In response to the question about whether renewable energy sources
generate as much energy as goes into their manufacture...
The page <www.pvpower.com/pvfaq.html> 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 <http://www.nrel.gov/ncpv/pdfs/30150.pdf> 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.