Plugging the gap

It is widely accepted that a barrier to the uptake of electric cars is the lack of a readily accessible network of chargers. If the only place to charge up is at home, it will severely limit how far a private motorist is confident of driving.

Another limitation is the speed of charging. A full charge of an exhausted battery takes six to eight hours, something quite difficult for drivers used to filing up with petrol in five minutes to get used to.

The main factors constraining speed are the electricity supply infrastructure and battery characteristics. Fast charging of electric vehicles – such as luggage trucks at airports – is routine in industrial settings.

However, the scale of the problem of achieving filling station rates of recharge is illustrated if you consider that the effective rate of energy transfer in filling a tank with diesel in three minutes is 10MW. The biggest current wind turbines are capable of generating 9MW. Even a power station the size of Drax, which generates 4,000MW, would only produce enough electricity to refuel 400 cars simultaneously at this rate.