Performance of gas turbine cycle for combined cycle power plant

Abstract

The gas turbine based power plant is characterized by its relatively low capital cost compared with the steam power plant. It has environmental advantages and short construction lead time. However, conventional industrial engines have lower efficiencies, especially at part load. One of the technologies adopted nowadays for efficiency improvement is the “combined cycle”. The combined cycle technology is now well established and offers superior efficiency to any of the competing gas turbine based systems that are likely to be available in the medium term for large scale power generation applications. This project has an objective to evaluate the performance of a combined cycle power plant for four different gas turbine cycles namely simple cycle, intercooled cycle, reheat cycle and intercooled cycle and reheat cycle. The proposed combined cycle plant would produce 300MW of power (200 MW from the gas turbine and 100 MW from exhaust gas temperature and resulting high thermal efficiency of the bottoming steam cycle. The optimal gas turbine (GT) cycle will lead to a more efficient combined cycle power plant (CCPP), and this will result in great savings. The initial approach adopted is to investigate independently the four theoretically possible configurations of the gas plant. Each alternative cycle was studied, aiming to find the best option from the standpoint of overall efficiency, installation and operational costs, maintainability and reliability for a combined power plant working on base load. When the investigation for this has done, a Matlab program and Microsoft Excel spreadsheet have been developed for each cycle to evaluate and compare the performance of different gas turbine cycles.