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Questions and answers: The Stadtwerke Kaiserslautern (hereafter SWK) are exploring the subsurface beneath the city and district for geothermal energy opportunities. For this purpose, large trucks will be on the road in December. What can the population expect?
What are the municipal utilities planning in terms of geothermal energy?
The SWK wants to know whether geothermal energy, i.e., energy from the earth’s interior, is an option for supplying heat for the population of Kaiserslautern and the surrounding region. “We are investigating whether geothermal energy can be a base load alternative for our district heating,” said SWK Managing director Arvid Blume. The project is called “Pfälzer Wärme” (Palatinate Heat). Information on this can be found on a website of the same name www.pfaelzer-waerme.de.
How will measurements be carried out?
“We are collecting endless amounts of data,” said SWK Man-aging director Blume. To this end, mea-sure–ment teams are expected to be out and about from the beginning of December, covering an area of around 150 square kilometers and, roughly speaking, surveying the subsurface. This is carried out on behalf of SWK, by the company DMT.
DMT is the Deutsche Montan Technologie, based in Essen, Germany. Around 100 DMT employees will be involved in the project, reported geologist Uwe Baaske, project manager of SWK. The seismic survey teams are easily recognizable by their large vehicles, known as vibro trucks, “Maximum transparency is very important to us,” said Blume with regard to the measurements.
How does the measurement/seismic survey work?
The vibrotrucks drive through the area of interest and send sound waves into the subsurface at predetermined locations. According to Baaske, four measurement teams will be deployed in the region, each with two vibration vehicles. The sound waves are reflected by rock layers in the subsurface, which are then recorded by small sensors, called geophones. The geophones were laid out at the end of November before the trucks began their tours. The data collected will be used to create a view of the earth’s interior and reveal its geological structure. Baaske compares the measurements to computer tomography in medicine. In preliminary investigations, 27,000 measuring points and around 17,000 vibration points were identified in the area. These are processed by DMT’s teams starting December for the duration of about two weeks, dependin on weather conditions.
What can the population expect when the large trucks drive through the city and villages?
“The most annoying thing is the noise,” says Uwe Baaske. When the measurement teams drive through the streets, they generate noise that is remotely comparable to the passage of garbage trucks. The measurement process itself, when the trucks generate vibrations that are transferred as sound waves into the earth, takes about one and a half minutes, Then the truck moves on and depending on the length of the street, it can take up to an hour and a half to measure an entire street. “It’s a kind of mobile construction site,” said Baaske, referring to measurements on major traffic routes such as thoroughfares.
What rules and regulations do the experts have to follow when taking measurements?
Regulations and permits for the seismic project are laid down in the main operating plan, which has been approved by the State Office for Geology and Mining, Uwe Baaske explained.
What are the devices that are being laid out? What happens to them?
The devices, passive seismic sensors, resemble a cube with a stem, with an edge length of about 15 centimeters. The geophones contain technology that is essential for measurements. They are laid out and collected after the survey process and around 10,000 devices are in use and reused in the course of the seismic survey. By mid-December, all geophones will have disappeared from the landscape. According to Baaske, the devices use GPS to record exactly where they were laid out and which vibrations were registered. The collected data is then read out, the geophones do not transmit data on their own, Baaske assured us. The vibro trucks only travel on public roads and tracks.
Will geothermal energy definitely come to Kaiserslautern?
According to SWK board member Arvid Blume, “geothermal energy could be a way to supply district heating.” Whether this will happen also depends on the results of the investigations. The seismic investigations are intended to provide the data basis for such a decision. Deep geothermal energy must be “reliable and affordable and needs to be properly evaluated,” he emphasized.
What is the schedule?
Measurements began Dec. 1 and are expected to last until mid-month. The measurement teams work Monday through Saturday from 7 a.m. to 6 p.m. After final evaluation a decision to continue with the geothermal project will be made.
