Exergy-based optimization of fin geometry in unglazed PV/T air collectors

This study presents a comprehensive thermal–electrical and exergy modeling framework for an unglazed photovoltaic/thermal (PV/T) air collector equipped with longitudinal fins, with emphasis on identifying environmentally sustainable fin-design strategies. Although fin-based enhancement is widely applied in PV/T systems, the influence of fin aspect ratio ( FAR ) H/t and air mass flow rate m ̇ on exergy performance remains insufficiently quantified. To address this gap, a 3-node steady-state energy balance model is developed to quantify heat transfer among the PV laminate, air duct, and back plate, incorporating fin conduction and radiative exchange through an equivalent surface formulation. The coupled governing equations are solved iteratively to predict PV temperature, outlet air temperature, and thermal–electrical exergy performance. The results reveal a clear thermodynamic trade-off between fin-area enhancement and flow-blockage-induced convection suppression. Increasing the FAR improves overall performance by enhancing heat recovery despite the hydrodynamic penalty. At m ̇ = 0.050 kg s⁻¹ m⁻², the total exergy efficiency increases from 11.30% at H/t = 20 to 12.96% at H/t = 80, accompanied by an approximate 2.2% reduction in exergy destruction. At higher m ̇ = 0.075 kg s⁻¹ m⁻², total exergy efficiency further improves from 12.05% to 14.06%, with a larger 2.7% decrease in exergy destruction, indicating improved thermodynamic performance at increased airflow rates. Model predictions show good agreement with published experimental trends, confirming the validity of the approach. A lightweight sensitivity analysis identifies solar irradiation and convective heat-transfer correlations as dominant uncertainty sources, while top and back loss coefficients exhibit weak influence. Overall, the findings provide design-oriented guidance for sustainable PV/T development by demonstrating that meaningful gains in energy and exergy recovery can be achieved through geometric fin optimization and appropriate airflow selection without additional materials or auxiliary cooling. • A unified thermal–electrical–exergy model is developed for a fin-integrated PV/T air collector. • Fin aspect ratio is identified as a key design variable governing PV/T thermodynamic trade-offs. • Total exergy efficiency improves from 10.9% to 13.8% by increasing the fin aspect ratio (H/t). • Model predictions closely match published experimental trends, confirming model accuracy. • Sensitivity results show Ut and Ub have minimal effect, validating their constant-parameter treatment.