CU Boulder and University of Wyoming engineers have successfully scaled up an innovative water-cooling system capable of providing continuous day-and-night radiative cooling for structures. The advance could increase the efficiency of power generation plants in summer and lead to more efficient, environmentallyfriendly temperature control for homes, businesses, utilities and industries.

The new research demonstrates how the low-cost hybrid organic-inorganic radiative cooling metamaterial, which debuted in 2017, can be scaled into a roughly 140-square-foot array—small enough to fit on most rooftops—and act as a kind of natural air conditioner with almost no consumption of electricity.

“You could place these panels on the roof of a single-family home and satisfy its cooling requirements,” said Dongliang Zhao, lead author of the study and a postdoctoral researcher in CU Boulder’s Department of Mechanical Engineering.

The technology, which takes advantage of natural radiative cooling principles, is described today in the journal Joule. “As Earth’s temperature warms due to the absorbed heat from the sunlight during the day, it continuously emits infrared light to the cold universe all the time,” said Professor Ronggui Yang of Mechanical Engineering and lead author of the study. “During the night, Earth cools down due to the emission without the sunshine.”

The researchers’ film-like material reflects almost all incoming sunlight while still allowing an object’s stored heat to escape as much as possible, keeping it cooler than ambient air even in the midday sun. “The material, which we can now produce at low cost using the current rollto-roll manufacturing techniques, offers significant advantages,” said Associate Professor Xiaobo Yin of Mechanical Engineering and CU Boulder’s Materials Science and Engineering Program. “We can now apply these materials on building roof tops, and even build large-scale water cooling systems like this one with significant advantages over the conventional air conditioning systems, which require high amounts of electricity to function,” said Associate Professor Gang Tan of the University of Wyoming’s Department of Civil and Architectural Engineering.