Nanofluid based photovoltaic thermal systems integrated with phase change materials: Numerical simulation and thermodynamic analysis

In the current research, a three-dimensional photovoltaic thermal system integrated with phase change material system with nanofluids is investigated. The working fluids involved in this study include nano-magnesium oxide, multiwall carbon nano tube and hybrid (mixture of nano-magnesium oxide and nano-multiwall carbon nano tube) nanofluids dispersed in pure water. After comparing single-phase model and mixture model, the mixture model is used in the study and fluid flow regime in the collector is assumed to be laminar, fully develop, uniform and incompressible, to model the nanofluid in the system. A parametric analysis is conducted to examine the effect of various parameters such as working fluid type, mass fraction of nanofluid and phase change layer thickness on thermal and electrical performance of system. Moreover, the temperature distribution of phase change in the system for different sections is investigated. According to the results, the surface temperature of the system with multiwall carbon nanofluid only reduces by 0.3 degrees C, with an increase in a mass fraction from 3% to 6%. Moreover, multiwall carbon nanofluid has the highest overall energy efficiency, and magnesium oxide nanofluid has the lowest overall energy efficiency. For the mass fraction of 6% wt, the overall energy efficiency of system with working fluids of water, magnesium oxide nanofluid, multiwall carbon nanofluid, and hybrid nanofluid is 55.24%, 60.08%, 61.07%, and 60.66%, respectively. In addition, it is observed that by increasing phase change layer thickness, both outflow and surface temperature of the system reduce.