Geothermal Energy

Seminar Report

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Name: P.ROHITHRoll No: 10C41A0339Course: MECHANICAL

Department of MECHANICAL ENGINEERING

Jayamukhi institute of technological Sciences

Narsampet, warangal-506 332

(Affiliated to JNTUH, Accredited by NBA)APRIL 2014Jayamukhi institute of technological SciencesNarsampet, warangal 506 332

(Affiliated to JNTUH, Accredited by NBA)CERTIFICATE

This is to certify that the Seminar Report entitled GEO THERMAL ENERGY is submitted by P.ROHITH bearing Roll No 10C41A0339 in IV B.Tech (ME) II semester. Supervisor Head of the Department

MR. M.JAWAHAR Prof. V.VIKARAM REDDDY CONTENTS

1) INTRODUCTION2) SOURCES OF EARTHS INTERNAL ENERGY2.1 Different Geothermal Energy Sources3) DIRECT USES OF GEOTHERMAL ENERGY IS APPROPRIATE FOR SOURCES BELOW 1500C3.1How Direct Uses Work4) GROUND HEAT COLLECTERS4.1 Borehole Heat Exchange5) GENERATION OF ELECTRICITY6) HOT DRY ROCKS7) GEOTHERMALS HARMFUL EFFECTS8) GEOTHERMALS POSITIVE ATTRIBUTES9) GEOTHERMAL HEAT PUMPS10) AVAILABILITY OF GEO THERMAL ENERGY11) HIGH TEMPERATURE SYSTEMS12) LOW TEMPERATURE SYSTEMS13) ADVANTAGES14) CONCLUSION15) REFERENCES16) BIBILOGRAPHY1. INTRODUCTION

The centre of Earth is believed to be 5,500 degrees Celcius which is almost as hot as the surface of the sun. Geothermal (which literally means Earth Heat) energy is energy which is taken from inside the Earth and used by us. Even a couple of miles down the temperature of the Earth can be over 200 degrees Celcius. Therefore there is an enormous amount of energy to be tapped into

The top 15 metres of the Earth's surface have a relatively constant temperature through all of the seasons. Therefore one of the commonest uses of geothermal energy is Geothermal Heat Pumps. Pipes buried into the ground circulate fluid through the warm ground extracting energy and using it to heat buildings very efficiently. In the summer heat from buildings can be transfered back into the ground by the same process cooling the building. Geothermal heat pumps can be used almost everywhere on the Earth's surface. Often used in agriculture to heat greenhouses, geothermal heat pumps cut electricity bills by up to 80%.

Geothermal heat can also be used directly in volcanic locations around the world. For example, in Iceland water is heated by being pumped down into the ground and back up again. In those locations with extreme geothermal heat close to the surface (e.g. natural hot springs) it is even possible to generate electricity using turbines driven by the steam to power generators. Geothermal power stations are very clean emitting only steam and a few trace gases, and they take up very little space compared to fossil fuel power stations.

2. SOURCES OF EARTHS INTERNAL ENERGY 70% comes from the decay of radioactive nuclei with long half lives that are embedded within the Earth

Some energy is from residual heat left over from Earths formation.

The rest of the energy comes from meteorite impacts.

2.1 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. This type of resource can be used for both heat and for natural gas. 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 exists to tap into the heat reserves stored in magma. The best sources for this in the US are in Alaska and Hawaii.

3. DIRECT USES OF GEOTHERMAL ENERGY IS APPROPRIATE FOR SOURCES BELOW 1500C space heating

air conditioning

industrial processes

drying

Greenhouses

Aguaculture

hot water

resorts and pools

melting snow

3.1How Direct Uses Work:

Direct Sources function by sending water down a well to be heated by the Earths warmth.

Then a heat pump is used to take the heat from the underground water to the substance that heats the house.

Then after the water it is cooled is injected back into the Earth.

4.GROUND HEAT COLLECTERSThis system uses horizontal loops filled with circulating water at a depth of 80 to 160 cm underground.

4.1 Borehole Heat Exchange :

This type uses one or two underground vertical loops that extend 150 meters below the surface.

Fig.4.15. GENERATION OF ELECTRICITYDry 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.

Fig 5.1

6. HOT DRY ROCKSThe simplest models have one injection well and two production wells. Pressurized cold water is sent down the injection well where the hot rocks heat the water up. Then pressurized water of temperatures greater than 2000F is brought to the surface and passed near a liquid with a lower boiling temperature, such as an organic liquid like butane. The ensuing steam turns the turbines. Then, the cool water is again injected to be heated. This system does not produce any emissions. US geothermal industries are making plans to commercialize this new technology.

Fig 6.1

7. GEOTHERMALS HARMFUL EFFECTS 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 prevented this the cooled water must be injected back into the reserve in order to keep the water pressure constant underground.

Power plants that do not inject the cooled water back into the ground can release H2S, the rotten eggs gas. This gas can cause problems if large quantities escape because inhaling too much is fatal.

One well blew its top 10 years after it was built, and this threw hundreds of tons of rock, mud and steam into the atmosphere.

There is the fear of noise pollution during the drilling of wells.

