Enhanced geothermal system

BALASORE COLLEGE OF ENGINEERING &
TECHNOLOGY
Sergarh,Balasore,756001
ENHANCEDGEOTHERMALPOWERPLANT
Submitted by: PANKAJ KUMAR NAYAK

Branch: ELECTRICAL ENGINEERING
Roll no: 11-EE-10
Regd. no: 1101225025
ABSTARACT
The paper givesanoverviewof theexisting power plant technology.Itaddresses variousproblems that have
beenencountered, andoutlinescountermeasuresthat havebeen applied.Twomain types of geothermal power plants are
common,thecondensing power plant, using fluid fromreservoirswithtemperaturesintherange 200–320°C, and the binary
fluid power plant usingtemperatures aslow as120°C. Alsofeatured aretheprincipal advantagesappropriate tothe utilization of
geothermal resources for production of electricity.
The papermoreovertouchesuponsome of the advantagesaccruable fromthe integrateduseofgeothermal resources
(usingthesame resource forelectricity production incascade or parallel withproduction ofhot water foralternativeuses), taking
hybrid conversion as a case in point.
Also featured isa worldwideoverview of the geothermal power plants by Bertani(undertheauspicesof IGA in 2013).
The survey categorizes the power plants by country,typeofpowerconversion systemused, and its role with respect to the
country’s total electricity generationandtotal power demand.Alsoaddressed isthe actual geothermal electric power generat ion
per continentrelative to actualtotal installedplantcapacity.Finally the survey featurestheeffectofresource temperature on the
power generation density.
Environmental abatement measures,suchasre-injection of thespent (denudedofmostofits thermalenergy) geothermal fluid
and methodsofminimizing atmosphericcontamination by CO2 andH2S gases are alsooutlined, andsoare the main associated
technical problems.

ACKNOWLEDGEMENT
I take this opportunity to express my hearty thanks to all
those who individually as well as collectively helped me in the successful
completion of this report.
I am thankfulto Mr.S.N. MOHANTY,H.O.D of department of
Electrical Engineering, and also thankfulto all the faculties of Electrical
Engineering of Balasore College Of Engineering & Technology for
having supported me to carry out this seminar report and for their
constant advice.
I also acknowledge the continuous encouragement rendered by my
friends.
PANKAJ KUMAR NAYAK
Regd. No. :1101225025
Semester:7th
Branch:Electrical Engineering

CONTENTS :
 Introduction
 History
 Sources/ Origins of Geothermal energy
 Classification of Geothermal Power
plant
 Application of Geothermal energy
 Equipment required for Electric power
generation by Enhanced Geothermal
process
 Working principle of Enhanced
Geothermal system(EGS)
 Advantages and Disadvantages
 Overview of Geothermal energy in
World
 Overview of Geothermal energy in India
 Conclusion
Reference

INTRODUCTION:
Geothermal energy is the heat contained within the Earth and it
can be used to generate electricity by utilizing two main types of
geothermal resources. so 1st
one is Hydrothermal resources use
naturally occurring hot water or stream circulating through
permeable rock and 2nd
one is Hot rock resources produce super
heated water or stream by artificially circulating fluid through
the rock. Geothermal energy is the energy stored in the form of
heat below the earth’s surface. Its potential is limitless in human
terms and its energy is comparable to the sun. Geothermal heat
and water have been used for thousands of years. The Romans,
Chinese and Native Americans used hot mineral springs for
bathing, cooking and for therapeutic purposes.
Today geothermal water is used in many applications such
as district heating, systems which provide steam or hot water to
multiple units, as well as for heating and cooling of individual
buildings, including offices, shops and residential houses, by
using geothermal heat pumps. Moreover, it has industrial
potential for raising plants in greenhouses, drying crops,
heating water at fish farms and other industrial processes.
For close to 100 years geothermal energy has also been used
for electricity generation. Today, so called Enhanced
Geothermal Systems (EGS, also known as Hot Dry Rock),
enable the exploitation of the Earth’s heat for producing
electricity without having natural water resources. To extract
energy from hot impermeable rock, water is injected from the
surface into boreholes in order to widen them and create some
fractures in the hot rock. Flowing through these holes, the water

heats up and, when it returns to the surface, it is used for
generating electricity.
Clean, renewable, constant and available worldwide,
geothermal energy is already being used in a large number of
thermal and electric power plants.
Definitions of Geothermal:
So Geothermal means Heat produce in inner-earth surface is known as
Geothermal.

