University College London (UCL) researchers have developed a ‘smart’ window that promises to cut window-cleaning costs in tall buildings while reducing heating bills and boosting worker comfort, and they are now talking with manufacturers about commercialising the innovation.
The windows use nature inspired nanostructures that mimic the eyes of moths to cut glare, save energy and clean themselves. The prototype glass, which has been developed with support from the Engineering and Physical Sciences Research Council (EPSRC), has been found to delivers three key benefits:
- Self cleaning: The window is ultra-resistant to water, so rain hitting the outside forms spherical droplets that roll easily over the surface – picking up dirt, dust and other contaminants and carrying them away. This is due to the pencil-like, conical design of nanostructures engraved onto the glass, trapping air and ensuring only a tiny amount of water comes into contact with the surface. This is different from normal glass, where raindrops cling to the surface, slide down more slowly and leave marks behind
- Energy saving: The glass is coated with a very thin (5-10 nanometre) film of vanadium dioxide which during cold periods stops thermal radiation escaping and so prevents heat loss; during hot periods it prevents infrared radiation from the sun entering the building. Vanadium dioxide is a cheap and abundant material, combining with the thinness of the coating to offer cost and sustainability advantages over silver/gold-based and other coatings used by current energy-saving windows
- Anti-glare: The design of the nanostructures gives the windows the same anti-reflective properties found in the eyes of moths and other creatures that have evolved to hide from predators. It cuts the amount of light reflected internally in a room to less than 5% – compared with the 20-30% achieved by other prototype vanadium dioxide-coated energy-saving windows – with this reduction in ‘glare’ boosting occupant comfort.
The research team calculates that the windows could result in a reduction in heating bills of up to 40%, with the precise saving depending on the exact latitude of the building where they are incorporated.
UCL project leader, Dr Ioannis Papakonstantinou, said: “It’s currently estimated that, because of the obvious difficulties involved, the cost of cleaning a skyscraper’s windows in its first five years is the same as the original cost of installing them. Our glass could drastically cut this expenditure, quite apart from the appeal of lower energy bills and improved occupant productivity thanks to less glare.”
The university is in discussions with UK manufacturers with the aim of commercialising its innovation. Professor Ivan Parkin of UCL said, “The key to this will be scaling up the nano-manufacturing methods we have developed to produce the glass, as well as the process of coating it in vanadium dioxide.” It is believed that smart windows could begin to reach the market within around three to five years.
UCL PhD student and lead researcher, Alaric Taylor added: “In addition to developing the glass, we hope to create a ‘smart’ film that incorporates our nanostructures and can easily be applied to conventional windows using a DIY approach. We’d develop it so the film still delivers the same benefits as the glass without significantly affecting aesthetics.”
Image: Nanostructures engraved onto glass. Image courtesy Alaric Taylor