Electric vehicles as energy processing and conversion systems

D.Ing. (Electrical & Electronic Engineering Science)In the light of a history of more than a century, and reviving interest over the last three decades, battery powered electric vehicles are seen as one of the contributing technologies to alleviate transport problems in the future. This thesis is concerned with the use of energy in road transport. In particular, some selected aspects of the application of battery powered road vehicles are addressed. The thesis gives a brief background history and reviews the forces and factors which presently play a role in the developments and future application of battery electric vehicles. The main contribution, however, lies in the field of technical clarification of some aspects of electric vehicle theoretical analysis, which have not been addressed before. The first of these technical subjects is the analysis of energy consumption of vehicles when operating under non-steady driving conditions. The analysis results in simple but relevant expressions for the energy consumption of any moving vehicle during start-stop driving, as well as driving over a hilly route. The potential benefit of kinetic energy recovery can be quantitatively determined. The theory is then applied to battery electric vehicles and the results are compared to actual recorded energy consumption figures. The second technical investigation concerns the optimisation of electric vehicle drive systems with respect to mass. It is shown that optimized drive systems should be designed to suit both the energy density characteristics of the batteries used, as well as the particular characteristics of the drive cycle to which the vehicles will be applied