Purdue researchers say cooling paint could someday replace AC, slow global warming

Most would agree paint is a fairly low-tech product. Or is it?

After a six-year-long research project, a group of Purdue University engineers insists they’ve created white paint that can lower the temperature in a room as well as any air conditioner and have a positive impact on the earth’s environment by taking the heat from a room and sending it into outer space.

As weird as the idea sounds, the group from Purdue says the paint it has developed can keep surfaces 18 degrees Fahrenheit cooler than their surroundings—without consuming any energy.

The study, which was built on attempts dating back to the 1970s, was supported by Purdue’s Cooling Technologies Research Center and the Air Force Office of Scientific Research through the Defense University Research Instrumentation Program.

Is this too good to be true? Xiulin Ruan, Purdue professor of mechanical engineering who headed up the project, says no.

Ruan

“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,” Ruan said.

According to the researchers, the paint could replace the need for air conditioning by absorbing nearly no solar energy and sending heat away from the building.

The paint would not only send heat away from a surface, but also away from Earth by deflecting it 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, Ruan explained.

“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 the Purdue project as a doctoral student in Ruan’s lab.

Earth’s surface would actually get cooler with this technology if the paint were applied to a variety of surfaces including roads, rooftops and cars around the globe, the researchers said.

The paint developed at Purdue isn’t the first to boast about cooling properties.

But, the Purdue researchers contend, their paint is a cut above commercial heat-deflecting paints currently on the market. Those paints reflect 80% to 90% of sunlight and cannot achieve temperatures below their surroundings.

The white paint that Purdue researchers created reflects 95.5% sunlight and efficiently sends infrared heat out to space, Ruan said.

In a paper published Oct. 21 in the journal Cell Reports Physical Science, the researchers show that compared with commercial white paint, the paint they developed can maintain a lower temperature under direct sunlight and reflect more ultraviolet rays.

“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 doctoral student in mechanical engineering and a co-author of the work.

Cutting down on air conditioning also means using less energy produced by coal, which could lead to reduced carbon dioxide emissions, Peoples said. The researchers have further studies underway to evaluate these benefits.

The team filed an international patent application on the paint formulation through the Purdue Research Foundation Office of Technology Commercialization.

One of the next steps is adding a bit of variety that consumers might like. The researchers are working on developing other paint colors that could have cooling benefits.

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5 thoughts on “Purdue researchers say cooling paint could someday replace AC, slow global warming

  1. In the big steel mills, they heat metals to liquid state in giant vats that are cool to the touch. They are painted with a heat resistant paint. I used this myself probably over twenty years ago to paint exposed hot water pipes along floor baselines. This completely eliminated any loss of heat and any chance of getting burned touching a hot water line. The pipes could even be covered by regular paint in order to blend in. The company did not normally sell to non industrial users and it was expensive. I discussed the possibility of using this paint on the walls and ceiling instead of insulation and they said that it should work. I couldn’t afford it so did not pursue. It significantly lowered the cost of heating the water.

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