Multi-objective optimization of a biogas-fired gas turbine incorporated with closed Brayton and ejector power/cooling co-generation cycles

Fossil fuels have long been the primary source of energy for human consumption. However, with increasing population growth and industrialization, electricity demand continues to rise, necessitating a sustainable and clean energy supply to mitigate environmental damage and support global development. This research proposes a gas turbine-based power plant that utilizes renewable biogas as its fuel source. To enhance the plant's efficiency, the gas turbine is integrated with a closed Brayton cycle, complemented by compressor intake cooling. This cooling process is achieved through a combined power and ejector refrigeration unit, which recovers waste heat from the gas turbine. The energy, exergy, and economic performance of the proposed plant are thoroughly analyzed, with exergy efficiency and unit product cost serving as the objective functions for multi-criteria optimization. The results demonstrate that compressor intake cooling improves both thermodynamic and economic performance under all operating conditions. At the optimal design point, the system with intake cooling achieves an exergy efficiency of 39.38%, compared to 33.64% for the system without it. Additionally, while the system with intake cooling requires higher initial investment, it offers lower unit product costs, making it a more economically viable option.