Who has the best-reasoned estimates of time periods for energy returned on energy invested for solar?
I have been looking at the scientific literature on solar- how much energy does it take to make and install a panel, how much energy does the panel return over its lifetime, what is the energy payback period. (Along the way I got sidetracked into the time factor - how often does the energy get paid back.)
My initial thoughts were very optimistic. I got excited by an article at:
https://cleantechnica.com/2018/02/03/solar-power-can-pay-easily/
That first link makes a very big claim - namely that solar pays back power with a very good "energy payback period."
Edit: a condensed version of the same optimistic story is at:
https://cleantechnica.com/2018/03/25/solar-power-energy-payback-time-now-super-short/
I looked at claims from NREL such as:
https://www.nrel.gov/docs/fy04osti/35489.pdf
and (because a lot of science papers cited this as a source) I looked at claims from Europe such as:
http://www.ecn.nl/docs/library/report/2007/e07026-LCIdata-cSiPV-pubv2_0.xls
And as far I could tell, a solar panel is pure win. It take a few years to pay back the energy required to make it, and then it is pure energy "profit" until the end of its service life. But then doubt set in. A lot of science papers are based on the XLS spreadsheet linked above, and that spreadsheet claims that it is full of guesswork and estimates and trust in the manufacturers. Obviously, solar panel manufacturers might exaggerate their efficiency, and those exaggerations might get worked into the spreadsheet, and thence to the scientific literature. Furthermore, estimates of solar installations might fail to recognize relevant expenses of embodied energy. Maybe solar requires a lot of steel, aluminum, concrete, gravel, and water, but maybe the estimates for solar energy payback don't factor those in properly. Therefore my question is - who has the best reasoning? Whose estimates are the most comprehensive? Whose model fits the reality most accurately?
I would really love to see a retrospective study on solar panel installation, where someone put in a big solar installation and tracked all the inputs, outputs, waste factors, and unexpected outages. However, I have not yet found anything like that. I have found pro-solar folks who are busy installing panels (who don't have numbers on their "energy payback period"), and I have found anti-solar folks who claim that it is all a bunch hippie malarkey (and who refuse to believe any hopeful claims about "energy payback period"), but I have not found anyone who says, "Solar is not perfect, it has some inefficiencies, it has some unexpected flaws, and here are the numbers that measure our experience." I don't know if the scientific literature is the best place to look for such information. Helpful comments would be appreciated. Thank you.
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