Effect of the cyclic heating (aging) on the solar absorptance and specific heat of particulate materials

Abstract

Using solid particles as a heat transfer media (HTM) in concentrated solar power applications gained growing attention lately. Unlike molten salt, solid particles offer high operating temperatures (greater than 1000°C), no freezing issues, abundantly availabile, high thermal energy storage capacity, low-cost, non-corrosive, and applicability of direct irradiation. Comprehensive knowledge of thermophysical and optical properties of solid particles is essential to ensure an effective harnessing of solar energy. The most important considerations when selecting solid particles include (1) thermophysical and optical properties, (2) thermal resistance, (3) crack resistance (4) satisfactory health and safety risks (5) availablity, and low-cost. It is also imperative to consider optical and thermophysical characteristics that might change from what they were as received after cyclic heating for a long time. Therefore, the knowledge of the thermal performance of particulate materials becomes significant before using them as HTM. In this study, some particulate materials have been chosen to study their feasibility to be used as heat transfer and storage media for the particle-based central receiver tower system. These particulate materials include red sand, white sand, ilmenite and carbobead CP. The cyclic heating was performed on the particulate materials for 500 hours at 1200°C. Weighted solar absorbtance and specific heat have been measured for the candidate particulates as received and after cyclic heating (aging) for a specified duration of time.