What is the energy payback for PV?

Abstract

Producing electricity with photovoltaics (PV) emits no pollu-tion, produces no greenhouse gases, and uses no finite fossil-fuel resources. The environmental benefits of PV are great. But just as we say that it takes money to make money, it also takes energy to save energy. The term " energy payback " captures this idea. How long does a PV system have to operate to recover the energy—and associated generation of pollution and CO 2 —that went into making the system, in the first place? Energy payback estimates for rooftop PV systems are 4, 3, 2, and 1 years: 4 years for systems using current multicrystal-line-silicon PV modules, 3 years for current thin-film mod-ules, 2 years for anticipated multicrystalline modules, and 1 year for anticipated thin-film modules (see Figure 1). With energy paybacks of 1 to 4 years and assumed life expectancies of 30 years, 87% to 97% of the energy that PV systems generate won't be plagued by pollution, green-house gases, and depletion of resources. Based on models and real data, the idea that PV cannot pay back its energy investment is simply a myth. Indeed, researchers Dones and Frischknecht found that PV-systems fabrication and fossil-fuel energy production have similar energy payback periods (including costs for mining, transportation, refining, and construction).