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July 11, 2012

Mass Production Solar Thermal Concentrators Enhanced with Telescope Mirror Technology

With $1.5 million from the Department of Energy, University of Arizona researchers are continuing to improve groundbreaking technology to produce solar electricity at a price competitive with non-renewable energy sources. The "tracker" consists of a steel frame that ultimately will support eight mirrors (each measuring 10 feet by 10 feet), together generating enough electricity to power about four to five homes. The system can also power industrial furnaces that can melt glass.

The Department of Energy recently granted $1.5 million to Angel's research group to extend the mirror-making process to the so-called thermal method for making solar electricity. The mirror-making process will be optimized for cost-efficient mass production. The group has already patented its method for making dish-shaped glass mirrors.

The tracker, as the structure is called, supports two curved, highly reflective glass mirrors, each measuring 10 feet by 10 feet. The tracker is "on sun," converting the hot Arizona summer sun into electrical power.


Regents' Professor Roger Angel has pioneered a new way to make glass mirrors to concentrate sunlight to make electricity (Photo: Patrick McArdle/UAnews)



"Much of what we have learned about making telescope mirrors carries over," Angel said, "how to make them, how point them and how to make them efficient at collecting light. But for this technology, we have to do things ten thousands times cheaper and ten thousand times faster than we do for a telescope."

Angels' team plans to build a furnace that works like a giant toaster oven. Within in a few seconds, heaters placed above the flat sheet of glass turn glowing red, and within a minute the glass will soften and sink into the mold placed underneath.

"Because we are focusing highly concentrated sunlight onto the cells, we had to design an effective cooling system for the cells," Coughenour said. "Otherwise, they would melt within seconds."

A unit of fans and radiators – not unlike the cooling system in a car – is attached to the solar cell array, keeping them about 36 degrees Fahrenheit above ambient air temperature.

"The tracker is fully automated," Coughenour explained. "The system wakes itself up in the morning and turns to the East. It knows where the sun will rise even while it's still below the horizon. It tracks the sun's path during the day all the way to sunset, then parks itself for the night."

In recent test runs, the prototype module generated 2.5 kilowatts of electricity, enough to meet the power demands of two average U.S. households.

"By using mirrors to focus on small but super-efficient photovoltaic cells, we have the potential to make twice as much electricity as even the best photovoltaic panels," Angel said.

How does the solar technology compare to non-renewable energies?

Angel said an array of sun trackers on an area measuring about 7 miles by 7 miles would generate 10 Gigawatts of power during sunshine hours.

Unlike conventional power plants that use steam to power turbines, Angel's photovoltaic prototype uses no water, making it especially suitable for desert regions. The materials are cheap to produce and by concentrating sunlight with mirrors the plant's footprint is smaller than that of PV panel-based plants.

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