Performance assessment of sCO2- and organic fluid based cycles integrated with LNG gasification plants

In recent years, the role of natural gas in the global energy mix has significantly increased, contributing 24.7% to the overall primary energy supply in 2020, due to its importance in the energy transition towards decarbonization. This rise in consumption has led to a substantial growth in interregional trade, with Liquefied Natural Gas (LNG) surpassing pipelines as the primary transportation method. In 2020, LNG accounted for 52% of global natural gas trade, up from 41% in 2010. Efficient operation of LNG regasification terminals is now crucial for both environmental and economic reasons, particularly regarding the recovery of cold energy typically wasted during regasification, where LNG is stored at approximately −160 °C and ambient pressure. This study investigates the integration of LNG regasification with thermodynamic cycles that exploit the available cold energy during the working fluid’s condensation. Two cycle categories are considered: a low-temperature cycle using seawater as a heat source, and a high-temperature cycle using exhaust gases from a gas turbine powered by a portion of the regasified natural gas. CO2 and R125 are selected as working fluids, with CO2 analyzed under both subcritical and supercritical conditions. The system’s performance is evaluated as a function of the regasification and distribution pressures, with a turbine installed to recover energy from the pressure difference. A medium-sized regasification terminal (50 kg/s) is analyzed, achieving an integrated cycle power output between 3 and 35 MW, depending on the heat source and working fluid. The integrated gas turbine operates at around 70–80 MW. Dedicated models developed Matlab environment simulate the regasification process, topping cycles, and their energy integration.