Energy, exergy and exergoeconomic analyses of gas-turbine based systems

Abstract

Gas turbines are the primary technology used for the purpose of power generation nearly everywhere. In this thesis, the Makkah Power Plant, running on a Brayton cycle, is considered for analysis. The peak demand for electric power in the City of Makkah occurs in the middle of the day during the summer and is almost double the off-peak demand. The plant employs turbines of two world renowned manufacturers. However, there are many mechanical and electrical issues related to the overall insufficient operation of the plant. From the balancing of mass, entropy, energy, exergy and cost equations, a greater understanding of the systems as well as their efficiencies is achieved. The parametric study and plant optimization are performed to investigate the effects of the variation of specific input parameters such as fuel mass flow rate, air volume flow rate and compressor inlet air temperature, on the overall operating efficiency of the system. Through this study, the overall plant energetic and exergetic efficiencies are increased by 20% and 12% respectively with cooling down the compressor inlet temperature to 10oC. Furthermore, exergy and exergoeconomic analyses are conducted to obtain that the largest exergy destruction occurs in the combustion chamber, followed by the turbine. The optimization results demonstrate that CO2 emissions can be reduced by increasing the exergetic efficiency and using a low fuel injection rate into the combustion chamber. Finally, this study will assist efforts to understand the thermodynamic losses in the cycle, and to improve efficiency as well as provide future recommendations for better performance, sustainability and lessen environmental impact.