Energy and exergy analysis of a solar air collector with evacuated tubes under different flow and reflector configurations

This study investigates the energy and exergy performance of a solar air collector (SAC) integrated with evacuated tubes under varying air flow rates and reflector configurations. Experiments conducted from 08:00-18:00 h showed outlet air temperatures up to 105.2°C. Energy efficiency ranged between 35-71%, while exergy efficiency varied from 2.16-5%. Exergy input, output and loss averaged 104.6, 3.0 and 101.6 kJ/kg, respectively. Efficiency decreased near midday but improved later. Overall, the reflector-assisted high-flow system demonstrated superior thermal and exergy performance, highlighting its potential for sustainable and efficient solar air heating applications.