Thermodynamics and Economics of Different Asymmetric Cold Energy Transfer in a Liquid Air Energy Storage System

Liquid air energy storage is a promising large-scale energy storage technology. However, the asymmetric cold energy transfer exists due to the cold energy loss during the intermission period (the transition time between the charging and discharging process), which seriously affects the system efficiency. Most theoretical researches are based on the ideal cold energy storage (CES) models, failing to predict the characteristics of the asymmetric energy transfer. Therefore, a new self-adapting modified Linde cycle (I) is built for the imperfect CES. Two methods of cold energy supplement to increase the CES efficiency are investigated, including a modified Linde cycle with an external cold source of liquid nitrogen (II) and a modified Claude cycle (III). Thermodynamics and economics are compared for three modes. The influences of adiabatic efficiencies of the compressor and the turbine on the system are analyzed. The results show that modes II and III can achieve the higher energy, exergy efficiencies compared to mode I. Mode III has the highest round-trip efficiency and the largest gaps of III-I and III-II are 2.3% and 2.5%, respectively. Mode III owns the best economic performance and the annual total profit is 185.3-836.6 k$ higher than that of mode I.