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Extending use of geothermal through storage of heat in aquifers

View over Stuttgart from Degerloch (source: ThinkGeoEnergy)
Alexander Richter 30 Jan 2017

Geothermal researchers from the Karlsruhe Institute of Technology in Germany are working on several projects that could utilise aquifers for storage of heat for use e.g. in winter times.

Harvesting the summer in the winter, or how one can store waste heat under ground for later utilisation has been recently covered in a rather interesting article in German publication Innovations Report.

While not exactly new, I first stumbled across this on projects by car manufacturer BMW that has been looking at a project like this, as well as some heat storage concept of the German parliament building in Berlin.

The storage of summer heat or the waste heat of industrial plants in subterranean, water-bearing layers – in so-called aquifers – is, for example, widespread in the Netherlands. At more than 1,800 locations, the neighbour country of Germany already implemented this technology. In Germany, there are currently only three sites with geothermal energy storage in groundwater conductors.

The most prominent example is the Reichstag building in Berlin (the Federal Parliament), which is supplied with warmth in winter and cold in the summer via several aquifers. Hamburg is currently planning an enormous aquifer heat storage facility, which will bring in the future over a quarter million households and commercial enterprises warm through the winter.

“In (the state of) Baden-Wuerttemberg, there is still no aquifer storage, even though the subsoil is well suited for energy storage in many areas,” says Professor Philipp Blum of the Institute for Applied Geosciences of the Karlsruhe Institute of Technology (KIT).

Aquifer reservoirs are water-bearing layers in the subsoil in which the water does not flow or hardly flows – so the heat is not transported away. They are tapped through boreholes to heat up the water in the subsoil with the waste heat from industrial plants or solar heat. The surrounding rock acts as an isolator. The stored heat can then be recalled by means of heat exchangers, if necessary, for example in the winter.

Such a system is planned for the surplus heat of a large swimming pool and adventure pool in Hockenheim/ Germany. The cellar rooms are heated up to more than 30 degrees Celsius all year round due to the heating system and the waste heat of technical installations.

This excess heat is now to be stored in a groundwater conductor during the summer months, in order to be available again in winter. Scientists of the Karlsruhe Institute of Technology (KIT) are coordinating the project and are developing a tailor-made and innovative monitoring and storage concept.

But waste water ducts or tunneling systems are also suitable as heat storage or cold storage. “The so-called tunnel geothermal energy for heating, cooling and heat storage is planned for the future elephant house of the Wilhelma Zoo in Stuttgart,” explains Blum, coordinator of the research project GeoSpeicher.bw.

“The new City Museum of Stuttgart will be able to manage its energy use efficiently due to waste water heating and cooling,” Blum continues. Within the framework of doctoral theses, the integration of tubular geothermal heaters into a heat-smart grid is being investigated, as well as the system integration of geothermal plants into an existing building and energy concept.

A total of eight geothermal energy projects in Baden-Württemberg will be scientifically evaluated and accompanied in the coming three years under the leadership of KIT. The topics range from innovative monitoring and storage concepts, detailed heat transport models, hydrogeochemistry studies, extensive system and optimization analyzes to tailor-made communication strategies. Regular workshops, conferences and trainings ensure a lively exchange of thoughts even across the institute’s boundaries.

Seven doctoral students from both the KIT and the universities of Heidelberg and Stuttgart as well as the universities of Biberach and Offenburg are involved in the various projects. Blum emphasizes: “A cross-disciplinary doctoral school ensures that building technicians, engineers, geologists and decision-makers learn from each other. To this end, we also invite experts from the Netherlands to build up strong competencies in this future-oriented technology in Germany. “

Philipp Blum outlines the goal: “Together with the involved municipalities, we want to create tangible demo and example projects with a broad public impact. That is why experts from the city utility companies of Hockenheim, Biberach, Überlingen, Bad Waldsee and Stuttgart are closely involved in the work right from the start. “

In the GeoSpeicher.bw project, scientists from the Karlsruhe Institute of Technology collaborate with colleagues from the universities of Heidelberg and Stuttgart, as well as the universities of Biberach and Offenburg.

 

Source: Innovations Report