salve,
complimenti x il forum+sito e una domanda:

qual é il break-even energetico di un pannello PV in anni?

qui si parla di un ottimistico 4 anni tendente a 1 in dipendenza dal tipo di silicio. La fonte sembra godere di una certa autorevolezza  
http://www.nrel.gov/docs/fy04osti/35489.pdf

"Today’s PV industry generally recrystallizes any of several
types of “off-grade” silicon from the microelectronics
industry, and estimates for the energy used to purify and
crystallize silicon vary widely. Because of these factors,
energy payback calculations are not straightforward."

"best estimates of electricity used to make nearfuture, frameless PV were 600 kWh/m2
for single-crystalsilicon modules and 420 kWh/m2
for multicrystalline
silicon. Assuming 12% conversion efficiency (standard
conditions) and 1,700 kWh/m2
per year of available sunlight energy (the U.S. average is 1,800), Alsema calculated
a payback of about 4 years"

saluti, J.