Heat Pump efficiency in old single-family houses: Interim results of large-scale field trial [24]

Within the BMWi-funded project "WPsmart im Bestand" (FKZ: 03ET1272A; https://www.ise.fraunhofer.de/de/forschungsprojekte/wpsmart-im-bestand.html), the ecologically appropriate use of Heat Pumps in existing houses was demonstrated in a broad field study. In the BMWK-funded follow-up project "WP-QS im Bestand" (FKZ: 03EN2029A; https://www.ise.fraunhofer.de/de/forschungsprojekte/wp-qs-im-bestand.html), the measurement is continued under consideration of further research questions (e.g. noise of outdoor air Heat Pumps and PV self-consumption).

The main focus continues to be on the analysis of efficiency and operating behavior, taking into account the individual conditions in each use case. Up to 75 Heat Pumps (approx. 1/3 from "WPsmart im Bestand" with partly new Heat Pumps and approx. 2/3 new measurement objects) will be examined until at least mid-2024.

 The outdoor air and ground source Heat Pumps are used for space heating and domestic hot water heating and are installed in buildings built between 1826 and 2001. The condition of the buildings ranges from unrenovated to nearly fully renovated and different types of heat transfer systems are installed.

The measurement concept includes minute-by-minute logging of the measurement data. On the electrical consumer side, the drives in the heat source (brine pump or fan) as well as the distribution pumps are logged in addition to the compressor, control and electrical back up.

In the hydraulic circuits of the heat source and the heat sink energy, power, volume flow and temperatures are measured.

The contribution to the European Heat Pump Summit covers the efficiency analysis of an interim evaluation period considering around 40 to 50 HPs. Considering a 12-month evaluation period (e.g. the period July 2022 to June 2023) the focus is on the annual performance factors and the directly quantifiable efficiency influences, such as the system temperatures and the required auxiliary energies. Furthermore, the year of construction, the installed heat transfer systems as well as a roughly assessment of realized renovation measures (detailed analyses will not be completed at the time of the conference) will frame the measurement data.