Thermodynamical analysis of a mirror gas turbine cycle for LNG cryogenic exergy recovery

Liquefied Natural Gas (LNG) is transported via specialized marine vessels under relatively low pressure (0.13–0.14 MPa) and at cryogenic temperatures of approximately 100 K, where it is stored in insulated cryogenic containers. The liquid state and extremely low temperature of LNG correspond to its high exergy content, which is accumulated during the liquefaction process - a phase that involves substantial energy consumption. During regasification, which occurs in atmospheric regasifiers at onshore terminals and local regasification stations, this cryogenic exergy is typically lost without being recovered or utilized. To address this inefficiency, this study proposes and evaluates novel LNG regasification based on Brayton cycle modifications. These systems are analyzed and compared in terms of exergy efficiency to assess their potential for improved energy recovery. A solution based on the mirror gas turbine concept with a low overall compression ratio is selected due to its high energy efficiency of 73% and high exergy efficiency of 52%. The proposed system is shown to maintain high efficiencies for a wide range of temperature difference values across the heat exchangers which indicates a possibility of compact implementation.