Geothermal Energy

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CHAPTER-1
INTRODUCTION
1.1 Introduction
The word geothermal is derived from Greek word geo which means Earth and
thermal means heat. Geothermal energy is the heat from Earth crust which is due to
rocks and fluids and can be used to generate electricity. As this heat is continuously
generating in Earth so geothermal energy is a renewable energy source. According to
a recent study, there are 806 geothermal power projects in development around the
world with a combined capacity of 23,313 megawatts, with the majority located in
Asia, North America and Africa. Geothermal energy is one of the few renewable
energy resources that can provide continuous power with minimal visual and other
environmental impacts. Geothermal systems have a small footprint and no carbon
dioxide emissions. Although geothermal energy has provided commercial load
electricity for more than a century, it has often been ignored in developing energy
supply. MENA Geothermal in 2008, lunched the first geothermal system in
Palestinian residential complex. Warm geothermal waters at low temperatures (38-
70°C) are available in some regions in Palestine. MENA Geothermal Company is the
First Palestinian Company Succeeds in Using Renewable Energy in the West Bank
and Jordan. The sources ready for utilization at present could supply heat for about 50
ha of greenhouses (i.e. an equivalent of 5000 tons of petroleum fuel per year). Most of
the geothermal water is in deep wells (1000-1500m). Water is at low salinity and in
most cases can be used for irrigation. Further drilling can increase the geothermal
potential to supply heat for about 250 ha of heated greenhouses, which means
doubling the heated greenhouse area in Palestine.
Looking at overall projects in development, Asia is by far the most active, with a
combined planned capacity of around 10,100 megawatts. The majority of these
projects can be found in Indonesia, followed by the Philippines and Japan. North
America follows with around 6,340 megawatts in development; mostly in the U.S.
Africa has a planned capacity of around 2,500 megawatts, mainly in Kenya. European
development accounts for around 1,400 megawatts, which mostly falls on Iceland and

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Italy. Turkey, which was categorized as being part of the Middle East, has around 800
megawatts in development.
Geothermal energy is used in at least 21 countries all over the world to generate
electricity in the tune of 8000MW (Huttrer, 2001). For direct use (i.e., space heating
and cooling, fish farming, agricultural and industrial purposes), geothermal energy
has been used by 58 countries in the world accounting for total energy of more than
15,000MW (Lund and Freeston, 2001).
Looking at individual countries, Indonesia is the leading country, with more than
8,000 megawatts of projects in development. It is followed by the U.S. with around
6,100 MW in development. If all projects were to come on-line, America would still
remain the top country, with Indonesia coming in a close second.
1.2 Historical Development
The oldest known pool fed by a hot spring, built in the Qin dynasty in the 3rd
century BC
Hot springs have been used for bathing at least since Paleolithic times. The oldest
known spa is a stone pool on China's Lisan mountain built in the Qin Dynasty in the
3rd century BC, at the same site where the Huaqing Chi palace was later built. In the
first century AD, Romans conquered Aquae Sulis, now Bath, Somerset, England, and
used the hot springs there to feed public baths and underfloor heating. The admission
fees for these baths probably represent the first commercial use of geothermal power.
The world's oldest geothermal district heating system in Chaudes-Aigues, France, has
been operating since the 14th century. The earliest industrial exploitation began in
1827 with the use of geyser steam to extract boric acid from volcanic mud in
Larderello, Italy.
In 1892, America's first district heating system in Boise, Idaho was powered
directly by geothermal energy, and was copied in Klamath Falls, Oregon in 1900. The
first known building in the world to utilize geothermal energy as its primary heat
source was the Hot Lake Hotel in Union County, Oregon, whose construction was
completed in 1907. A deep geothermal well was used to heat greenhouses in Boise in
1926, and geysers were used to heat greenhouses in Iceland and Tuscany at about the

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same time. Charlie Lieb developed the first downhole heat exchanger in 1930 to heat
his house. Steam and hot water from geysers began heating homes in Iceland starting
in 1943.
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, at the same Larderello dry steam field
where geothermal acid extraction began. It successfully lit four light bulbs. Later, in
1911, the world's first commercial geothermal power plant was built there. It was the
world's only industrial producer of geothermal electricity until New Zealand built a
plant in 1958. In 2012, it produced some 594 megawatts.
Lord Kelvin invented the heat pump in 1852, and Heinrich Zoelly had
patented the idea of using it to draw heat from the ground in 1912. But it was not until
the late 1940s that the geothermal heat pump was successfully implemented. The
earliest one was probably Robert C. Webber's home-made 2.2 kW direct-exchange
system, but sources disagree as to the exact timeline of his invention. J. Donald
Kroeker designed the first commercial geothermal heat pump to heat the
Commonwealth Building (Portland, Oregon) and demonstrated it in 1946. Professor
Carl Nielsen of Ohio State University built the first residential open loop version in
his home in 1948. The technology became popular in Sweden as a result of the 1973
oil crisis, and has been growing slowly in worldwide acceptance since then. The 1979
development of polybutylene pipe greatly augmented the heat pump’s economic
viability.
In 1960, Pacific Gas and Electric began operation of the first successful
geothermal electric power plant in the United States at The Geysers in California. The
original turbine lasted for more than 30 years and produced 11 MW net power.
The binary cycle power plant was first demonstrated in 1967 in the USSR and
later introduced to the US in 1981. This technology allows the generation of
electricity from much lower temperature resources than previously. In 2006, a binary
cycle plant in Chena Hot Springs, Alaska, came on-line, producing electricity from a
record low fluid temperature of 57 °C (135 °F).

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1.3 Outline of Seminar
Chapter 1: Introduction
This chapter describes about the origin of Geothermal Energy and how it was
developed. Moreover it also highlights the present scenario of Geothermal Energy.
Chapter 2: Literature Survey
This chapter consists of evolution of Geothermal Energy; the research papers that led
to the development of Geothermal Energy.
Chapter 3: Sources of Geothermal Energy
In this chapter sources from which Geothermal Energy can be extracted are described
and also this chapter highlights the explorations methods of Geothermal Energy.
Chapter 4: Geothermal Energy in India
This chapter consists of goals and vision of Geothermal Energy in India. It talks about
the present scenario of Geothermal Energy in India.
Chapter 5: Conversion of Geothermal Energy into Electricity
This chapter reveals different types of conversion techniques used in conversion of
Geothermal Energy into Electricity.
Chapter 6: Costs related to Geothermal Energy
In this chapter the costs which are related to establish the geothermal plant and costs
which are related to extract energy from them are mentioned.
Chapter 7: Applications
Various applications of geothermal energy are described in this chapter.

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Chapter 8: Conclusion
Then we put an end to this seminar by having the conclusion followed by the
reference used for this seminar.

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CHAPTER-2
LITERATURE SURVEY
2.1 Introduction
When compared to fossil fuel energy sources such as coal and natural gas,
geothermal emerges as one of the least polluting forms of energy, producing virtually
zero air emissions. Geothermal offers a baseload source of reliable power that
compares favourably with fossil fuel power sources. But unless legislative changes
are enacted, geothermal energy will continue to be produced at only a fraction of its
potential.
2.2 Research Papers
2.2.1 Geothermal Energy : Indian scenario
Mukul Chandra Bora | 2010
In his work he said that Geothermal energy is an inexhaustible source of energy
and is available from earth crust. It is that renewable energy source which doesn’t
need any fuel to generate electricity, and the emissions connected with geothermal
energy are very low and negligible compared to emissions that result from fossil fuels
burning. Geothermal energy is gaining importance as alternate source of energy.
Geothermal energy based power production over the world has gone up from 5800
MW to 8400 MW from 1998 to 1999. Thus all the countries, except India, have
started using geothermal energy to generate power and support a variety of industries.
Nearly 70% of India's power production is based on coal due to the availability of
huge coal reserves in the country. Excessive use of fossils fuel will have deteriorating
effect on the quality of human life. This is the time for India to launch its geothermal
energy resources programme in a big way to implement clean development
mechanism (CDM). The country has enormous resources, which are lying untapped.
The country has the know-how and technology sources to generate power and support

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various industries using geothermal energy. This paper will briefly illustrate the
potential and challenges that are ahead in India with special reference to the Himalaya
region towards the use of Geothermal Energy.
2.2.2 Promoting Geothermal Energy: Air Emissions
Comparison and Externality Analysis
AlyssaKagel, KarlGawell | published in 2005
The authors acknowledge the U.S. Department of Energy, particularly Roy
Mink and Susan Norwood, for its generous funding and guidance. The authors also
extend special thanks to Kevin Porter and Christina Mudd of Exeter Associates Inc.
for their editorial assistance and feedback. A complete list of acknowledgements
precedes the document upon which this article is based,
Alyssa Kagel is Outreach and Research Officer at the Geothermal Energy
Association in Washington, DC, where she focuses on environmental science. She
holds a B.A. in Environmental Studies from Wesleyan University. She has previously
worked at the Brookhaven Division of Environmental Protection in New York, at the
office of Rep. Vivian Fisher (D-N.Y.), and has participated in and organized various
environment campaigns. She coauthored the white paper, Guide to Geothermal
Energy and the Environment, funded by the U.S. Department of Energy, which
provides the basis for this article.
Karl Gawell has been Executive Director of the Geothermal Energy Association
since 1997. Before then, he was Director of Government Affairs for the American
Wind Energy Association. He has studied in the Department of Economics at
Nottingham University, and holds a B.S. in Foreign Service from Georgetown
University. His background includes senior positions in several national
environmental organizations, including the National Wildlife Federation and The
Wilderness Society, and several positions in the U.S. Congress.

