Factors affecting electric vehicle energy consumption

Abstract

Internal combustion (IC) engines waste a majority of the energy they consume, with only 20% actually going into moving the vehicle. The drivetrains of electric vehicles (EVs) can operate at over 80% efficiency which shows that they have great potential in reducing the transportation energy demand. This paper initially quantifies the energy needed to run an EV, having similar dimensions and performance to modern IC vehicles. Simple range and cost calculations were used to establish the advancements needed in battery technology to match the ranges of IC vehicles. Factors affecting EV energy consumption are then addressed, with the aid of MATLABw simulations, to ascertain what variations can be expected in real-world situations and the benefits of optimising vehicle parameters. The results are then compared with conventional and hybrid IC vehicles. It is shown that an optimised EV can achieve a 63% 'tank-to-wheels' energy reduction over the best conventional IC vehicles available, and 60% over hybrids. The effects of either a badly optimised EV, hard acceleration during the driving cycle, or constant large accessory power draws, such as heaters and demisters, are each shown to increase the EVs energy consumption by 70%/km. To achieve the performance and practicalities comparable with modern IC vehicles, new battery technologies with specific energies of > 300 Wh/kg are required. © 2011 Taylor & Francis.