INVESTIGATION OF CORE-SHELL NANOFLUIDS FOR ENHANCED SOLAR ABSORPTION AND THERMAL STORAGE
Direct Absorption Collectors (DACs) have gained popularity as a new and promising design for solar collector systems. DACs utilize nanofluids to absorb solar energy directly; eliminating the need for an absorber tube, and providing increased efficiency. Nanofluids are dilute suspensions with dispersed nano-sized particles that show good thermal and optical or radiative properties. This study focuses on optimizing the overall system efficiency considering collection and thermal storage efficiencies. Therefore, nanofluids of core shell nanoparticles are considered as they can enable optimization of collection and thermal storage efficiencies simultaneously. Core-shell nanoparticles are spherical particles with multiple layers of different materials that can be selected for considering the absorption and thermal storage behavior. Component and system level models are developed. The collector model considers direct absorption of solar energy by a flowing nanofluid, while the radiative properties of the nanofluid are predicted based on Lorenz-Mie theory. Combined with the thermal storage model, the overall efficiency of the system will be compared to conventional systems. Based on both component and system level performances the optimal size, material and concentration for core shell nanoparticles will be identified.