Optical properties, thermal conductivity, and viscosity of graphene-based nanofluids for solar collectors

Abstract

Nanofluids based on graphene and water are promising working fluids for use in solar collectors. In this study, the optical properties, thermal conductivity, and viscosity of nanofluids based on water and graphene material, with the addition of sodium dodecyl sulfate (SDS) surfactant, were experimentally investigated. To obtain these nanofluids, graphene nanoparticles were synthesized using a plasma-chemical method and were later characterized by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The relationships between the concentrations of graphene in the nanofluids and the geometric parameters of vessels for effective absorption of solar energy were determined. The spectral dependences of the extinction coefficient for the nanofluids and for aqueous solutions with black aniline dye were compared. It was found that the application of graphene-based nanofluids is more effective than aqueous solutions based on aniline dye in photothermal energy conversion. Additionally, it was noted that the addition of graphene and the SDS surfactant does not lead to an increase in viscosity or a significant change in the thermal conductivity of the nanofluids for concentrations up to 0.02 wt%. The results showed that the studied nanofluids are effective absorbers of solar energy and, at the same time, do not require additional energy consumption to move through the solar harvesting circuit.