A Yolk/Shell Strategy for Improvement in Thermal Conductivities in Microencapsuted Phase Change Materials

Abstract

Solar thermal energy has been considered as one of the most promising energy source because of its inexhaustible feature. Solar thermal power generation system is designed for using and storaging sunlight and turning it into electricity. However, the amount of power generation is limited by the working fluid’s heat capacity and thermal conductivities. Enhancements in solar thermal storage induced by latent heat have been demonstrated by adding phase-change materials (PCM) into working fluids. In this study, we introduce yolk/shell structure, which represents a new class of special core/shell structures with a distinctive core @void @shell configuration. We successfully encapsulated Sn microparticles with protective carbon shell to prevent oxidation. And with this yolk/shell strategy, the voids between the yolk and the shell could serve as a buffering space for the volumetric changes of the Sn cores during the phase transition process, resulting in high stability. The Sn coated with carbon yolk/shell microparticles possessed high thermal conductivity and heat capacity. Furthermore, the appropriate doping proportion of PCMs with Hitec salt has also been tested without sacrificing viscosity of working fluids. This study provides a new strategy for microencapsulated particles and carbon shell have high thermal conductivity and thermal stability. With the low-cost synthesis process and superior thermal properties, Sn encapsulated with carbon shells have potential applications in energy storage enhancement in thermal energy systems.