There are many good reasons for using geothermal power. For example, it is available around the clock, 365 days a year, has great potential in many German regions and can be used for supplying both heat and electricity. With this in mind, the German government intends to increase the contribution of geothermal energy in domestic energy production in Germany in the future. The new 6th Energy Research Programme from the German government details the key research areas for the coming years.

In 2010, the German Federal Ministry for the Environment (BMU) approved approximately 15 million euros in funding for new geothermal research projects. This corresponds to a share of around 11% of the BMU funding for newly approved practical research projects relating to renewable energy sources. Ullrich Bruchmann, who is responsible for research funding in geothermal energy at the BMU, details the priorities as follows. “In the coming years, direct geothermal heat utilisation will also become a key area for research funding. In the medium term, this is the best way of noticeably increasing the contribution of geothermal energy in Germany. However, technologies used in high-performance geothermal power plants for generating geothermal energy are also being developed further. We also intend to support scientifically ambitious and innovative geothermal projects with funding in the future.”

Specific technology developments

One goal is the development of new, cost-effective and high-performance drilling processes. To date, up to 80% of the investment costs involved in erecting a geothermal power plant are spent on drilling. In addition, geothermal plants also require specially adapted pumps. These must be resistant against high temperatures and pressures, plus the corrosion that occurs when used in deep saltwater. Similarly demanding material requirements apply to the measurement technology and procedures, and also to the heat exchanger. Depending on the geological conditions, the natural productivity of a geothermal reservoir is sometimes not sufficient. An appropriate amount of hot water can only be supplied when water pumped with overpressure expands and increases the natural fracture systems, for example. The thermal water can then circulate better and draw more heat from the rock. The techniques and methods of such stimulation measures should be developed further. Special power plant processes (e.g. organic rankine cycle and Kalina cycle) are required for geothermal power plants with relatively low operating temperatures. The efficiency of these processes must be improved further.

Data access and accompanying ecological research

In order to evaluate the location of new geothermal plants, the planning team requires quick, comprehensive access to existing geoscientific data. Information on key existing regions for geothermal energy utilisation in Germany is already available online through the GeotIS database system. In the coming years, this should be supplemented with data from additional regions and from petrothermal geothermal energy. The BINE project information, entitled “On the trail of deep geothermal energy”, will introduce the GeotIS information system at the beginning of September. The energy research programme also promotes accompanying ecological research on geothermal energy. The goals are protection of ground water, new concepts for handling natural radioactivity in rocks and thermal water, plus the research of seismic activities.

Background

Deep geothermal systems use natural geothermal energy from depths below 400 metres for supplying heat and energy. Hydrothermal systems primarily use the energy from warm and hot water contained underground, whilst petrothermal systems use the energy stored in rocks. Geothermal energy is a constant source of energy, regardless of the time or season, and can thus be used locally to take on some of the base load in heating networks and electricity grids.

Germany has three regions that are particularly suitable for generating geothermal energy – the North German Basin, the Upper Rhine Rift and the South German Molasse Basin. As a result of current research projects, we can see that each region has different characteristics that affect the chances and requirements for their utilisation of geothermal heat. The North German Basin shows lower flow rates, moderate temperatures and, in parts, very high salinity. Meanwhile, the South German Molasse Basin shows some high flow rates, high temperatures and a mostly low salinity. The Upper Rhine Rift shows difficult practical conditions as a result of its heterogeneous geology with fault zones and the high probability of seismic activity, plus a tendency towards highly corrosive thermal water compositions. Despite this, its high temperatures and high flow rates exhibit good conditions for economic geothermal use.

17 geothermal plants were in operation in Germany by the end of 2010, with a generated output of 165 MW. Five of these (Neustadt-Glewe, Landau, Unterhaching, Bruchsal and Simbach) are operated as geothermal power plants and supply the public grid with power.