Дисертації з теми "Coupled energy systems"
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1
Ezanno, Philippe. "Vibration localization and statistical energy analysis in coupled systems." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-06112009-063056/.
2
Liu, Daerhan. "Novel Strongly Coupled Magnetic Resonant Systems." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3717.
Анотація:
Wireless power transfer (WPT) technologies have become important for our everyday life. The most commonly used near-field WPT method is inductive coupling, which suffers from low efficiency and small range. The Strongly Coupled Magnetic Resonance (SCMR) method was developed recently, and it can be used to wirelessly transfer power with higher efficiency over a longer distance than the inductive coupling method.
This dissertation develops new SCMR systems that have better performance compared to standard SCMR systems. Specifically, two new 3-D SCMR systems are designed to improve the angular misalignment sensitivity of WPT systems. Their power transfer efficiency for different angular misalignment positions are studied and analyzed. Prototypes are built for both systems and their performance is validated through measurement. Furthermore, new planar broadband conformal SCMR (CSCMR) systems are developed that maintain high efficiency while providing significantly larger bandwidth than standard CSCMR systems. Such broadband CSCMR systems are used here for the first time to simultaneously accomplish highly efficient wireless power transfer and high data rate communication through the same wireless link. These systems that combine wireless power and communication are expected to enable next-generation applications with battery-less and “power-hungry” sensors. Example applications include implantable and wearable sensors as well as embedded sensors for structural health monitoring.
3
Pardo, García Nicolás. "Energy efficiency improvement of hybrid ground coupled HVAC systems from thermal energy generation and storage management." Doctoral thesis, Universitat Politècnica de València, 2009. http://hdl.handle.net/10251/6065.
Анотація:
Nowadays, the increasing of the energy consumption is producing serious
changes in the natural environment as the global warming. Around the 40%
of all greenhouse gas emissions in developed countries come from the building
equipments, where approximately 60% are produced by the air conditioning
systems. In this context, ground coupled heat pumps are an attractive solution
as air conditioning systems in commercial buildings due to their higher
efficiency compared with the conventional air to water heat pump. In fact,
the American Environmental Protection Agency recognizes ground coupled
heat pump systems among the most efficient and comfortable systems available
today. Nevertheless, the energy efficiency of the ground coupled heat
pumps could be improve by means a properly management of the di erent
equipments which form them.
The objective of the research of this PhD thesis will be the development
of management strategies in the air conditioning system based on the ground
coupled heat pumps to improve its energy efficiency at the same time that we
keep the thermal comfort in the conditioned areas. The energy management
strategies will be oriented in the three ways: combining of several generation
systems (ground coupled heat pump and air to water heat pump), decoupling
thermal generation from thermal distribution (by means a thermal storage
device) and strategies based on the management of the devices of the system
(by means of continuous regulation of them).
From the results of this research we can obtain two main conclusions.
The rst one is that a properly management of a system composed by a
thermal storage, an air to water heat pump and a ground coupled heat pump
produce an improvement of the energy efficiency around a 40% respect to a
conventional system and around a 18% respect to a geothermal system. The
second main conclusion of this thesis is that a properly management strategy
in continuous regulation of the devices which are part of a ground coupled ..Pardo García, N. (2009). Energy efficiency improvement of hybrid ground coupled HVAC systems from thermal energy generation and storage management [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/6065
Palancia
4
Lutz, Michael [Verfasser], and André [Akademischer Betreuer] Thess. "Coupled metal hydride systems for energy storage / Michael Lutz ; Betreuer: André Thess." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2021. http://d-nb.info/1234452863/34.
5
Heidel, Timothy David. "Tradeoffs between revenue enhancements and emissions reductions with energy storage-coupled photovoltaics." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/52755.
Анотація:
Thesis (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 111-114).
Energy storage has the potential to dramatically change the operation of photovoltaics by allowing for a delay between generation and use. This flexibility has the potential to impact both the revenue from generating electricity using photovoltaics and the associated emissions reductions. This thesis attempts to quantify the impacts of adding energy storage to photovoltaics. The thesis formulates an optimization problem to solve for the optimal use of photovoltaics with energy storage from 2000 to 2005 in New England. The optimization is first solved using perfect information about historical solar generation, energy prices, and marginal emissions rates. Then, the model is solved using forecasted energy prices and emissions rates. The analysis finds that adding energy storage to photovoltaics can increase annual revenues by over 30%. With energy storage capacity and power equal to solar capacity, annual revenues were found to increase between 19.3% and 31.1% with an energy storage efficiency of 100%. Unfortuneately, the potential revenue increases were found to fall to between 9.1% and 21.3% with 80% efficient storage and between 3% and 14.5% with 60% efficient storage. However, when owners utilize energy storage to maximize revenue, the changes in avoided emissions with energy storage are found to be negligible. Alternatively, it is possible to achieve significant increases in the emissions offset by photovoltaics with energy storage. However, when energy storage is utilized to maximize emissions reductions, revenue decreases.
