Thermodynamic matching mechanism and topological evolution for LNG-LAES: A dual-stage refrigeration strategy with pre-cooling

The integration of Liquid Natural Gas (LNG) cold energy into Liquid Air Energy Storage (LAES) is a promising pathway for efficient energy storage, yet current optimization approaches often overlook the intrinsic thermodynamic synergy within the liquefaction process. A mechanism-driven optimization strategy for an LNG-LAES system integrated with an independent nitrogen refrigeration cycle is proposed in this study. Through a systematic analysis of the spatial distribution of the minimum temperature difference, it is identified that the pinch point in conventional schemes is prematurely constrained to the intermediate temperature region (approx. -80°C), severely limiting the utilization of high-grade cold energy. To address this, a strategic cold energy cutoff method combined with flow modulation is introduced to reshape the heat transfer profiles. Subsequently, a novel dual-stage refrigeration topology featuring pre-cooling is developed. The optimized configuration successfully shifts the pinch point to the deep-cryogenic end, reducing the Logarithmic Mean Temperature Difference in the main cold box from 11.95°C to 6.48°C. Under the global optimal conditions (6.1 MPa liquefaction pressure, -164°C nitrogen temperature), the system achieves a minimized LNG mass flow ratio of 0.588, representing a 50% reduction compared to the baseline. Furthermore, by regulating the expansion refrigeration pressure, the system effectively adapts to LNG temperature fluctuations (-145°C to -135°C), maintaining the Round-Trip Efficiency between 75.52% and 78.84%. This performance effectively decouples the energy storage capacity from LNG terminal throughput constraints, offering a reliable solution for large-scale grid energy management.