Optimization and Experimental Validation of ACNP-Coated Peanut Shell Absorber Plate for Enhanced Thermal Performance of Solar Air Heaters

Abstract This study investigates the enhancement of thermal and exergy performance in a solar air heater using activated carbon nanoparticle (ACNP) coatings integrated with peanut-shell-based composite absorber plates. Experimental and optimization analyses were conducted to determine the influence of mass flow-rate, ACNP concentration, and solar intensity on system efficiency. Results revealed that the incorporation of bio-based peanut-shell composites and ACNP coatings significantly improved heat absorption and transfer characteristics. The optimum operating conditions were identified at a mass flow-rate of 0.035 kg/s, ACNP concentration of 20 wt%, and solar intensity of 760 W/m2, achieving a maximum thermal efficiency of 78.5%, exergy efficiency of 4.08%, and outlet air temperature of 78.2 °C, with a moderate pressure drop of 180 Pa. Validation through response surface methodology (RSM) confirmed strong agreement between predicted and experimental results, emphasizing the accuracy of the developed models. The contour and 3D surface plots demonstrated clear interaction effects between parameters, optimizing system performance effectively. The findings highlight that ACNP-coated peanut-shell composites provide a sustainable, cost-effective, and high-performance solution for solar air-heating applications, promoting the advancement of bio-inspired materials in renewable thermal energy systems.