(cont.) This tradeoff between the economic and environmental benefits that can be achieved when energy storage is added to photovoltaics means it is unlikely to be possible, without policy, to simultaneously achieve large increases in both revenue and avoided emissions. Policy mechanisms could be used to enable energy storage to enhance both the revenue from photovoltaics and avoided emissions.
by Timothy David Heidel.
S.M.in Technology and Policy
6
Kyriakodis, Georgios-Evrystheas. "Development of a coupled simulation tool for urban building energy demand, district energy systems and microclimate modeling." Thesis, La Rochelle, 2020. http://www.theses.fr/2020LAROS028.
Анотація:
Ce travail de thèse aborde les liens complexes entre les processus physiques urbains, par le développement de modèles couplés pour tenir compte simultanément de la demande énergétique des bâtiments, les systèmes énergétiques individuels ou de quartier, et du microclimat urbain. L'échelle spatiale correspond aux quartiers urbains explicités géométriquement, et l’échelle temporelle est annuelle. Différentes stratégies de couplage ont été évaluées, pour leur capacité de représentation des effets thermiques, et des phénomènes couplés. Les schémas de couplages synchrones sont efficaces pour les interactions dynamiques entre bâtiments et microclimat. Néanmoins, ce couplage est sensible aux propriétés thermiques du bâtiment. La simplification de la canopée urbaine à un nœud de calcul entraîne une variation significative de la demande énergétique. Par ailleurs, le modèle développé a été utilisé pour évaluer les performances thermiques d'un quartier de La Rochelle. Le remplacement des climatiseurs individuels par un réseau urbain de froid élimine la contribution anthropique des bâtiments, et améliore le confort thermique extérieur, agissant comme une stratégie d'atténuation locale d’îlot de chaleur. Cependant, il entraîne une pénalité énergétique due aux pertes par le sol du réseau urbain. Cette pénalité énergétique est amplifiée lorsqu'une stratégie d'atténuation passive (matériaux froids) est mise en œuvre simultanémentThis PhD work investigates the complex links between urban physical processes, through the development of coupled simulation platforms to account simultaneously for building energy demand, individual or district energy systems, and urban microclimate. The spatial and temporal scales correspond to urban neighborhoods under explicit geometries, and annual simulations respectively. Several coupling strategies have been evaluated, regarding thermal efficiency indicators, and the determination of the diversity of coupled phenomena. The synchronous coupling schemes can effectively assess the dynamical interactions between buildings and the local microclimate. Nevertheless, the coupling variable is sensitive to the thermal properties of the building. The simplification of the urban canopy layer to a single-node description reveals significant variability in building energy demand. Besides, the developed model has been employed to assess the thermal performance of an urban neighborhood in La Rochelle. The transition from local energy systems to the district energy network eliminates anthropogenic heat from buildings, and improves the outdoor thermal comfort conditions, acting as a local heat island mitigation strategy. However, it is associated with an energy penalty due to the ground losses of the piping circuit. This energy penalty is amplified when a passive mitigation strategy (cool materials) is implemented concurrently
7
Munoz, Guevara Jules Ricardo. "Optimization Strategies for the Synthesis / Design of Hihgly Coupled, Highly Dynamic Energy Systems." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/29251.
Анотація:
In this work several decomposition strategies for the synthesis / design optimization of highly coupled, highly dynamic energy systems are formally presented and their implementation illustrated. The methods are based on the autonomous optimization of the individual units (components, sub-systems or disciplines), while maintaining energy and cost links between all units, which make up the overall system. All of the approaches are designed to enhance current engineering synthesis / design practices in that: they support the analysis of systems and optimization in a modular way, the results at every step are feasible and constitute an improvement over the initial design state, the groups in charge of the different unit designs are allowed to work concurrently, and permit any level of complexity as to the modeling and optimization of the units.
All of the decomposition methods use the Optimum Response Surface (ORS) of the problem as a basis for analysis. The ORS is a representation of the optimum objective function for various values of the functions that couple the system units1. The complete ORS or an approximation thereof can be used in ways, which lead to different methods. The first decomposition method called the Local Global Optimization (LGO) method requires the creation of the entire ORS by carrying out multiple unit optimizations for various combinations of values of the coupling functions. The creation of the ORS is followed by a system-level optimization in which the best combination of values for the coupling functions is sought
The second decomposition method is called the Iterative Local Global Optimization (ILGO) scheme. In the ILGO method an initial point on the ORS is found, i.e. the unit optimizations are performed for initial arbitrary values of the coupling functions. A linear approximation of the ORS about that initial point is then used to guide the selection of new values for the coupling functions that guarantee an improvement upon the initial design. The process is repeated until no further improvement is achieved. The mathematical properties of the methods depend on the convexity of the ORS, which in turn is affected by the choice of thermodynamic properties used to charecterize the couplings. Examples in the aircraft industry are used to illustrate the application and properties of the methods.Ph. D.
8
Tomasi, Roberta. "Energy performance, comfort and ventilation effectiveness of radiant systems coupled with mechanical ventilation." Doctoral thesis, Università degli studi di Padova, 2012. http://hdl.handle.net/11577/3422467.
