Electric vehicle
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| 9 Design Considerations 9.1 Introduction To maximise the fuel efficiency of any vehicle the mass, aerodynamic drag and rolling resistance have to be minimised, while at the same time maximising engine/motor and transmission efficiencies. It is particularly important to design battery electric vehicles with high efficiencies in order to reduce the mass of expensive batteries required. This chapter builds on the previous chapter on vehicle modelling. The various parameters that went into the model are examined individually, together with their effect on vehicle performance. Various choices available to designers to optimise their vehicle design are discussed, as is the greater flexibility to place components in electrical vehicles with a view to optimising weight positioning and minimising aerodynamic drag. 9.2 Aerodynamic Considerations 9.2.1 Aerodynamics and Energy It is well known that the more aerodynamic a vehicle is, the lower is its energy consumption. Bearing in mind the high cost of onboard electrical energy, the aerodynamics of electric vehicles is particularly important, especially at high speeds. Let us first consider the effect of aerodynamic drag. As seen in Chapter 8, the drag force F ad on a vehicle is F ad = 1 2 ρAC d v 2 (9.1) and the power P adw (W) at the vehicle’s wheels required to overcome this air resistance is P adw = F adw × v = 1 2 ρAC d v 3 (9.2) Electric Vehicle Technology Explained, Second Edition. James Larminie and John Lowry. © 2012 John Wiley & Sons, Ltd. Published 2012 by John Wiley & Sons, Ltd. |