High Temperature Solar Absorber Material Measurement Technique

Abstract

Basic material properties determine the amount of solar energy that is absorbed, transmitted or reflected and these values will often change with differing temperatures. This investigation developed a new approach to evaluate the material properties (i.e., reflectivity, absorptivity) of a solar absorber wall and experimentally tested the method using sample coupons. The reflectivity was measured both at ambient and elevated temperatures over a range of angles from 0 to 90 degrees. The same experimental data set was used to calculate the sample’s total reflectivity, by uniquely integrating the recorded intensities over a hemisphere. The test methodology uses the incident solar energy as the heating source, while directly measuring the reflected light (an integrated value over all visible wavelengths) and is suitable for test samples over 3,000 K.