Анотація:
This work presents the results of different numerical and experimental studies about energy performance, thermal comfort and ventilation effectiveness of radiant systems combined with different types of mechanical ventilation. Experimental studies have been carried out in Italy, in a test room in the laboratories of the company RHOSS S.p.A in Codroipo (Udine) and in Denmark, in a test room in the laboratories of the International Centre for Indoor Environment and Energy (ICIEE), at DTU (Danish Technical University), in Lyngby.
Radiant systems in residential and in office buildings are increasingly used because of the low heating or cooling demand and, at the same time, for the good thermal comfort they assure.
The thermal output estimation of radiant system in steady state condition needs the determination of the convective heat transfer coefficient from the surface to the room; a critical review among the correlations available in literature have been carried out and correlations for heated ceiling and cooled floor have been presented. Furthermore the variation of convective heat transfer coefficients, depending on the considered ventilation systems, has been estimated by means of the Computational Fluid Dynamics (CFD) technique.
The energy performance and thermal behavior of radiant systems during transient conditions have been predicted by using experimental tests and numerical calculations with the software Digithon that was developed by the University of Padua. In this work the validation of this software by comparison with experimental data has been presented.
In new and renovated buildings the high tightness and high insulation determine a potential risk of poor indoor air quality and condensation at the surfaces; for this reason an efficient ventilation system is necessary to provide for fresh air in the rooms. In a low polluted building air quality depends on human bioeffluents, among which carbon dioxide is considered the most significant one. By using numerical simulations (CFD) the effects of the supply and extract air terminals on contaminants distribution in offices equipped with a cooled ceiling has been investigated. Besides, in order to fully characterize the indoor climate of residential rooms or offices, an extensive experimental study has been carried out in a test room to determine both thermal comfort and ventilation effectiveness for different solutions of mixing ventilation and displacement ventilation combined with floor radiant systems. In particular, the effects of supply and extract air terminals positions by using low air change rates in mixing ventilation and the effects of different ventilation rates with displacement ventilations terminals have been analyzed. Results from experiments have been used for the validation of a CFD model for the prediction of air distribution in rooms equipped with mixed or displacement ventilation, combined with heating/cooling floor systems.In questo lavoro di dottorato vengono presentati i risultati di uno studio sui sistemi radianti per il raffrescamento ed il riscaldamento in ambito civile e sulla loro integrazione con opportuni sistemi di ventilazione meccanica. Le prestazioni energetiche in regime stazionario e transitorio, così come le prestazioni di comfort termico e di qualità dell’aria garantita, sono state studiate mediante l’ausilio di prove sperimentali, di simulazioni fluidodinamiche e di altri codici di calcolo. Gli studi sperimentali sono stati realizzati in parte in Italia, presso i laboratori dell’azienda RHOSS S.p.A di Codroipo (Udine), e in parte presso i laboratori dell’ICIEE (International Centre for Indoor Environment and Energy), dell’Università Tecnica di Danimarca, (DTU) a Lyngby (DK). L’aspetto più rilevante di questo lavoro è legato alla sempre maggiore diffusione dei sistemi radianti come soluzione per il riscaldamento ed il raffrescamento di ambienti interni, in quanto combinano vantaggi energetici ad elevati livelli di comfort termico. Per ragioni dovute alla piccola differenza di temperatura tra l’ambiente e il fluido termovettore, i sistemi radianti si interfacciano molto bene con caldaie a condensazione, pompe di calore, sistemi free cooling, collettori solari e altre sorgenti rinnovabili e soluzioni ad alta efficienza energetica. Il calcolo della resa termica di tali sistemi viene eseguito mediante le equazioni valide per la convezione in regime stazionario, come quelle fornite dalle norme Europee EN 1264 ed EN 15377. In letteratura esistono numerose correlazioni valide per il calcolo della potenza convettiva di superfici orizzontali e verticali e di superfici interne di stanze reali; le norme EN 1264 ed EN 15377 consigliano correlazioni diverse e lo stesso accade per codici si simulazione energetica degli edifici. Ad oggi non è disponibile una chiara definizione di coefficiente di scambio termico convettivo per i sistemi radianti, specialmente per quanto riguarda pavimenti freddi e soffitti caldi. Il primo obiettivo di questa tesi è stato di realizzare un’analisi critica delle correlazioni disponibili in letteratura adatte ai sistemi radianti e di proporre delle equazioni per ogni configurazione di riscaldamento o raffrescamento da soffitto, pavimento o parete. In ambito residenziale il pavimento radiante rappresenta una delle soluzioni più richieste grazie all’elevato livello di comfort termico garantito; tuttavia, al fine di migliorare la qualità dell’aria e specialmente a causa della necessità di deumidificare l’aria in estate per evitare formazione di condensa, accanto al sistema radiante andrebbe installato un sistema di ventilazione meccanica. L’aria primaria in estate è solitamente a temperatura più bassa della temperatura della stanza e dotata di una certa velocità; nel caso di immissione da bocchette installate vicino ad una superficie radiante, lo scambio convettivo potrebbe venire variato rispetto ad una soluzione senza