Durability, performance and scalability of sol-gel front surface mirrors and selective absorbers

Abstract
Durability and performance tests have been developed in front surface silver mirrors . As prepared mirrors provide an AM1.5G integrated solar reflectance of 0.96 for thin SiO2 layers^1,2,3 and 0.93 for thick SiO2 layers. The protective SiO₂ layers are produced by the sol-gel technique⁴. Sol-gel thin silica protected mirrors present an outdoor durability over 4 years measured in a QUV weathering chamber and sol-gel thick silica mirrors present more than 5 years (tests currently being performed) . Thermal durability tests performed at 200°C show no appreciable degradation during one month, but at 300°C damage appear after two weeks. Sol-gel front surface aluminum reflectors have been developed for UV applications that consist in alternating layers of titania (TiO₂) and silica (SiO₂) over a commercial aluminum sheet attaining a reflectivity of 0.895 in UV region.. Selective Au/TiO2 absorber cermets have been produced with the same technique with quite promissing optical properties.