Optimization design of CuCrxMn2-xO4-based paint coatings used for solar selective applications

CuCrxMn2-xO4 (x = 0.5, 1) spinels, novel pigments for spectrally selective paints, have been prepared through a sol-gel combustion synthesis process. Thickness Sensitive Spectrally Selective (TSSS) paint coatings, using CuCrxMn2-xO4 (x = 0.5, 1) obtained at varied calcined temperatures (500 similar to 1100 degrees C) as pigment, were deposited on top of aluminum substrates by an cost-effective spray coating method and characterized by reflectance measurements over the spectral range of 0.3-20 mu m. Influence of pigment species and coating thickness on optical properties of paint coatings was investigated. Results suggest that CuCr0.5Mn1.5O4-based coatings are more favorable than CuCrMnO4-based ones and coatings using 700 degrees C calcined CuCr0.5Mn1.5O4 as pigment exhibit the optimum spectral selectivity (alpha(s) = 0.92 similar to 0.93, epsilon(T) = 0.22 similar to 0.31). Difference in powder thermal emittances reveals that suitable pigments can be pre-chosen before fabricating paint coatings to obtain optimum spectral selectivity. Long-term stability tests of the TSSS paint coatings were performed according to the methodology worked out within IEA-SHC Task X and the results confirmed that coatings in this study could be safely used during collector's lifetime without degradation in performance. (c) 2012 Elsevier B.V. All rights reserved.