Geothermal energy is heat which comes from the earth. It can be found anywhere. It may be tapped from deep wells. We may find it in our own yards. It can involve large power stations or small pumps. It is inexpensive to obtain, is renewable and cleaner. It also lessens dependence on fossil fuels, like coal or oil.
In 2013, sixty-eight billion kilowatts of electricity were produced by geothermal energy. It was enough to take care of six million households in the United States. The United States is a leader in producing geothermal energy. Eighty percent is produced in California where there are forty geothermal plants. They provide seven percent of the state's electricity. Geothermal heat pumps heat and cool buildings by using the heat from underground.
Radioactive materials like uranium and potassium decay in a layer just under the earth's crust. They produce heat. This layer is called the magma. It is made of hot and molten rock. Hot spots or the places on the earth where the underground temperatures are the highest occur where the earth's crust is thin. They also are found near active volcanoes. They can occur at the edges of tectonic plates under the earth. Land lining both sides of the Pacific Ocean is called the Pacific Rim. Many hotspots are located there. In the United States, California, Alaska, Nevada, and Oregon have hot spots.
In these areas, seismic movement occurs. That means that there are earthquakes and plate movement. Hot water rises up through the cracks and creates hot springs and geysers. Old Faithful in Yellowstone National Park is a geyser. Water temperatures can reach 200 degrees Fahrenheit. Milder heat is found just below the surface of the earth, between ten and one hundred feet down. Dry rock formation very deep in the earth can also provide heat.
Enhanced Geothermal Systems is the term for the new technology used in the production of geothermal energy. If these geothermal plants would be used continually, their capacity would equal those of coal and nuclear power. Today, the way that geothermal energy is captured is by taking the hot steam which rises up to the surface from under the earth's crust. The steam drives generators. Geothermal plants drill holes into the earth also to tap into the steam.
The geothermal power plants take steam and hot water from the ground and use it. Then they return it to the ground as warm water. Thus, it can be reused. There are three types of geothermal power plants. In the dry steam design, the steam goes into a turbine. Then the steam is condensed into water. The second type of plant depressurizes the hot water which is turned into steam quickly so that it can turn a turbine. This is called a flash steam plant. In a binary cycle plant, the hot water from the earth heats a second liquid which has a lower boiling point. This is changed to steam more quickly.
The largest geothermal system known is called the Geysers which is north of San Francisco, California. It is steam driven. The first well was drilled in 1924. Today, the facilities produce sixty percent of the electricity for the region north of San Francisco to the Oregon border. Their process loses too much steam, however, so a project began to transport eleven million gallons of wastewater through forty miles of pipes to the plant. When it arrives, the water is injected into the ground. The open type of plant does emit some pollutants. Hydrogen sulfide, arsenic, and some minerals are released in the steam. Salt can build up in the pipes too and has to be removed. For these reasons, the binary system which returns everything to the ground and is a closed loop with no emissions seems to be more efficient.
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