- Geothermal Power refers to power from the heat (thermal) of the earth (Geo). The inside of the earth consists of the outer crust, the mantle and the inner core. The topmost layer of the mantle just below the earth crust contains molten rocks called magma. Magma is a high temperature (estimated to be in the order of 1000 - 1400 oC) and highly viscous fluid. Volcano results when magma breaks through the earth crust as lava ("river" of magma) on the earth surface. Any surface water that trickles down the cracks in the earth crust and comes in contact with magna (or molten rocks) get heated up and have escaped to the surface as hot springs. The temperature of the earth rocks increases as it goes deeper down.

There is 3oC temperature increase for every 100 meters into the the earth and by the depth of 3,000 m or 3 Km below the ground, the rock would be hot enough to boil water.

Geothermal power harnesses this heat source benefit the earth crust to provide heat (as in heated water) and electricity to homes and industries. Geothermal power has been used in several parts of the World (and most profoundly in Iceland) to provide heating for swimming pools, domestic hot water at homes and industries and building space heating. It has also been used to provide electricity. The generation of electricity from geothermal energy source is carried out through a Geothermal Power Plant.

Geothermal power plants are similar to Coal powered plants and hydroelectric powered plants and Nuclear Plants in the way they produce electricity. The difference in the systems is their fuel sources. Essentially, the technologies produce the energy that drives the turbine and the electromagnetic rotor which creates flow of electrons (or electricity). Geothermal Power Plants obtain the fuel that drives the plants from hot fluids buried several kilometres below the earth surface.

Water from the surface (e.g. rain water) seeping through the cracks on the earth surface, over several years, fill the underground reservoir. The fluid (consisting of water and dissolved materials and solids picked up as the water seeped down) in the underground reservoir is heated up to very high temperatures when it comes into contact with the molten rock (magma) beneath the earth crust, to form the superheated fluids. The superheated fluids do not turn into steam while underground because they are not exposed to air. As the fluid get to the surface, they become steam and could be used similarly to the steam generated from coal fired plants, to power a turbine that drives an electromagnetic system that generates electricity for domestic and industrial uses.

An approach, called crystallizer-reactor clarifier technology, described below, is used to turn the superheated fluids into steam while removing solids from it. The fluid is used to drive the turbine that generates electricity.

The components of a geothermal power plant are as described below:

Production Wells: The superheated fluids are tapped by production wells drilled up to 1500 to 3000 m (1.5 to 3.0 Km) below the earth surface. Under its own pressure, the superheated fluids flow through the production wells to the surface. As the hot fluid flows to the surface, the pressure lessens causing a small amount to become steam.

Wellhead Separator: The mixture of the hot fluid and and the steam moves through a surface pipeline system to a wellhead separator where the pressure is reduced. In the wellhead separator most the remaining hot fluid vaporises to produce high pressure steam.

Standard Pressure Crystallizer: Any hot fluid not flashed as steam, up to this point, moves to a standard pressure crystallizer to produce standard pressure steam.

Low Pressure Crystallizer: Remaining hot fluid is then flashed at a lower pressure, inside a low pressure crystallizer, to create a lower pressure steam.

All steam (high, standard and low pressure) created is sent to a turbine. The force of the steam spins the turbine’s blades which turns the shaft connected to an electrical generator. Electrical charge is created and can be directed to a transformer where the voltage is increased and sent down power lines.

At the end of these processes, any fluid not converted into steam is returned to the underground reservoir where in time they will be re-heated and re-used, making the process renewable.

Learn more about geothermal energy through this video:

Some Other Resources for Geothermal Energy:

• Geothermal Energy on Wikipedia