Further realistic annual simulations of earth-air heat exchangers installations in a coastal city

Abstract

Earth-Air Heat Exchangers (EAHE) can reduce the heating/cooling load of a building using buried ducts, where the air is forced to flow and exchange heat with the soil. Due to the Earth’s thermal inertia, the region near the surface of the soil can serve as a heat source or sink. This available thermal energy in the soil surface layer comes from the solar radiation incident on the Earth. Thus, the air leaves the duct(s) at milder temperatures, helping to reduce the use of traditional air conditioning systems. This paper aims to analyze the thermal behavior of an EAHE taking into account realistic data relative to a south coastal city of Brazil, where: (1) the geotechnical profiles of the soil were obtained in-situ through standard penetration tests (SPT), allowing to adopt adequate thermo-physical properties; and (2) the temperature annual variation for the soil surface and the air in the region were obtained from an international forecast center. Still in the methodology, the simulations were performed with a verified and validated finite volume computational model. As the overall results point out, 2 m is the ideal depth to place the ducts locally, which increases the EAHE thermal potentials in the summer and winter seasons. Different of other places, due to the water tables close to the surface in the studied regions, it is not worth to make installations at higher depths there.