Abstract: The present invention relates to improving the overall efficiency of a fuel cell system by reducing parasitic power consumption. A controller is programmed to decrease oxidant stoichiometry until oxidant starvation is detected or until oxidant stoichiometry is about one. When oxidant starvation is detected, the oxidant stoichiometry is increased until oxidant starvation is no longer detected. The fuel cell system employs a sensor for detecting an operational characteristic such as voltage output, or oxygen or hydrogen concentration in the cathode exhaust stream. The controller uses the operational characteristic to calculate oxidant stoichiometry or to determine when there is oxidant starvation at the cathode.

Abstract: The invention provides a fuel cell arrangement with a plurality of fuel cell stacks which are stacked on top of one another and are enclosed in a sealed exterior housing. Supply air is freely guided to the fuel cell stacks within the enclosure, while combustion gas is provided to the respective stacks by means of pipes. A plurality of flat seals are provided between adjacent fuel cell stacks, each having a central air opening and a separate peripheral combustion gas channel. The lowermost fuel stack is mounted by means of such a seal, on a base plate into which a collective channel for exhaust air and a channel for combustion gas are integrated.