A Comparison between steam injection and combined cycle power plant using exergy analysis

Abstract

The objective of this paper aims is to analyze the performance of a Siemens GT5-2000E gas power plant in West Tripoli using steam injection and combined cycle technologies from an exergy perspective to evaluate energy conversion efficiency and reduce thermal losses. The study relies on real operational data from the power plant. Two gas turbine units were simulated using Aspen Plus to apply the steam injection and combined cycle techniques, while an exergy analysis using the operational data of each system component was performed using Excel. The results showed that the steam injection and combined cycle technologies achieved different exergy efficiencies compared to a standard cycle gas turbine. The exergy efficiency of the two gas units in the conventional cycle was 55.19%. After applying the steam injection technique, the exergy efficiency increased to 74.82% at 15°C, reflecting an improvement of 35.6% compared to the conventional cycle. In contrast, the combined cycle technique recorded an exergy efficiency of 49.10%, representing a lower improvement of 10.1% compared to the conventional cycle. Exergy analysis also revealed that the combustion chamber was the largest contributor to exergy destruction in all cases, accounting for 40–50% of total losses. It can be concluded that the steam injection technique represents the most efficient option from an exergy perspective, as it achieves the highest improvement in energy conversion efficiency and the lowest energy losses compared to the combined cycle and the conventional cycle gas units.