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2.2.3 The Criteria for Suitable Location of Geothermal plant
Anita Sowa-Watrak, Iwona Klosok-Bazan
Energy crisis around the world and implementation of so-called Package 3x20
where one of its demands aimed at increasing the share of renewable energy sources
in overall balance, result in a significant increase in the interest in geothermal energy,
and thus in the production of electricity from geothermal sources. Unfortunately, in
Poland and the Czech Republic we are dealing mainly with low and average
temperature deposits, which are used primarily for heating and leisure facilities. The
use of available sources for electricity production requires a series of tests and
analyses -geological and engineering. It is worth investing in this type of solution
because electricity derived from geothermal energy has a low impact on the
environment and, in contrast to other renewable sources of energy, is stable during the
day and available throughout the year. The main purpose of the article is to outline the
criteria of geothermal power plants location. The main factors determining influence
on location of geothermal power plants are: the temperature and the capacity of the
source, the depth of resources available and the degree of mineralization of water
sources as well as their efficiency. Moreover, the potential locations for binary
geothermal power plant creation in Poland has also been outlined.
2.2.4 Exergetic Performance Investigation of Medium-Low
Enthalpy Geothermal Power Generation
Junkui Cui | Published in 2009
In this paper it is described that the renewable energy sources are becoming
attractive solutions for clean and sustainable energy needs. Geothermal energy is
increasingly contributing to the power supply worldwide. In evaluating the efficiency
of energy conservation systems, the most commonly used measure is the energy
efficiency, for indicating the possibilities for thermodynamic improvement, energy
analysis is inadequate and exergy analysis is needed. The main purpose of this study
is to investigate the thermodynamic efficiency of binary power cycle from medium-
low enthalpy geothermal resources, and analyze the exergetic efficiency based on an
designed binary cycle power plant. The investigation results indicate that the binary-
cycle power generation has significant potential in performance improvement.

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CHAPTER-3
SOURCES OF GEOTHERMAL ENERGY
3.1 Introduction
Geothermal exploration is the exploration of the subsurface in search of viable
active geothermal regions with the goal of building a geothermal power plant, where
hot fluids drive turbines to create electricity. Exploration methods include a broad
range of disciplines including geology, geophysics, geochemistry and engineering.
Geothermal regions with adequate heat flow to fuel power plants are found in rift
zones, subduction zones and mantle plumes. Hot spots are characterized by four
geothermal elements. An active region will have:
 Heat Source - Shallow magmatic body, decaying radioactive elements or
ambient heat from high pressures.
 Reservoir - Collection of hot rocks from which heat can be drawn
 Geothermal Fluid - Gas, vapour and water found within the reservoir
 Recharge Area - Area surrounding the reservoir that rehydrates the
geothermal system.
Exploration involves not only identifying hot geothermal bodies, but also low-density,
cost effective regions to drill and already constituted plumbing systems inherent
within the subsurface. This information allows for higher success rates in geothermal
plant production as well as lower drilling costs.

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As much as 42% of all expenses associated with geothermal energy production can be
attributed to exploration. These costs are mostly from drilling operations necessary to
confirm or deny viable geothermal regions. Some geothermal experts have gone to
say that developments in exploration techniques and technologies have the potential
to bring the greatest advancements within the industry.
3.2 Methods of Geothermal Exploration
3.2.1 Drilling:
Drilling provides the most accurate information in the exploration process, but
is also the most costly exploration method.
Thermal gradient holes (TGH), exploration wells (slim holes), and full-scale production
wells (wildcats) provide the most reliable information on the subsurface. Temperature
gradients, thermal pockets and other geothermal characteristics can be measured
directly after drilling, providing valuable information.
Geothermal exploration wells rarely exceed 4 km in depth. Subsurface materials
associated with geothermal fields range from limestone to shale, volcanic rocks
and granite. Most drilled geothermal exploration wells, up to the production well, are
still considered to be within the exploration phase. Most consultants and engineers
consider exploration to continue until one production well is completed successfully.
Generally, the first wildcat well has a success rate of 25%. Following more analysis
and investigation, success rates then increase to a range from 60% to 80%. Although
expenses vary significantly, drilling costs are estimated at $400/ft. Therefore, it is
becoming paramount to investigate other means of exploration before drilling
operations commence. To increase the chances of successfully drilling, innovations
in remote sensing technologies have developed over the last 2 decades. These less
costly means of exploration are categorized into multiple fields including geology,
geochemistry and geophysics.
3.2.2 Geophysics:
There are subsequent methods under Geophysics :

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3.2.2.1 Seismology:
Seismology has played a significant role in the oil and gas industry and is now
being adapted to geothermal exploration. Seismic waves propagate and interact with
subterranean components and respond accordingly. Two sub categories exist that are
relevant to the source of the seismic signal. Active seismology relies on using
induced/man-made vibrations at or near the surface. Passive seismology uses
earthquakes, volcanic eruptions or other tectonic activity as sources.
Passive seismic studies use natural wave propagation through the earth. Geothermal
fields are often characterized by increased levels of seismicity. Earthquakes of lesser
magnitude are much more frequent than ones of larger magnitude. Therefore,
these micro earthquakes (MEQ), registering below 2.0 magnitude on the Richter scale, are
used to reveal subsurface qualities relating to geothermal exploration. The high rate of
MEQ in geothermal regions produce large datasets that don’t require long field
deployments.
Active Seismology, which has history in the oil and gas industry, involves studying
man made vibrational wave propagation. In these studies geophones (or other seismic
sensors) are spread across the study site. The most common geophone spreads are in
line, offset, in-line with centre shot and Fan shooting.
Many analytical techniques can be applied to active seismology studies but generally
all include Huygens Principle, Fermat’s Principle and Snell’s law. These basic principles
can be used to identify subsurface anomalies, reflective layers and other objects with
high impedance contrasts.
3.2.2.2 Gravity:
Gravimetry studies use changes in densities to characterize subsurface
properties. This method is well applied when identifying dense subsurface anomalies
including granite bodies, which are vital to locate in the geothermal exploration
projects. Subsurface fault lines are also identifiable with gravitational methods. These
faults are often identified as prime drilling locations as their densities are much less
than surrounding material. Developments in airborne gravitational studies yield large
amounts of data, which can be used to model the subsurface 3 dimensionally with
relatively high levels of accuracy.

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Changes in groundwater levels may also be measured and identified with gravitational
methods. This recharge element is imperative in creating productive geothermal
systems. Pore density and subsequent overall density are affected by fluid flow and
therefore change the gravitational field. When correlated with current weather
conditions, this can be measured and modeled to estimate the rate of recharge in
geothermal reservoirs.
Unfortunately, there are many other factors that must be realized before data from a
gravity study can be interpreted. The average gravitational field the earth produces is
920 cm/c^2. Objects of concern produce a significantly smaller gravitational field.
Therefore, instrumentation must detect variations as small as 0.00001%. Other
considerations including elevation, latitude and weather conditions must be carefully
observed and taken into account.[6]
3.2.2.3 Resistivity and magnetotellurics:
Magnetotellurics (MT) measurements allow detection of resistivity anomalies
associated with productive geothermal structures, including faults and the presence of
a cap rock, and allow for estimation of geothermal reservoir temperatures at various
depths. MT has successfully contributed to the successful mapping and development
of geothermal resources around the world since the early 1980s, including in the U.S.
and countries located on the Pacific Ring of Fire such as Japan, New Zealand, the
Philippines, Ecuador, and Peru.
Geological materials are generally poor electrical conductors and have a high
resistivity. Hydrothermal fluids in the pores and fractures of the earth, however,
increase the conductivity of the subsurface material. This change in conductivity is
used to map the subsurface geology and estimate the subsurface material composition.
Resistivity measurements are made using a series of probes distributed tens to
hundreds of meters apart, to detect the electrical response of the Earth to injection of
electrical impulses in order to reconstruct the distribution of electrical resistance in the
rocks. Since flowing geothermal waters can be detected as zones of low resistance, it
is possible to map geothermal resources using such a technique. However, care must
be exercised when interpreting low resistivity zones since they may also be caused by
changes in rock type and temperature.

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The Earth’s magnetic field varies in intensity and orientation during the day inducing
detectable electrical currents in the Earth’s crust. The range of the frequency of those
currents allows a multispectral analysis of the variation in the electromagnetic local
field. As a result, it is possible a tomographic reconstruction of geology, since the
currents are determined by the underlying response of the different rocks to the
changing magnetic field.
3.2.2.4 Magnetics:
The most common application magnetism has in geothermal exploration
involves identifying the depth of the curie point or curie temperature. At the curie point,
materials will change from ferromagnetic to paramagnetic. Locating curie temperatures
for known subsurface materials provides estimates on future plant productivity. For
example, titanomagnetitite, a common material in geothermal fields, has a curie
temperature between 200-570 degrees Celsius. Simple geometric anomalies modelled
at different depths are used to best estimate the curie depth.
3.2.3 Geochemistry:
This science is readily used in geothermal exploration. Scientists within this
field relate surface fluid properties and geologic data to geothermal bodies.
Temperature, isotopic ratios, elemental ratios, mercury & CO2 concentrations are all
data points under close examination. Geothermometers and other instrumentation are
placed around field sites to increase the fidelity of subsurface temperature estimates.
3.3 Sources
3.3.1 Hot water reservoirs:
Hot water geothermal reservoirs are the most common type. In a liquid-
dominated reservoir, the hot water has not vaporized into steam because the reservoir
is saturated with water and is under pressure.

