Photovoltaic Cells Are Still Very Green, Comparative Test Shows

By Henry Fountain

New York Times
Published: February 26, 2008

Solar power generated by photovoltaic cells is among the greenest of energy options. The cells just sit there, basking in the sun and emitting nothing but electrons.

But cells are manufactured, and the manufacturing process is not benign. Over the life cycle of solar cells — from the mining of raw materials to the finished product — just how green are they?

Vasilis M. Fthenakis of Brookhaven National Laboratory and colleagues have the latest analysis to be published in Environmental Science and Technology. The short answer is that photovoltaic cells are still very green.

The researchers looked at emissions of greenhouse gases and pollutants like nitrogen oxide gases and heavy metals from the manufacture of four types of cells. Most of the emissions are results of the electricity used, and the amounts depend in part on the mix of electricity in the grid, or how much comes from coal plants, hydroelectric, nuclear and the like.

The researchers found that thin-film cadmium telluride cells were the greenest, although the differences among the four types were slight. All told, the researchers say, replacing electrical power from the grid with electricity generated by solar cells results in at least an 89 percent reduction in greenhouse gases and pollutants.