Geothermal Power Plant

Group Members:

Aashish Kumar – 11BEE1076Aryan Chhabra- 11BEE1112Antony Albert Raj I – 11BEE1055Arvind Kumar – 11BEE1092Irfan Khan – 11BEE1013Shreyansh Vats – 11BEE1033Nisha Bhagat – 11BEE1009Shyamla Kumari – 11BEE1129

INTRODUCTION

What is Geothermal Energy ?Geothermal Energy is thermal energy generated and stored in the earth.Thermal energy determines the temperature of the matter.Earth’s geothermal energy originates from the original formation of the Planet and from radioactive decay of minerals.

Geothermal Power Plant uses superheated water to generate electricity.It is a most efficient way or we can say a much better way to generate electricity because they require no raw materials and having little or no impact on the environment

Why is geothermal energy a renewable resource?Because its source is the almost unlimited amount of heat generated by the Earth's core.

How much does geothermal energy cost per kilowatt-hour (kWh)?At The Geysers, power is sold at $0.03 to $0.035 per kWh. A power plant built today would probably require about $0.05 per kWh.

Where is geothermal energy available?Hydrothermal resources - reservoirs of steam or hot water - are available primarily in the western states, Alaska, and Hawaii. However, Earth energy can be tapped almost anywhere with geothermal heat pumps and direct-use applications. Other enormous and world-wide geothermal resources - hot dry rock and magma, for example - are awaiting further technology development.

What we all know about Geothermal power plant ?

Current worldwide installed capacity is 10,715 megawatts(MW), with the largest capacity in the United States (3,086 MW).

India has announced a plan to develop the country's first geothermal power facility in Chhattisgarh.

Economically Geothermal power requires no fuel, it is therefore immune to fuel cost fluctuations.

Geothermal power is considered to be renewable because any projected heat extraction is small compared to the Earth's heat content. The Earth has an internal heat content of 1031 joules.

Further, due to its low emissions geothermal energy is considered to have excellent potential for mitigation of global warming.

Geothermal Hotspots

The areas in the world with the higher underground temperatures are regions with active volcanoes or geologically young volcanic events.

These “hot spots” occur at tectonic plate boundaries or where the earth’s crust is thin enough to let the heat through.

The Pacific Rim, with its many active volcanoes, has many hot spots, along with Alaska, Hawaii, and much of the western United States.

These regions are also seismically active with earthquakes and magma movement, which breaks up rock structures and allows water to circulate. As the water rises to the surface, natural hot springs and geysers occures.

WORLDWIDE GEOTHERMAL HOTSPOTS

WORLD GEOTHERMAL PROVINCES

Conversion of Geothermal Energy

Geothermal power uses the heat of magma below the Earth's crust, which comes from radioactive decay Direct useElectricity generationGeothermal heat pumps

Electricity GenerationGeothermal electric power generation generally uses higher temperature geothermal resources (above 110◦C)

– Vapour dominated sources – direct steam conversion

– Liquid dominated sources – to separate steam from the

geothermal fluid

– Low quality resources – using binary power plant

• Electricity generation requires high temperature resources that can only come from deep underground. The heat must be carried to the surface by fluid circulation, either through magma conduits, hot springs, hydrothermal circulation, oil wells, drilled water wells, or a combination of these.

• Away from tectonic plate boundaries the geothermal gradient is 25-30°C per km of depth in most of the world, and wells would have to be several kilometers deep to permit electricity generation.

• The quantity and quality of recoverable resources improves with drilling depth and proximity to tectonic plate boundaries

Geothermal Electricity Productioncontinued..

• Heat from the earth—geothermal energy—heats water that has seeped into underground reservoirs. These reservoirs can be tapped for a variety of uses, depending on the temperature of the water. The energy from high-temperature reservoirs (225°-600°F) can be used to produce electricity.

• In the United States, geothermal energy has been used to generate electricity on a large scale since 1960. Through research and development, geothermal power is becoming more cost-effective and competitive with fossil fuels.

• There are currently three types of geothermal power plants:

Layout of a Geothermal Plant

To harness energy ,large holes have to be dug into the earth until a geothermal hotspot is found.Pipes are inserted inside these holes through which water is sent and steam output is obtained.The production involves two process 1) Converting Geothermal energy into Mechanical energy 2) Converting Mechanical Energy into Electrical Energy

The success of the energy production depends on the temperature of the plant which depends on the temperature of the rocks in earth.The water is sent through the injection well and reaches the rocks and then hot water comes from the production well.The steam that comes out of the mixture might have dissolved brine and some dust particles.

Process Flow

Due to the high pressure when it reaches the topmost of the earth surface it is converted into steam.The separator is the place where steam that comes from the earth is made clean by removing the brine and dirt so that they do not damage the turbine blades.The high pressure and low pressure steam runs the turbine.The generator is coupled with turbine to produce electricity.The condensor is a phase changer where the steam output of the turbine is given to the condensor and gets converted to hot water.This hot water is then sent to the cooling tower where it loses it heat and then sent to the geothermal reservoir for further production of steam.

TYPES OF GEO-THERMAL POWER PLANT

• DIRECT DRY STEAM• FLASH AND DOUBLE FLASH STEAM CYCLE• BINARY CYCLE

DIRECT DRY STEAM

• Steam plants use hydrothermal fluids that are primarily steam.

