September 24, 08
MIT Students Design “Passive” Solar Power Panels that Track the Sun

A team of three students who designed a system that could allow solar power panels to track the sun without motors or control systems won top honors Thursday -- and a check for $10,000 -- in the finals of a competition aimed at developing innovative energy technologies.

This was the second annual MADMEC -- which stands for Making And Designing Materials Engineering Contest -- and it offered students six categories of engineering challenges related to producing innovative solutions for energy-related problems in the developing world. The contest is co-sponsored by MIT's Department of Materials Science and Engineering (DMSE) and by corporate sponsors Dow Chemical, Saint Gobain and General Motors.

The competition began last spring, and all four of the teams that made it to the finals won prizes, ranging from the $10,000 top award to $1,000 for the fourth-place finishers.

The winning team, called Heliotrope, chose to imitate the way plants track the sun across the sky, by using the difference in temperature between shaded and sunny areas to change the properties of the material supporting solar photovoltaic cells. The system, once built, is completely passive, requiring no power source or electronics to control the movement. Solar cells that track the angle of the sun can be 38 percent more efficient at generating power than those that are mounted in a fixed position, explained team member George Whitfield, a graduate student in DMSE.

The team explored several different variations of the proposed system, using various materials including polymers and bimetallic strips. The system that shows the most promise, they said, mounts solar panels at the top of a curved arch made of a pair of metals such as aluminum and steel, which should be durable enough to withstand the elements with little or no maintenance.

"We wanted to show this concept in action," Whitfield explained as he demonstrated a scale model of the arch by shining a spotlight to warm up one side and cause the arch to bend, tilting the solar panel toward the light. "Our prototypes are cheaper than existing systems" for tracking the sun, he said, and could be built from materials that are readily available in developing nations.

The second-place winner was a team that worked on a way to make inexpensive coatings for windows that would block infrared light, thus allowing daylight through while blocking the sun's heat to reduce the need for air conditioning. Third place went for simple wind generators that could be placed alongside a road to produce electricity from the movement of passing cars. And the fourth prize went to a simple attachment for a bicycle that could allow it to generate electricity to charge batteries, such as those used in the One Laptop Per Child computers.

"I was very impressed with all the entries," said Ned Thomas, DMSE head and Morris Cohen Professor of Materials Science and Engineering. The department will definitely plan on holding another MADMEC competition starting next spring, he said.