Numerical investigation of heat and moisture migration in clayey and sandy soils, exploring seasonal fluctuations

Geothermal energy is widely known as a sustainable and eco-friendly energy source. For its applications, assessing the hydrothermal soil behaviour is crucial. However, the installation of ground geothermal systems at shallow depths makes them sensitive to atmospheric conditions, which affect the temperature field and the thermal balance. This paper presents the results of a numerical study investigating the hydrothermal behaviour of unsaturated soils (clay and sand), considering the meteorological variations at the ground surface. The atmospheric-soil interactions, including solar radiation, sensible heat flux, and latent heat flux, are essential for quantifying the energy balance and the hydro-thermal transfer processes taking place at the ground surface. By analysing these components, we can gain a comprehensive understanding of how energy is distributed and transferred to the soil. A numerical study was carried out using a finite element method (FEM) to assess the hydrothermal behaviour of unsaturated soils. The analysis of the obtained results from the model simulation reveals that variations in soil types have an impact on the distribution of heat and moisture migration, with both time and depth. Moreover, it appears that clayey soils show the highest efficiency in geothermal energy transfer. This research offers crucial insights into the optimization of both the design and implementation of geothermal systems.