Demo site for Mine Thermal Energy Storage (MTES).

In Bochum, currently abandoned mines formerly used for hard coal production are being transformed into a Mine Thermal Energy Storage (MTES). The MTES is to be installed at the Ruhr University technical centre and will be integrated in the university’s heating and cooling network. This grid is currently being fed with heat from gas fired boilers and a combined heat and power unit. We aim to do the following:

• Partly replace the current heat supply by reusing mine water from the abandoned Mansfeld colliery as a local and renewable heat source.
• Store waste heat at a level of approximately 30 °C into the MTES.
• Boost the temperature up to more than 90 °C when needed to meet demand by using a heat pump.

Project details

• Location: Ruhr University Bochum
• Energy infrastructure:
  • Local heating grid of the Ruhr University Bochum, currently supplied by two combined heat and power units with a total of 9 MW operated by Unique Wärme GmbH.
  • Three peak boilers with a total thermal output of 105 MW, located at the university’s technical centre.
  • Local heating grid also supplies heat for approximately 4800 apartments, 760 houses and 115 other buildings (industrial clients).
  • Temperatures: 80-120°C (depending on the outside temperature).
• MTES heat source: Waste heat from the technical centre / data centre (700 kW peak load).
• Objectives of the demo site:
  • Integrate concept to reuse waste heat at the site as well as technical possibilities and its limitations, respectively.
  • Demonstrate storing surplus heat from technical centre and/or surplus return temperature from heating grid to the MTES.
  • Increase the heating grid efficiency by using smart district control.
  • Confirm the target storage capacity: 2-8 TJ. This should be proved by carrying out push & pull-tests to validate the performance of the MTES before a commissioning will be done.
  • Calibrate a site-case-model by generated subsurface data (i.e. production rates as well as load/unload curves) to prove the performance of the whole system.
  • Follow-up heat pump dimension after MTES test operation.
• Status:
  • Fraunhofer-IEG started fieldwork (drilling and testing operations) in September 2024. Read the update here.

Integration
The power plant of the university district heating grid is situated 300 m Northeast of the MTES pilot site developed in the HEATSTORE project. The project outcome and lessons learned from this pilot site will be used for the PUSH-IT project. The site will be developed primarily by Fraunhofer Research Institution for Energy and Geothermal Systems (IEG) with full support of the Ruhr University facility management. The previous pilot incorporates local buy-in from nearby industry stakeholders, and housing, providing opportunity for residential input into the project as well. The area’s historic colliery is also likely to positively influence public perceptions of the project making the site relevant from a social science perspective.