Researchers at Oxford University have developed a new adaptable smart window technology that has the potential of reducing the energy usage of the average home by a third.
The technology uses a spectrally tunable low-emissivity coating that can control the amount of heat that comes into a room without affecting the quality of the light that enters.
The thermal energy from the sun’s infrared rays is absorbed by the glass and then is re-emitted as heat. That heat can either be used to warm the room using transparent electrical heaters embedded in the glass or can be reflected away to cool the room. The windows can change according to seasonal needs.
The researchers built a prototype using a material called an active chalcogenide-based phase change material. When it is cold, the infrared rays from the sunlight are harvested and used to heat the building. When it is warm, the new glass can switch state to reflect the heat and reduce the need for air conditioning. The active phase change material is adjustable so that the amount of heat absorbed or reflected can be tuned for precise temperature control. There is essentially no effect on visible light passing through the window. Current low-emissivity glass for windows can reduce heat transfer, but its properties cannot be altered according to seasonal needs.
The researchers estimate that using windows fitted with the new prototype glass – including the energy required to control the film – would save 20 to 34% in energy usage annually compared to double-glazed windows found in many modern homes.
A spinout company from Oxford called Bodle Technologies is collaborating with two existing industrial partners to develop the technology further.
Photo, posted April 26, 2008, courtesy of Lima Andruska via Flickr.