Exergetic and economic assessment of integrated cryogenic energy storage systems

Cryogenics-based Energy Storage (CES) is a thermo-electric bulk energy storage technology that received much attention lately both in academia and industrial applications. CES charges surplus electricity in an energy-intense gas liquefaction process, stores electricity in form of liquid air and discharges electricity in a liquid-air Rankine cycle. CES is associated with a number of advantages towards competing bulk-energy storage technologies. CES is based on mature technologies, having a low environmental impact, no geographical constraints, long cycle life, low standby losses and a remarkable exergy density. At present, CES is at a pre-commercial state, which makes its claimed competitive specific costs and reported stand-alone efficiency of 40-60% crucial to its further development and application. This paper aims to identify the efficiencies and specific costs of a number of CES system configurations and to investigate the sensitivity of estimating CES costs to the wide range of reported characteristics. The exergetic and economic analyses are based on results from simulation of seven system configurations in ASPEN Plus. Economic sensitivity analysis is conducted independently and relies solely on data from literature. Among others, the effects of the following parameters on the CES levelized cost of discharged electricity are evaluated: price of electricity, specific investment cost, annual operation hours and economic life. The exergetic analysis revealed the favourable integration of regasifying LNG, in which the CES exergetic efficiency reaches 55%. Integration of waste heat was shown to reduce the specific costs of 300 MW CES systems from 1400 (sic)/kWh to 1100 (sic)/kWh. Lowest levelized cost of electricity was reached by diabatic CES systems with combustion of natural gas (161 (sic)/MWh) closely followed by waste heat integration (171 E/MWh). In the sensitivity analysis the effects of the specific costs and the cost of charged electricity were found to be of greater importance than efficiency. Moreover, CES was evaluated to be economically feasible in comparison to other bulk energy storage technologies.