With air and fuel feed rates at twice their design values, cold start time is reduced to 63 s. Cold start could be achieved in 36 s if fuel processor component masses were reduced to one-half their values in the present designs. Such a system needs no compressor or expander, but it is difficult to recover the energy in the spent anode gas. There is a large heat load on the condenser for water recovery. The fuel-cell stack needs nearly twice the active cell area for system efficiency comparable to that of a pressurized system.
Water management is a significant issue, particularly at elevated ambient temperatures.
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