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15 Jun 2020, 09:20
Paul Hockenos

Germany’s geothermal sector is struggling to take off

Model of Schäftlarnstraße geothermal heating plant in Munich
A model of how the Schäftlarnstraße geothermal heating plant in Munich will look when finished. Photo: SWM

While geothermal energy is a viable alternative to curb emissions for heating and cooling, fears and high costs have limited its expansion. But Bavaria and now Baden Wurttemberg are forging ahead. The potential of geothermal energy, especially for heating, is particularly enticing.

In Munich, south of the city centre along the Isar River, one of the largest geothermal heating plants in Europe is under construction and on schedule to begin supplying 80,000 citizens in the Bavarian capital with heat and cooling services in 2021. The Schäftlarnstraße plant is one of six in total that by 2035 will supply much of Munich's 1.5 million citizens with heat, and many of them also with cooling and some even with electricity, too. Alongside Paris and other European cities, including Hamburg, Aachen, and Potsdam in Germany, Munich is intent on tapping the vast energy potential of the hot thermal waters that flow beneath the earth’s crust in order to hit ambitious Energiewende (energy transition) targets, especially in Germany’s fossil-fuel-dominated heating sector.

“Munich’s is the most advanced geothermal strategy for district heating in Central Europe,” says Andre Deinhardt of the German Geothermal Association (BVG), an umbrella group for the industry. “The rest of Germany’s cities are today where Munich was 20 years ago. But many want to catch up,” he says.

“We’re simply very lucky that Munich and regions to its south in the Alps’ foothills are located atop huge reservoirs of thermal water at depths that we can access safely,” says Michael Solic of the city’s municipal utility Stadtwerke München, who notes that natural gas explorations done decades ago told the city about its geothermal trove. The city expects eventually to provide about 560,000 urban households connected to district heating systems with space heat and hot water. In light of ever-hotter summers, the city is also expanding district cooling networks.

Munich’s geothermal fleet counts among Germany’s 37 deep geothermal plants, most of which are in Bavaria. Among geothermal technologies, deep geothermal is the heavy hitter. Its plants access currents that run very hot and far beneath the earth’s surface: the subterranean waters can reach more than 200 degrees Celsius in wells bored as deep as five kilometres. Yet in Germany, deep geothermal accounts for just a tiny fraction of the country’s heating and cooling: 0.1% – and even less for electricity.

Until very recently, Germany’s federal government had been much more cautious than the Bavarians or other countries, such as Turkey, the Netherlands, and Sweden (see factsheet), about promoting geothermal projects, largely because of their cost and complexity. Geothermal is mentioned only once, and parenthetically, in the country’s 2050 action plan as a source for renewable heating. Geothermal power qualifies for a feed-in-tariff, and since 2009 there have been modest subsidies for deep drilling. In 2020, for the first time, shallow geothermal received state support: namely rebates of up to 45% for drilling, ground source heat pumps, and other costs, when a building is replacing oil heating with renewable energy.

Indeed, despite all of the buzz around Munich’s showy rollout, shallow geothermal energy could prove the real workhorse for Germany. Heat reserves much closer to the surface can be exploited with ground source heat pumps, which boost the temperature of shallow thermal sources’ heat. There are 420,000 geothermal heat-pump units across the country, above all in houses and larger buildings such as hospitals, which cover 1.2% of Germany’s heat consumption. German laws requiring new buildings to meet energy efficiency standards and the new state grants to invest in low-carbon heating have already, in 2020’s first quarter, fueled Germany’s investment in geothermal. The think tank Agora Energiewende recommends that Germany install 2.5 to 3 million by 2030.  

Germany's heat consumption from renewable energies in 2019

Indeed, geothermal energy is expected to boost the Energiewende mightily in decades to come, above all in the heating sector. Since 2012, geothermal’s generation of heat has almost doubled. But this is still just a sliver of its potential, according to studies such as the 2019 report of the German Environment Agency (UBA), Germany’s environmental protection agency, which calculates scenarios for Germany’s heating sector that show shallow and deep geothermal covering about half of the country’s heat supply by 2050.  In 2019, four associations involved in the heating sector called for a state master plan to ramp up Germany’s use of deep geothermal sources much more quickly.

“Geothermal has a very promising future in Germany’s heating sector,” explains Ernst Huenges, head of geoenergy at the German Research Center for Geosciences (GFZ), “because there isn’t really anything else that can provide the amount of heat that Germany needs to become climate neutral.”

The various kinds of bioenergy, Huenges says, which currently account for most of Germany’s low-carbon heat, cannot be expanded much beyond their current volume. Solar thermal energy, he says, another source of heat, is not competitive in cities “due to high demand for roof space, which is already required for photovoltaic panels.”

Deep geothermal plants, such as those in and around Munich, can provide heat and cooling, and in some cases power too, to tens of thousands of households or even to industrial centres. The process is relatively straightforward. From deep wells, geothermal water or steam is piped up from the earth’s depths and then fed into a heat exchanger, which transfers the water’s heat into district heating grids. The process functions as a sustainable closed loop. The used water is then piped back down through a second well, returning it to the earth. Such deep reservoirs exist in southern Germany, the Upper Rhine region, and most of northern Germany. For cooling, absorption chillers turn the heat into cold, which is the technology that the Schäftlarnstraße plant will rely upon for generating cooling.

The conditions for shallow geothermal generation are more common across most of the country, especially beyond cities – namely, where ground heat of 10 to 25 degrees Celsius can be tapped at depths above 400 meters. Shallow systems, however, require electric heat pumps to ramp up temperature in order to heat buildings. Experts say the geothermal pumps are extremely efficient: one kilowatt hour of electricity can generate 100 kilowatt hours of thermal energy. Around a fifth of all buildings in Sweden rely on geothermal heat pumps for heating and cooling.

