Geothermal Electrical Energy Report

7/29/2019 Geothermal Electrical Energy Report

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INTRODUCTION

NON-CONVENTIONAL SOURCES OF ENERGY

The Industrial Revolution of the 19th century ushered in newtechnologies. The spurt in

inventions in that century was unprecedented in many ways. Some of these inventions

involved use of natural resources like coal and oil. The thought of exhaustible nature of

these resources and the environmental damage from the use of these resources never

occurred either to the inventors or the subsequent generations. In the quest to sustain

galloping economic activity, the dependence on coal and oil has soared at a phenomenal

rate over the years. The burnt fuels result in the release of carbondioxide and other gases

into the atmosphere causing environmental damage. It has become imperative to look at

energy technology with a new perspective. There are abundant renewable sources of

energy such as wind,sun, water, sea, biomass apart from even daily wastes. These sources

are pollution free and hence clean energy apart from being unlimited inexhaustible.

Power generation in India has grown in size to around 1 lakh MW andin Tamil Nadu it

has increased to 7924 MW which is distributed through a vast network of transmission,

sub-transmission and distribution lines that reach all villages even in remote areas. The

demand for power is growing rapidly. The problem will be compounded due to fast

depletion of fossil fuel deposits, quality of fuels, heavy price to be paid for basic

materials plus their transportation cost and above all the environmental degradation

caused by the use of conventional energy sources. Under such conditions, environment

friendly and pollution-free, non-conventional and renewable energy sources known as

'clean and green energy' have emergedas an important alternatives to conventional energy

sources. The renewable energy sources are clean and inexhaustible as they rely on sun,

wind, biomass, etc., as primary sources of energy. It is estimated that, about 2000 MW

can be generated from wind potential available in Tamil Nadu.

As against this potential, 19 MW of power in the State Sector mostly through

demonstration wind farms and 838 MW in the private sector have been harnessed as on

31.3.02, Under Biomass, the estimated potential is about 500 MW and 154 MW capacity

has been expected using biomass bagasse. The country is endowed with large amount of

sustainable resource base and non-conventional energy technologies which are well-

suited for grid connected power generation, energy supplies in remote areas which are not


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could not be connected to the grid and for captive consumption. Nonconventional energy

sources like wind energy, solar energy through thermal as well as photovoltaic system,

biomass and hybrid sources will help to great extent in enhancing power generation

capacity. Hence appropriate policies and programmes that optimize the use of available

energy resources with new technologies have to be propagated, promoted and adopted, if

necessary, by budgetary support.


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HISTORY OF GEOTHERMAL ENERGY

Geothermal energy is thermal energy generated and stored in the Earth. Thermal energyis the energy that determines the temperature of matter. The Geothermal energy of the

Earth's crust originates from the original formation of the planet (20%) and from

radioactive decay of minerals (80%). The geothermal gradient, which is the difference in

temperature between the core of the planet and its surface, drives a continuous

conduction of thermal energy in the form of heat from the core to the surface

At the core of the Earth, thermal energy is created by radioactive decay and temperatures

may reach over 5000 degrees Celsius (9,000 degrees Fahrenheit). Heat conducts from the

core to surrounding cooler rock. The high temperature and pressure cause some rock to

melt, creating magma convection upward since it is lighter than the solid rock. The

magma heats rock and water in the crust, sometimes up to 370 degrees Celsius (700

degrees Fahrenheit).

From hot springs, geothermal energy has been used for bathing since Paleolithic times

and for space heating since ancient Roman times, but it is now better known for

electricity generation. Worldwide, about 10,715 megawatts (MW) of geothermal power is

online in 24 countries.


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GEOTHERMAL ENERGY SOURCES

There is a spectrum of geological formations from which geothermal energy can be

obtained. At one end of the spectrum there are conventional hydrothermal systems where

hot water or steam trapped in underground reserviors or aquifers flows to the surfacethrough to hot dry rocks at the other end of the spectrum, where there is no natural

permeable reservoir.

Most of the World's operating geothermal energy power plants are located in hot volcanic

regions where hot underground reservoirs have been formed from water seeping from the

surface through natural fractures and faults near molten magma or hot volcanic rocks.

