1,721,015 research outputs found
Design of a combined power, heating and cooling system at sized and undersized configurations for a reference building: Technoeconomic and topological considerations in Iran and Italy
No full textThe objective of the present paper is sizing of a technically optimum and economically feasible cogeneration system to supply heating, cooling and electricity to a reference building in the city of Pisa, Italy, for different months of the year. This cogeneration system is proposed in two operational modes, sized and under-sized, so that the effect of natural gas and electricity consumption costs on the system design can be achieved. To this end, the amount of energy consumption and cost of various types of the proposed cogeneration systems based on reciprocating engines are computed and compared. Afterward, in the proposed systems, for understanding the effect of the costs of the energy carriers in different countries on the rate of payback period, a comparison is conducted on the payback period between Iran and Italy. In the end, a sensitivity analysis is performed in Iran and Italy to survey the effect of any change in the cost of investment, natural gas, and electricity on the payback period. The results indicated that although the costs of gas and electricity are comparatively lower, the payback period is longer for Iran, which can be blamed on Iran’s higher discount rate (~50%). The results of sensitivity analysis showed that if the natural gas cost in Italy equals that of Iran, there would be a 6.4% reduction in the payback period and if the electricity cost consumption in Iran is taken equivalent to the cost of electricity in Italy, a decrease of 25% will appear in the payback period
Multi-objective optimization of a proposed multi-generation cycle based on Pareto diagrams: Performance improvement, cost reduction, and CO2 emissions
No full textEnergy system optimization is a significant task aimed at optimizing system operations and reducing costs and emissions. In this paper, an energy system is presented for multi-energy generation of power, heating/cooling, and desalination. First, the cycle's exergy, exergoeconomics, and environmental impact are analyzed. Then, optimization is performed using MATLAB software by applying a genetic algorithm (GA) and adopting 10 design parameters with two objective functions. The goal of optimization is to find the design variable values based on a Pareto plot that will increase the exergy efficiency while reducing cost and CO2 emissions. Scatter plots of the decision variables for the population indicate that objective functions can be optimized. Optimal values for the objective functions can be found by selecting lower values for the heat exchanger and evaporator's pinch-point temperature differences and higher values for the compressor pressure ratio, inlet temperature of the gas turbine (GT), isentropic efficiencies of air compressor (AC) and GT, and temperature of Rankine cycle evaporator. After optimization, exergy efficiency increased around 8.4%, cost dropped 14.8%, CO2 emissions were reduced by 1.2%, and the production of desalinated water increased about 7.6% using the proposed cycle. At the end of work, the influences of design variables on CO2 emissions as well as the total cycle cost are investigated in a parametric study
4E analysis of a modified multigeneration system designed for power, heating/cooling, and water desalination
No full textMultigeneration systems, owing to their efficient fuel utilization, are recognized as one of the best technical and economical methods of energy saving and climate control. In this paper, a multigeneration system is proposed for the production of power, heating/cooling, and desalinated water. The proposed system was first studied by means of an energy, exergy, exergoeconomic, and environmental analyses and the obtained results were compared with that of multigeneration systems described in the literature (the selected multigeneration systems are based on a gas turbine cycle as prime mover). In addition, a parametric study was used to investigate the effects of primary thermodynamic quantities such as air pre-heater outlet temperature, pinch-point temperature difference in evaporator, evaporator temperature of cooling cycle, and evaporator temperature of desalination system on cycle performance. Results indicated that the proposed cycle's power, heating, cooling, and desalinated water production is 30.5 MW, 40.8 MW, 1 MW, and 0.364 kg/s, respectively. In addition, the cycle's total cost and total CO2 emissions are 1943.5 $/h and 0.163 kg/kWh. The parametric survey showed that the air pre-heater outlet temperature and the gas turbine inlet temperature are the most influential parameters in changing the system's CO2 emissions. In this way, an increase of the pre-heater outlet temperature causes a 26% reduction in the cycle's CO2 emissions, whereas an increase of the gas turbine inlet temperature leads to a 53% increase in CO2 emissions
Developing an off-grid biomass gasification cogeneration system for Moroccan olive oil mills: Simulation, experimental validation, and 3E analysis
No full textApplying biomass gasification in combined heat and power systems (BCHPs) at olive oil mills is a sustainable
energy solution, which allows effectively managing waste, mitigating greenhouse gas emissions, and optimizing
investments by reducing biomass transportation costs. Morocco, a major global olive oil producer, has abundant
olive groves and mills generating substantial amounts of waste. However, limited research exists on utilizing
olive oil waste for BCHPs in Moroccan mills. This article proposes the construction of a BCHP in DARA mill,
Morocco, including studying residues from olive oil production, simulating the BCHP, validating the gasification
process through experiments, conducting energy, exergy and exergoeconomic analyses, and performing the
parametric study on system performance. In the experimental data, the equivalence ratio for olive cake and olive
pruning was obtained at 0.3 and 0.32, which agrees well with the simulated model by 0.31 and 0.315. The
energy analysis revealed that 30% of input energy is converted to useful energy, while 70% is wasted, resulting in
a 42% efficiency. From the exergy analysis, it was found that only 18% of the entered exergy is utilized as useful
exergy, while 68% is destroyed and 12% is lost, resulting in 19% efficiency Investment expenses contribute to
87% of system costs, with cost of exergy destruction accounting for the remaining 13%. The engine, gasifier, and
cleaning unit incur the highest exergy destruction and associated costs. Increasing both the air–fuel ratio (from
1.7 to 2) and water–fuel ratio (from 0.001 to 0.25) simultaneously leads to a 21% decrease in system exergy
efficiency, a 3% increase in investment costs, and a 10% increase in costs related to exergy destruction
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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