HISTORY :
 First electricity (20kW) from geothermal produced from natural
steam in Larderello, Italy in 1904.
 New Zealand’s north island gets 6% of its electricity from
geothermal energy.
 1920: Test boring in Niland CA.
 1922: Electricity generation in The Geysers.
 1950: 95°F, 220kW generating plant in Katanga.
 The Geysers CA expanded to 600MW in 1975.
History says that the first use of geothermal energy occurred more than
10,000 years ago in North America by American Paleo-Indians. People
used water from hot springs for cooking, bathing and cleaning. The first
industrial use began near Pisa, Italy in late 18th century. Steam coming
from natural vents (and from drilled holes) was used to extract boric
acid from the hot pools that are now known as the Larderello fields. In
1904, Italian scientist Piero Ginori Conti invented the first geothermal
electric power plant in which steam was used to generate the power.
With the above experiment, the first geothermal plant in USA started in
1922 with a capacity of 250 kilowatts. It produced little outputand due
to technical glitch had to be shut down. However, in 1946 first ground-
source geothermal heat pump installed at Commonwealth Building in
Portland, Oregon. During the 1960′s, pacific gas and electric began
operation of first large scale in San Francisco, producing 11 megawatts.
Today there are more than 60 geothermal power plants operating in
USA at 18 sites across the country.
In 1973, when oil crisis began many countries began looking for
renewable energy sources and by 1980 (GHP) started gaining
popularity in order to reduce heating and cooling costs. As effect of
climate change started showing results, governments of various
countries joined hands to fight against it, for which Kyoto Protocol was
signed in Japan in 1997, laid out emission targets for rich countries and
required that they transfer funds and technology to developing

countries, 184 countries have ratified it. Geothermal power today
supplies less than 1% of the world’s energy in 2012 needs but it is
expected to supply 10-20% of world’s energy requirement by 2050.
Geothermal power plants today are operating in about 20 countries
which are actively visited by earthquakes and volcanoes.
EGS IMPLEMENTED COUNTRY:

Source/Origins of Geothermal energy:
Heat stems from radioactive disintegrations of atomic nuclei [Sorensen,
2000], initial cooling from agglomeration in planet formation, and other
various processes Hot spots occur where strong convective magma
circulation is occurring, usually near continental plate boundaries and
mountainous regions Hot dry rock, the most common type, retains
convective heat Storage in a developed area may be depleted in 50
years.
Sources of Geothermal energy:
Sources of Geothermal Energy in western country:

• 70% of Geothermal energy comes from the decay of
radioactive nuclei with long half lives that are embedded
within the Earth.
• Some energy is from residual heat left over from Earths
formation.
• The rest of the energy comes from meteorite impacts.

Different Geothermal Energy Sources:
1. Hot Water Reservoirs: As the name implies these are
reservoirs of hot underground water. There is a large
amount of them in the US, but they are more suited for
space heating than for electricityproduction.
2. Natural Steam Reservoirs: In this case a hole dug into
the ground can cause steam to come to the surface. This
type of resource is rare in the USA and Other country.
3. Geopressured Reservoirs: In this type of reserve, brine
completely saturated with natural gas in stored under
pressure from the weight of overlying rock. This type of
resource can be used for both heat and for natural gas.
4. Normal Geothermal Gradient Reservoirs: At any place
on the planet, there is a normal temperature gradient of
+300
C per km dug into the earth. Therefore, if one digs
20,000 feet the temperature will be about 1900
C above the
surface temperature. This differencewill be enough to
produce electricity. However, no useful and economical
technology has been developed to extracted this large
source of energy.
5. Hot Dry Rock Reservoirs: This type of condition exists
in 5% of the US. It is similar to Normal Geothermal
Gradient, but the gradient is 400
C/km dug underground.

