bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chromium-Related Degradation of Thin-Film Electrolyte Solid Oxide Fuel Cell Stacks
Authors: Menzler Norbert H. , Sebold Doris , Fang Qingping 
Published: February 2020

Solid oxide fuel cell short stacks for dezentralized stationary power delivery have been operated with special thin-film electrolyte anode-supported cells. After operation times of up to 3,000h the cells were post-test characterized. The cells have besides very thin electrolyte films (≤ 3µm) either LSCF or LSC cathodes (LSCF: La-Sr-Co-Fe oxide, LSC: La-Sr-Co oxide). Typical operation parameters were temperatures between 600 and 750°C, a current density of 500mA/cm², hydrogen with 20% water vapor and a fuel utilization of approx. 40%. Typical chromium evaporation protection layers like wet powder sprayed manganese oxide and cathode contact layers (a perovskite based on La-Mn-Co-Cu oxide) were used.
Microstructural post-test characterization reveals in the case of using a 1µm 8YSZ electrolyte prepared via sol-gel route and on top a sputtered diffusion barrier layer composed of GDC, the existence of SrCrO4 either on top of the LSCF cathode as expected or, unexpectedly the formation of the spinel phase at the borderline cathode / barrier (electrolyte) layer. In case of using a 3µm thin screen printed 8YSZ electrolyte and an LSC cathode, the chromite phase has not been detected at the cathode / barrier border.
SEM and TEM post-test analysis of the cells show in case of the sol-gel electrolyte and sputtered GDC also the formation of micro-pores within the GDC layer. Theoretical calculations reveal that the chosen current density may lead to either preferred oxygen reduction or preferred chromium reduction depending on the real local current density within the cathode / barrier (electrolyte) interface.
Stationary 2D FEM Model Framework for SOFC Stack Performance Prediction
Authors: Geisler Helge , Kromp Alexander , Joos Jochen , Weber André , Ivers-Tiffée Ellen 
Published: February 2020

High performing anode-supported cells (ASCs) undergo a significant power reduction when contacted by a metallic interconnector (MIC) and operated in a stack layer [1,2]. The performance limiting factors can be identified by a stationary 2D FEM model, which calculates current/voltage (C/V) characteristics for specific SOFC stack layer setups. The required parameter set which describes (i) electrical/ionic conduction, (ii) electrochemical charge transfer and (iii) porous media gas transport is obtained via electrochemical impedance spectroscopy (EIS), 4-point DC conductivity measurements and 3D microstructures extracted from FIB-tomography [3]. The applicability of our stationary 2D FEM model was verified by comparing simulated and measured C/V characteristics over a broad range of operation conditions, and published in [3,4].
For state-of-the-art LSCF cathodes as thin as 45 µm, the simulation results demonstrate significant performance loss due to O2starvation underneath the MIC contact ribs and/or electrical cross conduction limitations in the cathode material underneath the gas channel area in each individual stack layer [3,4]. Following up these results, a systematic variation of the cathode parameters thickness, porosity, tortuosity, mean pore diameter, and electrical conductivity as well as of the MIC flowfield design has been carried out numerically. In this way, the sensitivity of each parameter on stack layer performance became transparent.
It will be shown in this work, that (i) choosing an optimized cathode/MIC design combination can increase current density at 0.7V by more than 25% in an SOFC stack assembly (see figure 1), that (ii) the magnitude of possible loss minimization requires the ability to precisely control the system parameters, and that (iii) an optimized MIC design avoids microstructural changes occurring in the cathode/CCL material because of its inherent chemical stability limitations.
[1] L. Blum, W. A. Meulenberg, H. Nabielek, R. Steinberger-Wilckens, Worldwide SOFC Technology Overview and Benchmark, International Journal of Applied Ceramic Technology
2, pp. 482-492 (2005).
[2] M. Kornely, A. Leonide, A. Weber, E. Ivers-Tiffée, Journal of Power Sources, Volume 196, Issue (17), pp. 7209-7216 (2011).
[3] H. Geisler, A. Kromp, A. Weber, E. Ivers-Tiffée, Journal of the Electrochemical Society, 161 (6) F778-F788 (2014).
[4] H. Geisler, A. Kromp, A. Weber, E. Ivers-Tiffée, Proceedings of the 11th European Solid Oxide Fuel Cell Forum, A0904 (2014).

