Performance enhancement of gas turbine by supercritical CO2 cycle construction: System and component two-level evaluation

Gas turbine (GT) can play a significant role in the new power system with high renewable energy penetration. This paper develops the supercritical CO2 power cycle (CPC) to improve its efficiency through waste heat recovery (WHR), and the integrated system is designed for large ship propulsion. An ideal WHR cycle perspective is drawn to guide the evolution of the CPC configuration, and the techno-economic model of these CPCs are established. Then, a system and component two-level evaluation framework with corresponding criteria is formed: through thermodynamic and multi-objective optimization and comparison, the layout with optimal comprehensive performance was identified; the conventional and advanced exergy analyses, as well as their comparison, were carried out to obtain the components' information. Results show that both the recuperative and the split-flow can substantially enhance the CPC's WHR capability, while the over-expansion has minimal effect. By integrating the CPC, the GT's efficiency can be improved by approximately 33 %. Multi-objective optimization reveals that the partial heating layout outperforms the recuperated layout in terms of overall performance. Specifically, despite having a similar levelized cost of electricity of 4.73 cents/kWh, its total heat recovery efficiency (THRE, 17.6 %) exceeds that of the latter by a margin of 14.2 %. The heater has the most considerable exergy destruction in the optimal layout, accounting for 19.3 %. With the current technology, the THRE can be increased to 25.5 % through component refinement. Conversely, the advanced exergy analysis indicates that the heater has a minimum improvement potential of 1.52 %. The turbine has the highest endogenous avoidable exergy destruction ratio of 31.8 %, which deserves focused development and investment.