A Passive Ventilation System for Energy Efficiency in Tropical Buildings

Passive design strategies incorporated in buildings could produce energy efficient designs, which can reduce or even eliminate the installation of complex and active energy consuming measures. This study involves the development of a passive ventilation system designed for tropical climates, which emphasized reliance on direct utilization of solar energy. The system uses a similar concept to that of a solar thermal flue, in which a solar heated channel which also functions as a daylight channel, is used to create the necessary stack effect for air movement. As the system is targeted for use in residential buildings and offices, the challenge would be to ensure that the system works for low ceiling heights and with minimal dissipation of heat to the interior of buildings. Being in the design stage, a Computational Fluid Dynamics (CFD) software is used to investigate the effectiveness of the system by predicting the temperature and airflow distributions as well as the air speed inside a typical naturally ventilated room at different solar times. Results show that the flow rate of air leaving the room were found to be reasonably favourable, increasing steadily to about 4 air change rate (ACH) towards later in the afternoon, as the air channel temperature increases. Graphical presentations of the simulations also portray the positive effect of the channel in inducing air movement within the interiors. However, air movement created in the occupied spaces was found to be rather low, averaging about 0.04m/s in the occupied spaces and with little variations throughout the day.