Photo credit: Engineering and Physical Sciences Research Council (EPSRC)
A revolutionary new type of smart window could cut window-cleaning costs in tall buildings while reducing heating bills and boosting worker productivity.
Developed by UCL (University College London) with support from the Engineering and Physical Sciences Research Council (EPSRC), prototype samples confirm that the glass can deliver 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 real cost and sustainability advantages over silver/gold-based and other coatings used by current energy-saving windows.
- Anti-glare: The design of the nanostructures also 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 per cent – compared with the 20-30 per cent achieved by other prototype vanadium dioxide coated, energy-saving windows – with this reduction in ‘glare’ providing a big boost to occupant comfort.
“This is the first time that a nanostructure has been combined with a thermochromic coating. The bio-inspired nanostructure amplifies the thermochromics properties of the coating and the net result is a self-cleaning, highly performing smart window,” said Dr Ioannis Papakonstantinou of UCL.