ventilazione. Mediante uno studio con simulazioni fluidodinamiche CFD è stato possibile valutare l’incremento dello scambio convettivo da un soffitto freddo mediante lo sfruttamento di aria primaria. I sistemi radianti, in particolare i sistemi a soffitto, rappresentano un’ottima soluzione per rimuovere i carichi termici degli uffici durante il periodo estivo, ma allo stesso tempo possono essere usati per il riscaldamento invernale degli stessi con buone prestazioni energetiche e di comfort termico. La differenza sostanziale è che durante la stagione invernale il sistema radiante si trova a lavorare prevalentemente in regime stazionario, mentre durante la stagione estiva i carichi esterni dovuti alla radiazione solare e all’escursione diurna, accompagnati da carichi interni dovuti all’occupazione umana, determinano condizioni piuttosto variabili durante la giornata. Il comportamento di sistemi radianti a regimi stazionari e transitori sono state studiate mediante prove in camera climatica; inoltre un modello di calcolo chiamato Digithon, sviluppato all’interno del Dipartimento di Fisica Tecnica dell’Università di Padova, è stato validato mediante un confronto con dati sperimentali. Seguendo un’opportuna procedura, riportata nella tesi, è stato possibile impostare dei profili di carico che simulano una tipica giornata estiva o invernale su una parete della stanza ed è stato studiato come il soffitto radiante reagisca per cercare di mantenere una certa temperatura di comfort nella stanza. Al fine di mantenere una buona qualità dell’aria, evitare la formazione di condensa, ma anche per incrementare la capacità di raffrescamento quando richiesto, i sistemi radianti per gli uffici andrebbero sempre associati a sistemi di ventilazione meccanica. Accanto ai tradizionali sistemi a soffitto con ventilazione a miscelazione, le soluzioni con ventilazione a dislocamento accoppiate a sistemi a pavimento o a soffitto sono alternative di crescente interesse per gli uffici. In edifici dove sia bassa la quantità di inquinanti emessi dai materiali edili, dai mobili e dalle attrezzature, la quantità di bioeffluenti dagli occupanti, dei quali l’anidride carbonica CO2 è normalmente usata come principale indicatore, è determinante per la qualità dell’aria interna. La capacità di rimozione dei contaminanti e, parallelamente, la capacità di immettere aria pulita negli ambienti sono espresse dall’efficienza di ventilazione (ventilation effectiveness). Mediante simulazione fluidodinamiche CFD è stato possibile confrontare l’efficienza di rimozione dei contaminanti utilizzando diverse soluzioni di ventilazione a dislocamento piuttosto che soluzioni tradizionali a miscelazione. La qualità di un ambiente interno andrebbe misurata in termini sia di comfort termico garantito all’occupante che di qualità dell’aria. Attraverso prove sperimentali in laboratorio, i principali indici di comfort termico e di efficienza di ventilazione sono stati determinati per diverse configurazioni di ventilazione a miscelazione e di ventilazione a dislocamento in ambienti rappresentativi di applicazioni residenziali o del terziario. I risultati sono stati in seguito utilizzati per effettuare una validazione di un modello fluidodinamico (CFD) creato per la previsione del movimento dell’aria in ambienti residenziali o uffici.
9
Hu, Hao. "Optimal and Miniaturized Strongly Coupled Magnetic Resonant Systems." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/3024.
Анотація:
Wireless power transfer (WPT) technologies for communication and recharging devices have recently attracted significant research attention. Conventional WPT systems based either on far-field or near-field coupling cannot provide simultaneously high efficiency and long transfer range. The Strongly Coupled Magnetic Resonance (SCMR) method was introduced recently, and it offers the possibility of transferring power with high efficiency over longer distances. Previous SCMR research has only focused on how to improve its efficiency and range through different methods. However, the study of optimal and miniaturized designs has been limited. In addition, no multiband and broadband SCMR WPT systems have been developed and traditional SCMR systems exhibit narrowband efficiency thereby imposing strict limitations on simultaneous wireless transmission of information and power, which is important for battery-less sensors. Therefore, new SCMR systems that are optimally designed and miniaturized in size will significantly enhance various technologies in many applications.
The optimal and miniaturized SCMR systems are studied here. First, analytical models of the Conformal SCMR (CSCMR) system and thorough analysis and design methodology have been presented. This analysis specifically leads to the identification of the optimal design parameters, and predicts the performance of the designed CSCMR system. Second, optimal multiband and broadband CSCMR systems are designed. Two-band, three-band, and four-band CSCMR systems are designed and validated using simulations and measurements. Novel broadband CSCMR systems are also analyzed, designed, simulated and measured. The proposed broadband CSCMR system achieved more than 7 times larger bandwidth compared to the traditional SCMR system at the same frequency. Miniaturization methods of SCMR systems are also explored. Specifically, methods that use printable CSCMR with large capacitors, novel topologies including meandered, SRRs, and spiral topologies or 3-D structures, lower the operating frequency of SCMR systems, thereby reducing their size. Finally, SCMR systems are discussed and designed for various applications, such as biomedical devices and simultaneous powering of multiple devices.
10
Schroeder, Ryan T. "Gait entrainment in coupled oscillator systems: Clarifying the role of energy optimization in human walking." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2020. https://ro.ecu.edu.au/theses/2281.
