
26 Principles of Sustainable Energy Systems
© 2008 Taylor & Francis Group, LLC
costs for manufacturing are the substrate on which the thin lms are deposited, the lm-
deposition process, and facility operation although there can be substantial energy used
in mining and processing rare earth minerals. NREL reported that it takes 120 kWh/m
2
to
make frameless, amorphous-silicon PV modules. Adding another 120 kWh/m
2
for a frame
and support structure for a rooftop-mounted, grid-connected system, assuming 6% con-
version efciency (standard conditions) and 1700 kWh/m
2
per year of available sunlight
energy, the energy payback is about 3 years and the ...