Energy and comfort performance analysis of monitored thermally activated building systems combined with geothermal heat pumps

The combination of geothermal heat pumps (GEO HPs) and thermally activated building systems (TABS), that allow both low temperature heating and high temperature cooling, could yield primary energy savings of around 20- 71% in comparison with conventional heating/cooling systems. However, the potential energy savings are rarely reached in practice due to bad integration of the different subsystems and inefficient control. The present paper presents the analysis of two monitoring campaigns by stressing the influence of relevant parameters such as the performance of components (heat pump, ground heat exchangers, TABS, etc.), building characteristics and the implemented control strategies. The buildings have been monitored and analyzed in the frame of the WKSP-project realized by Institute of Building Services and Energy Design (IGS) at Technical University of Braunschweig. The results show good performance of ground coupled heat pump with seasonal COP up to around 5. Moreover, the use of ground heat exchangers to perform free chilling allows seasonal EER up to 20. Furthermore, the control strategies implemented in the different buildings are quite different. It is also shown that this system can lead to a running cost reduction up to 50% compared to conventional systems and that CO2 emissions can be reduced by 40%.