an oxidant-gas supply passage through which the oxidant gas flows toward the fuel cell; a compressor provided in the oxidant-gas supply passage and capable of sucking and pressurizing the oxidant gas to discharge the oxidant gas toward the fuel cell; a water injection device to inject water toward a suction port of the compressor; a return passage connecting an upstream portion in the oxidant-gas supply passage upstream of the compressor and a downstream portion in the oxidant-gas supply passage downstream of the compressor to bypass the compressor; a regulation valve whose opening is adjustable and which is provided in the return passage; a moisture-content measuring device provided in the oxidant-gas supply passage downstream of the compressor and downstream of the downstream portion of the return passage; and a controller connected to the moisture-content measuring device, wherein the controller is configured to control the opening of the regulation valve based on a moisture content measured by the moisture-content measuring device.