Dynamic behaviour of buildings with Thermally Activated Building Systems (TABS)

Thermally Activated Building Systems (TABS) integrate the exchange of heat and cold between the building and the HVAC system into the structure of the building. By using TABS, water filled tubes are inserted in the concrete floors/ceilings of the building. By supplying heated or cooled water, the room air is conditioned via the large thermal mass of the floor in contrast to the direct conventional HVAC systems.

 Heat and cold are exchanged via the floor and ceiling surfaces, with a large share of radiative heat exchange, which is experienced to be very comfortable. Air flow rates, possibly causing draft, can be reduced, because only hygienic air needs to be supplied.

 Since water temperatures can be relatively low for heating (< 30°C) and relatively high for cooling (> 15°C), low-exergy production systems, such as ground coupled heat pumps and ‘direct’ cooling can be used with very high efficiencies. On the other hand, TABS impose specific requirements to the building construction. Because thermal power is limited and the time constant is large, both the magnitude as well as the variation of the building loads must be limited by providing e.g. sufficient insulation and/or solar shading devices.

 Heat exchange between the TABS and the building zone can only be controlled by changing the surface temperature of the ceiling and floor surfaces, which is realized by adaptation of the flow rate or the water supply temperature. The time constant of this heat transfer process is in the range of 10-15 h, which is much larger than the occurring heat gains and losses. Therefore, an effective and efficient control strategy is of utmost importance in exploiting the energy saving potential of TABS, while realizing thermal comfort. Integrating the building and TABS dynamics, the knowledge of the future heat gains and losses and the knowledge of the occurring heat transfer phenomena into the control strategy is crucial. This can be realized by adaptation of the controller settings in traditional feedback control strategies or by more advanced controllers such as e.g. Model based Predictive Control (MPC). 

 Evaluating the effect of the control strategy and controller settings on the thermal comfort and energy use, is the main goal of the current research.

Contact persons

Maarten Sourbron
Lieve Helsen
Martine Baelmans