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15:10-15:30 Uhr - Forum 1

Study on HTHP coupled with HT-MTES

Arianna Passamonti1, Florian Hahn1, Frank Strozyk1, Gregor Bussmann1, Torsten Seidel2, Rolf Bracke1
Fraunhofer IEG, Germany; 2delta h Ingenieurgesellschaft, Germany


Motivation of the paper

The heavily populated region of North-West Europe (NWE) has inherently an elevated thermal energy demand, and, to achieve the 2030 EU targets, NWE is required to decrease CO2 emissions produced by fossil fuel fired power plants.

To reach these goals, Germany planned the phase out of coal latest by 2038. The need for alternative sustainable and renewable solutions is therefore of major relevance, especially in the areas that largely rely on coal such as North Rhine-Westphalia.


With this motivation, two projects were initiated: Geothermica HeatStore and NWE-Interreg DGE-Rollout. Within HeatStore, the development of a high temperature mine thermal energy storage (HT-MTES) pilot plant is planned. During the summer, solar thermal energy will heat the water present in an abandoned small mine situated at the premises of Fraunhofer IEG. As part of the DGE-Rollout project, during the heating season, the water present in the mine will be the source for a high temperature heat pump (HTHP) that will be connected to the high temperature district heating (DH) grid.

What was done

Through a collaboration between Fraunhofer IEG and delta h Ingenieurgesellschaft, best drilling spots for extraction and injection wells were proposed. Subsequently, the drilling phase is planned to start in mid-June 2020. Theoretical hypothesis on the volume of water present in the mine were performed to determine its capacity.

Consequently, different solutions for large scale heat pumps, HTHP’s for DH applications and possible refrigerants, were individuated. Market readiness and available solutions were analyzed.

Considerations on dimensioning and required characteristics for the HTHP were drawn.

How it was done and validated

Simulations to choose the best drilling spot and the heat transfer within the mine were completed.

Literature review to determine the state of the art of current heat pump operational installations and available products on the market was concluded to individuate existing solutions applicable for this project.

Simplified computational models to determine performances of different refrigerants under the different source and sink working conditions were developed. Energy balances to determine the heat pump dimensioning were performed.

Major results

Major results include the individuation of the best drilling spots for the HeatStore project, knowledge gained on the large scale HTHP application and determination of requirements for the needed technology.

Next steps will be drilling and pumping tests, eventual HTHP requirements updates, HTHP installation and testing.


With the development of the projects, it will be possible to prove the exploitation of abandoned mines as heat storage facilities and having them coupled to heat pumps will lead the pathway for the needed energy conversion towards the CO2 reduction goals.

Präsentation (PDF)

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