Sunlight's heat will cool down youth center at Davis-Monthan

2012-03-10T00:00:00Z Sunlight's heat will cool down youth center at Davis-MonthanMichelle A. Monroe Arizona Daily Star Arizona Daily Star
March 10, 2012 12:00 am  • 

Davis-Monthan Air Force Base will be using Arizona's sun to cool its youth center by summer.

Sopogy Inc., a Hawaii-based energy company, is installing a new type of solar-energy system on the roof of the building that will use heat from sunlight to create chilled air.

The project is part of the military's plan to cut installations' energy costs.

The Department of Defense found that air conditioning accounts for 30 percent to 60 percent of its total facility energy expenditures. Officials decided that switching from fossil fuels to solar heat would help the department meet its renewable-energy targets.

Sopogy's system uses heat from sunlight to create cool air in a process known as absorption chilling.

By May 1, there will be 72 mirrored "micro-concentrated" solar collectors, which are about 12-feet long, weigh less than 200 pounds and will provide about 66 tons of cold air, according to a Davis-Monthan spokesman.

The mirrors focus the sunlight on a pipe filled with a heat transfer fluid that runs to a solar absorption chiller, which reacts to the heat and creates cold air, said Darren Kimura, president and CEO of Sopogy.

The parabolic mirrors are motorized to track the sun's movement, Kimura said. Most air-conditioning systems in the United States use a compressor and a refrigerant, which creates cold air but uses a large amount of electricity. Industrial absorption chillers are typically driven by natural gas or waste heat.

Kimura said Sopogy installed the first air-conditioning system using the technology in 2009 in California.

All of the materials used in the system are nonhazardous, Kimura said. The liquid that reacts with heat to make cold is lithium bromide, which is found naturally in ocean water.

"It takes the same reaction that you would find if you were on a beach on a hot day," Kimura said. "There's the hot sun but then that cool air, the cool breeze, that's the same effect that the chiller has except the chiller is much more concentrated."

Davis-Monthan will be the second military installation to use the technology. The first was Fort Bliss, near El Paso.

The company began working with NASA on the technology years ago, Kimura said, adding that the Pentagon identified Davis-Monthan as a prime site.

Sopogy's system also will provide thermal storage and natural gas as backup for the cooling system on cloudy days.

"This gives you cold air 24 hours, seven days a week," Kimura said, adding that the cost is less than half of the cost of electric refrigeration.

For now, the technology is only for businesses or big buildings like schools.

"We're trying to downsize it so it can be cost-effective in your home and we're not quite there yet," Kimura said.

Michelle A. Monroe is a University of Arizona journalism student and a NASA Space Grant intern. Contact her at mmonroe@azstarnet.com

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