Goodbye air-conditioner — world’s whitest paint can cool down your house

Researchers at Purdue University in the US state of Indiana have created the world’s whitest paint, capable of cooling down buildings.

The new ultra-white paint was developed by mechanical engineering professor Xiulin Ruan and his graduate students over seven years.

The idea of the project was to find a solution that could save energy and fight climate change. Should the paint be adopted widely, it could do just that.

The researchers claim their paint can deliver a 10kW cooling power when covering a surface area of about 1,000 square feet (92.9m2).

“That’s more powerful than the air-conditioners used by most houses,” Ruan stated.

To achieve this performance, the team had to make the paint as white as possible to maximise reflectivity, in the process claiming the Guinness World Records record for the world’s whitest paint colour.

The paint reflects 98.1% of solar radiation while emitting infrared heat at the same time.

Because it absorbs less heat than it emits, surfaces coated with the paint are cooled below the surrounding temperature.

Xiulin Ruan, a Purdue University professor of mechanical engineering, and his students have created the whitest paint on record. (Purdue University photo/John Underwood)

Although there are certain commercial heat-reflecting paints on the market, all of them become hotter when exposed to the sun.

They can typically reject only 80-90% of sunlight and don’t make surfaces cooler than the surrounding air.

The researchers based their work on previous attempts dating back to the 1970s to develop a radiative cooling paint that could replace air-conditioning.

The paint has two features that make it ultra-white — a very high concentration of the chemical compound barium sulfate, which is also used in photo paper and cosmetics, and different particle sizes of barium sulfate in the paint.

“What wavelength of sunlight each particle scatters depends on its size, so a wider range of particle sizes allows the paint to scatter more of the light spectrum from the sun,” the researchers stated.

The researchers have filed patents for the paint formulation and have partnered with a company to scale up production.

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Goodbye air-conditioner — world’s whitest paint can cool down your house