Optical properties of nanoparticles and nanofluids for direct absorption of solar radiation

Abstract

Theoretical investigation and selection of the optical properties of homogeneous metallic (titanium Ti, gold Au) and metal core–oxide shell (Ti–TiO2) nanoparticles with the radii 50, 75, 100 and 125 nm and their nanofluids have been carried out in the spectral interval 200–2500 nm for the purpose of effective absorption of solar radiation. Selected Ti and Ti–TiO2 nanoparticles with the radii 75–100 nm, in some cases up to 125 nm, are good absorbers in the visible and infrared spectral intervals and can be proposed for their use in solar thermal systems. Extinction and absorption of solar radiation by nanofluids (nanoparticles and water) are determined by the dominant influence of the system of Ti and Ti + TiO2 nanoparticles with concentration 109 cm−3 in the spectral interval 200–800 nm for the radii 50–75 nm and in interval 200–1100 nm for the radii 100–125 nm, and water dominantly influences the radiation extinction by nanofluid in the spectral range 1200–2500 nm.