Geothermal energy experts are playing down worries about the threat of induced seismicity connected with enhanced or engineered geothermal systems (EGS) following news reports about an earthquake apparently caused by an EGS project in Germany. The project in the western German city of Landau in der Pfalz is continuing operation while a panel of experts evaluates data from the mid-August magnitude-2.7 temblor. Officials of Geox GmbH, the plant’s owner, deny the temblor was caused by their plant.
Globally, about 9,000 MW of geothermal projects are operating today. Most of them tap water heated to high temperatures deep underground by the Earth’s own heat. The water is pumped to the surface to generate steam that drives steam turbines, which generate electricity. EGS is different in that it goes three to 10 kilometers into the Earth, much deeper than other systems. Instead of tapping existing water, it fractures the deep rock with water pumped in at high pressure and extracts the hot water or steam via a separate well to generate electricity on the surface.