Thermal and Eco‐Economic Performance Enhancement of Evacuated Tube Solar Collectors Using EG ‐Modified TBAB Phase Change Materials

This research enhances thermal efficiency and sustainability of evacuated tube solar collectors (ETSCs) by developing a high‐performance EG‐modified tetrabutylammonium bromide (TBAB) phase change material (PCM) that improves heat transfer, energy storage, and overall system reliability. Lower‐temperature solar heating applications with ETSCs are to be thoroughly investigated, as they are more effective heating methods. This study examines the thermal and eco‐economic potential of a TBAB‐PCM improved with 2.5 wt.% extended graphite (EG). The EG was added to TBAB at 0, 0.5, 1, 2, and 2.5 wt.%. The resulting 2.5 wt.% EG demonstrated a high thermal conductivity of 0.94 W/m·K, a latent heat storage capacity of 174.3 kJ/kg, and good thermal stability (95.4% residual mass at 200°C). This modified PCM achieved a maximum temperature of 96.8°C, resulting in quicker heat uptake and increased collector performance, with a heat absorption rate of 24.7 kJ/h·kg and a high thermal efficiency of 72.4%. Environmental and economic research revealed a high CO 2 emission reduction of 0.32 kg/day·m 2 , a high annual energy savings of $19.76/m 2 , and a minimum payback period of 9 months. With optimum thermal enhancement and sustainability. Hence, the 2.5 wt.% EG–TBAB composite is recommended for a viable solar thermal energy storage option.