WINZER

In Germany, renewable energy sources have been steadily expanded for more than 20 years. The share of renewable energies has grown steadily, especially in the electricity supply. However, the supply of regenerative heating and cooling is stagnating. A central problem here is the lack of seasonal storage options, e.g. to use solar surpluses from the summer to cover higher demand in the winter. On the Fraunhofer IEG site in Bochum, the near-surface IEG small coal mine has already been developed with three boreholes in order to use it as a future heat storage facility. In addition, a solar thermal system with a capacity of 30 kW has already been installed, allowing the uplifted mine water to be heated up to 60°C and re-injected (stored).

Project contents
The existing plant in Bochum will be used as part of the project to carry out overall condition monitoring. From this, findings on the hydrochemical, microbiological, geomechanical and groundwater economic condition of the mine water will be derived. In addition, the plant components will be examined in relation to cyclic operation. Based on the conclusions to be drawn, concepts and technologies for the feasibility and optimization as well as the safe operation of heat storage facilities in former coal mines can be derived.
The project has the following overall goals:

• Demonstrating the potentials and challenges of mine heat storage in urban agglomerations under various non-ideal boundary conditions
• Testing and implementation of transferability to other locations
• Investigation of the specifics of different coal types with regard to pollutant mobilization in relevant temperature ranges

delta h is entrusted with the accompanying numerical modeling. In addition to the construction and validation of the TH models at the various locations, heat storage scenarios within the plants are also being investigated.

Project partners
The project is managed by Fraunhofer IEG in Bochum. In addition to delta h Ingenieurgesellschaft, the Ruhr Universität Bochum (Chair of Urban Water Management and Environmental Engineering, Chair of Hydrogeochemistry and Chair of Geothermal Energy Systems) and the TU Bergakademie Freiberg are part of the project consortium.