THEORETICAL AND EXPERIMENTAL PERFORMANCE OF COMPOUND PARABOLIC CONCENTRATORS

Abstract

The compound parabolic concentrators (CPC) are promising low concentration non imaging solar collectors, with intermediate indicative working temperature range (60 - 300 oC), that can operate monthly, seasonally or annually without the need of continuous tracking. They show competitive performance with flat plate collectors when used in applications of temperatures slightly above the ambient. Likely, the CPC collectors have lower cost and smaller pumping power consumption. Thereby, the present work presents a rigorous study of the optical, geometrical and thermal characteristics of CPCs with bare tubular absorbers. This investigation covered also the effect of truncation, number of frequent tilt adjustments and usage of heat transfer enhancement (HTE) techniques like twisted tape insertion on the performance of CPC. In all cases, the CPCs are oriented as usual in an East-West direction and facing south. Moreover, a CPC test rig was set up at the Faculty of Engineering campus, Cairo University, which helped to validate the transient model and gave a clear indication for the CPC performance under Egypt’s environmental working conditions. The designed CPC performed well as a solar water heater with a measured efficiency of around 46.7% during winter