Geo thermal Power plants

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All about Geothermal power plants

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Geo thermal Power plants

  1. 1. Geothermal Energy Presented by Vijay Marcel D I year M.Tech(R.E)
  2. 2. Introduction-Geothermal Energy • Geothermal Energy is the thermal energy generated and stored in earth • U.S geological survey defines geothermal source as “all of the heat stored in the earth’s crust above 15oC to a depth of 10 Km”.
  3. 3. Geothermal sources • Five general categories of geothermal resources has been identified • Hydrothermal convective systems • Vapor dominated or dry steam fields • Liquid-dominated system or wet steam fields • Hot-water fields • Geopressure resources • Hot dry rocks • Magma resources • Volcanoes
  4. 4. Geothermal systems • In commercial use there are essentially five types of geothermal systems. – Dry steam power plants – Single flash power plants – Double flash power plants – Multiple flash power plants – Binary power plants
  5. 5. Dry steam power plants
  6. 6. • Dry steam power plants extract heat at 200 oC and 4-8MPa • Water is injected to the geothermal zone and the heat transported from the hot rocks by convection of water in porous medium. • Steam drives the turbine,which coupled with the generator produces electricity. • The steam is condensed and pumped back into the geothermal zone.
  7. 7. Single flash power plant
  8. 8. • The water in the reservoir is at 230oC and 4MPa • The liquid originates mainly from depth of 600m to 1400m and is flashed into mixture of steam and brine at the surface. • After passing through a cyclone separator to remove the water the steam is supplied to the turbine,which coupled with the generator to produce electricity • The brine withdrawn from cyclone separator after flashing is injected to the well
  9. 9. Double flash power plant
  10. 10. • Double flash power plant is similar to that of single flash power plant. • The brine from the I stage cyclone separtor is admitted to a II second stage low pressure cylone separator • The steamfrom the II stage cyclone separtor is supplied to a low pressure turbine • The remaining spent brine is reinjected to the ground.
  11. 11. Binary cycle power plant
  12. 12. • In reservoirs where temperatures are typically less than 220oC (430oF). but greater than 100oC (212oF). binary cycle plants are often utilised. • The reservoir fluid (either steam or water or both) is passed through a heat exchanger. • It heats a secondary working fluid which has a boiling point lower than 100oC (212oF). This is typically an organic fluid such as Isopentane, which is vaporised and is used to drive the turbine. • The fluid in a binary plant is recycled back to the heat exchanger and forms a closed loop. • The cooled reservoir fluid is again re-injected back into the reservoir
  13. 13. Hot Dry Rock or Enhanced geothermal systems
  14. 14. • Wells are drilled 3-6 km into crust • water is pumped into hot, crystalline rock via an injection well, becomes superheated as it flows through open joints in the hot rock reservoir, and is returned through production wells. • At the surface, the useful heat is extracted by conventional processes, and the same water is recirculated to mine more heat.
  15. 15. Advantages of Geothermal power plant • Unlike solar energy or wind energy, it is not dependent on the weather conditions. • Clean source of power. • Less area is required. • Unhindered production of power. • Additional capacity can be added to produce more power and is thus flexible. • Maintenance cost of geothermal power plants is very less.
  16. 16. Technological Issues • Geothermal fluids often contain significant quantities of gases such as hydrogen sulphide as well as dissolved chemicals and can sometimes be acidic and is corrosive. • Well casings and pipelines can suffer corrosion and or scale deposition, and turbines, especially blades can suffer damage leading to higher maintenance costs and reduced power output. • These potential problems can be overcome by a combination of utilizing corrosion resistant materials, careful control of brine temperatures, the use of steam scrubbers and occasionally using corrosion inhibitors.
  17. 17. • Geothermal plants results in emission of huge quantities of waste heat ,which can damage fisheries. • possible remedies include reinjection of surplus cooling tower water and the generation of additional power by means of binary fluid cycles. • The withdrawal of huge quantities of underground fluid from wet field can cause substantial ground subsidence. Re-injection of the fluid is the best solution to the problem
  18. 18. Thank you

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