More than half of Germany's energy demand is needed to generate heat, either for heating buildings or as process heat for industry. So far, 85 percent of this heat has been generated by fossil fuels, i.e. coal, oil and gas. If Germany wants to become climate-neutral by 2045, this must change. Therefore, heating methods that do not generate CO2 emissions are in demand. An alternative is geothermal energy, the use of geothermal energy, which provides the hot interior of our planet. So far, it has only been sparsely used in Germany, but this is set to change in the future: Together with centers of the Helmholtz Association, the Fraunhofer-Gesellschaft today presented a roadmap with recommendations on how geothermal energy could be tapped on a large scale in the future.
- How deep do you have to drill in this country to use geothermal energy?
- How many of these deep geothermal plants are there in Germany so far?
- What role could geothermal energy play in the heat supply in the future?
- What are the biggest obstacles?
- How economical could deep geothermal energy be?
- What are the risks and side effects?
How deep do you have to drill in this country to use geothermal energy?
There are two variants of geothermal energy: In near-surface geothermal energy, the boreholes typically go 100 meters deep, where the water is about 12 degrees warm and can then operate a heat pump at the top. This technology is already quite widespread: There are around 440,000 such systems in Germany. The other method is deep geothermal energy: Here, the boreholes reach up to 5,000 meters deep, and there the water is up to 180 degrees hot, regardless of the season. This water can be pumped up and used for district heating networks or as process heat for industry. The study is about this deep geothermal energy, because there is considerable potential here.
How many of these deep geothermal plants are there in Germany so far?
So far, the number of deep geothermal plants in Germany has been limited – there are just 42. Together, they have an output of 360 megawatts, which is no more than a single larger coal-fired cogeneration plant today. These 42 geothermal plants are not evenly distributed across the country. This is because suitable underground hot water reservoirs are not available everywhere, but only in certain regions, especially in northern Germany, the Rhine/Ruhr, the Upper Rhine Graben and the Munich area.
What role could geothermal energy play in the heat supply in the future?
Although the hotspots are regionally limited, the potentialis surprisingly high: According to the study, geothermal energy could cover a quarter of Germany's heating demand. In order to be able to leverage this potential, however, the number of turbines would have to be increased a hundredfold – many new holes would have to be drilled. By 2030, there would be around 4,000 boreholes, and by 2040 even as many as 20,000 kilometer-deep holes. This would be necessary if the political target of 50 percent climate-neutral heating in 2030 is to be fulfilled and not just 15 percent as before.
What are the biggest obstacles?
There are still some hurdles in the way of the expansion of geothermal energy: For example, it is not yet known exactly enough where worthwhile hot water reservoirs are located. This requires further exploratory drilling in order to obtain an underground "map" that is as precise as possible, which shows: Where is drilling worthwhile, where not? Another problem: So far, there is only a relatively small geothermal industry that produces these plants. This would have to be scaled up significantly in the future, then the plants should also become cheaper. In addition, the legal regulation is still quite cumbersome, and the approval procedures take too long. All this would have to be simplified and accelerated. And: Not every borehole brings the desired success, which deters some energy suppliers. Therefore, the report proposes a kind of insurance that at least partially covers possible default risks.
How economical could deep geothermal energy be?
As far as the economic viability of geothermal energy is concerned,the experience with previous plants is quite optimistic: Here, the generation costs are 2.5-3 cents/kWh, i.e. in the order of magnitude of fossil energies. But since geothermal energy is now to be expanded so quickly, high investments are due in the next ten years alone, estimated at 50 to 60 billion euros. In order to achieve this, the federal government should promote geothermal energy with well over one billion euros per year in the future, according to the recommendation of the report.
What are the risks and side effects?
However, geothermal energy also has some risks and side effects. Care must be taken not to affect drinking water reservoirs. In addition, the drilling makes noise and could disturb residents. And: There have been cases where geothermal plants have triggered small earthquakes. But according to the study, these risks and side effects seem manageable: In the event of earthquakes, sensors can warn in good time, then the pumping of the water would be throttled, which reduces the risk of earthquakes. And the drilling rigs should at least be soundproofed so well that they do not disturb the residents too much.