Experimental analysis of soil temperature profiles for shallow geothermal applications in tropical urban environments

Abstract

This study presents an experimental characterization of the soil temperature profile in the city of Soyapango, El Salvador, performed at an educational institution during the summer season. The objective is to evaluate, from a thermal behavior perspective, the potential applicability of low-enthalpy geothermal systems, specifically Canadian-type earth–air heat exchangers, under local urban conditions. Temperature measurements were performed at multiple depths between the surface and 3 m, and at different times of the day over a one-week period, to analyze thermal gradients, daily variability, and the degree of temperature attenuation with depth. The results show a significant reduction and delay in temperature fluctuations as depth increases; however, at 3 m depth the subsurface temperature still exhibits noticeable variability, particularly under high ambient temperature conditions typical of volcanic soils with low moisture content. These findings suggest that, in similar geological contexts, greater depths or additional design considerations may be required to achieve the thermal stability necessary for effective passive air-conditioning. The study highlights the importance of local, in-situ thermal measurements as a preliminary step for the design of shallow geothermal systems in tropical urban environments.