In recent years interest has been growing in using fuel cell powered auxiliary power units (APUs) to reduce idling in line-haul trucks. Demonstrations of this technology have been constructed at universities and within industry, each with its own advantages and disadvantages. Invariably, in every design, tradeoffs need to be made and this has resulted in a multitude of different APU solutions that address different aspects of the problem.

This paper reviews some of the recent work related to fuel cell APUs for large trucks. The paper also examines what characteristics are important to consider in the design and integration of a fuel cell APU and outlines the strategy and methodology taken by the University of California Institute of Transportation Studies in designing and building a viable demonstration fuel cell APU.