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A seminar report On GEO THERMAL ENERGY Submitted to Jawaharlal Nehru Technological University, Kakinada In Partial Fulfillment of the Requirements for the Award of the Degree Of Bachelor of Technology In Mechanical Engineering By C.MADHURI LATHA (07481A0317) Under the esteemed guidance of Dr. A. Jawahar Babu, Ph.D Professor and Head of ME Department of Mechanical Engineering GUDLAVALLERU ENGINEERING COLLEGE SESHADRIRAO KNOWLEDE VILLAGE

Madhuri Seminar

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Page 1: Madhuri Seminar

A seminar report

On

GEO THERMAL ENERGY

Submitted to Jawaharlal Nehru Technological University, Kakinada

In Partial Fulfillment of the Requirements for the

Award of the Degree Of

Bachelor of Technology

In

Mechanical Engineering

By

C.MADHURI LATHA (07481A0317)

Under the esteemed guidance of

Dr. A. Jawahar Babu, Ph.D

Professor and Head of ME

Department of Mechanical Engineering

GUDLAVALLERU ENGINEERING COLLEGE

SESHADRIRAO KNOWLEDE VILLAGE

GUDLAVALLERU – 521356

2010 – 2011

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GUDLAVALLERU ENGINEERING COLLEGE: GUDLAVALLERU

SESHADRI RAO KNOWLEDGE VILLAGE

DEPARTMENT OF MECHANICAL ENGINEERING

CERTIFICATE

This is to certify that this seminar work entitled

“GEO THERMAL ENERGY”

Is a bonafide record of work done

By

C.MADHURI LATHA (07481A0317)

Under my guidance and supervision and submitted in partial fulfillment of the requirements for the award of Degree of Bachelor of Technology in Mechanical Engineering during the Year 2010–2011 by Jawaharlal Nehru Technological University, Kakinada.

Dr. A. JAWAHAR BABU, Dr. A. JAWAHAR BABU,

Seminar Guide. Head of Department,

Mechanical Engineering.

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ABSTRACT

In present day scenario, people are very much worried about POLLUTION (mainly

caused by non-renewable sources such as petroleum, diesel, coal etc), which is increasing

rapidly day by day. So, as to breathe easy, pollution should be avoided or reduced to some

extent in one way or the other. Besides pollution, the cost of non-renewable sources is

being cumulated. So, it is our turn to find alternative for these non-renewable energy

sources. This is an attempt to create an awareness regarding GEO-THERMAL ENERGY

and its applications in various fields, which is one among the alternative energy resources.

  The Earth’s crust is a bountiful source of energy and fossil fuels are only part of the

story. Heat or thermal energy is by far the more abundant resource. To put it in perspective,

the thermal energy in the uppermost six miles of the Earth’s crust amounts to 50,000 times

the energy of all oil and gas resources in the world! The word “geothermal” literally means

“Earth” plus “heat.” The geothermal resource is the world’s largest energy resource and has

been used by people for centuries. In addition, it is environmentally friendly. It is a

renewable resource and can be used in ways that respect rather than upset our planet’s

delicate environmental balance.

Geothermal power plants operating around the world are proof that the Earth’s

thermal energy is readily converted to electricity in geologically active areas. This also

deals the things concerning about geo-thermal power plant advantages and environmental

aspects.

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INTRODUCTION

Geothermal energy comes from the heat within the earth. The word "geothermal"

is derived from the Greek words geo, meaning earth," and thermal, meaning "heat."

People around the world use geothermal energy to produce electricity, to heat buildings

and for other purposes.

The earth's core lies almost 4,000 miles beneath the earth's surface. The double-

layered core is made up of very hot molten iron surrounding a solid iron center. Estimates

of the temperature of the core range from 5,000 to 11,000 degrees Fahrenheit (F). Heat is

continuously produced within the earth by the slow decay of radioactive particles that is

natural in all rocks.

Surrounding the earth's core is the mantle, thought to be partly rock and partly

magma. The mantle is about 1,800 miles thick. The crust is the outermost layer of the

earth, the land that forms the continents and ocean floors. It can be three to five miles

thick under the oceans and 15 to 35 miles thick on the continents.

