GEOTHERMAL ENERGY

What is Geothermal Energy?• Geothermal energy is thermal energy generated

and stored in the Earth. Thermal energy is 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%).

• Earth's internal heat is thermal energy generated from radioactive decay and continual heat loss from Earth's formation. Temperatures at the core–mantle boundary may reach over 4000 °C • The high temperature and pressure in Earth's

interior cause some rock to melt and solid mantle to behave plastically, resulting in portions of mantle convecting upward since it is lighter than the surrounding rock. Rock and water is heated in the crust, sometimes up to 370 °C

Looking briefly into the past• The oldest known pool fed by a hot spring, built in

the Qin dynasty in the 3rd century BCE.• Hot springs have been used for bathing at least

since paleolithic times .The oldest known spa is a stone pool on China's Lisan mountain built in the Qin Dynasty in the 3rd century BC, In the first century AD, Romans conquered Aquae Sulis, England, used the hot springs there to feed public baths and underfloor heating. The admission fees for these baths probably represent the first commercial use of geothermal power.

• The world's oldest geothermal district heating system in Chaudes-Aigues, France, has been operating since the 14th century. • The earliest industrial exploitation began in 1827 with

the use of geyser steam to extract boric acid from volcanic mud in Larderello, Italy.• In 1892, America's first district heating system

in Boise, Idaho was powered directly by geothermal energy. A deep geothermal well was used to heat greenhouses in Boise in 1926, and geysers were used to heat greenhouses in Iceland and Tuscany at about the same time.

• In the 20th century, demand for electricity led to the consideration of geothermal power as a generating source. Prince Piero Ginori Conti tested the first geothermal power generator on 4 July 1904, at the same Larderello dry steam field where geothermal acid extraction began. It successfully lit four light bulbs. Later, in 1911, the world's first commercial geothermal power plant was built there. • In 1960, Pacific Gas and Electric began operation of

the first successful geothermal electric power plant in the United States at The Geysers in California. The original turbine lasted for more than 30 years and produced 11 MW net power.

SOURCES

Hot water reservoirs Natural steam reservoirs Geo pressurised reservoirs Normal geothermal gradient Hot dry rocks Molten magma

INDICATIONS Hot springs Geysers Geothermal reservoirs Volcanoes

EXPLORATION Bubbling mud, geysers and hot pools are

good indicators of geothermal activity at the surface, but what is going on underground?

Exploration methods Areas are explored, analysed and mapped Geological, geophysical and geochemical

data are combined Field models are developed Geothermal potential is assessed Drilling sites are identified

HOW IT IS OBTAINED? First, specialist geologists and engineers

locate an economic source of geothermal energy.

Site selection is based on heat content, fluid content, and permeability of the rock.

The methods used are: Geothermal drilling Heat exchangers Heat pump installation

GEOTHERMAL EXPLORATION SURVEYS Satellite imagery and aerial photography Volcanological studies Geologic and structural mapping Geographical analysis Temperature gradient hole drilling

EXAMINING OF ROCKS

DISCOVERY OF RESERVOIR

BASIC METHODS AND

TECHNOLOGIES

Dry Steam Plants: These were the first type of plants created. They use underground steam to directly turn the turbines.

Flash Steam Plants: These are the most common plants. These systems pull deep, high pressured hot water that reaches temperatures of 3600F or more to the surface. This water is transported to low pressure chambers, and the resulting steam drives the turbines. The remaining water and steam are then injected back into the source from which they were taken.

Binary Cycle Plants: This system passes moderately hot geothermal water past a liquid, usually an organic fluid, that has a lower boiling point. The resulting steam from the organic liquid drives the turbines. This process does not produce any emissions and the water temperature needed for the water is lower than that needed in the Flash Steam Plants (2500F – 3600F).

Electricity Generation

There are 3 types of power plants:-

Dry steam power plant Flash steam power plant

Binary cycle power plant

Dry Steam power plant Geothermal reservoir containing pure steam is required.Pure dry steam drives turbine.Very rare type of geothermal power plant.

Flash steam power plant Geothermal reservoirs containing both hot water & steam is

required.Pressure changing system is required.

Binary cycle power plant Does not use steam directly to spin turbines.Vapourized hydrocarbons are used to spin the turbine.Hydrocarbons having lower boiling point such as

 isopentane, isobutane and propane can be used.No harmful gas is emitted to the atmosphere.

Turbine & generator:-

Thermal efficiency of the plantsThe thermal efficiency of these plants is low around

7-10% because geothermal fluids are at low temperatures compared to steam in boilers.

