Status: 04/28/2023 08:22 a.m
Stadtwerke Schwerin are opening a geothermal heating plant today. The geothermal project in the Lankow district is intended to supply 2,000 households. The plant costs 20 million euros. This is how it looks there.
Stadtwerke Schwerin are opening a geothermal plant today. Among others, Federal Chancellor Olaf Scholz (SPD) and Mecklenburg-Western Pomerania’s Prime Minister Manuela Schwesig (SPD) will attend the inauguration. The bosses of many other urban energy suppliers from all over Germany also want to be there. They want to know how Schwerin manages to get so much thermal energy from a comparatively shallow depth and with comparatively cold water.
Warm water from a depth of 1,296 meters
Engineer Benjamin Kielgas is the geothermal foreman in the new plant and stands in the well house. “We’re getting water at a temperature of 56 degrees here from a depth of 1,296 meters. That’s thermal brine, it consists of 15 percent salt,” says the Stadtwerke man. The fountain house is about the size of a gazebo, inconspicuous. The water arrives here from a depth of more than a kilometer: the thermal water will flow in a blue-green plastic pipe with a diameter of 20 centimetres. Before Schwerin residents can heat their homes with geothermal energy, a few more steps are necessary.
Final work before the pumps start
The analog pressure and temperature displays are still not deflecting. Shortly before the inauguration, the lamps will be installed here, but the essentials are ready: the depth pump was installed in the borehole a few days ago. “We used a feed pump at a depth of 250 meters, which pushes the water up so that we can use the thermal energy. It goes into our plant and is processed there,” says Kielgas, describing what is happening deep below Schwerin.
heat pumps and heat exchangers
The pump conveys the water from a rock layer that contains the valuable thermal water and into which it is finally pumped back: a cycle. First, however, the hot deep water flows from the well house into the geothermal power station. Special precautions are necessary for this: Because of the salt content, the thermal water must not be released into the environment under any circumstances, says engineer Kielgas and opens the door to the geothermal power plant. Heat exchangers and heat pumps are located here.
Thermal water heats up heating water
The three heat exchangers are reminiscent of beehives, and the titanium surfaces consist of thousands of honeycombs. A single exchanger has a surface area of 300 square meters due to the many honeycombs, explains Benjamin Kielgas: “In the refrigerator you also have a heat exchanger that extracts the heat from the refrigerator and releases it to the environment. And here we extract the heat from the thermal water and give it to it to the water of the intermediate circuit.”
Series connection: heat pumps heat up water
Plant manager Benjamin Kielgas and public utility spokeswoman Julia Panke at the heat exchanger in the geothermal plant.
The cooled thermal water can be pumped back underground one kilometer away, it has done its job. The heating water in the intermediate circuit flows on to large heat pumps in the machine hall next door. The pumps are reminiscent of old steam locomotives with their large black boilers. In summer they bring the heating water up to around 80 degrees. Four pumps are connected in series, says Kielgas; so they would get by with just 56 degrees Celsius, with which the deep water arrived up here.
Disadvantage of geothermal heat: Energy requirement of heat pumps
But the four large heat pumps are also energy-hungry, and that’s the catch at the moment. The municipal utilities therefore need additional energy. “We have two combined heat and power plants, each with an output of one megawatt. Our geothermal power plant, the entire system with deep pump and heat pumps, consumes around 1.7 megawatts. The two combined heat and power plants are sufficient, the rest goes into the grid,” explains Kielgas. “The electricity is normally generated from natural gas, but will be converted to biomethane in the future so that we have green energy here at the Lankow site.”
The Schwerin underground offers the possibility to tap the hot thermal water in several places. The public utilities are already planning another geothermal plant. In order to find other locations, the underground must be examined in more detail.