Geothermal is all the more important today, as Germany’s heating sector constitutes about half of Germany total energy consumption, and has lagged far behind the power sector in converting to renewables. Fossil fuels still overwhelmingly dominate the heat sector, which includes cooling and industrial heating processes. The share covered by renewables is just 14% – most of which is bioenergy.

“The Energiewende has so far concentrated on electricity and has been very successful there,” says Huenges. “But heat must be addressed and I think the Wärmewende [heat transition] is finally beginning to happen. Germany can’t get around geothermal. In fact, it’s a very good fit.”

Huenges notes that the state of Baden Wurttemberg recently announced far-reaching support scheme for deep geothermal projects. The state believes that, among other towns and regions, the cities of Karlsruhe, Mannheim und Heidelberg can all be heated with deep geothermal energy.

“All of southern Germany and our biggest cities like Hamburg and Berlin are giving geothermal a hard look,” says Deinhardt. “This means drilling and drilling to determine where the geological conditions are right.” Deinhardt applauds the federal government’s new subsidies for drilling, even though, he says, what the geothermal sector really needs is fair markets that reward carbon-free energies that provide heat. The cost of drilling one well is about €10 million and every loop has two wells; they are thus the largest line item in geothermal development, which can run to €60 million for a single heat and power plant. The German investment bank’s subsidy amounts to €2.5 million per borehole. A maximum of four deep wells can be funded per project.

Geothermal’s enticing qualities

The qualities of geothermal energy, where the geological conditions are right, which includes much of Europe, are multifarious: for one, it is largely CO2 free. Also, it’s a baseload renewable, in contrast to wind and solar power, which are weather dependent. Since the earth’s internal temperatures are relatively steady, geothermal plants generate 24/7 and could thus back up energy systems based on wind and solar, as Germany’s will be. Moreover, the earth’s internal temperatures can be harnessed to generate electricity as well as heat. The process requires that steam drive a turbine-propelled generator that produces electricity. Five geothermal units in Germany generate both heat and power.

Experts say that harnessing the earth’s heat is largely safe and environmentally friendly when hydraulic fracking technology is not employed to enhance water flows in less-porous underground areas. Most hydraulic fracking in geothermal wells – the cause of earth tremors where it has been used – is banned in Germany.

“We’ve had practically no objections here in Munich,” says Solic about Stadtwerke München’s two inner-city plants. The plants, he notes, are small in size: just a large building. “And the plants themselves issue no exhaust and make no noise beyond a faint swishing sound of the ventilators that is drowned out by the city’s other noises.”    

Fears and faults

But geothermal energy is not without its drawbacks: namely fears about its safety and high costs. Tremors and earthquakes triggered by well construction, such as the 5.5 magnitude quake in Pohang, South Korea in 2017, have largely been the result of hydraulic fracking, which employs water or chemicals to fracture hot rock that inhibits the flow of thermal waters.

But even in Germany, less-invasive methods that tamper with the earth’s geology have caused damage. The miniscule tremors in 2008 in Staufen im Breisgau, in southern Baden Wurttemberg, caused by drilling are still an issue in the region. In 2013 in the city of Landau in Rhineland Palatinate, poor project analysis and high-pressure pumping of water back into the earth also caused tremors that damaged housing.

“Staufen and Landau are on the minds of people in the Upper Rhine region when we talk with them about new plants,” says Herbert Pohl, managing director of Deutsche ErdWärme, a Karlsruhe-based geothermal developer, that aims to build several plants in southwestern Germany. “But mistakes were made there that wouldn’t be made today. Our pre-drilling analyses are much more advanced and thorough,” he says.

Another threat is the contamination of drinking water. Berlin, for example, could have significant geothermal potential but since its entire drinking water reservoirs are directly beneath the city, experts fear that drilling could cause contamination. Studies commissioned by the city are currently examining the scale of this threat.

New technology and knowledge about geology and seismic activity makes geothermal today a much safer bet, says Stefan Wiemer, professor of seismology and director of the Swiss Seismological Service. “There’s no silver bullet that will prevent such accidents in the future,” says Wiemer. “But good risk management, such as seismic monitoring, will reduce the risk.”

“It’s possible to guarantee a very high degree of safety,” says Huegnes of GFZ, “but people are still scared of geothermal. They find in scary, altering the ground beneath them.”   

And then there’s the price tag, especially in the exploratory and drilling phases. The intensive geological and seismic studies, and then the drilling are the developer’s largest expenses. “This is a long and intensive process,” says Pohl of Deutsche ErdWärme. “You have to have investors behind you who you can count on for reliable funding.”

Germany’s federal ministry for the economy and energy says that its explorations into exploiting geothermal for electricity generation found the process too expensive and plagued by technical difficulties.

The price tag of one of Germany’s newest geothermal heat and power plants in Holzkirchen, south of Munich, was €40 million. The community only had enough funding for one exploratory borehole, which struck plentiful thermal flows five kilometres below the surface.

“The earth’s heat is a resource that doesn’t deplete the way that, say, an oil well does,” says Pohl. “With minimal operating costs and maintenance, a geothermal plant can produce heat and power non-stop for 30 to 40 years.”

Geothermal, Pohl says, is the baseload source required for an entire economy to transition to renewable energy. The 30 deep plants now in the pipeline are thus probably just the start of geothermal’s story in Germany.       

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