Geothermal Resources

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Geothermal Resources
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The earth is a geologically active planet with distinct features such as volcanic eruptions and earthquakes. The energy required to drive these activities is the internal heat stored during earth’s formation. Because of its relatively smaller size and lower internal heat, the moon is devoid of these activities.
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4 Kious, W. J., and Tilling, R. I., “The Dynamic Earth: The Story of Plate Tectonics,” US Geological Survey, 2001. The electronic version of this book can be downloaded from http://pubs.usgs.gov/publications/text/dynamic.html.
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Ring of Fire
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FYI ...
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The horseshoe region encircling the Pacific Ocean covering western coasts of southern, central, and northern Americas, the Alaskan southern coast, Japan, Philippine, Indonesia, and New Zealand houses many hundreds of active and dormant volcanos and thus is called the “Ring of Fire.” This region is also the area most frequented by earthquakes and volcanic eruptions and is suitable for exploiting geothermal energy.
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Volcanoes are formed when convection currents originating deep inside the earth cause lateral forces that push one oceanic plate beneath the other, causing it to melt in a process called subduction. Some of the molten rock or magma rise find their way toward the surface and flow as lava.
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The “Ring of Fire.” The solid lines are locations of deep-sea trenches
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formed when oceanic plates collided (Image Courtesy of USGS).
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208
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Geothermal resources are of four types: hydrothermal, pressurized, hot dry rock, and magma. Hydrothermal resources are the most common source of geothermal energy and are referred to as underground reservoirs containing hot water or steam. Pressurized resources are high-temperature, high-pressure brines trapped in porous rocks. Hot dry rocks (HDR) refer to solid slabs of rock that can be up to several kilometers thick. Finally, magma is the molten rock in volcanic formations rising up from deep within the mantle. Almost all geothermal sources currently being utilized are hydrothermal.
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Depending on how the geothermal eruption appears, a hydrothermal source can be classified as a hot spring, a warm spring, a fumarole, or a geyser. Hot springs refer to upwelling of ground water with temperatures above that of the human body. It is called a warm spring when the temperature is lower body temperature but higher than the surrounding atmosphere. When a reservoir does not contain adequate water to seep through and is eventually converted to steam, the geothermal resource is referred to as a fumarole. Geysers are intermittent hot springs that, depending on geological conditions, erupt in regular intervals ranging from a few minutes to hours or months apart (See box “The Old Faithful”). Sixty percent of all geysers in the world are in Yellowstone National Park in Wyoming; others are scattered elsewhere, mainly in California, Italy, New Zealand, and Iceland.
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Geothermal resources typically lie from between a few hundred to a few thousand meters below the earth’s surface. Deeper reservoirs are generally higher in temperature and therefore yield higher efficiencies. The cost of the power plant itself is less, but drilling costs increase exponentially with depth, increasing the overall cost of extracting energy from deeper mines. With current technologies, only reservoirs within roughly four kilometers are considered to be economically viable sources of geothermal energy.
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Question: Can geothermal energy be considered a renewable source of energy? Old Faithful
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Digging Deeper ...
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A geyser is like a periodically erupting pressure cooker. The one known as “Old Faithful” has been a popular attraction in Wyoming’s Yellowstone National Park for many years. Geysers work the same way a coffee percolator works; a long narrow column of water is heated from below. In the case of geysers, the source of this heat is volcanic activity and magma. Because of its weight, water reaches temperatures well above its boiling temperature under atmospheric conditions. As the lower layer of water turns into steam, it expands, pushing out the upper layer lifting the column of water above it. As the eruption continues, the weight of the column of water, and with it the pressure at the bottom, decreases and water turns liquid again. After the water begins to reenter the channel, the whole process repeats in 50-70 minutes.
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209
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Chapter 9 - Geothermal Energy
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Answer: The earth, like the sun, has an immense amount of stored energy which will by all accounts last billions of years into the future. Unlike solar energy, which is readily available, we must tap geothermal resources. With the current technology, only hydrothermal resources are economically suitable and these have a limited lifetime before they are exhausted. (For example, the power-generating capacity of Geysers has dropped by 40% since only a decade ago). These resources can be recharged in the future as they are gradually reheated by the internal heat of the earth and, depending on their locations, can take several decades to hundreds of years to become operational again. It has therefore been suggested that geothermal energy be considered as a sustainable resource, one whose usefulness can be prolonged or sustained by optimum production strategies and methods.5 In the case of the Geysers, wastewater from a nearby community has increased the efficiency; it is estimated that at the rate of 1000 megawatts, geysers will remain sustainable for a few decades.
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==References==
==References==

