GEOTHERMAL ENERGY

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GEOTHERMAL ENERGY GEOTHERMAL POWER PLANT
PRSENTED BY - ABHILASH V. BHURE Y.C.C.E. NAGPUR
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What is Geothermal Energy?

• Geothermal" comes from the Greek words geo
  (earth) and thermal (heat). So, geothermal means
  earth heat.
• The thermal energy contained in the interior of
  the earth is called geothermal energy.
• Geothermal heat originates from earth's fiery
  consolidation of dust and gas over four billion
  years ago.
• The geothermal energy is enormous and will last
  for several millions of years and is therefore
  called renewable

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Question arises how does it comes to the earth
surface?

• The heat from the earth's core continuously flows
  outward. It transfers (conducts) to the
  surrounding layer of rock, the mantle.
• When temperatures and pressures become high
  enough, some mantle rock melts, becoming magma.
• Then, because it is lighter (less dense) than the
  surrounding rock, the magma rises (convects),
  moving slowly up toward the earth's crust,
  carrying the heat from below. c

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Pictorial view showing how exactly it takes
happens?
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• HOW EXACTLY IT IS BEING REPLENISHED???

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GEOTHERMAL RESOURCES

• The Earth's temperature increases with depth,
  with the temperature at the center reaching more
  than 4200 C (7600 F).
• A portion of this heat is a relic of the
  planet's formation about 4.5 billion years ago,
  and a portion is generated by the continuing
  decay of radioactive isotopes.
• Heat naturally moves from hotter to cooler
  regions, so Earth's heat flows from its interior
  toward the surface.

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• Because the geologic processes known as plate
  tectonics, the Earth's crust has been broken into
  12 huge plates that move apart or push together
  at a rate of millimeters per year.
• Where two plates collide, one plate can thrust
  below the other, producing extraordinary
  phenomena such as ocean trenches or strong
  earthquakes.
• At great depth, just above the down going plate,
  temperatures become high enough to melt rock,
  forming magma.

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• Because magma is less dense than surrounding
  rocks, it moves up toward the earth's crust and
  carries heat from below. Sometimes magma rises to
  the surface through thin or fractured crust as
  lava.
• However, most magma remains below earth's crust
  and heats the surrounding rocks and subterranean
  water. Some of this water comes all the way up to
  the surface through faults and cracks in the
  earth as hot springs or geysers.

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• When this rising hot water and steam is trapped
  in permeable rocks under a layer of impermeable
  rocks, it is called a geothermal reservoir.
• These reservoirs are sources of geothermal energy
  that can potentially be tapped for electricity
  generation or direct use. 4 Here, the production
  well withdraws heated geothermal fluid, and the
  injection well returns cooled fluids to the
  reservoir.
• Typically, geothermal wells are drilled to depths
  ranging from 200 to 1,500 meters depth for low-
  and medium-temperature systems, and from 700 to
  3,000 meters depth for high-temperature systems.

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Types of Geothermal Power Plants

• There are three types of geothermal steam
  plants depending on the way the energy is
  generated
• Dry Steam Power Plant
• Flash Steam Power Plant
• Binary Steam Power Plant

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Dry Steam Power Plant

• Steam is produced directly from the geothermal
  reservoir to run the turbines that power the
  generator, and no separation is necessary because
  wells only produce steam.
• This is the oldest type of geothermal power
  plant. It was first used at Lardarello in Italy
  in 1904.

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Flash Power Plant

• Geothermally heated water under pressure is
  separated in a surface vessel (called a steam
  separator) into steam and hot water (called
  brine in the accompanying image).
• The steam is delivered to the turbine, and the
  turbine powers a generator. The liquid is
  injected back into the reservoir.

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Binary Power Plant

• The geothermal water heats another liquid, such
  as isobutane or other organic fluids such as
  pentafluoropropane, which boils at a lower
  temperature than water.
• The two liquids are kept completely separate
  through the use of a heat exchanger, which
  transfers the heat energy from the geothermal
  water to the working fluid.
• The secondary fluid expands into gaseous vapor.
  The force of the expanding vapor, like steam,
  turns the turbines that power the generators. All
  of the produced geothermal water is injected back
  into the reservoir.

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Environmental Impacts

• Land
• Vegetation loss
• Soil erosion
• Landslides
• Air
• Slight air heating
• Local fogging
• Ground
• Reservoir cooling
• Seismicity (tremors)

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Advantages of Geothermal Energy

• Geothermal Energy is a renewable source of
  energy.
• By far, it is non-polluting and environment
  friendly.
• There is no wastage or generation of
  by-products.
• Maintenance cost of geothermal power plants is
  very less.
• Geothermal power plants don't occupy too much
  space and thus help in protecting natural
  environment.
• Unlike solar energy, it is not dependent on the
  weather conditions.

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Disadvantages of Geothermal Energy

•  Only few sites have the potential of Geothermal
  Energy.
• Most of the sites, where geothermal energy is
  produced, are far from markets or cities, where
  it needs to be consumed.
• There is always a danger of eruption of volcano.
•  Installation cost of steam power plant is very
  high.
•  There is no guarantee that the amount of energy
  which is produced will justify the capital
  expenditure and operations costs.
• It may release some harmful, poisonous gases that
  can escape through the holes drilled during
  construction.
•  

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Geothermal Positive Attributes

• Useful minerals, such as zinc and silica, can be
  extracted from underground water.
• Geothermal energy is homegrown. This will
  create jobs, a better global trading position and
  less reliance on oil producing countries.
• US geothermal companies have signed 6 billion
  worth of contracts to build plants in foreign
  countries in the past couple of years.
• In large plants the cost is 4-8 cents per
  kilowatt hour. This cost is almost competitive
  with conventional energy sources.

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• Geothermal plants can be online 100-90 of the
  time. Coal plants can only be online 75 of the
  time and nuclear plants can only be online 65 of
  the time.
• Flash and Dry Steam Power Plants emit 1000x to
  2000x less carbon dioxide than fossil fuel
  plants, no nitrogen oxides and little SO2.
• Geothermal electric plants production in 13.380 g
  of Carbon dioxide per kWh, whereas the CO2
  emissions are 453 g/kWh for natural gas, 906g
  g/kWh for oil and 1042 g/kWh for coal.
• Binary and Hot Dry Rock plants have no gaseous
  emission at all.
• Geothermal plants do not require a lot of land,
  400m2 can produce a gigawatt of energy over 30
  years.

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Seminar
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