An analysis of a large-scale liquid air energy storage system

Liquid air energy storage (LAES) is a class of thermo-electric energy storage that utilises cryogenic or liquid air as the storage medium. The system is charged using an air liquefier and energy is recovered through a Rankine cycle using the stored liquid air as the working fluid. The recovery, storage and recycling of cold thermal energy released during discharge more than double the overall energy efficiency of the cycle. The demand on a storage plant in a grid support application is expected to be irregular and intermittent in response to fluctuating supply from intermittent renewable generators. This will complicate the storage of thermal energy and will mean the energy flow rates in the thermal store will vary from cycle to cycle and the state of charge of the store will also vary. This paper presents an analysis of the LAES cycle. The material and configuration of the cold thermal store is discussed in particular with reference to scale and measures to mitigate losses due to the irregular and intermittent duty cycle. The paper concludes with capital and levelised cost analysis of a reference 20 MW/80 MWh LAES plant and a comparison of the levelised cost with other storage technologies.