Comparative analysis of sensible heat and latent heat packed bed cold energy storage for liquid air energy storage systems

A liquid air energy storage is a novel technology receiving substantial interest for balancing the supply and demand of energy because of its high energy density and not being geographically constrained. The main challenge of the liquid air energy storage system demonstrated so far is its low round-trip efficiency. Internal heat recovery, using hot and cold thermal energy storages, increases the round-trip efficiency of the liquid air energy storage. High temperature thermal energy storages are widely studied for different applications. However, the poor performance of the cold thermal energy storage is currently a bottleneck to achieve cost-effectiveness of the liquid air energy storage system. That is due to the very low temperatures and the large temperature span of the cold energy storage. In this paper, two types of cold thermal energy storages, a packed-bed sensible storage and a latent heat storage with cryogenic phase change materials, were applied to a stand-alone liquid air energy storage system. A one-dimensional transient numerical model was developed to analyse the storage systems. The round-trip efficiency, liquid air yield, and expansion work of the liquid air energy storage system were evaluated considering both storage options. The results indicate that the latent heat packed bed storage configuration has higher round-trip efficiency (41 %), liquid yield (58.1 %), and power output (42 MW) than those of the configurations with sensible heat storage. However, there are some sensible materials, like quartzite rocks that, with the same volume of the packed bed, perform as well as cryogenic phase change materials due to their high densities.