Influence of the spectral composition of solar radiation on the heating and evaporation processes of graphene nanofluids

• Published in: Solar energy 2024-11, Vol.282, p.112977, Article 112977
• Main Authors: Tran, Q.T., Mikhailova, I.A., Mikhailov, V.V., Makarov, P.G.
• Format: Article
• Language: English
• Subjects: Graphene nanofluid; Interfacial solar vapor generation; Photothermal effect; Solar radiation
• ISSN: 0038-092X
• DOI: 10.1016/j.solener.2024.112977

[Display omitted] •Graphene nanofluid was well heated under 520 and 808 nm monochromatic irradiation.•In the wavelength range from 1.85 to 8.90 μm, the main absorber was water.•Increased graphene nanoflake concentration enhanced solar evaporation rate.•Graphene nanofluid showed high promise for direct absorption solar collectors. In this study, the effects of heating and surface evaporation of graphene nanofluids, influenced by the spectral composition of incident radiation, were investigated for the first time. It was observed that the graphene nanofluid exhibited significant heating when exposed to lasers with wavelengths of 520 and 808 nm, whereas water did not absorb or heat under visible and near-infrared light. However, in the wavelength range from 1.85 to 8.90 μm, water acted as the primary absorber, with graphene nanoflakes serving primarily to enhance the thermal conductivity of the solution. The evaporation rate from the surface of a graphene nanofluid with a 5 % mass concentration was approximately 70 % higher than that of distilled water. The use of graphene paste further increased the evaporation rate by up to 95 %. A homogeneous graphene nanofluid model was developed, which aligned well with the experimental data. This model was used to examine various factors affecting the heating process of graphene nanofluids, including the concentration of graphene nanoflakes, density of the incident radiation flux, nature of the upper surface of the system, depth of the liquid column, and light absorption coefficient of the bottom surface material. Importantly, our study highlights the significant potential of graphene nanofluids as working fluids in solar energy systems, offering broadband absorption for the direct conversion of solar radiation into thermal energy.