Evaluating the solar flux distribution uniformity factor for parabolic trough collectors

In a parabolic trough collector (PTC), the varying solar flux distribution at the receiver's surface causes high temperature gradients, which are harmful to the material. The existing studies have used only a visual approach to depict the homogenization of solar flux, which is subjective rather than quantitative. This paper presents a method for quantifying the uniformity of flux distribution as a single numerical factor (m), that can be applied to any PTC design. The approach, based on ray tracing, was used to determine the locations on a receiver surface where the incoming rays are captured. Validation was performed by comparing the ray tracing of a single ray with measurements obtained in a 2D drafting program. Then, taking a PTC with a concentration ratio C = 10, the model was simulated for various rim angles (j). The relationship between the visual flux distribution and m is discussed. The values of m for several real PTC designs were then evaluated and compared. A useful visual tool is also presented for obtaining and comparing m for a range of concentration ratios and rim angles. An online tool was also developed to help researchers to quickly calculate the m value for their PTC designs. (C) 2020 Elsevier Ltd. All rights reserved.