The objective of Annex 61 is to investigate the heat pump solutions for cluster of buildings and positive energy districts.


Annex 61 studies the application of HP for clusters of buildings and positive energy neighborhoods (PEN) or districts (PED), respectively. A focus is on clusters of buildings and smaller districts, mainly with residential and office use. While a majority of project contributions concentrates on new built clusters or districts, quite some projects also focus on strategies to increase the energy performance of existing neighborhoods to approach a zero energy/emission balance, which is also in the scope of the Annex. Thereby, renovation strategies include both the improvement of the building envelope and the integration of HP, and optimized concepts of the combi¬nation of both approaches to improve the energy performance are to be evaluated.


In order to assess the heat pump potentials the Annex work follows a 4-step methodology divided into the following Tasks. Based on the state-of-the-art analysis of HP use in already existing clusters of buildings or Positive Energy Districts, a concept analysis for HP in PED is carried out. For promising concepts, a detailed techno-economic analysis is accomplished and backed-up by monitoring of HP operation in PED, which are evaluated in parallel to the concept analysis.

Task 1 – State of the art of heat pumps in positive energy districts
Starting from already existing HP systems in cluster of buildings, the state of the art is characterized and boundary conditions for the follow-on tasks are gathered. As Key Performance Indicators (KPI) CO2-eq.-emissions and further technical and economic KPI are considered. As result of Task 1 an assessment of technically realistic options for PED as well as an economic estimation of reachable ambition levels and the economic handicap could be evaluated. Therefore, standardized load profiles are generated and used for archetype district, e.g. entire residential use, mixed residential and office use etc. These archetype districts are to be characterized by the building quality reflected in the loads, the available renewable sources and the on-site energy production options.

Task 2 – Generic system concepts
In Task 2 the analysis of generic system concepts is performed. Starting from decentralized concepts on individual building level different categories to a central integration are defined, comprising a purely electric connections, a collective heat source, a semi-centralized integration in terms of mixed centralized and decentralized HP, e.g. a central SH HP combined with a “booster” decentralized domestic hot water HP up to a fully centralized HP integration. For each subsystem, a short technical characterization is elaborated. As result, an overview of generic integration options of the HP in districts with pros and cons and favorable applications as well as recommendations are foreseen.

Task 3 – Techno-economic analysis of promising concepts
Based on the favorable system concepts derived in Task 2 a more detailed techno-economic analysis is carried out, in particular regarding the design and control as well as integration with storage and other generators to optimize the HP operation regarding performance, renewable energy integration, system cost and energy flexibility. The detailed investigations are carried out by simulations where also modelling aspects of larger heat pumps are a research topic. Task 3 also serves to evaluate optimization potentials of real systems in monitoring in Task 4, which in turn yield operational and performance data to validate developed models.

Task 4 – Demonstration and monitoring
Task 4 is dedicated to the evaluation of the real performance of heat pumps in district applications and to the identification of typical optimization potentials in the real operation for the different heat pump integration options in monitoring. Moreover, a comparison and verification to simulated values is enabled by the real operational data and can in turn provide a benchmark and optimisation potentials by simulation based control optimisation.

Task 5 – Dissemination and communication
All task are accompanied by dissemination activities like workshops, articles, website information and presentations, which are summarized in an overarching Task 5.


Besides the final report expected deliverables of the Annex 61 comprise

  • State-of-the-art summary of heat pump application in positive energy districts in the participating countries
  • Assessment of the role of heat pumps in positive energy neighbourhoods
  • Generic concepts for heat pumps in districts
  • Techno-economic analyses of heat pump concepts in positive energy districts
  • Modelling of larger heat pumps for blocks of buildings (component level/system level)
  • Sizing methods for decentralized and centralised heat pumps in positive energy districts
  • Heat source integration as well as electric and thermal storage integration on district level (central vs. decentral)
  • Evaluation of control and flexibility options of heat pumps for groups of buildings/neighbourhoods
  • Renovation concepts to approach positive energy/zero emission balance with heat pump
  • Evaluation of monitoring projects of heat pump application in positive energy districts and districts with existing buildings
  • Dissemination of results at website, in publications, workshops and reports