BALASORE COLLEGE OF ENGINEERING &

TECHNOLOGY

Sergarh,Balasore,756001

ENHANCED GEOTHERMAL POWER PLANT

Submitted by: PANKAJ KUMAR NAYAK

Branch: ELECTRICAL ENGINEERING Roll no: 11-EE-10

Regd. no: 1101225025

ABSTARACT

The paper gives an overview of the existing power plant technology. It addresses various problems that have

been encountered, and outlines countermeasures that have been applied. Two main types o f geothermal power p lants are

common, the condensing power plant, using fluid from reservoirs with temperatures in the range 200–320°C, and the binary

f luid power plant using temperatures as low as 120°C. Also featured are the principal advantages appropriate to the utilization o f

geothermal res ources for production o f electr icity.

T he paper moreover touches upon some of the advantages accruable from the integrated use of geothermal resources

(using the same resource for electricity production in cascade or parallel with production of hot water for alternative uses), taking

hybr id convers ion as a case in po int .

Also featured is a worldwide overview of the geothermal power plants by Bertani (under the auspices of I GA in 2013).

T he survey categorizes the power plants by country, type of power conversion system used, and its ro le with respect to the

country’s total electricity generation and total power demand. Also addressed is the actual geothermal electric power generat ion

per continent relative to actual total installed plant capacity. Finally the survey features the effect of resource temperature on the

power generation dens ity.

Environmental abatement measures, such as re-injection of the spent (denuded of most of its thermal energy) geotherma l f lu id

and methods of minimizing atmospheric contamination by CO2 and H2S gases are also outlined, and so are 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 thankful to Mr.S.N. MOHANTY,H.O.D of department of

Electrical Engineering, and also thankful to 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 output and 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 electricity production.

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 +300C per km dug into the earth. Therefore, if one digs

20,000 feet the temperature will be about 1900C above the

surface temperature. This difference will 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 400C/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.

Availability of Geothermal Energy :

Classification of 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: The geothermal fluid is mixture of water and steam at

temperature less than 150 C. The geothermal fluid cycle is

different from 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.

Application of 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

throughout the 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.

Overview Of 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.

Overview of 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 explanation of practical use

http://www.acmehowto.com/howto/appliance/refrigerator/overview.htm

University of Nevada at Reno Desert Research

Institute http://www.bnl.gov/est/MEA.htm Brookhaven

Laboratories

http://geothermal.inel.gov/ INEEL http://www-esd.lbl.gov/ER/geothermal.html Lawrence

Livermore Labs

http://www.sandia.gov/geothermal/ Sandia National Labs

http://www.nrel.gov/geothermal/ National Renewable

Energy Labs http://www.eere.energy.gov/geothermal/webresources.

html More Resources

____________________________________________________________________________________________

rredc.nrel.gov/www.dieoff.org. Site devoted to 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

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