Experimental investigations of secondary reflector enhanced medium temperature parabolic trough solar thermal collector

The performance of the newly designed parabolic trough solar thermal collector system has been investigated experimentally in the current work. The receiver tube is placed below the focal axis, and a secondary reflector is placed over it, as specified in the design. The primary goal of this experiment is to investigate the effect of a secondary reflector intended for uniform heat flux distribution on the performance enhancement of a parabolic trough solar thermal collector under various flow rates and outdoor weather conditions. The experiments are carried out by using Therminol55 as the working fluid. Effects of installing a secondary reflector under actual outdoor weather conditions and for different flow rates of 2.0 L min⁻¹, 5.0 L min⁻¹, and 7.5 L min⁻¹ have been evaluated and the amounts of outlet fluid temperature (T_o), useful heat gain (Q), and thermal efficiencies (η_th) have been reported. It is observed that the system performance with the secondary reflector is better than the conventional solar collector. It has been found that the efficiency of the solar collector is increased by 6.79% with the use of the secondary reflector. Using the secondary reflector, the average working fluid outlet temperature is observed as 461.35 K, which is 19.71% higher than the conventional PTC. The levelized Cost of Heat is 11.74 Cents/kWh according to the economic analysis, significantly lower than those found in literature. The experimental results and low cost of the system demonstrate that it can be used in the desired application, both technically and economically.