Hybrid energy/power sources for electric vehicle traction systems

Electric vehicles are set to play a prominent role in addressing the energy and environmental impact of an increasing road transport population by offering a more energy efficient and less polluting drive-train alternative to conventional internal combustion engine (ICE) vehicles. Given the energy (and hence range) and performance limitations of electro-chemical battery storage systems, hybrid systems combining energy and power dense storage technologies have been proposed for vehicle applications. Further, in recent years, fuel cell systems have also been proposed as a potential energy carrier, and the most suitable alternative likely to displace petroleum based fuels during the first half of this century. Whilst there are many technical and resource management issues associated with the displacement of petroleum fuels for transportation, and the commensurate supply infrastructure requirements, this paper will discuss some of the application issues associated with the implementation of hybrid energy/power sources for electric vehicle traction systems. Results from two case studies based on the combination of an electro-chemical storage battery and fuel cell energy sources with a supercapacitor peak power buffer will be presented to illustrate the benefits of on-board source hybridisation for urban road vehicles. It will discuss the simulation models and highlight design optimisation for energy efficiency and storage mass/volume of such systems when connected in hybrid configurations.