Experimental (3E) Energy, Exergy, and Economic Analysis of a Star-Fin PVT Collector Incorporating Al₂O₃ Nanofluid

This study experimentally investigates a novel star-fin absorber tube integrated into a photovoltaic-thermal (PVT) collector to enhance thermohydraulic, electrical, and economic performance while maintaining low hydraulic resistance and manufacturing simplicity. Star-shaped copper fins mounted on a central rod promote organized secondary flows that disrupt the development of the thermal boundary layer. Three configurations were evaluated under controlled indoor irradiance of 400–1000 W/m² and coolant flow rates of 0.5–2.5 LPM: a smooth pipe baseline (SP), a star-fin insert with distilled water (ID), and a star-fin insert with 0.20 vol% Al₂O₃-water nanofluid (ID-NF). A consistent performance hierarchy of ID-NF > ID > SP was established across all operating conditions. The ID-NF configuration achieved a peak thermal efficiency of 83.05% at 2.5 LPM and 1000 W/m², representing a 20.3% improvement over the SP configurations. Electrical efficiency exhibited an irradiance-dependent behavior, with ID-NF attaining 14.29% at 400 W/m², owing to effective nanofluid cooling that suppresses carrier recombination losses. Second-law analysis confirmed the superiority of ID-NF, achieving a thermal exergy efficiency of 24.12% at 1000 W/m², versus 8.73% for SP, while a peak thermal-hydraulic performance factor of 1.418 at 2.5 LPM establishes a net thermohydraulic benefit over all comparable passive insert geometries in the literature. Economically, ID-NF delivered the highest annual energy gain (389.5 MYR/year), the lowest cost-benefit ratio (0.0417), and the shortest payback period (6.9 years), outperforming the bare PV system by a factor of 2.6. The star-fin insert achieves competitive performance with a single manufacturable geometry, without relying on nanophase-change materials, offering a scalable and economically viable pathway for next-generation PVT systems.