Thermodynamic and economic analysis of multi-generation system based on LNG-LAES integrating with air separation unit

Abstract

LNG consumption is rising globally, releasing significant cold energy during regasification. Coupling LNG vaporization with liquid air energy storage (LAES) maximizes this cold energy recovery, enhancing LAES efficiency. However, current LNG-LAES systems face issues like insufficient high-grade cold energy use and high liquid air temperatures. LAES's inability to recover LNG cold energy during energy release necessitates cold storage fluid, increasing costs. Safety concerns also arise from LNG and air coexisting in the same heat exchanger, and LNG vaporization fluctuations can destabilize LAES operations. This study proposes a multi-generation system (LNG-LAES-ASU) incorporating an air separation unit (ASU) to address these challenges. The ASU recovers LNG cold energy during energy release, adapts to LNG vaporization fluctuations, and reduces ASU energy consumption. Energy, economic, and peak-shaving performance analyses show the system achieves a 91.07 % round-trip efficiency (RTE). The ASU's average energy consumption is 0.1356–0.1506 kWh/Nm³ O₂, much lower than a standalone ASU's 0.4 kWh/Nm³ O₂. Over 30 years, the system yields a net present value (NPV) of $56,111,291 and a dynamic payback period of 3.23 years. Its peak-shaving capacity is 2.47–2.57 times greater than LNG-LAES alone. This research offers valuable insights into efficient LNG cold energy utilization.