Experimental and numerical study of a solar collector using phase change material as heat storage

Abstract

Abstract The present work present numerical and experimental investigations to study the performance of a small-scale parabolic trough solar concentrator integrated with thermal energy storage system. A new design of receiver which uses the phase change material to store the thermal energy is built. A parabolic-trough solar concentrator was proposed and constructed using a concentric absorber tube with phase change material. The absorber is considered as a temporary thermal heat storage component. The heat storage-recovery mechanism will act as a thermal compensator that allows the parabolic trough solar concentrator to stabilizing energy output during the absence of intense radiation or for short time cloudy conditions. The PCM used a binary salt composed of a mixture of 60% NaNO3 and 40% KNO3, filling the annular space of the absorber tube. Solar energy is converted to heat, stored in the phase change material and is discharged to cold water, which is the final heat transfer fluid in the inner pipe of the receiver. The simultaneous testing of the receiver with and without phase change material is investigated. A commercial computational fluid dynamics model of the whole system is presented and numerical results are compared to experimental results, which were conducted with and without phase change material in the receiver tube. The maximum outlet water temperature achieved using phase change material in the receiver tube is about 16.80% and 14.86% higher than the simple tube for 21 July and 21 October respectively. The daily thermal efficiency of the parabolic trough solar concentrator increases by 6.56% and 8.32 respectively for a both days using a receiver with a phase change material concentric tube. The phase change material showed good heat retention of 2 h to 1 h 40 min for water inlet temperature 30°C and 40°C respectively.