Effective thermal conductivity and thermal cycling stability of solid particles for sCO2 CSP applications

Abstract

A supercritical CO2 (sCO2) Brayton cycle solar power system based on solid particle thermal energy storage is proposed to enhance the efficiency of concentrated solar power (CSP). The effective thermal conductivity and thermal cycling stability of solid particles are crucial for sCO2 CSP applications. Some natural and artificial solid particles, such as black silicon carbide, green silicon carbide, white corundum, brown corundum, brown ceramsite sand, garnet, river sand and desert sand are considered as potential thermal energy storage medium due to its low cost and easy availability in large quantities. However, there are few studies about the effective thermal conductivity and stability of these solid particles after thermal cycling tests. In this study, the effective thermal conductivity of these solid particles was measured by the hot wire method. Particularly, the effective thermal conductivity of black silicon carbide and green silicon carbide was measured by modified hot wire method. In addition, the changes of mass, real density, bulk density, void fraction and mean diameter of the above-mentioned solid particles after 100 times thermal cycling tests were also recorded to analyze thermal cycling stability. Based on the results of all the above tests, green silicon carbide exhibits high effective thermal conductivity and good thermal cycling stability, which presents a great potential as a thermal energy storage medium.