ASSESSING SOIL THERMAL BEHAVIOR FOR GEOTHERMAL APPLICATIONS: THE INFLUENCE OF SALINITY ON HEAT TRANSFER

Soil salinity represents a critical environmental problem that alters the thermal properties of soil, especially in dry and arid regions where it occurs naturally or due to unsustainable land management. The efficiency and design of shallow geothermal energy systems, which depend on the soil's thermal behavior to provide heating and cooling, will be strongly affected by these alterations. This work involves the development of a theoretical and numerical model that simulates the coupled transport of heat, moisture and chemical solute in unsaturated soils, including the impact of dry atmospheric conditions characteristic of the Sahara Desert. Three soil types: sandy, sandy loam, and silty loam, that are typical of the prevailing soils in the Adrar region, were investigated under three varying levels of salinity. The findings show that salinity has a significant impact on the dynamics of surface and subsurface temperatures, with the effects differing depending on the type of soil. The highest surface temperatures were observed in sandy soil with a salinity level of 0.1 M, while the most favorable thermal performance was recorded in sandy loam at a higher salinity concentration of 0.3 M. Moreover, it has been shown that with increasing salinity reducing heat accumulation, nonsaline conditions (0 M) produced the best thermal performance for silty loam soil. These findings highlight the complex relationship between soil composition and salinity in influencing the hydrothermal behavior of unsaturated soils. Furthermore, this research provides important knowledge to optimize the design of shallow geothermal systems in arid environments, enhancing their efficiency and performance. By integrating an understanding of soil thermal behavior under varying salinity and climatic conditions, the study contributes to creating more reliable and sustainable geothermal energy solutions adapted to the specific demands of dry regions.