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

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 degrees C. Five European laboratories performed spectral measurements at room temperature, while two laboratories performed infrared spectral measurements at operating temperature up to 800 degrees 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 alpha sol at room temperature, over the spectral range [0.3 - 2.5] mu m, ii) thermal emittance epsilon th(T), over the common spectral range [2-14] mu m, derived from spectral measurements performed from room temperature up to 800 degrees C. Oxidized H230 reached an alpha sol value of 90.9 +/- 1.0%. Pyromark 2500 reached an alpha sol value of 96.3 +/- 0.5%, while the industrial black coating achieved an alpha sol value of 97.0 +/- 0.4%. Silicon carbide reached an alpha sol value of 93.5 +/- 1.1%. Low standard deviations in alpha sol indicate reproducible measurements at room temperature. For oxidized H230, the epsilon th,calc(T) value varied from 55% at room temperature up to 81% at 800 degrees C. For Pyromark 2500 and the industrial black coating, epsilon th,calc(T) fluctuated between 90% and 95%, with a weak temperature dependence. For silicon carbide, epsilon th,calc(T) varied from 70% at room temperature up to 86% at 800 degrees C. The typical standard deviation among participating laboratories is about 3%. epsilon th,meas(T) values derived from spectral measurements at operating temperature were consistent within a few percentage points in comparison to epsilon th,calc(T) values derived from spectral measurements at room temperature.