Glass Greenhouse CFD Simulation Using Solar Ray Tracing, ANSYS Fluent Software

Glass greenhouses rely greatly on solar radiation to work properly. Glass, which is transparent to most wavelengths of sunlight, permits solar radiation to enter the greenhouse, resulting in a warm and controlled environment for plant growth. Once inside, the greenhouse’s surfaces, such as plants, soil, and structures, absorb solar energy. The absorbed energy is then converted into heat, which raises the temperature inside the greenhouse. The glass walls trap this heat, resulting in a greenhouse effect that prevents infrared radiation from escaping and keeps the temperature greater than the surrounding environment. This controlled thermal climate is critical for extending the growing season, boosting plant growth, and protecting crops from bad weather conditions.

This time, a glass greenhouse is simulated using ANSYS Fluent software. As always, a valuable paper is selected for basic assumptions titled “Numerical and experimental study of a closed loop for ground heat exchanger coupled with heat pump system and a solar collector for heating a glass greenhouse in north of Tunisia”.

Simulation Process

The geometry of the glass greenhouse is modelled considering pipes beneath the soil ground acting as solar collectors. Although it is challenging, a structured grid is generated. Discrete Ordinates (DO) model is activated in the solver to investigate solar radiative effects, which play a crucial role in greenhouses. Plus, solar irradiation is calculated using ANSYS Fluent`s Solar Ray Tracing module. So, the software only defines the longitude and latitude of the location. It is 1st of January and the outdoor temperature is nearly 10°C.

Post-processing

The modeling of a glass greenhouse with solar collectors beneath during winter circumstances at an external temperature of 10°C yielded excellent energy efficiency and thermal regulation results. Despite the reduced outside temperatures, the greenhouse significantly increased internal heat retention due to the incorporation of solar collectors beneath the building. Consequently, the indoor temperature reaches 34.8°C, which is about 25°C higher than the outdoor temperature. The velocity and temperature contours show notable effects of natural convection inside the greenhouse and low absorption of glass.