These systems are often found near volcanically active tectonic plate boundaries such as

in New Zealand, Iceland and The Philippines.

Hydrothermal systems can also occur outside volcanic regions where the rocks are hotterthan normal and water has collected within sedimentary rock. These systems can be

found in Hungary where the earth's crust is relatively thin or in the Perth Basin in

Western Australia and below the Cooper Basin in South Australia where rocks generate

anomalous quantities of heat.

Geothermal power plants, fed by hydrothermal systems, are therefore mostly located

where there is volcanic activity. The geothermal energy is recovered by harvesting the

hot water, or steam, already in the Earth.


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In some hydrothermal systems the permeability of the hot rocks may be too low to enable

the water to flow at a rate sufficient for electricity generation. The flow rate, and thus

productivity, of these hydrothermal systems can often be improved by pumping water,under pressure, down the wells to open additional fractures and pathways in the hot

underground reservoirs. This technique, first developed by the petroleum industry, and

now being refined by the geothermal industry, is known as fracture stimulation.

A geothermal reservoir, or system, that has been fracture stimulated to improve the water

flow rate, is often called an Engineered or Enhanced Geothermal System. Fracture

stimulation is used to generate a permeable underground reservoir for hot dry rock

systems and is also used to improve the permeability of hydrothermal systems.

This brings us to the other end of the spectrum, Hot Rock systems that do not have a

natural system of permeable water filled fractures or faults. They are normally associated

with granites that contain anomalously high concentrations of the naturally radioactive

elements uranium (U), thorium (Th) and potassium (K). Although enriched in these

elements compared to other rocks, radioactive element concentrations are still relatively

low. The radioactive decay of these elements over millions of years generates heat which

is trapped underground when the granites become buried by insulating sediments.


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Hot Rock systems can be either hot wet rocks where there are water filled fractures,

through to hot dry rocks where the extraction of heat is achieved by pumping cool water

from the surface into the rocks at depth and subsequently withdrawing it at a much higher

temperature after it has flowed under pressure through fractures in the hot rocks.

Sedimentary Rock

The easiest rock to drill into is sedimentary rock, rock that is formed by the erosion of

older rocks into a form of compressed sand. It is within the porous confines of sandy,

fractured or cavernous sedimentary rock that water is trapped and becomes heated by hot

rocks or magma.

Sedimentary rock provides two major advantages for geothermal energy production over

volcanic rock and granite. Firstly, as most of the World's fossil fuels are formed in

sedimentary rocks they have been drilled, assessed and mapped.

Secondly, where sedimentary rock is porous, it usually traps water. Therefore in order to

harness the energy from hot sedimentary rock there is no need to introduce water and

circulate it through the rock as it is already there.

Hot RocksWells are drilled into rocks which are much hotter than normal and sufficiently hot to

enable commercial generation of electricity.Hydraulic fracturing is used to enhance the

natural fracture pathways of the hot reservoir rocks.

Geothermal energy from hot dry rocks is recovered by drilling deep into the hot

crystalline rocks (usually granites) and forcing water down an injection well and through

fractures forced open by the water pressure in the rocks and back to the surface through

fractures connecting to other wells drilled nearby. The water gathers heat and becomes

superheated as it flows through the hot rocks


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GEOTHERMAL ENVIRONMENTAL PROBLEMS

Depletion of resources

The process of extracting geothermal fluids (which include gases, steam and water) for

power generation typically removes heat from natural reservoirs at over 10 times their

rate of replenishment. This imbalance may be partially improved by injecting waste

fluids back into the geothermal system.

Damage to natural geothermal features

Natural features such as hot springs, mud pools, sinter terraces, geysers, fumaroles (steam

vents) and steaming ground can be easily, and irreparably, damaged by geothermal

development. When the Wairkei geothermal field was tapped for power generation in

1958, the withdrawal of hot fluids from the underground reservoir began to cause long-

term changes to the famous Geyser Valley, the nearby Waiora Valley, and the mighty

Karapiti blowhole. The ground sagged 3 metres in some places, and hot springs and

geysers began to decline and die as the supply of steaming water from below was

depleted.

