Tuesday, November 30, 2010

Electricity Generation, Transmission, End-Use Efficiency

We use archaic methods to generate, transport, and consume electricity in the U.S.,

photo: treehugger.com

Electricity consumption in the U.S. is really, really inefficient...       
       93% of the coal used to generate electricity is wasted.

Average (2008) coal power plant efficiency:
       ~33% (3,412 [Btu content of a kWh of electricity] / 10,378 [heat content, Btu's]
       ::U.S. Energy Information Administration

(nuclear power stations are about the same efficiency, natural gas is a little better)

In 2007, national-level grid losses were 6.5% of total electricity disposition excluding direct use.
       ::U.S. Energy Information Administration

In general, up to 75% of the electricity used in the U.S. today could be saved with efficiency measures that cost less than the electricity itself.
       ::Wikipedia: Efficient energy use

of every 100 Btu's consumed, we lose: 100 * .33 = 33 * .935 = 30.855 * .25 =
       7.714 Btu consumed for desired uses,
       the rest thrown away

       => 92.29% of coal used to generate electricity is wasted

The Good News... 
All this inefficiency works both ways: for every watt you save through improved efficiency or conservation, you save about 10 Watts at the coal, gas, or nuclear generating plant.

Wind turbines and photovoltaics power the grid at 98% efficiency -- meaning they lose only 2% during generation and conversion to grid voltage -- compared to 92% lost with coal, gas and nukes.

Also, nationwide, coal-fired electric power generation declined 11.6 percent from 2008 to 2009, bringing coal's share of the electricity power output to 44.5 percent, the lowest level since 1978. Coal consumption at U.S. power plants paralleled the decline in generation, dropping 10.3 percent from 2008.

Nukes are losing ground to renewables, too. They are just too slow to bring on line, and way to expensive compared to renewables. Not to mention toxic.

       ::U.S. Energy Information Administration

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