Gas Turbine Power Plant

Gas Turbine Power Plant:

A generating station which employs gas turbine as the prime mover for the generation of electrical energy is  known as a  gas turbine power plant

In a gas turbine power plant, air is used as the working fluid.The air is compressed by the compressor and is led to the combustion chamber where heat is added to air, thus raising its temperature.Heat is added to the compressed air either by burning fuel in the chamber or by the use of air heaters.The hot and high pressure air from the combustion chamber is then passed to the gas turbine where it expands and does the mechanical work.The gas turbine drives the alternator which converts mechanical energy into electrical energy.It may be mentioned here that compressor, gas turbine and the alternator are mounted on the same shaft so that a part of mechanical power of the turbine can be utilized for the operation of the compressor. Gas turbine power plants are being used as standby plants for hydro electric stations, as a starting plant for driving auxiliaries in power plants etc.

Advantages:

(i) It is simple in design as compared to steam power station since no boilers and their auxiliaries are required.

(ii) It is much smaller in size as compared to steam power station of the same capacity.This is expected since gas turbine power plant does not require boiler, feed water arrangement etc.

(iii) The initial and operating costs are much lower than that of equivalent steam power station.

(iv) It requires comparatively less water as no condenser is used.

(v) The maintenance charges are quite small.

(vi) Gas turbines are much simpler in construction and operation than steam turbines.

(vii) It can be started quickly form cold conditions.

(viii) There are no standby losses.However, in a steam power station, these losses occur because boiler is kept in operation even when the steam turbine is supplying no load.

Disadvantages:

(i) There is a problem for starting the unit.It is because before starting the turbine, the compressor has to be operated for which power is required from some external source.However, once the unit starts, the external power is not needed as the turbine itself supplies the necessary power to the compressor.

(ii) Since a greater part of power developed by the turbine is used in driving the compressor, the net output is low.

(iii) The overall efficiency of such plants is low (about 20%) because the exhaust gases from the turbine contain sufficient heat.

(iv) The temperature of combustion chamber is quite high (3000oF) so that its life is comparatively reduced.