Purdue researchers Xiulin Ruan (left) and Joseph Peoples point an infrared camera at white paint samples on a rooftop.
Purdue University photo/Jared Pike
Ultra-black coatings and paints like Vantablack have gotten lots of attention in recent years. What the world needs now is to cool off (we’ve hit an unprecedented point in global warming), and a new white paint developed by engineers at Purdue University could help.
The paint reflects 95.5% of sunlight and “can keep surfaces up to 18 degrees Fahrenheit cooler than their ambient surroundings,” said Purdue in a statement this week. That’s something commercial heat-reflecting white paints haven’t been able to achieve.
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The researchers published their results in the journal Cell Reports Physical Science.
“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,” said study co-author Joseph Peoples.
Developing the paint was a multi-year process involving a lot of testing of different paint formulations. The team ultimately hit on calcium carbonate (a compound found in chalk, limestone and seashells) as a main ingredient.
The radiative cooling paint developed at Purdue appears purple on the left, showing a lower temperature in direct sunlight than the commercial white paint sample on the right.
Purdue University image/Joseph Peoples
The engineers compared the new paint with commercial white paint by looking at samples with an infrared camera. The radiative cooling paint appears purple in the image, showing that it stays cooler in direct sunlight.
The team is looking ahead to a future where the paint could be applied to houses, roofs, cars and even roads. It could help reduce the demand for energy-hungry air conditioning in buildings.
“The paint would not only send heat away from a surface, but also away from Earth into deep space where heat travels indefinitely at the speed of light. This way, heat doesn’t get trapped within the atmosphere and contribute to global warming,” said Purdue.
This project is a new entry in a field focused on developing cooling materials, coatings and paints. A passive cooling film created by researchers at the University of Colorado Boulder performs in a similar manner to the Purdue paint by dissipating heat and cooling objects underneath it to below ambient temperatures.
The team is also investigating if they can make other colors with similar cooling properties. Now the new paint just needs a catchy name like Vantablack. How about Wintrawhite?
