explain the working of a geo-thermal power plant.

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

Geothermal power uses the heat of magma below the Earth's crust, which comes from radioactive decay.

i)     Direct use

ii)    Electricity generation

iii)   Geothermal heat pumps

Electricity Generation

Geothermal electricity generation generally uses higher temperature geothermal resources (above 110 degree C).

1)  Vapor dominated source-direct steam conversion.

2)  Liquid dominated sources-to separate steam from the geothermal fluid.

3)  Low quality resources-using binary power plant.

4)  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.

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

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

7)  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 degree F) can be used to produce electricity.

8)  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.

Types of Geo-Thermal Power Plant:

1) Direct Dry Steam.

2) Flash and double flash steam cycle.

3) Binary cycle.

DIRECT DRY STEAM:

1) Steam plants use hydrothermal fluids that are primarily steam.

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

3) Steam eliminates the need to burn fossil fuels to run the turbine.

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

FLASH CYCLE:

1) Fluid (182 degree C) is sprayed into a tank held at a much lower pressure than th fluid.

2) The vapor then drives a turbine, which drives a generator.

3) 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:

1) Moderate-temperature water is used in it.

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

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

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

5) Most efficient for future.

MERITS:

1) It is 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) Maintance 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:

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 gurantee 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.