Critical relative humidity of evaporative cooling in CCPP based on thermodynamic and economic analyses

Abstract

A calculation and analysis to determine the feasibility of inlet air evaporative cooling systems for combined cycle power plant (CCPP) is carried out. According to the psychrometric chart, the effects of ambient temperature and relative humidity (RH) on the temperature drop of the inlet air across an evaporative cooling system are analyzed. The power differences between CCPP with and without an inlet air evaporative cooling system in different environmental conditions are investigated. Based on the thermodynamic and economic analyses, a new concept, the critical RH, is proposed to evaluate the feasibility and economics of CCPP with inlet air evaporative cooling system considering different ambient conditions. If ambient RH is lower than the critical value, an inlet air evaporative cooling system is suitable and economical for regions considered. Sensitivity analysis of the factors affecting the critical RH is also carried out. The critical RH varies with climatic condition, electricity price, fuel price and expected payback period (PBT).