The term geothermal originates from the Greek (“gé” = earth and “thermós” = warm), literally translated it means heat of the earth.
The interior of the earth is hot, as we can see at volcanoes, geysers and hot springs. An enormous energy potential lies hidden beneath our feet.
Deep geothermal energy harnesses the heat energy stored in the uppermost kilometers of the earth’s crust.

Schematic representation of temperatures in the Earth’s interior (Source: GFZ)

Inside the earth, temperatures reach around 5000 to 6000 degrees Celsius, with temperatures between 90 and 150 °C at depths of 3-5 kilometers in most regions of the earth. On average, temperatures rise by 3 °C per 100 meters depth. In specific geological situations, especially in volcanic areas, the temperature increase can be much higher. In Iceland, for example, the temperature at a depth of 1000 meters can already exceed 200 °C.

The heat in the earth’s interior is caused mainly due to the following processes:

  • Residual heat from the formation time of the earth
  • Decay of radioactive isotopes
  • Heat of crystallization during crystal formation in the liquid part of the earth’s interior

These processes cause a steady stream of thermal energy rising from the earth’s interior toward the surface. The heat is stored in the rocks and in deep-lying groundwater reservoirs and can be tapped by deep drilling.

Geothermal plant for district heating of Riem (Source: Stadtwerke München)

The provision of geothermal energy is almost emission-free. This makes the expansion of geothermal plants an important component of the energy and, in particular, the heat transition. Geothermal plants provide constant energy all year round, regardless of weather conditions, and are largely free of price fluctuations and import risks due to their local availability.

A basic procedure exists for the development of geothermal resources. For each planned plant, the site-specific conditions have to be investigated. The reservoir conditions at depth are estimated by geophysical measurements at the surface as well as by existing subsurface data. Thus, there is a certain risk that the well will not find thermal water or that the thermal water temperature will not match the planned user groups – this is commonly referred to as the discovery risk.

Drill head and drilling rig during the construction of the Freiham geothermal plant (Source: Stadtwerke München)

The drilling phase is the most expensive stage in the development of a geothermal plant (about 1-1.5 million euros per kilometer of drilling depth). Once the extraction has been started, it is important to ensure sustainable management of the geothermal resource, i.e. the thermal water. In addition, the correct selection of the above-ground plant technology is crucial for the efficiency of the energy supply.

In the past, microseismic events (weak earth movements) have occurred occasionally in the vicinity of some geothermal sites, the causes of which have not yet been conclusively clarified. All these factors result in a special complexity of the technology such that numerous research questions still remain unanswered.

The aim of the Geothermal-Alliance Bavaria is to address these questions. We are working to ensure that the regional available geothermal resource in Bavaria can be used in a long-term, efficient and socially acceptable manner, in particular, to promote the necessary transition to renewable heat supply.

Our ongoing projects

Research