Windows as a heat source instead of an energy thief

Windows are important for letting in light and for the aesthetics of the buildings we live and work in. The downside is that big glass surfaces steal heat and waste large amounts of energy. Now a research team has found a solution to the problem.

Since glass surfaces are becoming more and more expansive in architecture, maintaining the temperature balance of buildings is a challenge. A large amount of heat is lost because big glass windows act as “cold bodies”. Generally, if it’s freezing outside and +20 °C indoors, the temperature of the window is about +16 °C. In cold weather regular glass remains cold even in direct sunlight. Getting a window to both let in light and retain heat has proven to be a challenge.

Alexander Dmitriev, professor of physics, and his research colleagues got an idea. They thought that if windows could become warm from sunlight through nanotechnology, the warmth of rooms could be maintained better.

“Windows still have to be transparent and not change the colour of objects indoors. So we created so-called nano-antennae that absorb sunlight and generate high-energy electrons that heat the glass. But the glass is still mostly transparent and has a colour rendering index of close to one hundred per cent.”

The researchers designed special nano-antennae for sunlight made from cheap and common nickel material and placed them across the glass surface. “We already can warm up the glass more than eight degrees Celsius in direct sunlight,” Alexander Dmitriev says. “By optimising the antennas, we can generate even more heat.”

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