GREENING SUN WITH CHEMISTRY AND RECYCLING

Making Solar Panels Greener; Producing photovoltaic panels more sustainably will require reducing energy consumption, toxic substances
Sarah Everts, February 21, 2011 (Chemical & Engineering News)

"…[I]t’s worth taking a measured look at the environmental impact of photovoltaic technology from cradle to grave…[Makers of] crystalline silicon-based photovoltaic solar panels, which currently boast about 80% of the global market…have borrowed much of their technology from the electronics industry, which relies on an abundance of chemicals and energy-intensive steps that pose risks to human and environmental health.

"..[T]hey must instead choose more environmentally friendly manufacturing processes and plan for the panels’ safe disposal…[C]ompanies are increasingly setting up programs that will collect and recycle panels after their 20–25-year lifespan, with some businesses committing to not sending their products to developing nations in which other electronic waste is processed unsafely…"

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"…[C]ompanies are looking to reduce the amount of energy required to produce photovoltaics, thereby improving the bottom line and environmental profile of manufacturing. Researchers in both academia and industry are also starting to scrutinize the photovoltaic production process to figure out which chemicals could and should be replaced.

"…[C]rystalline silicon must be in use about two years before the cumulative energy they supply to the grid balances the energy required to produce them—the so-called energy-payback time…Many scientists have tried developing more-energy-efficient ways to purify and crystallize silicon…But none of the fledgling processes outperform the industrial status quo…[W]orse, much of the crystallized silicon goes to waste…Finding a way to recycle…would reduce waste across the industry…Turning a cut wafer into a usable solar panel involves a series of wet-chemical etching steps…[M]ore benign chemicals…[are being tried but few] perform to industry standards…"

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"[C]rystalline silicon dominates the photovoltaic market…[but] other technologies, particularly thin-film cadmium-telluride-based photovoltaic cells, are gaining a significant foothold. CdTe photovoltaic panels pay back their consumed energy in about a year, twice as fast as crystalline silicon photovoltaic cells…[and] don’t require as many chemical processing steps…[but] [c]admium is a [toxic] carcinogen…And tellurium is so rare that some people consider it unsustainable…

"As companies figure out how to establish effective recycling programs for retired photovoltaic panels, as well as how to make those panels in more sustainable ways, they will have to continue to balance priorities that are sometimes at odds. Improving the energy efficiency of cells will make the energy payback time shorter…[but require mopre chemicals and water.] Resolving these challenges will ensure that photovoltaics don’t just produce renewable energy but are themselves renewably produced."