By the laws of thermodynamics this low temperature limits the efficiency of heat engines in extracting useful energy during the generation of electricity.

The efficiency of the system does not affect operational costs as it would for a coal or other fossil fuel plant, but it does factor into the viability of the station.

CostDirect use of geothermal energy is absolutely cheaper than other energy

sources.

Cost of electricity generation depends upon certain factors:Temperature and depth of resourceType of resource (steam, liquid, mix) Available volume of resource

Size and technology of plantThe initial investment is high.

They cost around US $0.05 to $0.08 (Rs. 2.772 to Rs. 4.4352) per kWh

Once the capital cost is recovered, the price can decrease to below US $0.05 (Rs 2.2772) per kWh

WORLD LEVEL USAGE

• Air conditioning• Industrial processes• Drying • Greenhouses• Aquaculture• Hot water• Resorts and pools• Melting snow

DIRECT USES

Most of New Zealand’s geothermal energy goes to produce electricity, but it can be used for any processes where heat is required. The heat is used for digesting wood pulp, drying timber and paper, and generating electricity.

INDUSTRIAL PROCESSING

The world’s only geothermally heated prawn farm was established in 1987 on the banks of the Waikato River, next to the Wairākei power station. The farm heats its own water with heat exchangers, which draw heat from the power station’s waste water before it flows back into the Waikato River.

FARMING

Geothermal waters are used for heating greenhouses on a small scale (covering 10 hectares in total), specially for the commercial, out-of-season production of vegetables, flowers and fruit.

GREENHOUSE HEATING

DISTRICT HEATING There are 18 district heating systems

operating in the western United States. Over 270 cities in the western U.S. Are

close enough to geothermal reservoirs to use district heating.

Hot water from one or more geothermal wells is piped through a heat exchanger plant to heat city water in separate pipes. Hot city water is piped to heat exchangers in buildings to warm the air.

In some places, geothermal water is piped from wells to heat single homes or whole residential or commercial districts. This truck-mounted drill rig is drilling a well for use in Klamath Falls, Oregon.

These pumps are used to pump the heated water to buildings in a district heating system, after it has passed through the heat exchanger.

This is a "plate type" heat exchanger which passes hot geothermal water past many layers of metal plates, transferring the heat to other water passing through the other side of each plate.

GEOTHERMAL ENERGY IN

INDIA

India has reasonably good potential for geothermal; the potential geothermal provinces can produce 10,600 MW of power.Though India has been one of the earliest countries to begin geothermal projects way back in the 1970s, but at present there are no operational geothermal plants in India. There is also no installed geothermal electricity generating capacity as of now and only direct uses (eg. Drying) have been detailed.

More than 300 hot spring locations have been identified by Geological survey of India (Thussu, 2000). The surface temperature of the hot springs ranges from C to as much as C. These hot springs have been grouped together and termed as different geothermal provinces based on their occurrence in specific geotectonic regions, geological and structural regions such as occurrence in orogenic belt regions, structural grabens, deep fault zones, active volcanic regions etc.

General Scenario:

Potential sites:Province Surface

Temp CReservoir

Temp CHeat Flow Thermal

gradient

Himalaya >90 260 468 100

Cambay 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

Geothermal Field Estimated (min.) reservoir Temp (Approx) Status

Puga geothermal field 240oC at 2000m From geochemical and deep geophysical studies (MT)

Tattapani Sarguja (Chhattisgarh) 120oC - 150oC at 500 meter and 200oC at 2000 m

Magneto telluric survey done by NGRI

Tapoban Chamoli (Uttarakhand) 100oC at 430 meter Magneto telluric survey done by NGRI

Cambay Garben (Gujrat) 160oC at 1900 meter (From Oil exploration borehole)

Steam discharge was estimated 3000 cu meter/ day with high

temperature gradient.Badrinath Chamoli (Uttarakhand) 150oC estimated Magneto-telluric study was done

by NGRIDeep drilling required to

ascertain geothermal fieldSurajkund Hazaribagh (Jharkhand) 110oC Magneto-telluric study was done

by NGRI.Heat rate 128.6 mW/m2

ManikaranKullu (H P)

100oC Magneto-telluric study was done by NGRI

Heat flow rate 130 mW/m2

KasolKullu (H P)

110oC Magneto-telluric study was done by NGRI

Total thermal installed capacity in MW: 203.0

Direct use in TJ/year 1,606.3Direct use in GWh/year 446.2

Capacity factor 0.25

HISTORICAL CAPACITY & CONSUMPTION DATA:

