Numerical assessment and building-scale integration of water-cooled PV/T systems for cooling load mitigation in hot-arid climates

Hybrid Photovoltaic/Thermal (PV/T) systems offer a dual-benefit pathway for decarbonizing the building sector by simultaneously generating electricity and recovering thermal energy from a single rooftop-integrated collector. Buildings in hot-arid climates such as Mosul, Iraq face extreme summer cooling demands driven by ambient temperatures exceeding 42 °C and peak solar irradiance reaching 950 W/m 2 , yet high-fidelity numerical assessments of PV/T systems specifically calibrated to these conditions remain scarce. This study presents a three-dimensional, steady-state Computational Fluid Dynamics (CFD) investigation — conducted in ANSYS Fluent 2024R1 — of a single water-cooled PV/T collector module integrated into a 500 m 2 residential rooftop in Mosul. The novelty of this work lies in combining high-fidelity collector-level CFD modelling with an analytical heat-flux-based methodology to estimate the roof-attributable cooling load reduction at building scale under extreme Iraqi arid climate conditions. Parametric simulations were conducted across four coolant mass flow rates (0.05–0.20 kg/s) under peak summer irradiance (950 W/m 2 ). The CFD model was validated against published experimental data, with mean absolute percentage errors (MAPE) below 3% for coolant outlet temperature rise across all tested flow rates, establishing model reliability. Results show that increasing the mass flow rate to 0.20 kg/s reduces the average PV surface temperature from 343 K to 318 K, effectively mitigating thermal hotspots and enhancing electrical efficiency by up to 8%. While the coolant temperature gain (ΔT) decreased from 9.0 K to 4.5 K at higher flow rates, the total thermal power extracted per module increased monotonically, reaching approximately 3.8 kW at 0.20 kg/s. Based on CFD-derived PV surface temperature reductions and an analytical roof heat flux model (using steady-state conduction and sol-air temperature equations), the four-collector array is estimated to reduce the roof-attributable cooling load by approximately 13–18% of the total building baseline load, corresponding to an absolute reduction of 1.6–2.2 kW. These findings confirm that building-integrated PV/T systems represent a high-efficiency, zero-footprint solution for combined energy generation and thermal load mitigation in arid regions, and provide a transparent, reproducible methodology for building-scale load estimation from collector-level CFD results.