8. GEOTHERMALS POSITIVE ATTRIBUTES Useful minerals, such as zinc and silica, can be extracted from underground water.

Geothermal energy is homegrown. This will create jobs, a better global trading position and less reliance on oil producing countries.

US geothermal companies have signed $6 billion worth of contracts to build plants in foreign countries in the past couple of years.

In large plants the cost is 4-8 cents per kilowatt hour. This cost is almost competitive with conventional energy sources.

Geothermal plants can be online 100%-90% of the time. Coal plants can only be online 75% of the time and nuclear plants can only be online 65% of the time.

Flash and Dry Steam Power Plants emit 1000x to 2000x less carbon dioxide than fossil fuel plants, no nitrogen oxides and little SO2.

Geothermal electric plants production in 13.380 g of Carbon dioxide per kWh, whereas the CO2 emissions are 453 g/kWh for natural gas, 906g g/kWh for oil and 1042 g/kWh for coal.

Binary and Hot Dry Rock plants have no gaseous emission at all.

Geothermal plants do not require a lot of land, 400m2 can produce a gigawatt of energy over 30 years.

9. GEOTHERMAL HEAT PUMPS produces 4 times the energy that they consume.

initially costs more to install, but its maintenance cost is 1/3 of the cost for a typical conventional heating system and it decreases electric bill. This means that geothermal space heating will save the consumer money.

can be installed with the help of special programs that offer low interest rate loans.

Electricity generated by geothermal plants saves 83.3 million barrels of fuel each year from being burned world wide. This prevents 40.2 million tons of CO2 from being emitted into the atmosphere.

Direct use of geothermal energy prevents 103.6 million barrels of fuel each year from being burned world wide. This stops 49.6 tons of CO2 from being emitted into the atmosphere.

Fig.9.1

Fig.9.2

Fig.9.3

10. AVAILABILITY OF GEO THERMAL ENERGY On average, the Earth emits 1/16 W/m2. However, this number can be much higher in areas such as regions near volcanoes, hot springs and fumaroles.

As a rough rule, 1 km3 of hot rock cooled by 1000C will yield 30 MW of electricity over thirty years.

It is estimated that the world could produce 600,000 EJ over 5 million years.

There is believed to be enough heat radiating from the center of the Earth to fulfill human energy demands for the remainder of the biospheres lifetime.

Geothermal production of energy is 3rd highest among renewable energies. It is behind hydro and biomass, but before solar and wind.

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.

Table 10.1

Table 10.2

11. HIGH TEMPERATURE SYSTEMS These areas are associated with the Ring of Fire volcanic activities around the Pacific Rim Basin

Geyser-temperature steam is contaminated with salts that cause corrosion of turbines or engines

Removing these salts to protect the machinery is costly

Types of geothermal systems

Direct from steam underground

Flash-steam systems take in deep-well hot water (high enthalpy) that is above the boiling point to heat clean water into steam in a heat exchanger

Binary systems that heat a low-boiling-point fluid like butane or propane to drive a closed-loop turbine12. LOW TEMPERATURE SYSTEMS

The classic use of earth/water is as a heat sink or source for air conditioning or heating

Pipes embedded in the earth carry refrigerant or water and conduct heat from the hotter to cooler substance

Since the earth (or water) has a high specific heat in comparison with air, there is good thermal transfer

In winter, heat is extracted from the earth by the chilled refrigerant, while in the summer, the hot refrigerant conducts heat to the earth

Houses have been built partially underground to moderate the winter and summer temperatures

Dennis Weaver built an Earthship house with used tires, aluminum cans, and stucco

13. ADVANTAGES

Think of all the advantages of geothermal energy when you have a lava flow in your backyard. You could dry your clothes, warm your house and heat your water. Even cook dinner if you wanted.

Well geothermal does help you do that without having to get so close to the source. if you are fortunate enough to live in an area with this geologic activity in play close under the surface of the Earth, you can harness this energy. Let's look at some of the advantages of geothermal energy.

1. No fuel is needed. For me to heat my home, I have to tap into the electric grid powered by Florida Power and Light. They get most of their electricity from The Power Plant that burns coal to run the generators. With geothermal energy, the fuel is already there. No need for coal or oil or wood.

2. No Pollution. Geothermal Energy produces no pollution. There are virtually no greenhouse gases given off. There is no pollution.

3.Relatively efficient. Geothermal energy is also very efficient, because after a site is located and a geothermal power plant is built, the efforts required to channel it are negligible.

14. 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]

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

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

http://www.acmehowto.com/howto/appliance/refrigerator/overview.htm

University 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

16. BIBILOGRAPHY Geothermal Power Wikipedia http://en.wikipedia.org/wiki/Geothermal_power

Geothermal Energy -Renewable Energy Acess.com http://www.renewableenergyworld.com/rea/tech/geothermal

Geothermal Energy Energy Efficiency and Renewable Energy -U.S. Department of Energy http://www1.eere.energy.gov/geothermal/

The Geothermal Energy Story -Energy Story http://www.energyquest.ca.gov/story/chapter11.html

Geothermal Energy Association http://www.geo-energy.org/

Department Of Mechanical Engineering, JITS

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