Engineers from Purdue University have created a special type of paint that can keep surfaces up to 7 degrees cooler than their ambient surroundings, similar to how a refrigerator does, but without the drawback of consuming large amounts of energy.
The paint has been in development for the last six years, with the researchers considering over 100 different material combinations before narrowing them down to 10 and testing about 50 different formulations for each material. They finally landed on a formulation made of calcium carbonate, an earth-abundant compound commonly found in rocks and seashells.
The calcium carbonate, used as the paint’s filler, allowed the formulation to behave essentially the same as commercial paint but with greatly enhanced cooling properties. The calcium carbonate fillers also absorb almost no ultraviolet rays due to a so-called large “bandgap,” a result of their atomic structure.
“It’s very counterintuitive for a surface in direct sunlight to be cooler than the temperature your local weather station reports for that area, but we’ve shown this to be possible,” said Xiulin Ruan, a Purdue professor of mechanical engineering.
According to the researchers’ cost estimates, this paint would be both cheaper to produce than its commercial alternative and could save about R16 [$1] per day that would have been spent on air conditioning for a one-story house of approximately 100 Square meters in size.
According to Joseph Peoples, a Purdue Ph.D. student in mechanical engineering and a co-author of the work- “Your air conditioning kicks on mainly due to sunlight heating up the roof and walls and making the inside of your house feel warmer. This paint is basically creating free air conditioning by reflecting that sunlight and offsetting those heat gains from inside your house.”
Take a look at a demonstration of the paints cooling properties below: