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Proceedings Paper

Optical characterization platform for transparent insulation materials in solar energy
Author(s): Werner J. Platzer
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Paper Abstract

The precise optical characterization of transparent insulation materials used in windows, flat- plate collectors or for transparent insulation of buildings, is an important step to design solar collector and daylighting systems with these materials and to estimate energy benefits, peak loads, efficiencies, and different potential risks such as overheating, thermal damage or glare. Physically the aim is clear: Angle-dependent transmittance and reflectance properties for the solar and visible wavelength ranges yield the necessary information for the engineer to enable him to design a good system. However, it is far from trivial to obtain these data with sufficient precision for the rather different materials. The class of TIMs poses mainly the following problems, originating in their special character. TIMs often: (a) have a rather coarse structure, (b) show considerable scattering, (c) are relatively thick, (d) are spectrally selective, (e) and are not always rotationally symmetric. Therefore the optical measurement process has to: (a) integrate over a relatively large sample area (b) be able to detect intensity scattered in the sample (c) take into account the complex structure of the sample (d) and weight the different spectral bands correctly. We have set-up a set of radiation sources and integrating detector spheres which are able to measure directional-hemispherical and hemispherical-hemispherical reflectance and transmittance (hence also absorptance) for the visible and the solar wavelength range. This was possible by applying a PTFE-based coating to the spheres, having a unique spectrally flat response over the whole range, and using non-selective broadband detectors. Careful design tried to optimize integrating sphere geometry. Moreover, spectral measurements between 285-1100 nm are possible with an optical multichannel analyzer utilizing glass fiber optics. The whole experimental set-up will be presented and discussed together with representative results.

Paper Details

Date Published: 9 September 1994
PDF: 12 pages
Proc. SPIE 2255, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XIII, (9 September 1994); doi: 10.1117/12.185408
Show Author Affiliations
Werner J. Platzer, Fraunhofer-Institut fuer Solare Energiesysteme (Germany)

Published in SPIE Proceedings Vol. 2255:
Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XIII
Volker Wittwer; Claes G. Granqvist; Carl M. Lampert, Editor(s)

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