ASU students use sun power to beat heat - East Valley Tribune: Business

ASU students use sun power to beat heat

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Posted: Wednesday, May 11, 2005 6:57 am | Updated: 7:38 am, Fri Oct 7, 2011.

Arizona State University graduate students are finding ways to use the sun to cool down, displaying five solar-related projects Tuesday that can lead to more energyefficient methods of cooling.

The architecture students created the projects for a class in experimental analysis, led by professor David Tait.

This is the 13th year his students have produced such projects in the hands-on research class.

The presentation was held on the roof of the architecture building on ASU’s main campus, and provided snacks and refreshments, including garlic bread baked in Tait’s solar oven.

"The point of the class is just to experiment," said graduate student David Carroll. "The point isn’t to prove that something works. If it doesn’t work, it’s just as good."

Carroll, along with partner Shreshth Nagpal, developed a photovoltaic skylight that cools the air inside a building and provides electrical power. It might someday lower consumers’ monthly power bills.

The skylights, or Building Integrated Photovoltaic modules, convert the sun’s rays into electricity while heating up the air inside at the same time, forcing the hot air to rise and exit through a controllable vent. This creates negative pressure inside the space, so warm, outside air then enters through a vent with moist evaporative pads that cool the air to a comfortable temperature. The skylights then heat up the air and circulate it again.

Carroll said although the initial construction cost to install the skylights might be higher, the amount of money saved on electricity and cooling helps it pay for itself in time.

Students Rashimi Sonal, Shivani Shah and Khanin Hutanuwatr looked to nature for inspiration for their breathing canopy.

"We are copying how a tree performs," Sonal said.

Leaves provide cooler air under the shade of a tree through a process called "evapotranspiration." The grad student trio tried to mimic this effect. They constructed the covering using a plastic material for the top, small water tubing in the middle, and a breathable material underneath.

As the sunlight warms the top plastic layer, the heat causes the water in the middle to evaporate, and the moisture seeps out of the bottom layer of material, cooling the occupants underneath.

The students’ data shows the canopy can help reduce 95-degree outside temperatures to 72 degrees under its shade. The canopy, which may be the concept closest to commercial application, also conserves more water than the mister systems in use on many restaurant patios.

When this experiment was conducted in past years, the light-rail planners were interested in the concept of the breathing canopy for its stations, but dropped the project because there was not enough data to support it. The graduate students, however, hope to continue to make modifications and collect enough data over the summer to be included in the light rail’s plans once again.

The other projects experimented with soil insulation, a cool tower and a green roof to try to find alternative methods of cooling buildings and public places.

Most of the projects have been accepted to appear at the Passive Low Energy Architecture conference in Lebanon. The students will conduct more testing this summer and write a full paper to submit to the conference.

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