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The lowest-cost solar panels on the market are made using thin-film solar cells that cost about 80 cents per watt of electricity they produce; costs for other types of cells can be as high as $2 per watt. Those prices are too high if solar power is to displace coal and natural gas. But Chris Rivest has a plan to reduce the price of solar cells to well under 50 cents per watt.

Rivest cofounded SunPrint in 2008 to build cheaper solar cells using a process called acoustic printing, originally developed by Xerox for ink-jet printers. Focusing a sound wave onto a pool of ink causes droplets to spatter onto a nearby surface. Rivest and his cofounders designed and built an acoustic printer to deposit layers of ink containing cadmium telluride, one of the most cost-effective solar-cell materials available, on glass, plastic, or metal. Because acoustic printing provides finer control than other printing methods, the technique uses 50 percent less cadmium telluride and eliminates further processing steps that require expensive tools. Rivest expects commercial production of solar panels to begin within a year or so. --Neil Savage