Intercomparison of opto-thermal spectral measurements for concentrating solar thermal receiver materials from room temperature up to 800 °C

Abstract

An intercomparison of opto-thermal spectral measurements has been performed for some relevant receiver materials in concentrating solar thermal applications, from room temperature up to 800°C. Five European laboratories performed spectral measurements at room temperature, while two laboratories performed infrared spectral measurements at operating temperature up to 800 °C. Relevant materials include Haynes 230 (oxidized, Pyromark 2500 and industrial black coating) and silicon carbide. Two key figures of merit were analyzed: i) solar absorptance αsol at room temperature, over the spectral range [0.3 – 2.5] μm, ii) thermal emittance εth(T), over the common spectral range [2-14] μm, derived from spectral measurements performed from room temperature up to 800 °C.

Oxidized H230 reached an αsol value of 90.9±1.0%. Pyromark 2500 reached an αsol value of 96.3±0.5%, while the industrial black coating achieved an αsol value of 97.0±0.4%. Silicon carbide reached an αsol value of 93.5±1.1%. Low standard deviations in αsol indicate reproducible measurements at room temperature.

For oxidized H230, the εth,calc(T) value varied from 55% at room temperature up to 81% at 800 °C. For Pyromark 2500 and the industrial black coating, εth,calc(T) fluctuated between 90% and 95%, with a weak temperature dependence. For silicon carbide, εth,calc(T) varied from 70% at room temperature up to 86% at 800 °C. The typical standard deviation among participating laboratories is about 3%. εth,meas(T) values derived from spectral measurements at operating temperature were consistent within a few percentage points in comparison to εth,calc(T) values derived from spectral measurements at room temperature.