Анотація:
Empirical evidence suggests that parameters of human gait (e.g. step frequency, step length) tend to minimize energy expenditure. However, it is unclear if individuals can adapt to dynamic environments in real time, i.e. continuously optimize energy expenditure, and to what extent. Two coupled oscillator systems were used to test the learned interactions of individuals within dynamic environments: (1) experienced farmworkers carrying oscillating loads on a flexible bamboo pole and (2) individuals walking on a treadmill while strapped to a mechatronics oscillator system providing periodic forces to the body. Reductionist trajectory optimization models predicted energy-minimizing gait interactions within the coupled oscillator systems and were compared to experimental data assessed with linear mixed models. On average, pole carriers significantly adjusted step frequency by 3.3% (0.067 Hz, p=0.014) to accommodate the bamboo pole – consistent with model predictions of energy savings. Novice subjects entrained (i.e. synchronized) their step frequency with machine oscillations up to ±10% of preferred step frequency and at amplitudes as low as 5% body weight (or ~33 N). Still, some subjects rarely entrained at all, and many exhibited transient entrainment, i.e. they drifted in and out of step frequencies matching the machine oscillations. Overall, subject entrainment was more robust and consistent with lower frequencies and higher amplitudes (20-30% of body weight). Although no systematic difference was found between the metabolic consumption of subjects during and not during entrainment, the net mechanical work done on subjects by the force oscillations had a strong effect on metabolic output (p
11
Young, Elizabeth R. (Elizabeth Renee) 1980. "Spectroscopic investigation of photo-induced proton-coupled electron transfer and Dexter energy transfer in model systems." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/49750.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2009.Vita.
Includes bibliographical references.
Spectroscopic investigations of systems designed to advance the mechanistic interrogation of photo-induced proton coupled electron transfer (PCET) and proton-coupled (through-bond) energy transfer (PCEnT) are presented. PCET is ubiquitous in Nature, where it is at the heart of bioenergy conversion and catalysis (Chapter I). Systems of relevance to mechanistic studies of PCET and PCEnT are the central tenet of this work. In uni-directional PCET, electron transfer (ET) occurs from an electron donor (De) to an electron acceptor (Ae) through a hydrogen bonded proton interface. The proton interface plays a vital role in mediating ET. Thus, the exact ionization configuration of the interface must be uncovered to fuIIy realize the influence of the interface. SpecificaIIy, does the interface exists in the non-ionized (i.e. amidine-carboxylic acid) or ionized (i.e. amidinium-carboxylate) form. Strategies to spectraIIy monitor the interface ionization state by extending electronic communication from a porphyrinic chromophore to its pendant amidinium functionality are pursued through examination of an alkynylamidinium Ni(II) porphyrin (Chapter II) and an amidinium appended Zn(II) purpurin (Chapter III). With the ionization state of the interface resolved, mechanistic studies of photo-induced PCET between an identical De and Ae pair juxtaposed by a non-ionized (amidine-carboxylic acid) and an ionized (amidinium-sulfonate) interface are undertaken to reveal that PCET occurring through an ionized interface is more strongly coupled to the surrounding solvent environment (Chapter IV). Work on this system is extended to a second solvent of similar dielectric constant to establish that molecular variation of the solvent environment impacts PCET, likely through its interaction with the proton interface (Chapter V). Two water-soluble amidinium-appended ferrocene moieties are presented as building blocks for aqueous bi-directional PCET in which PT occurs to the bulk and ET occurs along a covalently bound coordinate (Chapter VI). ET and through-bond EnT are described by the semiclassical nonradiative decay formalism, meaning both processes should be sensitive to an intervening proton network. For the first time, PCEnT is established using ferrocenyl-amidine moieties bound through an amidinecarboxylic acid interface to Ru(II) polypyridyl complexes (Chapter VII).
Elizabeth R. Young.
Ph.D.
12
Mitchell, Steven J. "The Development of a Steel Fuse Coupling Beam for Hybrid Coupled Wall Systems." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1368026875.
13
Lazaro, Orlando. "CMOS inductively coupled power receiver for wireless microsensors." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51874.
Анотація:
This research investigates how to draw energy from a distant emanating and alternating (i.e., AC) magnetic source and deliver it to a battery (i.e., DC). The objective is to develop, design, simulate, build, test, and evaluate a CMOS charger integrated circuit (IC) that wirelessly charges the battery of a microsystem. A fundamental challenge here is that a tiny receiver coil only produces mV's of AC voltage, which is difficult to convert into DC form. Although LC-boosted diode-bridge rectifiers in the literature today extract energy from similar AC sources, they can do so only when AC voltages are higher than what miniaturized coils can produce, unless tuned off-chip capacitors are available, which counters the aim of integration. Therefore, rather than rectify the AC voltage, this research proposes to rectify the current that the AC voltage induces in the coil. This way, the system can still draw power from voltages that fall below the inherent threshold limit of diode-bridge rectifiers. Still, output power is low because, with these low currents, small coils can only extract a diminutive fraction of the magnetic energy available, which is why investing battery energy is also part of this research. Ultimately, the significance of increasing the power that miniaturized platforms can output is higher integration and functionality of micro-devices, like wireless microsensors and biomedical implants.
