It looks like the 2 year payback was talking about energy payback, not economic payback, which is what I and a few other list members were talking about before. Current PV technology also has about a 2 year (actually 0.75 to 4 depending on technology and framing options) energy payback. Actual lifespan of the crystallline PV promises to be much longer than 25 years that most warrantees are. I have a 10 year warranteed module purchased in 1985, and it was still generating over 90% of rated power when it was 20 years old last winter. The theoretical studies I've heard of project near 100 year lifespan for them, based on observed degradation of silicon semiconductor junctions in 24/7 communications equipment in which the junction starts breaking down after 20 to 25 years. Since PV only works a quarter of the time, somewhere between 70 and 100 years seems to be when the junctions will start breaking down.
And I think you've also pointed out another problem with using payback as the metric -- traditional economic accounting doesn't take into account lifespan after payback very well. If two items pay back in 2 years, they seem to be the same, even if only lasts 2 years, and one lasts another 18 years. On 2/18/06, Chris lloyd <[EMAIL PROTECTED]> wrote: > > > How many 50 watt panels do you need... < > > It just stated the production and installation of each 50 watt unit costs > were recouped in 2 years( used in South Africa ), leaving another 15 to 18 > years of useful life before degrading became to great. I think this was the > link I found. > http://www.scienceinafrica.co.za/2004/november/energy.htm > Chris. > > > > Wessex Ferret Club > www.wessexferretclub.co.uk > > > _______________________________________________ > Biofuel mailing list > Biofuel@sustainablelists.org > http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org > > Biofuel at Journey to Forever: > http://journeytoforever.org/biofuel.html > > Search the combined Biofuel and Biofuels-biz list archives (50,000 > messages): > http://www.mail-archive.com/biofuel@sustainablelists.org/ > > > > _______________________________________________ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (50,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/
