Parabolic trough reflector manufactured with aluminum first surface mirrors thermally sagged

This project was conceived with the aim of developing a parabolic trough concentrator with first surface solar mirrors made over floated soda-lime glasses with concave geometry. In order to cover all the surface of the concentrator, whose measurements were 2.37 m of aperture and 1.14 m long, 16 mirrors were built with sizes of 0.3×0.6 m and they were put together like a mosaic set. Each mosaic segment of the parabolic trough was fabricated using a male mold over which were made concave mass-rock (Masa-roca®) parts of the same size of the mirrors. This product works up to 800°C with a minimum deformation when it has been set and hardened. In order to sag the floated glasses, they were introduced in a furnace up to 600°C for about 2 h. Mirrors were made using sputtering technique with planar magnetron. The evaporation of aluminum film was about 1000 إ in thickness, while SiO2 was about 3000 إ. The specular reflectance of the mirrors was around 86%. The field test of focusing such a concentrator gave a size focus of about 5.08 cm, where over 90% of reflected beam solar irradiance arrived on a simulated pipe receiver with this diameter.