14
Reimuth, Andrea [Verfasser], and Wolfram [Akademischer Betreuer] Mauser. "The role of residential photovoltaic-coupled battery storages in the energy system from a regional perspective : a spatiotemporal assessment of residential photovoltaic and battery storage systems and their effects on the energy flows / Andrea Reimuth ; Betreuer: Wolfram Mauser." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1223849937/34.
15
Parada, Giovanny A. "Synthesis of Biomimetic Systems for Proton and Electron Transfer Reactions in the Ground and Excited State." Doctoral thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-251471.
Анотація:
A detailed understanding of natural photosynthesis provides inspiration for the development of sustainable and renewable energy sources, i.e. a technology that is capable of converting solar energy directly into chemical fuels. This concept is called artificial photosynthesis. The work described in this thesis contains contributions to the development of artificial photosynthesis in two separate areas. The first one relates to light harvesting with a focus on the question of how electronic properties of photosensitizers can be tuned to allow for efficient photo-induced electron transfer processes. The study is based on a series of bis(tridentate)ruthenium(II) polypyridyl complexes, the geometric properties of which make them highly appealing for the construction of linear donor-photosensitizer-acceptor arrangements for efficient vectorial photo-induced electron transfer reactions. The chromophores possess remarkably long lived 3MLCT excited states and it is shown that their excited-state oxidation strength can be altered by variations of the ligand scaffold over a remarkably large range of 900 mV. The second area of relevance to natural and artificial photosynthesis that is discussed in this thesis relates to the coupled movement of protons and electrons. The delicate interplay between these two charged particles regulates thermodynamic and kinetic aspects in many key elementary steps of natural photosynthesis, and further studies are needed to fully understand this concept. The studies are based on redox active phenols with intramolecular hydrogen bonds to quinolines. The compounds thus bear a strong resemblance to the tyrosine/histidine couple in photosystem II, i.e. the water-plastoquinone oxidoreductase enzyme in photosynthesis. The design of the biomimetic models is such that the distance between the proton donor and acceptor is varied, enabling studies on the effect the proton transfer distance has on the rate of proton-coupled electron transfer reactions. The results of the studies have implications for the development of artificial photosynthesis, in particular in connection with redox leveling, charge accumulation, as well as electron and proton transfer. In addition to these two contributions, the excited-state dynamics of the intramolecular hydrogen-bonded phenols was investigated, thereby revealing design principles for technological applications based on excited-state intramolecular proton transfer and photoinduced tautomerization.
16
Mallégol, Antoine. "Optimisation multi-objectifs de systèmes énergétiques couplés : méthodes exactes et approchées." Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2023. http://www.theses.fr/2023IMTA0383.
Анотація:
Un système d'énergie est un ensemble d'infrastructures et de technologies permettant la production, le stockage et la distribution d'énergie. Les systèmes énergétiques couplés incluent plusieurs vecteurs énergétiques, par exemple de l'électricité et de la chaleur, et des interactions peuvent avoir lieu entre ces formes d'énergie. L'optimisation des systèmes énergétiques permet de dimensionner et piloter au mieux la génération et le stockage d'énergie, avec divers objectifs qui peuvent être liés au coût ou à l'impact environnemental du système. Dans ce travail nous modélisons et optimisons un système énergétique couplé sur une période de temps longue (une année), avec une résolution temporelle élevée. En parallèle, nous tenons compte de non linéarités dans les équations qui régissent le rendement électrique de la cogénération et celles décrivant le stockage thermique. Nous proposons de manière incrémentale différentes méthodes de résolution, allant d'un programme mathématique à une matheuristique, en passant par une heuristique. Nous montrons l'intérêt de ces approches pour réduire les coûts de ces systèmes, tout en augmentant la proportion de sources d’énergies renouvelablesAn energy system is a set of infrastructures and technologies that allow for the production, storage, and distribution of energy. Coupled energy systems include multiple energy vectors, such as electricity and heat, and interactions can occur between these forms of energy. Optimization of these systems allows for the best possible design and operation of energy generation and storage, with various objectives that can be linked to cost or the environmental impact of the system. In this work, we model and optimize a coupled energy system over a long period of time (one year), with a high temporal resolution. In parallel, we take into account non linearities in the equations that govern the electrical efficiency of cogeneration and those describing thermal storage. We incrementally propose different resolution methods, ranging from a mathematical program to a matheuristic, through an heuristic. We show the interest of these approaches for reducing the costs of these systems, while increasing the proportion of renewable energy sources
17
Piechowski, Miroslaw. "A ground coupled heat pump system with energy storage /." Connect to thesis, 1996. http://eprints.unimelb.edu.au/archive/00000724.
18
Stelzer, Rainer. "Une méthode énergétique pour les systèmes vibro-acoustiques couplés." Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00780602.
