Abstract: Multi-shaft and single-shaft configurations require full consideration of the unit performance, capital investment, operation and maintenance cost, operating convenience and the construction space. The analysis and comparison on the two types of configuration are conducted from three aspects, i.e., unit performance, unit configuration and environmental impacts. The unit performance deals with the gross power output, gross efficiency, auxiliary power demand, generator losses and shaft power. The unit configuration involves space limitations and expansion capability. And the environmental impacts include CO₂ and NO_x emissions. The results show that the single-shaft configuration is more suitable for the units with better requirements on unit performance, NO_x emissions, CO₂ emissions, start-up and expansion possibilities, while the multi-shaft configuration is better for the units with limited space but with higher requirement on steam turbine availability and reliability.

Key words: gas-steam combined cycle, single-shaft, multi-shaft, unit performance