On Mon, 28 Nov 2005 23:13:31 GMT, "dennis@home"
wrote:


"Matt" wrote in message
.. .
On Mon, 28 Nov 2005 22:11:37 GMT, "dennis@home"
wrote:

Quite a lot of peak demand is supplied by stored water generation (inside
welsh moutains)

No, SOME peak demand is supplied by pumped storage schemes

Thats what I said.
Quite a lot and SOME have the same meaning.

No, they will not routinely use the pumped storage capacity for peak
demand because if a conventional generator is lost or there is an
overhead line circuit fault the system could quite rapidly become
unstable. Some peak demand is met by pumped storage but "quite a lot"
would be very severely overstating the case.

For instance, maybe like today, on a typical winter day with plenty of
spare conventional capacity declared available (no constraints) the
contribution from pumped storage at peak would be NIL (remembering
that like every day there will still be a peak demand that is way in
excess of the minimum demand). On unexpected loss of say 500MW of
generation 30 minutes before a peak then pumped storage generation may
be rescheduled to be 200MW, the rest being achieved by picking up load
earlier on other conventional plant, some of the remainder of the
pumped generation may be spinning in air so that loading can be
rapidly achieved, but it won't generate beyond this because of the
increased costs associated with pumped storage. Basically if demand
can be easily met by conventional plant then it will. The huge peaks
so often referred to in publicity blub are in reality a few times a
decade occurance (football/burying royals etc)

and by gas turbines which spin up in a few seconds.

That has not been the practice in the UK for about 30 years, they
didn't even run during the miners strike in the 80's

That's odd, they built the one three miles from me since then.

No, the last gas turbines added to the UK system would have been at
Torness in around 1988 and Sizewell B in 1996, neither are fuelled by
gas but can run up to be on load in around 2 minutes. A gas turbine
in any historical sense related to the UK power industry was always
fuelled by gas oil, a heavier fraction than aviation fuel, and never,
ever by gas. So unless you live next to those two nuclear sites what
they will have actually built near you is a combined cycle gas fired
station which CANNOT be loaded in anything like a "few seconds"


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