GeoThermal

Geothermal energy is energy obtained by tapping the heat of the earth itself, both from miles deep into the Earth's crust in volcanically active locations of the globe or from shallow depths, as in geothermal heat pumps in most locations of the planet. It is expensive to build a power station but operating costs are low resulting in low energy costs for suitable sites. Ultimately, this energy derives from heat in the Earth's core.
Three types of power plants are used to generate power from geothermal energy:
Dry steam -Dry steam plants take steam out of fractures in the ground and use it to directly drive a turbine that spins a generator.
Flash-Flash plants take hot water, usually at temperatures over 200 °C, out of the ground, and allows it to boil as it rises to the surface then separates the steam phase in steam/water separators and then runs the steam through a turbine.
 Such geothermal power sources exist in certain geologically unstable parts of the world such as Chile, Iceland, New Zealand, and the United States The two most prominent areas for this in the United States are in the Yellowstone basin and in northern California. Iceland produced 170 MW geothermal power and heated 86% of all houses in the year 2000 through geothermal energy. Some 8000 MW of capacity is operational in total.