A Novel High Efficiency Hybrid Power Unit for Hydrogen-Fueled City Transit Bus

The paper presents the analysis of a hydrogen-fueled city transit bus with `zero' emission. The vehicle power train is based on electric motors fed by a novel and high efficiency hybrid power unit composed by a functional coupling of a hydrogen fuel cell stack and a set of kinetic energy storage systems at high speed. The transit bus has been simulated by means of a numerical model by using the worldwide harmonized drive cycle for light-duty vehicle test procedure. The implemented parametric model calculates the traction power requirement, by starting from the speed profile, taking into account both system and path parameters (vehicle characteristics, load factor and path features). Each component of the power train is modelled separately and validated with experimental data from literature. Specific fuel consumptions and emissions for the traction are compared with the ones of a similar diesel motorized transit bus in the same operating conditions. The results highlight that the proposed hybrid power unit allows a significant fuel and CO
₂
emission saving to be achieved.