range from the constant 50 to 60 degree Fahrenheit temperatures found in the upper ten feet of earth’s crust to very hot rock and water up to several miles below the surface. Hot rock and water resources are available predominantly in the western United States, Alaska, and Hawaii, but the constant temperatures in shallow ground can be tapped almost anywhere. Like the energy of the sun, the energy within the earth is immense and has a lifetime measured in billions of years. However, unlike the sun, geothermal resources can be depleted by drawing energy out of them at a faster rate than they are replenished, resulting in a decrease in the local amount of available energy. If depleted, geothermal resources can take tens or hundreds of years to recover, so it is important to take measures that prolong the useful life of the resource.1 Geothermal fields produce only about one-sixth of the carbon dioxide that a natural-gas-fueled power plant produces, and very little, if any, nitrous oxide or sulfur-bearing gas. Geothermal Energy has been around for as long as the Earth has existed. "Geo" means earth, and "thermal" means heat. So, geothermal means earth-heat. Have you ever cut a boiled egg in half? The egg is similar to how the earth looks like inside. The yellow yolk of the egg is like the core of the earth. The white part is the mantle of the earth. And the thin shell of the egg, that would have surrounded the boiled egg if you didn't peel it off, is like the earth's crust. Below the crust of the earth, the top layer of the mantle is a hot liquid rock called magma. The crust of the earth floats on this liquid magma mantle. When magma breaks through the surface of the earth in a volcano, it is called lava. For every 100 meters you go below ground, the temperature of the rock increases about 3 degrees Celsius. Or for every 328 feet below ground, the temperature increases 5.4 degrees Fahrenheit. So, if you went about 10,000 feet below ground, the temperature of the rock would be hot enough to boil water. Deep under the surface, water sometimes makes its way close to the hot rock and turns into boiling hot water or into steam. The hot water can reach temperatures of more than 300 degrees Fahrenheit (148 degrees Celsius). This is hotter than boiling water (212 degrees F ). About 10,000 years ago, Paleo-Indians used hot springs in North American for cooking. Areas around hot springs were neutral zones. Warriors of fighting tribes would bathe together in peace. Every major hot spring in the United States can be associated with Native American tribes. California hot springs, like at the Geysers in the Napa area, were important and sacred areas to tribes from that area. In other places around the world, people used hot springs for rest and relaxation. The ancient Romans built elaborate buildings to enjoy hot baths, and the Japanese have enjoyed natural hot springs for centuries. Geothermal Today Today, people use the geothermally heated hot water in swimming pools and in health spas. Or, the hot water from below the ground can warm buildings for growing plants, like in the green house on the right. In San Bernardino, in Southern California, hot water from below ground is used to heat buildings during the winter. The hot water runs through miles of insulated pipes to dozens of public buildings. The City Hall, animal shelters, retirement homes, state agencies, a hotel and convention center are some of the buildings which are heated this way. In the Country of Iceland, many of the buildings and even swimming pools in the capital of Reykjavik (RECK-yah-vick) and elsewhere are heated with geothermal hot water. The country has at least 25 active volcanoes and many hot springs and geysers. Geothermal Electricity Hot water or steam from below ground can also be used to make electricity in a geothermal power plant. In California, there are 14 areas where we use geothermal energy to make electricity. The red areas on the map show where there are known geothermal areas. Some are not used yet because the resource is too small, too isolated or the water temperatures are not hot enough to make electricity. The main spots are: • The Geysers area north of San Francisco • In the northwest corner of the state near Lassen Volcanic National Park • In the Mammoth Lakes area - the site of a huge ancient volcano • In the Coso Hot Springs area in Inyo County • In the Imperial Valley in Southern California. Some of the areas have so much steam and hot water that it can be used to generate electricity. Holes are drilled into the ground and pipes lowered into the hot water, like a drinking straw in a soda. The hot steam or water comes up through these pipes from below ground.
burned to heat water into steam. The steam or hot water in a geothermal power plant is heated by the earth. It goes into a special turbine. The turbine blades spin and the shaft from the turbine is connected to a generator to make electricity. The steam then gets cooled off in a cooling tower. |
| What is Geothermal Energy |
| Geothermal Energy. |
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