Energy Assessment of a Combined Cycle Power Plant through Empirical and Computational Approaches: A Case Study ^†

Energy management on the demand side is an important practice through which to address the challenge of energy shortage. In Pakistan, power plants have no specific energy management practice and a detail energy audit is normally observed as a one-time estimation that does not give significant information. In this study, an energy audit of a combined-cycle gas turbine power station was conducted and empirical data were compared with those obtained through a model developed in ASPEN, a simulation software that forecasts process performance. Next, an optimization tool was used to modify the ASPEN results and a comparison was drawn to estimate the amount of energy saved. It was found that compressor power consumption can be decreased up to 14.68% by increasing the temperature of compressed air from 320.2 °C to 423.79 °C for gas turbines. The output of gas turbines can be enhanced up to 13.5% and 21.4% with modelled and optimized data, respectively, using a multistage air compressor and multistage expansion. The calculated efficiency of the steam turbine was found to be 30.4%, which is 27.61% less than that of its designed efficiency. Steam turbine efficiency can be increased by 5% using a variable-speed water pump, leading to an estimated energy-saving potential of 8–9%. The combustion efficiency of gas turbines is not only important for higher turbine power output but also for better steam generation through heat-recovery steam generators in case of combined-cycle operations. The overall steam turbine efficiency is estimated to have increased by 19.27%, leading to a 12.68% improvement in combined efficiency.