Experimental 3E Assessment of a PLC-Controlled Solar Air Heater with Adjustable Baffle

This work investigates the performance of a solar air heater (SAH) equipped with ten baffles whose angles can be adjusted in real time by a PLC. Many SAH systems operate passively, which makes their outlet temperature sensitive to daily variations in solar radiation. This study aims to show that an actively controlled SAH can maintain stable and efficient operation under practical outdoor conditions. Experiments were carried out at two set-point temperatures commonly used in drying applications, 54 °C and 60 °C, and the system was assessed through energy, exergy, and sustainability indicators. Greater baffle inclination increased turbulence and heat transfer, yielding thermal efficiencies up to 76.8%. The friction factor followed the Reynolds number closely, indicating that overall flow resistance depends mainly on the airflow rate. Exergy efficiency remained between 1.24% and 2.69%, while the Sustainability Index stayed near unity due to fan power related losses. A regression model was also developed to estimate the airflow needed to keep the outlet temperature at the desired level. Long-term projections show that the system can supply 20–22 MWh of heat and avoid nearly 9 tons of CO₂ emissions over 20 years. These findings highlight that combining PLC-based control with adjustable baffles offers a practical and environmentally meaningful improvement for solar air heating systems.