Underground spaces natural energy applied in the building thermal conditions performance in summer conditions

Abstract

This paper presents a numerical simulation, done by a Building Dynamic Software, of an application of underground thermal energy storage in a university building with complex topology. In this study, the level of thermal comfort of the occupants of a building located in a Mediterranean type environment is evaluated for typical summer conditions. The Building Dynamic Software calculates the air temperature of the spaces, the surface temperature of opaque bodies, transparent bodies and internal bodies, the mass of contaminants and water inside the spaces and in the surfaces, the thermal comfort of the occupants, the indoor air quality and the flow thermal energy from underground to the occupied spaces. The university building is divided into 319 spaces, distributed by four floors, and is composed by 329 transparent surfaces (windows) and 3585 opaque surfaces (internal and external walls, doors, and others). Below the ground floor is numerically considered an underground floor, with the same area of the building and with a typical floor height, used to thermal energy storage. The building internal ventilation system, during the day, transport the cooled airflow from the underground to thermally uncomfortable spaces. The cooled airflow is transported to spaces turned to East in the morning and to spaces turned to West in the afternoon. However, throughout the day the cooled air is transported to all the south-facing spaces. Two situations were simulated numerically: with and without underground thermal energy storage. The occupancy and the internal ventilation were also considered. The results show that the internal airflow and the outside temperatures recorded during the 24 hours of the day allow to guarantee the necessary underground thermal energy storage to cool the more uncomfortable spaces. The indoor air quality is acceptable and the thermal comfort level of occupants, considering their adaptation, is near the acceptable level suggested by the standards.