Development of a secondary collector for an existing solar trough

Maximizing the optical collection efficiency of a linear concentrated photovoltaic (CPV) system implies to provide a uniform illumination over the cells array, even when an off-axis sun tracking angle occurs. Moreover, the small cells’ size imposes severe requirements on the dimensions of the linear sun image. In contrast optical aberrations, solar divergence effects, mechanical strains, and incorrect tracking contribute to spread the concentrated light and to shift the image position. A secondary optic device was especially designed and optimized to convert a medium concentration parabolic trough originally designed to be a single-stage system into a double stage. The additional element design has to face the rigid constraints imposed by the preexistent main collector. Despite this limitation, its introduction guarantees a suitable lighting on the cells in a range within ±0.5° of tracking angle misalignment, consistent with the system tracking errors observed during the first test operations.