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Re: [hreg] more efficient use of Natural gas to produce electricity

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  • chasmauch@aol.com
    Natural gas is used to generate electricity primarily in three ways: burning the gas in a boiler to make steam to drive the generator, using gas turbines to
    Message 1 of 4 , May 22, 2006
      Natural gas is used to generate electricity primarily in three ways: burning the gas in a boiler to make steam to drive the generator, using gas turbines to drive the generator directly, or a combination of the two, which is the most efficient. You can read about all 3 at this link; however the pertinent parts are copied below.

      Steam Generation Units

      Natural gas can be used to generate electricity in a variety of ways. The most basic natural gas fired electric generation consists of a steam generation unit, where fossil fuels are burned in a boiler to heat water and produce steam, which then turns a turbine to generate electricity. Natural gas may be used for this process, although these basic steam units are more typical of large coal or nuclear generation facilities. These basic steam generation units have fairly low energy efficiency. Typically, only 33 to 35 percent of the thermal energy used to generate the steam is converted into electrical energy in these types of units.

      A Centralized Gas Turbine Generation Station
      Source: National Energy Technology Laboratory, DOE

      Centralized Gas Turbines

      Gas turbines and combustion engines are also used to generate electricity. In these types of units, instead of heating steam to turn a turbine, hot gases from burning fossil fuels (particularly natural gas) are used to turn the turbine and generate electricity. Gas turbine and combustion engine plants are traditionally used primarily for peak-load demands, as it is possible to quickly and easily turn them on. These plants have increased in popularity due to advances in technology and the availability of natural gas. However, they are still traditionally slightly less efficient than large steam-driven power plants.

      A Gas Fired Turbine - The Size of a Locomotive
      Source: Office of Fossil Energy, DOE

      Combined Cycle Units

      Many of the new natural gas fired power plants are what are known as 'combined-cycle' units. In these types of generating facilities, there is both a gas turbine and a steam unit, all in one. The gas turbine operates in much the same way as a normal gas turbine, using the hot gases released from burning natural gas to turn a turbine and generate electricity. In combined-cycle plants, the waste heat from the gas-turbine process is directed towards generating steam, which is then used to generate electricity much like a steam unit. Because of this efficient use of the heat energy released from the natural gas, combined-cycle plants are much more efficient than steam units or gas turbines alone. In fact, combined-plants can achieve thermal efficiencies of up to 50 to 60 percent

      In a message dated 5/22/06 11:55:59 A.M. Central Daylight Time, kconlin@... writes:
      It will take more energy to compress the gas than you would recover when it
      expanded in the turbine.  Natural gas is not naturally pressurized except in
      isolated instances, it is compressed with huge compressors that use natural
      gas as the fuel to power the engines that run the compressors.

      Once it has expanded you would have to re-compress it before the next cycle,
      with a net loss of energy.

      Kevin Conlin
      Solarcraft, Inc.
      13130 Stafford Road, Suite 125
      Stafford, TX 77477-4536
      fax (281)495-0440

      -----Original Message-----
      From: refuge@... [mailto:refuge@...]
      Sent: Saturday, May 20, 2006 6:08 PM
      To: hreg@yahoogroups.com
      Subject: [hreg] more efficient use of Natural gas to produce electricity

      hello all,

           this may sound naive as I'm not 100% sure of all of the specifics of
      natural gas fired electric plants work but since the main concept is to burn

      natural gas to heat up water to make steam to spin the turbines which
      electricity... wouldn't it make sense to bypass the whole heating up water
      part and just increase the pressure on the gas to spin the turbines? and
      use the gas for something else... or, since it would be pressurized just use

      the same gas over and over... making less pollution and making everything in

      the process more efficient.... just my $.02... I would appreciate comments
      about this... 

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