Panx Geothermal LNJ Bhilwara Tata Power Thermax NTPC Avin Energy Systems GeoSyndicate Power Private Limited

Geothermal companies:

• "Geothermal Energy - Initiative and Development" conference. Pandit Deendayal Petroleum University organised the event, which took place on 26 July 2013 in Gujarat's capital city Gandhinagar.• Companies involved in the Indian geothermal

projects include ONGC (Oil and Natural Gas Corporation) in Gujarat. The company has started exploring clean energy to create growth opportunities and maximize shareholder value.• ONGC started cooperation with Belgian company

Talboom last year

RECENTLY A PROJECT IS BEING DEVELPOED IN INDIA:

• MeSy IndiaMeSy India acts as technical arm to governmental institutions in the conduction of scientific and geothermal research projects, and stimulates new R&D projects in collaboration with Indian national research institutions and international organizations, in particular in the field of techniques and earthquake mechanisms, reservoir induced seismicity, advanced mining technologies, ground water production stimulation, use of geothermal energy, hazardous underground waste storage.• Geological Survey of India• National Geophysical Research Institute,

Hyderabad• Oil and Natural Gas Corporation,

Dehradun 

Geothermal research centres:

EFFECTS ON THE ENVIRONMENT

OF GEOTHERMAL ENERGY

DEPLETION OF RESOURCES: The process of extracting geothermal fluids 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.

SUBSIDENCE :Extracting geothermal fluids can reduce the pressure in underground reservoirs and cause the land to sink. The largest subsidence on record is at Wairākei, where the centre of the subsidence bowl is sinking at a rate of almost half a metre every year. In 2005 the ground 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.

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. Carbon dioxide is also a greenhouse gas, contributing to potential climate change.

ADVANTAGES OF

GEOTHERMAL ENERGY

1. Significant Cost Saving : Geothermal energy generally involves low running 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. No Pollution : This is one of the main advantage of using geothermal energy since 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 very harmful to the environment.4. Direct Use : Since ancient times, people having been using this source of energy 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 run with huge cost saving it proves quite useful.

5. Job Creation and Economic Benefits : Government of various countries are investing hugely in creation of geothermal energy which on other hand has created more jobs for the local peopleThough above said advantages prove that geothermal energy has big capability in itself in creating clean and safe environment and also it is an excellent source of cheap, reliable, simple, clean and renewable power but it also suffers from few drawbacks which is why it is not being utilized everywhere to its full capacity.

6.It is a non-renewable source of energy.7. There is no wastage or generation of byproducts.

10. Maintenance cost of geothermal power plants is very less.

11. These power plants does not occupy much space and thus help in protecting environment.

12. Unlike solar energy,it is not dependent on weather conditions.

DISADVANTAGES OF

GEOTHERMAL ENERGY

1. Not Widespread Source of Energy : Since this type of energy is not widely 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 one time 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 steam over 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 have invested heavily in these plants. Due to this factor, companies have to do extensive initial research before setting up the plant.

4. Suited To Particular Region : It is only suitable for regions which have 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 some poisonous 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. Once the 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.7. Only few sites have the potential of geothermal energy.

8.  Most of the sites, where geothermal energy is produced, are far from markets or cities, where it needs to be consumed.9. Total generation potential of this source is too small.10. There is always a danger of eruption of volcano.11.  Installation cost of steam power plant is very high.12.  There is no guarantee that the amount of energy which is produced will justify the capital expenditure and operations costs.13.  It may release some harmful, poisonous gases that can escape through the holes drilled during construction.

FUTURE OF GEOTHERMAL ENERGY

The first geothermal power plant is established in 1911 in Larderello, Italy.

Currently only 24 countries are able to produce electricity from geothermal energy in large scale producing a total of 11,700 MW of electricity.

But it only comprises for about less than 0.4% of the worlds electricity consumption.

This is mainly due to the fact that there is 75-80% chance of failure for exploratory well digging and geothermal energy is not available at all places.

Due to these facts developing countries like India is unable to install a geothermal power plant due to high risk and unavailability of geothermal energy.To support the establishment of geothermal power plants the International Geothermal Association(IGA) and International Renewable Energy Alliance(REN alliance) has funded more than 10 projects and more than 65 countries are its members so in order to overcome these limitations research is going on at IGA,Bocham,Germany to produce geothermal power more efficiently at low installation costs

a geothermal power plant in Utah, U.S.A

CONCLUSIONS & SUMMARY