A new application study of liquefied natural gas in assisting in the start-up of the liquid air energy storage system without sufficient cold storage energy

Liquid air energy storage (LAES) is a highly promising large-scale energy storage technology, with the cold energy cycle being a key part. However, during the initial start-up of an LAES system or its restart after a prolonged maintenance, the system may face a cold storage energy deficiency, and how to establish the cold energy cycle under such conditions has not been adequately addressed in existing studies. Based on a dynamic model of an LAES system, this study first investigates the process and performance of air liquefaction without cold storage energy, relying solely on the throttling cooling effect of air. Subsequently, a novel scheme and evaluation metrics are proposed for using the additional cold energy from liquefied natural gas (LNG) to assist in the start-up of the LAES system without cold storage energy, and the performance of this process is analyzed. The results show that when cold storage energy is sufficient, the liquid air begins to form approximately 30 s after start-up. However, when cold storage energy is deficient, it takes about 844 s to generate liquid air, and the maximum liquid yield is only 2.71 %, leading to around a 30-fold increase in the time required to fill up the liquid air tank (LAT) compared to the rated charging duration. By introducing the LNG, the liquid air can be produced 92 s after start-up under optimal conditions, with a maximum liquid yield of 41.7 %. The time required to fill up the LAT is reduced to 1/15.2 of the required time of the LAES system not using external cold energy. Additionally, the lower the LNG operating pressure, the faster the air liquefaction process, and the less the total LNG consumption. The findings of this study provide a viable contingency strategy for cold storage energy deficiency in LAES systems caused by any possible factors, contributing to the development of robust start-up procedures and enhancing system reliability.