Liquid air as an energy carrier : application to LNG cold energy distribution in cold storage system = 에너지 운반체로서의 액화공기 : 냉동 창고에의 LNG 냉열 에너지 분배 적용application to LNG cold energy distribution in cold storage system
This study proposes a liquid air supply chain of a cold storage system, delivering wasted liquefied natural gas (LNG) cold energy to a cold storage system with liquid air. The liquid air is utilized in the cold storage system for a cold energy delivery and a distributed generation. LNG cold energy is used in an air liquefaction system to store energy in liquid air. The produced liquid air is transported to a cold storage system by trucks. In the cold storage system, liquid air delivers the cold energy for the refrigeration, and vaporized air generates electricity by passing through an expander. Processes of the air liquefaction system and a proposed system that utilizes liquid air are designed. The designed processes are evaluated in terms of thermodynamic and economic aspects. Subsequently, the results are compared with a conventional $NH_3/CO_2$ cascade refrigeration system. From the thermodynamic analysis, the air liquefaction system required 130 bar of air compression pressure and the proposed system required 100 bar of liquid air injection pressure. In the proposed system, 106 kW of power was generated. From the life-cycle cost (LCC) analysis, approximately 2–33% of LCC reduction was achieved in the proposed system, depending on the daily operation time. For a nominal operation time of 16 ~ 18 h/day, about 8–11% of LCC reduction was achieved. The sensitivity analysis for the cold storage systems indicated that the liquid air delivery was the dominant parameter.