A method for designing a fuel processor having an optimized size (i.e., volume
and mass) for use in a fuel cell system which provides electrical power in a plurality
of power ranges. The method includes maximizing water availability in the fuel
cell system and sizing the first CO reduction reactor to provide for peak fuel
cell system operational efficiency in a most-used power range while sizing the
second CO reduction reactor to ensure the fuel processor can components to operate
at a desired maximum power. The method allows development of a fuel processor that
has significantly lower total mass and volume, and shorter start-up time, than
conventionally designed processors, yet can perform at a desired maximum power.
