On Tue, 26 May 2009, Theo Markettos wrote:

David A Stocks wrote:

A trickle-charge point is equivalent to a 13A socket inside a house.
The distribution system would barely notice that, even if everyone
started charging a car at the same time - we're talking about a system
which copes with events like a third of the nation's households putting
a kettle on the boil at the start of a TV commercial break.

Yes, but a third of the nation's households will still put the kettle on
during a commercial break... while their car is plugged in outside.
Peak loads add. (Give or take the fact that everyone's watching
different channels these days)

Trickle chargers could be set up as frequency response units:

http://en.wikipedia.org/wiki/Nationa...eserve_service

Or something similar. Basically, at the point at which everyone switches
their kettles on, cars across the city stop charging for five minutes, and
resume once the tea is brewing.

Fast charge points would probably require rationing, probably by making
them expensive to use. The peaks in electricity demand tend to occur
during the late afternoon when cars are more likely to be out on the
road than sat on charging points.

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.

It is, but it is not (quite) beyond the wit of man. I think you're
suggesting something along the lines of what i suggested above, but
cleverer.

tom

--
unconstrained by any considerations of humanity or decency