Earth’s Interior

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The earth's crust is broken into pieces called plates. Magma comes close to the

earth's surface near the edges of these plates. This is where volcanoes occur. The lava that

erupts from volcanoes is partly magma. Deep underground, the rocks and water absorb

the heat from this magma. The temperature of the rocks and water get hotter and hotter as

the depth increases underground.

People around the world use geothermal energy to heat their homes and to

produce electricity by digging deep wells and pumping the heated underground water or

steam to the surface. Or, one can make use of the stable temperatures near the surface of

the earth to heat and cool buildings.

First Geothermal Power Plant In The World

In 1904 emerging steam was used to turn a small turbine which in turn powered five light

bulbs - the first ever demonstration of geothermal electricity generation. In 1911 the

Valle del Diavolo (Devil's Valley) was chosen as the site of what would remain the

world's only geothermal power station for almost half a century. By 1913 a 250kW power

station had been built which provided power for the Italian electric railway system.

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Prince Piero Ginori Conti invented the first geothermal power plant in 1904, at the

Larderello dry steam field in Italy

How does geothermal energy come to the surface?

Flow of magma up into volcanoes, which discharge it as lava.

Flow of underground water, or steam, naturally heated deep in the Earth.

Flow of water or steam, injected and retrieved by human effort.

Because the geologic processes known as plate tectonics, the Earth’s crust has been

broken into 12 huge plates that move apart or push together at a rate of millimeters per

year. Where two plates collide, one plate can thrust below the other, producing

extraordinary phenomena such as ocean trenches or strong earthquakes. At great depth,

just above the down going plate, temperatures become high enough to melt rock, forming

magma. Because magma is less dense than surrounding rocks, it moves up toward the

earth’s crust and carries heat from below. Sometimes magma rises to the surface through

thin or fractured crust as lava. However, most magma remains below earth’s crust and

heats the surrounding rocks and subterranean water.

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Schematic representation of an ideal geothermal system.

So, how does water get there then, deep in the Earth? It usually gets there through

rain water trickling down rock fissures. Where a lot of it collects in underground aquifers,

and is heated by the Earth, it expands and may rise to the surface as water or steam. Hot

water in such geothermal reservoirs can reach temperatures of 700F (or 370C). Now this

source of heating energy has been used by people for many centuries.

The third way of getting at this energy is facilitated by humans. It involves

injecting water at high pressures deep into porous heated rock formations and retrieving it

as hot water.

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The Three Main Applications Of Geothermal Energy Are:

1) Direct Use and District Heating Systems which use hot water from springs or

reservoirs near the surface. 

2) Electricity generation in a power plant requires water or steam at very high

temperature (300 to 700 degrees Fahrenheit). Geothermal power plants are generally built

where geothermal reservoirs are located within a mile or two of the surface. 

3) Geothermal heat pumps use stable ground or water temperatures near the earth's

surface to control building temperatures above ground.

1) DIRECT USE AND DISTRICT HEATING SYSTEMS

The direct use of hot water as an energy source has been happening since ancient times.

The Romans, Chinese, and Native Americans used hot mineral springs for bathing,

cooking and heating.

Hot water near the earth's surface can be piped directly into buildings and industries for

heat. A district heating system provides heat for 95 percent of the buildings in Reykjavik,

Iceland.

2. GEOTHERMAL POWER PLANTS:

There are three geothermal power plant technologies being used to convert

hydrothermal fluids to electricity. The conversion technologies are

Dry steam

Flash Steam and

Binary Cycle

The type of conversion used depends on the state of the fluid (whether steam or water)

and its temperature.

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Dry Steam Power Plants:

Steam plants use hydrothermal fluids that are primarily steam. The steam goes

directly to a turbine, which drives a generator that produces electricity. The steam

eliminates the need to burn fossil fuels to run the turbine. (Also eliminating the need to

transport and store fuels!) This is the oldest type of geothermal power plant. It was first

used at Lardarello in Italy in 1904, and is still very effective. Steam technology is used

today at The Geysers in northern California, the world's largest single source of

geothermal power. These plants emit only excess steam and very minor amounts of

gases.

