Multilayer perceptron-assisted multi-objective optimization of an integrated cryogenic biogas upgrading system for simultaneous liquid CO2, hydrogen, power, heating, and cooling production

Using biogas in an integrated multi-generation system is one of the possible solutions for optimizing the utilization of renewable energy, minimizing environmental effects, and enhancing resource efficiency. In the current project, a new multi-product energy setup using biogas is designed that co-produces liquid CO 2 , electric energy, hydrogen, cooling, and heating by combining the cryogenic biogas upgrading technology with a gas turbine, steam Rankine cycle, absorption chiller and water electrolyzer. This proposed design is a single-stage nitrogen refrigeration system with heat integration for high biomethane recovery and efficient liquefaction of CO 2 and utilization of waste heat. The setup is evaluated based on 4E (exergy, energy, economic and environmental) criteria. Furthermore, an AI-based multi-objective optimization method using Multilayer Perceptron (MLP), Grasshopper Optimization Algorithm (GOA) plus TOPSIS is proposed to optimize the operating conditions considering both thermodynamic and economic/environmental objectives concurrently. The suggested setup yields 3926 kW of electric energy, 2341 kg/h of liquid CO 2 , 10.08 kg/h of hydrogen, 2799 kW of cooling, 3236 kW of heating, with 58.22%, 27.56% and 22.2% energy, exergy, and electric efficiencies, separately. Economic analysis shows a period of payback by around 5.2 years, and optimized solution shows an exergy efficiency of 28.30%, CO 2 footprint of 0.093 kg/kWh, and specific product cost of 17.59 $/GJ. The outcomes reveal the designed integrated setup is capable of offering an efficient and viable solution for the high value utilization of biogas by simultaneously producing several energy carriers and products.