1,720,969 research outputs found
Multilevel modeling of solid oxide electrolysis
No full textThis chapter discusses the methods of numerical modeling of solid oxide electrochemical cells operated in electrolysis mode. Techniques related to computer simulations of processes taking place in a high-temperature electrolyzer at the level of microstructure, cells, stack, and power systems with solid oxide electrolyzers (SOEs) are presented. A brief introduction to the key electrochemical and mass and energy transfer processes is followed by a discussion of numerical approaches, with particular focus on reduced order and lumped volume models. Numerical methodologies related to system-level studies, including both steady state (i.e., nominal and off-design) and dynamic operation, are presented for the purpose of characterizing the thermodynamic performances. This chapter presents recent advances in the numerical modeling of SOEs and provides a review of recent literature in the field
Off-design analysis of a micro-CHP unit with solid oxide fuel cells fed by DME
No full textAbstractThis paper presents the results of stationary off-design modelling of a micro-combined heat and power unit with solid oxide fuel cells. Mathematical models of the main components of the system with nominal power output of 1.6 kW were developed and implemented in the commercial modelling software Aspen HYSYS 8.0. The purpose of the study was to perform an analysis of possible operating conditions of the power system, using methodology which makes it possible to track changes in electrical and overall efficiency. Electrical load, fuel and oxidant utilization were varied to observe changes in performance of the micro-CHP unit. Performance maps were created to determine optimal working conditions to achieve either maximum electrical efficiency or power. The currently analysed system exhibits electrical and overall efficiencies exceeding 40% and 80%, respectively
Numerical model of planar anode supported solid oxide fuel cell fed with fuel containing H2S operated in direct internal reforming mode (DIR-SOFC)
No full textExperimental analysis of a planar 100 mm × 100 mm SOFC cell was conducted during operation at 1173 K in direct internal reforming (DIR) mode. In the first phase the rate of direct internal reforming was varied from 0 to 100% what corresponds to complete external reforming and complete DIR, respectively. In the second phase 1.2 ppm(v) of H2S was introduced to the feeding gas and the variation of the rate of direct internal reforming was repeated. Following the experimental analysis the numerical model was proposed to determine the correlation between the presence of the poisoning agent and the electrochemical performance. The effect on the resistance of the cell was studied. The lumped volume model was applied to predict the cell voltage. With the use of the experimental data it was possible to determine the relative change of the model parameters which describe the ionic and electronic conductivity of the SOFC. Model was adopted for predictive modeling of the solid oxide fuel cell, operated in DIR-SOFC mode with and without the presence of hydrogen sulfide. Additionally, literature data measured for a cell operated in complete internal reforming mode with variation of the sulfur content in the feeding gas were analyzed to define the effect of H2S content on the performance drop. Relative change of the resistance of a cell was correlated with the rate of internal reforming and the content of sulfur.
Results of the analysis show that the degradation of the performance of SOFC due to sulfur poisoning during operation in DIR mode can be modelled with high fidelity. Change of the ionic and electronic resistance of a cell accounted for the maximum of 34 and 53%, respectively when the rate of DIR was altered between 0 and 100%. The contribution of the sulfur poisoning accounts for 69 and 79% when the H2S content varies in the range of 0.001–5 ppm(v). With average relative prediction error below 3%, the proposed approach finds good application in simulating the performance of a cell exposed to different gas mixtures with different levels of sulfur in the fuel stream
Characterization of a circular 80 mm anode supported solid oxide fuel cell (AS-SOFC) with anode support produced using high-pressure injection molding (HPIM)
No full textThe current study was oriented at analyzing the performance of an anode-supported solid oxide fuel cell produced using high-pressure injection molding. The cell with a total thickness of 550 μm was produced in the Ceramic Department (CEREL) of the Institute of Power Engineering in Poland and experimentally analyzed in the Energy Department (DENERG) of Politecnico di Torino in Italy. The high-pressure injection molding technique was applied to produce a 500 μm thick anode support NiO/8YSZ 66/34 wt% with porosity of 25 vol%. The screen printing method was used to print a 3 μm thick NiO anode contact layer, 7 μm thick NiO/8YSZ 50/50 wt% anode functional layer, 4 μm thick 8YSZ dense electrolyte, 1.5 μm thick Gd0,1Ce0,9O2 barrier layer and a 30 μm thick La0,6Sr0,4Fe0,8Co0,2O3–δ cathode with porosity 25 vol%.
