Thermodynamic modeling and parametric study of a small-scale natural gas/hydrogen-fueled gas turbine system for decentralized applications

In this study a detailed thermodynamic model of a small-scale natural gas/hydrogen-fueled gas turbine system is presented. The thermodynamic model includes both a basic thermodynamic analysis and an exergy analysis. Exergy analysis aims on the identification of exergy destruction in the various system components. Specifically, it is investigated how hydrogen addition in the fuel supply can affect exergy loss. Off-design modeling is also implemented to realistically evaluate performance at part-load operation. A parametric study is conducted to examine the effect of hydrogen ratio on system performance. The hydrogen ratio is varied from 0 to 0.9, to examine the behavior of the developed model at different hydrogen contents. The results suggest that hydrogen addition to the natural gas fuel supply can change the operational behavior of the gas turbine cycle. Although net electrical efficiency is only marginally increased as hydrogen ratio is increased (0.347 vs. 0.356), the exergetic efficiency is more significantly affected, mainly due to the reduction of combustor losses as hydrogen content increases (0.338 vs. 0.360). Also, hydrogen addition has a positive effect in terms of carbon emissions, since even a tiny hydrogen injection at a hydrogen ratio of 0.1 (on a volumetric basis) results in a 6.1% reduction in CO2 emissions, as compared to methane-only fueling. Overall, the results suggest that even a small amount of hydrogen addition to the gas turbine cycle can have a significantly positive effect in terms of system efficiency and operational cost.