Geothermal Power Plant
Geothermal power plant
uses its geothermal activity to generate power. This type of natural
energy production is extremely environmentally friendly and used in
many geothermal hot spots around the globe.To harness the energy, deep
holes are drilled into the earth until a significant geothermal hot spot
is found.When the heat source has been discovered, a pipe is attached
deep dopower station,wn inside the hole which allows hot steam from deep
within the earths crust to rise up to the surface.Geothermal power is
considered to be sustainable because the heat extraction is small
compared with the Earth’s heat content. The emission intensity of
existing geothermal electric plants is on average 122 kg of CO2
per megawatt-hour (MW·h) of electricity, about one-eighth of a
conventional coal-fired plant.In the 20th century, demand for
electricity led to the consideration of geothermal power as a generating
source. Prince Piero Ginori Conti tested the first geothermal power
generator on 4 July 1904 in LARDERELLO, Italy. It successfully lit four
light bulbs.
GEOTHERMAL RESOURCES
Below the Earth’s crust, there is a
layer of hot and molten rock called magma. Heat is continually produced
there, mostly from the decay of naturally radioactive materials such as
uranium and potassium. The amount of heat within 10,000 meters (about
33,000 feet) of Earth’s surface contains 50,000 times more energy than
all the oil and natural gas resources in the world. The areas with the
highest underground temperatures are in regions with active or
geologically young volcanoes. These “hot spots” occur at plate
boundaries or at places where the crust is thin enough to let the heat
through. The Pacific Rim, often called the Ring of Fire for its many
volcanoes, has many hot spots, including some in Alaska, California, and
Oregon. Nevada has hundreds of hot spots, covering much of the northern
part of the state.These regions are also seismically active.
Earthquakes and magma movement break up the rock covering, allowing
water to circulate. As the water rises to the surface, natural hot
springs and geysers occur, such as Old Faithful at Yellowstone National
Park. The water in these systems can be more than 200°C.
Seismically active hotspots are not the
only places where geothermal energy can be found. There is a steady
supply of milder heat—useful for direct heating purposes—at depths of
anywhere from 10 to a few hundred feet below the surface virtually in
any location on Earth. Even the ground below your own backyard or local
school has enough heat to control the climate in your home or other
buildings in the community. In addition, there is a vast amount of heat
energy available from dry rock formations very deep below the surface
(4–10 km). Using a set of emerging technologies known as Enhanced
Geothermal Systems.If these resources can be tapped, they offer enormous
potential for electricity production capacity. In its first
comprehensive assessment in more than 30 years, the U.S. Geological
Survey (USGS) estimated that conventional geothermal sources on private
and accessible public lands across 13 western states have the potential
capacity to produce 8,000–73,000 MW, with a mean estimate of 33,000
MW.State and federal policies are likely to spur developers to tap some
of this potential in the next few years. The Geothermal Energy
Association estimates that 132 projects now under development around the
country could provide up to 6,400 megawatts of new capacity.As EGS
technologies improve and become competitive, even more of the largely
untapped geothermal resource could be developed. The USGS study found
that hot dry rock resources could provide another 345,100–727,900 MW of
capacity, with a mean estimate of 517,800 MW.
Working principle
Word “geothermal” has its roots in two
Greek words, “gheo” which means Earth and “thermal” which means heat.
This energy is mainly generated from Earth’s core since temperature of
Earth’s center is reaching temperatures above 6000 degrees Celsius which
is even hot enough to melt a rock. Lesser part of this energy is gained
from the crust, the planet’s outer layer by decay of radioactive
elements which are present in all the rocks. In nature this energy is
usually shown in the form of the volcanoes, hot water springs and
geysers, which are all areas on which heat is concentrated near the
earth’s surface. Geothermal energy from steam, hot water
and hot rocks from Earth’s crust. The success of this process depends on
how hot the water gets, and water temperature depends on how hot were
rocks to start with, and how much water is pumped down to these rocks.
