Exergy, economic, and water consumption perspectives in the comparative assessment of inlet air cooling methods

Abstract

This study investigates the impact of three inlet air cooling techniques, media evaporative cooling, fogging systems, and absorption chillers, on the performance of a three-block combined cycle power plant with a total capacity of 1434 MW in Iran. The analysis specifically focuses on a single block comprising two gas turbines coupled with one steam turbine. Thermodynamic and economic evaluations were conducted using the ThermoFlow and EES software platforms. The exergy efficiency was evaluated at two ambient temperatures, 20 °C and 30 °C, under a constant relative humidity of 25 %. Higher efficiency improvements were observed at 30 °C, with values of 0.6 %, 1.7 %, and 2.6 % for media evaporative cooling, fogging, and absorption chillers, respectively. Under the design conditions of 40 °C ambient temperature and 25 % relative humidity, all three cooling systems also enhanced power generation efficiency and capacity. The absorption chiller achieved the highest net output increase, 45 MW, followed by fogging, 30 MW, and media evaporative cooling, 26 MW. The corresponding demineralized water consumption rates were 15, 16.5, and 36 m³/h, respectively. Economically, the media evaporative system achieved the shortest payback period of 2.7 years, while the absorption chiller showed the longest at 6.8 years. Under arid climate conditions, the media evaporative system demonstrated superior performance in terms of cost-effectiveness and environmental impact. Conversely, in high-humidity environments, the absorption chiller provided the greatest enhancement in turbine performance. By delivering a comprehensive, multi-criteria assessment of efficiency, cost, and water resource utilization, this research contributes valuable insights toward the sustainable optimization of large-scale combined cycle power plants.