Smart glass cuts AC bills

Chemists at University College London have coated glass with an intelligent material that lets light through but impedes the flow of heat depending on the temperature. The coating is produced by atmospheric pressure chemical vapor deposition (CVD) of tungsten doped vanadium(IV) oxide from VOCl3, water and WCl6. The coated glass allows visible wavelengths of light through at all times but reflects infrared light when the temperature rises above 29°C. The change is due to an electronic rearrangement that switches the vanadium dioxide derivative between acting as a metal and a semiconductor. The UCL research team, led by Ivan Parkin, suggests that the coating's ability to switch between absorbing and reflecting means it could be used to allow the sun's heat to warm the occupants of buildings in cooler conditions. However, when temperatures soar room heating would be reduced by up to 50%.