This presentation focuses on one of the renewable energy source which is obtained from the earth. Geothermal power plant have the same working principle like the other thermal plants but with a certain differences. This topic is again basic highlight about geothermal power plant. thu in order to obtain full information you should refer other books.

1. Chapter Three
GEOTHERMAL ENERGY
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2. GEOTHERMAL ENERGY
energy from the inside of the Earth
➢The term geothermal comes from the Greek geo meaning earth and therine meaning
heat thus geothermal energy is energy derived from the natural heat of the earth.
➢The heat inside the Earth core is continually generated by the decay of the long lived
radioactive isotopes of uranium, thorium and potassium, which are present in the Earth.
➢The core itself has two layers: a solid iron core and an outer core made of very hot
melted rock, called magma.
➢The mantle which surrounds the core and is about 1,800 miles thick. It is made up of
magma and rock.
➢The crust is the outermost layer of the earth, the land that forms the continents and
ocean floors. It can be three to five miles thick under the oceans and 15 to 35 miles thick
on the continents.
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3. GEOTHERMAL ENERGY
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4. GEOTHERMAL ENERGY…
➢The earth's crust is broken into pieces called plates. Magma comes close to the earth's
surface near the edges of these plates. This is where volcanoes occur. The lava that
erupts from volcanoes is partly magma.
➢The heat that flows from the Earth's hot interior due to plate movements, zones of high
heat flow, may be located close to the surface where convective circulation plays a
significant role in bringing the heat close to the surface.
➢The gradual radioactive decay of elements within the earth maintains the earth's core at
temperatures in excess of 5000°C.
➢Heat energy continuously flows from this hot core by means of conductive heat flow
and convective flows of molten mantle beneath the crust.
➢The result is that there is a mean heat flux at the earth's surface of around 16 kilowatts
of heat energy per square kilometer which is dissipated to the atmosphere and space.
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5. GEOTHERMAL ENERGY
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6. GEOTHERMAL ENERGY
➢This heat flux is not uniformly distributed over the earth's surface but tends to be
strongest along tectonic plate boundaries where volcanic activity transports high
temperature material to near the surface.
➢Only a small fraction of the molten rock feeding volcanoes actually reaches the
surface.
➢ Most is left at depths of 5-20 km beneath the surface, where it releases heat that can
drive hydrological convection that forms high temperature geothermal systems at
shallower depths of 500-3000m.
➢The heat continuously flowing from the Earth’s interior, which travels primarily by
conduction, is estimated to be equivalent to 42 million megawatts (MW) of power
expected to remain so for billions of years to come, ensuring an inexhaustible supply of
energy, Renewable energy.
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7. How does geothermal heat get up to the surface?
➢Hot magma reaches all the way to the surface, where we know it as
lava.
➢But most often the magma remains below earth's crust, heating
nearby rock and water(rainwater that has seeped deep into the earth) .
➢sometimes as hot as 700 0F(3700C).
➢Some of this hot geothermal water travels back up through faults and
cracks and reaches the earth's surface as hot springs or geysers,
➢but most of it stays deep underground, trapped in cracks and porous
rock. This natural collection of hot water is called a geothermal
reservoir.
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8. GEOTHERMAL ENERGY
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9. GEOTHERMAL ENERGY
➢If geothermal reservoirs are close enough to the surface, we can reach
them by drilling wells,
➢Scientists and engineers use geological, electrical, magnetic, geochemical
and seismic surveys to help locate the reservoirs after an exploration well
confirms a reservoir discovery, production wells are drilled.
➢ A geothermal system is made up of three main elements:
✓heat source
✓reservoir and
✓fluid, which is the carrier that transfers the heat.
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10. GEOTHERMAL ENERGY
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11. Generation of electricity
➢To develop electricity from geothermal resources, wells are drilled into a
geothermal reservoir. The wells bring the geothermal water to the surface
➢We use the natural hot water and steam from the earth to turn turbine
generators to produce electricity.
➢Geothermal power plants give off water vapour, but have no smoky
emissions.
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12. Generation of electricity
➢There are four commercial types of geothermal power
plants:
a. Flash power plants,
b. Dry steam power plants,
c. Binary power plants, and
d. Flash/binary combined power plants
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13. A. Flash Power Plant:
Geothermal 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 generates
power. The liquid is
injected back into the
reservoir and reheated.
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14. B. Dry Steam Power Plant:
A very few geothermal
reservoirs are filled
naturally with steam, not
water.
➢ This means that the wells
will produce only steam.
➢ The power plants that run
on this steam are called “dry
steam” power plants.
➢ Here, the steam blasts right
into the turbine blades (they
do not need separators),
then is condensed to water
and piped back into the
reservoir.
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15. Generation of electricity
C. Binary Power Plant: Recent advances in geothermal technology have
made possible the economic production of electricity from geothermal
resources lower than 150°C (302°F).
➢Binary plants typically use an Organic Rankine Cycle system.
