The direct conversion of sunlight into electricity via photovoltaic (PV) modules is widely considered a potential solution to environmental problems such as acid rain and global warming caused by conventional electricity generation. But PVs, like any technology, can only be considered "green" if their net environmental benefits exceed their net environmental costs. Accounting for these costs and benefits can be approached by using life cycle analysis (LCA). LCA is a methodology for documenting the entire history behind goods or services and assessing each component's contribution to a total environmental impact.

A study conducted by Michael E. Murray ('04) and Professor John Petersen on the Lewis Center's PVs found that the Oberlin installation pays back the environmental costs of construction (energy and carbon dioxide) early in its useful life, but it cannot pay back financial investments in the economy as it is currently structured.

The environmental benefits from using solar electric systems are derived in a negative sense: by not using conventional forms of electricity. Solar energy generated from the roof displaces conventional electricity and, over time, adds to the PVs' environmental value. The graph below depicts electricity sources for different locations -- the United States as a whole; Oberlin, Ohio; and the Lewis Center -- over three different timescales. The U.S.'s and Oberlin's fuel sources are essentially constant over time; note Oberlin's heavy dependence on coal as an electricity source, which is the most polluting of all fossil fuels.

"Payback and Currencies of Energy, Carbon Dioxide and Money for a 60-kW Photovoltaic Array":

Michael Murray's and Professor John Petersen's paper for the 2004 American Solar Energy Society annual conference (103KB PDF)
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Michael Murray's 2004 Honors Thesis (1.4MB PDF, more detailed content than above)
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