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 excess heat going
up the stack and out the cooling towers, and all the little motors and
fans keeping the big motor running that do all the pumping and blowing
and cooling and lubricating and stack filtering...

Then you have the transmission lines, with little bits siphoned off
in resistive loss and flash-over of insulators and dielectric losses
in underground cables. And every transformer along the way taking a
small bite, whether it's stepping voltage up or down.

A nibble here, a bite there, and suddenly it's half gone.

The only real exception is hydroelectric, wind turbines, geothermal,
and the like. There are still losses, but gravity and wind and magma
are free (in limited quantities). And building the facilities to
exploit them safely (Hoover Dam) costs quite a bit, and has to be
figured into the 'cost' of that power.

(Versus the cost of exploiting them *un*safely - St. Francis Dam,
Saugus CA, built 1926 failed 1928, killed thousands when it did...)

This is why when you need bulk heat for hot water or cooking or
space heat, you buy the fuel (coal, oil, propane, natural gas, wood)
and burn it yourself on site. You have to deal with the equipment,
sure, but you also cut out that 50% loss middleman that is always
involved with electric heat.

-- Bruce --