Patent ID: 7147945

Claim:
A system for determining a gas composition within a fuel cell 12 of a shut down fuel cell power plant, the system comprising; a. at least one fuel cell 12 for generating electrical current from hydrogen containing reducing fluid and process oxidant reactant streams, wherein the fuel cell includes an anode electrode 14 and a cathode electrode 16 on opposed sides of an electrolyte 18 , an anode flow field 28 adjacent the anode electrode 14 for directing the reducing fluid stream to flow adjacent to the anode electrode 14 , a cathode flow field 30 adjacent the cathode electrode 16 for directing the process oxidant stream to flow adjacent the cathode electrode 16 , and an anode inlet valve 62 secured in fluid communication with the anode flow field 28 for selectively admitting the reducing fluid into the anode flow field 28 ; and, b. a sensor circuit 86 secured in electrical connection with the fuel cell 12 , wherein the circuit 86 includes a power source 88 , a voltage-measuring device 90 , and a sensor circuit switch 92 , the sensor circuit 86 being secured to the fuel cell 12 so that the power source 88 may selectively deliver a pre-determined sensing current to the fuel cell 12 for a pre-determined sensing duration.