Assessment of the Application of Fuel Cell APUs and Starter-Generators to Reduce Automobile Fuel Consumption

Auxiliary power units (APUs) provide electrical power, with favourable efficiency and independent of the drive system, for a variety of mobile applications. The demand for electricity increases with increasing demand for convenience and safety functions, as well as for control and regulation services. Examples of these functions are engine-independent air conditioning in motor vehicles or by-wire technologies in aircraft. The additional power must be provided with the greatest possible efficiency, due to the general requirement for an overall reduction in fuel consumption.This contribution compares the present status of on-board electricity supply in conventional passenger cars with variants, based on the starter-generator and the auxiliary power unit (APU). The results of a process engineering analysis define the potential efficiency of electricity generation with solid oxide fuel cell (SOFC) based systems. In addition to the load profiles of the auxiliaries, the driving cycle must be defined within the framework of a model-based dynamic drive train simulation, in order to finally determine the fuel consumption per kilometre in dynamic operation. As a result, the fuel consumption of the variants investigated is presented and the possibilities for applying fuel cell APUs and starter-generators assessed