Анотація:
Ce mémoire de thèse présente le développement de la méthode "statistical modal energy distribution analysis (SmEdA)" pour des systèmes vibro-acoustiques couplés. Cette méthode de calcul est basée sur le bilan énergétique dans des sous-systèmes fermés couplés, comme une structure ou une cavité. L'interaction entre de tels systèmes est décrite par des couplages entre les modes. La version initiale de SmEdA prend en compte seulement les modes qui ont une fréquence propre dans le bande d'excitation. Le travail présenté ici étudie l'effet des modes non résonants sur la réponse et identifie les cas dans lesquels un tel effet devient important. L'introduction des modes non résonants permet d'utiliser la méthode SmEdA dans des cas d'applications plus larges. En outre, une nouvelle méthode de post-traitement a été développée pour calculer des distributions d'énergie dans les sous-systèmes. Finalement, une nouvelle méthode d'approximation pour la prise en compte des modes de systèmes de grandes dimensions ou mal définis a été formulée. Toutes ces méthodes ont été comparées avec d'autres méthodes de calcul via des exemples académiques et industriels. Ainsi, la nouvelle version de SmEdA incluant le post-traitement pour obtenir des distributions d'énergie a été validé et les avantages et possibilités d'applications sont montrés.
19
Ransley, Edward Jack. "Survivability of wave energy converter and mooring coupled system using CFD." Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/3503.
Анотація:
This thesis discusses the development of a Numerical Wave Tank (NWT) capable of describing the coupled behaviour of Wave Energy Converters (WECs) and their moorings under extreme wave loading. The NWT utilises the open-source Computational Fluid Dynamics (CFD) software OpenFOAM(R) to solve the fully nonlinear, incompressible, Reynolds-Averaged Navier-Stokes (RANS) equations for air and water using the Finite Volume Method (FVM) and a Volume of Fluid (VOF) treatment of the interface. A method for numerically generating extreme waves is devised, based on the dispersively-focused NewWave theory and using the additional toolbox waves2Foam. A parametric study of the required mesh resolution shows that steeper waves require finer grids for mesh independence. Surface elevation results for wave-only cases closely match those from experiments, although an improved definition of the flow properties is required to generate very steep focused waves. Predictions of extreme wave run-up and pressure on the front of a fixed truncated cylinder compare well with physical measurements; the numerical solution successfully predicts the secondary loading cycle associated with the nonlinear ringing effect and shows a nonlinear relationship between incident crest height and horizontal load. With near perfect agreement during an extreme wave event, the reproduction of the six degree of freedom (6DOF) motion and load in the linearly-elastic mooring of a hemispherical-bottomed buoy significantly improves on similar studies from the literature. Uniquely, this study compares simulations of two existing WEC designs with scale-model tank tests. For the Wavestar machine, a point-absorber constrained to pitch motion only, results show good agreement with physical measurements of pressure, force and float motion in regular waves, although the solution in the wake region requires improvement. Adding bespoke functionality, a point-absorber designed by Seabased AB, consisting of a moored float and Power Take-Off (PTO) with limited stroke length, translator and endstop, is modelled in large regular waves. This represents a level of complexity not previously attempted in CFD and the 6DOF float motion and load in the mooring compare well with experiments. In conclusion, the computational tool developed here is capable of reliably predicting the behaviour of WEC systems during extreme wave events and, with some additional parameterisation, could be used to assess the survivability of WEC systems at full-scale before going to the expense of deployment at sea.
20
ERDMAN, Paolo Andrea. "Quantum Thermal Machines." Doctoral thesis, Scuola Normale Superiore, 2020. http://hdl.handle.net/11384/95512.
21
Alghamdi, Jamal Khaled. "CFD Simulation Methodology for Ground-Coupled Ventilation System." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/35736.
Анотація:
In the past two decades, a growing interest in alternative energy resources as a
replacement to the non-renewable resources used now days. These alternatives include
geothermal energy which can be used to generate power and reduce the demands on
energy used to heat and cool buildings. Ground-coupled ventilation system is one of the
many applications of the geothermal energy that have a lot of attention in the early 80â s
and 90â s but all designs of the system where based on single case situations. On the other
hand, computational fluid dynamics tools are used to simulate heat and fluid flow in any
real life situation. They start to develop rapidly with the fast development of computers
and processors. These tools provide a great opportunity to simulate and predict the
outcome of most problems with minimum loss and better way to develop new designs.
By using these CFD tools in GCV systems designing procedure, energy can be conserved
and designs going to be improved.
The main objective of this study is to find and develop a CFD modeling strategy
for GCV systems. To accomplish this objective, a case study must be selected, a proper
CFD tool chosen, modeling and meshing method determined, and finally running
simulations and analyzing results. All factors that affect the performance of GCV should
be taken under consideration in that process such as soil, backfill, and pipes thermal
properties. Multiple methods of simulation were proposed and compared to determine the
best modeling approach.Master of Science
22
Alfadil, Mohammad Omar. "Design Tool for a Ground-Coupled Ventilation System." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/100604.
