Aging of solar absorber materials under highly concentrated solar fluxes

• A definition of ‘aging’ is suggested in the case of solar absorber materials.
• A facility named SAAF allows accelerated aging tests to be performed.
• The influence of periodic solar irradiance variations on aging is evaluated.
• The evolution of the properties is related to the decrease in the thermal performance.

This article introduces an experimental approach to study the aging of absorber materials used in the receivers of CSP power plants. The term ‘aging’ is discussed in the case of solar absorber materials and a definition is suggested. A two-layer material (metal+paint coating) that is commonly used in solar tower receivers is studied. Accelerated aging tests are performed on this material with the Solar Accelerated Aging Facility (SAAF) available at PROMES laboratory (Odeillo, France). To evaluate the aging state of the samples after being solar-treated, the thermoradiative and thermophysical properties that characterize the aging of the coating are estimated with two experimental devices. The results show the influence of the mean irradiance, amplitude, period, and exposure time of the radiative cycles on the estimated properties. The absorptance appears to be the most sensitive property causing the thermal performance to decrease. Particular attention should be paid to the application of the paint coating which needs to be vitrified carefully in order to obtain optimal and stable absorption properties.