1,720,962 research outputs found
Solutions for Retrofitting Catenary-Powered Transportation Systems Toward Greater Electrification in Smart Cities
Full text linkHighlights: What are the main findings? Catenary-powered transport systems do not need substantial infrastructure updates to support a huge increase in load demand that can reach up to 4 times the current daily energy demand. A neutral impact on the overall operational efficiency of the catenary system can be achieved if the round-trip efficiency of the converter–battery block is at least 90.0%. Some scenarios with bigger battery pack capacity require 94.4% of round-trip efficiency. What is the implication of the main finding? Scalability of catenary-powered systems: The work demonstrates that trolleybus networks (case study) are a scalable, robust, future-proof option for cities looking to electrify or expand their public transportation without incurring significant costs related to infrastructure reinforcement. Efficiency requirements for battery systems integration: Achieving the mentioned levels of round-trip efficiency for the converter–battery block might become more challenging, potentially requiring more stringent system monitoring and optimization. Catenary-powered networks are expected to play a pivotal role in urban energy transition, due to the larger deployment of electric public transport, in-motion-charging (IMC) vehicles, and catenary-backed electric vehicle chargers. However, there are technical challenges that must be overcome to ensure the successful utilization of existing networks without compromising vehicle performance or compliance with network standards. This paper aims to validate the use of battery energy storage systems (BESS) built from second-life batteries as a means of retrofitting catenary-powered traction networks. The objective is to increase the network robustness without creating a negative impact on its overall operational efficiency. Consequently, more electrification projects can be implemented using the same network infrastructure without substantial modifications. Furthermore, a power management scheme is presented which allows the voltage and current range allowed in the catenary network and the BESS maximum charging rate to be controlled from user-defined values. The proposed control scheme is adept at customizing the BESS size for the specific application under consideration. Validation is performed on a case study of the trolleybus system in Bologna, Italy
Performance Evaluation of DAB-Based Partial- and Full-Power Processing for BESS in Support of Trolleybus Traction Grids
Full text linkThe energy transition toward greater electrification leads to incentives in public transportation fed by catenary-powered networks. In this context, emerging technological devices such as in-motion-charging vehicles and electric vehicle charging points are expected to be operated while connected to trolleybus networks as part of new electrification projects, resulting in a significant demand for power. To enable a significant increase in electric transportation without compromising technical compliance for voltage and current at grid systems, the implementation of stationary battery energy storage systems (BESSs) can be essential for new electrification projects. A key challenge for BESSs is the selection of the optimal converter topology for charging their batteries. Ideally, the chosen converter should offer the highest efficiency while minimizing size, weight, and cost. In this context, a modular dual-active-bridge converter, considering its operation as a full-power converter (FPC) and a partial-power converter (PPC) with module-shedding control, is analyzed in terms of operation efficiencies and thermal behavior. The goal is to clarify the advantages, disadvantages, challenges, and trade-offs of both power-processing techniques following future trends in the electric transportation sector. The results indicate that the PPC achieves an efficiency of 98.58% at the full load of 100 kW, which is 1.19% higher than that of FPC. Additionally, higher power density and cost effectiveness are confirmed for the PPC
High-Precision Model for Accurate Simulation of Trolleybus Grids: Case Study of Bologna
Full text linkThe integration of renewable sources to catenary-powered electric traction systems is a paramount step to satisfy sustainability and smart city objectives, albeit necessitating accurate simulations of the infrastructure. This paper presents an innovative trolleybus network simulator, characterised by the modularity of the catenary model and built on an intuitive graphical user interface that offers significant topological change flexibility. The model is distinguished by high precision and moderate processing effort, bridging the gaps of existing block-based simulation tools. A graphical analysis of the voltage distribution evaluated in a section of Bologna's trolleybus network shows the advances in precision of the proposed model
Modelling Trolleybus Networks: a Critical Review
Full text linkThe trolleybus system is already part of the urban environment of several metropolitan cities. In view of the emergence of smart cities, it appears reasonable to look at how the trolleybus grid can become a more active part of the urban's electricity network. However, the infrastructure design approaches adopted so far make the current trolleybus networks overdesigned to handle the improbable worst-traffic case scenarios. Consequently, the trolleybus electrical supply system is both underutilized and oversized. Through modeling, simulations, and a cluster of measured trolleybus and corresponding network data, various new functionalities may be explored, among which electric vehicle chargers and energization of auxiliary equipment, towards a more sustainable and smart trolleybus grid. This paper merges the authors' engineering knowledge and sources available in the literature on designing and modelling trolleybus networks and performs a critical review of them to lay the foundations for proposing possible optimal alternatives. Being the city of Bologna organized with multiple electrically powered zones with either basic or complex topologies, the respective trolleybus system has been chosen as a case study
Retrofitting Catenary-Powered Transport Systems Toward Greater Electrification
No full textElectric transportation is expected to play an important part in the urban energy transition as catenary-powered networks become more widely deployed. However, technological problems must be overcome to ensure that current networks can be used successfully without sacrificing vehicle performance and network technical compliance. This research seeks to justify the usage of battery energy storage systems (BESS) as a retrofitting solution for catenary-powered traction networks. The goal is to strengthen the network without compromising overall operational efficiency, allowing additional electrification projects to be executed using the same network infrastructure without significant changes. To achieve this objective, solutions using second-life batteries (SLB) are compared with scenarios involving new batteries and alternative strategies, such as reinforcing critical catenary points and implementing voltage regulation in substations. The results show that, although SLBs from decommissioned vehicles present a viable solution, they require battery capacities at least four times greater than those needed for solutions using new batteries
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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