The message
from David Hansen contains these words:

Still a rather expensive waste of time though installing these things
(along
with windmills stuck on the roof or huge windfarms in the countryside)

Ah,proof by assertion.

No more so that the stuff you rely on.

you still have to rely on nuclear/coal/gas/oil fired power stations to
maintain a reliable and constant supply of electricity.

The idea that any source of electricity generation is reliable is
mildly amusing. For example a little over a year ago one of the
largest coal fired plants in Europe had to be shut down suddenly
after a conveyor belt fell down.
http://www.thecourier.co.uk/output/2007/01/22/newsstory9203741t0.asp

And not so long ago two turbines self destructed. The conveyer belt was
no doubt quickly repaired. Not so the turbines.

Take a conventional generator out of service for a whole month in a year
and you would still have a load factor in excess of 90% if the demand
was there. With wind turbines the system allows for the demand always to
be there but the average load factor was under 30% last time I looked
with some turbines under 20%. Relying on wind for more than a small
proportion of total capacity is a recipe for disaster. Even the
proponents of wind power were saying until recently that 20% was the
practical limit and even for that you need an installed capacity of
circa two thirds of total demand.

One of the reasons for connecting local electricity systems together
from say the 1930s was to allow excess standby plant to be shut down
while increasing overall reliability. Any connected source of
electricity feeds into this common system. Ignoring this simple fact
leads one to make foolish statements and come up with ridiculous
costs, as the Royal Academy of Engineering have demonstrated.

If you think that shutting down power plants because of lack of demand
or even for routine maintenance or repair is on a par with the weather
shutting down wind turbines either because of oversupply or under supply
of wind you really do deserve your reputation for not thinking things
through.

--
Roger Chapman