Gas power plant

GAS POWER PLANT

•         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.

MERITS:

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.

Demerits:

•           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.