Thermo-hydraulic performance enhancement of a photovoltaic/thermal system using optimized wire coil inserts

Photovoltaic/thermal (PV/T) systems can simultaneously generate electricity and recover useful thermal energy, but their thermal and electrical performance is strongly affected by PV temperature and heat removal from the collector. Enhancing fluid mixing inside the collector is therefore important for improving heat transfer and maintaining favorable operating temperatures. The geometry of the wire-coil insert is characterized by three principal parameters: the pitch ( P ), wire diameter ( d ), and coil diameter ( D c ). This study presents a numerical investigation into how these geometric characteristics affect the thermo-hydraulic and electrical performance of a flat-plate PV/T system. The influence of the wire coil geometry on the flow behavior, heat-transfer performance, PV surface temperature, and pressure drop was comprehensively evaluated. The simulation results indicate that the optimal wire coil configuration is achieved at P = D i , d = 0.3 D i , and D c = 0.9 D i , where D i represents the inner diameter of the collector tube. With this optimized design, the PV surface temperature was reduced from 305.2 K to 301.7 K compared with the thinnest wire coil configuration, leading to increases of 5.3% in thermal efficiency and 4.7% in overall system efficiency. Moreover, growing the inlet flow rate from 30 to 120 L/h raised the performance evaluation criterion (PEC) from 0.6 to 1.6, while the overall efficiency improved from 83.4% to 88.7%. These outputs reveal that the effectiveness of the proposed wire coil insert becomes more pronounced at higher flow rates because of enhanced fluid mixing and improved heat-transfer capability. The results confirm that an appropriately optimized wire coil insert can boost heat extraction from the PV/T, resulting in enhanced thermal regulation and higher energy conversion performance while preserving favorable thermo-hydraulic behavior. Additionally, the optimal wire coil configuration proposed in this study provides a more uniform temperature field and lower temperature gradients than the conventional PV/T system without inserts. This improved temperature uniformity is expected to reduce thermal stresses and slow material degradation, thereby extending the operational lifespan of system.