In Geyser Valley, one of the first features to vanish was the great Wairkei geyser, which

used to play to a height of 42 metres. Subsequently, the famous Champagne Pool, a blue-

tinted boiling spring, dwindled away to a faint wisp of steam. In 1965 the Tourist Hotel

Corporation tried to restore it by pumping in some three million litres of water, but to no

avail. Geyser Valley continued to deteriorate, and in 1973 it was shut down as a tourist

spectacle. This story has been repeated many times where there has been geothermal

development.

Subsidence

Extracting geothermal fluids can reduce the pressure in underground reservoirs and cause

the land to sink. The largest subsidence on record is at Wairkei, where the centre of the

subsidence bowl is sinking at a rate of almost half a metre every year. In 2005 the ground


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was 14 metres lower than it was before the power station was built. As the ground sinks it

also moves sideways and tilts towards the centre. This puts a strain on bores and

pipelines, may damage buildings and roads, and can alter surface drainage patterns.

Polluting waterways

Geothermal fluids contain elevated levels of arsenic, mercury, lithium and boron because

of the underground contact between hot fluids and rocks. If waste is released into rivers

or lakes instead of being injected into the geothermal field, these pollutants can damage

aquatic life and make the water unsafe for drinking or irrigation.

A serious environmental effect of the geothermal industry is arsenic pollution. Levels of

arsenic in the Waikato River almost always exceed the World Health Organisation

standard for drinking water of 0.01 parts per million. Most of the arsenic comes from

geothermal waste water discharged from the Wairkei power station. Natural features

such as hot springs are also a source of arsenic, but it tends to be removed from the water

as colourful mineral precipitates like bright red realgar and yellowy green orpiment.

Air emissions

Geothermal fluids contain dissolved gases which are released into the atmosphere. The

main toxic gases are carbon dioxide (CO2) and hydrogen sulfide (H2S). Both are denser

than air and can collect in pits, depressions or confined spaces. These gases are a

recognised hazard for people working at geothermal stations or bore fields, and can also

be a problem in urban areas. In Rotorua a number of deaths have been attributed to

hydrogen sulfide poisoning, often in motel rooms or hot-pool enclosures. Carbon dioxide

is also a greenhouse gas, contributing to potential climate change. However, geothermal

extraction releases far fewer greenhouse gases per unit of electricity generated than

burning fossil fuels such as coal or gas to produce electricity.


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Advantages and Disadvantages of Geothermal Energy

As our reliance on fossil fuels have started to increase, geothermal energy is seen as the

new source of power generation by digging out the heat stored inside the earth. Though

not used fully due to factors such as location and high costs but in the years to come

when fossil fuels would start to diminish, it will turn out to be the cheapest source of

power generation. Geothermal energy suffers from its own advantages and disadvantages

as described below.

1. Significant Cost Saving: Geothermal energy generally involves lowrunning costs since it saves 80% costs over fossil fuels and no fuel is used to

generate the power. Since, no fuel is require so costs for purchasing, transporting

and cleaning up plants is quite low.

2.

Reduce Reliance on Fossil fuels:Dependence on fossil fuels

decreases with the increase in the use of geothermal energy. With the sky-

rocketing prices of oil, many countries are pushing companies to adopt these

clean sources of energy. Burning of fossil fuels releases greenhouse gases which

are responsible for global warming.

3.

Reduce Reliance on Fossil fuels:Dependence on fossil fuelsdecreases with the increase in the use of geothermal energy. With the sky-

rocketing prices of oil, many countries are pushing companies to adopt these

clean sources of energy. Burning of fossil fuels releases greenhouse gases which

are responsible for global warming.


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4. No Pollution :This is one of the main advantage of using geothermal energysince it does not create any pollution and help in creating clean environment.

Being the renewable source of energy, geothermal energy has helped in reducing

global warming and pollution. Moreover, Geothermal systems does not create any

pollution as it releases some gases from deep within the earth which are not veryharmful to the environment.

5. Direct Use :Since ancient times, people having been using this source ofenergy for taking bath, heating homes, preparing food and today this is also used

for direct heating of homes and offices. This makes geothermal energy cheaper

and affordable. Although the initial investment is quite steep but in the long runwith huge cost saving it proves quite useful.

