High temperature solid oxide cells can be used both as fuel cells (SOFC) for power generation and as electrolyzer cells (SOEC) for hydrogen generation. Such cells are called reversible cells. They are typically made using solid electrolytes which exhibit purely ionic conduction and negligible electronic conduction. In this work reversible cells made of mixed ionic electronic conducting (MIEC) materials with significant electronic conduction as electrolyte are investigated. It is shown that MIEC cells can be designed to operate as efficiently as those made of a purely ionic conducting electrolyte (e.g. YSZ). Thus, in SOFC mode, suitably designed MIEC electrolyte cells consume fuel at the same rate, deliver the same power and release the same amount of joule heat as purely ion conducting electrolyte cells. Similarly, in SOEC mode, MIEC electrolyte cells consume water vapor at the same rate, generate hydrogen at the same rate, consume the same electrical power and release the same joule heat as purely ionic conducting electrolyte cells. Experimental results are presented on SOEC stacks made of YSZ and MIEC electrolyte cells. The MIEC electrolyte cells exhibit more stable operation compared to purely ion conducting electrolyte (YSZ) cells. The improved durability of MIEC electrolyte cells is attributed to the smoothening of the chemical potential of oxygen,) (2 x O , variation in the electrolyte. The analysis also shows that highly active electrodes should lower the tendency for degradation even with a purely ion conducting electrolyte cell.
High temperature steam electrolysis (HTSE) is a promising technology for large-scale hydrogen production. However, research on HTSE performance above the kW level is limited. This paper presents the results of 4 kW HTSE long-term test completed in a multi-kW test facility recently developed at the Idaho National Laboratory (INL). The 4 kW HTSE unit consisted of two solid oxide electrolysis stacks electrically connected in parallel, each of which included 40 electrode-supported planar cells. A current density of 0.41 A cm-2 was used for the long-term operating at a constant current mode, resulting in a theoretical hydrogen production rate about 23 slpm. A demonstration of 830 hours stable operation was achieved with a degradation rate of 3.1% per 1000 hours. The paper also includes detailed descriptions of the piping layout, steam generation and delivery system, test fixture, heat recuperation system, hot zone, instrumentation, and operating conditions. This successful demonstration of multi-kW scale HTSE unit will help to advance the technology toward near-term commercialization.
This paper describes the development of a feedback controller for rejecting wind disturbances on a crane payload. The goal of this research is to perform in-situ parameter sensitivity testing that is specific to a given crane structure. Through experimentation, this paper evaluates the robustness of a closed-loop controller that implements station keeping on a bridge crane. A set of general trends were developed to describe how altering system parameters and operating conditions affected controller performance. Such findings are not limited to single parameter characterization and can be extended to multiple variables given specific system specifications.
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