1,720,974 research outputs found
Energy-sustainable hospitals: Integration of a novel compound parabolic concentrator system with two storage tanks for domestic hot water production at high and low temperatures
No full textHospital buildings are known to be energy-intensive, since they are operated all year round at high costs, contain sophisticated medical equipment, and follow strict cleaning practices and environmental regulations. Domestic hot water consumption accounts for most of the energy consumption in hospital buildings. The objective of this research work is to study the energy performance of a novel compound parabolic concentrator system connected to two heat exchangers arranged in series, in turn, connected to two storage tanks that supply domestic hot water to two different hospital users. The first user requires high temperatures for laboratories, cleaning, sterilization of operating room instruments, and so on, while the second user requires lower temperatures mostly represented by health services. To guarantee the supply of the thermal energy needs, an external integration system was connected to each storage tank. A calculation scheme was created in a transient simulation environment that provides dynamically all temperatures at the output of the various system components and all thermal exchanges through each component. Starting from a reference configuration, a parametric simulation was carried out by varying the size of the plant components. The research aim was to
evaluate the influence of the component sizes on the plant’s transient behaviour by means of a qualitativequantitative determination of the monthly and yearly system energy exchanges and some performance indicators, such as the solar fraction, solar efficiency and fuel consumption on a monthly and yearly basis. The outcomes of this research demonstrated that the choice of the storage tank volumes and the secondary circuit flow rate allows designers to allocate the solar energy produced between the two users, while the collector area and the primary circuit flow rate allow designers to fix the fraction of overall thermal demand to be satisfied and the efficiency of solar energy conversion into thermal energy to the fluid. Finally, similarly to the f-chart method, some empirical correlations are proposed to rapidly verify the system performance without using any transient simulation tool
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
A multilayer panel in cork and natural phase change materials: thermal and energy analysis
Full text linkThis paper presents thermal and energy analysis of a multilayer panel in bio-based cork material and natural phase change materials (PCMs) for the development of prefabricated, recyclable and energy-efficient and autonomous building modules. For this purpose, a calculation tool is developed for the dynamic simulation of the thermal and energy behaviour of the sandwich panel. In particular, through an extensive parametric survey, the panel is sized with the identification of the arrangement of the layers, PCM temperature, and layer thicknesses to optimize the insulating and damping properties, considering typical climatic conditions of the Mediterranean climates of Southern Italy. From the conducted simulations, the types of sandwich panels that have the best insulating and storage characteristics for the building module construction were chosen. The results of these simulations will be used in future research for the preliminary design of tests to be carried out in a climatic chamber and to build a building module in real conditions to be constantly monitored through the automatic instrumental survey of internal and external physical quantities such as temperature, humidity and radiant temperature
Hourly forecasting of the photovoltaic electricity at any latitude using a network of artificial neural networks
Full text linkNowadays, special attention is paid to the importance of using photovoltaic (PV) systems to tackle the problem of climate change and the energy crisis. Artificial intelligence is currently used in different science fields for its great potential and accuracy in forecasting problems. In this work, a network of artificial neural networks (ANNs) was trained and validated to forecast the hourly worldwide electrical power produced by various PV modules, with different electrical characteristics. Each ANN describes the worldwide performance of each PV module on the optimal inclination angle. The training data consists of the hourly air temperature, horizontal total solar radiation as input data and electrical power produced as output. The power is obtained from the hourly simulation of PV modules with an electrical circuit model in 24 localities at very different latitudes. The validation and generalization of the network were obtained by considering the six PV modules in further 24 localities and by considering two further PV modules in all 48 localities considered. The excellent results in terms of accuracy metrics confirmed that the network of ANNs is a reliable, simple and accurate tool that can be used to predict the hourly performance of any PV module in any location worldwide
Energy Independence of a Small Office Community Powered by Photovoltaic-Wind Hybrid Systems in Widely Different Climates
Full text linkHybrid renewable energy systems are an optimal solution for small energy communities’ energy supply. One of the critical issues is the strong correlation of these systems with outdoor climatic conditions. The goal is to make local communities increasingly energy independent. To this end, an in-depth analysis of the behaviour of hybrid photovoltaic (PV)–wind systems powering small office communities in 48 locations around the world characterized by widely varying climates was conducted. System sizes, assumed to be stand-alone or grid-connected, were varied, for a total of 343 system power configurations. Highest satisfied load fraction (SLF) values are obtained with a significant predominance of PV over wind; the trend is more pronounced in dry and continental climates (zones B and D according to the Köppen climate classification). The utilization factor (UF) values of 1 are rarely reached and never in the wind-only or PV-only configurations. In all climates, the grid energy interaction factor (GEIF) values of zero are never reached but come very close. The benefit-cost ratio (BCR) of grid-connected systems is significantly higher than stand-alone systems
Photovoltaic Performance Assessment in Different Weather Conditions Utilizing an Artificial Neural Network Ensemble
No full textThe adoption of Renewable Energy Sources (RESs), particularly solar Photovoltaic (PV) systems, is essential for sustainable energy systems. To enhance PV system performance, precise and efficient simulation tools are crucial. Conventional simulation methods often involve complex computations and lengthy processes. This research study presents an alternative approach to solar energy modeling by exploiting Artificial Neural Networks (ANNs) in order to improve the accuracy and reliability of simulations of photovoltaic systems. The investigation is carried out in two phases. First, six separate ANNs were constructed each dedicated to predicting the hourly electrical output for one of six different PV modules. and total horizontal solar radiation of 24 locations were entered as features, while the corresponding hourly output of a 5-parameter photovoltaic model served as output. ANNs were trained with varying numbers of hidden layer neurons, and the optimal number of neurons was determined based on common accuracy metrics. In the second, each ANN was subjected to validation considering 24 other locations, generating the corresponding hourly electric power forecasts. A comparative analysis was then conducted both in terms of accuracy metrics evaluated on an hourly basis and errors on the yearly energy produced. Optimal ANNs demonstrate high R-square values along with low root mean square error and mean absolute error values. Across different global locations and PV modules, accuracy diminishes but remains relatively elevated in regions with extreme temperature or solar radiation values
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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