Optical characterization of solid particle solar central receiver materials

Abstract

The angular scattering properties and scattering and absorption components of the extinction coefficient have been measured for Master Beads, an iron-doped Al/sub 2/O/sub 3/ spheroid manufactured by Norton Chemical Co., Worcester, MA. This material, commonly used as a proppant in oil well drilling operations, exhibits good optical absorption properties over the solar insolation spectrum, and favorable thermal and mechanical properties for temperatures up to 1000/sup 0/C. These characteristics, along with its low cost, make Master Beads a good candidate as the absorbing medium in the solid particle solar central receiver concept. The objective of the ongoing optical properties measurement program is to obtain information to be used as input to radiation transfer models for prediction of receiver performance. Scattering and extinction measurements were performed at 632.8 nm in a falling curtain geometry of one-particle nominal thickness. Measurements were performed over a range of mass flow rates and particle densities. Photographic documentation of curtain particle density enabled calculation of mean scattering and absorption loss components per particle in the absence of multiple-particle optical interactions.