(RHIE) Geothermal Lesson

Geothermal

What Is Geothermal Energy?

The word geothermal comes from the Greek words geo (earth) and therme (heat). So, geothermal energy is heat from within the Earth. We can recover this heat as steam or hot water and use it to heat buildings or generate electricity.

Geothermal energy is a renewable energy source because the heat is continuously produced inside the Earth. Geothermal energy is the heat from the Earth. It's clean and sustainable. 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.

Early geothermal plants used steam pumped directly from underground. Today, however, most geothermal power plants pump water down into wells, use subsurface heat to warm it, and return it to the surface to form steam, which drives electric turbines to generate electricity. Geothermal power has been an established technology since the early 20th century and is economically viable in geologically suitable sites, such as in the Geysers field in northern California or in Iceland, which produces most of its energy in this way.

People around the world use geothermal energy to heat their homes and to produce electricity by digging deep wells and pumping the heated underground water or steam to the surface. We can also make use of the stable temperatures near the surface of the Earth to heat and cool buildings.

Locating Geothermal Energy

Naturally occurring large areas of hydrothermal resources are called geothermal reservoirs. Most geothermal reservoirs are deep underground with no visible clues showing above ground. But geothermal energy sometimes finds its way to the surface in the form of-

• Volcanoes and fumaroles (holes where volcanic gases are released)
• Hot springs
• Geysers

The most active geothermal resources are usually found along major plate boundaries where earthquakes and volcanoes are concentrated. Most of the geothermal activity in the world occurs in an area called the Ring of Fire. This area encircles the Pacific Ocean.

When magma comes close to the surface, it heats ground water found trapped in porous rock or water running along fractured rock surfaces and faults. These features are called hydrothermal. They have two common ingredients- water (hydro) and heat (thermal).

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