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Fig-3.1:Hot water reservoir
To generate electricity, the hot water is piped from geothermal wells to one or more
separators where the pressure is lowered and the water flashes into steam. The steam
then propels a turbine generator to produce electricity. The steam is cooled and
condensed and either used in the plant's cooling system or injected back into the
geothermal reservoir.
A binary cycle power plant is used when the water in a hot water reservoir is not hot
enough to flash into steam. Instead, the lower-temperature hot water is used to heat a
fluid that expands when warmed. The turbine is powered from the expanded,
pressurized fluid. Afterwards, the fluid is cooled and recycled to be heated over and
over again.
3.3.2 Natural steam reservoirs:
In a Natural steam reservoir, the natural steam is piped directly from a
geothermal well to power a turbine generator. The spent steam (condensed water) can
be used in the plant's cooling system and injected back into the reservoir to maintain
water and pressure levels. Dry steam reservoirs are rare but highly efficient at
producing electricity. The Geysers in California is the largest and best known dry

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steam reservoir. Here, steam is obtained by drilling wells from 7,000 to 10,000 feet
deep.
3.3.3Geo pressurised reservoirs:
3.3.3.1 Geopressure: geopressure Pressure beneath the surface of the earth;
especially, a pressure of greater than usual strength existing in a subsurface formation;
for example, a fluid deposit that is under very high pressure because it bears part of
the overburden load. Simply stated: The pressure within the earth, or formation
pressure
3.3.3.2. Benefits of Geo pressurised reservoirs: The composition of the
waters in normally pressured reservoirs often differs from the composition of the
waters in geopressured or abnormally high-pressured reservoirs. Geopressure zones
immediately subjacent to platform carbonate rocks can be modelled to serve as
proximal sources of hydrothermal fluids for epigenetic Pb-Zn deposits in sedimentary
basins. In some geopressure zones of the Gulf of Mexico, geothermal gradients can be
as high as 10°C 100 m−1
. This arises because the water-saturated geopressured shale
masses act as thermal insulators. Geopressure zones may have sufficient fluid
pressure to rupture overlying strata, providing a vertical conduit for hot mineralized
brine to migrate directly into carbonate host rocks. There are several theories
concerning the cause of the geopressured zones. Knowledge of how to locate
geopressured zones is important in drilling operations, because if such a zone is
drilled into without adequate preparation, the well may blow out, perhaps causing a
fire, loss of the well, loss of the drilling rig, or even loss of life. The usual precaution,
if the driller knows of a high-pressure zone, is to increase the weight of the drilling
mud; however, the continual use of heavyweight mud is much more expensive than
drilling with a lighter weight mud. As drilling and extinguish a fire at an ignited
blowing well are very expensive, steps are taken by the drilling company to assure
that an adequate drilling rig is used, that the optimum size borehole is drilled, that the
correct weight drilling mud is pumped down, that strong enough casing is inserted
into the well, and that blow-out preventers are operative.

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3.3.4 Normal geothermal gradient:
Geothermal gradient is the rate of increasing temperature with respect to
increasing depth in the Earth's interior. Away from tectonic plate boundaries, it is
about 25–30 °C/km (72-87 °F/mi) of depth near the surface in most of the
world. Strictly speaking, geo-thermal necessarily refers to the Earth but the concept
may be applied to other planets. The Earth's internal heat comes from a combination of
residual heat from planetary accretion, heat produced through radioactive decay, latent
heat from core crystallization, and possibly heat from other sources. The major heat-
producing isotopes in the Earth are potassium-40, uranium-238, uranium-235, and thorium-
232.At the centre of the planet, the temperature may be up to 7,000 K and the pressure
could reach 360 GPa (3.6 million atm).
Fig-3.2:Temperature gradient
Because much of the heat is provided by radioactive decay, scientists believe that
early in Earth history, before isotopes with short half-lives had been depleted, Earth's
heat production would have been much higher. Heat production was twice that of
present-day at approximately 3 billion years ago, resulting in larger temperature

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gradients within the Earth, larger rates of mantle convection and plate tectonics, allowing
the production of igneous rocks such as komatiites that are no longer formed.
3.3.5. Hot dry rocks (HDR):
Hot dry rock (HDR) is an abundant source of geothermal energy available for use.
A vast store of thermal energy is contained within hot - but essentially dry -
impervious crystalline basement rocks found almost everywhere deep beneath the
earth’s surface.
Although often confused with the relatively limited hydrothermal resource already
commercialized to a large extent, HDR geothermal energy is very different.[3]
Whereas
hydrothermal energy production can only exploit hot fluids already in place in the
earth’s crust, an HDR system (consisting of the pressurized HDR reservoir, the
boreholes drilled from the surface, and the surface injection pumps and associated
plumbing) recovers the earth’s heat from hot but dry regions via the closed-loop
circulation of pressurized fluid. This fluid, injected from the surface under high
pressure, opens pre-existing joints in the basement rock, creating a man-made
reservoir which can be as much as a cubic kilometre in size. The fluid injected into
the reservoir absorbs thermal energy from the high-temperature rock surfaces and
then serves as the conveyor for transporting the heat to the surface for practical use.

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CHAPTER-4
GEOTHERMAL ENERGY IN INDIA
4.1 Introduction
The energy scenario in India is fast changing with the emphasis given in the
XIIth Five Year Plan on renewable sources of energy. Though the dominance of fossil
fuels, viz. coal and oil will continue in the energy sector for the next few decades, the
concern for reducing the greenhouse gas emissions warrants increasing use of green
energy renewable energy sources as a substitute to oil and coal. Solar energy and
wind energy are major contributors of the renewable energy as these resources are
widely distributed all over India and are available round the year. Geothermal energy
is also an additional source of renewable energy with site specific availability and
potential for consistent supply in all the seasons throughout the year.
Geothermal Energy is heat stored in earth’s crust, which is manifested on surface as
hot springs and is being used worldwide since the beginning of the last century for
electricity generation and also for direct heat application. The global geothermal
power generation was at 13.3 Gigawatts (GW) in January, 2016, and if the current
trend continues, is projected to increase to 18.4 GW by 2021 and 32 GW by 2030
(www.geoenergy.org). Top five leading countries in the geothermal power generation
are USA (3450 MW), Philippines (1870 MW), Indonesia (1340 MW), Mexico (1017
MW) and New Zealand (1005 MW) as of 2015. The total installed capacity, reported
in 2014 for geothermal direct utilization worldwide is around 70.3 GWt and the
leading countries with the largest capacity of geothermal direct utilization are China,
Sweden, USA, Turkey, Iceland, Japan, Hungary, Italy and New Zealand. For
harnessing geothermal energy in India the Ministry of New & Renewable Energy
(MNRE) has been supporting R&D on exploration activities and Resource
Assessment during last 25 years. This includes formation of expert groups, working
group, core group and committees in addition to providing financial support for such
projects and for resource assessment.

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Government of India, Ministry of New and Renewable Energy (MNRE) has been
contemplating major initiative in deployment of geothermal technology for harnessing
the geothermal energy in the country during past few decades. Since geothermal Page
3 of 23 electricity generation is characteristically site and technology specific and
Indian geothermal resources are mostly of low to medium enthalpy type, the
Government is planning to encourage the demonstration projects at the first stage to
assess the technical viability of the selected geothermal resources before going to the
commercial models.
Geothermal energy is a site specific renewable source of energy specifically suitable
for catering to the energy needs of remote/interior localities. Considering the possible
utility of geothermal energy as a substitute of heat as well as energy source and the
need of the hour to harness all possible sources of renewable energy, the Ministry of
New & Renewable Energy has formulated Development framework for the
exploration and development of geothermal resources in India, draft of which was
circulated in March, 2015.
4.2 Geothermal Energy Scenario: India and the world
Geothermal power plants operated in at least 24 countries in 2010, and
geothermal energy was used directly for heat in at least 78 countries. These countries
currently have geothermal power plants with a total capacity of 10.7 GW, but 88% of
it is generated in just seven countries: the United States, the Philippines, Indonesia,
Mexico, Italy, New Zealand, and Iceland. The most significant capacity increases
since 2004 were seen in Iceland and Turkey. Both countries doubled their capacity.
Iceland has the largest share of geothermal power contributing to electricity supply
(25%), followed by the Philippines (18%).
The number of countries utilizing geothermal energy to generate electricity has more
than doubled since 1975, increasing from 10 in 1975 to 24 in 2004. In 2003, total
geothermal energy supply was 20 MToE (metric Tonne Oil Equivalent), accounting
for 0.4% of total primary energy supply in IEA member countries. The share of
geothermal in total renewable energy supply was 7.1%. Over the last 20 years, capital
costs for geothermal power systems decreased by a significant 50%. Such large cost
reductions are often the result of solving the “easier” problems associated with
science and technology improvement in the early years of development.

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Although geothermal power development slowed in 2010, with global capacity
reaching just over 11 GW, a significant acceleration in the rate of deployment is
expected as advanced technologies allow for development in new countries. Heat
output from geothermal sources increased by an average rate of almost 9% annually
over the past decade, due mainly to rapid growth in the use of ground-source heat
pumps. Use of geothermal energy for combined heat and power is also on the rise.
India has reasonably good potential for geothermal; the potential geothermal
provinces can produce 10,600 MW of power (but experts are confident only to the
extent of 100 MW). But yet geothermal power projects has not been exploited at all,
owing to a variety of reasons, the chief being the availability of plentiful coal at cheap
costs. However, with increasing environmental problems with coal based projects,
India will need to start depending on clean and eco-friendly energy sources in future;
one of which could be geothermal
In India, exploration and study of geothermal fields started in 1970. 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.
4.3 The Vision and Goals
As per the vision of Honourable Prime Minister on “24x7- Power For All”, the
Government is committed to bring about a transformative change in the power sector
and ensure affordable 24x7 power for all homes, industrial and commercial
establishments and adequate power for farms, in the next few years.
The geothermal Framework envisages to make a substantial contribution to India’s
long-term energy supply and reduce our national greenhouse gas emissions by
developing a sustainable, safe, secure, socially and environmentally responsible
geothermal energy industry, apart from creating new employment opportunities and
leading to environmentally sustainable development by the means of deployment of
20 MW(elect) and additional 1,000 MW(thermal) Geothermal Energy Capacity in the

