Silica aerogel granulate material for thermal insulation and daylighting

Silica aerogel granulate is a nanostructured material with high solar transmittance and low thermal conductivity. These properties offer exciting applications in building envelopes. One objective of the joint R&D project ISOTEG at ZAE Bayern was to develop and characterize a new glazing element...

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Bibliographic Details
Published in:Solar energy 2005-01, Vol.79 (2), p.131-139
Main Authors: Reim, M., Körner, W., Manara, J., Korder, S., Arduini-Schuster, M., Ebert, H.-P., Fricke, J.
Format: Article
Language:English
Subjects:
Applied sciences
Daylighting
Energy
Exact sciences and technology
Granular silica aerogels
Insulation
Lighting
Nanostructured materials
Natural energy
Optical properties
Silica
Solar collectors
Solar energy
Solar thermal conversion
Thermal properties
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Summary:Silica aerogel granulate is a nanostructured material with high solar transmittance and low thermal conductivity. These properties offer exciting applications in building envelopes. One objective of the joint R&D project ISOTEG at ZAE Bayern was to develop and characterize a new glazing element based on granular silica aerogel. Heat transfer coefficients of less than 0.4 W/(m 2 K) and a total solar energy transmittance of 35% for the whole glazing unit were achieved. The glazing has a thickness of less than 50 mm. Another application for granular silica aerogel is, for example, in solar collectors. The thermal properties of the glazing as well as the optical and thermal properties of the granular aerogels are presented here. The solar transmittance of a 10 mm packed bed of silica aerogel was 53% for semi-translucent spheres and 88% for highly translucent granulate. In our heat transfer experiments the gas pressure, external pressure load, temperature and gas filling were varied. The various thermal conductivity values measured for the glazing and collector applications were compared to the values calculated using two different packed bed models. For the gas-dependent measurements the intergranular voids in the granulate were 1.0 ± 0.1 mm before loading the packed bed, 0.3 ± 0.1 mm at an external load of 3.2 bar (3.2 × 10 5 Pa) and 0.6 ± 0.1 mm after release. A direct radiative conduction of λ direct = 4.5 ± 0.5 × 10 −3 W m −1 K −1 was obtained.
ISSN:0038-092X
1471-1257
DOI:10.1016/j.solener.2004.08.032