6. Molten Magma Reservoirs: No technology exists to tap
into the heat reserves stored in magma. The best sources
for this in the US are in Alaska and Hawaii.
Availabilityof GeothermalEnergy:

Classificationof Geothermal Power Plants :
Geothermal Power Plants are of several types. They are
classified on basis of
• Geothermal fluid used
• Thermodynamic cycle adopted
1. STEAM GEOTHERMAL POWER PLANT:
It is called vapour dominated geothermal power plant.
Geothermal fluid is steam.
2. PETRO THERMAL GEOTHERMAL POWER
PLANT:
It is also called Hot Dry Rock geothermal power plant. Thermal
energy in hot dry geological rock is extracted by circulating
water through artificial fracture in hot dry rock. Steam turbine
is used as prime mover.

3. FLASHED STEAM GEOTHERMAL POWER
PLANT:
It is a type of Liquid Dominated geothermal power plant.
Production well produces mixture of water and steam at
temperature more than 180 C and with low content of dissolved
minerals. Steam turbine is the prime mover. Geothermal fluid
is flashed to obtain steam.
4. BINARY LIQUID DOMINATED GEOTHERMAL POWER
PLANT:
Thegeothermal fluid is mixture of water and steam at
temperature less than 150 C. The geothermal fluid cycle is
differentfrom the working fluid cycle. The geothermal heat is
exchanged with the working fluid of low boiling point in a heat
exchanger gas turbine drives the generator shaft.

5. BINARY CYCLE GEOTHERMAL POWER
PLANT WITH HOT BRlNE:
When geothermal fluid is liquid with high mineral content,
binary cycle similar to (4) is preferred.
6. TOTAL FLOW GEOTHERMAL POWER PLANT:
The entire geothermal fluid is passed through the special
turbine. Such system is used when the geothermal fluid has very
high content of mud, dissolved minerals etc.

Applicationof Geothermal Energy :
• Space heating
• Air conditioning
• Industrial processes
• Drying
• Greenhouses
• Agriculture
• Hot water
• Resorts and pools
• Melting snow

Equipment Required for Electric Power
Generation Using Geothermal Energy:
The Equipment required in geothermal plant are as follow……
1.Turbine
2.Generator
3.Condenser
4.Cooling tower system
5.Condenser pumping system
6.Heat exchanger
7.Gas evacuation system
8.Pipeline system
9. Automatic control and communication system
Turbine :
The rate and seriousness of scaling in the turbine are directly related to
the steam cleanliness, i.e. the quantity and characteristics of separator
“carry-over“. Thus the operation and efficiency of the separator are of
great importance to trouble free turbine operation. Prolonged operation
of the power plant off-design point also plays a significant role.
Generator :
It must be pointed out here that high-temperature steam contains a
significant amount of carbon dioxide CO2 and some hydrogen sulphite
H2S and the atmosphere in geothermal areas is thus permeated by these
gases. All electrical equipment and apparatus contains a lot of cuprous
or silver components, which are highly susceptible to sulphite corrosion
and thus have to be kept in an H2S free environment. This is achieved by
filtering the air entering the ventilation system and maintaining slight
overpressure in the control room and electrical control centres. The
power generator is either cooled by nitrogen gas or atmospheric air that
has been cleaned of H2S by passage through special active carbon filter
banks.
Condenser :

