2. Content What is Geothermal Energy? The Geothermal Gradient Where is Geothermal Energy derived from? Applications of Geothermal Energy Geothermal Energy in India Harmful Effects Of Geothermal Energy Positive Attributes
3.
4. This geothermal energy originates from the original formation of the planet, from radioactive decay of minerals, and from solar energy absorbed at the surface.
5.
6. Where is Geothermal Energy derived from? Much of the heat is believed to be created by decay of naturally radioactive elements. An estimated 45 to 90 percent of the heat escaping from the Earth originates from radioactive decay of elements within the mantle. Heat of impact and compression released during the original formation of the Earth by accretion of in-falling meteorites. Heat released as abundant heavy metals (iron, nickel, copper) descended to the Earth's core.
7. 10 to 25% of the heat flowing to the surface may be produced by a sustained nuclear fission reaction in Earth's inner core. Heat may be generated by tidal force on the Earth as it rotates, since land cannot flow like water it compresses and distorts, generating heat. Some heat may be created by electromagnetic effects of the magnetic fields involved in Earth's magnetic field.
8. Heat generated due to radioactive disintegration: The major heat-producing isotopes in the Earth are potassium-40, uranium-238, uranium-235, and thorium-232. At the centre of the planet, the temperature may be up to 7,000 K and the pressure could reach 360 Gpa Because much of the heat is provided by radioactive decay, scientists believe that early in Earth history, before isotopes with short half-lives had been depleted, Earth's heat production would have been much higher. This extra heat production, which was twice that of present-day at approximately 3 billion years ago,would have increased temperature gradients within the Earth, increasing the rates of mantle convection and plate tectonics, and allowing the production of igneous rocks such as komatites that are not formed today.
9. Heat flows constantly from its sources within the Earth to the surface,so the earth loses heat on a daily basis. Geothermal energy is transported toward the crust by Mantle plumes; a form of convection consisting of upwellings of higher-temperature rock. The heat of the earth is replenished by radioactive decay at a rate of 30 TW. The global geothermal flow rates are more than twice the rate of human energy consumption from all primary sources.
10. Applications of Geothermal Energy:Direct Applications :Heating Direct heating in all its forms is far more efficient than electricity generation and places less demanding temperature requirements on the heat resource. Heat may come from co-generation with a geothermal electrical plant or from smaller wells or heat exchangers buried in shallow ground. If the ground is hot but dry, earth tubes or downhole heat exchangers can collect the heat. But even in areas where the ground is colder than room temperature, heat can still be extracted with a geothermal heat pump more cost-effectively and cleanly than it can be produced by conventional furnaces . Geothermal heat pumps can be used for space heating essentially anywhere in the world.
13. 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.
15. Binary cycle power plant A binary cycle power plantallows cooler geothermal reservoirs to be used than with dry steam and flash steam plants. They are used when the temperature of the water is less than 175 °C. Pumps are used to pump hot water from a geothermal well, through a heat exchanger, and the cooled water is returned to the underground reservoir. A second "working" or "binary" fluid with a low boiling point, typically a butane or pentane hydrocarbon, is pumped at fairly high pressure (500 PSI) through the heat exchanger, where it is vaporized and then directed through a turbine. The vapor exiting the turbine is then condensed by cold air radiators or cold water and cycled back through the heat exchanger.
18. 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.
21. Geothermal Energy in India Potential Geothermal provinces of India Source: Values from Geological Survey Of India on the basis of their research
22.
23. 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.
24. 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.
25.
26.
27.
28. Binary and Hot Dry Rock plants have no gaseous emission at all.
