from the April 2009 issue

Ben Gurion University researchers develop energy efficient windows

Researchers at Ben-Gurion University of the Negev (BGU) in Israel have developed a highly efficient window technology that is warm in winter and cool in summer.

The window has a system of reversible panes that allows passive heating in winder and reduces solar heating in the summer.

The system consists of two panes - one clear airtight pane and a smaller tinted pane with openings at the top and bottom. The two panes are attached to a single frame that can be swivelled one way or the other depending on the season or the daily weather.

In winter or on cold days, the tinted pane faces indoors and absorbs short-wave solar radiation transmitted through the clear pane. The tinted pane emits warmth into the room and the openings at the top and bottom also heat circulating air.

At other times when warm, the window is swivelled so that the tinted pane faces outwards and absorbs incoming solar radiation before reaching the interior-facing clear pane. Now the openings at the top and bottom of the tinted pane have a cooling effect instead.

"The 'Seasons Window' features the only glazing system that permits effective passive heating in winter without glare or high radiant temperature near a window and reduces unwanted solar gains in summer without obstructing the view outdoors," says researcher Evyatar Erell.

For the moment, the window will only be available in Israel through aluminium company Alubin. But the technology would save energy in any sunny region with distinct hot and cold seasons. require about five cents per kilowatt/hour.

Reprinted from the Israel High-Tech & Investment Report April 2009

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