Emissions from photovoltaic life cycles

[jpak]

(Nanowerk News) New photovoltaic technologies, such as the recent introduction of thin-film cadmium–telluride (CdTe) materials, have nearly doubled the efficiency of solar cells within the past few years. But the methods of making the materials used for photovoltaic cells, whether from silicon, metal, or other material, have raised doubts about the environmental friendliness of these passive energy collectors. Purifying and producing silicon uses a lot of water and energy, and refining zinc and copper ores to get Cd, Te, and other elements creates metal emissions and an energy sink—all of which increase the technology's environmental footprint.

A new life-cycle assessment (LCA) of some of the leading photovoltaic technologies, published in ES&T ("Emissions from Photovoltaic Life Cycles"), shows that some may be better than others, particularly when it comes to emissions over their lifetimes. Overall, however, replacing traditional electricity grids fueled by gas, coal, and other means with photovoltaics would cut emissions of greenhouse gases, particulate matter, and other pollutants by 89–98%. Rooftop panels could further reduce emissions because of the resulting decrease in transmission lines and other infrastructure. But each form of photovoltaics has a different LCA profile, specific to heavy-metal emissions and electricity use in particular, the new analysis shows.

Led by Vasilis Fthenakis of Brookhaven National Laboratory and Columbia University, the LCA includes information from databases of more than a dozen active solar companies and provides a complex snapshot of the state of the solar industry up to 2006. Fthenakis and co-workers compared data from companies that make single-crystal, multicrystal, and ribbon silicon solar cells, all of which have different efficiencies in converting sunlight into electricity. They also compared these products with the thin-film CdTe photovoltaic systems manufactured by fast-growing Arizona-based First Solar.

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Ken Zweibel, president of Colorado-based PrimeStar Solar, notes that even if China were to adopt photovoltaics wholesale, produced entirely with coal-powered electricity, new solar materials would allow products with 30-year lifetimes to make up for those emissions in several years. Plus future technologies could further shift emissions: "The field is changing fast," adds Zweibel, who recently coauthored a "solar grand plan" with Fthenakis in Scientific American.

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[skids]

1. Link? Looks like a good one for the bookmarks file. n/t

[jpak]

2. Acckk! link here (thanks)

http://www.nanowerk.com/news/newsid=4496.php

:hi:

[eppur_se_muova]

3. Thanks, I was wondering about just this question. nt

[diane in sf]

4. It's reality like this that keeps me somewhat optimistic we might get past

our current evolutionary bottleneck.