Thin-film has best solar carbon footprint, says study

Not all PV technologies are manufactured the same way, and some are more environmentally-friendly than others.

That's the conclusion of a new report from the Environmental Science & Technology journal, which found that each PV technology has its own life-cycle assessment profile.

Though new PV solar cell technologies have doubled solar cell efficiency in the last three years, concerns have been raised regarding the environmental friendliness of the processes by which many of these devices are made.

Based on production data taken from over a dozen solar companies between 2004 and 2006, researchers from Brookhaven National Laboratory and Columbia University compared the manufacturing processes of single-crystal, multicrystal, ribbon silicon solar cells and thin-film cadmium-telluride solar cells.

The assessment also took into account the support materials needed such as cables, and the energy sources used in each manufacturing process. Different values were assigned to electricity generated from sources such as coal and natural gas. The researchers also looked at the use of each system over a 30-year period.

The researchers found that thin-film cadmium-telluride solar cells had the best life-cycle profile. Even though the process emitted the heavy metal cadmium, it still had a lower overall level of “harmful air emissions” than the other PV technologies in the study, they said.

Among the companies that make cadmium-telluride solar cells are Q-Cells, First Solar, PrimeStar Solar and Bloo Solar.

"Overall, all PV technologies generate far less life-cycle air emissions per GWh than conventional fossil-fuel-based electricity generation technologies," they wrote in the report. "At least 89% of air emissions associated with electricity generation could be prevented if electrity from photovoltaics displaces electricity from the grid.

Vasilis Fthenakis, a Brookhaven scientist and lead author of the paper, noted that one factor the report did not include was end-of-life and recycling data. "Those studies are not yet completed," he said in a statement, but added "it's a safe assumption ... that recycling will make the emissions profile better, [and] the feasibility of recycling is here."

The report can be found here.

Cleantech developments making news in the past 24 hours

• AES raises $1.58B with China Investment

View the last week of cleantech developments here | Subscribe to full feed