6. Job Creation and Economic Benefits :Government of variouscountries are investing hugely in creation of geothermal energy which on other

hand has created more jobs for the local people.


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Disadvantages Of Geothermal Energy

Energy created from geothermal power is safe, clean, simple, reliable and environment

friendly as it is extracted from deep within the earths surface. But despite these

advantages, geothermal energy is not being used widely. Geothermal energy suffers from

its disadvantages as described below.

1.

Not Widespread Source of Energy :Since this type of energy is notwidely used therefore the unavailability of equipment, staff, infrastructure,

training pose hindrance to the installation of geothermal plants across the globe.

Not enough skilled manpower and availability of suitable build location pose

serious problem in adopting geothermal energy globally.

2. High Installation Costs :To get geothermal energy, requires installation

of power plants, to get steam from deep within the earth and this require huge onetime investment and require to hire a certified installer and skilled staff needs to

be recruited and relocated to plant location. Moreover, electricity towers, stations

need to set up to move the power from geothermal plant to consumer.

3. Can Run Out Of Steam :Geothermal sites can run out of steamover a period of time due to drop in temperature or if too much water is injected

to cool the rocks and this may result huge loss for the companies which haveinvested heavily in these plants. Due to this factor, companies have to do

extensive initial research before setting up the plant.


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4. Suited To Particular Region : It is only suitable for regions whichhave hot rocks below the earth and can produce steam over a long period of time.

For this great research is required which is done by the companies before setting

up the plant and this initial cost runs up the bill in setting up the geothermal power

plant. Some of these regions are near hilly areas or high up in mountains.

5. May Release Harmful Gases : Geothermal sites may contain somepoisonous gases and they can escape deep within the earth, through the holes

drilled by the constructors. The geothermal plant must therefore be capable

enough to contain these harmful and toxic gases.

6. Transportation : Geothermal Energy can not be easily transported. Oncethe tapped energy is extracted, it can be only used in the surrounding areas. Other

sources of energy like wood, coal or oil can be transported to residential areas but

this is not a case with geothermal energy. Also, there is a fear of toxic substances

getting released into the atmosphere.


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GEOTHERMAL POTENTIAL:

Geothermal energy is the natural heat of the earth. Earth's interior heat originated from its

fiery consolidation of dust and gas over 4 billion years ago. It is continually regeneratedby the decay of radioactive elements, that occur in all rocks.

From the surface down through the crust, the normal temperature gradient - the increase

of temperature with the increase of depth - in the Earth's crust is 17 C -- 30 C per

kilometer of depth (50F--87F per mile).. .

Below the crust is the mantle, made of highly viscous, partially molten rocks with

temperatures between 650 C -- 1250 C (1200 F -- 2280 F). At the Earth's core, which

consists of a liquid outer core and a solid inner core, temperatures vary from 4000 C --

7000C(7200F--12600F).Major geothermal fields are situated in circum-pacific

margins, rift zones of East,Africa,North Africa, Mediterranean basin of Europe .


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Currently, hydrothermal energy is being commercially used for electricity generation and

for meeting thermal energy requirements. In 1997, The world's geothermal electricity

generation capacity was 8000 MW and another 12000 MW for thermal applications.

Italy, New Zealand, USA, Japan, Mexico, Philippines, Indonesia are some of the

countries which are using geothermal energy for electricity generation and thermal

applications. Exploration of geothermal fields needs knowledge of geology,

geochemistry, seismology, hydrology and reservoir engineering.

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.


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CONCLUSION:

Geothermal energy is limited in extent as extracting the heat usually exceeds the

replenishment rate

Hot, dry rock (HDR) is widespread and offers new resources in areas where

geyser activity is unknown

Direct low-temperature heat transfer for home systems is practical as long as low

maintenance is designed into the system

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 [Kruger, 1973].


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REFERENCES:

http://www.eere.energy.gov/geothermal/ Government Lab

http://www.geothermalheatpump.com/how.htmGood explanation of practical use

http://www.acmehowto.com/howto/appliance/refrigerator/overview.htmUniversity 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
http://www.geothermalheatpump.com/how.htmhttp://www.geothermalheatpump.com/how.htmhttp://www.geothermalheatpump.com/how.htm


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