Development of a technically and economically feasible thermal storage concept for the use of mines as heat storage.
Seasonal heat storage in decommissioned coal mines has not yet been put into practice in North-Rhine-Wesphalia or in Germany, which means that the Geo-MTES (Mine Thermal Energy Storage) project of the International Geothermal Energy Centre (GZB) at University of Applied Sciences Bochum (in cooperation with RAG AG and delta h) is a trailblazer in the field. The research project Geo-MTES stems from the “Förderinitiative Energiespeicher“, a joint initiative from the BMWi, the BMU and the BMBF to promote the development of energy storage solutions. The central objective of the Geo-MTES project (feasibility study) is the development of a technically and economically feasible thermal storage concept for the use of the colliery “Prosper Haniel” as a heat storage facility. The concept envisages the seasonal storage of residual heat from industrial and power plant processes, and/or from the solar thermal energy generated in the colliery brownfields nearby, in the mine infrastructure, and to use it as needed in the winter months for heating commercial and residential buildings, if necessary over existing district heating networks.
To establish such underground heat storage systems, the mine infrastructure must be converted accordingly, and the appropriate operational systems must be developed. A necessary requirement is the availability of a mine that is fully accessible and, if possible, active. The hard coal mine “Prosper Haniel” remains fully accessible until the end of 2018, so that it is possible to develop and establish specific heat storage concepts. The basis of a seasonal heat storage system in the “Prosper Haniel” mine are the year-round rock temperatures of 30-50°C, thanks to shaft depths of up to 1200m. The mine’s network is 141km long, spread over 165km2, which creates a very large volume available for storage in the mine infrastructure.
Seasonal underground heat storage must have a large volume because it needs to store immense amounts of thermal energy, it must be reliable, economical and able to be integrated into existing structures. The materials and structures have to meet very high specifications, which are required by the conditions in the underground storage system, namely, high thermal stress, condensation, and the structural cross section stability of the mine. The materials and structures used must guarantee an operating life of 40 to 50 years to allow the amortisation of the heat storage system. The system needs a thermal energy producer to deliver thermal energy and, depending on the producer and the application scenario, the storage and the system can undergo different heat outputs, mass flows and temperature levels. All the affected components (storage construction, charging and discharging facilities, pipe dimensions, pumps, etc.) have to be suited to the planned operating conditions and the resulting stresses. If different producers supply the heat storage facility, it will be necessary to carefully coordinate the amounts of heat and the charge and discharge schedulles of each producer. Furthermore, the feasibility study has to study the possible effects of seasonal heat storage on the physical properties of the rock formations. Additionally, a seismic, geochemical and energy monitoring system for a pilot facility will be developed to register and assess the possible geological hazards.
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Information on funding and further project participants
Funding code: FKZ 03ET1193A