Using Computational Fluid Dynamics to investigate heat exchanges between the environment and photovoltaic panels

Resumo

Given the increasing demand for energy sources with lower environmental impact, solar panels play an important role in diversifying energy sources and in the process of decarbonizing the electrical grid. Their electricity production is based on the photovoltaic effect; however, only a portion of the energy from solar radiation is utilized, with the rest being reflected or transferred to the environment in the form of heat, increasing the temperature of the panel and causing an energy efficiency loss, since the performance of the panels is influenced by the operating temperature.
Therefore, our study aims to investigate the heat exchanges by natural convection that occur between solar panels and the surroundings, disregarding radiation. The analysis was conducted using Computational Fluid Dynamics with the OpenFOAM software, which employs the Finite Volume Method to discretize the governing equations. We sought to evaluate the effects of varying the inclination of the panel on the surrounding temperature.
The CFD modeling consists of three stages: pre-processing, processing, and post-processing. In the pre-processing stage, the Gmsh software was used to create the computational domain, a simplified 2D model of 4 m x 4 m around the panel with a length of 2 m, a temperature of 80 °C, and presenting different inclinations. Then, the domain was discretized through the division into an unstructured mesh of finite volumes with progressive refinement near the panel.
Wall conditions were assigned for the ground and the panel, and free flow conditions for the surroundings. The fluid was defined as air, with dynamic viscosity of 1.849 × 10^-5 kg/m∙s, specific heat at constant pressure of 1000 J/kg∙K, Prandtl number of 0.7296, and temperature of 25°C. In the processing stage, the transient state solver, buoyantPimpleFoam, was used for transient and turbulent flows of compressible fluids for heat transfer, including the K-epsilon turbulence model.
In the post-processing stage, the Paraview software was used to map temperature and velocity fields. The results show the formation of air flows and the gradual propagation of temperature to the environment from the panel through thermal plumes. The increase in the panel's inclination contributed to raising the average temperature of the surroundings. The natural convection from the panel caused the formation of air flows due to the buoyancy effects that occur with the variation of the fluid's density.