WHAT IS GEOTHERMAL ENERGY?

Geothermal energy is a renewable and clean source of energy with a huge potential to meet the world's energy requirements. Geothermal power capacity is estimated to be 50,000 times the energy of all known petroleum reserves. Geothermal energy is produced commercially from naturally occurring steam and hot water trapped in reservoirs of permeable and porous rocks, typically 500 to 2,000 metres below the earth's surface. The energy from this heat can be used directly, with geothermal heat pumps to heat homes (Earth Energy), or indirectly to generate electricity.

Steam, extracted by drilling wells, is used to power turbines and generate electricity. The temperature of the steam has to be high enough (85°C) to provide sufficient energy to drive the turbines. A hotter steam source correlates with a higher quality (and more valuable) geothermal resource. After passing through the turbine the steam is cooled and re-injected into the reservoir. This maintains a supply of water in the reservoir and mitigates resource depletion. Typically areas with geothermal energy resources are most prevalent along the margins of tectonic activity. The map below illustrates the regions with the highest potential for geothermal development.

Background on Geothermal Energy

• First developed in 1890, Geothermal power is currently produced in more than 23 countries around the world, including the United States and Japan, where geological conditions are most ideal for the economic exploitation of this renewable and environmentally sustainable energy source;
• Installed generating capacity is currently in excess of nine thousand megawatts (MW) worldwide with approximately 44 percent of this capacity located in the Americas and 30 percent located in the United States;
• Improvements in development technologies have increased plant availability and utilization now commonly exceeds 98 percent on an annual basis;
• The geological conditions required for the development of geothermal power are most frequently found in areas of strong tectonic activity, where the interaction of the earth's plates creates the friction required to produce geothermal heat;
• This geothermal heat interacts with water contained in naturally occurring aquifers to form bodies of hot water with temperatures as high as 350C;
• Drilling into these aquifers allows the heated water and steam to be brought to the surface where it is used to drive conventional turbines that generate electricity. The water is then reinjected back into the ground to preserve the power generating lifespan of the aquifer.