At November 26-28, 2018 the 6th working meeting of IEA HPT Annex 46 on “domestic hot water (DHW) heat pump systems” took place at the NTB in Buchs, Switzerland. On the first day the occasion was used for an exchange of information between the Annex 46 and the Annex 49 on “design and integration of heat pumps in nearly Zero Energy Buildings (nZEB)”.

Due to the low space heating demand of nZEB, the DHW operation has a higher share of the total energy consumption in nZEB. Therefore, the DHW performance of the heat pump gains importance for the overall net zero energy balancing. Integration options for heat pumps with other building technologies in multifunctional use, on the other hand, may be beneficial for the DHW operation. Thus, synergies exist between the topics of the two Annexes. Therefore, an information exchange and a collaboration between the Annexes is very useful in order to exchange specific project information of the national contributions in the respective Annexes.

At the Annex 46 working meeting, the following project examples of the DHW integration by heat pumps in nZEB have been presented, which are investigated by simulation and monitoring in the IEA HPT Annex 49:

• Central heat pump for space heating of 8 terraced houses with decentralised DHW storages equipped with booster heat pumps investigated by simulation and monitoring as contribution of TH Nürnberg. The space heating grid is used as source for the booster heat pumps in DHW mode.
• Central energy storage with solar thermal support and heat pump with desuperheating mode coupled to a fresh water system in the single flats of a multi-family nZEB investigated by simulation and monitoring at the University of Innsbruck. The system has the advantage of low supply temperature requirements due to the fresh water system and reduced legionella risk at short distribution pipes. The system is investigated in more detail regarding storage size, storage stratification and the integrated desuperheating mode.
• Heat recovery for space heating and DHW from the cooling operation in a 5-storey building with mixed commercial, office and residential use investigated by monitoring at HSR Rapperswil in collaboration with the designers of the building. The building is operated without recooler, i.e. all waste heat from the space cooling operation is recovered for the DHW preheating or as regeneration of the ground-source borehole field.
• Monitoring results of a highly integrated heat pump with different simultaneous operation modes for the building services including internal waste heat use for DHW preparation developed at Oak Ridge National Laboratory, USA. In field monitoring the air-source integrated heat pump prototype reached high overall performance in the different operation modes.