tommallett:A friend of mine is an engineer and he recently conducted a study suggesting that of all the different ways to run cars it is petrol that is the most energy efficient if everything is traced back to source.
The petrol engine is thermodynamically very inefficient and is worst at light load, where most petrol engines spend most of their time. The efficiency of an electric car from 'socket to wheel' is far in excess of that of a petrol car. If (big, big if at the moment) the electricity comes from a renewable source, the amount of wasted energy is small.
However, a typical fossil-fuel power station is not greatly more efficient than a petrol engine. I believe 30-40% is a typical figure, compared to maybe 25-30% for a petrol engine. Clearly adding in the transmission, power conversion, battery charging and motor losses and with centralised generation from fossil fuels the EV is going to struggle to better the petrol engine.
A better approach would be to have the EV's internal batteries charged by an appropriately-sized ICE, which is run at it's most efficient operating point when in use. Battery technology is improving, in particular reduced internal resistance allowing the battery to be charged rapidly, which would be neccessary for such a scheme. This 'series hybrid' would not be significantly more *efficient* than a traditional petrol-engined car, but combined with regenerative braking could deliver very significant improvements in fuel consumption per unit distance (which is what really matters).
The good news for drivers is that any EV with fully regenerative braking needs very powerful motors to give adequate braking performance (work out the braking power of the average family hatchback, it's huge compared to the engine power), and so has the potential for delivering rapid acceleration too, which can only be a good thing!
"Rockets are just another name for trouble. Either you just had trouble, you are having trouble, or you are going to have trouble." - Milt Rosen, Viking Program Director, White Sands Missile Test Range