U.S. students are developing cost-efficient solar power

08 May 2008
U.S. students are developing cost-efficient solar power

A team of students at the Massachusetts Institute of Technology have spent the last few months assembling a prototype for a concentrating solar power system they think could revolutionize the field by harnessing solar energy on the cheap.

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.

Students mounting solar
frame. Photo / Donna Coveney

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.

The control mechanism, which allows the dish to track the sun automatically across the sky, is also remarkably simple--photocells mounted on each side of the dish with opaque baffles, which cast a shadow on the cell when it drifts out of alignment, connect to a simple circuit that turns on small electric motors to push the dish back into the right position.

According to the team leader, mechanical engineering graduate student Spencer Ahrens, the team is keeping careful track of all the costs for parts and the time spent on assembly, to provide a baseline for figuring out what an eventual large-scale field of such dishes would cost. "We're using all commodity materials that are all in high production," he says.

That's in stark contrast to most attempts to build solar dish concentrating systems, which have tended to use expensive custom-made equipment to achieve high efficiency.

Ahrens thinks that in mass production the dishes can be competitive in cost with other energy sources and could produce heat for space heating and electric power at the same time.

The prototype isn't quite finished yet, because of delays in getting the mirror glass shipped from the factory.

"The details of assembly and operation could well present some unexpected stumbling blocks, as is so often the case with new designs. Still, they're smart kids, they know what they're doing. That's how you learn," says Jefferson Tester, HP Meissner Professor of Chemical Engineering, who has been advising the student-led group.

Source and more information

MIT Edu