The application of novel techniques for gas turbine inlet-cooling that improve both the power and efficiency of the modern commercial steam-air-cooled gas turbine combined cycle power plants in hot and humid climates

Abstract

Increasing ambient temperature significantly reduces the efficiency and power output of the combined cycle power plant. Gas turbine (GT) inlet-cooling decreases air temperature at the inlet of the air compressor; thus, reduces the work of the compressor and increases the mass flow rate and power output. The steam-cooled GT has a higher output per kg of inlet air than the air-cooled GT; therefore, for the same power output, the mass flow rate and as a consequence the cooling load is lower for the steam-cooled GT. Accordingly, the impact of applying GT inlet-cooling on the performance of the combined cycle is expected to be different for the steam-cooled GT from that for the air-cooled GT. For hot and humid climates, the typical GT inlet-cooling techniques of evaporative, inlet-fogging, and desiccant-cooling are not effective while absorption and refrigeration GT inlet-cooling systems consume significant amounts of energy, which influence the efficiency and power output. In this paper, novel GT inlet-cooling techniques that take advantages of the process air and exhaust heat energies are introduced. The commercial STAG 107H steam/air-cooled GT combined cycle with such innovative GT inlet-cooling systems are modeled. The effectiveness of the novel cooling techniques is compared with that of the available GT inlet-cooling systems of inlet-fogging, refrigeration, and absorption. The impacts of varying ambient temperature and relative humidity on the performance of the commercial combined cycle with the different GT inlet-cooling techniques are presented, compared, and the results are discussed. The results indicate that the introduced innovative techniques for GT inlet-cooling are the most suitable for hot and humid climates with improvements of up to 1.2 percentage point in the combined cycle efficiency and 1.4% in the power output when compared with the refrigeration and absorption GT inlet-cooling systems.