renewable energy sources BY MOSES DHILIP KUMAR

 renewable energy sources

ABSTRACT:
           

            “Reduce air pollution” this term will be better suited for the geothermal energy only. Geothermal, this is the Greek world in which geo means (earth). So geothermal means earth heat.
            In earlier days this geothermal energy has been used for bathing and heating, but it was until 20th century, now this geothermal power started for fuel and is there for virtually emissions free and insusceptible to fluctuations in fuel cost.
            Geothermal energy is that generating electricity form the natural that under the surface of the earth. Our earth’s interior consists of several layers’ of rocks to hot water & molten lava. The heat of the interior is used for producing power by some of the power plants. Wells are drilled over a mile deep into underground reservoir to tap out steam and very hot water which can be brought out to the surface for use in a variety of application, because the heat under the earth are up to 300 deg- 800 deg which can be in the form of steam. 
            Geothermal reservoirs that are close enough to the surface to be reached by drilling can occur in places where geologic processes have allowed magma to rise up through the crust, near to the surface, or where it flows out as lava. The crust of the Earth is made up of huge plates, which are in constant but very slow motion relative to one another.                           
              The first geothermally-generated electricity in the world was produced at Larderello, Italy; in 1904 the use of geothermal energy for electricity has grown worldwide to about 7,000 megawatts in twenty-one countries around the world. The United States alone produces 2700 megawatts of electricity from geothermal energy, electricity comparable to burning sixty million barrels of oil each year. .
 

INTRODUCTION:

Our earth is receiving heat naturally from the sun. But distinctly our earth’s interior unreal part it self is heat to high rate. The heat of the earth is very much wasted. So if the heat is made for useful purpose there is more advantage. Important of this is we can reduce the pollution.
This geothermal heat originates from earth’s fiery consolidation which consists of dust and dead plants and animals which have been decayed over 4000 year are changed to renewable resource.
The heat under the earth is up to 300’F to 800’F. This can be also in the form of steam for generation power. There are various type of power plant and various methods of producing power from geothermal energy. This paper also describes about it.
This geothermal energy is now produced by most of the countries such as united states new Zealand etc… and some of the countries are going project for setting the plants for generation of power by geothermal.

GENERAL DEFINITIONàGEOTHREMAL ENERGY

            Geothermal energy is the energy obtained by tapping the heat of the earth itself,usally from kilometers deep into the earth crust. Geothermal comes from the Greek words geo, meaning earth, and therme, meaning heat. Geothermal power is the use of geothermal heat to generate electricity. Geothermal power supplies 0.416% of the world's energy. Prince Piero Ginori Conti tested the first geothermal power plant on 4 July 1904, at the Larderello dry steam field in Italy.

 GEOTHERMAL ENERGY:
            Our earth’s interior consists of hard partial such as rocks whish are hot molten state. This heat is provided from the sun. This heat is geothermal energy which yields warmth and power that we can use without polluting the environment. At earth’s core about 4000 miles deep, the temp may reach over 9000`F.
The heat from the earth’s core flows continuously outward. It conducts the heat to the surrounding layer of rock and this is mantle when the temperature and pressure increases, some mantle rock melts, becoming magma which is the molten lava. Due to the increase of steam or hot water towards the earth’s crust.
 Sometimes this hot magma (lava) reaches the surface in the volcanoes. More often the magma remains below the crust, heating the rocks and water nearly. Some of the hot geothermal water travels back up through faults and cracks and reaches earth surface as hot spring as geysers. The collation of hot water is called geothermal reservoir.

GENERATION OF ELECTRICITY USING GEOTHERMAL ENERGY:

In the geothermal power plants steam or hot water with pressure from the geothermal reservoir provides the force that spins the turbine generation and produces electricity. The out use water is send to the reservoir through injection wells.There are various rinds or geothermal power plants. The rind of plant depends on the temperatures and pressure of the reservoir. A dry steam reservoir produces steam directly under ground, this is piped to generation.A geothermal reservoir that produces mostly hot water is called hot water reservoir and is used in a “flash” power plant. Water ranging in temperature from 300`F to 700`F is brought up to the surface through the oduction well. The steam with a temperature of 700`Fwhen send to turbine has a chance of damage. To reduce this,

            Steam is first send through the heat exchanger, at this heat is transferred to the cold water which turns to 300`F. The steam from the heat exchanger is about 400`F is now sending to turbine for power. Hence double power is generated.  A reservoir with temperatures between 250 - 360 degrees F is not hot enough to flash enough steam but can still be used to produce electricity in a "binary" power plant. In a binary system the geothermal water is passed through a heat exchanger, where its heat is transferred into a second (binary) liquid, such as isopentane, that boils at a lower temperature than water. When heated, the binary liquid flashes to vapor, which, like steam, expands across and spins the turbine blades. The vapor is then recondensed to a liquid and is reused repeatedly. In this closed loop cycle, there are no emissions to the air.

