Enhanced geothermal system

Enhanced Geothermal System. (The words on the drawing, are in German. One word has this correct version: Injektionsbohrung)

An enhanced geothermal system (EGS) is a geothermal energy system that can make electrical energy when natural underground water is not there.

For a long time, geothermal energy could only be produced where there were hot rocks, underground water, and cracks in rocks all together in one area. These areas may need underground water or a network of fractures in their rocks or both.

Heat can now be got outside normal geothermal areas like active plate boundaries. It can be got in less active areas like the western United States.

The heat is got by artificially pushing water down into hotter rocks. This can create new fractures through the rock in addition to expanding the existing fractures. That is why the new technique is called "fracking".