AGING OF SOLAR BOOSTER REFLECTOR MATERIALS

Anodized aluminium lacquered with polyvinylidene fluoride, anodized al uminium, vacuum evaporated aluminium foil and stainless steel have bee n aged up to 7 yr. It was found that anodized aluminium is not long-te rm durable, while the others show only slow deterioration. Stainless s teel, however, has very low solar reflectance to make it useful. A pro mising material is lacquered aluminium, which is durable but tends to become scattering after ageing. Another promising reflector material i s vacuum evaporated aluminium foil, which after more than 6 yr of agei ng is still highly reflective and very specular. Light scattered withi n a cone of typically 20 degrees will hit the solar collector. Thus, t he optical characterization should ideally be performed with scatterom eters and integrating spheres with this acceptance angle. The characte rization should, furthermore, be carried out at an incidence angle of 45 degrees for booster reflectors. The influence of the lacquering pre -deposition treatment on the optical properties has also been studied and it was found that a less aggressive process is beneficial for the optical properties. (C) 1998 Published by Elsevier Science B.V. All ri ghts reserved.