Patent ID: 8057929

Claim:
A fuel cell system, comprising: a fuel cell that processes an oxidant to produce electrical energy; a variable capacity compressor system that supplies said oxidant to said fuel cell and that during operation of the fuel cell system, supplies said oxidant by operating in a mode selected from a normal mode below a threshold rate of 40%/s change in capacity and a rapid transient mode selected from an upward and downward variation at or above the threshold rate, said variable capacity compressor system comprising: a compressor that compresses said oxidant; and a compressor motor that drives said compressor a controller that monitors a power demand from said fuel cell and that selects a power source for said compressor motor, said power source being either a main power source when operating in said normal mode or a supplemental power source when operating in said rapid transient mode which is upward wherein said supplemental power source is selected from capacitors and supercapacitors and wherein said controller controls charging of said supplemental power source comprising regenerative braking of the compressor motor that converts mechanical energy into charging current.