We investigated the natural convective heat transfer characteristics within a solar power plant having a built-in aluminium metallic porous block and by using MWCNT-Fe3O4/water hybrid nanofluid. The Darcy-Brinkmann-Forchheimer model is used to describe the porous media flow field as well as the energy equation. When a metallic porous block is integrated to the plant, the average Nusselt number becomes significantly higher and increases with increasing Darcy numbers. The use of a hybrid nanofluid causes higher heat transfer rate compared to a pure fluid. Inferences obtained from this analysis are expected to provide a design basis of a modern solar plant intended for augmented energy recovery.