Study of surfaces, produced with the use of granite and titanium, for applications with solar thermal collectors

Abstract

The present work consisted in obtaining and studying selective surfaces for applications in low-cost flat plate solar collectors, using residues from the granite industry. Five different surfaces were studied, varying the percentage by weight: 100% granite powder, 75% granite powder + 25% titanium oxide, 50% granite powder + 50% titanium oxide, 25% granite powder + 75% titanium oxide and 100% titanium oxide. For the tests, an experimental wooden bench was built, and it was possible to simulate the conditions of a flat plate solar collector. For characterization of the surfaces, SEM techniques, infrared analysis and UV-VIS absorbance determination were used, as well as graphs with surface temperatures and with radiation in the sun tests. The efficiency of the surfaces was determined by the ratio of the absorptivity through the emissivity, as well as the trademark MRTiNOX. An efficiency of 23.58 was obtained for this, while for the 50% granite - 50% titanium surface the value of 23.30 (closest to the trade mark) was calculated. Therefore, replacing the traditional components of selective surfaces with granite proved to be a satisfactory solution, contributing to the reduction of costs with solar energy.