With the loss of coal and natural gas combustion, district heating needs a new energy source [in Germany and beyond]. Herefore geothermal energy is a suitable replacement, in former mining regions even with the heat of mine water as a suitable option.
How to optimally utilise the potential s the focus of the work of Prof. Dr. Rolf Bracke. On May 1, 2020, he was appointed to the new chair for geothermal energy systems at the Faculty of Mechanical Engineering at the Ruhr University Bochum (RUB). He is also head of the new Fraunhofer Institute for Energy Infrastructures and Geothermal Energy, IEG for short, which started work in early 2020 and into which the Bochum International Geothermal Center was integrated.
“With the joint appointment of Rolf Bracke, the RUB not only consolidates the association with non-university partners,” said Prof. Dr. Andreas Ostendorf, Vice-Rector for Research, Transfer and Young Researchers at RUB. But “we are also increasing the visibility and attractiveness of Bochum as a research location.”
Mine water can provide heat
“Germany has a gigantic district heating infrastructure, which today is fed with heat from the combustion of hard coal and lignite, waste heat from the steel industry and to a lesser extent from waste incineration,” explains Rolf Bracke. If coal combustion ceases and more and more waste is recycled, new sources of heat have to be used, and this already in the next 15 years. Deep geothermal energy and – especially in the Ruhr area – heat of the mine water are possible.
New drilling techniques and heat pumps
One of the challenges for research is to develop new drilling methods that allow it to penetrate quickly and safely to a depth of four or five kilometers. “For example, we work with laser or plasma technology,” says Rolf Bracke. The technical applications relating to the use of deep heat also need to be further developed. It’s about high-temperature heat pumps.
“You have to be aware that burning fossil fuels releases a temperature of more than 600 degrees Celsius, whereas today’s district heating networks only need hot water with a temperature of around 100 degrees Celsius. This means that most of the fossil heat cannot be used at all, “says Rolf Bracke.”
To decarbonise the heating systems with geothermal energy, drilling has to be carried out to a depth of three kilometers – that’s where the natural thermal water has this [sufficient] temperature. Or you use warm pit water with a temperature of around 35 degrees Celsius directly or if necessary heat it up even further. This turns a mine into a seasonal heat store in summer for useless waste heat from cooling systems of buildings or industry. High-temperature heat pumps then bring the pit water preheated to 70 degrees to district heating temperature of over 100 degrees. This way coal mining and its legacies can become the basis for modern heating systems for the next generation, “continues the researcher.
Rolf Bracke studied at the Rheinisch-Westfälische Technische Hochschule Aachen and worked for a long time in the private sector before becoming a professor at the Bochum University in 2002. As part of his international research, he established the Bochum Geothermal Center as an outstanding institution in this field. “He has thus laid the foundations for the new Fraunhofer IEG facility,” emphasizes Vice-Rector Andreas Ostendorf. During this time, he was already connected to a number of collaborations with RUB scientists.
For example, he has successfully established the “Applied Research on Geothermal Energy Systems” graduate school with the Faculty of Earth Sciences at the RUB on the Bochum University of Applied Sciences and is also a member of the research departments “Subsurface Modeling and Engineering” and “Closed Carbon Cycle Economy”. With the Faculty of Civil and Environmental Engineering and the Faculty of Mechanical Engineering, Rolf Bracke has already carried out a large number of cooperation projects.
“The structure of the chair at the RUB is particularly exciting for me because it is about combining engineering with geosciences and materials research,” says Rolf Bracke. “It is a real interface task that RUB can prove with its motto ‘Creating Knowledge Networks’.”
Visible strength of city and region
With the appointment of Rolf Bracke, the RUB has further intensified the joint appointments with all major non-university research organizations in Germany. The new Max Planck Institute for Cybersecurity and Privacy, which was approved at the beginning of 2019, is under construction and has already started research with the appointment of the first founding directors.
The new Fraunhofer IEG facility is being jointly operated with the Fraunhofer Institute for Environmental, Safety, and Energy Technology in Oberhausen, with which the RUB has enjoyed long-term close cooperation, in particular research on regenerative energy systems and the energy transition in Germany and Europe at the Reinforce RUB considerably. This synergy potential also increases the attractiveness and international visibility of the science city of Bochum and the research region of the Ruhr area.
Source: Ruhr-Universitaet Bochum