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MIT team plays with fire to create cheap energy

New solar dish harnesses power from heat – at a size and cost that make soaking up the sun even more attractive.

By Staff Writer for The Christian Science Monitor / June 18, 2008

Spencer Ahrens, Matthew Ritter, and Eva Markiewicz created a solar dish that boils water (or sets wood ablaze) at a cost cheaper than heat from gas, oil, or coal.

Melanie Stetson Freeman – Staff


Cambridge, Mass.

Out on a lawn at the Massachusetts Institute of Technology with joggers and traffic passing nearby, Spencer Ahrens is demonstrating what looks like either the future of solar power – or perhaps a death ray.

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Thrusting a 12-foot board up into the air in front of a large mirror-covered satellite-type dish, Mr. Ahrens, an MIT graduate student, waves the board, looking for an elusive sweet spot where reflected sun rays converge.

With three student teammates looking on, he steadies the board once its tip begins to glow. Shining white in the reflected solar rays, the wood suddenly bursts into flames. Students laugh as smoke billows in the breeze.

This burning-board trick may seem like a YouTube stunt, but it’s actually a visceral demonstration of a device with a serious purpose: to make super-cheap solar heat.

From garage inventors to government scientists, many have tried to make a solar dish that focuses sun rays to generate power. What makes this student project different is not that they’ve done it – but that they’ve done it so cheaply, building this dish with off-the-shelf parts.

“A lot of good people have built working dishes, but generally they’re more expensive, more complex, and harder to build,” says Matthew Ritter, an Olin College of Engineering student who’s also part of the team. “We use widely available materials – that’s our breakthrough.”

The student team has already formed a company – Raw Solar – that they hope will one day have an assembly line cranking out cheap solar dishes that individually or in large arrays could supply affordable heat to a college campus, suburban home, or third-world village.

A few minutes later, the real demonstration begins. A pole protrudes from the front of the solar dish – similar to the rod that sticks out from satellite-TV dishes. Wrapped around the end of it is spiral tubing, which the team fills with water from a garden hose. With the dish swiveled to face the sun, the tubing glows white. Boiling water sputters from the far end of the hose, which lies in the shade beneath the dish.

The secret: frugal design
Materials and construction are fairly simple. Aluminum tubing is riveted to a steel cross bracing. Affixed to that frame are strips of mirror from a local supply house. High-heat barbecue paint coats the coil collector at the apex of the pole.

“Small solar thermal is a kind of power that has really been traveling under the radar,” says Micah Sze, an MIT business school graduate tapped to help market the technology. “People have been focusing on electricity from the sun, not the heat market. We think there’s an opportunity to supply heat to large institutions like universities and someday individual homes.”