➢The geothermal water (called “geothermal fluid” in the accompanying
image) heats another liquid, such as isobutene 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
➢The secondary fluid expands into gaseous vapor
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16. ➢ second liquid flashes to
vapor and drives the
turbine.
➢ Once used, the
geothermal water is
pumped back into the
reservoir
➢ Moderate-temperature
reservoirs are more
common than high
temperature reservoirs
➢ use of binary power
plants is expanding
worldwide.
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17. D. Flash/Binary Combined
Cycle:
➢ This type of plant, which
uses a combination of flash
and binary technology, has
been used effectively to take
advantage of both
technologies.
➢ In this type of plant, the
portion of the geothermal
water which flashes’ to
steam under reduced
pressure is first converted to
electricity with a back
pressure steam turbine and
the low-pressure steam
exiting the backpressure
turbine is condensed in a
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18. Direct (non-electrical) uses of geothermal water
➢Shallower reservoirs of lower temperature -- 21-149°C (70-
300°F) are used directly in health spas, greenhouses, fish farms,
and industry and in space heating systems for homes, schools
and offices.
➢It is only during the last century that we have used geothermal
energy to produce electricity. But using geothermal water to
make our lives more comfortable is not new: people have used
it since the dawn of mankind. Wherever geothermal water is
available, people find creative ways to use its heat.
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19. Agriculture and aquaculture
➢Geothermal energy is used directly in agriculture and
aquaculture:
➢to help grow flowers, vegetables, and other crops in
greenhouses while snow-drifts pile up outside
➢to shorten the time needed for growing fish, shrimp,
abalone and alligators to maturity
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20. Industry
➢The heat from geothermal water is used worldwide for
industrial purposes. Some of these uses include drying fish,
fruits, vegetables and timber products, washing wool, dying
cloth, manufacturing paper and pasteurizing milk.
➢Geothermally heated water can be piped under sidewalks and
roads to keep them from icing over in freezing weather. Thermal
waters are also used to help extract gold and silver from ore and
even for refrigeration and ice-making.
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21. Hot Spring Bathing and Spas (Balneology)
➢For centuries, peoples of China, Iceland, Japan, New Zealand, North America and other
areas have used hot springs for cooking and bathing. The Romans used geothermal
water to treat eye and skin disease and, at Pompeii, to heat buildings. Medieval wars
were even fought over lands with hot springs.
➢In Europe, natural hot springs have been very popular health attractions. The first
known "health spa" was established in 1326 in Belgium. (One resort was named "Espa"
which means "fountain." The English word "spa" came from this name.) All over Eurasia
today, health spas are still very popular. Russia, for example, has 3,500 spas.
Japan is considered the world’s leader in balneology. The Japanese tradition of social
bathing dates back to ancient Buddhist rituals. Beppu, Japan, has 4,000 hot springs and
bathing facilities that attract 12 million tourists a year. Other countries with major spas
and hot springs include New Zealand, Mexico and the United States.
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22. District heating
➢The oldest and most common use of geothermal water,
apart from hot spring bathing, is to heat individual
buildings, and sometimes entire commercial and
residential districts.
➢A geothermal district heating system supplies heat by
pumping geothermal water -usually 60° C (140°F) or
hotter- from one or more wells drilled into a geothermal
reservoir. The geothermal water is passed through a heat
exchanger which transfers the heat to water in separate
pipes that is pumped to the buildings. After passing
through the heat exchanger, the geothermal water is
injected back into the reservoir where it can reheat and be
used again.
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23. Geothermal heat pumps
The heat pumps are machines that move heat in a direction opposite
to that in which it would tend to go naturally, i.e. from a cold space
or body to a warmer one. A heat pump is effectively nothing more
than a refrigeration unit. Any refrigeration device (window air
conditioner, refrigerator, freezer, etc.) moves heat from a space (to
keep it cool) and discharges that heat at higher temperatures. The
only difference between a heat pump and a refrigeration unit is the
desired effect, cooling for the refrigeration unit and heating for the
heat pump. A second distinguishing factor of many heat pumps is
that they are reversible and can provide either heating or cooling in
the space.
Geothermal heat pumps reduce electricity use 30-60% compared
with traditional heating and cooling systems, because the electricity
which powers them is used only to move heat, not to produce it. The
U.S. Environmental Protection Agency rates geothermal heat pumps
among the most efficient of heating and cooling technologies.
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24. Advantages of geothermal energy
➢Provides clean and safe energy using little land Is renewable
and sustainable
➢Generates continuous, reliable “baseload” power
➢Conserves fossil fuels and contributes to diversity in energy
sources
Avoids importing and benefits local economies Offers modular,
incremental development and village power to remote sites
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25. Conclusion:
Energy demand is increasing rapidly
worldwide. Some energy and environmental
experts predict that the growth of electricity
production and direct uses of geothermal
energy will be revitalized by international
commitments to reduce carbon dioxide
emissions to avert global climate change and
by the opening of markets to competition.
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26. End of Chapter Three
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