New ‘cooling glass’ sends heat into space

Developed at the University of Maryland (UMD, the microporous glass coating can lower the temperature of the material beneath it by 3.5oC at noon, and has the potential to reduce a mid-rise apartment building’s yearly carbon emissions by 10 per cent, according to the research team led by Distinguished University Professor Liangbing Hu in the Department of Materials Science and Engineering.

The team’s findings are detailed in a paper published in Science.

In use, the coating first reflects up to 99 per cent of solar radiation to stop buildings from absorbing heat. It then emits heat in the form of longwave infrared radiation into the cold universe, where the temperature is generally around -270oC.

In a phenomenon called ‘radiative cooling’, space acts as a heat sink for the buildings; they take advantage of the new cooling glass design along with the so-called atmospheric transparency window - a part of the electromagnetic spectrum that passes through the atmosphere without increasing its temperature - to deposit large amounts of heat into the cold universe.

“It’s a game-changing technology that simplifies how we keep buildings cool and energy-efficient,” said Assistant Research Scientist Xinpeng Zhao, the first author of the study. “This could change the way we live and help us take better care of our home and our planet."

According to UMD, the new glass can withstand exposure to water, ultraviolet radiation, dirt and flames, enduring temperatures of up to 1,000oC. Furthermore, the glass can be applied to surfaces including tile, brick and metal.

The team used finely ground glass particles as a binder, allowing them to avoid polymers and enhance its long-term durability outdoors, Zhao said. They chose the particle size to maximise emission of infrared heat while simultaneously reflecting sunlight.

"This 'cooling glass' is more than a new material - it's a key part of the solution to climate change,” said Hu. “By cutting down on air conditioning use, we're taking big steps toward using less energy and reducing our carbon footprint. It shows how new technology can help us build a cooler, greener world."

Mechanical engineering Professor Jelena Srebric and Professor Zongfu Yu from the Department of Electrical and Computer Engineering at the University of Wisconsin-Madison are co-authors of this study.

The team is now focusing on further testing and practical applications of their cooling glass. They have established CeraCool to scale up and commercialise it.