Hydrogen Powertrains: A Comparison Between Different Solutions for an Urban Bus

In the compelling need for the decarbonization of the transport sector, hydrogen could play a crucial role, especially in heavy duty applications where the limited specific energy of chemical batteries can significantly reduce either the payload or the operative range. Moreover, the possibility to use Hydrogen not only within Fuel Cells (FCs) systems but also as a fuel in Internal Combustion Engines (ICEs) makes it even more attractive for future sustainable transport systems. In such a framework, this work aims to compare, through numerical simulation, different hydrogen powertrain configurations designed for an urban bus application. In particular, a series hybrid architecture was chosen as a reference considering three different technologies for its Auxiliary Power Unit: two internal combustion engines fuelled with Diesel and Hydrogen respectively, and a Fuel Cell featuring almost the same power level of the internal combustion engines. The study was carried out in real world driving conditions and the results were also compared with the ones of a conventional diesel powertrain. In particular, the numerical analysis highlighted an evident gain in terms of fuel consumption and overall efficiencies for both FCEV and H2-ICE, with respect to conventional and hybrid diesel powertrains. Based on the present results, further developments will be devoted to the optimization of the hybrid control strategy for a cost-effective exploitation of the hydrogen fueled configurations.