Nano Fluid and Phase Change Materials Practice in Evacuated Tube Solar Collector: A Review

Solar thermal technology applied to utilize the thermal energy coming from the sun in various applications with the help of solar thermal collectors.Different types of solar collectors such as flat plate, evacuated tube, concentrating collectors, and pitched roof solar collectors are available in practice.Among them, evacuated tube solar collectors are widely used due to their lower convective losses and higher efficiencies.Researchers put great effort to enhance the efficiency of ETSCs by applying various enhancement techniques like integration of fins and reflectors; incorporation of different thermal energy storage materials, nanofluids, PCMs, etc.The purpose of this article is to summarize the effect of nanofluids (ZnO, CuO, Al 2 O 3 , and CNTs) and different PCMs (Tritriacontane Paraffin and Erythritol) as energy storage options in practice on the efficiencies of evacuated tube collectors.PCMs with melting temperature (90 -180 °C) have been successfully practiced in ETSCs.