Geothermal Energy: Earth’s Natural Energy
There are several sources of energy available yet we seem to rely on one that is not renewable. The most convenient way to get a source of energy would be from the earth itself (Encyclopedia 563). This source of energy is called geothermal energy, which is energy contained in intense heat the continually flows outward from deep within the earth (Encarta I).
When the planets were formed billions of years ago, heat was trapped inside and the cores became molten. Smaller planets cooled and solidified, but earth retained most of the heat (Encyclopedia 563). The crust also generates heat due to the decay of radioactive elements within the rocks (Encarta II). When temperatures and pressures become high enough, mantle rocks melts in magma. Because it is less dense than surrounding rock, it slowly rises towards earth’s crust (Introductory para 4). If the magma reaches the surface, sometimes the molten interior will burst out of volcanoes in places where earth’s crustal plates haves spread apart (Encyclopedia 563, Encarta II). But often the magma remains underground heating nearby rocks and water. This water travels up to earth’s surface as hot springs or geysers. These collections of hot water are called geothermal reservoirs (Introductory para 5). Geothermal reservoirs and volcanoes tend to be near each other. Geysers are slightly different from hot springs because their underground reservoir is periodically blocked due to high pressure. When the pressure is released, the geysers spout out hot water (Encyclopedia 563).
People have been using Earth’s heat for centuries. At first, the most common use was for relaxation. Native Americans used the hot water for cooking as early as ten thousand years ago. Romans used the “magic water” to help treat diseases and heat buildings at Pompeii (Introductory para 6). A piping system was developed in Boise, Idaho, in as early as 1892, to pump water from hot springs to homes and business. Since then, these district heating systems have been used around the world, particularly in Iceland (Encyclopedia 563). At the beginning of the twenty-first century, about three hundred eighty geothermal power plants around the world, including California, the Philippines, Italy, Mexico, Rocky Mountain states, Iceland, Japan, New Zealand, and Indonesia, provide one and a half percent of the world’s electricity (Encarta IV; Miller).
Today people drill wells into geothermal reservoirs to obtain the hot water. Geologists do extensive research to find out what areas contain this water. Then once the hot water or steam travels up the wells to the surface, it can be used to generate electricity (Introductory para 7).
There are three types of geothermal power plants, but most are flash steam plants. In a flash steam plant, hot water is piped into the plant where hot water boils to steam. The force of the expanding steam turns a turbine generator, which produces electricity. After turning the turbine, the water and the steam is piped back down to the reservoir so it can be reused (Encarta IV.A).
For reservoirs that produce mostly steam, a dry steam plant is used. In a dry steam plant, steam is piped directly through a turbine generator (Encarta IV.B).
In a binary power plant, heat from geothermal water is transferred through heat exchangers to a second fluid, usually isobutene contained in adjacent pipes. The transferred heat converts to vapor, which powers a turbine generator. Afterwards, the fluid condenses back into a liquid and is over and over again turned back into vapor by the geothermal heat. Later the water is returned to the reservoir. The binary working fluid vaporizes at temperatures lower than is necessary to vaporize water; therefore binary power plants can generate electricity by low-temperature geothermal reservoirs. However these power plants are usually more expensive to build and operate than the other types (Encarta IV.C).
There are many great advantages to using geothermal energy to generate electricity. The power plants do not have to burn fuel to manufacture steam to turn the turbines, nor is there any smoky air. Plants take up very little space and are smaller per megawatt than for almost every other type of power plant. Installations don’t require dams, forest harvesting, or mine shafts. Plants are designed to run all the time and are resistant to interruptions due to weather or natural disasters (Introductory para 13-17).
Geothermal water can be used for spas, to heat greenhouses and produce better crops, and to speed growth of fish. Industrial uses of the heat include manufacturing paper, pasteurizing milk, drying timber, melting snow, carbonating soft drinks, and warming soil (Colorful). The water can also heat individual or groups of buildings, called district heating. Heat from geothermal water is transferred through a heat exchanger to the city. Then the water is injected back into the reservoir so it can be used once again (Encarta V).
Geothermal energy is a renewable resource because earth’s heat is continuously radiated within. Each year’s rainfall supplies new water to reservoirs. Geothermal plants have very little effect on the environment, compared to other types of power plants (Encarta VI). In fact, it gives ninety-six percent less fewer carbon dioxide emissions per unit of energy than fossil fuels. The total amount of current energy recoverable would meet the United States’ energy needs at the current consumptions for the next seven hundred years (Miller).
However there are a few disadvantages. Unlike oil, geothermal energy has to be generated directly above the site of the reservoir. So areas is which geothermal energy can be used is currently extremely limited and scarce (Encyclopedia 564). Even then, usable reservoirs must be carefully managed or else they will be depleted within a few decades. Although it does not have much effect on the environment, extractions of hot water can cause some areas of land to sink. Also there is a high cost to drill into the ground. Economics is the main barrier to the complete use of geothermal energy (Miller).
In conclusion, geothermal energy is a very convenient, clean, and powerful source of energy. If we were able to get passed the few annoying barriers, it would be smart to power the entire earth based on its own source of energy in its core.
Works Cited
“Colorful Geothermal Energy Uses Poster Available.” Geothermal Information. Aug 2005. 25 May 2005. <http://www.geothermal.org/articles/colorfulposter.pdf>
Encyclopedia of Technology and Applied Sciences. Volume 4. 2000.
“Geothermal Energy.” Microsoft Encarta Encyclopedia Standard 2004. CD-ROM. Microsoft, 2003.
“Geothermal Energy Facts: Introductory Level.” Geothermal Education Office. 23 Dec 2000. 23 May 2005. <http://geothermal.marin.org/pwrheat.html>
Miller, Jr., Tyler. Living in the Enviroment. 10th ed. Wadsworth Publishing Co., 1998.