Earth`s geothermal Resources

The whole of Iceland uses geothermal energy for heating, while five geothermal power stations generate around 20 per cent of the electricity. However, what is relatively easy on volcanic Iceland is a technical challenge in Central Europe. The boreholes have to be more than 4 kilometres deep before enough heat can be developed to drive a geothermal power station. “Geothermics could contribute more to the energy supply if we could manage to solve the technical problems and reduce the development costs,” explains Dr. Ernst Huenges, Head of the Geothermics Section at the GFZ.

This is why the GFZ has established a geothermics lab in Groß Schönebeck, the only one of its kind in the world. The geological conditions here are typical for large parts of Central Europe. Water-bearing rock layers with temperatures between 100 and 200 degrees Celsius are found here at a depth of between 4,000 and 5,000 metres. The two exploration boreholes extend 4,300 and 4,400 metres respectively into the earth’s inner regions. The first borehole serves to transport hot water up to the surface in order to drive the turbines of the planned experimental power station, while cooled water is then pumped down into the subterranean surfaces again through the second borehole. Several sets of experiments previously created some artificial fissures in the rock through which the deep water can flow and absorb the heat. “This stimulation method enables us to raise the productivity of the geothermal deposits,” explains Huenges. Geoscientists from several European partner countries are now developing new methods in the I-GET (Integrated Geophysical Exploration Technologies) project to precision locate suitable geothermics sites – without first having to drill any expensive test boreholes. They study the depth structure of the earth’s crust with seismic and magnetotelluric measurements. This enables them, for example, to determine the distribution of electrical conductivity in the subterranean bedrock, which serves as an indicator for deep-lying, water-bearing layers. “This work is clearly moving the technology forward so we will also be able to make broader use of it in Europe in the future,” says Huenges.