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Engineering researchers have developed a ‘smart glass’ that could be commercialised as a self-cleaning window with exceptional energy-saving performance.
Tests on prototypes of the glass, created at University College London (UCL), show that it is ultra-resistant to water, so rain hitting the outside forms spherical droplets that roll easily over the surface – picking up dirt and dust and other contaminants and carrying them away. This is due to the conical design of nanostructures engraved onto the glass, trapping air and ensuring that only a tiny amount of water comes into contact with the surface. This, claim the researchers, is different from normal glass, where raindrops cling to the surface, sliding down slowly and leaving marks. The glass also has energy-saving properties, being coated with a very thin 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. The researchers say vanadium dioxide is an abundant material, which, combined with the thinness of its application, makes it significantly cheaper than the silver or gold-based materials currently used in energy-saving windows.
Dr Ioannis Papakonstantinou, from the department of electronic and electrical engineering at UCL, said: “This is the first time that a nanostructure has been combined with a thermochromic coating. The nanostructure amplifies the thermochromics properties of the coating and the net result is a self-cleaning, high-performance smart window.”
The UCL team calculates that the windows could result in a reduction in heating bills of up to 40%. Windows made of the glass could be especially well-suited to use in high-rise office buildings.
Papakonstantinou added: “It’s estimated that, because of the 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.”
Discussions are now under way with glass manufacturers with a view to driving the new window towards commercialisation, including the scaling up of the nano-manufacturing methods that the UCL team has developed to produce the glass.