Desenvolvimento e validação de protótipo experimental para estudo do envelhecimento fototérmico de superfícies seletivas solares

Abstract

The increasing demand for renewable energy sources has driven the use of solar thermal collectors, whose performance depends on the efficiency and durability of selective surfaces. However, these coatings undergo degradation under harsh operating conditions, requiring accessible photothermal evaluation methods. Given this context, this work presents the development and validation of an experimental prototype for the photothermal aging analysis of solar selective surfaces. The prototype utilizes halogen dichroic lamps as radiation sources, with temperature data acquisition performed via an Arduino microcontroller and thermocouple sensors. The methodology consisted of subjecting selective films to different ultraviolet radiation conditions (UV-C and UV-A) and thermal stress within the developed device. Chromium-based surfaces were investigated in three configurations: Cr (S1), Cr+Cr/Cr2O3 (S2) and Cr/Cr2O3 (S3), deposited by Magnetron Sputtering. The samples were characterized using UV-Vis-NIR, XRD, and Optical Profilometry. Results indicated losses in the absorptivity of the exposed substrates, with a mean reduction of 1.28%. Among the fabricated films, the S1 configuration demonstrated the highest stability (a variation of only -0.09%), while S2 showed the lowest resistance (-15.89% loss). XRD analysis revealed that the film structure maintained an amorphous character across all configurations and exposure environments, indicating phase stability. However, profilometry pointed out that the exposure of the S2 film to the prototype caused a greater roughness reduction effect compared to other environments. The prototype operated stably at 80 °C, validating its effectiveness as an innovative and low-cost tool for studying the durability of absorber coatings.