1,720,965 research outputs found
Hierarchizing Energy Saving Strategies in Wine Industry by Advanced Modelling of Chilling Units Operation
No full textWineries are energy intensive industries and in order to make the production process more sustainable, solutions for an efficient use of energy should be implemented. Large surveys conducted in the wineries sector have highlighted the importance of performing accurate energy audits and have identified in the installation of efficient cooling/refrigeration systems the most promising solutions in a variety of cases. Unfortunately, the savings achieved by such energy efficient solutions is often calculated by highly simplified approaches, which do not take into consideration the actual operating conditions of the equipment (highly variable on a seasonal and daily basis). In this paper a systematic and novel procedure is presented, aimed at developing reliable cooling load profiles for refrigeration and air-conditioning and identifying to what extent more efficient chilling units could countribute to reduce the electricity consumption. With this purpose, the use of Seasonal Energy Efficiency Ratios is critically analyzed, proving the need for seasonal indicators customized on the actual operating conditions of the chillers. The proposed method is applied to a winery producing still red and white and sparkling wines, for which only aggregated energy consumption data are available
Methodologies for the evaluation of polygeneration systems
No full textPolygeneration is widely recognized as one of the most promising technologies for the rational and efficient use of energy in industrial and civil sectors. Due to the simultaneous production of multiple outputs and the unsteady operating conditions observed in a number of applications, a systematic assessment of the economic, energetic, and environmental performance requires the use of appropriate indicators and approaches. In this chapter a brief overview of such evaluation methods is presented, clarifying the main strengths and weaknesses of each of them and providing a solid conceptual basis to address the controversial arguments. The overview necessarily covers the main assessment methods adopted in national and sovranational legislative frameworks, and it also includes some interpretive approaches such as thermoeconomic and exergoenvironmental analysis. Regarding the last point, a number of case studies discussed in the literature have been briefly presented to illustrate the proven capabilities and drawbacks of the different approaches
Potential applications of Salinity Gradient Power-Heat Engines for recovering low-temperature waste heat in cogeneration plants
No full textSalinity Gradient Power-Heat Engine is an innovative technology able to convert very low-temperature heat into electricity. Energy and economic benefits could be achieved by integrating this technology into cogeneration plants, where the exploitation of waste heat available during the operation could increase the revenues arising from “High-Efficiency” labels. For the first time, this paper proposes two potential applications in this field, and three illustrative case studies are purposely investigated. In the first case study, a salinity gradient-heat engine converts the waste heat available from a cogeneration plant serving an industrial process. In the second case study, a salinity gradient-heat engine is integrated into a cogeneration plant coupled to a district network. In the third case study, the possibility to reduce the size of a cogeneration plant by coupling this engine with a heat pump is investigated. The analysis relied on simplified models of the integrated systems which were numerically solved. Results for the first case study show an increase of 10.6% in revenues from the high-efficiency support mechanism and electricity selling. In the second case study, the primary energy saving increases from 8.7% up to 10.1%, thus achieving the threshold value for “High-Efficiency” eligibility. In the third case study, the heat engine allows to reduce up to 12.1% the nominal capacity of the prime mover. A prospective analysis of the integration of salinity gradient-heat engine in cogeneration plants is thus presented, and it poses a fundamental reference for future integration of this novel technology into these energy systems
An integrated approach based on Life Cycle Assessment and Thermoeconomics: Application to a water-cooled chiller for an air conditioning plant
No full textA large number of methods for energy systems analysis were developed in the last decades, aimed at acquiring an in-depth understanding of plant performances and enabling analysts to identify optimal design and operating conditions. In this work an integrated approach based on Life Cycle Assessment and Thermoeconomics is proposed as a method for assessing the exergo-environmental profile of energy systems. The procedure combines the capabilities of these two techniques, to account simultaneously for aspects related to thermodynamics of energy conversion processes and to the overall impacts along the plant life cycle related to other phases, i.e. from raw material extraction to the disposal of facilities. The capabilities of the method are illustrated by applying it to a water-cooled vapor compression chiller. After developing an accurate analysis of plant design and bill of materials of the chiller, the exergo-environmental profile was obtained. Then, the method was used as a decision support tool by considering a number of scenarios concerning possible design alternatives, context conditions and levels of maintenance. Results showed that the exergo-environmental performance of the chiller is highly sensitive to the electricity generation mix, which influences the trade-offs between the energo-environmental impacts related with plant operation and constructio
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
Energy assessment of a dish-Stirling system powering a reverse osmosis plant for seawater desalination
No full textWater scarcity in many regions of the world and the global demographic growth make the desalination of seawater and/or brackish an effective solution to meet the growing demand for freshwater. Nowadays, reverse osmosis has the largest share of the global installed desalination capacity. The impelling need to reduce greenhouse gas emissions has been pushing the search for sustainable technologies to produce the electricity needed to power reverse osmosis plants.
Among solar technologies, little attention has been paid to the possibility of powering reverse osmosis with electricity from the dish-Stirling concentrator. To fill this knowledge gap, this paper assesses the energy-saving potential of a reverse osmosis plant coupled with a cogenerative dish-Stirling concentrator on a small island in the Mediterranean Sea. A model of the integrated systems was developed based on data measured on a real dish-Stirling concentrator, and variation of the energy consumption of the reverse osmosis plant with the temperature of the feedwater solution was also accounted for. Hourly simulations showed that almost 36% of the annual water demand could be covered by driving the plant using electricity from the concentrator, and the solar fraction of the electricity consumed by the reverse osmosis
plant accounted for 57%. Finally, the analysis revealed that only a 1% decrease in solar fraction resulted when the heat recovered from the concentrator is not used for the feedwater preheating
Performance maps for an air-cooled air conditioning system as a preliminary instrument for the diagnosis of evaporator fouling
Full text linkDuring the past few decades, there has been increased interest in the development of automated approaches for detecting and diagnosing faults in air conditioning systems. One diagnostic approach involves the use of exergy analysis. As a first step towards understanding the application of exergy analysis to diagnostics, this work is focused on the thermodynamic and exergy analysis of a direct expansion air conditioning system used in small commercial building applications. The analysis was carried out by means of experimental activities on a 17.5 kW rooftop unit installed at the Herrick Laboratories, Purdue University, Indiana (USA). The system under investigation was equipped with a variable-speed compressor and variable-speed fans, thus allowing the unit to meet different loads without cycling on-off. A detailed mapping of the performance of this system was carried out by considering the effect of the outdoor temperature and the cooling load. In addition, the effect of evaporator fouling was considered.
Results showed that poor exergy performance are achieved, regardless the outdoor temperature and the cooling capacity tested. This fact is easily explained by considering the exergy destruction occurring in the evaporator. When testing evaporator fouling, exergy results showed that this fault contributed to increase mainly the consumption of the mechanical exergy of the air, thus allowing for an easy detection of this fault
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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