Abstract
A solar air heater absorbs radiation in the visible wavelength range to heat air for the thermal management of buildings. We demonstrate the fabrication of highly textured surfaces using reduced graphene oxide (rGO) nanosheets and silver nanowires (AgNWs) to maximize the collection of solar heat. The textured surface traps light waves efficiently because of the multiple reflections inside the nanoscale grooves. The textured surface functions as an almost perfect black body that traps all the radiation inside a Helmholtz jar via these multiple reflections. A circular copper disk with a thickness of 1 cm was coated with rGO and/or AgNWs, and the total amount of transferred heat was estimated. The thickness of the coated layer was less than 20 mu m. This indicates that, compared with that of the copper disk, the thermal conductivity of the layer was negligible. The heat transfer rates of the AgNW-, rGO-, and rGO/AgNW-coated disks were compared with those of the bare substrate (non-coated disk). We observed that the rGO/AgNW hybrid coating produced the highest heat transfer rate because of the optical interactions between the rGO sheets and AgNWs, with the synergetic effect enhancing light scattering at the textured surface.