1,720,954 research outputs found
Small scale solar tower coupled with micro gas turbine
No full textThis paper studies a small-scale CSP system composed of a solar tower and a recuperative air micro gas turbine (i.e. net power in the 100–200 kWe range). A code is developed to determine the optical performance of the heliostat field coupled with a secondary concentrator, while another code computes the thermal engine performance. The 832 m2 heliostat field layout is taken from a real plant, while the secondary optics is studied to maximize the optical-thermal efficiency. The selected secondary concentrator (CPC), with an aperture diameter of 0.5 m and an acceptance angle of 35° tilted of 52.5°, guarantees an overall optical efficiency of 77.9% in design conditions (Spring equinox, solar noon) and of 66.9% on yearly basis. For every Effective DNI (EDNI) and ambient temperature the turbine operation is optimized allowing to achieve a yearly solar-to-electricity efficiency of 16.3%. Summing up the cost of each component, an overall plant cost of about 2300 €/kW (peak) and a LCOE of 175 €/MWh are obtained. A sensitivity analysis on design EDNI, impacting on turbine size, is performed showing that its reduction from 700 W/m2 to 550 W/m2 allows reducing the LCOE down to 158 €/MWh, a value competitive with large-scale solar towers. The possibility of hybridization of plant (i.e. improving the gas turbine power output in selected hours, by means of biomethane or natural gas combustion) was considered to further reduce the LCOE
Innovative CSP tower system coupled with solar micro gas turbine
Full text linkLAUREA MAGISTRALE-In this thesis a complete thermodynamic, operational and economic analysis of a solar micro gas turbine is presented (design net power output of 187.3 kWel).
The heliostats field is taken from the existing plant of Aora in Almeria (Spain) while the tower receiver is optimized to give the maximum annual performances (optical efficiency of 72.02%).
Following a description of the components necessary to implement the power block, such as the volumetric receiver (allowing a higher maximum temperature with respect to a tubular receiver, respectively 1200°C and 800°C), a Matlab model is developed to simulate both on-design and off-design performances of the system. Technical constraints regarding the receiver, the recuperator, the combustor and the gas turbine engine (operating up to 950°C to avoid cooled-blade technologies) are accounted for a correct run. On-design conditions are characterized by a DNI of 950 W/m2 (peak flux in Sevilla) and an ambient temperature of 35°C, which correspond to an incident power from the sun of 790 W and the resulting solar-block efficiency is 32.99% while the solar-to-electric efficiency is 23.71%. The exergy analysis of the design system is also presented, highlighting a total second-law-efficiency loss of 74.51%, mostly due to the solar block (loss of 46.31%).
Referring to the GSE in Italy, a power plant can access renewable incentives while using an annual fuel-integration up to 15%. Thus, off-design conditions of the system also include hybridization.
Different strategies of operations are considered, such as the solar-only-mode (annual energy of 285.3 MWhel and annual ηsol-el of 0.2189), the nominal-power-mode with heavy fossil fuel firing (annual energy of 479.0 MWhel and annual ηsol-el of 0.2141), the maximum cycle efficiency mode (annual energy of 398.2 MWhel and annual ηsol-el of 0.2325), the hourly fuel-control of 15% (annual energy of 333.9 MWhel and annual ηsol-el of 0.2176) and the optimal renewable strategy with hybridization only when sun’s irradiation is low (annual energy of 339.0 MWhel and annual ηsol-el of 0.2239). A particular attention on CO2 emissions-savings with respect to a standard gas turbine is exposed.
Based on the reliable power-block costs (346.33 euro/kWe), and on the more uncertain solar-block costs (2444.24 euro/kWe), the final economic analysis is computed considering two possible discount rates, presenting a best scenario (LCOE of 0.2064 euro/kWh for the renewable strategy) and a worst scenario (LCOE of 0.2717 euro/kWh). Other economic parameters such as Net Present Value, Pay Back Time and Internal Rate of Return are calculated to evaluate the profitability of the project.
Finally a last case in view of a future where incentives wouldn’t be available anymore is considered, to understand if fuel-integration would be convenient or not. This analysis shows how the income increases with a higher hybridization, even though the profits remain negative
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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