Off-design performance of supercritical compressed carbon dioxide energy storage system

Abstract

Energy storage is a supporting technology to achieve large-scale consumption of renewable energy and smart grid. Supercritical compressed carbon dioxide energy storage (SC-CCES) system is an appealing physical energy storage thanks to its compact system structure and high round-trip efficiency. However, in previous studies, the temperature and pressure of storage chamber are traditionally set to a constant value, there is a lack of thermodynamic analysis for SC-CCES system from the perspective of storage chambers interactively varying, which results in compressor and turbine operating consistently at off-design conditions. Hence, the off-design performance of SC-CCES system is investigated. The parametric analysis is conducted to evaluate the influence of system parameters and the optimization design platform is established to explore the optimization potential. Results indicate that roundtrip efficiency and energy density of SC-CCES system present opposite varying trends with increasing compressor efficiency and the initial temperature of charge in low-pressure storage chamber. The optimal round-trip efficiency of SC-CCES system is achieved as 78.14 %, along with the optimal energy density of 0.2580 kWh/m³.