Parabolic trough reflector manufactured with aluminum first surface mirrors thermally sagged

This project was conceived with the aim of developing a parabolic trough co ncentrator with first surface solar mirrors made over floated soda-lime gla sses with concave geometry. In order to cover all the surface of the concen trator, whose measurements were 2.37 m of aperture and 1.14m long, 16 mirro rs were built with sizes of 0.3 x 0.6m and they were put together like a mo saic set. Each mosaic segment of the parabolic trough was fabricated using a male mold over which were made concave mass-rock (Masa-roca(R)) parts of the same size of the mirrors. This product works up to 800 degrees 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 degrees C for about 2 h. Mirrors were made using sputtering technique with planar magnet ron. The evaporation of aluminum film was about 1000 Angstrom in thickness, while SiO2 was about 3000 Angstrom. The specular reflectance of the mirror s was around 86%. The held 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. (C) 2000 Elsevier Science B.V. All rights reserved.