Patent ID: 8652698

Claim:
A fuel cell having a stack structure of multiple cells, where each of the cells has a membrane electrode assembly that is obtained by integrating an anode with a cathode across a specific electrolyte membrane and is interposed between a pair of separators, the fuel cell comprising: a fuel gas supply manifold that distributes a supply of fuel gas to the anodes of the respective cells; and an anode off gas exhaust manifold that collects flows of unconsumed fuel gas-containing anode off gas from the anodes of the respective cells to a collective flow of the anode off gas and discharges the collective flow of the anode off gas out of the fuel cell, each of the cells having a fuel gas flow path that makes a flow of the fuel gas, which is supplied from the fuel gas supply manifold, along surface of the anode and makes a flow of the anode off gas into the anode off gas exhaust manifold, the multiple cells including: a first cell having a first fuel gas flow path; and a second cell having a second fuel gas flow path, which is constructed to have a specific flow path structure having a higher potential for a decrease in concentration of the fuel gas in at least a partial area during power generation, compared with a potential of the first fuel gas flow path, the specific flow path structure of the second fuel gas flow path including a restriction element that narrows a sectional area of flow passage in part of the second fuel gas flow path; a non-narrowed area other than the restriction element, the specific flow path structure being configured such that fuel gas in a specific part of the non-narrowed area downstream of the restriction element has a pressure lower than a pressure of fuel gas in the first fuel gas flow path, and a sensor that measures a specific parameter value relating to the decrease in concentration of the fuel gas in the second fuel gas flow path; wherein the cathode of the membrane electrode assembly of the second cell includes a partial electrode located in an area opposite to the specific part of the non-narrowed area downstream of the restriction element; and wherein the sensor is a potential sensor that measures a local cathode potential of the partial electrode in the area opposite to the non-narrowed downstream area across the specific electrolyte membrane of the second cell as the specific parameter value.