Direct solar-thermal conversion features of flowing photonic nanofluids

Efficient solar energy capture and flowing fluid heating are very important for solar-thermal conversion applications. In this work, through multi-scale theoretical and experimental analysis, the application features of flowing photonic nanofluids in direct solar-thermal conversion were studied. On the one hand, at the microscopic level, the process of full-spectrum sunlight capture by photonic nanofluid was investigated. Specifically, the interactions among particles in Fe₃O₄/TiN photonic nanofluids were analyzed in detail, as well as the mechanism of sunlight capture enhancement caused by spectral complementarity and near-field effect of nanoparticles was expounded. On the other hand, through macroscopic flow heat transfer calculations and experiments, this work studied the direct solar-thermal conversion effects of photonic nanofluids under different application conditions, including solar concentration ratio, flow rate, working temperature, and sunlight intensity. Both the experimental and theoretical results clearly illustrate that the photonic nanofluid has excellent solar-thermal conversion ability, and can be well adapted to various solar-thermal applications. This work provides a detailed method and performance parameter reference for the nanofluid selection and the working condition adjustment of direct solar-thermal conversion.