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鈥淲e鈥檙e simply very lucky that Munich and regions to its south in the Alps鈥� foothills are located atop huge reservoirs of thermal water at depths that we can access safely,鈥� says Michael Solic of the city鈥檚 municipal utility Stadtwerke M眉nchen, who notes that natural gas explorations done decades ago told the city about its geothermal trove. The city expects eventually to provide about connected to district heating systems with space heat and hot water. In light of ever-hotter summers, the city is also expanding networks.

Munich鈥檚 geothermal fleet counts among Germany鈥檚 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鈥檚 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 of the country鈥檚 heating and cooling: 0.1% 鈥� and even less for electricity.

Until very recently, Germany鈥檚 federal government had been much more cautious than the Bavarians or other 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鈥檚 as a source for renewable heating. Geothermal power qualifies for a , and since 2009 there have been modest deep drilling. In 2020, for the first time, shallow geothermal received state support: namely rebates of 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鈥檚 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鈥� heat. There are 420,000 geothermal heat-pump units across the country, above all in houses and larger buildings such as hospitals, which cover of Germany鈥檚 heat consumption. German laws requiring new buildings to meet energy efficiency standards and the new to invest in low-carbon heating have already, in 2020鈥檚 first quarter, fueled Germany鈥檚 investment in geothermal. The think tank Agora Energiewende recommends that Germany install 2.5 to 3 million by 2030. 聽

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

鈥淕eothermal has a very promising future in Germany鈥檚 heating sector,鈥� explains Ernst Huenges, head of geoenergy at the German Research Center for Geosciences (GFZ), 鈥渂ecause there isn鈥檛 really anything else that can provide the amount of heat that Germany needs to become climate neutral.鈥�

The various kinds of bioenergy, Huenges says, which currently account for most of Germany鈥檚 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 鈥渄ue to high demand for roof space, which is already required for photovoltaic panels.鈥�

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鈥檚 depths and then fed into a heat exchanger, which transfers the water鈥檚 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, turn the heat into cold, which is the technology that the Sch盲ftlarnstra脽e plant will rely upon for generating cooling.

The conditions for shallow geothermal generation are more common across most of the country, especially beyond cities 鈥� 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. the geothermal pumps are extremely efficient: one kilowatt hour of electricity can generate 100 kilowatt hours of thermal energy. Around a in Sweden rely on geothermal heat pumps for heating and cooling.

Geothermal is all the more important today, as Germany鈥檚 heating sector constitutes 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 鈥� most of which is bioenergy.

鈥淭he Energiewende has so far concentrated on electricity and has been very successful there,鈥� says Huenges. 鈥淏ut heat must be addressed and I think the W盲rmewende [heat transition] is finally beginning to happen. Germany can鈥檛 get around geothermal. In fact, it鈥檚 a very good fit.鈥�

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

鈥淎ll of southern Germany and our biggest cities like Hamburg and Berlin are giving geothermal a hard look,鈥� says Deinhardt. 鈥淭his means drilling and drilling to determine where the geological conditions are right.鈥� Deinhardt applauds the federal government鈥檚 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 鈧�10 million and every loop has two wells; they are thus the largest line item in geothermal development, which can run to 鈧�60 million for a single heat and power plant. The German investment bank鈥檚 amounts to 鈧�2.5 million per borehole. A maximum of four deep wells can be funded per project.

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 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鈥檚 geology have caused damage. The miniscule tremors in 2008 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.

鈥淪taufen and Landau are on the minds of people in the Upper Rhine region when we talk with them about new plants,鈥� says Herbert Pohl, managing director of Deutsche ErdW盲rme, a Karlsruhe-based geothermal developer, that aims to build several plants in southwestern Germany. 鈥淏ut mistakes were made there that wouldn鈥檛 be made today. Our pre-drilling analyses are much more advanced and thorough,鈥� 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. 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. 鈥淭here鈥檚 no silver bullet that will prevent such accidents in the future,鈥� says Wiemer. 鈥淏ut good risk management, such as seismic monitoring, will reduce the risk.鈥�

鈥淚t鈥檚 possible to guarantee a very high degree of safety,鈥� says Huegnes of GFZ, 鈥渂ut people are still scared of geothermal. They find in scary, altering the ground beneath them.鈥澛犅犅�

And then there鈥檚 the price tag, especially in the exploratory and drilling phases. The intensive geological and seismic studies, and then the drilling are the developer鈥檚 largest expenses. 鈥淭his is a long and intensive process,鈥� says Pohl of Deutsche ErdW盲rme. 鈥淵ou have to have investors behind you who you can count on for reliable funding.鈥�

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

鈥淭he earth鈥檚 heat is a resource that doesn鈥檛 deplete the way that, say, an oil well does,鈥� says Pohl. 鈥淲ith minimal operating costs and maintenance, a geothermal plant can produce heat and power non-stop for 30 to 40 years.鈥�

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鈥檚 story in Germany.聽聽 聽聽聽聽