1,721,005 research outputs found
Thermal Energy Storage integration in electrical grids and in energy industries for decarbonization
Full text linkNello scenario mondiale attuale dove si rende necessario rispettare i limiti di emissione di gas serra per non valicare l’incremento della temperatura media globale, le fonti di energia rinnovabile dovranno sostituire i tradizionali combustibili fossili nella produzione di energia elettrica e termica nei vari settori incluso quello industriale. La non programmabilità intrinseca delle fonti di energia rinnovabili rende difficile far coincidere l’energia prodotta con la domanda in tempo reale. Per questo motivo, l’introduzione di sistemi di accumulo di energia è fondamentale, in quanto svolgono un ruolo chiave nel bilanciare la domanda e l’offerta. Questi sistemi consentono di immagazzinare l’energia in eccesso prodotta durante i periodi di bassa domanda, che può poi essere rilasciata quando la domanda è più alta, garantendo così un sistema energetico più stabile ed affidabile. Nei vari settori dove si necessità di energia, sono svariate le soluzioni che si propongono come tecnologia di accumulo. In questo lavoro di tesi di dottorato ci si focalizza sui sistemi di accumulo termico per la fornitura di vapore nel comparto industriale. In particolare, si presenteranno due tipi di sistemi di accumulo basati su letto fluidizzato di sabbia uno a carica solare diretta l’altro a carica elettrica. Entrambi i sistemi sono stati ideati e brevettati dalla Magaldi Power S.p.A. e denominati rispettivamente STEM® (Solar Thermo-Electric Magaldi) ed MGTES (Magaldi Green Thermal Energy Storage).
Per la tecnologia STEM®, per cui si prevede la carica solare, sono due gli aspetti innovativi da evidenziare: un algoritmo innovativo che prevede la correzione integrale degli errori di puntamento degli eliostati (specchi inseguitori solari) garantendo una maggiore efficienza di puntamento e quindi un incremento dell’energia solare raccolta all’interno dello letto fluido; l’utilizzo di un inclinometro biassiale per ogni eliostato, per aumentare la reiezione degli errori di puntamento dovuti a disallineamenti del terreno, migliorando così l’affidabilità del sistema.
Per la tecnologia MGTES, che prevede una carica termica mediante resistenze elettriche per effetto Joule, è stato realizzato uno studio per l’individuazione del sistema di riscaldamento più adatto al letto fluidizzato di particelle di sabbia. Sono state condotte simulazioni basate su modelli analitici confrontando elementi resistivi progettati per riscaldare attraverso conduzione, convezione e irraggiamento. Dopo la fase di simulazione, è stata realizzata una campagna di prove sperimentali per validare i risultati ottenuti dai modelli teorici, verificando l’accuratezza delle simulazioni e il comportamento reale dei sistemi di riscaldamento studiati.
Per identificare il metodo di riscaldamento più promettente, accanto alla valutazione quantitativa è stata eseguita un'analisi qualitativa, volta a valutare i fattori critici rilevanti per l'industrializzazione della tecnologia. Le considerazioni principali hanno riguardato la facilità di installazione, i requisiti di manutenzione, la sostituibilità dei componenti e la compatibilità della tecnologia con il mezzo di accumulo. È stata condotta un'analisi dei punti di forza, debolezza, opportunità e minacce, che comprendeva i principali fattori qualitativi menzionati. Le matrici risultanti sono state poi state strutturate per valutare sistematicamente questi aspetti.
Nello scenario proposto, in cui i sistemi di accumulo termici sono integrati nei distretti energetici, diventa essenziale un nuovo concetto di microgrid controllata. In questo contesto, sia i sistemi elettrici che quelli di accumulo termico richiedono una gestione ottimale. Un efficace Energy Management System (EMS) è fondamentale per l'utilizzo efficiente delle risorse energetiche distribuite. Tenendo conto di questi requisiti, è stata avviata una ricerca per sviluppare un modello di EMS volto ad ottimizzare i flussi di potenza per ridurre sia i costi energetici sia le emissioni di CO2. Questo argomento costituirà il fulcro dei futuri sforzi di ricerca.In the current global context, where it is essential to comply with greenhouse gas emission limits to avoid surpassing the increase in average global temperature, renewable energy sources must replace traditional fossil fuels in the production of both electrical and thermal energy across various sectors, including industry. The inherent unpredictability of renewable energy sources makes it challenging to align energy production with real-time demand. For this reason, the introduction of energy storage systems is crucial, as they play a key role in balancing supply and demand. These systems allow for the storage of excess energy produced during periods of low demand, which can then be released when demand is higher, ensuring a more stable and reliable energy system.
In the various sectors where energy is required, numerous solutions are being proposed for energy storage technology. This doctoral thesis focuses on thermal energy storage systems for steam supply in industrial applications. Specifically, two types of storage systems based on fluidized sand beds will be presented: one charged directly by solar energy and the other by electrical energy. Both systems were designed and patented by Magaldi Power S.p.A. and are named STEM® (Solar Thermo-Electric Magaldi) and MGTES (Magaldi Green Thermal Energy Storage), respectively.
