INTENSITY DISTRIBUTION IN THE COLLECTOR PLANE FROM STRUCTURED BOOSTERREFLECTORS WITH ROLLING GROOVES AND CORRUGATIONS

While testing different reflector materials for external reflectors fo r solar collector arrays, it was found that standard rolled aluminium and corrugated aluminium materials could perform almost as well as mir ror-like materials. A ray tracing model was developed to calculate the intensity in the collector plane for solar radiation from reflector m aterials with grooves or corrugations. Laboratory measurements, for re flector samples, with a specially designed spectral scatterometer were used to determine the angular intensity distribution of the reflected radiation. Calculations with the model using measured intensity distr ibutions show that the scatter from aluminium materials with rolling g rooves will be directed close to the specular direction and along an a lmost circular arc in the collector plane. The intensity in the collec tor plane will be redistributed slightly upward or downward depending on the season and time of day; therefore, both an increase and decreas e in average intensity can occur during the year relative to a mirror- like material with the same total reflectance. For rolled aluminium, a small performance improvement can be achieved compared to a mirror re flector with equal total reflectance. Corrugated surfaces will yield a significant increase in average intensity onto the collector aperture at times when the radiation from a mirror-like reflector would otherw ise be lost above the collector.