Current Status of Ceres Electrolysis Programme

Abstract

This paper reports on experimental testing and verification of Ceres solid oxide technology in electrolysis mode at all levels from small single cells to a 100-kW module. This programme has demonstrated that the electrochemical performance of Ceres core cell technology is broadly the same in fuel cell and electrolysis modes suggesting no fundamental difference when reversing the direction of current. Additionally, lifetime predictors such as degradation rate and resilience to thermal cycles and emergency stops, measured at stack level, show an equally high level of real-world robustness in electrolysis mode as in fuel cell mode. Finally, results from testing our first-of-a-kind 100kW electrolysis module show reliable operation, high electrical efficiency of >87% (LHV) or 38kWh/kgH2 and stacks performing at the same level as measured on test stands.

Electrochemical Analysis of an Electrolyte-Supported Solid Oxide Cell-Based MK35x Stack during Long-Term Electrolysis Operation

“…10,11,13 As a different metric, some long-term degradation studies prefer to use the resistance increase over time as a more accurate measure of degradation. 7,8,12,14,15 Here, values of 12-18 mΩ cm 2 kh −1 were reported for state-of-the-art ESC stacks, [6][7][8]12,15 or 20 mΩ cm 2 kh −1 for stacks with metal-supported cells were observed. 14 At the same time, the oxygen side outlet temperature increased from 800 °C at the beginning to 802 °C after 1570 h and 805 °C after 4942 h due to the increased Joule heating inside the stack.…”

“…7,8,12,14,15 Here, values of 12-18 mΩ cm 2 kh −1 were reported for state-of-the-art ESC stacks, [6][7][8]12,15 or 20 mΩ cm 2 kh −1 for stacks with metal-supported cells were observed. 14 At the same time, the oxygen side outlet temperature increased from 800 °C at the beginning to 802 °C after 1570 h and 805 °C after 4942 h due to the increased Joule heating inside the stack. Furthermore, the evolution of the gas-tightness of the stack was monitored by measuring the OCV in SOFC conditions, that is, with a dry fuel gas of 60% H 2 and 40% N 2 .…”

“…3 While some in-depth degradation studies are available on cell level, 4,5 detailed investigations of SOEL stacks with operation for more than 1000 h are uncommon in literature. [6][7][8][9][10][11][12][13][14][15] Moreover, the stack degradation behavior is only rarely spatially resolved to the individual repeat units (RUs) by means of electrochemical impedance spectroscopy (EIS). 7 The MK35x stack platform developed by IKTS is based on electrolyte supported cells (ESC) with chromium-iron-yttrium (CFY) interconnects.…”