21
initial phase till 2019 and 10,000 MW (thermal) and 500 MW(elect) by 2030. The
demand of electricity requirement can be mitigated by deploying Ground Source Heat
Pumps (GSHP’S) and retrofitting the existing HVAC systems with GSHP based
system. Geothermal Resource Assessment is being planned in 2016-2017 for public
domain.
Ministry is planning to encourage the International Collaboration with the world
leaders in Geothermal Energy like USA, Iceland, Philippines, Indonesia, Mexico and
New Zealand for support to accelerate deployment of geothermal energy by
international investment promotion (100% FDI in RE Sector), customized capacity
building and technical assistance to key stakeholders, help in mitigating the
exploratory risk, technological support etc.
4.4 History of Geothermal (GT)Studies in India
In India, preliminary assessments of geothermal resources by Geological
Survey of India (GSI) have indicated prospects of development of Geothermal Power.
Systematic efforts to explore the geothermal energy resources commenced in 1973
and 340 hot springs have identified in different parts of India with surface temperature
ranges from 35 °C to as much as 98 °C. Preliminary assessment suggests that except
for some Himalayan geothermal resources, where temperature may be in excess of
200 0C, India is in low and medium heat enthalpy zone with resource temperature of
100 to180 °C.
At present India is at nascent stage of harnessing its geothermal resources, owing to a
variety of reasons, the chief being the availability of plentiful coal at cheap costs and
relative abundance of hydropower in Himalayan region. However, with increasing
environmental problems with coal based projects and the need of the hour to harness
all available renewable energy sources, India needs to develop clean and eco-friendly
energy sources in future; one of which would be geothermal.
In India, many areas have been taken up for exploration of Geothermal Energy. Thirty
one areas have been examined in detail and shallow drilling has been completed in
sixteen areas (i.e., up to a maximum depth of 700 m in select areas and much less in
other areas). Development of geothermal resources requires deeper level exploration
and utilization of the energy for electricity generation. The deeper level exploration in

22
India could not be taken up due to non-availability of machinery and equipment and
lack of expertise in geothermal deep drilling.
Presently, the only direct-use of geothermal energy in the country is for bathing,
swimming and balneology and occasionally as a source of energy for cooking. The
increase in the annual geothermal use for balneology, bathing and swimming has gone
from 2,545 TJ in 2010 to 4,152 TJ in 2014; with an installed capacity of 981 MWt. It
is estimated that 5.0 MWt and 150 TJ/yr is used for cooking, which is included in the
other category. Thus, the total geothermal energy use for the country is 986 MWt.
Residential & Commercial building air conditioning consumes 30-60 % of the total
electricity consumption. The penetration of air conditioners in India is 8 % and is
Page 9 of 23 expected to grow to 30 % in ten years. Therefore India will need 83 GW
of power for cooling the buildings in next six years. Mainly cities with large energy
guzzlers infrastructure projects such as hotels, metro-stations and airports are
attributed for peak load when cooling loads builds up. Geo Exchange Heat pumps
based district cooling systems can cool community with 3000 houses without need of
AC for each room. District cooling circulates cold air in pipe for air conditioning
purposes. Geo Exchange Heat pumps based district cooling systems can save 30-60 %
savings for air conditioning load.
4.5 Potential in India
It has been estimated from geological, geochemical, shallow geophysical and
shallow drilling data it is estimated that India has about 10,000 MWe of geothermal
power potential that can be harnessed for various purposes.

23
Fig-4.1:Geothermal map of India
Rocks covered on the surface of India ranging in age from more than 4500 million
years to the present day and distributed in different geographical units. The rocks
comprise of Archean, Proterozoic, the marine and continental Palaeozoic, Mesozoic,
Teritary, Quaternary etc., More than 300 hot spring locations have been identified by
Geological survey of India (Thussu, 2000). The surface temperature of the hot springs
ranges from 35 C to as much as 98 C. These hot springs have been grouped together
and termed as different geothermal provinces based on their occurrence in specific
geotectonic regions, geological and structural regions such as occurrence in organic
belt regions, structural grabens, deep fault zones, active volcanic regions etc.,
Different orogenic regions are – Himalayan geothermal province, Naga-Lushai
geothermal province, Andaman-Nicobar Islands geothermal province and non-
orogenic regions are – Cambay graben, Son-Narmada-Tapi graben, west coast,
Damodar valley, Mahanadi valley, Godavari valley etc.

24
Some of the most promising geothermal sites for the development of geothermal
energy are:
 Puga in Jammu & Kashmir
 Cambay Graben in Gujarat
 Tattapani in Chhattisgarh
 Chhumathang in Jammu & Kashmir
 Manikaran in Himachal Pradesh
 Surajkund in Jharkhand
 Ratnagiri in Maharashtra
 Rajgir in Bihar
 Topaban in Uttarakhand
 Sohana belt in Haryana
 Bakreshwar in West Bengal
 Khammam in Telangana
 Badrachalam in Telangana
 Chintalapudi in Telangana
On the basis of enthalpy characteristics, the geothermal systems in India, can be
classified into medium enthalpy (125°C-200°C) and low enthalpy (<125°C)
geothermal
systems. These are described as follows:
4.5.1 Medium enthalpy geothermal energy systems:
The medium enthalpy geothermal energy resources are associated with:
1. Younger intrusive granites as in Himalayas, viz Puga-Chumathang, Parbati, Beas
And Satluj Valley geothermal fields.
2. Major tectonic features/lineaments such as the West Coast areas of
Maharashtra; along the Son-Narmada-Tapi lineament zone at Salbardi, Tapi;
Satpura areas in Maharashtra;
3. Tattapani in Chhattisgarh and Rajgir-Monghyar in Bihar; Surajkund, Tatta and
Jarom in Jharkhand, Bakreshwar in West Bengaland Eastern Ghat tracts of Orissa.

25
4. Rift and grabens of Gondwana basins of Damodar, Godavari and MahanadiValleys.
5. Quaternary and tertiary sediments occurring in a graban in the Cambay basin of
West Coast.
4.5.2 Low enthalpy geothermal energy systems:
The low enthalpy geothermal energy systems are associated with:
1. Tertiary tectonism and neo tectonic activity.
2. Shield areas with localized abnormal heat flow, which is normally very low.
4.6 Current projects in India
There are no operational geothermal plants in India.
Geothermal Field Estimated (min.) reservoir
Temp (Approx)
Status
Puga geothermal field 240̊̊̊C at 2000m From geochemical and deep
geophysical studies (MT)
Tattapani Sarguja
(Chhattisgarh)
120̊̊̊C - 150̊̊̊C at 500 meter and
200 Cat 2000 m
Magnetotelluric survey done by
NGRI
Tapoban Chamoli
(Uttarakhand)
100̊̊̊C at 430 meter Magnetotelluric survey done by
NGRI
Cambay Garben (Gujrat) 160̊̊̊C at 1900 meter (From Oil
exploration borehole)
Steam discharge was estimated 3000
cu meter/ day with high temprature
gradient.
Badrinath Chamoli
(Uttarakhand)
150̊̊̊C estimated Magneto-telluric study was done by
NGRI Deep drilling required to
ascertain geothermal field
Surajkund Hazaribagh
(Jharkhand)
110̊̊̊C Magneto-telluric study was done by
NGRI.
Heat rate 128.6 mW/m2
Manikaran
Kullu (H P)
NGRI.
Heat rate 128.6 mW/m2
Kasol
Kullu (H P)
NGRI
Table-4.1:Geothermal fields in India

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4.7 Geothermal companies in India
4.7.1 Panx Geothermal
India’s geothermal provinces are well known for high geothermal gradients
and temperatures. The country’s geothermal potential is currently estimated at more
than 10,000 megawatts.
Panax is targeting projects in the Himalayan geothermal province which has an
extreme high-heat zone and is abundant in geothermal resources. Panax has focused
its attention on the Puga Valley which is considered one of the most promising
geothermal regions in the country.
Panax has strategically entered into India’s geothermal industry by partnering with
locally-owned companies to explore and develop geothermal projects with
commercially attractive tariffs.
4.7.2 LNJ Bhilwara
New Delhi, Nov 23 2007, Iceland's Glitnir bank today signed an MoU with the
Rs 2,700-crore LNJ Bhilwara Group to set up geothermal power plants in India and
Nepal.
The bank is also eyeing partnerships with Indian small and medium firms to foray into
seafood and offshore rigs segments.
The two partners would conduct studies to explore the possibilities of developing at
various locations geothermal power plants, which tap heat beneath the earth's surface
to generate energy.
"Geothermal is one of our core sectors of operations worldwide. We have signed the
MoU to make a collaborative effort to explore and develop geothermal power in India
an Nepal," Glitnir Executive Director Bala Kamallakharan said here.
Kamallakharan, however, said no investment commitments have been made yet as the
projects are still in pre-feasibility stage. As per the initial surveys, 2-3 locations in
Jammu and Kashmir have been identified, he said.
"We will start with pilot projects of 5 MW to begin with as we have done in other
countries such as China. Bigger projects could follow on their successful completion,"
he added.