The condenser may be either water or air cooled . The calculations for
the condenser are roughly the same in both cases, as the cooling fluid
(air or water) is very close to linear. Station 1 is the working fluid
coming from the regenerator (or turbine in the case of a non-
regenerated cycle). Station 2 is the condensed fluid, normally saturated
liquid with little or no sub-cooling. Station c1 is the entry of the cooling
fluid, station c2 the outlet. The condenser is nothing but a heat
exchanger between the hot vapor from the regenerator/turbine and the
cooling working fluid of the cycle. It has to be observed that the
temperature of the hot fluid is higher than the one of the cold fluid
throughoutthe condenser.
Cooling Tower system :
The modern forced ventilation cooling towers are typically of
wooden/plastic construction comprising several parallel cooling cells
erected on top of a lined concrete condensate pond. The ventilation fans
are normally vertical, reversible flow type and the cooling water
pumped onto a platform at the top of the tower fitted with a large
number of nozzles, through which the hot condensate drips in
counterflow
to the airflow onto and through the filling material in the tower and
thence into the condensate pond, whence the cooled condensate is
sucked by the condenser vacuum back into the condenser. To minimise
scaling and corrosion effects the condensate is neutralised through pH

control, principally via addition of sodium carbonate. Three types of
problems are found to be associated with the cooling towers, i.e.
• Icing problems in cold areas.
• Sand blown onto the tower in sandy and arid areas.
• Clogging up by sulphitephylic bacteria.
Condenser Pumping System :
The condensate pumps must, as recounted previously, be made of highly
corrosion resistant materials, and have high suction head capabilities.
They are mostly trouble free in operation. The condensate pipes must
also be made of highly corrosion resistant materials and all joints
efficiently sealed to keep atmospheric air ingress to a minimum, bearing
in mind that such pipes are all in a vacuum environment. Any air
leakage increases the load on the gas evacuation system and thus the
ancillary power consumption of the power plant.
Heat Exchanger :
In high-temperature power generation applications heat exchangers are
generally not used on the well fluid. Their use is generally confined to
ancillary uses such as heating, etc. using the dry steam. In cogeneration
plants such as the simultaneous production of hot water and electricity,
their use is universal. The exhaust from a back pressure turbine or tap-
off steam from a process turbine is passed as primary fluid through
either a plate or a tube and shell type heat exchanger. The plate type
heat exchanger was much in favour in cogeneration plants in the
seventies to nineties because of their compactness and high efficiency.
They were, however, found to be rather heavy in maintenance. The
second drawback was that the high corrosion resistance plate materials
required were only able to withstand a relatively moderate pressure
difference between primary and secondary heat exchanger media.
Thirdly the plate seals tended to degenerate fairly fast and stick
tenaciously to the plates making removal difficult without damaging the
seals. The seals that were needed to withstand the required temperature
and pressure were also pricy and not always in stock with the suppliers.
This has led most plant operators to change over to and new plant
designers to select the shell and tube configurations, which demand less

maintenance and are easily cleaned than the plate type though requiring
more room.
In low-temperature binary power plants shell and tube heat exchangers
are used to transfer the heat from the geothermal primary fluid to the
secondary (binary) fluid. They are also used as condensers/and or
regenerators in the secondary system. In supercritical geothermal power
generation situation it is foreseen that shell and tube heat exchangers
will be used to transfer the thermal energy of the supercritical fluid to
the production of clean steam to power the envisaged power conversion
system.
Gas evacuation system :
As previously stated the geothermal steam contains a significant
quantity of non-condensable gas (NCG) or some 0.5% to 10% by weight
of steam in the very worst case. To provide and maintain sufficient
vacuum in the condenser, the NCG plus any atmospheric air leakage
into the condenser must be forcibly exhausted. The following methods
are typically adopted, viz.:
• The use of a single or two stage steam ejectors, economical for NCG
content less than 1.5% by weight of steam.
• The use of mechanical gas pumps, such as liquid ring vacuum pumps,
which are economical for high concentration of NCG.

