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Transient behavior of tubular solid oxide electrolyzer cells under fast load variations
Fogel, S.ORC; Kryk, H.; Hampel, U.ORC
Solid oxide electrolyzer cells (SOEC) pose a promising technology for the production of hydrogen gained from renewables, such as wind and PV. Due to the fluctuating nature of these sources, the transient behavior of SOEC under various load cases plays a crucial role in terms of their long-time stability, degradation behavior, conver-sion efficiency and application. As a consequence of the intermittent occurrence of renewables, SOEC designs and all employed materials have to be capable of with-standing harsh operating conditions, leading to strict demands regarding process control and the overall cell design. Tubular cell designs of SOECs received in-creased attention in recent years due to their inherent advantages. They offer rapid startup capabilities as well as high resistance to heat and thermal stresses. Further-more, tubular cells are characterized by significantly smaller sealing lengths in com-parison to planar cells, enabling a high-pressure application. Operating SOECs at elevated pressures poses beneficial opportunities for their future system application, since the produced hydrogen does not need to be compressed using a separate compressor stage or the electrolyzer can be combined with promising downstream synthesis units (e.g. methanol synthesis). Dynamic simulations can be used to de-termine the transient behavior of SOECs during operation with harsh load-transients. This simulation work aimed to study the transient behavior of a single, proton conducting SOEC during rapid load variations under high-pressure opera-tion. For this purpose, a two-dimensional model of a tubular SOEC was developed and different load steps and their influence on crucial operational parameters, such as temperature profiles, cell potential and species concentrations were investigated. The feasibility of the cell design regarding harsh transient load variations was stud-ied. Various load-pulse shapes and durations, different flow configurations and steam mass flow rates have been investigated and their influence on the short-term transient behavior of the cell were examined. With the aid of the aforementioned simulations, limiting operational states of the cell (e.g. steam starvation and tempera-ture hot-spots) as well as beneficial process parameter combinations for an im-proved cell operational behavior were ought to be identified with respect to advanc-es in cell control strategies.
Keywords: SOEC, dynamic operation, proton conduction
  • Poster
    Jahrestreffen der ProcessNet-Fachgruppe Energieverfahrenstechnik, 06.-07.03.2019, Frankfurt am Main, Deutschland

Publ.-Id: 29723 - Permalink