Thermal evaluation of geometrical innovations in concentric and eccentric evacuated single and double solar collectors

Abstract

Abstract In this study, an experimental and numerical investigation of eight geometrical configurations of evacuated tube solar collectors was conducted. The configurations were tested simultaneously in outdoor installation under the same test conditions. The parameters such as collector eccentricity, solar concentration, vacuum, collector absorber, and cover tube materials were investigated. The numerical model developed in MATLAB was validated with experimental results. The results show that the eccentricity and the absorptivity of the material of the absorber are the parameters that have the highest influence on the collector performance. The use of reflective film in the eccentric solar collectors’ configurations can increase efficiency by 33%. The vacuum presented an efficiency increase variation between 1% and 4% in the eccentric tube collectors. For the concentric collectors configurations, the use of the vacuum between the tubes can reach an increase of 9% in its performance. The eccentricity of the collector using reflective film and vacuum allows an effective solar concentration in the collector absorber presenting a 26% higher efficiency when compared with the concentric collector.