LAUSR

Abstract The suitability of an energy source for automotive application is determined by its gravimetric and volumetric energy density, portability, and safety characteristics. Hydrocarbon fuels predominate the energy resource in transportation sector mainly because of the favorable energy density and easiness for fuel handling, storage and transportation. The alternative energy sources have started to play an important role because they have a lower carbon footprint and the potential to decrease the reliance on the fossil fuels. Among the leading contenders, batteries and fuel cells draw the most attention in recent years because of their potential towards renewable mobility. In this paper, the energy density of various energy sources is reviewed, and its effect on the payload and driving range of the vehicles is discussed. The specific energy of hydrocarbon fuels (from fossil fuels to renewable fuels), fuel cells and batteries (from theoretical value to packaged value) is compared. The evolution of the energy density of the batteries is also investigated and the challenges towards the further enhancement of the battery energy density are presented. Present application status of the three energy sources is summarized, and the suitable energy source for various transportation sectors is suggested. Finally, the present status of hybrid vehicles and renewable hydrocarbon fuels with lower carbon footprint is discussed, which shows promise to overcome the environmental impact without sacrificing overall vehicle performances.