Granular aerogel windows

Silica aerogel has ideal characteristics for solar thermal applications. High transparency for solar radiation is combined with extremely low thermal conductivity. The chemical company BASF (D) is developing a granular form of aerogel, which will be introduced to the market in the near future. The application potential of this material in window systems was tested as part of a CEC-JOULE project in cooperation with four other industrial companies and two research institutes under the leadership of FhG/ISE in Freiburg. A typical u-value for a double glazed window with a 16 mm thick layer of granular aerogel is 1.0 Wmhighminus2Khighminus1, the solar transmission for diffuse light is about 45 %. Both parameters are variable over a wide range depending on the particle size distribution, thickness of the layer and choice of the filling gas. First window elements were tested in different applications.