Solar energy systems - Potential of nanofluids

Global warming escalation has extended average temperature of earth beyond its safe limit. To avert this environmental-threat, solar energy has acquired substantial attention of remarkable researchers in this century. To effectively utilize solar energy by transforming into thermal and electrical energy, the involvement of nanofluids having intensified thermal, optical and magnetic properties, has become very popular. The foremost objective of this article is to provide a comprehensive review on the applications of nanofluids in solar energy systems like solar collectors, photovoltaic cells, solar stills, and thermal energy storage, which are thoroughly discussed in this paper. The effect of various critical parameters including flow rate of nanofluid, concentration of nanoparticles in base fluid, size, and type of nanoparticles on the efficiency of solar systems is thoroughly analyzed by graphical means. Comparison is made between the performance of nanofluid and base fluid in terms of electrical and thermal efficiency enhancements for all solar energy systems. Effect of nanoparticles on outlet temperature of working fluid, area reduction of solar system, optical efficiency, pumping power and friction factor of working fluid is also analyzed. In addition, the stats of the entire work considering leading investigators, organizations, countries, and journals have also been discussed briefly. Results suggest that nanofluid have a massive impact on heat transfer and system overall efficiency compared to base fluid in solar energy systems. Moreover, various challenges including stability, cost-effectiveness, higher pumping power with the use of nanofluids have also been briefly discussed in this study. (C) 2019 Published by Elsevier B.V.