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Ed Huntress Ed Huntress is offline
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Default New electrical generator


"Bruce L. Bergman" wrote in message
...
On Tue, 18 Mar 2008 05:25:23 GMT, "Leo Lichtman"
wrote:
"Ed Huntress" wrote:


Efficiency of large power-plant generators runs
around 98%, shaft input power to electrical output.

^^^^^^^^^^^^^^^^^^
Do you have any kind of ballpark figure of the efficiency of the
distributionn grid, from the generator terminals to the average consumer?
I
would like to know this, because when people talk about the cleanliness of
electric cars, they frequently forget that there is CO2 coming out the
stacks at the power plant. Steam generation plants run MUCH cleaner than
automotive IC engines, but how much of that advantage do we lose in the
grid?


I've seen figures thrown around in the 40% to 50% range to get the
energy from the burning coal or oil or gas in the powerplant to your
wall socket. The generator at the power plant might be 98% by itself
(2% loss), but the prime mover is a huge loss.


The simplex prime movers, steam or gas turbine, typically run from 37% up to
45% or so efficiency. The newer, "combined cycle" turbines run around 56% -
58%. GE has one that has topped 60%. These are gas turbines that use the
turbine's exhaust to heat a steam boiler, then a steam turbine operating as
the second stage.

So the overall efficiency of these systems run around 0.98 x 0.56, or 55%.
Slightly higher is possible. I see that Wikipedia claims that the overall US
distribution/transmission efficiency, as of 1995, was 92.8% (they report it
as a loss of 7.2%).

(BTW, on a related topic, a solar Stirling at Sandia (I think) just topped
31% efficiency, which is a new record. That's twice the efficiency of the
best photovoltaic cells.)

--
Ed Huntress