Enhancement of solar absorption performance using TiN@SiCw plasmonic nanofluids for effective photo-thermal conversion: Numerical and experimental investigation

The heat exchange medium moderately determines the heat utilization efficiency of solar energy. Nanofluids, a type of working fluids with high thermal conductivity and strong light absorption, have been studied and applied to improve solar energy utilization. In this study, TiN@SiCw binary composite nanoparticles were prepared by a coupling agent method. The optical coupling absorption properties of TiN and SiCw nanoparticles were numerically simulated by the finite-difference time-domain method. Results showed the TiN@SiCw nanostructure can improve the width and intensity of spectral absorption. Then TiN@SiCw and SiCw nanofluids based on ethylene glycol were prepared by a two-step method and studied experimentally in terms of thermal conductivity and optical absorption. The photothermal conversion efficiency of the nanofluids was measured by a special flow and photothermal coupling model (side radiation). Experiments showed the thermal conductivity and light absorption of TiN@SiCw composite nanofluids were stronger than those of SiCw single-component nanofluids and the base fluid. Specifically, the energy absorption fraction and the photo-thermal efficiency of TiN@SiCw nanofluids at the highest concentration of 140 ppm were 96.2% and 90.5%, respectively, which were 12.1% and 21.7% higher respectively compared with SiCw nanofluids. Hence, the TiN@SiCw nanofluids are suitable for enhancing the efficiency of solar collectors.