Presented BY:

SOUMITA GHOSHGEOTHERMAL ENERGY: NEW PROSPECTS

CONTENTS Introduction Sources of Geothermal energyGeothermal Power Direct uses of Geothermal energy below 1500C Electricity Generation Geothermal Energy : Indian scenario New Prospects and latest Technology CPG technology to trap Geothermal heat. EGS Technology Conclusion

Geothermal energyisthermal energygenerated and stored in the Earth. Thermal energy is the energy that determines thetemperatureof matter. The adjective geothermal originates from the Greek roots (ge), meaning earth, and (thermos), meaning heat.

The geothermal energy of the Earth'scrustoriginates from the original formation of the planet (20%) and fromradioactive decayof materials (80%).

Earth's internal heatis thermal energy generated from radioactive decay and the residual heat left from Earth's formation. Temperatures at thecoremantle boundarymay reach over 4000C.

Geothermal power, if tapped into, is available around the clock, cost effective, reliable, sustainable, and environmentally friendly. When used to generate electricity, this means that geothermal energy is base-load, suited to producing energy at a constant level.

Introduction

Different Geothermal Energy Sources 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.

Natural Stem 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 US.

Geopressured Reservoirs: In this type of reserve, brine completely saturated with natural gas in stored under pressure from the weight of overlying rock

Normal Geothermal Gradient: 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.

Hot Dry Rock: 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.

Molten Magma: No technology yet exists to tap into the heat reserves stored in magma.

Geothermal Power

In nature, geothermal heat is in the form of volcanoes, hot springs and geysers. When heat >150C, it is considered hot enough to be used to generate electricity and heat.

The Earth's geothermal resources are theoretically adequate to supply humanity's energy needs, but only a very small fraction may be profitably exploited.

The geothermal potential of high-temperature resources suitable for electricity generation with conventional technologies (steam turbines, binary turbines) is spread rather irregularly and depends on the volcanic zones.

Direct uses of geothermal energy is appropriate for sources below 1500C space heatingindustrial processesdrying GreenhousesAquaculturehot waterresorts and poolsmelting snow

Generation of Electricity is appropriate for sources >150oCGeothermal power projects convert the energy contained in hot rock into electricity by using water to absorb heat from the rock and transport it to the earths surface, where it is converted to electrical energy through turbine-generators.

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

Flash Steam 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 is lower than that needed in the Flash Steam Plants .

Water from high-temperature reservoirs is partially flashed to steam, and heat is converted to mechanical energy by passing steam through low-pressure steam turbines.

Geothermal Energy : Indian Scenario India has reasonably good potential for geothermal; which if tapped into can produce 10,600 MW of power. At present there are no operational geothermal plants in India. There is also no installed geothermal electricity generating capacity as of now.

Plans to build India's first geothermal power plants are underway. Indian states Gujarat, Andhra Pradesh and West Bengal announce interest in developing the BRIC country's first geothermal energy plant, with power capacity in the range of 3MW to 5MW.

Companies involved in the Indian geothermal projects include-

ONGCPanx Geothermal Tata Power NTPC Avin Energy Systems GeoSyndicate Power Private Limited

Potential Sites

Puga Valley (J&K) Tatapani (Chhattisgarh)Godavari Basin (Himachal Pradesh)Bakreshwar (West Bengal) Tuwa (Gujarat) Unai (Maharashtra)Jalgaon (Maharashtra)

New Prospects and Latest technology to tap into the Geothermal Potential. Apart from the conventional power generation , several new prospects of harnessing the Geothermal power are used.

Low-temperature geothermal resources are typically used in direct-use applications, such asdistrict heating,greenhouses, mineral recovery, andindustrial process heating. There are at least 37 greenhouse and 58 aquaculture sites using geothermal energy in the United States alone.

Latest Technology CPG New technology that could revolutionize geothermal energy made waves at the American Geophysical Unionmeeting Aug, 2012. the world's hunger for energy will welcome the idea of CO2 Plumegeothermal poweror CPG.

CPG benefits include sequestering CO2; making geothermalenergy accessible in geographic regions where it has not been economically feasible to use this natural source for generating power; and storing energy from solar or wind farms. CPG could produce ten timesmore geothermal energythan traditional geothermal approaches currently yielded.

The liquid CO2, obtained by compressing the gas captured at the source from fossil fuel burning is pumped deep into the earth.Liquid CO2 would be pumped into horizontal wells set up in concentric rings deep in the earth.

Carbon dioxide flows through the porous rock bed deep in earth more quickly than water, collecting heat more easily and expands more than water when heated, so the pressure differential between the CO2 pumped into the ground and the heated CO2 is much greater. This pressure moves the Geothermal heat or steam up to surface level.

The amount of energy that can be generated depends on this pressure differential -- and is therefore substantially greater in CPG than in traditional geothermal plants.

The CO2 expands so much that the pressure alone can carry the heated CO2 back to the surface, an effect referred to as a "thermo-siphon". The thermo-siphon makes the use of pumps for recovering the hot CO2 unnecessary, reducing the energy costs required to generate the geothermal electricity for a higher overall efficiency.

Carbon Dioxide Plume Geothermal (CPG) technology

Developed at the University ofMinnesota (UMN) by Drs.Martin Saar, Jimmy Randolph,and Thomas Kuehn.

UMN filed U.S. patentallowed July 2012; Additionalpatents for CPG EORapplications filed in 2012

EGS Technology This is another latest development in this field. The EGS concept is to extract heat by creating a subsurface fracture system in the hot constituent rock to which water can be added through injection wells. Rocks are permeable due to minute fractures and pore spaces between mineral grains.

EGS are reservoirs created to improve the economics of resources without adequate water and permeability. Enhanced geothermal system (EGS) reservoir performance is controlled by the set of parameters: reservoir, geologic, drilling, plant design, and operation.

As depth and temperature increase, the permeability and porosity of the rocks decreases. To extract heat, it is required to drill to depths where the rock temperatures are sufficiently high to justify investment in the heat-mining project.

Conclusion Renewable energy technologies offer the promise of clean, abundant energy gathered from self renewing resources such as the sun, wind, earth, and plants.

At present, the scale of geothermal power industry is small because of the limitation of easily exploitable high temperature geothermal resources, therefore, the development of geothermal resources have to be primarily focused on utilization of ground source heat pumps which can make good use of the enormous low temperature geothermal.

Latest technologies for harnessing the Geothermal heat is coming up, such as the concept of CO2 PlumeGeothermal power(CPG) and Enhanced Geothermal System (EGS) which will further revive and commercialize the geothermal industry.

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