Energy and exergy assessment of integrating reflectors on thermal energy storage of evacuated tube solar collector-heat pipe system

An experimental study is presented on the energy and exergy assessment of integrating reflectors with an evacuated tube solar collector-heat pipe (ETSC-HP) system on its thermal energy storage. The impact of using upper, lower, and upper and lower (two) reflectors on the thermal energy storage, input energy, and energy losses, reflectors' effectiveness, and energy and exergy efficiencies is assessed. A complete thermal model that evaluates the thermal performance of the collector-heat pipe system and selects the reflectors title angles is presented. The findings show that using reflectors with ETSC-HP rises its input energy, storage energy, energy and exergy efficiencies, and reflected and radiation losses but it reduces the convection losses. Using upper, lower and the two reflectors raises the input energy to the collector by about 15.3%, 22.5%, and 37%, respectively, and the output daily storage energy by 14%, 22.1%, and 35.7%, respectively compared with the system without reflectors. The daily thermal efficiency of the ETSC-HP system with upper, lower and the two reflectors is 63.8%, 71.67% and 76.25% compared with 60.57% of the collector without reflectors. Using reflectors with the ETSC-HP raises the system thermal performance curve efficiency by about 16% relative to the collector without reflectors. Moreover, using two reflectors increases the average daily exergy efficiency by about 25.3%. Using reflectors with ETSC-HP proves its ability to raise the energy storage from the collector system compared to previous works.