1,721,022 research outputs found
Comparison of the solid oxide fuel cell system for micro CHP using natural gas with a system using a mixture of natural gas and hydrogen
No full textSolid oxide fuel cell systems for combined heat and power production (SOFC μCHP) fueled by natural gas are attractive because of their high electrical and total efficiency even at small scale. The development of a hydrogen economy will increase the availability of distributed hydrogen as a pure gas. Alternatively, hydrogen may be blended with natural gas in the grid. This study investigates the performance of SOFC μCHP systems, while using a fuel varying from pure hydrogen to pure methane via mixtures of hydrogen and methane called Hythane. Flowsheet models of external as well as internal reforming fuel cell systems were developed in Cycle-Tempo simulation software. Results show that both the external as well as the internal reforming system can operated on all fuel gas compositions varying from pure hydrogen to pure methane, thus allowing for a transition towards a hydrogen economy via the mixing of hydrogen into the natural gas grid. Although the natural gas based systems have a higher electrical efficiency, the introduction of hydrogen into the gas leads to a higher total efficiency of the combined heat and power system. The addition of hydrogen into the fuel minimizes the problems of thermal stress and thermal shock associated with the use of methane in internal reforming fuel cell systems. The internal reforming system showed a higher performance compared to the external reforming system for all Hythane gas mixtures in terms of not only electrical efficiency but also in terms of thermal and total efficiency.Economics of Technology and Innovatio
H2S poisoning contamination effect on solide oxide fuel cell
No full textFuel Cells (FC) are offering global opportunities of an efficient energy system based on hydrogen technology. There are still some technical issues that have to be solved to reach the goal of large scale distribution of fuel cell based conversion systems. High temperature FC (HTFC) seems to be the most suitable to be used with current fuels, mainly methane from natural gas or syngas from biomass gasification. The main problem with these fuels is the contamination with H2S. The article investigates the resistance level of SOFC to H2S by electrochemical testing. The tests measure the effect on polarization of H2S introduction at increasing concentration and investigates the possibility of recovering with standard hydrogen concentration. The analysis is a first step to a complete model that predicts the effect of H2S in solid oxide fuel cells depending on fuel cell type, anode design and operation conditions
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
Electrochemical Impedance Spectroscopy study on ammonia-fed Solid Oxide Fuel Cells
Full text linkThe use of ammonia as a fuel is one of the promising pathways to decarbonize the energy sector. When ammonia is converted into power in the so-called "Ammonia-to-Power", the most interesting technology is the Solid Oxide Fuel Cell (SOFC) that can operate directly with ammonia and reach high performance in terms of efficiency. SOFCs are a high-efficiency and, potentially, low-cost technology, but still suffer from degradation issues related to internal losses. An innovative experimental technique to evaluate losses evolution caused by degradation is electrical impedance spectroscopy (EIS), followed by measurement data post-processing through the Distribution of Relaxation Times (DRT) analysis. In this study, a single SOFC is studied with a combined EIS and DRT methodology, when operating with a gas mixture of hydrogen, nitrogen and ammonia. The results identify the contribution to DRT of fuel dilution and the internal ammonia decomposition reaction
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Characterization of a 100 W SOFC stack fed by carbon monoxide rich fuels
No full textThis paper presents the evaluation of the performance of a 100 W Solid Oxide Fuel Cell (SOFC) stack with CO rich fuels as anode gas. The study aims at measuring the Open Circuit Voltage (OCV) and the Area Specific Resistance (ASR) when the amount of CO in the anode flow varies from 0 to 40% in volume. At the same time, the FCTestQA procedures were applied and evaluated as methodology for Solid Oxide Fuel Cell testing. The theoretical OCV was measured considering both H2 and CO oxidation and the water gas shift reaction. The OCV values, as a function of CO concentration, resulted closely related to theoretical ones and the ASR value, calculated for different mixtures of fuel, did not change with anode gas composition and it seemed to be a function of the temperature and the degradation of the materials only
Analysis of ICE-to-Electric Powertrain Conversion for a Small Size Waste Collection Vehicle
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