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Re: energy payback time for renewable


Denmark now generates 50% of its electricity from wind....


-----Original Message-----
From: Daniel Schroeder [mailto:DSCHROEDER@CC.WEBER.EDU]
Sent: Wednesday, June 13, 2001 10:36 AM
Subject: energy payback time for renewables

In response to the question about whether renewable energy sources
generate as much energy as goes into their manufacture...

The page <> quotes a 1997 article that
arrived at energy payback times of 2.5 to 5 years for photovoltaics,
depending on location. (I haven't looked up the actual article.)

The document <> has a table
on page 31 comparing the manufacturing-related energy input for
various types of generators. Photovoltaics come out lowest among
the technologies listed, at only 2 kwh per watt installed. However,
when you figure that a PV system is operating near its peak capacity
only a rather small fraction of the time, the comparison of sources
will look quite different. Still, PV seems to compare favorably
to coal.

For wind, the Danish manufacturers' association quotes an energy
payback time of two to three months in a typical site. See
<>. The full study
supporting this claim is at <>.

Dan Schroeder
Weber State University