1,720,956 research outputs found
Scheduling and operation of RES-based virtual power plants with e-mobility: A novel integrated stochastic model
No full textIn the present paper, an Energy Management System is proposed to optimally schedule and operate a Virtual Power Plant (VPP) composed of charging stations for e-vehicles, stationary batteries, and renewable energy sources. The model is capable to optimize the bidding process on the Day-Ahead Market (DAM) through a two-stage stochastic formulation, which considers the uncertainties affecting the evaluation of the energy required for the next day. The stochastic scenarios are generated through a Monte Carlo procedure and clustered by a reduced domain k-means algorithm. To manage in real-time the operation of the VPP, a new Rolling Horizon mixed-integer linear programming model is adopted. The effectiveness of the tools developed is proved by numerical simulations reproducing the different operating conditions of the VPP. The benefits of the approach are confirmed by extensive analyses performed over a 4-month period. An increase of the profits of 23 % compared to a non-optimized strategy and of 6 % with respect to a deterministic optimization is observed
Flexibility Provision by an Aggregate of Electric Boilers in the Italian Regulatory Framework
No full textThe present work provides a numerical evaluation of the flexibility that an aggregate of electric boilers can supply to the power system in the Italian framework. To this purpose, the paper firstly outlines the current national regulations regarding the provision of flexibility by distributed energy resources. Then, considering the Italian discipline as a reference, a sensitivity analysis is performed on the regulating capability of an aggregate of electric boilers. In the analysis, the effects on the users' thermal comfort are also taken into account. To control boilers, enabling the provision of ancillary services, a heuristic based on a Greedy-Indexing algorithm is proposed, while the hot water usage is simulated by real data. The heuristic strategy implemented resulted to be particularly effective, enabling the provision of services without introducing significant detrimental effects on the users' thermal comfort
Residential Users as Flexibility Providers: a Techno-Economic Analysis
No full textThe increasing spreading of generation affected by uncertainty and the gradual phase-out of fossil-based power plants are requesting many countries to open the Ancillary Service Markets (ASMs) to new actors, such as the aggregators. In this framework, this paper presents a study aimed to evaluate the regulating capabilities, from both a technical and an economic point of view, of an aggregate composed of residential users equipped with small-scale renewable power plants and flexible loads (V2Ge-vehicles, electrical water boilers). To this purpose, two numerical models are proposed: the former quantifies the flexibility that can be offered in the ASM, while the latter simulates the operation of the aggregate, assessing the flexibility available and evaluating the possible unwanted effects caused to the users in case of ancillary service activation. Extensive analyses are performed, considering the Italian scenario as a reference
Short-term uncertainty in the dispatch of energy resources for VPP: A novel rolling horizon model based on stochastic programming
Full text linkThe intermittent nature of distributed energy resources introduces new degrees of uncertainty in the operation of energy systems; hence, short-term decisions can no longer be considered fully deterministic. In this article, an energy management system (EMS) was proposed to optimize the market participation and the real-time operation of a virtual power plant (VPP) composed of photovoltaic generators, non-flexible loads, and storage systems (e-vehicle, stationary battery, and thermal storage). The market bidding process was optimized through a two-stage stochastic formulation, which considered the day-ahead forecast uncertainty to minimize the energy cost and make available reserve margins in the ancillary service market. The real-time management of regulating resources was obtained through an innovative rolling horizon stochastic programming model, taking into account the effects of short-term uncertainties. Numerical simulations were carried out to demonstrate the effectiveness of the proposed EMS. The architecture proved to be effective in managing several distributed resources, enabling the provision of ancillary services to the power system. In particular, the model developed allowed an increase in the VPP's profits of up to 11% and a reduction in the energy imbalance of 25.1% compared to a deterministic optimization
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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