Dry steam power plant

Types of dry steam power plants:

Atmospheric exhaust geo-thermal power plants.

Condensing geo-thermal power plants.

Atmospheric exhaust geo-thermal power plants:

Atmospheric exhaust turbines are simpler and cheaper. The steam, direct from dry

steam wells or, after separation, from wet wells, is passed through a turbine and

exhausted to the Atmosphere. With this type of unit, steam consumption (from the same

inlet pressure) per Kilowatt-hour produced is almost double that of a condensing unit.

However, the Atmospheric exhaust turbines are extremely useful as pilot plants, stand-by

plants, in the Case of small supplies from isolated wells, and for generating electricity

from test wells during field development. They are also used when the steam has a high

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non condensable Gas content (>12% in weight). The atmospheric exhaust units can be

Constructed and installed very quickly and put into operation. This type of machine is

usually available in small sizes (2.5 - 5 MW).

Atmospheric exhaust geo thermal power plant

Condensing geo-thermal power plants:

The condensing units, having more auxiliary equipment, are more complex than

the atmospheric exhaust units and the bigger sizes can take twice as long to construct and

install. The specific steam consumption of the condensing units is, however, about half

that of the atmospheric exhaust units. Condensing plants of 55 - 60 MW capacity are very

common.

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Condensing geo thermal power plant

Flash Steam Power Plants:

Hydrothermal fluids above 360°F (182°C) can be used in flash plants to make

electricity. Fluid is sprayed into a tank held at a much lower pressure than the fluid,

causing some of the fluid to rapidly vaporize, or "flash." The vapor then drives a turbine,

which drives a generator. If any liquid remains in the tank, it can be flashed again in a

second tank to extract even more energy. Both dry steam and flash steam power plants

emit small amounts of carbon dioxide, nitric oxide, and sulfur, but generally 50 times less

than traditional fossil-fuel power plants.

Flash steam power plant

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Binary-Cycle Power Plants:

Generating electricity from low-to-medium temperature geothermal fluids and

from the waste hot waters coming from the separators in water - dominated geothermal

fields has made considerable progress since improvements were made in binary fluid

technology. The binary plants utilize a secondary working fluid, usually an organic fluid

(typically n-pentane), that has a low boiling point and high vapour pressure at low

temperatures when compared to steam.

The secondary fluid is operated through a conventional Rankine cycle (RC): the

geothermal fluid yields heat to the secondary fluid through heat exchangers, in which this

fluid is heated and vaporizes; the vapour produced drives a normal axial flow turbine, is

then cooled and condensed, and the cycle begins again.

Binary cycle power plant

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By selecting suitable secondary fluids, binary systems can be designed to utilize

geothermal fluids in the temperature range 85-170 °C. The upper limit depends on the

thermal stability of the organic binary fluid, and the lower limit on technical-economic

factors: below this temperature the size of the heat exchangers required would render the

project uneconomical. Apart from low-to-medium temperature geothermal fluids and

waste fluids, binary systems can also be utilized where flashing of the geothermal fluids

should preferably be avoided (for example, to prevent well sealing). In this case, down

hole pumps can be used to keep the fluids in a pressurized liquid state, and the energy can

be extracted from the circulating fluid by means of binary units.

Binary plants are usually constructed in small modular units of a few hundred kW

to a few MW capacities. These units can then be linked up to create power-plants of a

few tens of megawatts. Their cost depends on a number of factors, but particularly on the

temperature of the geothermal fluid produced, which influences the size of the turbine,

heat exchangers and cooling system. The total size of the plant has little effect on the

specific cost, as a series of standard modular units is joined together to obtain larger

capacities. Binary plant technology is a very cost-effective and reliable means of

converting into Electricity the energy available from water-dominated geothermal fields

(below 170 °C).