The experimental characterization was done at two temperature levels: 750 and 800 °C under fixed anodic and cathodic flow and compositions. The preliminary studies on the application of high-pressure injection molding are discussed together with the advantages of the technology. The performance of two generations of anode-supported cells is compared with data of reference cells with supports obtained using tape casting
Principles and applications of high temperature ion conducting ceramic in power generation - fuel cells and oxygen membranes
Full text linkHigh temperature membranes can be used in numerous applications including ceramic filters, selective sieves, removal of impurities, oxygen and hydrogen separation, electrochemical devices such as solid oxide fuel cells and solid oxide electrolysers. The fabrication process is oriented at achieving desired properties of the final product, including proper conductivity, size and density of pores, tortuosity, mechanical stability in high operating temperatures and others. Among the mentioned applications, solid oxide fuel cells and oxygen separation membranes represent materials with mixed ionic and electronic conductivity (MIEC) which will be further discussed in the lecture. Such material are often referred as membranes designed specifically for transport of ions and electrons
Modeling, design, construction, and operation of power generators with solid oxide fuel cells: from single cell to complete power system
No full textConsiderations regarding modeling of MW-scale IG-SOFC Hybrid Power System
No full textRES Master´s Thesis
Verkefnið er unnið í tengslum við Háskóla Íslands og Háskólann á AkureyriThe main objective of this thesis is to evaluate various modeling approaches for large systems employing high temperature fuel cell (particularly SOFC) modeling. It also includes a brief discussion of current trends and various designs. This thesis will review recently published papers investigating the hundred MWe scale SOFC hybrid Brayton-Rankine power systems. It goes into details discussing the crucial parameters influencing the cycle’s operation and performance. For better understanding, the basics of the fuel cell operation, involved processes and all phenonena are provided in Chapter 2.
In the next chapter the SOFC based systems with integrated gasification reactors are widely described. Current state-of-the-art trends and their background are presented. Finaly the desired system configuration is proposed and investigated. These particular arragements correspond to the U.S. Department of Energy (DoE) baseline for systems employing high temperature fuel cells, hence certain design solutions are involved. The SOFC stack feedstock is provided by the gasification of coal, however different fuel can also be gasified (biomass for example).
In the last chapter, the modeling and optimisation in the software are extensively described. Because of the fact that ASPEN Plus and Hysys are comonly used in the majority of cases when cycles involing high temperature fuel cells are analyzed, the attention will be focused on these two programs. Both of them have built-in tools allowing the modeling of heat exchangers, compressors and expanders (i.e. gas and steam turbines) by available units. ASPEN Plus is Fortran based software and the SOFC stack can be modeled as a user unit using this programming code. The modeling approach to the electrochemical and chemical processes within the SOFC stack will be delivered, since it is important for the modeling of the entire power cycle. Analysis of the whole system with the proposed tools allows the determination of the overall system thermal efficiency with high fidelity, thus the biggest effort must be made to correctly determine all input parameters and define the proper assumptions as well as simplifications. The final discussion emphasises the most crucial parameters.
The proposed system represents a clean energy source, which substantialy reduces the polutants flow associated with the power generation. Desulphurisation and gases clean-up processes are also involved in the cycle, therefore it meets all environmental requirements
Modeling, Design, Construction, and Operation of Power Generators with Solid Oxide Fuel Cells From Single Cell to Complete Power System
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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