Officially the coolest paint

Guinness record-breaker could slash energy bills in urban areas

The whitest paint on record has been developed by a university research team in the US, who created the bright shade to help combat global warming.

Awarded its own Guinness World Record title in September, the researchers from Purdue University say they developed the paint in a quest to slow global warming.

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

Ruan began developing the paint along with his graduate students with the aim of reflecting sunlight away from buildings.

To make the paint as reflective as possible, they discovered it had to be the whitest shade achievable without compromising paint quality. 

According to Ruan, their formulation reflects 98.1 per cent of solar radiation and also emits infrared heat.

By absorbing less heat from the sun than it emits, surfaces coated with the reflective paint can be cooled below their surrounding temperature without using any power, say the researchers.

This distinguishes it from white paints commercially available today which are only able to reflect 80 per cent to 90 per cent of sunlight, and unable to lower surface temperatures below those from their surroundings.

When we started this project about seven years ago, we had saving energy and fighting climate change in mind

Xiulin Ruan

Mechanical Engineering Professor, Purdue University

According to Purdue researchers, using the new paint formulation on a roof area of about 93 square metres (1,000 square feet) can result in a cooling power of 10 kilowatts.

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

The researchers also demonstrated how the paint handles outdoor conditions using high-accuracy temperature reading equipment called thermocouples. It was able keep surfaces cooler than the ambient surroundings at night and was also able to cool surfaces below the immediate surroundings under strong sunlight around noon.

According to researchers, the paint took six years of research to develop, with many different materials and formulations considered to create a strongly reflective paint that could was compatible with current paint fabrication processes.

“We looked at various commercial products, basically anything that’s white,” says Xiangyu Li, a postdoctoral researcher at the Massachusetts Institute of Technology, who worked as a student in Ruan’s lab.

 “We found that using barium sulfate, you can theoretically make things really, really reflective, which means that they’re really, really white.”

The tech:

The main feature that contributes to its extreme whiteness is the very high concentration of chemical compound barium sulfate commonly used in white cosmetics. It is a metal sulfate that is almost insoluble in water at room temperature.
Because the barium sulfate particles are all different sizes, it causes it to scatter more of the light spectrum from the sun, which makes it ultra-reflective.
Researchers say that while there is some scope to make the paint whiter, this could compromise the quality and application of the paint which may result in it breaking or peeling.

Who funds it:

The research was supported by the Cooling Technologies Research Center at Purdue University and the Air Force Office of Scientific Research.

Is it ready to roll:

Patent applications for the paint formulation have been filed via the Purdue Research Foundation Office of Technology Commercialisation.

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