Smart windows that can let in only light and no heat on a sunny day or block light while allowing heat transmission are being developed by American researchers.
Relying on what the researchers call dual-band electrochromic materials, the windows would give occupants a greater control over energy and sunlight passing through the window. The temperature inside a house equipped with such windows would therefore be more stable and less energy would be needed for heating and cooling.
Dual-band electrochromic materials consist of two types of nanocrystals with distinct optical properties. While one material allows selective control of visible light, the other focuses on the heat-producing infrared part of the spectrum.
The team from the University of Texas first engineered such a material in 2013 and has since enhanced its performance to the extent that they are now able to start considering practical implementation.
"We believe our new architected nanocomposite could be seen as a model material, establishing the ideal design for a dual-band electrochromic material," said Delia Milliron, professor of chemical engineering at the Cockrell School of Engineering of the University of Texas, who first described a dual-band electrochromic material in an article in Nature in 2013.
"This material could be ideal for application as a smart electrochromic window for buildings," she said about the latest advance.
The nanocrystal material could be switched between the two states for visible and infrared light control using a weak electrical impulse.
The material can block about 90 per cent of near-infrared light and 80 per cent of the visible light from the sun. The switch between the two modes takes only a few minutes whereas in the earlier versions it required hours.
The researchers are now working to produce a similarly structured nanocomposite material by simple methods suitable for low-cost manufacturing.