1,720,964 research outputs found
Redox flow batteries for energy storage
No full textThe concept of redox flow batteries (RFBs) is explained and their importance in grid level electrical energy storage is highlighted. The benefits of their modular configuration are linked to a flexible service operation, improved safety, recyclability, moderate costs and reduced environmental impact. Types of RFBs are classified and examples of their electrochemistry are provided, for both commercial devices and promising systems under development. Critical design features of electrodes, unit cells, cell stacks and balance of plant are summarized, together with the role of the power conditioner and the battery management system. Benefits and implications of electrolyte flow are considered and operational parameters affecting cell efficiency, performance and scale-up are given. These include cell resistance, reaction environment, mass transfer, shunt currents and pressure drop as well as cross-over through the membranes. Fundamental electrochemical and techno-economical figures of merit are surveyed. Failure mechanisms and durability are discussed. The scope of validated mathematical modelling and simulation in the design process of efficient RFBs is reviewed. The application of RFBs is illustrated at different scales and competition with other devices is briefly explored. Trends in RFB development and application opportunities are followed by further R&D needs
3D-printing of Redox flow batteries for energy storage: a rapid prototype laboratory cell
No full textAlthough interest in redox flow batteries (RFBs) for energy storage has grown over the last few years, implementation of RFB technology has been slow and challenging. Recent developments in 3D-printing of materials enable a transforming technology for fast, reproducible and documented cell manufacture. This technology can give an improved engineering approach to cell design and fabrication, needed to fulfil requirements for lower cost, longer lifetime hardware capable of efficient reliable performance. It can also be used to implement a flexible design methodology to suit various scales of operation, usually important during RFB development. In the case of electrolyte flow features, these needs are especially well met by fast prototyping strategies. This paper demonstrates the importance of 3D-printing for the realization of a hybrid zinc-cerium RFB laboratory cell. The design and fabrication process is described and the benefits offered by 3D-printing are considered. Finally, further opportunities offered by this approach to RFB manufacture and research are highlighted
The electrode kinetics of oxygen reduction: a case study. The corrosion of copper and its alloys in aqueous chloride solution at a smooth rotating disc electrode
No full textThe importance of oxygen reduction in corrosion processes is emphasized. The complex mechanism of this electrode process, due to 2- or 4-electron pathways, surface adsorption, and surface oxide formation resulting in possible passivity, is highlighted. Oxygen reduction can be controlled by charge (electron) transfer, mass transport of dissolved oxygen to the electrode surface, or both (mixed control). In practice, mixed control is common. Quantitative studies of the electrode kinetics of oxygen reduction at copper and its alloys and its simulation are illustrated by the use of a rotating disk electrode in aqueous chloride electrolytes at a temperature of 25°C. A variety of techniques is used to calculate the corrosion current density. The diffusion coefficient of dissolved oxygen if estimated via the Levich equation (under complete mass transfer control) and the Koutecky–Levich equation (under mixed control) is 1.9 ± 0.2 × 10−5 cm2 s−1 at 25°C. Other important cases of oxygen reduction in electrochemical technology are indicated, including gas and dissolved oxygen sensors, the negative electrode of metal-air batteries and fuel cell cathode reactions. Areas deserving further research and development are identified while broader subject areas include diverse bifunctional oxygen electrocatalysts for reversible batteries and regenerative fuel cells
3D-printed porous electrodes for advanced electrochemical flow reactors: a Ni/stainless steel electrode and its mass transport characteristics
No full textPorous electrodes have shown high performance in industrial electrochemical processes and redox flow batteries for energy storage. These materials offer great advantages over planar electrodes in terms of larger surface area, superior space time yield and enhanced mass transport. In this work, a highly ordered porous stainless steel structure was manufactured by 3D-printing and coated with nickel from an acidic bath by electrodeposition in a divided rectangular channel flow cell. Following the electrodeposition, the volumetric mass transport coefficient of this electrode was determined by the electrochemical reduction of 1.0×10−3 mol dm−3 of ferricyanide ions by linear sweep voltammetry and chronoamperometry. The convection diffusion characteristics are compared with other geometries to demonstrate the novelty and the advantages of 3D-printed porous electrodes in electrochemical flow reactors. Robust porous electrodes with tailored surface area, composition, volumetric porosity and flow properties are possible
Engineering aspects of the design, construction and performance of modular redox flow batteries for energy storage
No full textDespite many studies and several extensive reviews of redox flow batteries (RFBs) over the last three decades, information on engineering aspects is scarce, which hinders progress with scale-up and implementation of this energy storage technology. This review summarises cell design requirements then critically considers design, construction and cell features together with their benefits and problems, leading to good practice through improved cell performance, knowledge and experience. Techniques for the characterisation of the reaction environment are illustrated by measurements of mass transport to (and from) electrode surfaces as a function of flow conditions, as well as pressure drop and electrolyte flow dispersion. The effect of design features on performance is illustrated by the effect of process conditions on the components of cell potential. Adequate attention to engineering aspects is seen to be critical to the effective performance of RFBs, particularly during scale-up and long-term operation. Techniques for the characterisation of reaction environment are summarised and a list of essential design and construction factors is provided. Finally, critical areas needing research and development are highlighted
Electrochemical redox processes involving soluble cerium species
No full textAnodic oxidation of cerous ions and cathodic reduction of ceric ions, in aqueous acidic solutions, play an important role in electrochemical processes at laboratory and industrial scale. Ceric ions, which have been used for oxidation of organic wastes and off-gases in environmental treatment, are a well established oxidant for indirect organic synthesis and specialised cleaning processes, including oxide film removal from tanks and process pipework in nuclear decontamination. They also provide a classical reagent for chemical analysis in the laboratory. The reversible oxidation of cerous ions is an important reaction in the positive compartment of various redox flow batteries during charge and discharge cycling. A knowledge of the thermodynamics and kinetics of the redox reaction is critical to an understanding of the role of cerium redox species in these applications. Suitable choices of electrode material (metal or ceramic; coated or uncoated), geometry/structure (2-or 3-dimensional) and electrolyte flow conditions (hence an acceptable mass transport rate) are critical to achieving effective electrocatalysis, a high performance and a long lifetime. This review considers the electrochemistry of soluble cerium species and their diverse uses in electrochemical technology, especially for redox flow batteries and mediated electrochemical oxidation.<br/
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
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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