A smart window grows a silver shield to keep sunlight's heat out
A window can admit welcome daylight but also let in unwanted heat, taxing air conditioning systems. Darkening the glass helps control glare, but the absorption of sunlight warms it. An ideal window would block more incoming heat while also letting trapped heat escape.
A cutting-edge window developed by researchers in China combines the ability to control daylight, privacy, and heat emission. This smart window features a thin, ultrathin layer of silver that is activated by an electric voltage, turning the transparent glass opaque and reflecting incoming sunlight. Simultaneously, a separate infrared-emitting coating allows trapped heat to escape from the window.
In tests, enclosures covered with this prototype window were found to be 3.4°C cooler than those covered with quartz glass, and 4.3°C cooler when opaque compared to quartz glass in its transparent state. When switching from transparent to opaque, the window's cooling effect increased by an additional 2.5°C. The design offers a variety of colors, although these colors cannot be changed on command.
The heat-emitting feature is specifically designed for sky-facing windows, with vertical panes needing a modified surface for optimal performance. While the cooling effect was demonstrated in small experimental setups, further research is needed to determine its performance in occupied buildings over extended periods.
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