Effect of Ambient Temperature and Fuel Switching on the Performance and the Environmental Impact of Gas Turbine Plants: A Case Study of West Tripoli Gas Power Plant

Abstract

This paper analyses the performance and environmental impacts of gas turbine plants operating on diesel and natural gas. It provides a comprehensive assessment of how varying ambient temperatures and fuel type affect gas turbine operation and pollutant emissions. This is done under identical turbine inlet temperatures and net power to eliminate their effects and to enable a clearer comparison. Based on a case study of the Tripoli West 167 MW simple-cycle power plant, a thermodynamic model developed in Excel is used to simulate GT performance. Results indicate that as ambient temperature changes, net exergy destruction is primarily influenced by the exergy destruction changes in the turbine (~45%) and the compressor (~40%), although the combustor is responsible for over 80% of the net destruction in the cycle. The results also highlight the relationships between specific fuel consumption, net thermal efficiency, and pollutant emissions. For every 10 °C rise in ambient temperature, the net thermal efficiency declines by 1.55% and 1.5%, the specific fuel consumption rises by 1.57% and 1.52%, and pollutant emissions rise by 1.58% and 1.53% for diesel and natural gas, respectively. This may link the changes in net thermal efficiency and pollutant emissions to the specific fuel consumption. Switching from diesel to natural gas significantly reduces net exergy destruction (~73%), attributed to reduced combustor exergy destruction, and boosts overall thermal efficiency by about 1%. Switching to natural gas also reduces CO₂ emissions by (~24%) due to a lower carbon-to-hydrogen ratio (~15.2%) and lower fuel consumption (~10.2%). The emission factors determined by this study are 3.082 kg CO₂/kg fuel for diesel and 2.612 kg CO₂/kg fuel for natural gas. The change in emission factor between diesel and natural gas is similar to the change in carbon-to-hydrogen ratio between the two fuels (~15.2%). This relates the CO₂ emission factor to fuel chemistry. The findings suggest that using natural gas is preferable, especially in warmer months.