27
The bank is also eyeing biomass, sea food and offshore supply vessels segment in
India.
"We are talking to several companies to offer the role of a catalyst to accelerate the
consolidation in the industry. We are, however, focused on small and mid-sized firms,
which are neglected by other banks," Kamallakharan said. PTI
4.7.3 Tata Power
Mumbai: Tata Group company Tata Power Monday 2009 said it is looking at
the possibility of setting up a geothermal power plant and a solar power plant of 5
MW each at a suitable location in Gujarat, a move that will strengthen the renewable
energy portfolio of the company.
Tata Power has entered into an agreement in this regard with the Gujarat government
“to explore the possibility of setting up a 5 MW geothermal power plant in phase I,"
the Tata group company said in a filing to the Bombay Stock Exchange.
“The company also signed an MoU for developing a 5 MW solar power plant in
Gujarat," the filing added.
4.7.4 Thermax
Pune-based engineering solutions company Thermax is expanding its footprint
in the geothermal energy space.
After Puga in Leh, the company is looking at developing a power plant based on
geothermal energy in the Konkan region of Maharashtra.
The company is planning to enter into a memorandum of understanding with the
Maharashtra Energy Development Agency (MEDA), an arm of the State Government,
which promotes use of non-conventional energy.
A power plant based on geothermal energy harnesses the continuous heat from the
earth's inner layers for electricity production. In certain areas the earth's crust is more
conducive for setting up the plants. In Maharashtra, such favourable areas are found
on the coast, from the Maharashtra-Gujarat border to Rajapur in Konkan region.
Thermax has a joint venture with Reykjavik Geothermal, an Iceland-based company,
for developing the geothermal energy business in India. The joint venture is
developing a 3-MW geothermal plant in Puga valley, Leh on an experimental basis.
Phase I

28
Mr M.S. Unnikrishnan, Managing Director of Thermax, told Business Line that the
company has got a block around Rajapur for exploring geothermal energy. In the first
phase, a geological study would be conducted by non-invasive means and depending
on the success of this phase, further investigation would be carried out by drilling 1
km deep experimental wells, he said.
He said that currently it is difficult to predict the size of the plant as the size of the
geothermal field is not known.
“If we come across a large geothermal energy field, which could produce about 100
MW of power, then we could even form a separate company for setting up that plant,”
Mr Unnikrishnan said.
He said around Rs 10 crore is required developing one Megawatt of geothermal
energy. Since the heat continuously emanates from the earth's crust the load factor of
the plant is about 99 per cent.
According to an international geothermal expert, the power tariff from geothermal
plants is comparable to a thermal coal plant, which is in the range of Rs 2 to Rs 3 per
unit, while power from solar units are being sold at Rs 15 per unit.
Published on January 24, 2011
4.7.5 NTPC
The NTPC ltd will get drilled an exploratory bore well soon to establish
geothermal potential for power generation from Tatapani geothermal reservoir in
Balrampur district of Chhattisgarh, officials informed.
For resource assessment of geothermal reservoir at Tatapani, measurement of
geological parameters like MT studies, DRS studies is in progress, they informed.
The Project has been taken up under aegis of Chhattisgarh Renewable Energy
Development Agency (CREDA) in association with Geological Survey of India and
National Geographic Research Institute, Hyderabad.
22 August 2017

29
4.7.8 Avin Energy Systems
Avin Energy Systems Pvt Ltd has explored possibilities of setting up
geothermal power projects in Gujarat. Plans are underway to set up the first 5 MW
power generating plant using geothermal energy.
"AVIN"® has already done most of the ground work in regard to geothermal power
generation in Gujarat and in the coming future expects to set up geothermal power
generating units in Gujarat in the order of 1000 MW capacity which should, in a way,
feed the electricity requirements of not only the State but also the neighbouring States.
4.7.9 GeoSyndicate Power Private Limited
GeoSyndicate Power Pvt. Ltd. brings together established technology and a
wealth of expertise generated over a period of four decades. Ours is a congregation of
an experienced, established, scientific, engineering and management expertise.
Widely used over the world but first time in India, now with GeoSyndicate Power
Private Limited, geothermal is the energy for the future. GeoSyndicate Power Private
Limited aims at promoting the use of non conventional energy mechanisms to deliver
high efficiency and low cost electricity to the Indian Rural and power sectors, thereby
containing the pollution levels and giving Clean air for millions.
Besides power generation using Geothermal energy, the company also intends to
bring forth products pertaining to various Geo-Resources and Geo-Processes. Each of
the products / processes shall serve a specific need according to the required
parameters. The assets thus generated, as a whole, would be a value addition by the
company.
4.8 Geothermal Research Centres
4.8.1 MeSy India
MeSy India acts as technical arm to governmental institutions in the
conduction of scientific and geothermal research projects, and stimulates new R&D
projects in collaboration with Indian national research institutions and international
organizations, in particular in the field of techniques and earthquake mechanisms,

30
reservoir induced seismicity, advanced mining technologies, ground water production
stimulation, use of geothermal energy, hazardous underground waste storage.

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CHAPTER-5
CONVERSION OF GEOTHERMAL ENERGY
INTO ELECTRICTY
5.1 Introduction
Geothermal energy is derived from heat that originates in the Earth, which is
considered to be a clean, renewable energy source. Currently, geothermal energy use
mainly falls into two main categories, that is, direct use and electric power generation.
Geothermal water directly is used in district or space heating, greenhouses,
aquaculture and various industrial applications. Electric power generation of
geothermal energy utilizes energy in brine and hot rocks at a greater depth beneath the
Earth's surface. The total geothermal installed capacity per power generation in 2007
worldwide has increased to 9732 MW.
The type of energy conversion system used to produce electrical power from a
geothermal resource depends on the type and quality (temperature) of the resource.
Vapour-dominated resources use conversion systems where the produced steam is
expanded directly through a turbine. Liquid-dominated resources use either flash-
steam or binary systems, with the binary conversion system predominately used with
the lower temperature resources.
5.2 Types of Geothermal Resources
Geothermal energy comes in either vapor-dominated or liquid-dominated forms.
5.2.1Liquid-dominated plants
Liquid-dominated reservoirs (LDRs) were more common with temperatures
greater than 200 °C (392 °F) and are found near young volcanoes surrounding the
Pacific Ocean and in rift zones and hot spots. Flash plants are the common way to
generate electricity from these sources. Pumps are generally not required, powered
instead when the water turns to steam. Most wells generate 2-10 MW. Steam is
separated from liquid via cyclone separators, while the liquid is returned to the
reservoir for reheating/reuse. As of 2013, the largest liquid system is Cerro Prieto in

32
Mexico, which generates 750 MW from temperatures reaching 350 °C (662 °F). The
Salton Sea field in Southern California offers the potential of generating 2000 MW.
Lower temperature LDRs (120–200 °C) require pumping. They are common in
extensional terrains, where heating takes place via deep circulation along faults, such
as in the Western US and Turkey. Water passes through a heat exchanger in a
Rankine cycle binary plant. The water vaporizes an organic working fluid that drives
a turbine. These binary plants originated in the Soviet Union in the late 1960s and
predominate in new US plants. Binary plants have no emissions.
5.2.2Thermal Energy
Lower temperature sources produce the energy equivalent of 100M BBL per
year. Sources with temperatures of 30–150 °C are used without conversion to
electricity as district heating, greenhouses, fisheries, mineral recovery, industrial
process heating and bathing in 75 countries. Heat pumps extract energy from shallow
sources at 10–20 °C in 43 countries for use in space heating and cooling. Home
heating is the fastest-growing means of exploiting geothermal energy, with global
annual growth rate of 30% in 2005 and 20% in 2012.
Approximately 270 pet joules (PJ) of geothermal heating was used in 2004. More than
half went for space heating, and another third for heated pools. The remainder
supported industrial and agricultural applications. Global installed capacity was 28
GW, but capacity factors tend to be low (30% on average) since heat is mostly needed
in winter. Some 88 PJ for space heating was extracted by an estimated 1.3 million
geothermal heat pumps with a total capacity of 15 GW.
Heat for these purposes may also be extracted from co-generation at a geothermal
electrical plant.
Heating is cost-effective at many more sites than electricity generation. At natural hot
springs or geysers, water can be piped directly into radiators. In hot, dry ground, earth
tubes or down hole heat exchangers can collect the heat. However, even in areas
where the ground is colder than room temperature, heat can often be extracted with a

33
geothermal heat pump more cost-effectively and cleanly than by conventional
furnaces. These devices draw on much shallower and colder resources than traditional
geothermal techniques. They frequently combine functions, including air
conditioning, seasonal thermal energy storage, solar energy collection, and electric
heating. Heat pumps can be used for space heating essentially anywhere.
Iceland is the world leader in direct applications. Some 92.5% of its homes are heated
with geothermal energy, saving Iceland over $100 million annually in avoided oil
imports. Reykjavík, Iceland has the world's biggest district heating system, often used
to heat pathways and roads to hinder the accumulation of ice. Once known as the most
polluted city in the world, it is now one of the cleanest.
5.3 Parameters that influence the sustainable use of
geothermal energy
 Establishment of extraction technology;
 Maximum operating time under economic conditions;
 The minimum level and temperature for which exploitation is economically
efficient
 Achieving efficient, fully automated systems that use as the geothermal water
primary agent with temperature <100 °C, which is specific for geothermal
deposits in Romania;
 Technical, economic and environmental aspects of geothermal energy use;
 Ways of using electricity production.
The earth absorb energy from the sun, then it emit this energy night time. The
variation in earth surface temperature is just in the first 10m from the external earth
surface. Below this distance the earth temperature start increasing with depth as a
result of the molten rocks in the core of the earth.

34
Fig-5.1:Earth Dynamics
If it is possible to reach the high temperature rocks a huge energy can be extracted
from the earth that could be used for electricity production, heating and cooling
purposes.
5.4 Conversion of Geothermal Energy
The electricity generation from geothermal energy is done by three ways namely
5.4.1Direct steam systems
When the geothermal resource produces a saturated or superheated vapor, the
steam is collected from the production wells and sent to a conventional steam turbine.
Before the steam enters the turbine, appropriate measures are taken to remove any

35
solid debris from the steam flow, as well as corrosive substances contained in the
process stream (typically removed with water washing). If the steam at the wellhead is
saturated, steps are taken to remove any liquid that is present or forms prior to the
steam entering the turbine. Normally, a condensing turbine is used; however, in some
instances, a backpressure turbine is used that exhausts steam directly to the ambient.
Fig-5.2:Direct steam system
The steam discharges to a condenser where it is condensed at a sub atmospheric
pressure (typically a few inches of Hg). The condenser shown in Fig. 1 is a barometric
condenser. In a barometric condenser, the cooling water is sprayed directly into the
steam, with the cooling water and condensate being pumped to a cooling tower where
the condensing heat load is rejected to the ambient. Some plants use surface
condensers where the latent heat from the condensing steam is transferred to cooling
water being circulated through the condenser tubes. With a surface condenser, the
cooling water and condensate are typically pumped to the cooling tower in separate
streams. The steam condensate provides a makeup water source for the evaporative
heat rejection system. Any excess condensate, together with the tower blow down, is
injected back into the reservoir.
Hydrothermal resources typically contain varying amounts of dissolved minerals and
gases that impact both the design and operation of the energy conversion systems. In

