**6. Conclusion**

Cooling of PV module by nanofluids significantly enhances electrical efficiency and thermal energy. Cooling causes the heat removal which in turns halts the development of thermal stresses, making the PV modules to last long and operate more efficiently. Employing nanofluids impedes entropy generation as well. Efficiency of this system escalates with increasing concentration of nanofluid up to a certain limit but as the concentration exceeds this optimum limit, efficiency tends to decline because of the clustering and agglomeration of nanoparticles. Increasing flowrate of nanofluid increases the efficiency but as the flow gets into turbulent regime the instability issues arise and this also requires higher pumping power, in turns reducing overall system's efficiency. Using helical microchannel can increase the heat transfer and thus overall efficiency gets elevated. Using surfactant in the nanofluid can also surge the system's performance. Some of the measures that can refine the performance of these systems include,

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The unresolved challenges being faced by the researchers while using nanofluids include instability, agglomeration, high pumping power, and erosions. Stability improvement is the most important need of the hour in order to further proceed towards commercial use of nanofluids, as no perfect method of preparation and processing of stable nanofluid has been determined up-to-date.
