Abstract
Key Words: Hybrid Propulsion Systems, PEM Fuel Cells, Hydrogen.
In this paper the main issues related to the development of electric vehicles utilizing hydrogen fuel cells for on board generation of electric energy are faced and discussed. Two laboratory fuel cell systems based on 2.5 and 20 kW H2/air proton exchange membrane stacks were designed, realized and characterized with the aim to elucidate the specific concerns to be considered for automotive applications. The effect of the main operative variables (temperature, pressure and stoichiometric ratio) on stack power and efficiency was experimentally evaluated, while the role of air compressor, fuel purge, stack temperature and humidification strategy in the system management was evidenced. The characterization results were analysed in terms of H2 consumption and available power specifying the energy losses of the individual fuel cell system components. The two fuel cell systems were then used to realize two complete fuel cell power trains with mechanical power of 2 and 30 kW, suitable for scooter and minibus, respectively. The experimental study was conducted on dynamic test benches, able to simulate the behaviour of real vehicles on standard driving cycles, and was focused on the effect of different strategies of energy management, necessary to regulate the power flows inside the power train, on vehicle performance and efficiency.