Performance Evaluation of Supercritical Carbon Dioxide Recompression Cycle for High Temperature Electric Thermal Energy Storage

Abstract

As interests in low carbon power generation are growing, the share of renewable energy power generation is increasing. Naturally, research on energy storage system is being conducted worldwide as a system to solve the intermittency problem of renewable energy. When renewable energy increases significantly, it is important to secure sufficient operating reserve with energy storage capability. In this paper, the performance of electric thermal energy system using 10MWe supercritical carbon dioxide recompression cycle is analyzed to investigate the feasibility of the proposed concept. Among many performance indicators, this paper mainly focused on the required thermal power for the system to stay in the stand-by mode, and the dynamic behavior of the proposed system during fast power ramp-up so that the potential of the system for providing ancillary services can be revealed. To investigate these issues, an on-design analysis is first conducted to determine the performance of the proposed system followed by component design to evaluate off-design performances and transient responses of the system. From the quasi-steady state analysis, break-even conditions are found for various inventory levels. In the transient analysis for power increasing operation from 0% to 100%, fluctuations in physical parameters are observed due to the sudden change in properties near pseudocritical pressure conditions. However, this issue can be mitigated with an appropriate inventory control system as shown in this paper. Thus, the proposed system shows promising transient performances for fast power ramp-up operation. This means that the electric thermal energy storage system with a dedicated supercritical carbon dioxide power cycle can be utilized as an operating reserve. The conclusions of this study are not only limited for the electric energy storage system application but also has an implication to the concentrating solar power or the advanced nuclear power plant application of the supercritical carbon dioxide recompression cycle.