Enhanced life cycle modelling of a micro gas turbine fuelled with various fuels for sustainable electricity production

In this study, exergy and life cycle-based enhanced environmental (EXEN) and enviro-economic (EXENEC) analyses are performed on a micro gas turbine, operated with natural gas and alternative mixtures of natural gas-ammonia and natural gas-methanol. A novel iterative method that considers compressor pressure, turbine pressure, mass flow rates in the turbomachines, and net power output (100±3 kW) is used for simulation. Exergy analysis is applied, after which EXEN and EXENEC are performed. The EXEN shows that 50% natural gas-50% ammonia combustion has the lowest CO and CO2 emissions, and that natural gas combustion has the lowest NO emissions. 50% ammonia combustion decreases CO2 emissions by 48.9%, CO emissions by 50.12%, exergy output by 58.62%, and increases NO emissions by 2.37% compared to the natural gas. For 50% secondary fuel combustion, the CO reduction for ammonia compared to methanol is 56.33%. Ammonia combustion creates more NO compared for every same fraction of methanol. The EXEN values for GHG-100 (GHG: greenhouse gas) are found to be as follows: 29,404 kgCO2eq/month (CO2eq: CO2-equivalent); 27,395 kgCO2eq/month and 25,797 kgCO2eq/month; 23,406 kgCO2eq/month; 21,501 kgCO2eq/month; 19,651 kgCO2eq/month for natural gas; 10%–50% ammonia, respectively. The released CO2eq prices (GHG-100) in a month are decreased from $1005 to $672 with ammonia combustion. Methanol combustion decreases EXEN values (GHG-100) from 29,400 kgCO2eq/month to 19,275 kgCO2eq/month and EXENEC values (GHG-100) to $659. Ammonia has better CO2 and CO combustion-based reduction than the same fraction of methanol, while methanol leads to a 0.27%–1.9% better life cycle-based environmental performance compared to other fuel options.