Thermal performance and economic sustainability of flat plate solar collectors using MgO and ZnO nanofluids: A comparative analysis

Abstract

Considering the higher outlet temperature, the present study assessed the performance of Zinc oxide (ZnO) and Magnesium oxide (MgO) nanofluid-based flat plate solar collector at a low volumetric flow rate, that is, 30 L/h. The lower solar irradiance results in a low percentage enhancement in collector efficiency; therefore, it constraints the use of the nanofluid-based collector at such conditions. The collector efficiency was nearly 67.98% and 65.22% for 1 vol% ZnO and 0.2 vol% MgO, respectively, almost 20.57% and 16.53% more than base fluid (ethylene glycol: distilled water). For 1 vol% ZnO and 0.2 vol% MgO, the heat absorption parameter intensified by 20.48% and 17.12%, respectively. The payback period at the optimum concentrations of ZnO and MgO nanofluid-based flat plate solar collector compared to electric heating was ∼2.97 and 3.69 years, respectively. In terms of present worth, the cost savings in a life span of 15 years was approximately 1918.18 and 1839.05 USD for 1 vol% ZnO and 0.2 vol% MgO, respectively. Such gains could be extended using large-sized areas of collectors. The 1 vol% ZnO at the flow rate of 30 L/h has the shortest payback period and highest cost-saving; hence, profoundly recommended in the flat plate solar collector instead of the base fluid.