Climate-friendly energy generation thanks to medium-depth geothermal energy
Unique in Germany - aquatherm pipelines part of the project
A groundbreaking project has been launched in Schwerin: Stadtwerke Schwerin has put its first geothermal plant into operation. The plant, which is the only one of its kind in Germany so far, combines medium-depth geothermal energy and heat pumps and has a special relevance: In the future, 15 percent of the district heating in Schwerin will be generated in a climate-friendly way by using the renewable energy. Piping systems from aquatherm are part of the project.
Geothermal energy is an inexhaustible source that can be extracted all year round, regardless of climate or season. Stadtwerke Schwerin has a well-developed district heating network in the city. Thus, the use of geothermal energy is a consistent step towards sustainable and climate-friendly energy production.
The geological conditions at the site in Schwerin-Lankow are particularly favourable for the operation of the plant. At a depth of about 1,300 metres there is water with a temperature of about 56 degrees Celsius, brine to be precise, with a salt content of 15 per cent. For heat generation, this water is brought to the surface with the help of a powerful pump. The geothermal energy is then extracted through heat exchangers and, in a first step, heated to around 80 degrees Celsius by four heat pumps. Depending on the outside temperature, the water temperature is only increased again if necessary and then fed into the district heating network. The cooled thermal water is fed back into the same rock layer via an injection pipe, creating a closed circuit.
The entire piping in the machine house of the geothermal heating plant, including the connection to the heat pumps, was carried out with aquatherm blue in dimensions up to 200 mm in diameter. In this case, the installation of this plastic pipe system from aquatherm offers several advantages over other systems. "Thermal waters, such as those produced in the North German basin, place special demands on the piping material," explains Dr.-Ing. Frank Kabus, Managing Director of Geothermie Neubrandenburg GmbH as the consulting and planning office for the project. "Due to the high mineralisation of up to 300 g/l, the corrosion resistance of the material is of course an essential aspect. In addition, for geochemical reasons, a permanent overpressure of several bar must be maintained in the pipe system - and that at temperatures in the range of 50/70 °C. aquatherm blue made of the plastic polypropylene is an ideal solution under the conditions encountered. Oxygen access to the thermal water, normally a disadvantage of plastic compared to metallic pipes, can be prevented in this case by integrating a diffusion barrier. This is essential because otherwise particle formation can occur in the thermal water, which creates injection problems in the subsurface over time."
Dr. Kabus sees another advantage in the processing of the system: "Since the pipes are joined by welding, there are no weak points such as gluing. Especially with buried pipelines and the fact that the thermal water has a water hazard class, this advantage cannot be dismissed."
