Harnessing sunlight on the cheap

[tinrobot]

For a project that could be on the very cutting edge of renewable energy, this one is actually decidedly low tech--and that's the point.

A team of students, led by mechanical engineering graduate student Spencer Ahrens, has spent the last few months assembling a prototype for a concentrating solar power system they think could revolutionize the field. It's a 12-foot-square mirrored dish capable of concentrating sunlight by a factor of 1,000, built from simple, inexpensive industrial materials selected for price, durability and ease of assembly rather than for optimum performance.

Rather than aiming for a smooth parabolic surface that would bring the sunlight to a perfect focus, the dish is being made with 10-inch-wide by 12-foot-long strips of relatively low-cost, lightweight bathroom-type mirror glass. The frame is assembled from cheap aluminum tubing, with holes drilled in precise locations using a simple jig for alignment, so that the struts can be assembled into a framework that passively snaps into just the right parabolic curvature.

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Ahrens believes that such a design could quickly produce both hot water for space heating and electricity for the grid at prices that would be competitive today, unlike conventional photovoltaic systems that are still far too pricey for baseload generation. "In the sunbelt, our dish would make about 10,000 peak watts of heat and 3,500 peak watts of electricity," he says. Deployed in large numbers, the systems could make a big difference: "One square meter of concentrator is worth about one barrel of oil per year," he says.

"It's designed for long life--we hope they will last more than 30 years with good maintenance--and for indigenous manufacturing in the developing world with minimal tooling," Ahrens says. "We want to get something up that will be kind of viral and be widely adopted around the world."

http://web.mit.edu/newsoffice/2008/solar-dish-0506.html