PV ENERgY ROi
Tracks Efficiency Gains
Energy payback time (EPBT) is the time it takes for a photovoltaic (PV) system to produce all the energy used through- out its life cycle. A short EPBT corresponds to a high energy return on energy investment (EROI); these two indicators are metrics of
sustainability often used in comparative evaluations of different power-generation technologies.
Early assessments in the 1970s and ’80s showed
high EPB T (low EROI) values for prototype systems utilizing large amounts of steel and aluminum and thick silicon wafers produced in small,
inefficient production lines. Now, current commercial PV technologies “pay back” the energy
used in only six months to two years (depending
on the location/solar irradiation and the technology). With their expected life times of 30 years,
their EROIs range from 15:1 to 60:1, signifying
that they return 15 to 60 times more energy than
that used during their fabrication and lifetime.
All energy Inputs, Outputs
SOuTHeRn eneRGY MAnAGeMenT
The EROI of conventional thermal generation from
fossil fuels has been viewed as much higher than
those of photovoltaics; this recently was shown
to be a misconception. Here, the 1.5-megawatt
Sandy Cross Solar Farm was under construction
this spring to serve Elm City, N.C.