Figure 1
Current Status of Rapid Evaluation of Durability of Six SOFC Stacks within Nedo Project
Authors: Yokokawa Harumi 
Published: February 2020

Six solid oxide fuel cell stacks manufactured by Kyocera, MHPS, TOTO, NGK spark plug, NGK Insulator, Murata Manufacturing have been investigated to identify their performance degradation behavior, extract the major sources of degradation factors, clarify the degradation mechanism, and predict the time dependent contribution of such degradation to life time. Stack performance was analyzed into several contributions, and an interesting correlation of overpotential values and ohmic loss has been obtained in addition to identification of respective degradation rates. Respective degradation issues have been examined experimentally with SIMS, FIB-SEM, STEM and described as key simulation techniques to predict the long life up to 90,000 h. Emphases have been placed on degradation of cathodes with Cr or S; to ensure the appropriateness for overcoming such poisoning effects, care is made to measure the impurity level after long term operation in various environments. For simulation, focus was made to overcome some gaps between knowledge on stacks and on single (or buttons) cells appearing in several aspects.
Development of Intermediate Temperature (550 - 650oC) Metal Supported Solid Oxide Fuel Cells (SOFCs) Using Plasma Processes
Authors: Rupa Pantula K. P. , Goli V. R. , Balasubramanian Krishnamurty , Tomov R I , Kumar R Vasant , Glowacki B A , Krishnan Venkatesan Venkata 
Published: February 2020

The primary problem in preparation of metal supported SOFCs, in almost all cases is reconciling the sintering characteristics of the metal support vis-a-vis the ceramic electrolyte/ anode functional layer, with which it is in contact. The sintering temperatures of dense ceramics are much higher than those of metal supports (Ferritic steels in this case), as also are differences in sintering atmosphere.
As an alternative to using aids to lower the sintering temperature of ceramics (GDC and YSZ), thereby matching that of the substrate (which can lower electrical conductivity of the electrolyte), plasma spray deposition and plasma assisted co-sintering methods can be used effectively for multi-layered deposition, bonding and sintering.
In this work, an entire cycle for fabricating a metal supported cell is discussed, using porous SS430L as anode substrate, NiO-GDC as anode functional layer, GDC as electrolyte and LSCF-GDC as cathodic layer. Other techniques such as tape casting for metallic substrates and Inkjet printing have also been incorporated into the manufacturing operations to engineer a metal supported SOFC cell. Key steps involve -

Tape Casting of porous SS430L substrate layers, followed by vacuum sintering (1100 C)

Inkjet printing/ Screen printing of anode (NiO + GDC) functional layers, followed by hot plasma surface treatment to induce sintering and bonding (‘Plasma Glazing’)

Plasma Spray (powder) deposition of GDC electrolyte layer leading to bonding and sintering

Ink-Jet printing of GDC colloidal suspension to give better finish to the ‘rough’ electrolyte surface, followed by ‘Plasma Glaze’

Brush printing/ Screen printing of cathode (LSCF + GDC) layers on the electrolyte surface followed by ‘Plasma Glazing’

The above mentioned process is part of an ongoing Indo-UK program wherein NFTDC, with its partner, University Of Cambridge, UK, has taken a multi-disciplinary approach to developing a metal supported SOFC stack. This program includes - Materials synthesis and processing (GDC, LSCF), Stack design and Interconnect fabrication, Cell-Stack assembly, along with Electrochemical and microstructural characterization, and finally, process design of the overall system that can operate on commercial Natural Gas or Higher hydrocarbon fuels.
Thermal Integration of SOFC and Plate Heat Exchanger Desorber
Authors: Venkataraman Vikrant , Pacek Andrzej W , Steinberger-Wilckens Robert 
Published: February 2020

