Thermal performance of nano-architected phase change energetic materials for a next-generation solar harvesting system

Abstract

A new type of colloidal solution is developed by dispersing phase change material-based composite materials with an innovative core/shell structure in water. This solution is designed for both heat conversion and thermal storage of solar radiation. The performance examinations of phase change material (n-Hexadecane, n-Octadecane, n-Nonadecane) and shell material (Au, Cu, Ag, and Al) types, capsule size, phase change material mass concentration, operating temperature and geometric parameters to the solar absorber environment are compared. The results reveal that n-Nonadecane@Au, Cu, Ag, and Al based colloidal solutions enhance the heat transfer rate by 35.1, 27.4, 27.8, 47.8 %, respectively compared to Au, Cu, Ag, and Al-based nanofluid. Plasmonic shell materials provide enhanced interaction with light, thus high energy phase change material capsules are obtained. Enhancing the dimension of phase change material capsules from 25 to 55 nm lessens the surface area to volume ratio, enabling the capsules to cluster in water and reducing the heat transfer. Therefore, the temperature increment of n-Octadecane@Au, Cu, Ag, and Al colloidal suspensions is declined by 1.5, 2.6, 2.1, and 4.8 %, respectively. Further, as the phase change material concentration boosts from 8 to 16 %, the temperature augmentation diminishes by 19.2, 25.7, 18.1, and 19.6 %, respectively using n-Hexadecane@Ag, Al, Au, and Cu colloidal suspensions. Augmenting the inlet temperature enhances the combined radiative and convective losses, following in a reduction in the temperature increment. Furthermore, increasing the collector’s aspect ratio allows more sunlight to penetrate each unit of surface area, thereby raising the temperature of the thermal fluid. Finally, the findings indicate that these novel colloidal solutions remarkably augment the capacity of the next generation solar energy harvesting towards a net-zero future.