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Binary cycle

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Electricity generation in a vapor-dominated hydrothermal system.
Key: 1 Wellheads 2 Ground surface 3 Generator 4 Turbine 5 Condenser 6 Heat exchanger 7 Pump
  Hot water
  Cold water
  Isobutane vapor
  Isobutane liquid

A binary cycle power plant is a type of geothermal power plant that allows cooler geothermal reservoirs to be used than is necessary for dry steam and flash steam plants. As of 2010, flash steam plants are the most common type of geothermal power generation plants in operation today, which use water at temperatures greater than 182 °C (455 K; 360 °F) that is pumped under high pressure to the generation equipment at the surface.[1] With binary cycle geothermal power plants, 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 (3.4 MPa))[citation needed] 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.[2]

A binary vapor cycle is defined in thermodynamics as a power cycle that is a combination of two cycles, one in a high temperature region and the other in a lower temperature region.[3]

Introduction to Binary Cycles

The use of mercury-water cycles in the United States can be dated back to the late 1920s. A small mercury-water plant which produced about 40 megawatts (MW) was in use in New Hampshire in the 1950s, with a higher thermal efficiency than most of the power plants in use during the 1950s. Unfortunately, binary vapor cycles have a high initial cost and so they are not as economically attractive.[4]

Water is the optimal working fluid to use in vapor cycles because it is the closest to an ideal working fluid that is currently available. The binary cycle is a process designed to overcome the imperfections of water as a working fluid. The cycle uses two fluids in an attempt to approach an ideal working fluid.[4]

A modern binary cycle geothermal plant was recently built in McLean Virginia. LOC Co. sponsored this. LOC Co. is a family owned company which is run by Liv and Rocco Bognet and their child Christopher. The goal of LOC Co. is to give reduce the greenhouse gasses on our planet. With their binary cycle geothermal power plant, they give off no carbon dioxide as well as no other greenhouse gasses. Cite error: A <ref> tag is missing the closing </ref> (see the help page).

Dual Fluid

“Power is extracted from a stream of hot fluid, such as geothermal water, by passing the stream in heat exchange relationship with a working fluid to vaporize the latter, expanding the vapor through a turbine, and condensing the vapor in a conventional Rankine cycle. Additional power is obtained in a second Rankine cycle by employing a portion of the hot fluid after heat exchange with the working fluid to vaporize a second working fluid having a lower boiling point and higher vapor density than the first fluid.”[5]

Power Plants

There are numerous binary cycle power stations in commercial production.

Binary cycle power plants have a thermal efficiency of 10-13%.[9]

See also

References

  1. ^ "Geothermal Technologies Program: Hydrothermal Power Systems". Geothermal Technologies Program: Technologies. U.S. DOE Energy Efficiency and Renewable Energy (EERE). 2010-07-06. Retrieved 2010-11-02.
  2. ^ Scott, Willie (15 November 2010). "Geothermal Energy Power Plants and How They Produce Green Electricity". Bright Hub.
  3. ^ Çengel, Yunus A.; Michael A. Boles (2002). Thermodynamics: An Engineering Approach, Seventh Edition. Boston: McGraw-Hill. pp. Chapter 10. {{cite book}}: Unknown parameter |lastauthoramp= ignored (|name-list-style= suggested) (help)
  4. ^ a b [Çengel, Yunus A., and Michael A. Boles. "Chapter 10: Vapor and Combined Power Cycles."Thermodynamics: An Engineering Approach. 7th ed. Boston: McGraw-Hill, 2002. 557-89. Print.], additional text.
  5. ^ "DUAL FLUID CYCLE". United States, Patent No.3795103. 1974.
  6. ^ "Mammoth Pacific Geothermal Power Plant Honored with Environmental Award from State of California". Ormat. 20 August 2009.
  7. ^ "Steamboat Springs".
  8. ^ "Te Huka Geothermal Power Plant". Global Energy Observatory.
  9. ^ Ronald DiPippo (2007). Geothermal Power Plants, Second Edition: Principles, Applications, Case Studies and Environmental Impact. Oxford: Butterworth-Heinemann. p. 159. ISBN 0-7506-8620-0.
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