Influência do tipo de camadas e variações de temperatura nas propriedades ópticas de superfícies absorvedoras solares

Abstract

Solar energy can be used to generate electricity, through photovoltaic modules, or used to heat water, through solar collectors. However, the thermal efficiency of the solar collector depends on the selective coverage that covers the collector's absorber plate. These coatings are called selective surfaces and are materials that focus on having a high absorption capacity for solar radiation and low emissivity in the infrared. This work aims to evaluate the influence of the types of materials used in the production of solar absorbing surfaces (SSA) and their influence on the optical and morphological properties. For this purpose, chromium based SSA with and without anti-reflective layer will be produced by the Sputtering technique, in four different configurations, deposited on a stainless-steel substrate AISI 304 treated with electropolishing. The SSA will be characterized, optically and microstructurally via UV-Vis and FTIR Spectroscopy, Profiling and X-Ray Diffraction. The addition of an anti-reflective layer of chromium oxide or silica obtained satisfactory results, increasing the absorptivity by 2.34% and 1.66%, respectively. The best film produced was chromium-based with an anti-reflective layer of chromium oxide with heat treatment of 100 °C, obtaining an absorbance of 99.13%, with a roughness of 0.01 μm, however, X-Ray Diffraction (XRD) exhibited only characteristic peaks of the phase (Fe-γ austenite), corresponding to the phase present in the steel substrate. The results obtained in Optical Profiling indicate that the heat treatment did not provide high changes in the surface of the sample, since the films have high average absorbances above 97%, however the absorbance of the samples increases according to the decrease in roughness for most of the treatments, except for C1, which had high roughness and high absorbance.