Respectively, the paper summarises simulation activities in the IEA HPT Annex 61 in the different Annex tasks. After the general outline of the Annex tasks, a simplified modelling as a means to generate load characteristics for an evaluation of Positive Energy Districts (PED) in an early planning stage is described. The modelling has been developed at the University of Innsbruck. Hand in Hand with this load characteristic generator, archetype PED have been defined based on residential and mixed use of residential and office buildings as well as new built and retrofit application.
More detailed simulations are applied in the Annex 61 linked to the monitoring systems. As examples, projects from Germany and Switzerland are presented in the paper:
A problem in districts in particular in dense urban areas or for retrofit applications is the accessibility of sufficient and high-quality heat sources. In Switzerland a project for the 200 kW boiler replacement in two large multi-family buildings has been investigated by simulations. Due to drilling space and depth restrictions a ground-source-only application was not possible. Thus, a combination of the ground-source for peak load coverage and outdoor air source as a base load coverage and regeneration of the ground has been simulated. Simulation results confirm, that the combination of the two sources can provide enough heat source for a monovalent boiler replacement by two-indoor installed propane heat pumps, if the ground is only applied in peak load operation. The system will also be monitored in the upcoming winter period.
In Germany at the Technical University of Nürnberg, also a retrofit application is studied. A model retrofitting of a multi-family house of a social housing company is investigated by simulation and monnitoring. The ground-source heat pump is linked to transfer stations for space heating and DHW in each of the 32 flats. Temperature optimisations for the DHW operation and control strategies have been investigated by simulation. Additonally, also a cost comparison of a PV self-consumption and an entire grid feed-in have been performed. Simulation results confirm that the transfer stations enable to lower operating supply temperature and a self consumption can save 6-13% of the electricity cost. Further simulations regarding model predictive control are ongoing.
Also in Germany a concepts for the retrofitting of an existing district has been investigated by simulations. In the district Rusdorfer Kamp in Heide, a densification with new buildings and a connection of old building to a new heating grid is used as measure to energy improvement of the district. It is expected that 134 buildings are connected to the new grid, of which 47% are existing buildings. The system configuration consists of the central air-source heat pump (HP) and a combined heat and power (CHP) unit as second heat and power generator. A large PV system of 700 kW is the primary electricity producer for the heat pump. A back-up gas boiler is used in case that peak load cannot be covered by the HP and CHP. Furthermore, a battery as electric storage of 450 kWh and a heat storage of 500 m3 buried in the ground are included in the system. Mainly for scientific reasons, a small electrolyser is included as well in order to investigate how the produced hydrogen can be used in a fuel cell in the district or fed in the gas grid. The simulations confirmed that more than 50% of the energy demand can be covered by the HP with PV electricity. The rest is covered by the CHP unit. If grid electricity is used for the heat pump operation a much larger fraction can be covered by the heat pump. The realisation of the systems and the grid is still in the decision process regarding the financial viability.