Feature Report: What Is Geothermal Energy?

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Using High-Temperature Geothermal Energy to Generate Electricity

High-temperature geothermal energy can be used to generate electricity or a combination of heat and power. This requires capturing hot water or steam at temperatures of at least 150°C located between 1,500 to 5,000 meters below ground. Projects are often developed in areas characterized by volcanic activity.

fr - La géothermie haute énergie : l’électricité
The geothermal power plant in Nesjavellir, near the Hengill volcano in Iceland. © WIKICOMMONS

The Principle Behind Geothermal Electricity Generation

High-temperature underground heat sources can be used to generate electricity.

If geothermalDescribes the technology used to tap subsurface heat to produce energy... water is hotter than 150°C, it can be used directly in the form of steam to drive a turbine and thereby generate electricityForm of energy resulting from the movement of charged particles (electrons) through a conductor... . When its temperature is below 150°C, various techniques must be used first to vaporize the water that flows up to the surface in liquid form and transform it into dry steam, which can then be injected into a turbine.

High-temperature geothermal energy has been used since 1913, when it was employed at the world’s very first geothermal power plant, in Larderello, Italy.

Facilities Around the World and in France

High-temperature geothermal springs are located primarily in areas characterized by volcanic activity, at depths of between 1,500 and 5,000 meters below the surface, depending on geological conditions. They are mainly found in Asia, the Pacific Islands, East Africa and that continent’s Great Lakes region, North America, the Andean countries of South America, Central America and the Caribbean.

France has one geothermal power plant in operation in Bouillante, Guadeloupe. With a capacity of 13.5 megawatts, it generates close to 5% of the island’s electricity. The Strasbourg metropolitan area has several ambitious cogenerationThe simultaneous production of both heat (thermal energy) and power... (combined heatIn the field of statistical thermodynamics today, heat refers to the transfer of the thermal agitation of the particles making up matter... and powerIn physics, power is the amount of energy supplied by a system per unit time. In simpler terms, power can be viewed as energy output... ) projects in the gas pipelinePipeline used to transport gas over a long distance, either on land or on the seabed. , exploiting the great potential of the hot water aquifers in the Upper Rhine Valley.

EGS Technology in Soultz-sous-Forêts, France

In recent years, a new technology called enhanced geothermal systems (EGS) has emerged. In France, experiments using EGS are being carried out in Soultz-sous-Forêts in Alsace. The process involves injecting water into fractures in hot rock – often granite – located deep underground, then pumping it back up to the surface.

An EGS plant is in operation in Landau, Germany, in the Upper Rhine Valley, and projects are underway in Australia and the United States.

Learn more about new geothermal technologies.

Geothermal Electricity Around the World

81,7 TWh : The amount of power generated using geothermal energy around the world (out of a total of 25,000 TWh).  

In total, some 20 countries around the world produce geothermal electricity, led by the United States, the Philippines and Indonesia. Worldwide, 81.7 terawatt-hours (TWh) of power were generated from geothermal resources in 2016, out of a total of 25,000 TWh (6,000 TWh from renewable sources).

Geothermal electricity plays an essential role in countries such as Kenya (close to 50% of national power generation), Iceland (30%) and the Philippines (17%).
Find out more about geothermal energy in Kenya