For the STEM® technology, which uses solar energy for charging, two innovative aspects stand out: an advanced algorithm for the integral correction of heliostat (solar tracking mirrors) aiming errors, which improves aiming accuracy and consequently increases the amount of solar energy collected in the fluidized bed; and the use of a biaxial inclinometer for each heliostat, which helps to reduce aiming errors caused by ground misalignments, thus improving system reliability.
For the MGTES technology, which utilizes electric resistances to charge thermally through Joule heating, a study was conducted to identify the most suitable heating system for the fluidized bed of sand particles. Simulations were carried out based on analytical models, comparing resistive elements designed to heat through conduction, convection, and radiation. Following the simulation phase, an experimental testing campaign was conducted to validate the results of the theoretical models, verifying the accuracy of the simulations and the actual performance of the heating systems studied.
To identify the most promising heating method, a qualitative analysis was performed alongside the quantitative assessment, aimed at evaluating critical factors relevant to the industrialization of technology. Key considerations included ease of installation, maintenance requirements, component replaceability, and compatibility of the technology with the storage medium. A strengths, weakness, opportunities, and threats analysis was conducted, encompassing the primary qualitative factors mentioned. The resulting matrices were then structured to systematically evaluate these aspects.
In the proposed scenario, where thermal storage systems are integrated within energy districts, a novel controlled microgrid concept becomes essential. In this framework, both electrical and thermal storage systems require optimal management. An effective Energy Management System (EMS) is critical to the efficient utilization of distributed energy resources. Considering these requirements, research has been initiated to develop an EMS model aimed at optimizing power flows to reduce both energy costs and CO2 emissions. This topic will form the core of future research efforts
Modelling, optimisation and management strategies for a microgrid with integrated thermal energy storage
No full textThis paper presents a mathematical model of a multi-energy microgrid and, in particular, of a power-to-heat thermal storage system, and a novel management approach for the microgrid including the hybrid storage system. A model-based exhaustive optimisation is the core of an intelligent management strategy, which takes into account both forecast costs and production data obtained from publicly available databases. The management strategy is implemented for a case study describing an industrial facility with variable thermal energy demand. Various scenarios are simulated to evaluate the effects of the management technique and the integration of the hybrid electro-thermal storage system. The effectiveness of the management strategy is demonstrated in a scenario with high penetration of renewable sources. Here, only the management of the renewable surplus is optimally managed. The optimisation is also used to evaluate the competitiveness of the thermal storage technology in energy markets with energy congestion phenomena. The results highlight that combining thermal and electrochemical storage under a discrete optimisation framework can significantly reduce both operational costs and carbon dioxide emissions, particularly when integrated with intelligent forecast-based strategies, making this approach promising for the decarbonisation of energy-intensive industrial sectors
A Novel Endosurgical Prosthesis to Treat Thoracoabdominal Aortic Aneurysm in Complex Anatomy or Emergency Settings
No full textBACKGROUND: Despite improvements in operative techniques, open thoracoabdominal aortic aneurysm (TAAA) repair is complex and characterized by high mortality and morbidity rate. Less invasive techniques have been developed since 2005 for the treatment of TAAA. Unfortunately, many of these devices require custom fabrication, resulting in delay of many weeks until treatment can be delivered but crucial in critical emergency cases. We present a novel hybrid endovascular and surgical prosthesis, which was tested on five pigs, with the aim of reducing the barrier issues of endovascular therapy in such particular cases.METHODS: The principal characteristic of the proposed hybrid endovascular prosthesis is to combine a proximal and distal stented zones and, in between, a classical surgical blood tied Dacron prosthesis. The device was tested in five pigs where feasibility of implantation and acute postoperative outcomes were evaluated, including bleeding, bowel ischemia, renal function, and peripheral blood perfusion.RESULTS: In all cases, following laparotomy, the endoprosthesis was successfully implanted under fluoroscopy and the surgical prosthesis zone could be easily detected by the radio-opaque markers. No major bleeding or cardiac events occurred throughout preparation and implantation. One hour after prosthesis implantation and surgical anastomoses of all vessels were completed, normal urine output was registered, and no acidosis was detected.CONCLUSIONS: This novel graft has shown ease of endoprosthesis and visceral vessels implantation without the need of thoracotomy or extracorporeal circulation and may be useful in an emergency setting or high risk and complex anatomy TAAA unsuitable for traditional endovascular aneurysm repair, or to avoid an excess waiting time for a "custom made" prosthesis. The great adaptability of this "hybrid" prosthesis in complex anatomy for the majority of TAAA could be important in high-risk patients and in some difficult situations, such as a high risk of imminent rupture
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
A structural and 1H NMR relaxometric study on novel layered carboxyalkylaminophosphonate nanocrystals with Gd(III) ions located in the framework
No full textNovel Gd(III) carboxyalkylphosphonate nanocrystals were synthesized under mild hydrothermal conditions. Structural properties and 1H NMR relaxometric behaviour in aqueous solution as a function of the magnetic field strength were investigated, aiming to evaluate the local chemical environment of the paramagnetic centres and their interaction and affinity with water molecules
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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