Smart Window – University College London demonstrates three benefits

“This is the first time that a nanostructure has been combined with a thermochromic coating. The bio-inspired nanostructure amplifies the thermochromic properties of the coating and the net result is a self-cleaning, highly performing smart window,” said Dr. Ioannis Papakonstantinou of UCL.

The University College London (UCL) developed a new type of window. They call it smart window. In fact, it is not the entire window which is smart. To be precise, the focus is on the window glass. The scientists improved the glass extensively with a pencil-like engraved nanostructure onto the glass and demonstrated three benefits with their prototypes making the glass ‘smart’.

Anti-glare

Due to the applied nanostructure engraved onto the glass, their smart window (glass) has anti-reflective properties. They compare it with the eye of a moth which looks matt and black to protect against predators. The advantage is that less than five percent of the internal light in a room can be reflected. This increases the comfort for building occupants. Other prototypes like vanadium dioxide coated, energy-saving windows achieve 20-30 percent.

Self-cleaning

The engraved nanostructure makes the smart window (glass) resistant to water. Hitting rain drips off easily and rolls over the surface in the form of spherical droplets. At the same time, the raindrops pick up dirt and carry it away. Normal glass is different. Raindrops cling to the surface before they slide down more slowly. After drying, one can see their marks.

Energy-saving

The smart window (glass) is coated with a very thin film of vanadium dioxide. The layer is 5 – 10 nanometres thick. According to EPSRC (Engineering and Physical Sciences Research Council), it stops thermal radiation and prevents heat losses during cold seasons. During hot periods, it reduces the cooling demand because less infrared radiation is entering the building. The use of vanadium is a real advantage compared to other coatings. Vanadium dioxide is not expensive. It is an abundant element and occurs naturally in about 65 different minerals.

Dr. Ioannis Papakonstantinou of UCL, project leader, explains: “It’s currently estimated that, because of the obvious difficulties involved, the cost of cleaning a skyscraper’s windows in its first 5 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. As the trend in architecture continues towards the inclusion of more glass, it’s vital that windows are as low-maintenance as possible.”

It is estimated that this smart window (glass) can come onto the market within 3-5 years. The success depends on industrial interests.

Dr. Papakonstantinou says: “We also hope to develop a ‘smart’ film that incorporates our nanostructures and can easily be added to conventional domestic, office, factory and other windows on a DIY basis to deliver the triple benefit of lower energy use, less light reflection and self-cleaning, without significantly affecting aesthetics.”

The research project ended in September 2015 and has been funded with around £100,000 from the Engineering and Physical Sciences Research Council (EPSRC).