Highly insulating aerogel glazing for solar energy usage

Granular silica aerogels have been integrated into highly-insulating translucent glazing. This work was performed within the large R&D project ISOTEG pursued by the ZAE Bayern. To avoid settlement of the granules, which often occurred in earlier glazing concepts and even caused destruction of the glazing, the granules were sandwiched between a double skin sheet made of PMMA. The sheet was mounted between two low-e coated glass panes. To optimize the thermal insulation, krypton was used as filling gas. This construction allows to achieve heat transfer coefficients of less than 0.4 W/(m 2 K). Optimized granular layers provide high solar transmittance of 65% for a thickness of 20 mm. Thus a total solar energy transmittance of 35% for the whole glazing unit is achieved. The glazing has a thickness of less than 50 mm. Such aerogel glazings can be integrated into solar wall systems or used as lightscattering daylighting elements with vanishing energy losses over the heating period even for north facade integration. Optical and thermal properties of the developed granular aerogels as well as the thermal properties of the whole glazing unit are reported.