Annual performance of an earth-air heat exchanger installed beneath a university building under continental climate conditions

Earth-Air Heat Exchangers (EAHEs) are increasingly considered a promising solution for space heating and cooling using renewable energy, owing to the widespread availability and stable thermal conditions of the ground. This interest is reflected in the literature, which includes a large number of studies on these systems. However, studies involving long-term monitoring of real systems installed in operational buildings remain limited, particularly for tertiary-sector buildings. Moreover, to the authors’ knowledge, no reported case studies exist of round-duct EAHE installed beneath building foundations. The present study monitors, over one year, a straight, parallel, open-loop EAHE serving a university lecture building in the continental climate of Valladolid, Spain. The system achieved specific heating gains of 37 kWh/m² year, resulting in 22% reductions in the annual heating ventilation demand of the Air Handling Unit (AHU). Owing to the reduced summer operation of the building, cooling ventilation demand is limited, with the EAHE covering 13.7 kWh/m²·year and yielding 90% savings. In winter, the thermal effectiveness of the EAHE approached 0.4 and 0.6 under low and high operating airflow rates, respectively. In summer, effectiveness was marginally higher. The cooling and heating Coefficients of Performance (COP), calculated based on the actual electricity consumption of the fan, reached 3.3 and 3.5, respectively. These results are within the range of values reported in the literature for other EAHEs installed in tertiary buildings and may be considered marginally superior, allowing for the high peak airflow rates of up to 40,000 m 3 /h handled by the system.