Thermo-economic analysis, working fluids selection, and cost projection of a precooler-integrated dual-stage combined cycle (PIDSCC) system utilizing cold exergy of liquefied natural gas

The technically efficient and cost-competitive design of an energy system is a key factor for its implementation. Precooler-integrated dual-stage combined cycle (PIDSCC) is a technically sound technology for recovering wasted cold exergy of Liquefied Natural Gas (LNG) during its regasification process, but its economic aspect remains unclear. In this paper, the thermo-economic model is built and the optimization procedure is applied, enabling to investigate the impacts of three key parameters. 10 common organic fluids are compared by using Capital Cost Per Power (CPP) as the optimization objective under different NG distribution pressures. Additionally, the mathematization of economic metrics (CPP and LCOE) at scaled-up capacities are realized and cost projection correlations are derived as a rule of thumb. Simulation results suggest that the occurrences of thermodynamically- and economically-optimal design points mismatch, and the economical optimum occurs at a lower pumped pressure. Within the selected fluids, high critical-temperature ones (70-150 degrees C, e.g., R290, R32, and R600) for the dual-stage ORC system lead to a lower CPP. The economic attractiveness of the PIDSCC system is more distinct at the low NG distribution pressure (6 bar) and medium to large scale applications (>1 MTPA). These insights enable engineers and project developers to design and implement this novel technology. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study presents a thermoeconomic model and optimization of a pre cooler-integrated dual-stage combined cycle technology, indicating its suitability for low NG distribution pressure and medium to large-scale applications, providing engineers and project developers with a pathway for implementing a new technology.