Exergy and thermo-economic study of A 412 MW natural gas-fired combined cycle power plant

Abstract

Combined cycle power plants are highly favored for their superior power output and efficiency. However, evaluating and optimizing these plants require more than just first law-based energy analysis; a combination of energy, exergy, and thermoeconomic analyses is necessary. This thesis presents such an analysis for the 412 MW Haripur combined cycle power plant, utilizing over 3.7 million real-time operational data points collected over a year. This extensive dataset allowed for the examination of seasonal impacts on performance parameters and the development of a correlation table for key metrics. The analysis found that gas turbines (GT) perform optimally at lower ambient temperatures, while steam turbines (ST) achieve their highest efficiency in hot, dry conditions. The plant’s peak efficiency was 60.19% Exergy analysis identified the combustion chamber as the primary source of irreversibility, accounting for about 70% of total exergy destruction, with an exergoeconomic factor of 3.82%. To mitigate this, it is recommended to match the compressor outlet and fuel temperatures before combustion. Although the condenser is a major source of heat loss in energy analysis, exergy analysis showed it has a high exergoeconomic factor of 95.32%, indicating minimal economic loss per unit of exergy destroyed. The thesis concludes with key observations and recommendations for optimizing the power plant under various ambient conditions.