1,721,154 research outputs found
An implemented Operative-TCO analysis to assess the company cost of hydrogen compared to diesel and CNG-fueled buses
Full text linkIn the context of the transport sector's decarbonization efforts, targeting zero direct emissions in urban areas by 2040, Local Public
Transport (LPT) companies within the European Union (EU) are mandated with the task of fleet renewal, gradually replacing
internal combustion engine (ICE) vehicles with electric vehicles, including those powered by hydrogen fuel cells electric (HFCE).
Integrating novel vehicle technologies associated with the utilization of green energy carriers poses an additional challenge for LPT
companies concerning the management of service production costs.
For economic evaluation purposes, an effective method relies on Total Cost of Ownership (TCO) analysis, which encompasses
both fixed and variable costs associated with vehicles and their corresponding functional systems over their operational lifespan.
However, TCO analysis fails to encompass a segment of company costs attributable to operational vehicle performance aspects.
This paper proposes and elucidates an implementation of the Operative-TCO (OTCO) methodology, which additionally
incorporates costs stemming from vehicle operational constraints, such as mileage range and energy recharging time, as a function
of the service requirements along a designated route.
Utilizing data from the monitoring of an Italian LPT corporate fleet as a case study, the TCO and OTCO of green/grey-HFCE
vehicles are computed in comparison to diesel and compressed natural gas (CNG) vehicles. The findings are presented and
discussed in a comparative framework, inclusive of the assessment of emission-related costs
Control of Tethered Airfoils for High-Altitude Wind Energy Generation - Advanced control methods as key technologies for a breakthrough in renewable energy generation [Doctoral dissertation - Ph.D. in Information and System Engineering - Ciclo XXI - Politecnico di Torino]
No full textThis thesis is concerned with the development of an innovative technology of high-altitude wind energy generation and with the investigation of the related advanced automatic control techniques. Indeed, the problems posed by the actual energy situation are among the most urgent challenges that have to be faced today, on a global scale. One of the key points to reduce the world dependence on fossil fuels and the emissions of green-house gases is the use of a suitable combination of alternative and green energy sources. Renewable energies like hydropower, biomass, wind, solar and geothermal could meet the whole global energy needs, with minor environmental impact in terms of pollution and global warming. However, they are not economically competitive without incentives, mainly due to the high costs of the related technologies, their discontinuous and nonuniform availability and the low generated power density per unit area. Focusing the attention on wind energy, recent studies showed that there is enough potential in the total world wind power to sustain the global needs. Nevertheless, such energy can not be harvested by the actual technology, based on wind towers, which has nearly reached its economical and technological limits. The first part of this dissertation is aimed at evaluating the potential of an innovative high-altitude wind energy technology to overcome some of these limitations. In particular, a class of generators denoted as HAWE (High Altitude Wind Energy) is considered, which exploits the aerodynamic forces generated by the flight of tethered airfoils to produce electric energy. Numerical simulations, theoretical studies, control optimization, prototype experiments and wind data analyses are employed to show that the HAWE technology, capturing the energy of wind at higher elevation than the actual wind towers, has the potential of generating renewable energy available in large quantities almost everywhere, with a cost even lower than that of fossil energy.
Though the idea of exploiting tethered airfoils to generate energy is not new, it is practicable today thanks to recent advancements in several science and engineering fields like materials, aerodynamics, mechatronics and control theory. In particular, the latter is of paramount importance in HAWE technology, since the system to be controlled is nonlinear, open loop unstable, subject to operational constraints and with relatively fast dynamics. Nonlinear Model Predictive Control techniques offer a powerful tool to deal with this problems, since they allow to stabilize and control nonlinear systems while explicitly taking into account state and input constraints. However, an efficient implementation is needed, since the computation of the control input, which requires the real-time solution of a constrained optimization problem, can not be performed at the employed “fast” sampling rate. This issue motivates the research efforts devoted in the last decade to devise more efficient implementations of predictive controllers. Among the possible solutions proposed in the literature, in this thesis Set Membership theory is employed to derive off-line a computationally efficient approximated control law, to be implemented on-line instead of solving the optimization. The second part of this thesis investigates the methodological aspects of such a control strategy. Theoretical results regarding guaranteed approximation accuracy, closed loop stability and performance and constraint satisfaction are obtained. Moreover, optimal and sub-optimal approximation techniques are derived, allowing to achieve a trade-off between computational efficiency, approximation accuracy and memory requirements. The effectiveness of the developed techniques is tested, besides the HAWE application, on several numerical and practical examples
Combining Power-to-Heat and Power-to-Vehicle strategies to provide system flexibility in smart urban energy districts
No full textThe deployment of distributed renewable generation in urban districts requires managing local energy excess by means of distributed systems. Sector coupling strategies can be a solution to increase self-consumption, representing an alternative to electric batteries, however their limitations need to be assessed in order to properly plan urban systems.. This study investigates the potential role of heat pumps and smart charging of electric vehicles to provide system flexibility in residential neighbourhoods. Photovoltaic self-consumption, district self-sufficiency, annual costs and CO2 emissions have been assessed by simulating the district using the MATLAB toolbox for EnergyPLAN. Furthermore, the impact of the current energy market crisis has been evaluated. Cross-sector integration is crucial to improve system flexibility. Power-to-Heat system has a positive effect on all parameters, however its potential is limited. Power-to-Vehicle strategy is more effective and allows for doubling the community's self-consumption and self-sufficiency. However, the participation of vehicle owners in smart charging schemes is necessary. The combined implementation considerably improves energy, economic and environmental performance and turns out to be much more effective than electric batteries. Finally, the current increase in energy prices also improves the cost-effectiveness of electric batteries and makes the combined implementation of the three systems the best configuration
On the order reduction of the radiative heat transfer model for the simulation of plasma arcs in switchgear devices
No full textSimulation of stochastic systems via polynomial chaos expansions and convex optimization
No full text
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
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