A US research team has developed a paint that cools roofs under direct sunlight.
The research, published in the journal Cell Reports Physical Science, demonstrates that the new material could be used in commercial paints, is less expensive to manufacture, and passively reflects 95.5 percent of sunlight that reaches its surface back into outer space. In contrast, commercial paints currently on the market only reflect 80-90 percent of solar irradiation.
During the summer months and in regions with warm climates, most buildings rely on conventional air conditioning systems. These systems require energy, emit excess heat that transforms cities into "heat islands," and contribute to the climate crisis.
But while scientists have sought to develop radiative cooling paints since the 1970s, previously developed paints have not been capable of reflecting enough sunlight to function as viable, commercializable alternatives to traditional air conditioners.
The Science Daily website cited researcher Xiulin Ruan, professor at the School of Mechanical Engineering at Purdue University in Indiana, as saying: "It is a persistent task to develop a below-ambient radiative cooling solution that contributes to alleviating the global warming effect."
To make the new material, the team used calcium carbonate fillers instead of standard titanium dioxide particles that help minimize the amount of ultraviolet light the paint absorbs, transfers to buildings' walls, and thus raise their temperatures. The researchers also leverage a high particle concentration of 60 percent, which boosts sunlight scattering.
Ruan expects that the technology may benefit a wide range of industries, including residential and commercial buildings, data centers, warehouses, food storage, automobile, outdoor electrical equipment, military infrastructures and utility vehicles. "This paint may even be used to combat climate change since it rejects sunlight and radiates heat into space," said Ruan.