On-Board Integration of Hybrid Energy Storage Systems in Heavy Duty Vehicles: The Electric Buses Use Case

Road transportation contributes to 79% of the total transport emissions. To achieve European emissions targets by 2050, a sustainable mobility based on electric vehicles (EVs) powered by batteries or fuel cells is required. Albeit Li-ion batteries represent the best choice for light duty EVs, green transition for heavy duty transport is more challenging because of the greater mileage and the lack of fast-charging infrastructure. To extend mileage range and energy storage lifespan, hybridization of different energy storage technologies represents a promising solution towards a green transition based on zero-emissions heavy duty vehicles. In this Chapter, different systems are presented for a bus application. Three innovative hybrid propulsion systems, consisting of: (i) LiFePO4 battery (LFP)/Proton Exchange Membrane Fuel Cell (PEMFC), (ii) LFP/Vanadium Redox Flow Battery (VRFB) and (iii) Ni–NaCl battery coupled with PEMFC are analysed with reference to a real case study (i.e., urban electric bus) and compared to an electric bus powered by only LFP. With respect to the case study, it is demonstrated that there are benefits of hybridization in terms of mileage range and battery lifespan extension (when LFP is considered), paving the way for an efficient and effective green transition.