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Proceedings Paper

Optical characterization of solar reflecting surfaces
Author(s): Per Nostell; Arne Roos; Bjorn Karlsson
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Paper Abstract

Commercially available anodized aluminum, vacuum evaporated aluminum foil, and roofing aluminum have been optically characterized in the wavelength range 300 - 2500 nm in a single beam Edwards sphere at oblique angle of incidence (60 degrees). The first two materials are long-term stable, which makes them promising to use as external reflectors. The third one is of interest because of its low cost. A model is proposed for the correction factors for the single beam sphere. A comparison between the single beam sphere and a Beckman 5240 standard spectrophotometer equipped with an integrating sphere was made. The agreement between the measurements was excellent. Furthermore, angle resolved measurements were made with a scatterometer at 633 nm at the incidence angle 60 degrees for all three samples. These data were used in a simulation model to calculate the intensity in the collector plane, assuming a semi-infinite collector and dito external reflector. A calculation of a two-dimensional ideal Lambertian sample was also made. It is shown that optically dull materials, such as roofing aluminum, which has rolling grooves that scatter light, perform equally well as optically smooth materials, provided the scatter is confined to low angles. It is also concluded that integrating sphere measurements of the specular component of diffuse sample in standard spectrophotometers are misleading. The low-angle scattering of diffuse samples also contributes to the intensity in the collector plane and should therefore also be included in the measurement. For Lambertian samples the scatter is too high and such a surface is not a feasible choice of material.

Paper Details

Date Published: 14 October 1997
PDF: 10 pages
Proc. SPIE 3138, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XV, (14 October 1997); doi: 10.1117/12.290207
Show Author Affiliations
Per Nostell, Uppsala Univ. (Sweden)
Arne Roos, Uppsala Univ. (Sweden)
Bjorn Karlsson, Vattenfall Utveckling AB (Sweden)

Published in SPIE Proceedings Vol. 3138:
Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XV
Carl M. Lampert; Claes G. Granqvist; Michael Graetzel; Satyen K. Deb, Editor(s)

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