Chapter: Mechanical Engineering : Power Plant Engineering

Gas power plant

A gas power plant uses gas turbine as the prime mover for generating electricity.


         A gas power plant uses gas turbine as the prime mover for generating electricity.


           It uses natural gas or kerosene or benzene as fuel.


           Gas plant can produce only limited amount of the electricity.


         Efficiency of the plant is only 35%


           Generally a gas plant is expensive to operate.



         Hence it is usually installed with steam power plant in closed combined cycle.


         It is generally used in combination with steam/thermal power plant during peak load


         When the gas power plant is combined with thermal/steam power plant efficiency of the plant is up to 60% - 70%



Layout of the Gas turbine Power plant:


Combustion and generation of electricity:


         Gas turbine draws clean air into through air filter from atmosphere, with the help of a compressor.


           During the compression pressure of the air is increased.


         Compressed air is passed through to a combustion chamber along with fuel (Natural gas).


The air fuel mixture is ignited at high pressure in the combustion chamber.



           Combustion takes place.


         The generated hot gas of compression is passed through the gas turbine.


         Hot gases expand, and the turbine blades are connected to the turbine shaft are rotated.


         The turbine shaft which is coupled to the shaft of the electrical generator at the other end also rotates and drives the electrical generator.


         A portion of the energy developed by the hot gases through the gas turbine is used to run the compressor.


         The residual hot gases from gas turbine are passed through a heat exchanger (heat recovery steam generator)


         The heat exchanger produces steam with high pressure with the help of a steam boiler.


           The steam is allowed to expand in the steam turbine.


         when it passes through the turbine blades, the turbine shaft is rotated. The shaft is coupled to the generator, which generates electricity.


         Gas turbine and steam turbine combination enables increased power generation.


Transmission and distribution :


         The generated electricity from both gas and steam turbines is fed to the step up transformer where its voltage is increased.


   Then the electricity is conveyed through transmission lines for distribution.



Natural gas is readily available.


           Setting up cost can be reduced if the plant is installed near the source of natural gas.


           Less gas storage cost


           Less space occupation.


           Compared to steam power plant, smaller in size.


         Low operating cost.


           Low maintenance cost.


         No standby losses.


         Cheaper fuels like natural gas.



•           Gas turbine has low thermal efficiency.


•           Has starting problem.


•           Efficient only in combined cycle configuration.


•           Temperature of combustion chamber is too high, which results in shorter life time.


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Mechanical Engineering : Power Plant Engineering : Gas power plant |

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