‘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.’
Researchers at Purdue University, US have created a white paint that can keep surfaces significantly cooler than the ambient temperature. The paint could reduce the need for air conditioning as it reflects 95.5% of sunlight away from the building and radiates infrared heat. The research has been published in the journal Cell Reports Physical Science.
Over the course of six years the research team looked at more than 100 different combinations of materials, narrowing these down to ten. Next, some 50 different formulations for each material were tested. The final formulation is based on calcium carbonate.
The researchers said that using calcium carbonate, which works as the paint’s filler, allows the formulation to behave essentially as a commercial white paint but with greatly enhanced cooling properties. The calcium carbonate filler absorbs almost no ultraviolet rays due to the so-called large ‘band gap,’ a result of its atomic structure. It also has a high concentration of particles of varying sizes allowing the paint to scatter a wider range of wavelengths.
Xiulin Ruan a professor of engineering at Purdue University said; ‘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.’
It is said that the paint would be cheaper to produce than its commercial alternative and could save around US$1 each day on air conditioning for a typical one-storey house. Cutting down on air conditioning also means using less energy produced by coal, leading to a fall in emissions. The researchers are working to create other paint colours and have filed an international patent application.
DOI: 10.1016/j.crp.2020.100221
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