Abstract
The optical properties of a black pigment of mixed Mn-Fe oxides synthesized by the precipitation method, dispersed in silicone resin in different concentrations as well as different thicknesses of float glass with 0.1% of Fe2O3 for use in the construction of a two-slope passive solar still. Regarding the pigments, the spectral absorbance and emittance were evaluated, the x-ray diffraction patterns were obtained to know their crystalline structure and their morphology was studied through surface profilometry, in addition the spectral transmittance for the different samples of float glass was evaluated. With the previous information, both the absorbing surface and the condensers were optimized to propose the best design of the solar still. The hybrid material used as a selective coating in the still, which corresponds to 2.3% Mn-Fe mixed oxides, exhibited a high solar absorbance of 91.82% and a relatively low infrared thermal emission, less than 57.22%, as well as good stability to the corrosive and hot environment of the solar still, in addition to great durability over time, real operating conditions. The float glass with the highest transmittance corresponds to a thickness of 3 mm and an average transmittance of 82.57%. The built prototype was characterized by obtaining the temperature profiles of the absorber, water column and condensers, thermal efficiency, production and water quality. The prototype has a thermal efficiency of 27%, requiring only energy from the sun for its operation and the product water is distilled water, free of salts, of great potential value for human use and consumption in accordance with current official standards.