36
power cycles where steam is extracted from the geothermal resource and expanded in
a condensing turbine, the cycle design must account for the removal of the no
condensable gases extracted from the resource with the steam. If not removed, these
gases accumulate in the condenser, raising the turbine exhaust pressure and
decreasing power output. When hydrogen sulphide is present in the process steam, it
also accumulates in the condenser, though a portion partitions or dissolves in the
condensate or cooling water. When the hydrogen sulphide levels are sufficiently high
so that some abatement process of the condensate or cooling water is required, surface
condensers are typically used to minimize the quantity of water that has to be treated.
In addition, the noncondensable gas stream containing hydrogen sulphide must also
be treated prior to being released to the atmosphere.
5.4.2Flash Steam Plants
With few exceptions, the fluid in hydrothermal resources is predominantly
liquid. Frequently, the reservoir pressure is insufficient to overcome the hydrostatic
head in the wellbore and bring the fluid to the surface as a liquid, at flow rates
sufficient for commercial production. Depending on the power cycle used, it may be
necessary to use down hole pumps to provide the necessary flow. In instances when
the reservoir temperature is sufficiently high, the fluid is allowed to flash in the
wellbore. This reduces the hydrostatic head in the wellbore and allows more
production flow. When flashing occurs in the well, a two-phase fluid is produced
from the well. The conversion systems used with this flow condition are typically
flash-steam power cycles. In a single-flash cycle, a separator is used to separate the
fluid phases, with the steam phase being sent to a turbine.
Typically, in this cycle, the fluid pressure immediately upstream of the separator is
reduced, which results in additional flashing of the liquid phase and produces
additional steam flow. This single-flash steam power cycle is depicted in Fig. 2. Once
the steam leaves the separator, the cycle is very similar to that for a vapor-dominated
resource (Fig. 1). The saturated liquid brine leaving the separator is reinjected along
with cooling tower blow down and excess condensate.

37
Fig-5.3:Flash steam plant
The dual-flash steam power cycle adds a second low-pressure flash to the single-flash
cycle. In the dual-flash cycle, the liquid leaving the first (high pressure) separator
passes through a throttling device that lowers fluid pressure, producing steam as the
saturated liquid flashes. The steam from this second flash is sent either to a second
turbine or, if a single turbine is used, to the turbine at an intermediate stage. The
steam exhausting the turbine(s) is condensed with a heat-rejection system similar to
that of the steam plant used with a vapor-dominated resource. In the dual-flash cycle,
the optimum pressure of the first separator is higher than the optimum flash/separator
pressure in a single-flash cycle. Unless the resource temperature is high, the optimum
first-stage pressure can be found using an initial approximation that this separator
temperature is at the mid-point of the temperature where flashing starts to occur
(liquid reservoir temperature) and 100°C. The second, or low pressure, flash is
typically just above atmospheric pressure. As the resource temperature increases, the
optimum pressures for the two flash stages increase.
As with the direct steam systems (vapor-dominated resource), flash plants must have
provisions to remove noncondensable gases from the heat-rejection system, to remove
liquid from the saturated steam before it enters the turbine and, if levels are
sufficiently high, remove hydrogen sulfide from the noncondensable gas and
condensate streams. In addition, mineral precipitation is generally associated with the

38
flashing processes. This requires the use of chemical treatment in the wellbore,
separators, and injection system to prevent the deposition of solids on piping, casing,
and plant-component surfaces. The potential for mineral precipitation increases as the
fluid is flashed because the dissolved minerals concentrate in the unflashed, liquid
phase.
There are two types of Flash steam power plants
5.4.2.1 Single flash steam power plant
Figure 5.4 shows the schematic diagram of the single flash steam power plant.
The use of a flash system results in the elimination of a large portion of energy in
brine (liquid) form from the separator due to the low steam quality that emanates from
the two-phase fluid following the expansion valve. Single flash power plants are
usually considered as the most economical alternative for available geothermal
resources temperature above 190 °C. Higher temperature resources will produce more
liquid and steam for natural pressure conditions. For high-temperature resources
where two phase is dominated, the geothermal fluid is moved to the surface of the
borehole as a mixture of steam and liquid (brine). The separation process of steam
from brine occurs either in a horizontal separator under gravitational effect or in a
vertical separator under cyclonic motion. Following this the steam is directed to the
steam turbine while the saturated liquid is used as a heat input source for ORC in a
combined flash-ORC power plant (Gong et al. 2010) or, alternatively, the steam gets
re-injected to the reservoir through re-injection well. Single flash power plants are
classified according to their steam turbines types, i.e., the turbine exit conditions. Two
such basic types are the single flash with a condensation system and the single flash
back pressure system. In the first type, a condenser operating at very low pressure is
used to condensate the steam leaving the steam turbine. The condenser should operate
at low vacuum pressure to maintain a large enthalpy difference across the expansion
process of the steam turbine, hence resulting in a higher power output

39
Fig-5.4:Single flash steam power plant
The geothermal fluid usually contains non-condensable gases which are collected at
the condenser. Such a collection of gases may raise the condenser pressure, therefore
the gases should be removed from the condenser. This can be achieved by installing
vacuum pumps, compressors, or steam ejectors. The condenser heat removal is done
either by using a cooling tower or through cold air circulation in the condenser.
The condensate forms a small fraction of the cooling water circuit, a large portion of
which is then evaporated and dispersed into the atmosphere by the cooling tower. The
cooling water surplus (blow down) is disposed of in shallow injection wells. In single
flash condensation system, the condensate does have direct contact with the cooling
water.
5.4.2.2 Dual flash steam power plant
The dual flash steam plant (double flash) is preferred over the single flash
steam power plant depending on the conditions of the resource. In fact, it is similar to
the single flash power plant except that it produces more steam due to the use of two

40
separators. The schematic diagram of a dual flash power plant is shown in Fig. 2.
Using two separators leads to the use of a two-stage steam turbine, whereby one stage
operates at high pressure and the other at low pressure. Dual flash power plants are
able to produce up to 15–25% more power than a single flash power plant as their
power production capacity is in the range of 4.7 MW–110 MW. In a dual flash power
plant, the saturated liquid leaving the first separator is directed to a second separator
at lower pressure, resulting in more steam production.
Fig-5.4:Dual flash steam power plant
Following the steam production at high and low pressures, all steam gets directed to a
steam turbine using separate pipelines. The steam turbine can be a dual admission
turbine, a separate turbine, or may be made up of two separate tandem compound
turbines which operate based on the steam inlet pressure. The components of a dual
flash power plant are similar to those of a single flash steam power plant. The mineral
content of the water becomes concentrated depending on how the dual flash is
designed, hence the resource conditions are of extreme importance.

41
5.4.3 Binary Cycle Steam Power Plants
A binary conversion system refers to a power cycle where the geothermal fluid
provides the source of energy to a closed-loop Rankine cycle that uses a secondary
working fluid. In this closed loop, the working fluid is vaporized at pressure using the
energy in the geothermal fluid, expanded through a turbine, condensed, and pumped
back to the heat exchangers, thus completing the closed loop. This type of conversion
system is used commercially with liquid-dominated resources where the fluid
temperatures are below ~200°C. Typically, this conversion system requires the use of
pumped production wells to provide necessary well flow and to keep the fluid in a
liquid phase to prevent minerals from scaling of heat exchanger surfaces.
Fig-5.5:Binary cycle steam power plant
The system is depicted schematically in Fig. 5.5 with an evaporative heat-rejection
system. In some areas where geothermal resources are found, there is little water
available for evaporative heat-rejection systems. In these cases, the cooling tower and
condenser, shown in Fig. 3, are replaced with air-cooled condensers. Typically, all of
the geothermal fluid that passes through the binary plant heat exchangers is injected
back into the reservoir. This is environmentally desirable, as it effectively eliminates
all emissions to the ambient and, more importantly, provides a recharge to the
reservoir to maintain its productivity. The working fluids used in these plants are

42
volatile and typically are in a gas phase at room temperature and atmospheric
pressure. They liquefy at moderate pressures, and the entire working-fluid system is
generally operated at above atmospheric pressure to prevent the leakage of air into the
closed loop. Existing plants use isobutane, pentane, or isopentane working fluids.

43
CHAPTER-6
COSTS RELATED TO GEOTHERMAL
ENERGY
6.1 Introduction
Geothermal energy is the clean energy and has enormous potential in fulfilling
the energy needs for some of the countries. Geothermal energy does not produce
waste or generate greenhouse gases and is actually free which means it costs nothing.
Since it is the heat contained inside the earth and that heat will be produced for long
period of time even when non-renewable resources would start to diminish.
However, to harness that energy comes with the price tag, since you need some
method to extract that energy from inside the earth. The most common method to
extract that energy is through the use of geothermal power plant. The other method
which is mostly used by residential households is by the use of underground pipes.
The investment costs, mainly in drilling and equipment of the pipes accompanied by
the cost of the pump.
The main factors which can influence the decision for the use of geothermal energy
are geographical exploration to identify a suitable site, development of the site,
construction of the power plant, hire skilled professionals who can operate the plant
and transfer skilled manpower to those locations. Other factors which also come into
the picture are cost to the environment, operation and maintenance.
If you are a residential consumer, the main costs associated with it are labor, fitting of
long pipes under the ground. However that cost can soon be recovered within few
years with the advantages that it offers in the long term. Homes can have residential
solar powered systems that supply both heat and energy, along with a geothermal
heating system.
If compared this cost to the installation of heating system that uses fuel or and any
other energy source, that cost of installing and maintaining a geothermal heating
system may cost more by a significant amount. But, once the system is installed the

