Modification of a parabolic trough collector and its exergy analysis

Extraction of thermal energy from solar energy is a challenge in harvesting solar energy. When higher temperatures are required, it becomes necessary to concentrate solar radiation. Parabolic Trough Collectors (PTCs) are formed by a cylindrical surface of mirrors having high reflectivity with a parabolic shape that concentrates solar radiation on a receiver tube located at the focal point of the parabola. Working fluid, which is heated up by the solar radiation, circulates inside the receiver tubes. Energy losses at higher temperatures are the main cause of efficiency loss in PTCs. In previous work, the collector was exposed to the atmosphere and thus thermal losses were high. Some modifications to the design of PTCs for reduction of energy losses was proposed in this work. In order to reduce convective losses, an evacuated tube collector was introduced instead of copper tube. A modified PTC was fabricated and its performance evaluated. Exergy analysis was performed to study the effects of operational and environmental parameters on the performance of PTCs.