Numerical simulation and experimental characterization of the heat transfer in a PV/T air collector prototype

Abstract

PV/T systems are an emerging technology for the simultaneous production of electrical and thermal energy. In this paper, we present an experimental device modified with an arrangement of aluminum square tubes to remove thermal heat from the system and increase its electrical efficiency. A 1D analysis allowed prediction of the heat transfer in the solid components. Moreover, a 3D simulation allowed visualization of the temperature distribution in the prototype. The simulations considered the surrounding temperature, the solar irradiance and the airflow velocity inside the square tubes. The glass temperature, PV cell temperature and the outlet airflow temperature were logged. The study was performed at a low airflow (0.5 m/s) and at a high airflow (2 m/s); for both experiments, the maximum solar irradiance was 800 W/m2 and the heat fluxes were calculated. The time constant was shorter for the experiment at low airflow, because the airflow increased by 63.2% at 5400s. At a high airflow, it took 9100 s to achieve the 63.2% of the maximum increase, and the difference between the outlet temperature and the temperature of the surrounding air was significantly reduced. At 0.5 m/s and 2 m/s the PV cell reached a maximum temperature of 75 °C and 59 °C, respectively. The maximum difference in temperature between the two experiments was 20 °C. The best thermal average efficiency was 42.5%, corresponding to the high airflow experiment. Furthermore, based on the favorable air outlet temperature, at this flow rate, the outlet air could be used for drying in a subsequent process.

Keywords

• Photovoltaic thermal air collector (PV/T)
• Heat transfer
• Airflow
• Solar energy
• Numerical simulation
• Experimental data