Investigation of a booster secondary reflector for a parabolic trough solar collector

The objective of this work is the investigation of a novel booster reflector in a parabolic trough collector (PTC). More specifically, a vertical secondary booster reflector is located at the end of the trough in order to enhance the optical performance of the solar collector. This extra concentrator reduces the end optical losses of the PTC by reflecting back them in the receiver. Moreover, it acts as an extra reflecting area which captures extra solar beam irradiation in the cases with a non-zero incident angle. The collector is examined optically and thermally in order to determine both the optical and the thermal gain by the use of this novel idea. The overall analysis is conducted for steady-state conditions, as well as the yearly evaluation of the suggested idea is given. According to the final results, the use of the extra booster leads always to optical and thermal enhancement, especially in greater incident angles. The yearly optical enhancement, for a collector with a focal distance to length ratio of 0.236, is calculated at 21.7% and it is more intense in the months with greater incident angles. More specifically, it was calculated at 8.7% in June, 24.2% in September and 77.1% in December. The thermal analysis proved that the thermal enhancement is greater than the optical and it is higher when the system operates with great fluid temperature levels.