Final answer:
The efficiency of a gas turbine depends primarily on the temperature of the air before it enters the turbine, with a higher inlet air temperature leading to greater energy output and efficiency.
Step-by-step explanation:
The efficiency of a gas turbine depends primarily upon the temperature at which the air can be raised before it enters the turbine. Increasing the inlet air temperature maximizes the energy output from the turbine because the energy that can be extracted from the gas is a function of the temperature difference between the high-temperature inlet and the lower-temperature exhaust. The highest possible temperature of the hot reservoir (hot side of the turbine apparatus) and the lowest possible temperature of the cold reservoir increase the efficiency of a heat engine, as stated by the second law of thermodynamics.
A higher temperature before entering the turbine means that the gas can do more work and thus, produce more power. A similar principle is observed in other cycles such as the Otto cycle and the functioning of heat engines, where the greatest efficiencies are obtained with the greatest possible temperature difference between the hot and cold reservoirs. Although a regenerator is used in a Stirling engine to improve thermal efficiency, in the context of gas turbines, the critical factor is the temperature elevation before entering the turbine section itself.