Test and characterization of reversible solid oxide cells and stacks for innovative renewable energy storage

Abstract

This work aims at developing an innovative renewable energy storage solution, based on reversible Solid Oxide Cell (rSOC) technology. That is to say, one system optimized to operate either in electrolysis mode (SOEC) to store excess electricity to produce H 2 , or in fuel cell mode (SOFC) when energy needs exceed local production, to produce electricity and heat again from H 2 or any other fuel locally available. Firstly, work focused on optimization of the different layers constituting the single SOC cell to reach high initial performance applying state-of-the-art materials as previously reported [1]. Secondly, the initially highest performing cells were selected for long-term reversible SOFC/SOEC single cell tests. Thirdly, these cells were integrated in a stack design optimized for reversible operation at high degrees of H 2 and H 2 O utilization. The long-term single cell tests showed significant degradation in galvanostatic test periods during electrolysis but not in fuel cell mode prior to starting the reversible test operation while the degradation diminished during the subsequent rSOC operation of the cells operating at 700 C, +0.6 and -1.2 A/cm 2 in SOFC and SOEC modes respectively, at fuel utilization (FU) up to 80% in both modes. Electrochemical impedance spectroscopy analyses and post-mortem SEM investigations of tested single cells reveal that the fuel electrodes degraded significantly during the longterm single cell tests. Furthermore, long-term stack tests were conducted on 5-cell stacks, integrating both reference cells and optimised cells. The long-term stack tests were conducted applying different switches between SOFC and SOEC modes. Initially long duration tests (100h each mode) were performed in a mixture of 50% H 2 O and 50% H 2 to see the effect of the polarisation only. The alternating cycle SOEC/SOFC was repeated over a 1800 h testing period. Then stack switched daily from SOEC mode

Performance and Durability of Reversible Solid Oxide Cells with Nano-electrocatalysts Infiltrated Electrodes

“…In the EU-funded project REFLEX (Analysis of the European energy system under the aspects of flexibility and technological progress), the effects of current density, steam content, and the utilization degree were studied for the load cycling operation on the Ni/YSZ-based cells. 12,13 Differently, they found that at a high current density ( À 1.2 A/cm 2 ), the degradation rates under the SOEC mode significantly decreased during the load cycling operation compared to the constant SOEC operation. From the post-mortem investigation, microstructural changes such as detachment of Ni particles, Ni migration, and silica-rich impurities were observed in the fuel electrode after the load-cycling operation.…”

“…In the past decade, different electrode materials, microstructure of the electrodes, and operating conditions have been studied. [10][11][12][13] Lang et al 11 reported the long-term durability performance of an SOC stack consisting of 30 electrolytesupported cells (ESCs) supplied by Sunfire. The stack was operated for 3370 h in constant SOEC mode at 820°C followed by 2500 h in reversible SOFC/SOEC mode with the steam utilization of 70%.…”

Pathway toward cost-effective green hydrogen production by solid oxide electrolyzer

“…57 ALD (atomic layer deposition) and PLD (pulsed laser deposition) create nanofilms with higher performance and lower resistance. 58,59 Fig. 1 Three scenarios to reduce SOEC based hydrogen production cost.…”

“…57 ALD (atomic layer deposition) and PLD (pulsed laser deposition) create nanofilms with higher performance and lower resistance. 58,59 Overall, SOEC has and will move toward stability, durability, and efficiency.…”

Benchmark study of performances and durability between different stack technologies for high temperature electrolysis

“…The stack gas connections to the test bench were done through an in-house developed solution based on a proprietary form of high temperature flanges [28]. Additional information on stack design and experimental results on performance and durability can be found in references [13,[29][30][31][32][33][34].…”