World’s whitest paint could eliminate the need for home air conditioning

Xiulin Ruan, professor of mechanical engineering at Purdue University, and his students created the whitest paint ever recorded. (Credit: Purdue University photo / John Underwood)

WEST LAFAYETTE, Indiana (WANE) – Researchers at Purdue University have created the world’s whitest paint, which in a few years could dramatically reduce or even eliminate the need for air conditioning.

The painting won a record in the 2022 edition of the Guinness World Records.

According to Purdue, breaking a record for the whitest paint was not a goal for researchers – limiting global warming was.

“When we started this project about seven years ago, we had energy conservation and tackling climate change in mind,” said Xiulin Ruan, professor of mechanical engineering at Purdue.

Ruan invented painting with his graduate students; the idea was to create a painting that would reflect sunlight away from a building. But making the paint really reflective also made it look really white. The formulation created by Ruan’s lab reflects 98.1% of solar radiation at the same time as it emits infrared heat. Because paint absorbs less heat from the sun than it emits, a surface covered with this paint is cooled below room temperature without consuming energy.

Typical commercial white paint gets hotter than cold. Paints on the market designed to reject heat reflect only 80-90% of sunlight and cannot make surfaces cooler than their surroundings.

Using this new paint formulation to cover a roof area of ​​around 1,000 square feet could result in 10 kilowatts of cooling power, the researchers showed in a published article. “It’s more powerful than the air conditioners used by most homes,” Ruan said.

This white paint is the result of research based on attempts dating back to the 1970s to develop radiative cooling paint as a possible alternative to traditional air conditioners. Ruan’s lab looked at over 100 different materials, narrowed them down to 10, and tested about 50 different formulations for each material.

Two characteristics make this paint ultra-white: a very high concentration of a chemical compound called barium sulfate – also used in photo paper and cosmetics – and different particle sizes of barium sulfate in the paint. The wavelength of sunlight that each particle diffuses depends on its size, so a wider range of particle sizes allows paint to diffuse more of the sun’s light spectrum.

There is a bit of room to make the paint whiter, but not much without compromising the paint.

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