Revision as of 00:21, 29 June 2010

Geothermal Resources The earth is a geologically active planet with distinct features such as volcanic eruptions and earthquakes. The energy required to drive these activities is the internal heat stored during earth’s formation. Because of its relatively smaller size and lower internal heat, the moon is devoid of these activities. 4 Kious, W. J., and Tilling, R. I., “The Dynamic Earth: The Story of Plate Tectonics,” US Geological Survey, 2001. The electronic version of this book can be downloaded from http://pubs.usgs.gov/publications/text/dynamic.html. Ring of Fire FYI ... The horseshoe region encircling the Pacific Ocean covering western coasts of southern, central, and northern Americas, the Alaskan southern coast, Japan, Philippine, Indonesia, and New Zealand houses many hundreds of active and dormant volcanos and thus is called the “Ring of Fire.” This region is also the area most frequented by earthquakes and volcanic eruptions and is suitable for exploiting geothermal energy. Volcanoes are formed when convection currents originating deep inside the earth cause lateral forces that push one oceanic plate beneath the other, causing it to melt in a process called subduction. Some of the molten rock or magma rise find their way toward the surface and flow as lava. The “Ring of Fire.” The solid lines are locations of deep-sea trenches formed when oceanic plates collided (Image Courtesy of USGS). 208 Geothermal resources are of four types: hydrothermal, pressurized, hot dry rock, and magma. Hydrothermal resources are the most common source of geothermal energy and are referred to as underground reservoirs containing hot water or steam. Pressurized resources are high-temperature, high-pressure brines trapped in porous rocks. Hot dry rocks (HDR) refer to solid slabs of rock that can be up to several kilometers thick. Finally, magma is the molten rock in volcanic formations rising up from deep within the mantle. Almost all geothermal sources currently being utilized are hydrothermal. Depending on how the geothermal eruption appears, a hydrothermal source can be classified as a hot spring, a warm spring, a fumarole, or a geyser. Hot springs refer to upwelling of ground water with temperatures above that of the human body. It is called a warm spring when the temperature is lower body temperature but higher than the surrounding atmosphere. When a reservoir does not contain adequate water to seep through and is eventually converted to steam, the geothermal resource is referred to as a fumarole. Geysers are intermittent hot springs that, depending on geological conditions, erupt in regular intervals ranging from a few minutes to hours or months apart (See box “The Old Faithful”). Sixty percent of all geysers in the world are in Yellowstone National Park in Wyoming; others are scattered elsewhere, mainly in California, Italy, New Zealand, and Iceland. Geothermal resources typically lie from between a few hundred to a few thousand meters below the earth’s surface. Deeper reservoirs are generally higher in temperature and therefore yield higher efficiencies. The cost of the power plant itself is less, but drilling costs increase exponentially with depth, increasing the overall cost of extracting energy from deeper mines. With current technologies, only reservoirs within roughly four kilometers are considered to be economically viable sources of geothermal energy. Question: Can geothermal energy be considered a renewable source of energy? Old Faithful Digging Deeper ... A geyser is like a periodically erupting pressure cooker. The one known as “Old Faithful” has been a popular attraction in Wyoming’s Yellowstone National Park for many years. Geysers work the same way a coffee percolator works; a long narrow column of water is heated from below. In the case of geysers, the source of this heat is volcanic activity and magma. Because of its weight, water reaches temperatures well above its boiling temperature under atmospheric conditions. As the lower layer of water turns into steam, it expands, pushing out the upper layer lifting the column of water above it. As the eruption continues, the weight of the column of water, and with it the pressure at the bottom, decreases and water turns liquid again. After the water begins to reenter the channel, the whole process repeats in 50-70 minutes. 209 Chapter 9 - Geothermal Energy Answer: The earth, like the sun, has an immense amount of stored energy which will by all accounts last billions of years into the future. Unlike solar energy, which is readily available, we must tap geothermal resources. With the current technology, only hydrothermal resources are economically suitable and these have a limited lifetime before they are exhausted. (For example, the power-generating capacity of Geysers has dropped by 40% since only a decade ago). These resources can be recharged in the future as they are gradually reheated by the internal heat of the earth and, depending on their locations, can take several decades to hundreds of years to become operational again. It has therefore been suggested that geothermal energy be considered as a sustainable resource, one whose usefulness can be prolonged or sustained by optimum production strategies and methods.5 In the case of the Geysers, wastewater from a nearby community has increased the efficiency; it is estimated that at the rate of 1000 megawatts, geysers will remain sustainable for a few decades.

References

Further Reading

External Links