The water is pumped down through an „injection well“, it passes through
the cracks in these rocks and then comes back up again through a
„recovery well“ towards the surface, and because of the great pressure
water is transformed into a steam when getting to the surface.This
created steam then needs to be separated from brine what is usually done
in central separation chamber. After this process of separation is
over, complete steam is transferred to heat exchangers which are located
inside the power plant. After steam is transferred to heat exchangers
it’s possible to transfer it even further to the steam turbines where it
can be generated into electricity, and in the same time through the
exhaust pipes unused energy is being released.In heat exchangers steam
is being cooled under the pressure in condensate and after that heat is
transferred into cold water in condensate heat exchangers. This cold
water that is gained on this way gets pumped from wells to storage tanks
from which is transferred to heat exchangers where water’s temperature
gets increased and then passes through deaerators where it boils and
where released oxygen and other gases that could cause corrosion are
removed by final water cooling.
Simply term it’s all in the process of
water heating and its transfer to steam which can be then used to drive a
turbo-generator that generates electricity or this steam passes through
heat exchangers and heats water creating necessary heat for central
heating of households and industrial facilities.
Power station types
Geothermal power stations are not
dissimilar to other steam turbine thermal power stations – heat from a
fuel source (in geothermal’s case, the earth’s core) is used to heat
water or another working fluid. The working fluid is then used to turn a
turbine of a generator, thereby producing electricity. The fluid is
then cooled and returned to the heat source.
Dry steam power plants
Dry steam plants are the simplest and oldest design. They directly use geothermal steam of 150°C or greater to turn turbines.
Flash steam power plants
Flash steam plants pull deep, high-pressure hot water into
lower-pressure tanks and use the resulting flashed steam to drive
turbines. They require fluid temperatures of at least 180°C, usually
more. This is the most common type of plant in operation today
Binary cycle power plants
Binary cycle power plants are the most
recent development, and can accept fluid temperatures as low as
57°C.[11] The moderately hot geothermal water is passed by a secondary
fluid with a much lower boiling point than water. This causes the
secondary fluid to flash vaporize, which then drives the turbines. This
is the most common type of geothermal electricity plant being
constructed today.[23] Both Organic Rankine and Kalina cycles are used.
The thermal efficiency of this type plant is typically about 10-13%.
Advantages of Geothermal Energy
-
Significant Cost Saving
: Geothermal energy generally involves low running costs since it saves
80% costs over fossil fuels and no fuel is used to generate the power.
-
Reduce Reliance on Fossil Fuels : Dependence on
fossil fuels decreases with the increase in the use of geothermal
energy. With the sky-rocketing prices of oil, many countries are pushing
companies to adopt these clean sources of energy.
-
Environmental Benefits : Being the renewable source
of energy, geothermal energy has helped in reducing global warming and
pollution. Moreover, Geothermal systems does not create any pollution as
it releases some gases from deep within the earth which are not very
harmful to the environment.
-
Direct Use : Since ancient times, people having
been using this source of energy for taking bath, heating homes,
preparing food and today this is also used for direct heating of homes
and offices.
-
Job Creation and Economic Benefits : Geothermal energy on the other hand has created many jobs for the local people.
Disadvantages of Geothermal Energy
-
Not Widespread Source of Energy
: Since, this type of energy is not widely used therefore the
unavailability of equipment, staff, infrastructure, training pose
hindrance to the installation of geothermal plants across the globe.
-
High Installation Costs : To get geothermal energy,
requires installation of power plants, to get steam from deep within
the earth and this require huge one time investment and require to hire a
certified installer and skilled staff needs to be recruited and
relocated to plant location. Moreover, electricity towers, stations need
to set up to move the power from geothermal plant to consumer.
-
Can Run Out Of Steam : Geothermal sites can run out
of steam over a period of time due to drop in temperature or if too
much water is injected to cool the rocks and this may result huge loss
for the companies which have invested heavily in these plants.
-
Suited To Particular Region : It is only suitable
for regions where temperature below the earth are quite low and can
produce steam over a long period of time. For this great research is
required which is done by the companies before setting up the plant.
-
May Release Harmful Gases
: Geothermal sites may contain some poisonous gases and they can escape
deep within the earth, through the holes drilled by the constructors.
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