There is a paper on the IEEE web site at:
http://www.spectrum.ieee.org/select/0199/powsb1.html
That contains this paragraph:
"Two recurring questions as to the economic viability of PV--land
requirements and energy payback--have readily calculable
answers and are not insuperable obstacles. PV fields covering
250 000 km2, or less than 10 percent of Nevada, could meet the
entire U.S. demand for electric power. As for energy payback,
the conclusion in Vienna was that today's silicon technology, over
a 30-year operating life, should deliver four to six times the
energy consumed in manufacturing the PV system. Technology nearing
production can push the factor to 10 or more. "
Thare aren't any sources to back up these claims, but I'll accept
them as-is and quit questioning the pay-back period for now.
==>paul
