A new type of white paint tested by researchers was found to have amazing prowess to cool buildings without the need for an air conditioner, and thereby cut tonnes of emissions.
The special white paint, developed by researchers at Purdue University in Indiana, harnesses the power of ‘radiative cooling’ which passively cools buildings by refracting sunlight at much higher rates than conventional paints.
In testing, the new product was able to reflect back 95.5% of the sunlight and drop the internal temperatures of upto 1.7C as compared to ambient air-con systems.
“Our paint shows a high solar reflectance of 95.5% and a high normal emissivity of 0.94 in the sky window,” the searchers stated in the journal Cell Reports Physical Science.
Buildings, both commercial and domestic, around the world contribute hugely to the global emission budget. Cooling, heating, and lighting in towers, skyscrapers emit 28% of the global human-induced CO2, World Green Building Council data says.
This huge addition to carbon from buildings comes as a result of the burning of fossil fuels and coal that drive the heaters, ACs, and power the lightings in such buildings.
Researchers have in the past tried to overcome the need to cool building interiors sans emitting methods, like paint that could cool enough to end the reliance on traditional methods.
A number of refractive paints have been developed over the years for exterior application, but none were able to reduce temperatures on the inside enough.
But this new invention is apparently solving the problems. During testing, the scientists behind the product say after they put a painted object under the sun, the internal temperature dropped by 1.7C below the ambient.
And the same dip in temperature during the night went down by 10C below the ambient temperature, Prof Xiulin Ruan, from Purdue University in Indiana, who’s an author on the study, told the BBC.
“This is a significant amount of cooling power that can offset the majority of the air conditioning needs for typical buildings.”
But how does this white paint works?
Technically, the technology masters full daytime below-ambient cooling — a process where the sun’s rays are reflected significantly back into the environment, and the painted surface shows high emissivity which is reflecting energy as thermal radiation.
To achieve the feat, scientists have simply added one ingredient in the white paint, which is calcium carbonate to the mix. A high concentration of this substance enabled the paint to reflect back over 95% of sunlight.
Prof. Xiulin Ruan, explained since sunlight has multiple wavelengths, it is imperative to inculcate substances that are capable of reflecting back those rays of different wavelengths.
“We know that each particle size (of calcium carbonate) can only scatter one wavelength effectively so we decided to use different particle sizes to scatter all the wavelengths,” he told the BBC.
The paint, which lacks any metallic content, could find a wide range of applications in sensitive locations like data centers, and telecommunications towers.
But the paint will take some more development before it is commercially available. Researchers will now test its long-time reliability and efficiency before you can paint your home with it.