Combined cycle power plants (CCPPs) are currently one of the most important options for the construction of new generating capacity as well as for the replacement and repowering of existing steam turbine power plant units and to improve their performances. The main purpose of this book is to study the effect of different operating parameters such as ambient temperature, compressor pressure ratio, air-fuel ratio, and turbine inlet temperature on the performance of the repowered combined cycle power plant by using full repowering single pressure HRSG with reheat and supplementary firing.