Engineers at Purdue University in Indiana have created the world’s whitest shade of white paint that can help combat global warming. The new super-white paint reflects 95.5 percent of the sunlight that hits it. It remains 10 ° C cooler at night than the ambient temperature and 1.7 ° C lower in daylight. The research was published in the journal Cell Reports Physical Science.

This paint cools the building even without the use of air conditioning

When such a paint is applied to a building, it cools it even more than the ambient temperature. This paint will reduce cooling costs and thus energy consumption. If this paint were to be used en masse, carbon dioxide production would be significantly reduced. Entire cities could cool down significantly without consuming any electricity. So far, many cooling paints have been developed in the past to reflect sunlight. Such paints mostly reflected light with the help of glass, Teflon or titanium dioxide. However, they were expensive and impractical. Commercial “heat rejecting paints” currently on the market reflect only 80% -90% of sunlight and cannot achieve temperatures below their surroundings.

The paint is made of cheap and easily accessible material

Purdue scientists have developed a new composition. Instead of titanium dioxide, they used calcium carbonate fillers. This material is cheaper, more abundant and absorbs less ultraviolet light, so it is cooler. The paint contains a particle concentration of 60 and uses particles of different sizes so that sunlight is better scattered.

“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.

An infrared camera image shows that white radiative cooling paint developed by Purdue University researchers (left, purple) can stay cooler in direct sunlight compared with commercial white paint. (Purdue University image/Joseph Peoples)

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.

“We’re not moving heat from the surface to the atmosphere. We’re just dumping it all out into the universe, which is an infinite heat sink,” said Xiangyu Li, a postdoctoral researcher at the Massachusetts Institute of Technology who worked on this project as a Ph.D. student in Ruan’s lab.

“An infrared camera gives you a temperature reading just like a thermometer would to judge if someone has a fever. These readings confirmed that our paint has a lower temperature than both its surroundings and the commercial counterpart,” Ruan said.

The paint has excellent results

The white paint that Purdue researchers created reflects 95.5% sunlight and efficiently radiates infrared heat. The new paint was tested in direct sunlight and it remained 1.7 ° C (3 ° F) cooler than the ambient temperature, exhibiting a cooling power of 37 W / m2. At night, the paint dropped to 10 ° C (18 ° F) below the ambient temperature. To make the effect visible, one surface was painted with normal white and the other surface with a new super white paint.

“Our paint is compatible with the manufacturing process of commercial paint, and the cost may be comparable or even lower,” says Xiulin Ruan, an author of the study. “The key is to ensure the reliability of the paint so that it is viable in long-term outdoor applications.”

According to the researchers ’cost estimates, this paint would be both cheaper to produce than its commercial alternative and could save about a dollar per day that would have been spent on air conditioning for a one-story house of approximately 1,076 square feet.

“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 Joseph Peoples, a Purdue Ph.D. student in mechanical engineering and a co-author of the work.

The paint will now be examined for commercial use.

Source: Purdue University