Characterization of Sustainable Solar Absorbing Materials for Solar Thermal Applications

The optimization of absorber plate materials and coatings stands as a critical pursuit in augmenting the performance of solar thermal systems. In this study, substrates including copper, aluminum, stainless steel, brass, and zinc, machined to precise dimensions of $3 \mathrm{~cm} \times 5 \mathrm{~cm} \times 1 \mathrm{~mm}$, were subject to coating with various formulations of Black-N paint and charcoal through dip coating methodologies. Employing a handheld reflectometer gun, the optical properties, particularly absorptivity and emissivity, were meticulously measured. Results underscore a substantial augmentation in the optical characteristics of the coated absorber plates, particularly when concentrations of carbon in the coating solution were increased. This enhancement is attributed to the resultant amplification in surface roughness, which in turn bolsters emissivity by facilitating greater surface area. Remarkably, the choice of substrate material emerged as a pivotal factor. This research not only sheds light on the intricate interplay between coating composition, substrate material, and optical properties but also underscores the practical feasibility of employing economically viable materials in solar absorber plate applications, thereby paving the way for more efficient and cost-effective solar thermal systems.