• The use of hybrid systems incorporating methods 1 and 2 in series. The
advantages of the ejector systems are the low maintenance, and high
operational security of such systems. The disadvantage is the significant
pressure steam consumption, which otherwise would be available for
power production.
Pipeline System :
High density polyethylene (HDPE) pipe is the geothermal industry’s
standard piping material. The specific pipe used is a PE3408 HDPE
with a minimum cell classification of 345464C per ASTM D-3035.
Typically, a DR 11 (160 psi) rating is used for u-bends and header pipe
diameters two inches and smaller; and a minimum of DR 15.5 (110 psi)
is used for header pipe diameters greater than two inches. Pipe
produced specifically for the geothermal industry generally carries a 50-
year or longer warranty and has a life expectancy of over 100 years.
Advantages to using HDPE pipe include the following characteristics:
toughness, durability, and chemical and corrosion resistance. Another
advantage of HDPE pipe is that it requires no mechanical or glued
fittings that could corrode or fail. All joints are permanently joined
(welded) with heat fusion, providing a leak proof joint when properly
joined. The smooth wall of this pipe accommodates low-pressure losses.
Automatic control and communication system :
Modern power plants are fitted with a complex of automatic control
apparatus, computers and various forms of communication hardware.
These all have components of silver and cuprous compounds that are
extremely sensitive to H2S corrosion. They are therefore housed inside
“clean enclosures”, i.e. airtight enclosures that are supplied with
atmospheric air under pressure higher than that of the ambient
atmospheric one and specially scrubbed of H2S. Entrance and exit from
this enclosure is through a clean air blow-through antechamber to
prevent H2S ingress via those entering the enclosure. A more recent
design is to clean all the air in all control rooms by special filtration and
maintain overpressure. Most other current carrying cables and bus bars
are of aluminium to prevent H2S corrosion. Where copper cables are
used a field applied hot-tin coating is applied to all exposed ends.

Working Principle of EGS :
The most common current way of capturing the energy from geothermal
sources is to tap into naturally occurring "hydrothermal convection"
systems where cooler water seeps into Earth's crust, is heated up, and
then rises to the surface. When heated water is forced to the surface, it is
a relatively simple matter to capture that steam and use it to drive
electric generators. Geothermal power plants drill their own holes into
the rock to more effectively capture the steam.
There are three designs for geothermal power plants, all of which pull
hot water and steam from the ground, use it, and then return it as warm
water to prolong the life of the heat source. In the simplest design, the
steam goes directly through the turbine, then into a condenser where the
steam is condensed into water. In a second approach, very hot water is
depressurized or "flashed" into steam which can then be used to drive
the turbine.

In the third approach, called a binary system, the hot water is passed
through a heat exchanger, where it heats a second liquid such as
isobutene in a closed loop. The isobutene boils at a lower temperature
than water, so it is more easily converted into steam to run the turbine.
The three systems are shown in the diagrams below.
So the Over all working principle of EGS Is :

The simple Working Principle figure is shown below:

Advantages and Disadvantages:
Advantages:-
1) It is a renewable source of energy.
2) By far, it is non-polluting and environment friendly.
3) There is no wastage or generation of by-products.
4) Geothermal energy can be used directly. In ancient times, people
used this source of energy for heating homes, cooking, etc.
5) Maintenance cost of geothermal power plants is very less.
6) Geothermal power plants don't occupy too much space and thus help
in protecting natural environment.
7) Unlike solar energy, it is not dependent on the weather conditions.
Disadvantages:-
1) Only few sites have the potential of Geothermal Energy.
2) Most of the sites, where geothermal energy is produced, are far from
markets or cities, where it needs to be consumed.
3) Total generation potential of this source is too small.
4) There is always a danger of eruption of volcano.
5) Installation cost of steam power plant is very high.
6) There is no guarantee that the amount of energy which is produced
will justify the capital expenditure and operations costs.
7) It may release some harmful, poisonous gases that can escape
through the holes drilled during construction.

