Advanced exergy analysis and multi-objective optimization of dual-loop ORC utilizing LNG cold energy and geothermal energy

Cascading utilization is an effective strategy for enhancing the efficiency of geothermal power generation. This study proposes a novel dual-loop ORC-LNG system integrated with geothermal power generation and LNG cold energy recovery to efficiently exploit both geothermal and LNG cold energy. Energy, exergy, and thermo-economic models, along with an optimization framework combining NSGA-II and entropy-weighted TOPSIS, were developed. Advanced exergy analysis was employed to elucidate the interaction mechanisms between components and assess the optimization potential. The results indicate that the maximum net output power and thermal efficiency of the proposed system were 294.1 kW and 34.2 %, respectively, representing increases of 43.3 % and 63.7 % in thermal efficiency and net output power compared to the dual-loop ORC system. The thermodynamic performance was found to improve when working fluids with lower specific heat capacities and latent heats of vaporization were selected, as net output power was more sensitive to the working fluid flow rate. Additionally, the study revealed that the avoidable endogenous exergy destruction in the dual-loop ORC and dual-loop ORC-LNG systems was 38.2 % and 23.4 %, respectively, while unavoidable exogenous exergy destruction was primarily attributed to the irreversibility of heat transfer.