Properties of granular materials as heat transfer and storage medium in CSP application

Abstract

A selection of granular natural and ceramic materials has been experimentally characterized with regard to their application as heat transfer and storage media in concentrating solar power plants. Thermophysical, thermomechanical, tribological and rheological measurements have been conducted in order to identify the most suitable candidates for this dynamic high temperature operation. Ceramic materials are found to comprise some advantages, but natural products offer a considerably more economic solution. Thermal bulk conductivity is found to be only marginally affected by the solid's thermal conductivity, while specific heat is the same for all solids. Ceramics entirely withstand thermal cycling, while quartz-containing materials are prone to severe degradation. Most materials are found to attain a saturated state of attrition while being sheared under load, wherein quartz sand offers the lowest mass fraction of debris at saturation level. In the investigated grain size range, all materials show good flowability. The generation of debris requires consideration in the design of the CSP storage components.