Thermoeconomic optimization of a geothermal-assisted hybrid LNG and power generation system: Simulation, performance assessment, and sustainability insights

Abstract

This study investigates the optimization and economic analysis of a geothermal-assisted hybrid natural gas liquefaction (LNG) and power generation system, integrating geothermal energy to enhance efficiency and sustainability. The system's performance is evaluated using Aspen Plus simulations and numerical modeling, providing a comprehensive thermoeconomic assessment. Geothermal energy is utilized for two purposes: generating green electricity and reducing the energy demand for LNG production. Geothermal water, extracted at 130 °C and 100 kg/s, supplies heat to an absorption cooling system that precools natural gas to −45 °C before liquefaction. A geothermal power plant with 110 °C geothermal water generates 3000 kW of power, of which 1700 kW is utilized for the liquefaction process at 0.03 $/kWh. At the same time, excess electricity is managed through a power control unit. The system achieves an LNG production cost of 0.44 $/kg, with a liquefaction coefficient of performance (COP) of 0.74 and an exergy efficiency of 41.0 %. The idealized minimum work requirement is 460.5 kJ/kg, while practical evaluations indicate an actual work requirement of 1113 kJ/kg, highlighting actual operational constraints. The thermoeconomic assessment underscores the balance between technical efficiency and economic feasibility, demonstrating the potential of geothermal-assisted LNG for long-distance natural gas transportation. Integrating renewable geothermal energy enhances system efficiency and reduces operational costs, aligning with sustainable energy strategies. The model also aligns well with Engineering Equation Solver (EES) numerical simulations, presenting opportunities for further optimization through advanced modeling and artificial intelligence-based approaches. This study provides valuable insights for developing cost-effective and sustainable LNG technologies, offering a promising alternative for improving LNG production efficiency while leveraging renewable energy resources.