Geothermal energy

1. GEOTHERMAL ENERGY
Dr Fayaz A. Malla
Assistant Professor, Environmental Sciences
GDC Tral
Higher Education Department, Govt. of J&K

2. WHAT DOES THE WORD
"GEOTHERMAL" MEAN?
• Geothermal energy is the natural heat of the earth. Earth's interior heat
originated from its fiery consolidation of dust and gas over 4 billion years ago. It
is continually regenerated by the decay of radioactive elements, that occur in all
rocks.
• From the surface down through the crust, the normal temperature gradient - the
increase of temperature with the increase of depth - in the Earth's crust is 17 °C --
30 °C per kilometer of depth (50 °F -- 87 °F per mile).
• Below the crust is the mantle, made of highly viscous, partially molten rocks with
temperatures between 650 °C -- 1250 °C (1200 °F -- 2280 °F).
• At the Earth's core, which consists of a liquid outer core and a solid inner core,
temperatures vary from 4000 °C -- 7000 °C (7200 °F-- 12600 °F).

3. The Physics of Geothermal Energy
1st: The heat from impacts with large
bodies such as meteors and asteroids
was trapped in surrounding rock of the
planet and may have been enough in
certain circumstances to completely melt
the early Earth.
2nd: Remnant heat of an early Earth
event known as the Iron Catastrophe.
With much of early Earth still molten,
denser metals, particularly iron and
nickel, migrated to the center of the
planet. Tremendous amounts of frictional
heat was created.
3rd: Compression due to gravity.
Sources of Earth’s internal heat

4. The Physics of Geothermal Energy
• Detailed understanding of the nature of
heat below the Earth’s surface occurred
when scientists began to understand the
various origins of subterranean heat.
• Radiogenic heat was discovered by nuclear
physicists in the 1950’s.
• Radiogenic heat is generated by the decay
of radioactive isotopes of uranium,
potassium, and thorium, which are found
deep under the Earth’s surface, and
significantly contributes to the presence of
subterranean heat.
• Once radiogenic heat was understood,
along with other sources, the creation,
dissipation, and movement of underground
heat was better understood.
Earth’s Atomic Engine

5. HOW DOES
GEOTHERM
AL HEAT
GET UP TO
EARTH'S
SURFACE?
Conduction
• Heat from the Earth’s interior flows outward. It is
transferred to the outer layer of rock or the crust.
Convection
• In some regions, the mantle beneath the crust
may be hot enough to partly melt and create
magma. Magma rising upward out of the mantle
can bring intense shallow Magma or very hot rock
heat into the crust

6. Bringing the
Earth’s Heat to
the Surface
• In some instances, passive
heat extraction is used.
• In places with “hot rocks” at
the surface electricity is
created without the need
for heat extraction.
• Active heat extraction
requires energy input but
allows for power
production at many more
locations

7. History of Geothermal
Energy Usage
• For thousands of years, civilizations have
used naturally warm spring water for
various purposes
• This hot water was mostly used for
bathing and cleaning, but was also used to
heat living spaces
• In Ancient Rome, Hot spring water was
feed into large public bathing areas to
provide warm bathing for everyone
• Some large building were heated by
plumbing hot water through the floors

8. Larderello, Italy
• Geothermal energy was first
used to produce electricity in Italy
in the early 20th century. The first
working prototype was small and
constructed by Prince Gionori
Conti in 1905.
• This experimental unit paved
the way for the first commercially
viable unit, which in 1913 began
producing 250kWe

9. Reykjavik: The Smokey Bay
1755
In 1755, natural scientists drilled the first
holes for hot water wells
1930
In 1930, the first Icelandic buildings were
heated using geothermal energy
2008
In 2008, 52 water heating wells were in
operation, providing 2,400 liters per second
of water ranging from 62 to 132 ⁰C
Today
24% of Iceland’s electricity is produced from
Geothermal sources

10. HOW DO WE USE
GEOTHERMAL
ENERGY TODAY?
Domestic Use:
• Space Heating/Cooling
• Water Heating
Aquaculture use:
• Fish, Shrimp and Alligators
• Drying of fruits / vegetables
Industrial Use:
• Dying of cloth, washing wool, piping under sidewalks to
keep from freezing, manufacturing paper
Electricity Generation

11. Conversion of
Heat Energy

12. Dry Steam
Power Plants

13. Flash Steam
Power Plants

14. Binary-Cycle
Power Plants
• Most geothermal areas contain moderate-
temperature water (below 400°F).
• Energy is extracted from these fluids in binary-
cycle power plants.
• Process:
• Hot geothermal fluid and a secondary fluid
with a much lower boiling point than water
pass through a heat exchanger.
• Heat from the geothermal fluid causes the
secondary fluid to flash to vapor, which then
drives the turbines.
• Since this is a closed-loop system, virtually
nothing is emitted to the atmosphere.

15. SOME OF THE
ADVANTAGES OF USING
GEOTHERMAL ENERGY TO
GENERATE
ELECTRICITY
Clean:
• No emissions, safe to use
Reliable:
• Continuous, reliable base-load power
Sustainable / Reusable:
• Water can be recycled back into the earth and reused.
• No other fuel mixture required to create electricity.
Land Conservative:
• No major land requirements. Can be integrated into the
local area with no adverse effects
Flexible / Modular:
• Geothermal power plants can have modular designs,
with additional units installed in increments when
needed to fit growing demand for electricity

16. Geothermal Direct Use

17. Environmental
Impact
• Overall, geothermal power is a
sustainable, flexible, environmentally-
friendly resource.
• Main disadvantages:
• Emission of pollutant gases into
atmosphere
• Emission of toxic compounds to
surface level
• Possible cause of land instability
• Reliant on electricity power sources

18. Atmospheric
Pollution
• The practice of extracting fluid from deep
earth can cause dissolved (non-
condensable) gases to escape into the
atmosphere
• Major: CO2, CH4, NH3, H2S
• Minor: Hg vapor, C6H6 benzene
• Implications:
• Climate change
• Acid rain
• Health risks
• A relatively minor source of greenhouse
gases

19. Emission of Toxic Chemicals
• The heated water from geothermal sources may
contain boron, arsenic, mercury, antimony, and salt.
• Once the energy is extracted, the cooled water can
cause these trace toxins to come out of solution.
• High concentrations of toxins can cause environmental
damage.
• Solution: extracted (cooled) geothermal fluid is
commonly injected back into the source
• This closed-loop recycling technique prevents toxin
emission and prolongs the viable life of the source.

20. Geothermal energy is generated in over 20
countries. The United States is
the world's largest producer, and the
largest geothermal development in the world.
Global geothermal power generation potential is
between 70 to 80 gigawatts (GW). However, just
15% of known geothermal reserves around the
world are exploited for electricity production,
generating just 13 GW.

21. • The GSI (Geological Survey of India) has
identified 350 geothermal
energy locations in the country. The
most promising of these is in Puga
valley of Ladakh.
• The estimated potential for geothermal
energy in India is about 10000 MW.
• There are seven geothermal provinces
in India : the Himalayas, Sohana, West
coast, Cambay, Son-Narmada-Tapi
(SONATA), Godavari, and Mahanadi.
GEOTHERMAL ENERGY IN INDIA