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Modeling and analysis of a H₂-H₂O driven reversible solid oxide cell system for electrical energy storage applications
Hosseinpour, Javad
Hosseinpour, Javad
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2024
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2026-04-04
Abstract
The future of renewable energy resources, such as solar and wind is heavily reliant on energy storage. Solid oxide cells (SOCs) with bidirectional operation have advantages over other types of energy storage systems since they may be deployed in time-shifting, long-duration, and seasonal storage applications while having lower life cycle environmental impacts and can be manufactured from readily abundant elements and materials. This research examines the technical and economic viability of grid-scale energy storage systems based on high-temperature, stand-alone reversible solid oxide electrochemical systems at the 1 MW (8 MWh) scale using H2-H2O chemistry. A multi-scale modeling approach is employed that moves from one-dimensional cell-level models for stack performance estimation to full-scale systems with balance-of-plant models and equipment cost equations. The one-dimensional cell model is developed and calibrated using test data from an advanced, anode-supported SOC from a project industry partner. Process engineering and equipment selection of various ReSOC system configurations is examined and down selected based on energetic and economic considerations. The system performance sensitivity to various design parameters, including current density, stack temperature and pressure, and recirculation ratios on both the air and fuel sides of the stack, is explored and parameters selected through optimization studies of various objective functions. It is demonstrated that increasing the operating current density of the electrolysis stack leads to thermoneutrality while only minimally enhancing system efficiency. The results show that by carefully selecting the system design and operational parameters, it is possible to achieve 50.4% round-trip efficiency (RTE) with a levelized cost of storage (LCOS) as low as 13.5 ¢/kWh. Because of thermal management challenges associated with maintaining ReSOC stack operating conditions in either the highly endothermic or exothermic operating modes, approaches for integration of various thermal energy storage (TES) technologies are investigated towards improving the system RTE while trying to limit increases in LCOS. Both low- and high-temperature sensible and latent TES approaches are examined through a combination of heat transfer fluid type screening, phase-change materials assessment, and system simulation. The results show that a ReSOC combined with a steam accumulator which stores low-grade thermal energy (<150°C) during exothermic fuel cell operation achieves the highest system RTE (57%), representing a 6.6% point improvement over scenarios without TES. Despite the addition of new system components, the LCOS remains largely unchanged when compared to the base case. Technology attribute comparisons with conventional EES technologies are made. Lastly, the impact of mode-switching on the thermal dynamics of the ReSOC is evaluated under various inlet flow configurations using a dynamic 1-D Model.
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