Another way to make solar panels: grow 'em

Bye-bye ingots and wafers, hello silicon garden. A Colorado startup and DOE claim to slash the cost, waste and energy of making silicon solar cells. They're starting production soon.

NREL scientists Chaz Teplin (l) and Howard Branz figured out how to grow silicon on metal foil.

There's always room for more in the cornucopia of solar energy technologies.

First there was wafer-reliant crystalline silicon solar. Then came glass-based thin film solar, followed by plastic thin film. Throw in  concentrated photovoltaics , plus all the variations of " solar thermal " that create steam to drive turbines, and you'd think the basket was full.

Alas, researchers in Golden, Colorado will soon grow solar panels, a technique that could slash the costs, waste and energy requirements of solar cell and panel production.

That's right, grow.

The U.S. Department of Energy's National Renewable Energy Laboratory in Golden has figured out how to deposit a gaseous form of silicon onto an inexpensive metallic foil that acts as a seed crystal and gives root to adult silicon capable of handling photovoltaic chores. NREL uses chemical vapor deposition.

Golden-based startup firm Ampulse Corp. is installing a trial production line at the NREL facilities, using a foil substrate developed by DOE's Oak Ridge National Laboratory, according to a write-up on the NREL website.

Once the pilot is complete, "Ampulse plans to design a full-scale production line to accommodate long rolls of metal foil," NREL says.

Conventional techniques typically produce wafers that are 10 times thicker than necessary (although my SmartPlanet colleague Kirsten Korosec has just posted a story about a company, Twin Creek Technologies, that has learned how to slice thinner wafers ). By growing the solar cells rather than cutting wafers off of an ingot, Ampulse can make them only as thick as necessary, which is 10 microns or less, according to NREL.

The Ampulse technique uses the same gaseous form of silicon as conventional techniques. But as an energy saver, it eliminates an extra 1000 degree C step and a 1400 degree C step, both of which conventional production uses to convert, refine, melt and recrystallize the silicon into ingots.

The process "goes straight from pure silicon-containing gas to high quality crystal silicon film," says Brent Nelson, operational manager for the project at NREL.

By avoiding ingots, Ampulse saves a bulk of material, because solar producers typically lose a lot of silicon to "sawdust" when they cut ingots into wafers. NREL claims the loss is 50 percent of the ingot in conventional techniques.

Both Ampulse and conventional manufacturers start with silicon created by heating up sand and carbon at 2,000 degrees C, so the Ampulse process doesn't completely eliminate energy intensive stages in the value chain. That's a reminder that, like other forms of "carbon-free" energy such as nuclear and wind, the life cycle of solar is not completely free of global warming-inducing CO2 emissions.

Such is the cost of breathing!

Photo from NREL.

More solar technology, and CO2 in the energy value chain, on SmartPlanet:

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