Okay, it sounds too good to be true. But researchers at the University of Colorado–Boulder claim they have invented a new passive cooling material that can reduce temperatures even in direct sunlight while using no energy and no water. The breakthrough could be applied to power plants, which traditionally generate tremendous amounts of heat and use large quantities of water for cooling. It could also help reduce temperatures of solar panels, which suffer a fall-off in efficiency if they get too hot. “Just by applying this material to the surface of a solar panel, we can cool the panel and recover an additional one to two percent of solar efficiency,” said Yin. “That makes a big difference at scale.”
The challenge for the researchers was creating a material that can reflect incoming solar rays back into the atmosphere while still providing a means of escape for infrared radiation. To accomplish that objective, they embedded visibly-scattering but infrared-radiant glass microspheres into a polymer film. They then added a thin silver coating underneath in order to achieve maximum spectral reflectance.
The new meta-material takes advantage of passive cooling in which objects shed heat naturally in the form of infrared radiation. Such passive radiation is usually cancelled out by even a little direct sunshine. But the researchers have engineered a glass/polymer sheet that is 50 micrometers thick — just slightly thicker than a piece of household aluminum foil — and which can be manufactured using conventional roll to roll techniques.
“We feel that this low cost manufacturing process will be transformative for real-world applications of this radiative cooling technology,” said Xiaobo Yin, co-director of the research and an assistant professor of mechanical engineering at Colorado University–Boulder. “Just 10 to 20 square meters of this material on the rooftop could nicely cool down a single family house in summer,” says Gang Tan, an associate professor in the University of Wyoming’s department of civil and architectural engineering and a co-author of the paper.
“Just by applying this material to the surface of a solar panel, we can cool the panel and recover an additional one to two percent of solar efficiency,” said Yin. “That makes a big difference at scale.” Professor Yang adds, “The key advantage of this technology is that it works 24/7 with no electricity or water usage. We’re excited about the opportunity to explore potential uses in the power industry, aerospace, agriculture and more.”
The plan is to build a 200 square meter demonstration product before the end of 2017 as a way of introducing the material to potential commercial users before developing a business plan for the product. A patent application has already been filed. The breakthrough was funded by a $3 million grant awarded in 2015 by the Energy Department’s Advanced Research Projects Agency-Energy (ARPA-E).
Interestingly enough, Congress intends to eliminate funding for ARPA-E, meaning that America can kiss any more technological advances like this one goodbye while other countries take over the lead in applied research.
Source & photo credit: University of Colorado
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