SOFCs are a potential candidate for use as Auxiliary Power Units (APU’s) on board heavy duty trucks. Heat from the SOFC exhaust is generally used either for cabin heating or for recuperative heat exchange and even after that there is still a considerable amount of high quality heat available. The unique selling point of an SOFC is the availability of both electricity and high quality heat. Not using the heat from an SOFC stack is tantamount to using only half the available useful energy from the fuel.
The ongoing research work reported here focuses on the design & development of a compact Solid Oxide Fuel Cell –Vapour Absorption Refrigeration System (SOFC-VARS) unit for refrigerated truck applications. This report presents a numerical model and simulation for thermal integration of an SOFC stack with a plate heat exchanger desorber via a specially designed tube in tube heat exchanger with internal fins where thermal oil is heated to the required desorber temperature and then serves as the coupling fluid in the plate heat exchanger desorber.
The sizing of the heat exchanger and desorber has been carried out to fit a small refrigerated van, to cater to a 1 kW cooling load. The modelling focuses on the heat transfer aspects at the SOFC and heat exchanger end and on both heat & mass transfer aspects at the desorber end.
The results show that a plate heat exchanger desorber is able to produce the required quantity of refrigerant needed for a 1 kW cooling load. A thorough sensitivity analysis on the plate heat exchanger desorber has also been carried out to identify the parameters that affect desorption performance the most and the parameters that have least effect on the desorption performance.
The use of plate heat exchangers as desorbers not only gives a high heat transfer surface needed for desorption but also leads to considerable reduction in desorber volume when compared to conventional falling film desorbers. Based on the results obtained from modelling, appropriate design maps have been drawn which showcase the sizing of the plate heat exchanger desorber and the SOFC stack and also the mass flow rate of thermal oil needed.
A Lumped Dynamic Modelling Approach for Model-Based Control and Diagnosis of Solid Oxide Fuel Cell System with Anode Off-Gas Recycling
Authors: Marra Dario , Sorrentino Marco , Pohjoranta Antti , Pianese Cesare , Kiviaho Jari 
Published: February 2020

The interest towards anode off-gas recycling (AOGR) in Solid Oxide Fuel Cell (SOFC) systems has recently increased, mainly due to the potential electrical efficiency improvement, as well as to the possibility of avoiding feeding external water for fuel reforming, when adopting such a configuration. However, advanced system control is necessary to ensure such relevant benefits are achieved. Proper control actions and system performance optimization, when AOGR is introduced, entail developing detailed thermodynamic system analysis, in such a way as to remove or at least limit any hazard associated to solid carbon formation, while suitably meeting thermal and electric requirements. To this end, an adequate SOFC stack model is necessary. This work focuses on the identification and validation of an SOFC stack model that accounts for AOGR inclusion. A lumped dynamic modelling approach is adopted to simulate temperature and gas composition at the stack anode outlet. The model is able to simulate the dynamic response of the stack during transients, as shown in Figure 1. Experimental data from a real SOFC system is used in model validation and the modeling approach adopted here ensures achieving a satisfactory compromise between estimation accuracy and computational burden. These factors support using the model as state estimator in model-based control and diagnosis algorithms.
Figure 1 – Comparison between measured and simulated fuel gas temperature at anode outlet

Figure 1
SOFC Anode Based on YSZ Pillars
Authors: Nagato Keisuke , Shinagawa Shunta , Shikazono Naoki , Iwasaki Shiko , Nakao Masayuki 
Published: February 2020

In anode of solid oxide fuel cells (SOFCs), yttria-stabilized zirconia (YSZ), Ni, pore are distributed, and oxygen ions, electrons, H2 and H2O gases are transported in each path. And the species chemically reacted each other at the boundaries (triple phase boundaries, TPBs). In the view point of tortuosity, aligned YSZ and Ni particles and TPB are promising structures for a low resistances of matter transporting and their chemical reaction. In our previous work [1], it was proposed and developed that Ni particles were aligned by magnetic field during the drying process after screen-printing Ni/YSZ paste. A second step of low-tortuosity path configuration is completely straight along the specie transporting direction. Because the nominal conductivity of oxygen ion in YSZ is the lowest among the specie (ion, electrons, gas) transportation conductivities, YSZ should be straight preferentially. In this study, we prototyped pillar pattern of YSZ, infiltrated Ni, and investigated the effect of pillar width, height, and surface area of pillar corresponding to TPB length on the generation performance. The YSZ pillars were fabricated by an excimer laser. The figure shows that the width were varied 5, 10, 20, 40 μm, and their trenches were fabricated deeper in wider pillar. The trenches of YSZ pattern were infiltrated by Ni particles. The finer pillar resulted in higher generation performance as also shown in the figure. Furthermore, the electrochemical phenomena was discussed by Lattice-Boltzmann Method simulation.
[1] K. Nagato, N. Shikazono, A. Weber, D. Klotz, M. Nakao, E. Ivers-Tiffée, ECS Trans. 57, 1307-1311 (2013).

