Using High-Temperature Geothermal Energy to Generate Electricity
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High-temperature energy can be used to generate or a combination of and . 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.
© WIKICOMMONS - The geothermal power plant in Nesjavellir, near the Hengill volcano in Iceland.
The Principle Behind Geothermal Electricity Generation
If geothermal water is hotter than 150°C, it can be used directly in the form of steam to drive a turbine and thereby generate electricity . 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 (combined heat and power ) projects in the , 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.
Geothermal Electricity Around the World
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%).
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