The 8th Annex 61 working meeting was held at Alma Mater Studiorum University of Bologna on April 7-8, 2025. Attendees of AT, DE, CH, IT and JP participated onsite while the USA and further participant of AT and DE joined online.
On the first day interim result of the national contributions were presented and discussed. A simulation study of HP integration in district heating grids to lower grid temperatures with increasing integration of new or retrofitted buildings is performed by AEE-Intec, AT. With growing number of new built buildings and building renovation the temperature level of the district heating can be reduced. Remaining old buildings can be equipped with booster HP to supply the higher temperature level. Benefits are less grid losses, a higher share of renewable integration, options for higher waste heat usage and an increased redundancy, since multiple heat supply can be available. However, there can also be rebound effects, that with higher reduction of heating demand by heat pump integration, there might be too less remaining demand to operate the district heating economically.
A comparison of HP integration on building or block level by simulation has been evaluated at the University of Innsbruck based on monitoring data of the “Campagne” district. As a result, the SPF can be increase up to 0.5..1 SPF points due to reduced losses, lower temperature lift and less auxiliary energy for in building-wise integration. The economic situation could also improve, since less pumps and heat exchangers are required and the price of four smaller HP compared to one larger HP should not differ too much. Furthermore, new investigations on HP source integration and case studies on HP integration as peak load coverage for district heating has been presented by Switzerland. In Italy spread of district heating and heat pumps in Emilia Romagna region has been evaluated in detail and a tool for the local energy demand in districts are developed, which can be extend to the city level. Japan presented contributions to the state-of-the-art report, which will be amended after the meeting and case studies of district heating in Japan.
Another focus of the meeting was on the discussion of HP integration options for districts from decentralized to the centralized integration. Different integration options have been discussed and will be further investigated by simulation case studies and the evaluation of monitoring results. In this context also a collaboration with Annex 62, which investigates the HP integration for multi-family buildings, has been set up as exchange between the Annexes. The objective is to recommend favourable solutions depending on the application case.