3.05 - Low Concentration Ratio Solar Collectors

Abstract

This chapter presents a review of low concentration ratio solar collectors. The concentration ratio (C) of the collectors belonging in this category is not more than about 10. Because of the low concentration ratio, these collectors usually collect both direct and diffuse solar radiation. According to their concentration ratio, these collectors can be steady (C<2) or tracking. When tracking is used and depending on the concentration ratio, this can be intermittent as high accuracy is usually not required. The frequency of tracking increases with the concentration ratio. Higher concentration ratio leads not only to higher collector operating temperature but also to higher tracking accuracy requirements. The types of collectors examined in this chapter are the flat-plate collectors with diffuse reflectors, the reverse flat-plate collector, the compound parabolic collector (CPC), and various designs applied to evacuated tube collectors (ETCs) with either external or internal reflectors. One type of cusp concentrator, which is used in integrated collector storage (ICS) systems, is also examined.