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In this study, the performance of a photovoltaic thermal system (PVT) is investigated in a numerical and experimental study. In the numerical part, the Taguchi method is applied to determine the optimum place and time of the PVT system. Moreover, the optimum parameters that are independent of the design of the PVT system are obtained to improve the performance of the system in a specific place and time. Using the specified optimum parameters, the performance of the system is investigated from the energy and exergy viewpoints, experimentally. In the experimental study, using the designed setup, the performance of a water based PVT system is compared with that of a conventional photovoltaic unit (PV). The experiments are performed on a selected day in August at the Ferdowsi University of Mashhad, Mashhad, Iran (Latitude: 36° and Longitude: 59°). The numerical results indicate that the most effective parameter on the performance of the PVT system is the coolant inlet temperature and its optimal value is 20 °C. Moreover, the total energy efficiency of the PVT system in the optimum working condition is 69.02 %. The experimental results reveal that the average output electrical energy of the PVT system is 6.27 % more than that of the PV unit. In addition, the average thermal energy and exergy efficiencies of the PVT system are 34.12 % and 0.72 %, respectively.

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In this study, the effects of using pure water and Zinc oxide/water nanofluid as working fluids on the performance of a photovoltaic thermal system are evaluated using computational fluid dynamic approach. Moreover, effects of the parameters that are independent of the system design on the electrical and thermal efficiencies of the photovoltaic thermal system with Zinc oxide/water nanofluid are investigated. The studied parameters are: absorbed solar irradiation, wind speed, ambient temperature, coolant inlet temperature, coolant mass flow rate, and nanoparticles mass fraction in the Zinc oxide/water nanofluid. In this study, using the designed setup, the three-dimensional numerical model is validated by comparing the simulation results with those of the experiments. The experiments are performed on a selected day in August at the Ferdowsi University of Mashhad, Mashhad, Iran (Latitude: 36° and Longitude: 59°). Based on the numerical results, the thermal efficiency of the photovoltaic thermal system with Zinc oxide/water nanofluid is enhanced by increasing the absorbed solar irradiation, ambient temperature, coolant mass flow rate, and nanoparticles mass fraction. However, increasing the wind speed and coolant inlet temperature decreases the thermal efficiency of the system. Moreover, the considered parameters in this study have slight effects on the electrical efficiency of the photovoltaic thermal system. The relative increase of the electrical and thermal efficiencies of the photovoltaic thermal system with Zinc oxide/water nanofluid with 12 % by weight compared to that of pure water is 0.28 % and 12.58 %, respectively.

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In this study, the effects of using pure water, water/ethylene glycol mixture with 50:50 wt% and pure ethylene glycol as the working fluids on the energy and exergy efficiencies of a photovoltaic thermal (PVT) system are experimentally investigated. Moreover, the performance of the PVT systems are compared with a conventional photovoltaic (PV) system. The experiments are performed on a selected day in August at the Ferdowsi University of Mashhad, Mashhad, Iran (Latitude: 36° and Longitude: 59°). The investigated parameters in this study are: the photovoltaic cells temperature; output electrical and thermal powers; electrical and thermal energy efficiencies; output electrical and thermal exergies; and electrical and thermal exergy efficiencies. Based on the results, the PVT system with water/ethylene glycol mixture increases the output electrical power by about 5.41 % compared to that of the PV system. Furthermore, the results indicate that using pure water in the PVT system enhances electrical and thermal energy efficiencies compared to those of pure ethylene glycol and water/ethylene glycol mixture, whereas the overall exergy efficiency of PVT systems with pure water and water/ethylene glycol mixture working fluids are approximately same.