1,720,988 research outputs found
An input-to-state stabilizing discrete-time adaptive control scheme for Concentrating Solar Power systems
No full textThe development of advanced solar thermal parabolic trough collectors fields for electrical power generation calls for the conception of simple but effective temperature control strategies capable to cope with the nonlinearities and the uncertainties that typically affect this kind of plants, which are mainly due to the variability of thermal and optical parameters among the collector modules. For plants in which multiple temperature measurements are available for each string of collectors, as in the case of the molten-salt technology under exam, an adaptive control strategy is proposed. It relies on the combined use of a discrete-time nonlinear model-based controller with an on-line parameter adaptation mechanism based on error-projection. Under a persistency of excitation assumption, the input-to-state stability of the resulting closed-loop system with respect to bounded unstructured uncertainties can be proven. Simulation results show that the proposed control policy allows to effectively control the plant in various operating scenarios. © 2009 EUCA
Dynamic simulation of the operation of a molten salt parabolic trough plant, comprising draining procedures
No full textThe dynamic simulation of a molten salt operated parabolic trough plant is presented. The simulated plant is a typical 9 MWe CSP unit comprising 10 loops with 8 collectors in series (in turn this can be a "module" of a larger CSP solar field) a Two Tanks TES and a molten salt Steam Generator. This type of plant represents a challenge due to the large extension and relative complication of piping network operating with molten salt, in comparison to e.g. a molten salt Tower. The simulation model, implemented in Isaac Dynamics environment, is able to represent the normal operation of the plant with circulating HTF at variable mass flow depending on input DNI, and night circulation at reduced mass flow. In addition, in molten salt operated CSP plants draining operations are of prominent importance, given that these operations should be operated within a due time (depending on boundary conditions) avoiding the possible freezing of the salt mixture. Moreover also emergency draining (e.g. as a consequence of faults in the pump and/or in heat trace equipment) should be analyzed. At this purpose, the model has been modified and utilized to represent also circuit draining, involving flow reversal, that normally requires use of specialized thermo-hydraulic codes like Relap (Reactor Loss of coolant Analysis Program). In conclusion, the paper shows how the simulation environment is able to represent most of the dynamics that affect the operation of a molten salt parabolic trough plant. © 2013 The Authors
A novel wind turbine with permanent magnet generator for wind energy exploitation in very cold climates
No full textModeling and control of concentrating solar power systems: a discrete-time adaptive scheme for temperature control in molten salt solar collectors fields.
No full textMany different solutions have been developed in the last few years to concentrate the solar radiation for generating electrical power. Among the existing thermo-electrical Concentrating Solar Power technologies, parabolic trough fields are the most mature and one of the most suited for the application to large-scale plants. In this framework, the use of molten salts as Heat Transfer Fluid can provide major improvements to the parabolic trough technology. On the other side, the development of advanced molten salts plants calls for the conception of simple but effective temperature control policies able to cope with hard constraints and with the uncertainties that typically affect solar trough fields, which are mainly related to the variability of thermal and optical parameters among the collector modules. For plants in which multiple temperature measurements are available for each string of collectors, as in the case of the molten-salt technology under examination, an adaptive control strategy is proposed, which is aimed at satisfying the strict control requirements posed by the considered class of solar plants. The devised strategy relies on the combined use of a discrete-time nonlinear modelbased controller with an on-line parameter adaptation mechanism. Simulation results show that the proposed control policy, together with a specific constraints-handling strategy, allows one to effectively control the plant in various operating scenarios
An input-to-state stabilizing discrete-time adaptive control scheme for concentrating solar power systems
No full textThe development of advanced solar thermal parabolic trough collectors fields for electrical power generation calls for the conception of simple but effective temperature control strategies capable to cope with the nonlinearities and the uncertainties that typically affect this kind of plants, which are mainly due to the variability of thermal and optical parameters among the collector modules. For plants in which multiple temperature measurements are available for each string of collectors, as in the case of the molten-salt technology under exam, an adaptive control strategy is proposed. It relies on the combined use of a discrete-time nonlinear model-based controller with an on-line parameter adaptation mechanism based on error-projection. Under a persistency of excitation assumption, the input-to-state stability of the resulting c-l system with respect to bounded unstructured uncertainties can be proven. Simulation results show that the proposed control policy allows to effectively control the plant in various operating scenarios
Modelling and Simulation of the Thermo and Fluid Dynamics of the “Archimede Project” Solar Power Station.
No full textThe Archimede Project, developed by ENEA, is shortly presented, along with the problems related to the operating of a wide industrial size high temperature solar power station.
The importance of a reliable simulation tool able to predict the behavior of the plant in the design of control strategies is high-lighted. The innovative thermo fluid dynamic models of the plant, developed on the Matlab/Simulink® platform, are presented.
The applications of these models to the experimental PCS facility allowed to demonstrate their reliability and to consider their use in the simulation of the complex network of the Priolo Gargallo solar power station, in order to study control strategies and to match controllers to the mathematical model of the plant
Power production of an ORC system using a stratified molten salt as thermal energy storage integrated in a CSP plant
No full textThe use of Organic Ranking Cycle (ORC) systems to produce electrical energy in Concentrating Solar Power (CSP) plants has been significantly increasing over the recent years, mainly for small size plants [1-2]. The project ORC-PLUS, in the frame of Horizon2020, aims to deepen this aspect for an existing CSP plant located in a desert area at Ben Guerir in Morocco and using linear Fresnel collectors as well as thermal oil as heat transfer fluid (HTF). This plant foresees mainly two different operative modes: during daytime with sufficient Direct Normal Irradiance (DNI) an Organic Rankine Cycle (ORC) system is directly coupled to a 7 loops solar field; after sunset the ORC is fed by a thermal storage coupled to an additional solar field consisting of 3 loops. In the same context the performances of a stratified molten salt as thermal energy storage (TES) are deepened at ENEA CR Casaccia in Italy. Aim of this paper is the analysis of the power production of the 1 MWe ORC system present in the plant, under different operating conditions using a proper computing model
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
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