Most people are familiar with the idea that painting the roof of a building white can help cool it down by reflecting off sunlight. How much temperature reduction is possible, however, depends on the type of paint used. Radiant cooling paints have been used to enhance this effect since the 1970s. However, no colors could cool below ambient temperature. Maybe until now.

Engineers at Purdue University have developed a new formulation for white paint that can lower the surface temperature by up to -7 degrees Celsius below the ambient temperature. In addition, this impressive cooling effect is achieved without consuming any energy. That could make it a valuable weapon in the fight against climate change.

"That sounds pretty straightforward, but it actually works," Xiulin Ruan, Purdue professor of mechanical engineering, told Digital Trends. “Firstly, our paint can reflect 95.5% sunlight, which means that it is almost not warmed up by sunlight. There is also radiant heat in the infrared, and this heat passes through the atmosphere, which has a transparent window in the wavelength range of 8 to 13 micrometers, directly into space, which is an extremely cold heat sink at -270 degrees Celsius. (With) these two factors together, space can cool the paint below the ambient temperature. "

The color formulation has several variations of normal colors, such as: B. Calcium carbonate fillers instead of titanium oxide, and a variety of particle sizes, which makes sunlight more effective. Ruan suggested that the paint could have a wide range of possible uses. In addition to cooling buildings (which may not need AC power), it can also be used in large data centers, utility systems, automobiles, outdoor electrical equipment, and virtually anywhere else you want cooling to take place.

"Not only does it save energy, it (can) reduce the CO2 emissions associated with producing (this) saved energy," said Ruan.

He noted that the team is actively looking for ways to bring this to market. "We are already in the process of commercializing the technology through discussions with major manufacturers," said Ruan. "Some of the next steps include studying long-term durability and developing colored coolants."

An article describing the work was recently published in the journal Cell Reports Physical Science.

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