Shape optimization for parabolic troughs working in non-ideal conditions
Authors: Pierucci G., Fontani D., Sansoni P., De Lucia M.
Autors Affiliation: Università di Firenze, Dip. di Ingegneria Energetica, via Santa Marta 3, 50139 Firenze, Italy; CNR-INO Istituto Nazionale di Ottica, Largo E. Fermi 6, 50125 – Firenze, Italy
Abstract: The aim to realize more efficient solar concentrators, improves the research on the best configuration for the mirror surfaces. The optical behavior of a parabolic trough collector is investigated depending on its particular shape outside the ideal conditions. A 2D ray-tracing model of the real systems was realised taking into account a reference value for the solar radiation and different misalignment errors between the light beams and the mirrors axis. The computational analysis shows the relationship among the collection performance and the main geometrical parameters; different boundary conditions bring to consider different optimal configurations for the concentrator shape. Generally for medium concentration levels (50-150x) and non-ideal settings the more efficient parabolas are not characterized by a rim angle equal to 90°, which is the theoretical best value. Among the studied cases, it is interesting to note that a possible working condition for the PT system corresponds to a light beam scattering of 0.5° and a tracking misalignment of 0.2°. With these constrains, imposing high optical performance requirements, a maximum concentration ratio near to 60 can be reached with rim angle values of about 114°.