25 November 1992 Calorimetric measurements of the total hemispherical emittance of selective surfaces at high temperatures
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An apparatus is presented for measuring the hemispherical emittance (epsilon) in a temperature range of 100 - 400 degree(s)C. It is designed especially for samples with low values of (epsilon) between 0.015 and 0.15. The error margin lies around 6% of the measured value. A polished stainless steel sample (PTB, Braunschweig, Germany) serves as reference reproducing the PTB-results within 2%. Measurements of solar selective absorbers, a TiNxOy-Cu tandem absorber, a multilayer cermet absorber, and an Al2O3-Ni-Al absorber have been carried out. The values of (epsilon) range between 0.02 and 0.15 for 100 degree(s)C and between 0.035 and 0.3 for 400 degree(s)C. TiNxOy-Cu achieves the lowest values in both cases. The effects of temperature on the optical constants in the near IR of TiNxOy-Cu tandem layers are discussed. The results of measurements indicate a shift from dielectric to metallic behavior with rising temperature.
© (1992) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
A. Brunotte, A. Brunotte, Michel P. Lazarov, Michel P. Lazarov, R. Sizmann, R. Sizmann, "Calorimetric measurements of the total hemispherical emittance of selective surfaces at high temperatures", Proc. SPIE 1727, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XI: Selective Materials, Concentrators and Reflectors, Transparent Insulation and Superwindows, (25 November 1992); doi: 10.1117/12.130497; https://doi.org/10.1117/12.130497


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