Enhancing the buoyancy of air flows inside vertical solar chimneys using a G/CNT/AgNW-coated heat collector

Solar chimneys collect solar energy to facilitate the buoyancy-driven ascension of air in a vertical structure for cooling and heating buildings. In this study, we maximize solar-energy collection by nanotexturing the surfaces of a solar chimney with a supersonically sprayed film composed of graphene (G), carbon nanotubes (CNTs), and silver nanowires (AgNWs). This film facilitates the trapping of solar radiation via light scattering, essentially creating a black body inside a Helmholtz jar. The effect of the G/CNT/AgNW film thickness on solar-energy collection in an L-shaped channel and a 12-story building prototype is studied numerically and experimentally. A fully three-dimensional CFD analysis is conducted to investigate the buoyancy-driven flows inside the building model with and without the coating. The numerical results reveal that the outlet air velocity (w) and temperature (T) at the top of the building increase by 63% (an increment of Δw ∼ 0.07 m/s) and 82% (an increment of ΔT ∼ 27 °C), respectively, for the coated case as compared to the uncoated case.