Numerical simulation and experimental validation of a photovoltaic/thermal system: Performance comparison inside and outside greenhouse

Greenhouses consume huge amounts of energy in cool seasons and the destructive effect of it has recently given rise to the popularity of renewable energies such as solar energy in greenhouses. A photovoltaic/thermal system was numerically simulated in ANSYS Fluent to be used in the design and development of an optimized structure of such a system. The system was simulated in three tube arrangement (continuous, longitudinal, lateral), 5 tube diameters (6, 8, 10, 12, 14 mm), and 7 flow rates (3, 2.75, 2.5, 2.25, 2, 1.75, 1.5 lit/min). The optimized design from the simulations was developed, and was tested in indoor and outdoor conditions of a greenhouse. The performance of both settings was compared under similar conditions. Simulation results revealed that the best design among the proposed scenarios for development of a thermal collector was the one with longitudinal 14 mm tubes under 3 lit/min flow rate. The results showed that there is a good agreement between field data and simulation data. It was also found that the mean electrical efficiency for the inside and outside systems was 9.72% and 5.28%, respectively. The thermal efficiency of the outside system was 58.15% whereas the efficiency of the inside system was 48.82%.