"What is geothermal energy? Simply put, it is energy from the Earth. Geo refers to the solid part of the Earth and thermal refers to heat energy. Anywhere the Earth's surface is in close proximity to magma or volcanic activity under or near the Earth's surface, we can harness the energy. According to the Department of Energy,"Geothermal energy technologies use the heat of the earth for direct-use applications, geothermal heat pumps, and electrical power production. Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface and down even deeper to the extremely high temperatures of molten rock called magma. Three power plant technologies are being used to convert hydrothermal fluids to electricity. The type of conversion used depends on whether the fluid is steam or water and its temperature."

"eothermal energy in the United States continues to be an area of considerable activity. In 2012, the United States led the world in geothermal electricity production with 3,386 megawatts (MW) of installed capacity;[1][2] the largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California.[3] The United States generates an average of 15 billion kilowatt hours of geothermal power per year, comparable to burning some 25 million barrels (4,000,000 m3) of oil or 6 million short tons of coal per year.[4] Geothermal power plants are largely concentrated in the western states. They are the fourth largest source of renewable electricity, after hydroelectricity, biomass, and wind power. A geothermal resource assessment shows that nine western states together have the potential to provide over 20 percent of national electricity needs.[4][5]"

"Archaeological evidence shows that the first human use of geothermal resources in North America occurred more than 10,000 years ago with the settlement of Paleo-Indians at hot springs. The springs served as a source of warmth and cleansing, their minerals as a source of healing. While people still soak in shallow pools heated by the earth, engineers are developing technologies that will allow us to probe more than 10 miles below the earth's surface in search of geothermal energy. We invite you to study the timeline of the recent history of geothermal energy in the United States."

"It may surprise you to know that the ancient Romans had central heating. They used geothermal energy - in the form of hot springs - to heat their homes. Geothermal heating wasn't used in an organized fashion since until the late 19th century when Boise, Idaho, piped in water from local hot springs to warm buildings. Now, geothermal energy is used globally. Reykjavik, Iceland, leads the world in use of geothermal energy, heating 95 percent of its buildings with heat from below the Earth's surface."

" Geothermal Electricity Production Most power plants need steam to generate electricity. The steam rotates a turbine that activates a generator, which produces electricity. Many power plants still use fossil fuels to boil water for steam. Geothermal power plants, however, use steam produced from reservoirs of hot water found a couple of miles or more below the Earth's surface. There are three types of geothermal power plants: dry steam, flash steam, and binary cycle. Dry steam power plants draw from underground resources of steam. The steam is piped directly from underground wells to the power plant, where it is directed into a turbine/generator unit. There are only two known underground resources of steam in the United States: The Geysers in northern California and Yellowstone National Park in Wyoming, where there's a well-known geyser called Old Faithful. Since Yellowstone is protected from development, the only dry steam plants in the country are at The Geysers. This geothermal power plant generates electricity for the Imperial Valley in California. Credit: Warren Gretz Flash steam power plants are the most common. They use geothermal reservoirs of water with temperatures greater than 360°F (182°C). This very hot water flows up through wells in the ground under its own pressure. As it flows upward, the pressure decreases and some of the hot water boils into steam. The steam is then separated from the water and used to power a turbine/generator. Any leftover water and condensed steam are injected back into the reservoir, making this a sustainable resource. Binary cycle power plants operate on water at lower temperatures of about 225°-360°F (107°-182°C). These plants use the heat from the hot water to boil a working fluid, usually an organic compound with a low boiling point. The working fluid is vaporized in a heat exchanger and used to turn a turbine. The water is then injected back into the ground to be reheated. The water and the working fluid are

"Heat from the earth can be used as an energy source in many ways, from large and complex power stations to small and relatively simple pumping systems. This heat energy, known as geothermal energy, can be found almost anywhere-as far away as remote deep wells in Indonesia and as close as the dirt in our backyards. FROM OUR BLOG The Latest on Renewable Energy from Our Experts and Analysts Will Clean Energy Research and Development Be Sequestered? Laura Wisland PTC Extension Already Making a Big Difference for Wind Steve Clemmer The Local Energy Movement: Coming to a Town Near You Laura Wisland Subscribe to the Energy blog feed Many regions of the world are already tapping geothermal energy as an affordable and sustainable solution to reducing dependence on fossil fuels, and the global warming and public health risks that result from their use. For example, more than 8,900 megawatts (MW) of large, utility-scale geothermal capacity in 24 countries now produce enough electricity to meet the annual needs of nearly 12 million typical U.S. households (GEA 2008a). Geothermal plants produce 25 percent or more of electricity in the Philippines, Iceland, and El Salvador."