Multi-objective optimization analysis on gas-steam combined cycle system with exergy theory

The gas-steam combined cycle, usually combined with a gas turbine, a waste heat boiler and a steam turbine, is widely used for higher efficiency and lower emissions. However, most analyses on the units are based on the first law of thermodynamics, ignoring the energy quality. In this paper, the combined cycle's exergy efficiency is calculated on each equipment in a 200 MW system with matrix form. The total cost model is then established based on exergy economics theory. With the purpose of higher efficiency, less cost and lower emission, three related models are then established as objective functions. NSGA II genetic algorithm is carried out to obtain a set of Pareto frontier solutions for this multi-objective problem. The optimized frontiers, or optimal parameters in gas-steam combined cycle unit, can be taken as operation guidance for high efficiency, low cost and low emissions as [52.35%, 15,866.726$/h, 232.93 kg/MWh]. Further, sensitivity analysis on the three objective functions is studied under different operating conditions. (C) 2020 Elsevier Ltd. All rights reserved.