Light-absoption selection of nanoparticles and nanofluids containing nanoparticles for their effective heating by solar radiation

Light-absorption selection of single nanoparticle for solar radiation requires the simultaneous fulfillment of all of the following novel conditions—maximal close (overlap) of the dependence of nanoparticle efficiency absorption factor on wavelength with the dependence solar irradiance, predominant role of nanoparticle absorption over its scattering, the use of maximal values of nanoparticle efficiency absorption factor and its size. These results highlight the possibility for effective application of single homogeneous Ti and core–shell Ti–TiO2, Ni–NiO nanoparticles with radii of about 75 nm as perfect absorbers for solar radiation in the complete optical spectrum 250–2500 nm. Light-absorption conditions for nanofluids include dominant radiation absorption by presented nanoparticles with selected properties and concentrations of about 1 9 109, 1 9 1010 cm-3 under the solar absorption by water in the spectral interval of 250–1000 nm, which includes * 70% of whole solar energy. Presented results can be applied for applications in the development of novel working nanofluids for direct absorption solar collectors. These conditions can be used for the selection of various nanoparticles from different materials and structures for other optical radiation sources.