In the center of our earth it is as hot as the sun, around 6000 degrees. 2,000 to 5,000 meters below the earth’s surface it is still 60 to 200 degrees and in volcanic regions on the surface up to 400 degrees Celsius.

Our ancestors had been using geothermal energy in some regions for a long time: In the first century, the Romans in Aachen and Wiesbaden heated houses and thermal baths with hot spring water, in New Zealand the Maori used geothermal heat for cooking, and in Larderello, Italy, electricity was first generated from geothermal energy in 1904.

Around 400 power plants in 30 countries generate electricity with steam from the earth – the total output is 16 gigawatts (GW). This power generation is particularly important in volcanic regions along the Pacific Ring of Fire, in the USA, Mexico, El Salvador, Iceland, Turkey, Kenya, Indonesia, the Philippines and New Zealand – the global average, however, is the share of electricity from geothermal energy at only 0, 5 percent.

Geothermal energy is more important worldwide for heating swimming pools, buildings, greenhouses and urban heating networks. Water at a temperature of up to 200 degrees is pumped out of aquifers from boreholes that are up to 5,000 meters deep, the heat is used and the cooled water is pressed back through a second borehole.

This heat generation is possible worldwide, cheap and is increasingly used in countries without volcanic activity. According to estimates by Status Report Renewables, the installed capacity of geothermal thermal power plants worldwide is currently 38 gigawatts, more than double that of geothermal power plants for electricity generation.

So far, China (14 GW), Turkey (3 GW), Iceland (2 GW) and Japan (2 GW) in particular have been pursuing the expansion of deep geothermal energy with great determination and are using it to heat more and more districts and greenhouses. In Germany, the city of Munich in particular heats cheaply with geothermal energy and wants to use this energy in the heating sector to become climate-neutral by 2035.

The new federal government is now also focusing on the expansion of deep geothermal energy for climate-neutral heat supply by 2045 and wants to promote the development of deep heat sources with numerous measures. According to studies, deep geothermal energy in Germany with an installed capacity of 70 GW could generate around 300 TWh/a of heat, more than half of the future heat requirement of all buildings.

Geothermal energy is increasingly being used from the near surface of the earth in combination with heat pumps. In boreholes from 50 to 400 meters deep, water flows from top to bottom and back again in a closed pipe system and heats up to 10 to 20 degrees. A heat pump then uses this energy to produce hot water at 30 to 70 degrees, which can be used to heat buildings.

Researchers see a heat potential similar to that of deep geothermal energy in this near-surface geothermal energy. In Germany, the entire heat demand for buildings could be covered with these two technologies alone in the future.

According to an analysis by six German research institutes, heat generation using deep geothermal energy costs less than three euro cents per kilowatt hour (kWh).

Before Russia attacked Ukraine, however, heat generation with natural gas from pipelines was cheaper for many public utilities in Europe, so investing in the construction of deep geothermal plants did not seem attractive. The situation has changed completely as a result of the war and the sharp rise in gas prices in Europe to over 12 cents per kWh. Municipal utilities are now showing great interest in deep geothermal energy for municipal heat supply.

no The potential of geothermal energy is almost unlimited and the heat demand for heating buildings can be covered worldwide with deep and near-surface geothermal energy in combination with heat pumps.

But in industry, temperatures of over 200 degrees are sometimes required, which currently cannot usually be achieved with geothermal energy and heat pumps. For such high temperatures, heating with electricity, biogas, biomass and green hydrogen are the climate-friendly alternatives.

In the last hundred years, the oil and gas industry in particular has gathered expertise about the subsoil, how to drill, there are specialist staff and mature technology. Prof. Rolf Bracke, head of the Fraunhofer Institute for Energy Infrastructure and Geothermal Energy (IEG) is confident to DW that geothermal energy can be expanded quickly “if the oil and gas industry should turn to geothermal energy”.

However, if the companies continue to concentrate on the production of oil and gas because more money can be earned with it, “then I’m pessimistic,” says Bracke, because then there would be a lack of personnel and drilling technology for the rapid expansion of geothermal energy. According to Bracke, the development of heat sources in the depths takes two to three years with quick approval, in Germany about three times as long due to bureaucratic delays. The federal government now wants to accelerate this process and increase heat generation from deep geothermal energy tenfold from the current one terawatt by 2030.

Yes. In regions with seismic activity, geothermal energy can trigger small earthquakes if water is injected into the subsoil at too high a pressure and releases existing stresses there. In some cases, the tremors led to cracks in buildings and the rejection of this technique.

According to Bracke, there are no experiences with earthquakes in regions without tension in the subsoil. In the meantime, geothermal use has also been improved: With lower water pressures underground and more sophisticated monitoring methods, earthquakes on the surface can be avoided.

However, compared to the extraction of oil, natural gas and coal, geothermal energy is much less risky, emphasizes Bracke, and is “by far the safest source of energy on earth”.

Author: Gero Rueter

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The original of this article “Golden age for geothermal energy?” comes from Deutsche Welle.