Figure 1
Lifetime and Performance Prediction of SOFC Anodes Operated with Trace Amounts of Hydrogen Sulfide
Authors: Riegraf Matthias , Schiller Guenter , Costa Rémi , Friedrich K. Andreas , Latz Arnulf , Yurkiv Vitaliy 
Published: February 2020

Chemical degradation of Solid Oxide Fuel Cell (SOFC) anodes can be caused by various types of impurities present in practical fuels, as e.g. sulfur, chlorine, phosphorus and siloxane. To allow for a deeper understanding of the processes leading to sulfur poisoning, this study presents a modeling work of SOFC operating on H2/H2O and CH4/H2/H2O gas mixtures with different hydrogen sulfide (H2S) concentrations. In order to interpret experimental measurements, an elementary kinetic model is developed comprising a detailed multi‐step reaction mechanism of sulfur formation and oxidation at Ni/YSZ anodes coupled with channel gas-flow, porous-media transport and elementary charge-transfer chemistry.
A thermodynamic and kinetic data set of sulfur formation and oxidation is derived based upon various literature sources including a coverage-dependent description of the enthalpy of surface-adsorbed sulfur. Firstly, the developed model is validated against literature-based sulfur chemisorption isobars, and subsequently against electrochemical button-cell experiments displaying a significant influence of operation temperature and applied potential on cell performance and degradation.
It is shown that sulfur surface coverage increases with increasing current density indicating a low sulfur oxidation rate. In order to gain for an advanced fundamental understanding of sulfur poisoning, sensitivity analyses towards total anode resistance and sulfur coverage for different operating conditions will be presented.
Furthermore, the identified elementary sulfur poisoning reactions are used to extend an existing reaction mechanism for methane steam reforming which is then validated based upon a variety of electrochemical experiments. It is shown that atomically adsorbed sulfur significantly influences heterogeneous reforming chemistry, causing a substantial decrease in OCV. Under polarization, at constant current densities the cell voltage decreases in a non-linear way. After the removal of hydrogen sulfide from the feed gas the cell shows a faster recovery than in H2/H2O mixtures. In addition, numerical impedance simulations over a wide range of operating conditions were performed, which allows a physically-based assignment of observed gas concentration, heterogeneous chemistry and electrochemical processes.
Accomplishments, Status, and Road Map for the US Department of Energy's Fossil Energy SOFC Program
Authors: White Briggs M. , Lundberg Wayne L. , Pierre Joseph F. 
Published: February 2020

Development of electric power generation technology that efficiently and economically utilizes coal and natural gas while meeting environmental requirements is of crucial importance to the United States. The U.S. Department of Energy (DOE) Office of Fossil Energy (FE), through the National Energy Technology Laboratory (NETL), is leading the research and development of advanced Solid Oxide Fuel Cells (SOFC) as a key enabling technology. This work is being done in partnership with private industry, academia, and national laboratories.
Program participants are making significant progress toward commercialization. Milestones include: the development and validation of multiple generations of engineered seal concepts, cells with low degradation and high power density, development of integrated stack and system modeling tools, and validation of low-cost stainless steel interconnect solutions. With advances in cost reduction, the program is now focused on research to improve durability and reliability, especially in an integrated realistic system context. Integrated system tests at larger scales (10-100 kWe) are yielding respectable degradation rates in the 1 to 1.5%/1,000 hrs under cost-effective operating conditions.
In this presentation, these highlighted accomplishments will be reviewed along with the status of the program and a road map for the future.
Towards the Next-Generation of Solid Oxide Fuel Cell Systems
Authors: Singh Vaibhav , Wagner Patrick Hubert , Wuillemin Zacharie , Diethelm Stefan , Schiffmann Jürg , Van herle Jan 
Published: February 2020

