Thursday, November 27, 2014

Cool Discovery Blasts Summer Heat into 'the Cold Darkness of the Universe'

In this illustration, the reflective panel is coated with a material invented by Stanford engineers. They designed it to help cool buildings without air conditioning. The material works in two ways--It reflects incoming sunlight (yellow splotch) that would otherwise heat the building. And it sends heat from inside the structure directly into space as infrared radiation (reddish rays). The blue areas on an otherwise warm roof show the cooling effect. (Credit: Fan Lab, Stanford Engineering) Click to Enlarge.
Technology being developed at Stanford University could slash the need for summertime air conditioning, which currently uses up about 15 percent of the $180 billion spent on energy for commercial buildings in the U.S.

Lowering a building's temperature typically requires burning coal or gas to generate electricity, which runs the AC, which lowers the mercury. Far easier and cheaper than burning fuel to cool hot places would be to both stop the heat before it comes in and suck it out when it's too hot.

Research published Wednesday in the journal Nature describes a new, experimental material that can do those two things.  Thin, silicon-based wafers act as both a rooftop mirror, reflecting sunlight and heat skyward, and as a kind of thermal funnel, drawing a building's internal heat up through the roof.  Neither requires a volt of electricity.

The Stanford material can reduce the temperature by up to 5 degrees Celsius (9 degrees Fahrenheit), below the outside air temperature, according to the study.  Experiments have proven successful on an eight-inch-diameter wafer.  The researchers' next job is to scale up the effort.  "We need to get to a point where I can cover part of your roof," said Shanhui Fan, a co-author and professor of electrical engineering.  "So there's still a way to go."

The reflective panel and coating can probably be manufactured using existing fabrication techniques, Fan said.  Scaling-up will require more time, testing and money.  The work so far has been supported by the U.S. Energy Department's high-end research agency, ARPA-E.  The scientists haven't yet formed a company to commercialize their research.

Read more at Cool Discovery Blasts Summer Heat into 'the Cold Darkness of the Universe'

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