1,720,956 research outputs found
Analisi delle prestazioni di un gruppo integrato cogeneratore con motore a gas e pannelli fotovoltaici
No full textOggetto dello studio è l'analisi sperimentale e la modellazione di un gruppo elettrogeno a gas naturale in assetto cogenerativo, con possibilità di inseguimento del carico termico od elettrico, abbinato ad un impianto fotovoltaico e ad un sistema di accumulo elettrochimico. Esso rientra in un più ampio progetto riguardante la generazione distribuita, denominato Enerplan, condotto da AREA Science Park in collaborazione con il Dipartimento di Ingegneria Civile e Architettura dell'Università degli Studi di Trieste. L’indagine sperimentale ha riguardato il rilievo di numerosi dati funzionali ed il calcolo dei rendimenti elettrici e termici in diversi assetti operativi. Inoltre è stato realizzato un modello di simulazione utile per valutare le prestazioni tecnico-economiche del sistema integrato e per condurre analisi sul comportamento dinamico del sistema in presenza di diverse strategie di controllo
Modeling and Performance Analysis of an Integrated System: Variable Speed Operated Internal Combustion Engine Combined Heat and Power Unit–Photovoltaic Array
Full text linkThe paper presents the model of a combined heat and power (CHP) unit, based on a variable speed internal combustion engine (ICE) interfaced with a photovoltaic (PV) system. This model is validated by means of experimental data obtained on an 85 kWe CHP unit fueled with natural gas and a PV system with a rated power of 17.9 kW. Starting from daily load profiles, the model is applied to investigate the primary energy saving (PES) of the integrated CHPþPV system in several operating conditions and for different sizes of PV array. The results demonstrate the dependence of the CHP performance on the operating mode and a limited convenience of the variable speed strategy. The integrated system operation leads to performance improvements, which depend on the size of the PV component
Analisi delle prestazioni di campi fotovoltaici in condizioni operative caratterizzate da bassi valori di irraggiamento
No full textIl presente lavoro analizza le prestazioni di due impianti fotovoltaici di taglia simile (15 – 20 kWp) ma basati su tecnologie differenti, in condizioni operative reali. Scopo dello studio è l’analisi delle prestazioni effettive degli impianti sul lungo periodo, separando gli effetti della variabilità delle condizioni ambientali da quelli dovuti alla variabilità del rendimento dei pannelli e dei componenti elettrici ed elettronici, e alla loro evoluzione nel tempo. Particolare attenzione è data all’influenza che le condizioni d’irraggiamento e la temperatura hanno sull’efficienza degli impianti
Analysis of the outdoor performance and efficiency of two grid connected photovoltaic systems in northern Italy
No full textThis paper analyzes and compares the actual performance of two grid connected photovoltaic plants, which are of similar size but based on different modules technologies. The facilities are located on the roofs of two buildings of Area Science Park in the site of synchrotron ELETTRA in Basovizza (Trieste). The first system is equipped with modules of mono crystalline silicon wafer surrounded by ultra-thin amorphous silicon layers (hetero-junction with intrinsic thin layer), facing south and tilted at 30°, the second is equipped with mono crystalline silicon modules oriented 35° west and inclined at 10°. The set of data analyzed in this paper has been systematically acquired from October 15th 2011 to October 14th 2012 by means of a dedicated monitoring system.
The aim of this study is to analyze the actual performances of the plants and their yearlong evolution, separating the effects of the variability of environmental conditions from those due to the variability of the performance of panels and electrical components. Particular attention is given to the influence that irradiance and temperature have on the efficiency of the system.
An analysis methodology was applied to appropriately filter, classify and normalize the data in order to identify the modules temperature coefficients as a function of irradiance and to compare their actual efficiency with those declared by the manufacturer. Acquired data and mathematical correlations will allow the development of accurate simulation models, useful for assessing the actual profitability of similar installations. The latter can be obtained through the main performance indices of the systems that are calculated and reported in this paper for the period of observation
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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