A comprehensive review on nanofluid operated solar flat plate collectors

The impact of population explosion and continuous upsurge on energy demand has resulted in the intimidating depletion of fossil fuel resources, increased environmental pollution, and elevated production and consumption cost. Hence, in the past two decades the demand for renewable energy has escalated. The solar energy is the most trending topic when talking about renewable energy sources, because of its ease of availability, reduced dependence on foreign fuels and negligible maintenance. This can be directly harnessed unlike other renewable energy sources. A solar flat plate collector converts the radiant solar energy from the sun into thermal energy; usually, copper or aluminium is used as heat absorbing material. However, to further enhance the performance and thermophysical properties of the heat exchanger liquids of flat plate solar collectors like radiative heat transfer and thermal conductivity, the nanofluids are used. The use of nanofluids as an innovative type of working fluids is reasonably a new development in solar flat plate collectors. They are prepared by mixing low concentration of solid particles, sized 1–100 nm with the base fluid. The objectives of this review paper is to recapitulate the investigations carried in the field of solar flat plate collectors using a range of nanofluids, the performance analysis of various flat plate collectors using numerous nanofluids and the challenges faced in developing an efficient thermal collector using nanofluids. Furthermore, the article discusses the opportunities for future research.