Performance analysis of a photovoltaic thermal system with ternary nanofluids cooling and dual phase change materials

Photovoltaic-thermal (PV/T) systems offer a sustainable solution for electricity generation and energy conservation in developing countries. However, high operating temperatures can significantly reduce their efficiency. This study investigates the thermal performance of a PV/T system incorporating a cooling flow channel to regulate temperature and enhance electrical output while utilizing excess heat for practical applications. The system comprises glass, polycrystalline silicon, an absorber, and a flow channel employing ternary and water-based nanofluids. Two phase change materials (PCMs), paraffin octadecane wax (C₁₈H₃₈) and sodium sulfate decahydrate (Na₂SO₄·10H₂O), are embedded in the channel to enhance thermal regulation. Numerical simulations are conducted using COMSOL Multiphysics 6.0, employing a conjugate heat transfer approach to solve the continuity, momentum, and energy equations. The study considers steady, laminar, and Newtonian flow conditions and evaluates system performance under varying heat flux levels. Key parameters include Reynolds number (50–200), nanoparticle volume fraction (1 %–15 %), latent heat of melting (240–260 J/g), and ambient temperatures in Sukkur, Pakistan. Results indicate that paraffin wax undergoes phase transitions more rapidly than sodium sulfate decahydrate, whereas Na₂SO₄·10H₂O exhibits greater temperature variations due to higher inlet temperatures. Optimal thermal efficiency of 75.91 % is achieved at Re = 50, T_amb = 45 °C, and $\varphi$ = 10 %.