Exergy Analysis for Performance Optimization of a Steam Turbine Cycle

Exergy analysis of a 500 MWe steam turbine cycle is performed to identify the components that offer significant work potential saving opportunity. Criteria of performance relevant to the individual components are formulated. Exergy flows, exergy consumption due to irreversibilities and rational performance parameters for the turbine cycle and its components are computed by using plant operation data under different conditions. Energy efficiency of the turbine cycle is low due to large energy rejection, but the derived exergy efficiency of the turbine cycle is high due to low exergy rejection from the cycle. Part load operation exhibits lower energy efficiency due to higher energy rejection relative to net output. On the contrary, exergy rejection from the cycle relative to net output does not increase during low load operation. Results show that poor part load exergy efficiency is due to higher exergy destruction relative to net output. Higher pressure feed heaters deal with larger exergy and therefore, need more attention to improve cycle efficiency. Operation and maintenance decisions based on exergy analysis have proved to be more effective in reducing inefficiencies in operating power plant. Exergy-based approach of performance analysis will help practicing power engineers manage energy resources and environment better.