A new approach for obtaining angular acceptance function of non-perfect parabolic concentrating collectors

摘要

A new approach to calculate the angular acceptance function of cylindrical parabolic collectors has been developed. The procedure is rapid, simple and enables obtaining the acceptance function with or without absorber deviations. In a simple way, it registers the view angle of an eye slipping along the reflector surface. In case there are deviations, as a result of loss of symmetry, the function splits into four branches: two for the right and left hand side of the reflector section and two for the left and right hand side of the light cone reaching the aperture. As a result of deviations some branches are affected by windows where sun light escapes, reducing the optical efficiency of the collector. Deviations are computed as: (a) distance (d) between parabola focus and deviated absorber center and (b) rotation angle of the absorber (omega). Examples of perfect and non-perfect collectors are given and a variety of situations simulated: distance (d) varying between 0 and 1.0*Rabs and rotation angle (omega) between (-90 degrees) and (+90 degrees). A procedure to generate angular acceptance functions monotonically decreasing with the view angle is described and discussed. Results are exposed as sensitivity curves where the main parameters of the angular acceptance function are registered. The method described enables to map a large variety of optical configuration errors, which can be used for quality tests, design procedures and collectors development. Non parabolic geometries can also be treated with a similar procedure, showing that the method developed is a general and versatile approach. (C) 2017 Elsevier Ltd. All rights reserved.