OverviewOf Geothermal Energy In The World :
World Wide Geothermal Uses and Potential :-

Graphical presentation Of Geothermal power Projects:
 By the end of 2014 the global geothermal market is expected to
operate 12,000 MW of geothermal capacity on-line.
 There are 11,766 MW of new capacity in early stages of development
or under construction in 70 countries and territories around the
world. Additionally, developers are actively engaged with and
exploring 27 GW of geothermal resources globally that could
potentially develop into power plants over the next decade.
 Countries such as Uganda, France, Tanzania, Chile, and Rwanda
have geothermal projects under construction or in the latter stages of
development and will have their first operational geothermal power
plants within the next few years.

Overviewof Geothermal energy in India :
In India the Geoplants are given below:
Puga Valley (J&K)
Tatapani (Chhattisgarh) (Work in progress)
Godavari Basin Manikaran (Himachal Pradesh)
Bakreshwar (West Bengal) (Work in progress)
Tuwa (Gujarat)
Unai (Maharashtra)
Jalgaon (Maharashtra) (Work in progress)
Total thermal installed capacity in MWt :203.0
Direct use in TJ/year :1,606.3
Direct use in GWh/year :446.2
Capacity factor : 0.25

Conclusion :
Environmental and social impacts from geothermal use are site and
technology specific and largely manageable. Overall, geothermal
technologies are environmentally advantageous because there is no
combustion process emitting carbon dioxide (CO2), with the only
direct emissions coming from the underground fluids in the reservoir.
Direct CO2 emissions for direct use applications are negligible and
EGS power plants are likely to be designed with zero direct emissions.
An array of renewable energy sources-geothermal, solar, water, and
wind-have the theoretical potential to deliver all the energy humanity
needs thousands of times over in a clean, renewable way, if only that
energy could be collected. Doing so efficiently would mean using a
combination of resources depending upon local conditions and
developing technology. Expensive to implement, once in place these
technologies could provide energy on a long-term basis for very little
cost. The four articles in this Discovery Guide series on renewable
energy explain many of the advantages and drawbacks of wind, solar,
biofuels, and geothermal. Another factor to consider is electricity usage
versus transportation usage. Regarding transportation only biofuels, in
the form of ethanol or biodiesel, can be directly used for transportation.
Other forms of renewables, which generate power in the form of
electricity, must be collected and stored in battery form to be used for
transportation, and current technology to do so is cumbersome and
expensive (the exception is subway and trolley systems, which can use
electricity through direct transmission).

Future Geothermal Electricity :
Stream 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 as soon as we develop the
technology to use them. In the meantime, because they're so abundant,
moderate-temperature sites running binary-cycle power plants will be
the most common electricity producers.
Before geothermal electricity can be considered a key element of the
U.S. energy infrastructure, it must become cost-competitive with
traditional forms of energy. The U.S. Department of Energy is working
with the geothermal industry to achieve $0.03 to $0.05 per kilowatt-
hour.

Reference :
http://www.eere.energy.gov/geothermal/Government
Lab
Good explanationof practical use
http://www.acmehowto.com/howto/appliance/refrigera
tor/overview.htm
Universityof Nevada at Reno DesertResearch
Institute
http://www.bnl.gov/est/MEA.htmBrookhaven
Laboratories
http://geothermal.inel.gov/INEEL
http://www-esd.lbl.gov/ER/geothermal.html Lawrence
LivermoreLabs
http://www.sandia.gov/geothermal/Sandia National
Labs
http://www.nrel.gov/geothermal/NationalRenewable
Energy Labs
http://www.eere.energy.gov/geothermal/webresources.
html More Resources
______________________________________________
______________________________________________
rredc.nrel.gov/www.dieoff.org. Site devotedto the
www.ferc.gov/ Federal Energy Regulatory
Commission solstice.crest.org/
dataweb.usbr.gov/html/powerplant_selection.html
http://www.eere.energy.gov/geothermal/history.htm
http://www.consrv.ca.gov/geothermal/index.htm

Enhanced geothermal system

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