We have numerically investigated the natural convective heat transfer and entropy generation characteristic inside a wavy solar power plant filled with MWCNT-Fe3O4-water nanofluid using the finite element method. The simulated flow and temperature fields are investigated in terms of streamline contour, isotherm contour, local Nusselt number, average Nusselt number, dimensionless total entropy generation, and dimensionless average total entropy generation by varying the dimensionless amplitude of the wavy wall and nano-particle volume fraction. We reported that the presence of a wavy wall and the addition of nano-particles decreases the strength of recirculation developed in the flow field. Moreover, as seen from the analysis, an increase in the amplitude of the wavy wall and nano-particle volume fraction enhances the average Nusselt number. The entropy generation due to viscous dissipation is dominated for the considered value of the Rayleigh number. In addition, our results show that the increase in wave amplitude and nano-particle volume fraction reduces the average entropy generation. Inferences of this analysis are expected to have far ranging consequences to the optimum design of the solar power plant.