44
costs associated with the geothermal heating systems are much less than other heating
systems.
Governments of various countries offer incentives and rebates to residential as well as
industries to make use of geothermal energy where it is possible to harness that
energy. Everyone pays huge bills to heat or cool their homes that has long winters or
hot an humid summers. Then cost of geothermal energy can easily recovered in the
long term advantages that will accrue to the customer. Geothermal energy offers a
great solution to high energy bills. With this, your dependence on the fossil fuels will
be decreased and you will help in making this world pollution free.
6.2 Cost of a Geothermal Power Plant
According to studies, an economically competitive geothermal power plant
can cost as low as $3400 per kilowatt installed. (1) While the cost of a new
geothermal power plant is higher than that of a comparable natural gas facility, in the
long run the two are similar over time.
Fig-6.1:Estimated levelized cost of Electricity Generation

45
This is because natural gas construction costs account for only one third of the total
price of the facility, while the cost of the fuel at a natural gas facility represents two
thirds of the cost. The initial construction costs of a geothermal facility, in contrast,
represent two thirds or more of total costs. So although initial investment is high for
geothermal, natural gas and geothermal are still economically comparable over a long
term.
So costs of a geothermal plant are heavily weighted toward early expenses, rather than
fuel to keep them running. Well drilling and pipeline construction occur first,
followed by resource analysis of the drilling information. Next is design of the actual
plant. Power plant construction is usually completed concurrent with final field
development. The initial cost for the field and power plant is around $2500 per
installed kW in the U.S., probably $3000 to $5000/kWe for a small (<1Mwe) power
plant.
6.3 Cost of Power from Geothermal power plant
California Energy Commission (CEC) 2007 estimates place the levelized (2)
generation costs for a 50 MW geothermal binary plant at $92 per megawatt hour (3)
and for a 50 MW dual flash geothermal plant at $88 per megawatt hour, which over
the lifetime of the plant can be competitive with a variety of technologies, including
natural gas. (4) According to the CEC report, natural gas costs $101 per megawatt
hour for a 500 MW combined cycle power plant and $586 per megawatt hour for a
100 MW simple cycle plant. On average the cost for new geothermal projects ranged
from 6 tp 8 cents per kilowatt hour according to a 2006 report, including the
production tax credit. (5) But, it should be noted that the cost for individual
geothermal projects can vary significantly based upon a series of factors discussed
below, and that costs for all power projects change over time with economic
conditions.
"However, it must be remembered that a major impact on geothermal power cost is
the local, regional, national, and global competition for commodities such as steel,
cement, and construction equipment. Geothermal power is competing against other
renewable and non-renewable power development, building construction, road and
infrastructure improvements, and all other projects that use the same commodities and
services. Until equipment and plant inventories rise to meet the increase in demand

46
for these commodities and services, project developers can expect the costs to rise
well above the background inflation level." (6)
Moreover price of Geothermal power does not fluctuate like price of oil and gas.
Geothermal energy acts as a price stabilizer that offsets U.S. dependence upon highly
volatile fossil fuel power markets. This is because geothermal power does not need
outside fuel to operate—geothermal relies on a constant source of free fuel.
Geothermal is capital intensive, thus all of the fuel is essentially paid for upfront.
However, once the power project is built, most of its power production costs are
known and few market parameters can modify them.
6.4 Factors that influence the cost of Geothermal
power plant
There are many factors that influence the cost of a geothermal power plant. In
general, geothermal plants are affected by the cost of steel, other metals and labor,
which are universal to the power industry. However, drilling costs may vary as well.
Geothermal projects are site-specific, thus the costs to connect to the electric grid vary
from project to project. Also, whether the project is the first in a particular area or
reservoir impacts both risks and costs. The acquisition and leasing of land also varies,
because to fully explore a geothermal resource a developer is required to lease the
rights to 2,000 acres or more. Challenges to leasing and permitting vary from project
to project; especially on federal lands. These factors include:
 Size of the plant
 Power plant technology
 Knowledge of the resource
 Temperature of the resource
 Chemistry of the geothermal water
 Resource depth and permeability
 Environmental policies
 Tax incentives
 Markets
 Financing options and cost
 Time delays

47
6.5 Cost of geothermal energy compare to the cost of
fossil fuel in the future
Costs for geothermal generation at some facilities have decreased to half the
original price per kilowatt hour of power in 1980 , compared to when the first
independent geothermal plants were installed. (10) Their cost falling at a faster rate
than coal over this same period. The current price for extensions onto existing projects
can be competitive with polluting coal-fired plants. While geothermal’s costs have
steadily decreased throughout the years, those of natural gas have increased, often
experiencing boom and bust type cycles that can negatively impact the economy.
California Energy Commission (CEC) analysis examines what it estimates are the
cost of different technologies based upon “levelized cost” which includes both capital
and fuel costs. Their study places geothermal energy at a lower levelized cost
($/MWh) than many other types of merchant owned power plants including: Natural
Gas Combined-Cycle, Wind, Biomass Combustion, Nuclear, Solar Thermal, and
Photovoltaic. (11)
Many industry experts agree that geothermal is one of only a few alternative
technologies that will compete economically with polluting technologies in the near
term—even without considering the additional benefits of geothermal production

48
CHAPTER-7
APPLICATIONS OF GEOTHERMAL
ENERGY
7.1 Introduction
With growing concern over rising energy costs and the environmental impacts
of supplying our energy needs, there is a great need to find economical and
environmentally sound energy alternatives. However, amidst the push to expand
renewable energies, one option that is rarely discussed is geothermal energy. One
reason that geothermal is often overlooked is because of the lack of understanding
how the technology works and a view that it is new and unproven. Actually, people
have used geothermal energy for over 10,000 years with the first recorded use when
Paleo-Indians settled around hot springs and used them as a source for warmth,
cleansing, and healing. 3 More advanced geothermal technology, such as geothermal
heat pumps, have been used to heat and cool buildings since the late 1940s and today
more than 50,000 units are installed every year.
Geothermal energy has significant potential as part of a renewable energy mix.
Geothermal energy can be clean and reliable, and it is locally available in many
areas.5
Methods to utilize geothermal energy depend largely on local heat distributions. The
factors that most influence the applications of geothermal energy are accessibility,
water or steam temperatures, and geothermal reservoir permeability and porosity. 9
Applications can be broadly divided into three categories: power generation, direct
heating, and ground source heating and cooling.
7.2 Geothermal Applications
Geothermal power generation requires heat flow temperatures ranging from
212 °F to 482 °F. Unlike intermittent power sources like solar and wind, geothermal
energy is a reliable and consistent source of energy with an average system

49
availability of 95 percent. Three categories of geothermal power generation are direct
steam, flash, and binary plants.
Fig-7.1:Pie chart of Geothermal Application
Direct steam plants require very high-temperature geothermal resources that are
greater than 455 °F. These types of plants are both the rarest and most valuable
because they have access to such high ground temperatures. The plants use high
temperature steam via production wells that are 3,280 feet to two and an half miles
underground. The steam in these systems is processed so that particulates and non-
essential fluids are removed and then it is piped to operate turbines that generate
electricity.
Flash-steam power plants are much more common and require resource temperatures
ranging from 300-700 °F. These systems primarily use highly pressurized hot water
that is transported to the surface via production wells reaching depths of two and a
half miles underground. The pressure of this water is reduced during transport, a
fraction of the water “flashes” or explosively boils into steam, and then this steam is
moved to a turbine to generate electricity. Water that does not flash into steam is
channelled back to the reservoir to maintain pressure and productivity.
Binary-cycle power plants can utilize geothermal reservoirs ranging from 212 °F to
302 °F. Using these systems, hot water is circulated through a heat exchanger which
heats a secondary working fluid that turns to vapour at a lower temperature than
water. Closed-loop systems use vapour to spin turbines to generate electricity. The

50
vapor then condenses back into liquid and is transported back to the heat exchanger
where the process begins again.
7.2.1 Geothermal Direct-Heating
Even in areas with geothermal resources that are insufficient for power
generation, such resources can still be used for direct-heating applications. Direct-
heating use of geothermal energy involves utilizing low to moderate temperature
resources (68 °F to 302 °F) to provide heat directly to a wide variety of residential,
industrial, and commercial applications. Examples include homes, offices,
commercial greenhouses, fish farms, food processing facilities, and mining operations
as well as other direct-heating applications like melting snow on sidewalks.
Geothermal direct-heating can produce cost savings up to 80 percent over
conventional fossil fuels. Direct heating using geothermal energy is fairly widespread
and is expanding.
7.2.2Geothermal Ground Source Heating and Cooling
The most viable means of accessing geothermal resources is via geothermal
heat pumps (GHPs). A GHP is an electric heat pump that transfers natural heating and
cooling from the ground to regulate building air temperature. One of the largest
advantages of GHPs is that just a few feet from the surface, ground temperature stays
fairly constant (50 °F to 60 °F), whereas above surface temperature can vary
significantly. A relatively stable ground temperature means that GHPs can be installed
almost anywhere, achieving efficiencies of 300-600 percent during cold winters and
hot summers. These efficiency levels are many times greater than other heating
systems. High efficiency traditional furnaces or boilers range between 90-97 percent
annual fuel utilization efficiency.
In the winter, a GHP works by utilizing the ground temperature that is warmer than
the air above it to heat buildings; in the summer, the opposite process can be used to
cool buildings where the heat from indoor air is transferred out of the house into the
cooler ground. Basically, the ground can be thought of as a heat source during the
cold of winter and a heat sink during hot summer months.
Heated and cooled air produced by a GHP system is delivered through the house’s
ductwork in the same manner as conventional systems. A box called an air handler

51
includes an indoor coil and fan that circulates house air through the heat pump for
heating or cooling. Similar to a standard air conditioner, the air handler has a large
blower and filter.
It should be noted that the initial purchase and installation price of a residential GHP
is significantly higher than a comparable gas furnace or central airconditioning unit.
However, GHPs are much more efficient and overtime they will save the homeowner
money in operating and maintenance costs. On average, the initial investment in a
geothermal system is paid back through energy cost savings over a two to ten years
period. The average system life is twenty-five years for inside components and more
than fifty years for the ground loop system.
7.2.3 Geothermal Energy in Farming
Some of the common uses of geothermal energy are amongst farmers, who use
geothermal energy to heat their greenhouses.
In Tuscany, Italy, farmers have used water heated by geothermal energy for hundreds
of years to grow vegetables in the winter. Hungary is also a major user of geothermal
energy, where eighty percent of the energy demand from vegetables growers is met
using geothermal energy technology.Geothermal energy is also used in fish farms.
The warm water spurs the growth of animals ranging from alligators, shellfish,
tropical fish, amphibians to catfish and trout. Fish farmers from Oregon, Idaho, China,
Japan, and even Iceland use geothermal energy.
7.2.4 Geothermal Energy in Industry
Industry is another consumer of geothermal energy. Its uses vary from drying
fruits, drying vegetables, drying wood, and dying wool to extracting gold and silver
from ore. Check out this cool graphic from the state of California’s energy
almanac for the varying temperatures needed for a variety of industrial geothermal
energy uses.

