Energy analysis of electric vehicles using batteries or fuel cells through well-to-wheel driving cycle simulations

This work presents a study of the energy and environmental balances for electric vehicles using batteries or fuel cells, through the methodology of the well to wheel (WTW) analysis, applied to ECE-EUDC driving cycle simulations. Well to wheel balances are carried out considering different scenarios for the primary energy supply. The fuel cell electric vehicles (FCEV) are based on the polymer electrolyte membrane (PEM) technology, and it is discussed the possibility to feed the fuel cell with (i) hydrogen directly stored onboard and generated separately by water hydrolysis (using renewable energy sources) or by conversion processes using coal or natural gas as primary energy Source (through gasification or reforming), (ii) hydrogen generated onboard with a fuel processor fed by natural gas, ethanol, methanol or gasoline. The battery electric vehicles (BEV) are based on Li-ion batteries charged with electricity generated by central power stations, either based on renewable energy, coal, natural gas or reflecting the average EU power generation feedstock. A further alternative is considered: the integration of a small battery to FCEV, exploiting a hybrid Solution that allows recovering energy during decelerations and Substantially improves the system energy efficiency. After a preliminary WTW analysis carried Out under nominal operating conditions. the work discusses the simulation of the vehicles energy consumption when following standardized ECE-EUDC driving cycle. The analysis is carried out considering different hypothesis about the vehicle driving range, the maximum speed requirements and the possibility to sustain more aggressive driving cycles. The analysis shows interesting conclusions, with best results achieved by BEVs only for very limited driving range requirements, while the fuel cell solutions yield best performances for more extended driving ranges where the battery weight becomes too high. Results are finally compared to those of conventional internal combustion engine vehicles, showing the potential advantages of the different solutions considered in the paper and indicating the possibility to reach the target of zero-emission vehicles (ZEV). (c) 2008 Elsevier B.V. All rights reserved.