9.Energy Payback Time

9.Energy Payback Time-Image

Energy Payback Time (EPT) = Eo/Eg
Eo: Energy consumed to manufacture photovoltaic systems
Eg: Annual energy output by photovoltaic systems

Module Efficiency
Annual Production Scale (MW) 10 30 100
a-Si 8.0% 10.0% 12.0%
poly-Si 11.9% 12.3% 13.2%
Source: PVTEC's "Investigation to Evaluate Photovoltaic Generation"
Report on the investigation commissioned by the New Energy and Industrail Technology Development Organization (NEDO) of Japan during FY1996 

Data provided by Sanyo Electric Co., ltd.

8 Cost of Photovoltaic Cells
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Photocatalyst technology