Abstract

This thesis presents a numerical and experimental study of a hybrid ventilation system of an institutional building with emphasis on thermal comfort. Hybrid ventilation can improve thermal comfort and at the same time reduce energy consumption and peak power demand. By precooling the thermal mass of the building the energy consumption of the following day can also be reduced. A 17–story high institutional building is used as a case study to test different control strategies and to define the temperature low limit for admitting exterior air into the building through a transition space (a corridor), in order to ensure thermal comfort. A developed model, calibrated from full–scale tests, estimates the heat removed from the concrete and the impact on thermal comfort. It is used to test and compare the existing
control strategy to different ones of both reactive and predictive nature. 12 typical days are used to compare different control strategies. The system is currently operating based on heuristic control, with an exterior air temperature setpoint above which the air is allowed into the corridors. A control strategy based on data of the previous hour (reactive) is expected to triple the energy savings potential, but not guarantee satisfactory thermal comfort. A predictive control strategy provides thermal comfort, but also energy savings potential of the same magnitude as the reactive. Energy savings potential is increased even more if it is weighted more against discomfort when the building is unoccupied. In general the predictive control strategy opens the motorized dampers as much as possible during the cold days – without compromising thermal comfort – to precool the concrete floor so that it can reduce the cooling load of the next day.