Michael D. Gross, Associate Professor of Chemical Engineering
Spherical sintered bauxite particles between 200 mu m and 700 mu m in diameter have been shown to be effective in the direct absorption and storage of concentrated solar energy. These particles are commercially available in large quantities and exhibit as-received solar weighted absorptance (alpha(s)) greater than 0.90, which gradually degrades with extended heating in air at 700 degrees C and above. The degradation mechanism is an oxidation reaction that can be reversed via thermal or chemical reduction, resulting in alpha(s) > 0.95 along with enhanced resistance to further degradation for some formulations. Certain metal oxide pigments, added to Al2O3:SiO2, have proven to achieve solar weighted absorptance levels similar to those of the commercially available particles and may be promising alternatives to currently available materials.
Siegel, Nathan P.; Gross, Michael D.; and Coury, Robert. “The Development of Direct Absorption and Storage Media for Falling Particle Solar Central Receivers.” Journal of Solar Energy Engineering 137, no. 4 (2015) : 041003.