No coal mine was ever really been considered as an underground seasonal pit heat storage tank in a pilot plant before. As part of the Energy Storage Funding Initiative, funded by the Ministry for the Economic Affairs and Energy (BMWi) and the Federal Ministry of Education and Research (BMBF), the research project GeoMTES (Mine Thermal Energy Storage) now takes that missing step. Researchers are currently investigating how suitable the still active hard coal mine Prosper-Haniel in Bottrop, in the Ruhr area, is for the storage of seasonally available waste heat. The idea is to feed unused waste heat from industrial and power plant processes as well as solar heat in summer into the lower levels of the coal mine. This heat could be used in winter to supply the surrounding residential and commercial areas.

The aim of this project is to develop storage concepts that are technically and economically feasible. To this end, a feasibility study is to be carried out until September 2018. The modelling of the pit infrastructure – i.e. the shafts, galleries, routes and extraction areas – has already been completed. In this context, a numerical heat transfer model was created with a programme for mapping hydraulic and thermal processes in potential heat storage tanks.

With its 141km long network of routes and the 165km² extraction site, which will still be accessible until at least the end of 2018, the Prosper-Haniel mine is perfectly suited for the research project. Mines that are to be used as storage tanks must be fully accessible. The reason for this is primarily the infrastructure measures needed. The high population density in the immediate vicinity of Prosper-Haniel means that in winter heat consumption by a large number of consumers would be ensured.