Heat, light-controlling windows to become reality soon

Thanks to the development of new materials, smart windows which can automatically control heat and light passing through them may soon become a reality, shows research.

Researchers at the University of Texas at Austin are one step closer to engineering materials that would allow windows to allow light without transferring heat and, conversely, to block light while allowing heat transmission.

By allowing indoor occupants to more precisely control the energy and sunlight passing through a window, the new materials could significantly reduce costs for heating and cooling buildings.

The scientists have engineered two new advancements in electrochromic materials -- a highly selective cool mode and a warm mode -- not thought possible several years ago.

The cool mode material is a major step toward a commercialised product because it enables control of 90 percent of near infrared light (NIR) and 80 percent of the visible light from the sun and takes only minutes to switch between modes.

This could help reduce energy costs for cooling buildings and homes during the summer. The researchers reported the new architecture in Nano Letters.

"We believe our new architected nanocomposite could be seen as a model material, establishing the ideal design for a dual-band electrochromic material," said lead researcher professor Delia Milliron.

"This material could be ideal for application as a smart electrochromic window for buildings," Milliron added.

In a second research paper, Milliron and her team have reported how they can achieve optical control properties in windows from a single-component film.

The concept includes a simple coating that creates a new warm mode, in which visible light can be blocked, while near-infrared light can enter.

This new setting could be most useful on a sunny winter day, when an occupant would want infrared radiation to pass into a building for warmth, but the glare from sunlight to be reduced.

In this paper, published in the Journal of the American Chemical Society, Milliron proved that a coating containing a single component - doped titania nanocrystals - could demonstrate dynamic control over the transmittance of solar radiation.

Because of two distinct charging mechanisms found at different applied voltages, this material can selectively block visible or infrared radiation.

"These two advancements show that sophisticated dynamic control of sunlight is possible," Milliron said.