A hybrid power source for pulse power applications

Portable 12 V power supplies are used extensively for communications and po wer tool applications. These devices demand fast response times of the powe r supply. Fuel cells are generally best suited to continuous power applicat ions and require an initial warm-up period, although they offer the prospec t of increased operational duration over a battery for a given weight of po rtable system. This paper investigates the combination of specific energy p erformance from the fuel cell system with the specific power and response t ime of the battery. Two separate hybrid systems have been developed and tes ted; a planar, 20-cell, polymer electrolyte membrane fuel cell (PEMFC) stac k together with either a lead-acid or nickel/cadmium battery; and a convent ional 20-cell, bipolar, PEMFC stack. Both systems have been tested under pu lse-load conditions at temperatures between - 20 degrees C and +40 degrees C, and for comparison, the individual components have undergone similar tes ts. The hybrid systems have successfully operated continuously for several weeks under load profiles that the fuel cell alone could not sustain. Crown Copyright (C) 1999 Published by Elsevier Science S.A. All rights reserved.