# Geothermal Energy

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If you kept digging, what would you find? You'd probably find lots of worms, roots, and a few dog bones. But if you went really far down, you'd get geothermal energy.

### Geothermal Energy - What Is Geothermal Energy?

If you take the word geothermal apart, you get "geo" which means earth and "thermal" which means heat, so geothermal means heat from the Earth. Geothermal energy taps into the Earth's internal heat to create electricity and to heat and cool buildings.

### Geothermal Energy - A Look into the Earth

To get an idea of what Earth looks like, boil an egg and then cut it in half without peeling the shell. The yellow yoke is like the core of the Earth, the white part is the mantle of the Earth and the thin shell around the egg is the Earth's crust. The Earth's mantle consists of hot, liquid rock called magma (that's the stuff that shoots out of an erupting volcano) and the crust floats on this liquid.

If you're wondering what that has to do with geothermal energy, check this out: when water makes its way down close to the hot rock hundreds of feet below the surface, it turns to hot water or steam. The hot water can reach over 300 degrees Fahrenheit or 148 degrees Celsius - that's hotter than boiling water! This hot water from deep in the ground can be used to warm buildings, swimming pools and make electricity.

### Geothermal Energy - Getting Steamy

Geothermal power plants use the steam from hot water to produce electricity. The steam rotates a turbine that activates a generator, which produces electricity. There are three types of geothermal power plants:

• Dry Steam - The steam goes directly from underground wells to a power plant. The largest dry steam resource in the world is The Geysers, which is in California.
• Flash Steam - These are the most common. They use reservoirs of water that are hotter than 360 degrees Fahrenheit (182 degrees Celsius). The hot water flows up wells in the ground under its own pressure and some of it turns to steam. This steam is separated from the water and used to turn a turbine.
• Binary Cycle - These plants use water that is about 225 to 360 degrees Fahrenheit (107 to 182 degrees Celsius). The heat from the hot water is used to boil a working fluid (usually an organic compound that boils easily), which vaporizes in a heat exchanger (a device for transferring thermal energy from one fluid to another) and is then used to turn a turbine.

### Geothermal Energy - Did U Know?

• The US produces the most geothermal energy in the world.
• In the US, geothermal electricity is generated in California, Nevada, Utah, Alaska and Hawaii.
• Unlike wind and solar energy, geothermal resources are available 24/7.
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