A new binary system, the Kalina cycle, which utilizes a water-ammonia mixture

as Working fluid was developed in the 1990s. The working fluid is expanded, in

superheated Conditions, through the high-pressure turbine and then re-heated before

entering the low-pressure turbine. After the second expansion the saturated vapour moves

through a recuperative boiler before being condensed in a water-cooled condenser. The

Kalinaf cycle is more efficient than existing geothermal RC binary power plants, but is of

more complex design.

Electricity could facilitate many apparently banal, but extremely important

operations, such as pumping water for irrigation, freezing fruit and vegetables for longer

conservation.

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3. GEOTHERMAL HEAT PUMPS

Geothermal (ground water/ground source) technology utilizes a type of heat pump known

as a geothermal heat pump. This type of geothermal heat pump device extracts its heat

from water rather than from air. In this water is pumped through a special type of heat

exchanger and is either "chilled" by the evaporating refrigerant (in the heating mode) or

heated by the condensing refrigerant (in the cooling mode).

Types of Geothermal heat pumps

Open –Loop systems

Closed-Loop systems

Open –Loop systems:

An open loop is a loop established between a water source and a discharge area in which

the water is collected and pumped to a GWHP then discharged to its original source or to

another location. The piping for such configuration is open at both ends and the water is

utilized only once.

Open loop system

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Examples of such loops are: systems operating off wells wherein water is pumped from a

supply well, through the unit and discharged to a return well; open systems operating

from such surface water sources as ponds, lakes, streams, etc, where the source water is

pumped to the unit and returned to the source.

Open loops have the advantage of higher equipment performance since the source water

is used only once and then discharged, but have two significant disadvantages:

1. water quality needs to be carefully analyzed and treated if such corrosives as

sulphur, iron, or manganese are present , if pH is low, or if there are abrasives in it

2. the costs of pumping water through an open loop are usually somewhat higher

than those associated with circulating water through a closed loop

Closed –Loop systems:

A closed loop is one in which both ends of the loop's piping are closed. The water or

other fluid is re-circulated over and over and no new water is introduced to the loop. The

heat is transferred through the walls of the piping to or from the source, which could be

ground, ground water, or surface water. As heat is extracted from the water in the loop

the temperature of the loop falls and the heat from the source flows toward the loop.

Closed loop system

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In closed loop operation water quality is not an issue because corrosives become rapidly

"spent" or used up and corrosion caused by poor water quality is quickly curtailed The

wire-to-water efficiencies of circulators used in closed loop operation are very high and

the costs of pumping the water are lower as compared to open loops. System efficiencies

are somewhat lower in closed loop operation, but given the lower pumping costs

associated with this method, economics sometimes, but not always favor this approach.

Installed costs, however, are higher and need to be considered if the consumer already

has a well or other water source.

OTHER APPLICATIONS OF GEOTHERMAL ENERGY

 Agriculture:

Thermal water can be used in open-field agriculture to irrigate and/or heat the soil

and also to sterilize soil. Geothermal heat can also be used for crop and timber drying.

The main advantages of temperature control in open-field agriculture are:

o The prevention of plant damage from low air temperatures;

o Extension of the growing season;

o Increased plant growth and production; and

o Soil sterilization that controls pests and diseases.

Greenhouses:

Greenhouse heating is a common use of geothermal energy. Glass or plastic film

is used to trap solar radiation and heat, which provides a controlled environment for

plants to grow and increase yields. Many commercially grown vegetables, flowers, house

plants and tree seedlings are suitable for greenhouse culture.

Aquaculture:

Aquaculture is the farming of aquatic organisms including fish, and aquatic

plants. Farming implies some sort of intervention in the rearing process to enhance

production, such as regular stocking, feeding, and protection from predators. In

geothermal aquaculture the objective is to heat the water to the optimum temperature for

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fish growth. An emerging aqua cultural industry is the cultivation of vegetable species

that can be adapted for human and animal foods. Crops adaptable to geothermal enhanced

growth include duckweed, numerous algae species and kelp.

