Weight and Electrical Response Tradeoffs of PEMFC Hybrid Power Sources for APUs

Introduction During the last few years, aircraft have become increasingly more electric and this trend is expected to continue well into the future as cost and weight advantages drive the market towards cheaper and more efficient aircraft. More Electric Aircraft will contain ever more electric actuators and cabin features and will need more cost efficient power, both on the ground and during critical in-flight operations [1]. Fuel cells (FC) provide an efficient, clean, and quiet means of generating electric power and are an alternative to other types auxiliary power units (APUs) such as turbogenerators or large batteries. Since aircraft safety is critical and weight is limited, all new systems must be tested not only to comply with strict electrical standards [2], but also they must be optimized with respect to weight and fuel consumption. Incorporating a FC into an aircraft system will require an additional power dense energy source, such as a battery, to permit fuel cells that have inherently slow power response times to comply with aircraft electrical standards. The slow response of a polymer electrolyte fuel cell (PEMFC) [3] is contrasted with the fast response of a lithium ion (LI) battery in Figure 1 [4].