Combustion turbines in cogeneration (combined heat & power) and combined-cycle systems are the most energy efficient systems for fossil fuel energy utilization and power generation, respectively. Therefore, for reducing carbon footprint of energy utilization and power generation, it is important to maximize the utilization of these systems. This approach allows minimization of electric energy from less energy efficient systems such as combustion turbines in simple-cycle and steam-turbine systems. When the full potentials of cogeneration and combined-cycle systems have been utilized, simple-cycle combustion systems should be used next because these are, generally, more energy efficient than the steam-turbine based power plants. Unfortunately, during hot weather just when power demand and market value/price of electric energy are high, output capacity of all combustion turbine systems decreases by as much as 30% of the rated capacity (at the ISO temperature of 59F). Hot weather also decreases the energy efficiency of all combustion turbine systems by as much as 5%. Cooling the inlet air to combustion turbines is a well recognized approach for preventing the loss of power output capacity and reduction in energy efficiency of all combustion turbine systems. Several technologies are commercially available for this application. This paper focuses on the use of hybrid cooling systems, which incorporate two or more cooling technologies (instead of a single technology) that are used in sequential processing. The paper discusses the pros and cons of the hybrid systems and includes some examples of the combustion turbine systems that have been successfully using some of the hybrid systems for turbine inlet cooling.

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