Use of intermediate temperature solid oxide fuel cells for power generation is attractive, due to the highest achievable electrical efficiencies in the low power generation range. Nonetheless, there still exists a potential to improve the industry benchmark SOFC systems, which use natural gas or biogas as fuel and consider steam methane reforming, with external steam supply, for syngas production and usage in the stack.
Anode off-gas recirculation using a blower is the add-on to our next-generation SOFC system. Since the recirculating feed contains steam produced in the stack, no external steam supply is needed for reforming. This eliminates the use of expensive water de-ionisation sets. Further, it allows for high overall fuel utilization at low diffusion losses. System performance is evaluated through multi-objective optimization criteria, i.e. maximization of electrical efficiency and cogeneration efficiency. Evolutionary algorithms compare the different design alternatives, i.e. co-flow or counter-flow stack operation with hot or cold recirculation. The system flowsheet which includes models for BOP components and an inhouse experimentally validated SOFC stack model, is solved using the commercial software Belsim VALI.
The design variables identified for this system are 1. oxygen to carbon ratio before the external reformer 2. external to internal methane reforming fraction 3. reducing fuel species molar fraction at anode outlet 4. air-fuel equivalent ratio in the burner and 5. blower inlet temperature. Successive generations of population are obtained by reproduction and mutation of the existing population. Following the ‘survival of the fittest’ rule, the iteration is stopped when a non-dominated solution set represented by a Pareto-optimal front is obtained. The results obtained (eg. figure 1) suggest that improvements to the best SOFC systems, in terms of net electrical efficiency, are achievable.

Figure 1
Performance Characteristics of 100 W Carbon Fuel Cell Stack Based on SOFC Technology
Authors: Mushtaq Usman , Kim Sun-Kyung , Song Rak-Hyun , Lim Tak-Hyoung , Lee Jong-Won , Lee Seung-Bok , Park Seok-Joo 
Published: February 2020

Carbon Fuel Cells (CFCs) run on carbon-rich fuels such as coal and biomass. Owing to their high theoretical efficiencies, they have been studied as new stationary power generation. This work presents the fabrication and operation of a 100W SOFC-based CFC stack, consisting of 5 bundles with 6 tubular cells per bundle. 8 mol%Y2O3-stabilized ZrO2 (8YSZ) electrolyte and layers of La0.8Sr0.2MnO3/La0.6Sr0.4Fe0.8Co0.2O3 cathode were coated on Ni-8YSZ anode support, with an active electrode area of 60cm2 per cell. Six cells were embedded vertically on a fuel gas manifold and interconnected electrically in parallel within a bundle. Five bundles were sealed and stacked in series electrically. The stack was connected to carbon fuel chambers containing mixture of activated carbon and potassium carbonate. The carbon fuel mixture was agitated with carbon dioxide to promote reverse Boudouard reaction and thus providing carbon monoxide as stack fuel. The stack and the fuel chambers were operated simultaneously in a heating furnace. The CFC stack showed 111.5W at 850 oC and its average voltage degradation rate is 0.55 V/kh for 200hours. The CFC stack degradation during long-term operation was analyzed and discussed as related to microstructural change, poisoning by impurities and electrochemical cell polarization losses.
Anomalous Ohmic Loss in Solid Oxide Fuel Cells with Doped Ceria Interlayers
Authors: Zhou Xiao-Dong , Lu Z , Templeton J , Stevenson J W 
Published: February 2020

The ohmic resistance of an anode-supported SOFC is usually composed of contributions from the following parts: anode, electrolyte, cathode, and contact between the cell components. All of the ohmic resistances of cell components should be as small as possible to achieve an efficient SOFC operation. It is often believed that most of the ohmic resistance attributes to the electrolyte since the ionic conductivity of the electrolyte is usually several orders of magnitude lower than the electrical conductivities of the electrodes.
In an SOFC single cell with YSZ as the electrolyte, however, the contribution of the electrolyte to the total ohmic resistance of the anode-supported SOFC has not yet been fully understood despite of the numerous studies in this area. Several groups reported that the YSZ films in real SOFC environment showed lower ionic conductivities than that of the bulk YSZ material. This is especially true when the doped ceria is screen printed on YSZ-based single cell, in which the magnitude of the ohmic losses in the cell was observed more than three times greater than that for YSZ. The aim of this paper is to address the origin of the exaggerated ohmic resistance.