Matt wrote:
On Tue, 24 Oct 2006 08:27:07 +0100, Edward W. Thompson
wrote:

On Mon, 23 Oct 2006 13:25:06 +0100, Matt
wrote:

On Sun, 22 Oct 2006 23:38:05 +0100, wrote:

The original Q was about electrical generation. the UK's Thermal generation I
would imagine is no more than 30% efficient.
Slightly above mid 30's would be the worst thermal generation in the
UK, typical of 60's and 70's built coal and oil fired generation. Top
end for these is about 38%.

High 40's to mid's 50's is typical of 1990's gas fired generation.
Very recent gas fired generation is even higher, 60% for instance in
the case of Baglan Bay.
You are not comparing like to like re Baglan Bay. This is a CGT
system of limited capacity (500MW) I believe whereas the large steam
turbine stations are 3000MW plus with efficiencies, as you say, in the
upper 30s. I stick my neck out and say that steam turbine stations do
not exceed 40% efficiency (latent heat and all that jazz!).

The size of the boiler/turbine unit "generator" makes absolutely no
difference to it's efficiency. For a long, long time 120MW units
built in the 50's were (marginally) 2nd only to the 660MW units built
in the early 80's and notably above the majority of 500MW units built
in the 60's. Design and operating regime pay a much bigger part than
sheer size. There is no need to stick you neck out "steam turbine
stations" by which I *think* you might mean oil or coal fired
generation in the UK has an absolute ceiling at around 38%, basic
thermodynamics won't allow any more.

They will.

There is no theroetical limit apart from the difference between the
actual working fluid temperatures and the exhaust temperatures. With
condensing turbines and superheated front ends you can get a lot higher
than that - at a cost in complexity and of course corrosion issues.

If you tap off the low grade heat for heating buildings etc, of course
you can do even better.


More efficient heat recovery,
use of process heat, and the use of low pressure turbine blade
materials that don't get mashed to bits by wet steam were the big
changes when gas fired generation appeared.


Gas plants are built for cheap, not for efficiency.