The marketplace for electric power has become highly dynamic and competitive in nature in the backdrop of deregulation of power generation, declining fuel reserve margins, environmental regulations, climatic temperature extremes and the introduction of Availability Based Tariff (ABT). In such an environment, having the flexibility to augment gas turbine power output during periods when there is high tariff rates is of paramount importance to the profitability of the utilities.
Efficient, clean and less expensive to implement than most other alternatives, combined cycle power plants offer a blend of operational attributes that makes it the best choice for power production. The generated power and efficiency of gas turbine plants depend on the temperature of the inlet air. At high ambient temperatures, a power loss of more than 20%, combined with a significant increase in specific fuel consumption, compared to ISO standard conditions (15 C), can be observed.
The adverse effect of high ambient air temperatures on the power output of a gas turbine is twofold: as the temperature of the air increases, the air density and, consequently, the air mass flow decreases. The reduced air mass flow directly causes the gas turbine to produce less power output. Also, the higher intake-air temperature results in an increase of the specific compressor work and, therefore, in a further reduction of the power output.
Depending on the type of the gas turbine, the electric output will decrease by a percentage between 6% and more than 10% for every 10°C of intake-air temperature increase also there is a corresponding loss in the efficiency. The straightforward conclusion from the above discussion is that at temperatures of 2535 °C, common in Southern part of the country specially Kerala and 20-45°C in the northern part of the country where a large number of gas turbines are used for electricity generation, there is a power loss of more than 20%, combined with a significant increase in specific fuel consumption, compared to ISO standard conditions (15 C).