System Level Modeling and Optimization of Fuel Cell Powered Auxiliary Power Unit (APU) to be used in Commercial Vehicles

Engines of commercial vehicles deliver significant amount of power (more than 25% of propulsive power) for non-propulsive loads such as air-conditioner, alternator, air compressor, radiator fan, steering oil pump, lights etc. Use of these auxiliaries cause sub-optimal utilization of engine power resulting in increased fuel consumption and emissions. A fuel cell powered auxiliary power unit (FC-APU) is proposed to isolate the auxiliaries from the engine. Use of FC-APU shall help improve load carrying capacity, gradeability, fuel efficiency and emissions of the vehicle. This paper describes a mathematical system level model developed using MATLAB-SIMULINK to estimate auxiliary power consumption and simulate FC-APU system. A statistical analysis is performed on the power consumed by various auxiliaries during different duty cycles. The data is used to propose a FC- APU system. Fuel cell is the most expensive component in the system. Cost of the fuel cell increases with increase in power rating. Hence, objective of the system simulation is to propose a FC-APU system featuring fuel cell with lowest possible power rating.