Industrial applications:

Geothermal energy can be cost effective and reliable in industrial applications.

Some of these uses include drying fish, fruits, vegetables and timber products, washing

wool, dying cloth, manufacturing paper and pasteurizing milk. The largest industrial

applications are in pulp, paper and wood processing.

Electricity Generation from Geothermal Energy In U.S.

2700 MW of power

0.4% of all electrical generation

Iceland is one of the more countries successful in using geothermal energy:

86% of their space heating uses geothermal energy.

16% of their electricity generation uses geothermal energy.

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Potential Geothermal Provinces of India

Province Surface

To C

Reservoir To

C

Heat

Flow    mW/m2

Thermal

gradient o

C/km

Himalaya >90 260 468 100

Cam bay 40-90 150-175 80-93 70

West coast 46-72 102-137 75-129 47-59

SONATA 60-95 105-217 120-290 60-90

Godavari 50-60 175-215 93-104 60

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Geothermal Energy And The Environment

The environmental impact of geothermal energy depends on how it is being used. Direct

use and heating applications have almost no negative impact on the environment.

Geothermal power plants do not burn fuel to generate electricity, so their emission levels

are very low. They release about 1 to 3 percent of the carbon dioxide emissions of a fossil

fuel plant. Geothermal plants use scrubber systems to clean the air of hydrogen sulfide

that is naturally found in the steam and hot water. Geothermal plants emit 97 percent less

acid rain - causing sulfur compounds than are emitted by fossil fuel plants. After the

steam and water from a geothermal reservoir have been used, they are injected back into

the earth. Well-designed binary cycle power plants have no emissions at all.

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ADVANTAGES OF GEOTHERMAL ENERGY

Geothermal is a reliable renewable energy source.

By using geothermal energy, millions of tones of fossil fuels are being saved

worldwide.

The land area required for geothermal power plants is smaller per megawatt than

for almost every other type of power plant.

It is resistant to interruptions of power generation due to weather, natural disasters

or political rifts that can interrupt transportation of fuels.

No fuel is needed

Once we've built a geothermal power station, the energy is almost free.

It may need a little energy to run a pump, but this can be taken from the energy

being generated. So it is an economic benefit.

Geothermal energy does not produce any pollution, and does not contribute to the

greenhouse effect. So it is eco-friendly in nature.

 DISADVANTAGES OF GEOTHERMAL ENERGY

The big problem is that there are not many places where you can build a

geothermal power station. You need hot rocks of a suitable type, at a depth

where we can drill down to them. The type of rock above is also important, it

must be of a type that we can easily drill through.

Brine can salinate soil if the water is not injected back into the reserve after the

heat is extracted.

Extracting large amounts of water can cause land subsidence, and this can lead

to an increase in seismic activity. To prevent this the cooled water must be

injected back into the reserve in order to keep the water pressure constant

underground.

Drilling operation is noisy.

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The steam and hot water gushing out of the earth may contain H2S, CO2, NH3

and radon gas etc. If these gases are vented into the air, air pollution will be a

real hazard. These gases are to be removed by chemical action, before they are

discharged.

Overall efficiency for power production is low, about 15%, as compared to (35

to 40) % for fossil fuel plants.

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CONCLUSION:

The demand for electricity is growing exponentially year by year in India. Much

of this electricity is made by burning fossil fuels that are dirty and irreplaceable.

Fortunately, there are alternatives.

From the first power plant in Larderello, Italy, to the state-of-the-art facilities

found all over the world today, geothermal plants use natural hot water and steam from

the earth to run turbine generators. If geothermal energy continues to be used at the

present rate, it is estimated that the available resources could last for five million years.

Technological advances are making this a cost-effective resource. Expect to see its

increased use in the near future, especially in the geothermally active western United

States, India, Indonesia, and other "hot spots" around the Pacific.

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REFERENCES

1. www.energy.gov/energysources/geothermal.htm

2. www.trimodalgesthermal.com

3. www.geothermal.org/index.htm

4. www.geothermal.marin.org

5. Non-Conventional Energy Resources by G.D.RAI