Design, modeling, and optimization of a dual reflector parabolic trough concentration system

The aim of the present work is to enhance the thermal management avoiding the high-thermal stress on the outer surface of the parabolic trough receiver (PTR) derived from nonuniform concentrated solar flux distribution. A parabolic trough concentrating (PTC) system with second homogenizing reflector (HR) is numerically designed and optimized to ensure a uniform concentrated solar flux on the PTR walls. For this purpose, a three-dimensional optical model has been developed to analyze quantitatively the improvement made by the HR using the optical efficiency and qualitatively basing on the uniformity of the solar flux density distribution over the entire surface of the PTR. The validation of the numerical tool is presented, and the algorithm of the design process has been proposed and detailed. As a preliminary trait, it was revealed that the peak of the designed system performance is achieved with a rim angle of 68 degrees avoiding simultaneously the aberration and the blocking effects. Despite the optical efficiency decrease by about 7% compared with the conventional PTC design, the uniformity of the solar flux distribution has been strongly improved such that the maximum local solar flux density gradient is decreased from 80 to 11 kW/m(2) equivalent to a decrease of 86.25% with respect to the conventional PTC and the average local density is about 25.5 kW/m(2).