Engineers have made the whitest paint ever, and they think it could help fight a warming planet.
This whitest paint surpasses the ultra-white paint that the same group of engineers unveiled at Purdue University in October 2020, and it can cool buildings just as an air conditioner would do, they report in a new study.
If the paint covered a roof of 93 square meters in area, it would have a cooling of about 10 kilowatts. “It’s more powerful than the central air conditioners used by most homes,” said senior author Xiulin Ruan, a professor of mechanical engineering at Purdue University in Indiana. said in a statement.
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The cooling of the paint comes from the impressive ability to reflect sunlight – and therefore infrared heat. Commercially available paints specifically designed to ‘cool’ reflect about 80% to 90% of sunlight, but according to the statement, they can not cool surfaces to below their environment.
The new ultra-white paint, on the other hand, reflects 98.1% of the sunlight – much more than the former record holder, which reflects 95.5%. The paint is the opposite of the ultrablack that researchers created in 2014, called ‘vantablack’, which absorbs 99.9% visible light.
To create the new paint, the team considered more than 100 white materials and then tested about 10 of them in different formulations. Their previous ultrawhite paint was made from calcium carbonate, a compound found in rocks and shells, according to the statement.
The engineers made the new paint with high concentrations barium sulfate, a white, odorless insoluble compound used as a “contrast medium” in X-rays or CT scans by covering the walls of the esophagus, stomach or intestine so that it can be clearly imaged. It is also used to whiten photo paper and cosmetics.
The engineers further increased the reflection of the white paint by changing the particle sizes of barium sulfate. How much light each particle strains depends on its size; according to the statement, the paint according to the statement can spread many different wavelengths.
The group found that their paint surfaces can keep about 19 degrees Fahrenheit (10.6 degrees Celsius) cooler than the surrounding environment at night and 8 F (4.4 C) cooler than their environment while the sun is strong, around the noon.
But the paint also cooled during the winter temperature. When the outside temperature was 6 ° C, the paint lowered the sample temperature by 18 ° C. The researchers have now filed a patent application for this extremely white and cool paint. They also work with a company to make and sell the paint, according to the BBC.
Some cities paint all roofs white to save energy. New York, for example, recently painted 10 million square feet of white roofs, according to the BBC. Scientists are also considering the possibility of using the paint to cool the planet as it covers areas where humans do not live.
“We did a very rough calculation,” Ruan told the BBC. “And we estimate that we only need to paint 1% of the earth’s surface with this paint – perhaps an area where no people live covered under rocks – and that could help fight climate change.”
Still, others were cautious about the findings. The paint is only a small improvement over the commercially available paint, Ronnen Levinson, the leader of the Heat Island Group at the Lawrence Berkeley National Laboratory, told The Washington Post. “Cooling benefits are usually evaluated after a reflective material has been out for several years,” he told the Post. “I do not really know how the ultrabright white will perform then. But from the original features, if it is clean, it is about a ten percent performance improvement over today’s bright white roof coverings.”
The findings were published in the journal on April 15. ACS applied materials and interfaces.
Originally published on Live Science.