Investigating the impact of nanoparticle coating concentration variability on the heat absorption and efficiency of solar air heaters

Non-renewable fossil fuels have long supported global economic growth but have also caused detrimental environmental issues such as greenhouse gas emissions and climate change. To address these challenges and meet future energy demands sustainably, researchers are focusing on advanced materials and technologies to harness renewable energy. Solar energy, one of the most abundant renewable sources, offers a clean and widely available solution throughout the year. Among solar thermal technologies, the flat plate solar collector (FPC) stands out for its simplicity, cost-effectiveness, and practical application in thermal energy systems. This experimental study explores the impact of graphene nanoparticle-enhanced selective coatings on the absorber plate of a flat plate solar collector. Graphene, known for its exceptional thermal conductivity and optical absorption properties, was combined with black paint to form a novel coating applied to an aluminum absorber plate. Three samples were prepared with varying concentrations of graphene nanoparticles (0.5%, 1%, and 1.5%) and tested under real-time conditions. Air was used as the working fluid at a constant flow rate of 0.0169 kg/s. The results revealed a significant enhancement in thermal efficiency: the absorber surface achieved 67% efficiency at 0.5% concentration, 71% at 1%, and a maximum of 74% at 1.5% concentration. The improved performance is attributed to graphene's superior thermal conductivity compared to standard black paint. This research highlights the transformative potential of graphene-based coatings for enhancing FPC efficiency, presenting a novel and cost-effective solution for advancing solar thermal technologies and promoting sustainable energy systems.