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Durability Testing of a High‐Temperature Steam Electrolyzer Stack at 700 °C
Author(s) -
Fu Q.,
Schefold J.,
Brisse A.,
Nielsen J. U.
Publication year - 2014
Publication title -
fuel cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.485
H-Index - 69
eISSN - 1615-6854
pISSN - 1615-6846
DOI - 10.1002/fuce.201300150
Subject(s) - stack (abstract data type) , ohmic contact , materials science , voltage , transient (computer programming) , electrode , nuclear engineering , high temperature electrolysis , electrolysis , oxide , analytical chemistry (journal) , electrical engineering , thermodynamics , chemistry , composite material , physics , metallurgy , layer (electronics) , computer science , chromatography , electrolyte , programming language , engineering , operating system
A 5‐cell solid oxide electrolyzer cell (SOEC) stack has been operated at ca. 700 °C for 2,000 h under static conditions followed by a short‐term transient operation. The best repeating unit (RU) showed an area specific resistance of 0.4 Ω cm 2 and an initial voltage of 1.125 V at 705 °C and –0.6 A cm –2 when fed with 90% H 2 O/10% H 2 at the hydrogen‐electrode. One instability factor has been observed, which led to dramatic voltage fluctuations for most RUs in the stack. Such kind of voltage fluctuation is correlated predominantly to the variation of ohmic resistances of RUs, pointing out most probably unstable electrical contact in the stack under the present testing conditions. Disregarding the worst RU (RU1), the average degradation rate (voltage increase rate) of all RUs in the stack has been determined to be around 2% kh –1 (24 mV kh –1 ) for the last 500 h of static operation free of voltage fluctuations. The stack showed no noticeable degradation during the short‐term transient operation (totally 756 ON/OFF current cycles), indicating preliminarily that it could be possible to couple intermittent power sources with high‐temperature steam electrolyzers.