Geothermal energy is derived from the ubiquitous heat source present in the rock below the earth's surface. It has many uses, including heating and cooling for homes and offices. However, geothermal energy can also be used to create electricity. Reservoirs of extremely high-temperature water are present together with high permeability throughout the world in regions with certain geologic conditions. These hydrothermal resources can be exploited to create electricity based on temperature gradients and the resulting steam, which can power turbines.
Geothermal energy is an extremely effective, clean, reliable and domestic source of baseload electricity. However, hydrothermal resources are present only in very specialized conditions. Some regions, like Iceland, have extensive resources, but other areas that would benefit greatly from the advantages of geothermal energy are less fortunate.
Only a small portion of the world's vast geothermal resources have the naturally-occurring heat, water and permeability necessary for conventional hydrothermal. However, advanced geothermal technologies, such as Enhanced Geothermal Systems (EGS), can create engineered hydrothermal reservoirs in regions lacking in fluid saturation and permeability. These techniques greatly expand the potential of geothermal energy.
EGS is a technique of drilling into the ground and then injecting high pressure fluid into the well in order to enhance existing fractures in the rock and create an artificial reservoir that mimics a natural hydrothermal resource. Additional "production wells" are then drilled to intersect the fractures and pump fluid, super-heated by the heat in the rock, to the surface where it is used to power turbines and create electricity.