Assessment of an intermediate working medium and cold energy storage (IWM-CES) system for LNG cold energy utilization under real regasification case

Abstract

Owing to the fluctuating liquified natural gas (LNG) regasification rates in receiving terminals, LNG cold energy utilization systems face low recovery rate issue. In this work, an intermediate working medium and cold energy storage (IWM-CES) system is proposed to improve the operational flexibility and recovery rate for LNG cold energy utilization under actual regasification case. The proposed system comprises two modules, namely, cold energy recovery module and cold energy storage module. The cold energy recovery module recovers deep and shallow LNG cold energies using intermediate working mediums. The cold energy storage module acts as a buffer to promote stable cooling output. Key results revealed the maximum stable cooling output of conventional system (without cold energy storage) is constrained by the minimum regasification rate, which causes a relatively low recovery rate. On the contrary, the proposed system realizes a larger stable cooling output and enhances the cold recovery rate from 33.2% to 80.3%. Economically, the proposed system requires the injection of additional capital cost but can achieve better lifecycle profit. Environmental benefits are conducted and ultimately evaluated from users' perspective. Compared to the conventional system, the proposed system achieves the improvement of daily CO2 emissions reduction spanning 75.2 tons/day to 453.8 tons/day.