CAPACITY OF ELECTRICITY GENERATED:
              If heat recovered by ground source heat pumps is included, the non-electric generating capacity of geothermal energy is estimated at more than 100 GW (gigawatts of thermal power) and is used commercially in over 70 countries. During 2005, contracts were placed for an additional 0.5 GW of capacity in the United States. Estimates of exploitable worldwide geothermal energy resources vary considerably. According to a 1999 study, it was thought that this might amount to between 65 and 138 GW of electrical generation capacity 'using enhanced technology. A 2006 report by MIT that took into account the use of Enhanced Geothermal Systems (EGS), concluded that it would be affordable to generate 100 GW (gigawatts of electricity) or more by 2050 in the United States alone, for a maximum investment of 1 billion US dollars in research and development over 15 years. The report also calculated the world's total EGS resources to be over 13,000 ZJ. Of these, over 200 ZJ would be extractable, with the potential to increase this to over 2,000 ZJ with technology improvements - sufficient to provide the entire world's present energy needs for several millennia.
growing fish, shrimp, and alligators to maturity (aquaculture);

              

USES OF GEOTHERMAL ENERGY:

1. Geothermal waters ranging from 50 degrees F to over 300 degrees F are used directly from the earth:

2. To smooth acting muscles in hot springs, and health maintenance.

3. To help grow flowers, vegetables, and other crops in greenhouses while snow-drifts pile up outside (agriculture);

4. To shorten the time needed for growing fish, shrimp, and alligators to maturity (aquaculture);

5. To pasteurize milk, to dry onions and to wash wool.

This ensures that the ground does not freeze, providing a longer growing season and overall faster growth of agricultural products that are not protected by the shelter and warmth of a greenhouse. Rows of pipes carrying geothermal water have been installed under soil, where flowers or vegetables are growing. The world's largest district heating system is in Reykjavik, Iceland. Since it started using geothermal energy as its main source of heat Reykjavik, once very polluted, has become one of the cleanest cities in the world.
A RECENT SURVEY ON GEOTHERMAL ENERGY:

Global geothermal electric capacity.

Upper red line is installed capacity;

Lower green line is realized production.

USE OF GEOTHERMAL ENERGY NOWADAYS:

             Today we drill wells into the geothermal reservoirs to bring the hot water to the surface. Geologists, geochemists, drillers and engineers do a lot of exploring and testing to locate underground areas that contain this geothermal water, so we'll know where to drill geothermal production wells.

A TYPICAL GEOTHERMAL POWER LANT LAYOUT:

 

PARTS OF THE WORLD WHICH USE GEOTHERMAL ENERGY:
                    Magma can reach near the surface in three main geologic areas:  Where Earth's large oceanic and crustal plates collide and one slides beneath another, called a subduction zone The best example of these hot regions around plate margins is the Ring of Fire -- the areas bordering the Pacific Ocean: the South American Andes, Central America, Mexico, the Cascade Range of the U.S. and Canada, the Aleutian Range of Alaska, the Kamchatka Peninsula of Russia, Japan, the Philippines, Indonesia and New Zealand.

                                             

            Spreading centers, where these plates are sliding apart, (such as Iceland, the rift valleys of Africa, the mid-Atlantic Ridge and the Basin and Range Province in the U.S.); and places called hot spots-- fixed points in the mantle that continually produce magma to the surface. Because the plate is continually moving across the hot spot, strings of volcanoes are formed, such as the chain of Hawaiian Islands. The countries currently producing the most electricity from geothermal reservoirs are the United States, New Zealand, Italy, Iceland, Mexico, the Philippines, Indonesia and Japan, but geothermal energy is also being used in many other countries. The United States of America is the country with the greatest geothermal energy production.

            The largest dry steam field in the world is the Geysers, 72 miles (116 km) north of San Francisco. The Geysers began in 1960, has 1360 MW of installed capacity and produces over 750 MW net.

ADVANTAGES AND DISADVANTAGES:

I. CLEAN:
                  Geothermal power plants, like wind and solar power plants do not have to burn fuels to manufacture steam to turn the turbines. Generating electricity with geothermal energy helps to conserve nonrenewable fossil fuels, and by decreasing the use of these fuels, we reduce emissions that harm our atmosphere. There is no smoky air around geothermal power plants -- in fact some are built in the middle of farm crops and forests, and share land with cattle and local wildlife.

II. REQUIREMENT OF AREA:
                    The land area required for geothermal power plants is smaller per megawatt than for almost every other type of power plant. Geothermal installations don't require damming of rivers or harvesting of forests and there are no mine shafts, tunnels, open pits, waste heaps or oil spills.

III . RELIABLE:
             Geothermal power plants are designed to run 24 hours a day, all year. A geothermal power plant sits right on top of its fuel source. It is resistant to interruptions of power generation due to weather, natural disasters or political rifts that can interrupt transportation of fuels.

IV . FLEXIBLE:
            Geothermal power plants can have modular designs, with additional units installed in increments when needed to fit growing demand for electricity.

V . HELPS IN DEVELOPING COUNTRIES:
            Geothermal projects can offer all of the above benefits to help developing countries grow without pollution. And installations in remote locations can raise the standard of living and quality of life by bringing electricity to people far from "electrified" population centers.

DISADVANTAGES:
            When considering the disadvantage, its very less, when it is used directly it causes some of the skin problems because it from the earth directly without purifying. It can be utilized only in the areas where there is geothermal energy. Cost of the transmission is very high.

CONCLUSION:
            As per today’s scenario, fuel demand, shortage of the power supply cause a major problem in each ones life. So, that by using geothermal energy this can be reduced to some extend. Also the power produced now by the geothermal plant is up to about 100 ZW of power, if this made to increase more power can be produced and reduce the demands. For this more researches are going on.    Reducing the air pollution can be done by using the geothermal energy. Ozone layer is depleted only by means of means of the air pollution..