Hybrid solar air heater integrating flat plate and evacuated tube collectors with phase change material for improved thermal efficiency

The incorporation of phase change material (PCM) greatly enhances hybrid solar air heater's thermal efficiency formed of a flat plate collector (FPC) and an evacuated tube collector (ETC). The PCM helps in heat retention and further improving the operational performance of the system depending on the environmental conditions. Experiments are conducted under outdoor condition from the different climatic zones from March 8, 2024, to December 13, 2024, with hourly data collection from 8:00 h to 19:00 h. Experiments are conducted with an air mass flow rate of 0.030 kg/s, 0.035 kg/s, 0.040 kg/s with wind speed ranging from 4 to 7 m/s. In testing paraffin-based PCM (C28H58)–C30H62 for thermal energy storage, the output temperature of air, efficiency of the system, and pressure drop are correlated with variance in weather. These experimental results reflect heavy temperature variations however, system reveal a temperature that goes from 12°C at morning to reach 28°C by midday and, finally, a peak flat glass temperature of 77°C. The rising temperature reached 80°C at about 850 W/m² maximum solar radiation levels around 1:00 PM. Hybrid solar air-heating systems that use PCM operate at improved thermal efficiency to the tune of 65 percent at the air mass flow rate of 0.040 kgs, compared to the 48 percent for systems without PCM. Pressures drop, however, with increasing amounts of airflow, reaching a maximum of 225 Pa at the same flow rate. The investigation reflects the potential of PCM to store heat effectively for greater energy storage along with improved thermal management.