"Theo Markettos" wrote in message
...
With a suitably non-trickle feed, the charging would be controlled so that
it takes place during the troughs in demand. You'd have to say something
like 'charge me by 7.30am' and the charger would know that if it hadn't
got
enough cheap (aka trough) power by 4am it would have to charge on
'expensive' power. But you still need the grid and generating plant to
supply that. The system is a very complex series of many feedback loops,
so
controlling it is quite tricky.

A similar mechanism already exists for off-peak domestic customers using
night storage heaters, who get a contract stating something like "you get 7
hours of cheap rate elctricity between the hours of 2300 and 0800 the
following morning", together with a radio controlled switch for that part of
the supply. The switches are used by the local suppliers to manipulate their
overall load in order to buy bulk electricity at the best market prices from
the generators.

It should be possible to come up with something similar for charging cars.
If you want a 100% charge in the shortest time possible during peak demand
you pay a premium for it. If you want a 25% top-up charge spread over a few
hours you get a cheaper rate. It should be possible to manage the overall
demand on the National Grid and local distribution networks in order to
avoid major upgrades - for a while.

D A Stocks