Modeling and thermo-economic optimization of a new multi-generation system with geothermal heat source and LNG heat sink

LNG re-gasification process usually occurs through heat exchange with seawater, causing a large amount of exergy destruction. However, in this study, this process is employed as the heat sink of a geothermal driven multi-generation system. Because of the high temperature difference between the heat source (geothermal fluid) and the heat sink (LNG re-gasification process), a cascade of two organic Rankine cycles is placed between them. The system also includes an absorption refrigeration cycle and a PEM electrolyzer to form an efficient multi-generation system. A comprehensive analysis is carried out to assess the performance of the system both thermodynamically and economically. Furthermore, the paper presents a parametric study to illustrate the influences of major parameters on the system performance. To simultaneously optimize total cost rate, hydrogen production capacity, and exergy efficiency of the system, a multi-objective optimization procedure is developed (through coupling Genetic Algorithm with Artificial Neural Network) and applied to the system. Consequently, a system design with a total cost rate of 423.5 ($/hr), hydrogen production capacity of 276.1 (kg/hr), and exergy efficiency of 24.92% is obtained as the optimal solution. The proposed system shows great improvements in cooling, power generation, and hydrogen production capacities compared to literature.