What happens to mines that are no longer in use? Could they be used to store heat? Researchers are hoping to find this out and are conducting tests in the former Prosper-Haniel hard-coal mine in Bottrop to investigate whether it is suitable for underground heat storage. The GeoMTES research project is developing storage concepts for this purpose and a feasibility study will be carried out by September 2018. The modelling of the pit structure has now been completed.

The idea of drawing thermal energy from existing and disused coal mines is not new. Up to now, the possibility of storing heat in a former hard-coal mine has not yet been studied using a pilot plant. The aim of thermal storage in the pit structure of a mine is to store solar-generated heat and exhaust heat produced in a seasonal manner by industrial processes and power plants (mainly from combined heat and power generation) underground and to use this energy for heating residential and commercial buildings in wintertime. To this end, a feasibility study is being prepared within the framework of the GeoMTES project of the German government’ s Energy Storage Funding Initiative. The main aim is the development of a heat-storage concept that is implementable from both an engineering and economic viewpoint for a new form of use of the former Prosper-Haniel mine in Bottrop.

Prosper-Haniel mine as a research site

For the establishment of underground thermal storage facilities, appropriate infrastructure measures must be realised within the pit structure, i.e. the shafts, galleries or tunnels and excavations on different levels of the mine, and suitable development and conveying systems must be created. The hard-coal mine still has to be fully accessible for this purpose. For Prosper-Haniel, this is guaranteed until the end of 2018. There are 141 kilometres of underground routes and a total mining area of 165 km² in the Prosper-Haniel mine, and thus a heat-storage system with a large volumetric capacity is feasible inside the pit structure. Due to the high population density in the area around the mine, there is a good market that could take up the heat stored underground. The 7th mining level adjacent to Prosper-Haniel shaft 10 is currently being considered as a seasonal heat storage facility. Surplus heat from a biogas CHP could be stored there in summer and then used in winter for building heating and hot water provision via a local heating network in Bottrop-Kirchhellen. Coupling with the Ruhr district heating network is also conceivable.

“Mining model” as concept basis

At an inlet temperature of 90 °C and a rock temperature of approx. 30 to 50 °C at a depth of 1,200 m, the seasonal heat storage system uses temperature differences of up to 60 Kelvin. The basis for planning is a detailed numerical model of seasonal heat storage within the pit structure. To calculate the heat transport, the researchers use the SPRING programming system to create a numerical heat transport model that reproduces the hydraulic and thermal processes in the thermal storage system. This work has now been completed.

Further information on the GeoMTES research project can be found on the websites of the International Geothermal Centre at Bochum University of Applied Sciences and delta h Ingenieurgesellschaft mbH.

(fr)