| Geothermal Energy |
Electricity generation
Three different types of power plants - dry steam, flash, and binary - are used to generate electricity from geothermal energy,
depending on temperature, depth, and quality of the water and steam in the area.[4] In all cases the condensed steam and
remaining geothermal fluid is injected back into the ground to pick up more heat. In some locations, the natural supply of water
producing steam from the hot underground magma deposits has been exhausted and processed waste water is injected to
replenish the supply. Most geothermal fields have more fluid recharge than heat, so re-injection can cool the resource, unless it is
carefully managed.
Flash steam
Flash steam power plants use hot water above 182°C (360°F) from geothermal reservoirs. The high pressure underground keeps
the water in the liquid state, although it is well above the boiling point of water at sea level. As the water is pumped from the
reservoir to the power plant, the drop in pressure causes the water to convert, or "flash", into steam to power the turbine. Any water
not flashed into steam is injected back into the reservoir for reuse. Flash steam plants, like dry steam plants, emit small amounts
of gases and steam.[5]
Flash steam plants are the most common type of geothermal power generation plants in operation today. An example of an area
using the flash steam operation is the CalEnergy Navy I flash geothermal power plant at the Coso geothermal field.
Binary-cycle
The water used in binary-cycle power plants is cooler than that of flash steam plants, from 107 to 182°C (225-360°F)[5]. The hot
fluid from geothermal reservoirs is passed through a heat exchanger which transfers heat to a separate pipe containing fluids with
a much lower boiling point.[4] These fluids, usually Iso-butane or Iso-pentane, are vaporized to power the turbine.[6]. The
advantage to binary-cycle power plants is their lower cost and increased efficiency. These plants also do not emit any excess gas
and, because they use fluids with a lower boiling point than water, are able to utilize lower temperature reservoirs, which are much
more common. Most geothermal power plants planned for construction are binary-cycle.[6]
Enhanced Geothermal Systems
Main article: Hot dry rock geothermal energy
Enhanced Geothermal Systems , also known as Hot-dry-rock systems, involve pumping water into hot rocks in the earth, rather
than harvesting hot water already in the earth. This type of geothermal system has many advantages over the others, as it can be
used anywhere, not just in tectonically active regions. However, it requires deeper drilling than the other forms of geothermal
energy harvesting
Three different types of power plants - dry steam, flash, and binary - are used to generate electricity from geothermal energy,
depending on temperature, depth, and quality of the water and steam in the area.[4] In all cases the condensed steam and
remaining geothermal fluid is injected back into the ground to pick up more heat. In some locations, the natural supply of water
producing steam from the hot underground magma deposits has been exhausted and processed waste water is injected to
replenish the supply. Most geothermal fields have more fluid recharge than heat, so re-injection can cool the resource, unless it is
carefully managed.
Flash steam
Flash steam power plants use hot water above 182°C (360°F) from geothermal reservoirs. The high pressure underground keeps
the water in the liquid state, although it is well above the boiling point of water at sea level. As the water is pumped from the
reservoir to the power plant, the drop in pressure causes the water to convert, or "flash", into steam to power the turbine. Any water
not flashed into steam is injected back into the reservoir for reuse. Flash steam plants, like dry steam plants, emit small amounts
of gases and steam.[5]
Flash steam plants are the most common type of geothermal power generation plants in operation today. An example of an area
using the flash steam operation is the CalEnergy Navy I flash geothermal power plant at the Coso geothermal field.
Binary-cycle
The water used in binary-cycle power plants is cooler than that of flash steam plants, from 107 to 182°C (225-360°F)[5]. The hot
fluid from geothermal reservoirs is passed through a heat exchanger which transfers heat to a separate pipe containing fluids with
a much lower boiling point.[4] These fluids, usually Iso-butane or Iso-pentane, are vaporized to power the turbine.[6]. The
advantage to binary-cycle power plants is their lower cost and increased efficiency. These plants also do not emit any excess gas
and, because they use fluids with a lower boiling point than water, are able to utilize lower temperature reservoirs, which are much
more common. Most geothermal power plants planned for construction are binary-cycle.[6]
Enhanced Geothermal Systems
Main article: Hot dry rock geothermal energy
Enhanced Geothermal Systems , also known as Hot-dry-rock systems, involve pumping water into hot rocks in the earth, rather
than harvesting hot water already in the earth. This type of geothermal system has many advantages over the others, as it can be
used anywhere, not just in tectonically active regions. However, it requires deeper drilling than the other forms of geothermal
energy harvesting
Advantages
Geothermal energy offers a number of advantages over traditional fossil fuel based sources. From an environmental standpoint,
the energy harnessed is clean and safe for the surrounding environment.[8] It is also sustainable because the hot water used in the
geothermal process can be re-injected into the ground to produce more steam. In addition, geothermal power plants are unaffected
by changing weather conditions.[9] Geothermal power works continually, day and night, providing baseload power. From an
economic view, geothermal energy is extremely price competitive in some areas and reduces reliance on fossil fuels and their
inherent price unpredictability.[10] Given enough excess capacity, geothermal energy can also be sold to outside sources such as
neighboring countries or private businesses that require energy. It also offers a degree of scalability: a large geothermal plant can
power entire cities while smaller power plants can supply more remote sites such as rural villages
Geothermal energy offers a number of advantages over traditional fossil fuel based sources. From an environmental standpoint,
the energy harnessed is clean and safe for the surrounding environment.[8] It is also sustainable because the hot water used in the
geothermal process can be re-injected into the ground to produce more steam. In addition, geothermal power plants are unaffected
by changing weather conditions.[9] Geothermal power works continually, day and night, providing baseload power. From an
economic view, geothermal energy is extremely price competitive in some areas and reduces reliance on fossil fuels and their
inherent price unpredictability.[10] Given enough excess capacity, geothermal energy can also be sold to outside sources such as
neighboring countries or private businesses that require energy. It also offers a degree of scalability: a large geothermal plant can
power entire cities while smaller power plants can supply more remote sites such as rural villages
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