Development of Refractive Secondary Optics for FLATCON ® Modules

In this paper we present our first results on developing refractive secondary optics for the FLATCON concentrator. A secondary concept basing on a single refraction is investigated. More specifically, the performance of a lens-shaped secondary in combination with the Fresnel primary lens is studied. In first tests we used secondary lenses which are originally designed for another application. In experiments and simulations these devices turned out to increase the acceptance angle and/or the geometrical concentration factor (Cgeo). In particular, the acceptance angle at Cgeo ≅ 385X can be increased from ±0.5° to ±1.1°. Furthermore, an acceptance angle of ±0.6° was determined at Cgeo ≅ 1040X. In outdoor experiments we studied the optical gains obtained by the application of the secondary lenses.