ABSTRACT

This study presents an environmental and life cycle analysis of different gas turbine inlet cooling systems. The research objectives involves the parametric modelling of the basic inlet turbine system in terms of thermo-sustainability consideration; determination of the environmental effect of various turbine inlet cooling system; comparative analysis of the system with different turbine cooling methods; and performance of the life cycle analysis of the different cooling systems. A base turbine was considered for the analysis where such operating data as location ambient temperature, isentropic efficiencies of compressor and turbine, turbine inlet temperature, and compression ratio were obtained. Three turbine air cooling methods were considered; spray cooler and wetted media, fogging system technology and mechanical chiller system. Additionally, thermodynamic models were presented to cater for the sustainability of these cooling systems. Using a developed program source code, the results showed that the extent of sustainability depends directly on the amount of turbine inlet reduction achievable in consonance with the design requirements. The mechanical chiller (refrigerative method), sprayed cooling and fogging have a sustainability index (SI) of 2.243, 2.17 and 2.165 respectively. The base turbine system has the least Sustainability Index value of 2.057. The results points to significant increase in the sustainability of the system by employing different turbine inlet cooling. Furthermore, sensitivity analysis was performed to check the effect of basic operating variables on the system. The variation of ambient temperature on both energetic and exergetic efficiency in the plant demonstrates an overall decline in both energetic and exergetic efficiencies at increased ambient temperatures which is attributable to higher compressor work requirements at increasing ambient temperatures. Life Cycle Analysis (LCA) showed that the mechanical chillers (refrigerative) method gave the least with a value of 1651885753 mPts. From the results, the mechanical chiller (refrigerative method) of air cooling which achieved lowest inlet conditions, Sustainability Index (SI) of 2.243 and LCA result of 1651885753 mPts is recommended due to its least overall exergy destruction.