Multi-WP

In order to achieve the heat transition, locally available, non-fossil heat sources are of great importance. Outside air is one such heat source that is available everywhere and is already frequently used for heat pumps. Seasonal storage offers the opportunity to make better use of heat resources that are available for a limited period of time.

Both technologies can benefit from each other in combination: Air source heat pumps have experienced high market increases in recent years, but usually have lower efficiency figures (seasonal performance factors) compared to heat pumps with other sources. Seasonal storage tanks require heat sources for regeneration (reheating) to stabilize the temperature in the long term.

Contents and objectives

The aim of this project is to significantly improve this situation by combining air source heat pumps with geothermal probes as large-scale storage units, both for seasonal and short-term load shifting, in order to decouple generation and consumption over time. The air source heat pumps can be operated in such a way that they work from a certain outside temperature or when using PV, depending on the available solar yield.

Methodological approach

In this project, multi-WP systems - air source heat pumps with PV system and seasonal storage - are designed for various case studies (different energy consumption, mixed use, etc.) and optimized as part of a variation calculation. Furthermore, a comparison is made with heat pump systems without seasonal storage (air mono/bivalent, groundwater and ground) in terms of efficiency/working number as well as economic and ecological aspects.

In the case of seasonal storage systems, excessive heat demand can lead to undercooling of the subsurface; a seasonal heat balance is essential. Aspects such as conflicts of use, lock-in effects and noise pollution caused by air source heat pumps are addressed on the basis of the case studies. The project results will be prepared for political decision-makers, heating network operators and property developers/builders and disseminated in various articles and events.

Expected results

The aim of the investigations in this project is to improve the overall efficiency and cost-effectiveness of heat pump systems through load shifting. In addition, locally available heat sources can be used for heat generation regardless of location.

The realization of this project opens up another market segment for air heat pumps, moving away from the focus on the simplest and cheapest possible installation in renovation projects towards a particularly efficient way of using environmental heat in new build and renovation areas. The efficient development of air as a heat source in combination with seasonal storage significantly expands the possibilities for using locally available, non-fossil resources.

Client	FFG, BMK
Project management	Franz Zach
Project partner	Ochsner Process Energy Systems GmbH (OPES) Geologische Bundesanstalt (GBA)
Project duration	November 2021 to April 2024