Evaluation of Dynamic Reversible Chemical Energy Storage with High Temperature Electrolysis

Renewable power generation is intermittent and non-dispatchable, but is steadily increasing in penetration due to lower costs associated with installation and demand for clean power generation. Without significant energy storage available to a grid with high renewable penetration, a mismatch between the load and the power available can. Furthermore, advanced high temperature nuclear reactors offer clean power generation, but only at a baseload operation scenario due to the significant thermal inertia associated with the reactor. Also, natural gas is expected to continue to play a major role during and after the transition from modest renewable use to a majority of renewable penetration, but will need to have a reduced carbon footprint. In this study, the storage of otherwise curtailed renewable power through hydrogen via high temperature electrolysis and the dispatch of shifted renewable power through hydrogen via reversible high temperature fuel cells is studied on a system level utilizing spatially resolved dynamic physical system models built upon fundamental principles. Reversible solid oxide fuel cell (RSOFC) systems are considered for the bulk of the analysis for standalone, thermally self-sufficient systems using a combustor and resistive heaters. RSOFC systems are also considered for integration with renewable power for storage and dispatch of renewable power at various scales including grid-scale energy storage. Additionally, a nuclear reactor is coupled with a solid oxide electrolyzer system in order to study the ability of dispatching a nuclear power plant by shifting the heat from the turbine generators to the electrolyzer during periods of high renewable generation. Molten carbonate electrolysis used in a reformer-electrolyzer-purifier (REP) concept is considered for the generation of hydrogen from steam and natural gas where the power input is renewable resulting in a portion of renewable hydrogen from natural gas feedstock. The results of the work provide valuable insights into the steady-state and dynamic operation of RSOFC systems under various loads and system configurations. Integration with renewables, nuclear, and grid energy storage were studied and the benefits and challenges discussed. The REP integration with renewable power and natural gas feedstock was verified with experimental data and dynamic simulations were conducted