First spectral emissivity study of a solar selective coating in the 150-600°C temperature range

A complete experimental study of temperature dependence of the total spectral emissivity has been performed, for the first time, for absorber-reflector selective coatings used in concentrated solar power (CSP) systems for energy harvesting. The coating consist of double cermet layers of silicon oxide with different amounts of molybdenum over a silver infrared mirror layer. The experimental measurements were carried out by a high accurate radiometer (HAIRL) with controlled atmosphere in the mid-infrared and for temperatures between 150 and 600 C. The spectral emissivity is nearly constant in this temperature range. Therefore, the temperature dependence of the total emissivity is given by Planck function. These results were compared with those obtained with the usual calculus using room temperature reflectance spectrum. Finally, the performance of the coating was analyzed by comparison of coated respect to non-coated stainless steel.
This work was financially supported by the European Commission (project HITECO FP7-ENERGY-2010-1Collaborative N. 256830) the Spanish Ministry of Science and Innovation (projects FUNCOAT CSD2008-00023, RyC2007-0026) and program ETORTEK of the Consejería de Industria of the Gobierno Vasco in collaboration with the CIC-Energigune Research Center. L. González-Fernández acknowledges the Basque Government the support through a Ph.D. fellowship.