Characterization of Pyromark 2500 Paint for High Temperature Solar Receivers

Abstract

Pyromark 2500 is a siliconebased hightemperature paint that has been used on central receivers to increase solar absorptance. The radiative properties, aging, and selective absorber efficiency of Pyromark 2500 are presented in this paper for use as a baseline for comparison to hightemperature solar selective absorber coatings currently being developed. The solar absorptance ranged from ∼0.97 at nearnormal incidence angles to ∼0.8 at glancing (80آ°) incidence angles, and the thermal emittance ranged from ∼0.8 at 100 آ°C to ∼0.9 at 1000 آ°C. After thermal aging at temperatures of ∼750 آ°C or higher, the solar absorptance decreased by several percentage points within a few days. It was postulated that the substrate may have contributed to a change in the crystal structure of the original coating at elevated temperatures.