Impact of fuels on performance and efficiency of gas turbine power plants

A computational study to assess the performance of different gas turbine plants is presented in this paper. The work includes the effect of relative humidity, ambient inlet air temperature and types of fuels on gas turbine plants. Investigation also covers economic analysis and effect of fuels on emissions. Gas turbine frames of various ratings are used in gas turbine power plants in Saudi Arabia. 70 MWe GE-6101FA and 40 MWe GE-6561B frames are selected for the present study. GT PRO software has been used for carrying out the analysis including; net plant output and net efficiency, break even electricity price, break even fuel LHV price, carbon emissions etc., for a given location of Saudi Arabia. The relative humidity and ambient inlet air temperature have been varied from 30 to 45 % and from 80 to 100° F, respectively. Fuels considered are natural gas, diesel and heavy bunker oil. Simulated gas turbine plant output from GT PRO has been validated against an existing gas turbine plant output. It has been observed the simulated plant output is less than the existing gas turbine plant output by 5%. Results show that variation of relative humidity does not affect the gas turbine performance appreciably for all types of fuels. For 70 MWe frame, for a decrease of ambient inlet air temperature by 10 °F, plant net output and efficiency have been found to increase by about 5 and 2 %, respectively for all fuels. More specifically, plant net output and efficiency for natural gas are higher as compare to other fuels. For given 70 and 40 MWe frames, break even fuel price and electricity price have been found to vary from 2.03 to 2.54 US$/MMBTU and from 0.021 to 0.0254 US$/kWh respectively. It has been noticed that turbines operating on natural gas emit less carbon relatively as compared to other fuels.