52
7.3 Geothermal Heat Pump System Parts and Types
There are three basic parts to a GHP system: the geothermal connection, the
heat pump, and the heat distribution system. The geothermal connection is a system of
pipes (the “loop”) that in most systems are buried either horizontally or vertically
underground near the connected building. Within the geothermal loop, a solution
consisting of water, or a water/antifreeze mixture circulates and absorbs or releases
heat to the underground soil depending on the difference between temperatures above
and below ground. The purpose of the geothermal heat pump is to remove heat from
the circulating fluid in the connection, condense it, and move it to the building. The
opposite process occurs for cooling. Finally, the geothermal heat distribution system
is generally made up of conventional ductwork to carry heated or cooled air within a
building.
There are two main types of ground source geothermal systems: open-loop systems
and closed loop systems. Closed loop systems can be further divided into horizontal,
vertical, or water-based installations.
7.3.1 Horizontal closed loop system
A horizontal closed loop system is the most common set up and generally the
most economical option for residential applications (especially for new construction
with adequate land available). These systems include high-density polyethylene
piping that is buried in trenches 4-6 feet underground in a horizontal pattern.

53
Fig-7.2:Horizontal closed loop system
The pipes are filled with an antifreeze and water mixture that acts as a heat exchanger
that extracts heat from the ground to the building in the winter, and it takes heat from
the building and transfers it to the cooler ground in the summer
7.3.2 Vertical closed loop systems
Vertical closed loop systems are typically most appropriate for commercial
buildings or other large buildings (e.g., schools) where land space is limited or areas
where soil is too shallow to dig trenches. Vertical systems are made of piping that
extend 100-400 feet deep underground and are combined with a U-bend to form a
loop

54
Fig-7.3:Vertical closed loop system
7.3.3 Pond/lake closed loop systems
Closed loop systems that are connected to a pond or lake can be the most
economically viable option when the site has a sufficient body of water. This system
involves running a pipe-system underground (e.g., eight feet deep) between the
building and under the water in a coiled pattern that helps prevent freezing during the
winter.
Fig-7.4:Pond/lake closed loop systems

55
7.3.3.1 Open loop systems
Open loop systems use a water source (groundwater or a surface body of
water) as the source of heat exchange. This option is most appropriate only when
there is a sufficient source of clean water and water codes and regulations related to
groundwater discharge are met.
Fig-7.5:Open loop system
The water moves through the GHP system and then returns through a well, recharge
well, or surface discharge. 30 Open loop systems can have negative environmental
impacts such as warming surface waters and lowering water oxygen levels.
7.3.4 Geothermal Heat Pump Pros and Cons
There are several benefits and positive attributes of geothermal heat pumps that
make them attractive alternative or supplemental heating and cooling systems. There
are also several potential drawbacks and considerations that should be addressed
before deciding to install a GHP.
Geothermal Heat Pump Pros:
• 300-600% energy efficient
• 25-50% less electricity consumption compared to other types of systems
• Less expensive to operate and maintain compared to conventional heating and air

56
• conditioning systems with annual energy savings between 30-60% per year
• Reduced air emissions (e.g., pollution) by 44% as compared to conventional
airsource heat pumps and 72% in comparison to standard electric heating with
airconditioning systems
• Can be scaled for use in residential and commercial buildings of all sizes
• Flexible design allows for new and retrofit installations
• System takes up less space compared to standard systems
• Quiet and very little noise compared to conventional air conditioners
• GHPs can maintain 50% relative indoor humidity and are appropriate for zone
• heating and cooling
• System life for a GHP is generally greater than 20 years and underground piping
• generally warrantied between 25-50 years.
Geothermal Heat Pump Cons:
• Initial purchase and installation of GHPs is generally more expensive than
conventional
heating and cooling systems
• Potential negative environmental effects if installed or operated improperly
• Groundwater/environmental contamination in the event of a pipe leak.
As was mentioned earlier, GHPs can be installed almost anywhere because of
relatively constant ground temperatures. However, this is not to say that a GHP can be
installed without any planning. Geology, hydrology, and land availability are all
factors that should be evaluated before installing a GHP. Regarding geology, oil and
rock composition and properties should be considered when designing a ground loop
system because they can influence heat transfer rates. Surface water depth, volume,
and quality are all factors that influence how bodies of surface water can be used as an
open-loop system’s water source or as a container for piping in a closed-loop.
Regarding land availability, the amount, layout, and landscaping of the land where the
GHP system will be installed should also be considered when designing a system.
Because of the specialized knowledge, equipment, and skills required to properly
install a GHP system, it is recommended that homeowners not try to install a GHP on
their own, but instead work with a certified and experienced installer. Professional
installers can be located by contacting the local utility company, the International

57
Ground Source Heat Pump Association, or the Geothermal Heat Pump Consortium;
all can provide a listing of qualified installers in a local area.

58
CHAPTER-8
CONCLUSION
During a time of volatile energy costs and growing concerns over the effects
of fossil fuel use, geothermal energy has great potential as a resource that is both
environmentally and economically viable. Geothermal resources can be used in a
wide variety of applications from melting snow on sidewalks to generating electricity.
Geothermal heat pumps are a high efficiency means of heating and cooling buildings.
With careful planning, they can be installed almost anywhere and can provide
homeowners with significant annual energy savings. Although geothermal energy is
not the sole renewable energy solution, it can play a significant role in helping to meet
the heating, cooling, and energy needs of communities
The opportunities for geothermal power to play a much larger role in overall energy
production in the future require technical innovation, reduced startup costs, public
education, and a level economic and regulatory playing field with other energy
technologies. North American output could rise to 11,700 MW with existing
technology and 25,390 MW with enhanced technology under development by joint
government-industry programs.
Most of the easily located geothermal systems, those with hot springs, fumaroles, and
geysers at the surface, are already known and many have been developed. In order to
locate and characterize hidden geothermal systems that do not reach the surface, new
approaches to exploration are needed. The high economic risk of drilling has limited
geothermal exploration in recent years. Significant growth in geothermal generating
capacity during the next decade will rely on the discovery and production of several
new water-dominated geo-thermal fields as well as drilling techniques for reaching
them.
Researchers believe that the economic risk of exploratory drilling will be reduced
through the development of new core hole evaluation technologies. Core drilling
provides a set of rock samples and fine temperature-gradient information. It will be
necessary to develop the methodology and equipment to conduct reservoir testing and

59
evaluation during core drilling in order to take full advantage of the lower cost of core
drilling.
Steam and hot water reservoirs are just a small part of the geothermal resource. The
Earth's magma and hot dry rock will provide cheap, clean, and almost unlimited
energy once technology can tap into them. One future promising new geothermal
technology known as Hot Dry Rock (HDR) geothermal is designed to be able to tap
into much deeper geothermal resources than current technologies permit, thus
allowing geothermal energy to be used for low cost, renewable electricity generation
anywhere in the world. However, the technology to drill deep enough boreholes
(approximately 4 to 10 miles into the earth's surface) does not yet exist at a low
enough cost, and is a subject of current research and development by companies such
as Earthworm Tunnelling.
The economics of geothermal power can be further improved through co-production
of goods and services from high-temperature geothermal brine. Examples of this
include zinc and silica, which can be recovered from geothermal brine in conjunction
with electrical generation stations. Large quantities of distilled water, which is
currently costly to produce, is also a convenient by-product of the generation of
geothermal power. Geothermal power production can also be co-located with
pollution remediation equipment in the context of cleaning sub-surface spills or other
contaminations.
Hot, dry rock (HDR) is widespread and offers new resources in areas where geyser
activity is un known .Direct low-temperature heat transfer for home systems is
practical as long as low maintenance is designed into the system .Geothermal energy
is limited in extent as extracting the heat usually exceeds the replenishment rate.
Sources of high temperature water or steam are limited and the cost of extraction,
maintenance, and operation will remain high in comparison with other sources of
energy. Geothermal energy likely to remain at 1% of world energy.

60
REFERENCES
[1.] Mukul Chandra Bora.” Geothermal Energy : Indian scenario”,
September 2010
[2.] Alyssa Kagel etal.,” Promoting Geothermal Energy: Air Emissions
Comparison and Externality Analysis”,20̊̊̊0̊̊̊5
[3.] Anita Sowa-Watrak,” The Criteria for Suitable Location of
Geothermal plant”
[4.] Study mafia (https://studymafia.org/geothermal-energy-seminar-and-ppt-
with-pdf-report/)
[5.] Greentechmedia (https://www.greentechmedia.com/articles/read/the-
status-of-global-geothermal-power-development#gs.1YVr2T4)
[6.] World Energy Council (https://www.worldenergy.org/wp-
content/uploads/2017/03/WEResources_Geothermal_2016.pdf)
[7.] Wikipedia(https://en.wikipedia.org/wiki/Geothermal_energy#History)
[8.] Petrowiki(https://petrowiki.org/Convertinggeothermal_to_electric_power)
[9.] Geothermal Energy Association(http://geo-
energy.org/geo_basics_plant_cost.aspx)
[10.] Dovetailgeothermal(https://www.ourenergypolicy.org/wpcontent/uploads/
2013/09/DovetailGeothermal0911.pdf)

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