Cranking up the air conditioner is one way to keep buildings cool, but it guzzles energy. Passive materials can regulate interior temperatures more efficiently, and now scientists in South Korea have developed a new coating that keeps glass much cooler, while still being transparent.
Windows are great for filling rooms with natural light, but they’re also a major portal for messing with temperature. When it’s cold out, about 30% of the interior heat can escape through the windows, while in hotter times about 76% of the sunlight that hits windows enters as heat.
That’s why it’s important to plug this gap, ideally without ruining what makes windows appealing in the first place. A new coating, created by researchers at POSTECH and Korea University, could help do just that.
The team designed a material that can radiate heat away while allowing visible light to pass through. It’s made up of three layers that have different roles. The topmost layer is polydimethylsiloxane (PDMS), which emits far-infrared radiation, which is felt as heat. The center is a thin layer of silver, which reflects most of the rest of the solar spectrum – however, it’s full of micro-scale holes, to allow visible light to pass through.
The third layer is what’s called a Bragg mirror, which has been specially designed to reflect wavelengths of the near infrared spectrum, which constitute most of sunlight’s heat. This is made up of alternating layers of titanium dioxide and magnesium fluoride.
In tests, the new material was found to keep a glass surface an astonishing 22.1 °C (39.8 °F) cooler than glass coated with just PDMS. That’s among the largest cooling effects we’ve seen with this kind of coating.
The hope is that this material could be applied to windows to keep building interiors cooler without sacrificing light, reducing our reliance on heating and cooling systems that can chew through electricity.
“This technology is ready for mass production and has significant potential in architecture and environmental applications,” said Professor Junsuk Rho, corresponding author of the study. “Most importantly, it efficiently dissipates heat and reduces energy consumption, positioning it as a key technology for a sustainable future.”
The research was published in the journal Advanced Functional Materials.
Source: POSTECH