Brief description of Geothermal power plant

1. Geothermal Energy
Arpan Deyasi
Dept of ECE, RCCIIT, Kolkata, India
Course: EI605D
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2. What is Geothermal Energy?
Heat energy of earth, generated by
various natural processes
Decay of radioactive nuclei embedded within the Earth
Residual heat left over during Earth formation
Meteorite impact
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3. Geothermal Reservoirs
Geyser
Volcano
Boiling mud pot
Hot springs
This energy can be extracted by
Geothermal power plant
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4. How geothermal energy is obtained?
Cool water sends down through a well
to be heated by Earth’s warmth
Heat pump is used to take the heat from
underground water to the
substance which is to be heated
Water is cooled and injected back
to the Earth again
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5. How geothermal power plant works?
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6. Cooled water is pumped back into Earth to begin the process again
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Process flow of power plant
Hot water is pumped from deep underground
through a well under high pressure
When the water reaches the surface, the pressure is
dropped, which causes the water to turn into steam
The steam spins a turbine, which is connected
to a generator that produces electricity
Steam cools off in a cooling tower & condenses back to water

7. Different plants for Geothermal Energy production
Dry steam plant
Hot steam plant
Binary cycle plant
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8. Dry steam plant
Oldest type of plant
Reservoir containing
pure dry steam
is required
Temp of steam is
approximately 150°C
Rock catcher is required to capture the rocks coming
from underground
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9. Hot steam plant
commonly used
Containing both
hot water & steam
Pressure changing
system is required
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10. Binary cycle plant
Steam is not directly
used to spin turbines
No harmful gas is emitted
Temp of secondary
liquid (hydrocarbon)
is approximately 57°C
Steam hits secondary
liquid, which turns
into steam and the
turbine starts to rotate
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11. Major components of geothermal power plant
Production well
Separator
Stream turbine
Condenser
Steam Generator
Injection well
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12. Production well
A geothermal vent is a deep well drilled into the Earth
that the power plant uses to tap into the Earth’s heat
Depth ~ 10 km
Moist/dry steam is used
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13. Steam Generator
In a flash steam vent, superheated pressurized water is
drawn from its place underground to low-pressure tanks.
The pressure of the Earth kept the water in liquid form
despite its high temperature, and by removing that pressure
the hot water instantly turns to steam, hence the term flash
steam.
In a dry steam plant, the plant technicians pump water to
the bottom of the vent where the Earth’s heat boils the
water and turns it into steam.
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14. Turbine
Regardless of the plant type, both flash steam and dry
steam plants pump the steam from the geothermal vent to
a large turbine.
The steam passes this turbine, turning it in the process.
This turbine is attached to an electric generator, and as the
turbine turns the generator turns the mechanical energy
into electric energy, thus converting the heat from the
Earth into usable electricity.
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15. Condenser
After the steam passes through the turbine, it continues to a
condenser chamber.
This chamber condenses the steam back into liquid water by
cooling it.
The excess heat lost as the steam turns to liquid water may be
used for other applications, such as heating or greenhouse
farming.
The cooled liquid water is then typically pumped back into
the ground to either restart the boiling process for dry steam
or to replenish the natural heated aquifer for flash steam
plants.
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16. Separator
Used to remove non-condensable gases from stream
Injection well
Excess condensate and brine from separator returns
back to the underground thermal reservoir
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17. Direct Use
Hot springs used as spa
Heating water at fish farm
Raising plants at greenhouses
Providing heat at industrial sectors
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18. Advantages
Environmentally Friendly
Renewable
Huge Potential
Sustainable / Stable
Reliable
No Fuel Required
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19. Disadvantages
Location Restricted
Environmental Side Effects
Earthquakes
High Costs
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20. https://archive.epa.gov/climatechange/kids/solutions/technologies/geothermal.html
https://sciencing.com/parts-geothermal-power-plant-8621582.html
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References
Er. R K Rajput, Non-Conventional Energy Sources and Utilisation (Energy
Engineering), S. Chand Publishing
B.H Khan, Non Conventioanl Energy Resources, Tata McGraw-Hill
Education