• Steam goes directly to a turbine, which drives a generator that produces electricity.

• Steam eliminates the need to burn fossil fuels to run the turbine.

•  These plants emit only excess steam and very minor amounts of gases.

FLASH CYCLE• Fluid(182°C) is sprayed

into a tank held at a much lower pressure than the fluid.

• The vapour then drives a turbine, which drives a generator.

• If any liquid remains in the tank, it can be flashed again in a second tank (double flash) to extract even more energy.

BINARY CYCLE

•  Moderate-temperature water is used in it.

• Hot geothermal fluid and a secondary fluid with a much lower boiling point than water pass through a heat exchanger.

• Heat from the geothermal fluid causes the secondary fluid to flash to vapour, which then drives the turbines.

• Because this is a closed-loop system, nothing is emitted to the atmosphere.

• Most efficient for future.

E X T R A C T I O N W E L L

• The function of this extraction well is only to pump up the hot liquid(here water) from the reservoir.

• This well serves as the feed to the separator.• It carries the supply from the reservoir that is the original

mixture of water(as mist) and the steam(the vapor).

I N J E C T I O N W E L L

1. The basic idea behind an injector is to inject, or recycle the fluid (generally water) back to the reservoir to complete the loop.

2. The injected fluid enhances the transmissivity of the rocks and maintains the reservoir fluid.

3. The injection well has lines coming out from the separator as well as the condenser and the cooling tower which finally connect together to the main pipeline back to the reservoir.

4. Also, if the water is to be used for any other purpose than electricity generation, the supply can be taken from the injection wells as well (i.e. Apart from that from the reservoir).

INJECTION AND EXTRACTION WELLS

SEPARATOR

• The purpose served by the Vapor-liquid separator(Or simply the separator) is to separate the vapor-liquid mixture.

• For normal cases, this purpose is served by the gravity.• The inlet valve feeds the separator with the mixture through the inlet

diffuser(or the distributor).• The mixtures gradually moves up towards the vapor outlet. During this

process, a large amount of the water content condense-off and fall below. If some amount of water droplets remain in the vapor, they strike the de-entrainment mesh pad and fall back.

• The water is then taken off through the outlet.• The liquid level control monitors the level of liquid in the separator and

maintains the pressure required for it to operate.

SEPARATOR SCHEM ATICS

STEAM TURBINE

Wayang Windu Geothermal power plantOutput: 110MW Inlet steam pressure: 1.02 MpaInlet steam temperature: 181 CExhaust pressure: 0.012MpaSpeed: 3000 rpm

High efficiency blades: increase the efficiency by 3 %.Reaction type blades: assure good damping.Casing: single shell construction: This construction secure the vibration stability of the turbine rotor.Drum type construction: Deposition of corrosive components: eliminated.Possibility of stress corrosion cracking: eliminated

GeneratorCooling system: Totally controlled water to air.

Ventilation : Self ventilation

Excitation: Brushless Excitation

Speed: 3000 rpm

Output: 137,500 kVA

Power Factor: 0.8 lag

Condenser And NCG removal system

• Condensor:

- Pressure maintained at 0.01 Mpa by NCG removal system.

- NCG (Non Condensable Gas) System: 2 Stages

1. Two 100% capacity ejectors.

2. Two 100% cooling water pumps.

Circulating water system

• Consist of two 60% capacity circulating water pumps.

• Discharge condensate from the condensor hotwell to the cooling towers.

APPLICATIONS

Geothermal prawn farming

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.

Geothermal waste heat is used at Taupō to cultivate giant river prawns which require warm temperatures (24–28ºC).

This is a good example of what is known as ‘cascade use’, where geothermal heat has a function past its primary purpose. Cascading improves the overall efficiency of a resource by using its waste products. In the case of the prawn farm, cascading also reduces the discharge of hot water into the river, where it can harm aquatic life.

Geothermal energy is also used to heat sidewalks and roads to prevent freezing in the winter. Most recently, the Netherlands began using geothermal energy to keep bike lanes from freezing in the wintertime.

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

This includes a large greenhouse (0.8 hectares) for growing orchids for export, and another set up to grow capsicums with heat from the Kawerau geothermal field.

OTHER APPLICATIONS:Providing Heat For Residential And Commercial Use.

Electricity Generation

Food Processing

Paper processing

Aquaculture

MERITS OF GEOTHERMAL POWER PLANT

1)  It is a renewable source of energy.2)  By far, it is non-polluting and environment friendly. 3)  There is no wastage or generation of by-products.4)  Geothermal energy can be used directly. In ancient times, people used this source of energy for heating homes, cooking, etc.

5)  Maintenance cost of geothermal power plants is very less.6)  Geothermal power plants don't occupy too much space and thus help in protecting natural environment. 7)  Unlike solar energy, it is not dependent on the weather conditions.

DEMERITS OF GEOTHERMAL POWER PLANT

1)  Only few sites have the potential of Geothermal Energy.2)  Most of the sites, where geothermal energy is produced, are far from markets or cities, where it needs to be consumed.3)  Total generation potential of this source is too small.4)  There is always a danger of eruption of volcano.

5)  Installation cost of steam power plant is very high.6)  There is no guarantee that the amount of energy which is produced will justify the capital expenditure and operations costs.7)  It may release some harmful, poisonous gases that can escape through the holes drilled during construction.

THANK YOU