Improvement potential of Cryogenic Energy Storage systems by process modi fi cations and heat integration

Cryogenic Energy Storage (CES) system is currently gaining significant attention in the field of large-scale energy storage systems. This is because this system can provide high energy-density during storage and uses air or nitrogen that are available at no or a low cost. Moreover, the technology has matured and can be used on-site in a decoupled manner. The CES system has three sub-processes, namely, charging or liquefaction, storage, discharging or power cycle. To investigate the improvement potential of such systems, state-of-the-art configurations for each sub-processes have been analyzed in this paper. A configuration consisting of a multi-stage turbine expansion, a turbine and a JT-valve connected in series at the liquefaction stage, Organic Rankine cycle for utilization of heat of compression, and a four-stage reheat Rankine cycle with thermal energy storage at cryogenic temperature has been proposed. The study suggests that a high turnaround efficiency (about 90%) of the process may be achieved by an appropriate external source of thermal energy. ? 2021 Elsevier Ltd. All rights reserved.