Performance of a Gas Turbine is largely dependent on inlet air temperature. Gas Turbines are constant volume machines. At a given shaft speed they always move the same volume of air. But the power output of a turbine depends on the flow of mass through it. This is precisely the reason why on hot days, when air is less dense, power output falls off. A rise of one degree Centigrade temperature of Inlet air decreases the power output by 1% and at the same time heat rate of the turbine also goes up. This is a matter of great concern to power producers. Many techniques have been developed to cool Inlet air to Gas Turbine. Traditionally, Gas Turbine inlet air has been cooled by either mechanical chillers or media type evaporative coolers. It is also important to note that power consumption to cool inlet air is also of concern since it decreases the net power output of a Gas Turbine. In mechanical Chiller auxiliary power consumption is very high compared to media type evaporative coolers. Efficiency of evaporative cooler largely depends on moisture present in the air. Higher the moisture in the air lesser the advantage from it. Use of Geo exchange Systems can provide energy-efficient cooling by using underground pipes, filled with water solution because the underground temperature is quite low than ambient temperature and relatively constant round the year. Circulation of water in closed loop pipe system will extract heat from the inlet air to Gas Turbine and disperse the same into the earth. This will reduce sensible heat from the inlet air, which gives more benefit. After reduction in dry bulb temperature we can take advantage from Fog system /Evaporative Cooler. Using a combination we can get much more benefit. This will not only improve power output but also improve the heat rate of the Gas Turbine.

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