Smart Window Coatings Control Light And Heat Transmission

Better Smart Windows

UT Austin researchers have discovered a way to improve the efficiency of smart windows. The research paper from members of the Cockrell School of Engineering shows how a new material can selectively modulate visible light and NIR.

Smart windows are optical coatings, which transmit only either of light and sound. The study found that smart window coatings could reduce costs in building heating and cooling applications by allowing occupants to control energy and sunlight transmission more accurately.

As demonstrated by chemical engineering professor Delia Milliron and her team in 2013, a small burst of electricity enables dual-banded nanocrystal materials to switch back and forth, removing the mutual dependency of light and energy transmission through the medium. The latest findings by the team has advanced the study of electrochromic materials by introducing a specific cool mode and a warm mode.

The cool mode material is a potential commercial breakthrough, being able to control the 90% of NIR and 80% of visible light entering through a building window. It certainly helps that an occupant can switch between the modes in a matter of minutes. The material previously used for the same effect took hours to achieve it.

Milliron and a team, including Jongwook Kim and Brett Helms of the Lawrence Berkeley National Lab, came up with a novel architecture for electromagnetic materials which allow a cool mode to reflect near-infrared light while tram sitting the visible part of incident light. The nanostructure, reported in Nano Letters on July 20, has enabled buildings and homes to reduce cooling costs for the summer.

[caption id="attachment_644" align="alignright" width="300"] Commercialization Of Smart Windows[/caption]

According to Milliron, “We believe our new architected nanocomposite could be seen as a model material, establishing the ideal design for a dual-band electrochromic material. This material could be ideal for application as a smart electrochromic window for buildings.”

Milliron’s research paper proved that optical coatings containing doped titania nanocrystals can enable dynamic control over solar radiation conveyance. The material has two different charging mechanisms based on the different levels of voltage applied to it. This allows it to block either visible or infrared radiation. That means an occupant could have more of the heat from sunlight entering through the glass on a sunny winter day, or get the opposite on an overcast summer day.

According to Milliron, “We believe our deliberately crafted nanocrystal-based materials could meet the performance and cost targets needed to progress toward commercialization of smart windows.”