Integrating a multigeneration system into a biogas-fueled gas turbine power plant for CO2 emission reduction: An efficient design and exergy-economic assessment

Integrating renewable sources with existing power plants represents a viable strategy for enhancing feasibility, reducing thermodynamic irreversibility, and lowering air pollution. This study employs a biomass digestion method to produce syngas, which feeds a post-combustion chamber to assist a methane-fueled Brayton cycle. An efficient heat design model is developed using the Engineering Equation Solver (EES), integrating a geothermal-powered trigeneration unit with the upper cycle to produce power, cooling, and potable water. The integrated scheme includes a flash-binary geothermal plant, a separation vessel desalination process, multi-effect desalination, and generator-absorber-heat exchange refrigeration units. Energy, exergy, and economic analyses are conducted to assess the thermodynamic and economic feasibility of the system. A multi-criteria optimization is conducted in two scenarios: power-freshwater and exergy-net present value (NPV), using an integrated Histogram Gradient Boosting Regression (HGBR) and Multi-Objective Particle Swarm Optimization (MOPSO) model. The first scenario showed a 55.37 % increase in net electricity output (2100.28 kW) and a 51.7 % improvement in freshwater generation (36.09 kg/s) compared to the base case. The optimum point revealed an exergy efficiency of 28.36 %, a total NPV of $5.703 M, and a payback period of 4.85 years. In the second scenario, an exergy efficiency of 29.52 %, an NPV of $4.41 M, and a payback period of 5.37 years are achieved. Based on the results, the first scenario demonstrates superior performance.