Operational strategy for an isolated microgrid powered by a small modular reactor-driven sCO₂ recompression cycle integrating proton exchange membrane electrolysis and solid oxide fuel cells

A small modular reactor-driven supercritical CO₂ (sCO₂) cycle exhibits significant potential for deployment in isolated microgrids, including remote and offshore settings, but unsafe compressor operation constrains its load range, necessitating integrated energy storage capabilities. This study incorporates a proton exchange membrane electrolytic cell (PEMEC) and a solid oxide fuel cell (SOFC) to enable electricity absorption and supplementation. After determining the intrinsic load range of the sCO₂ recompression cycle via a self-developed model, the influence of cell operating parameters on charging and discharging performance is examined, and the combined system's energy efficiency over a complete charge-discharge cycle is evaluated. Results indicate that low-load and overload demands drive the compressor toward its surge and choke boundaries, confining the load range to 4.72-14.35 MW. The incorporation of PEMEC-SOFC expands this range to 1.42-15.31 MW. Adjusting hydrogen production/consumption rates exerts a stronger impact on the charging/discharging power than tuning operating temperature, and the former is constrained by the operating time due to the fixed hydrogen tank capacity. Among operation strategies with different charging and discharging durations, the short-charge/short-discharge mode yields the lowest energy efficiency of 33.73%, whereas the long-discharge mode achieves higher energy efficiency and enables an optimal charging time that maximizes overall system performance. A case study targeting an isolated microgrid demonstrates the system's storage-controlled discharge characteristics and confirms its theoretical feasibility. These findings provide a technically viable pathway to enhance the operational flexibility of sCO₂ cycle-driven isolated microgrids.