Анотація:
Ground-coupled ventilation (GCV) is a system that exchanges heat with the soil. Because ground temperatures are relatively higher during the cold season and lower during the hot season, the system takes advantage of this natural phenomenon. This research focused on designing a ground-coupled ventilation system evaluation tool of many factors that affect system performance. The tool predicts the performance of GCV system design based on the GCV system design parameters including the location of the system, pipe length, pipe depth, pipe diameter, soil type, number of pipes, volume flow rate, and bypass system. The tool uses regression equations created from many GCV system design simulation data using Autodesk Computational Fluid Dynamics software. As a result, this tool helps users choose the most suitable GCV system design by comparing multiple GCV systems' design performances and allows them to save time, money, and effort.Doctor of Philosophy
23
McDaniel, Matthew Lee. "Proposed Design for a Coupled Ground-Source Heat Pump/Energy Recovery Ventilator System to Reduce Building Energy Demand." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/33610.
Анотація:
The work presented in this thesis focuses on reducing the energy demand of a residential building by using a coupled ground-source heat pump/energy recovery ventilation (GSHP-ERV) system to present a novel approach to space condition and domestic hot water supply for a residence. The proposed system is capable of providing hot water on-demand with a high coefficient of performance (COP), thus eliminating the need for a hot water storage tank and circulation system while requiring little power consumption. The necessary size of the proposed system and the maximum and normal heating and cooling loads for the home were calculated based on the assumptions of an energy efficient home, the assumed construction specifications, and the climate characteristics of the Blacksburg, Virginia region. The results from the load analysis were used to predict energy consumption and costs associated with annual operations.The results for the predicted heating annual energy consumption and costs for the GSHP-ERV system were compared to an air-source heat pump and a natural gas furnace. On average, it was determined that the proposed system was capable of reducing annual energy consumption by 56-78% over air-source heat pumps and 85-88% over a natural gas furnace. The proposed GSHP-ERV system reduced costs by 45-61% over air-source heat pump systems and 52-58% over natural gas furnaces. The annual energy consumption and costs associated with cooling were not calculated as cooling accounts for a negligible portion (6%) of the total annual energy demand for a home in Blacksburg.Master of Science
24
Melo, Júnior José Carlos de Albuquerque. "On linearly coupled systems of Schrödinger equations with critical growth." Universidade Federal da Paraíba, 2017. http://tede.biblioteca.ufpb.br:8080/handle/tede/9316.
Анотація:
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
In thisworkwestudytheexistenceofgroundstatesforthefollowingclassofcoupled systems involvingnonlinearSchrödingerequations 8<: u + V1(x)u = f1(x; u) + (x)v;x 2 RN; v + V2(x)v = f2(x; v) + (x)u; x 2 RN; where thepotentials V1 : RN ! R, V2 : RN ! R are nonnegativeandrelatedwith the couplingterm : RN ! R by j (x)j < pV1(x)V2(x), forsome 0 < < 1. In the case N = 2, thenonlinearities f1 e f2 havecriticalexponentialgrowthinthesense of Trudinger-Moserinequality.Inthecase N 3, thenonlinearitiesarepolynomials with subcriticalandcriticalexponentintheSobolevsense.Westudyalsothefollowing class ofnonlocalcoupledsystems 8<: ( )1=2u + V1(x)u = f1(u) + (x)v;x 2 R; ( )1=2v + V2(x)v = f2(v) + (x)u; x 2 R; where ( )1=2 denotes thesquarerootoftheLaplacianoperatorandthenonlinearities havecriticalexponentialgrowth.Ourapproachisvariationalandbasedon minimization techniqueovertheNeharimanifold
Neste trabalhoestudamosaexistênciadegroundstatesparaaseguinteclassede sistemas acopladosenvolvendoequaçõesdeSchrödingernão-lineares 8<: u + V1(x)u = f1(x; u) + (x)v;x 2 RN; v + V2(x)v = f2(x; v) + (x)u; x 2 RN; onde ospotenciais V1 : RN ! R, V2 : RN ! R são não-negativoseestãorelacionados com otermodeacomplamento : RN ! R por j (x)j < pV1(x)V2(x), paraalgum 0 < < 1. Nocaso N = 2, asnão-linearidades f1 e f2 possuemcrescimentocrítico exponencialnosentidodadesigualdadedeTrudinger-Moser.Nocaso N 3, asnão- linearidades sãopolinômioscomexpoentesubcríticoecríticonosentidodeSobolev. Estudamos aindaaseguinteclassedesistemasacopladosnão-locais 8<: ( )1=2u + V1(x)u = f1(u) + (x)v;x 2 R; ( )1=2v + V2(x)v = f2(v) + (x)u; x 2 R; onde ( )1=2 denota ooperadorraízquadradadolaplacianoeasnão-linearidades possuemcrescimentocríticoexponencial.Nossaabordagemévariacionalebaseadana técnica deminimizaçãosobreavariedadedeNehari.
25
Chen, Hao. "Modeling and control of a marine current energy conversion system using a doubly salient permanent magnet generator." Nantes, 2014. http://archive.bu.univ-nantes.fr/pollux/show.action?id=83aa318a-2539-4dda-aa76-c57351bf6c09.
Анотація:
Parmi les énergies marines renouvelables hors éolien posé, toutes naissantes, l’énergie des courants marins (énergie hydrolienne) est susceptible de déboucher sur une exploitation commerciale et industrielle à moyen terme. C’est une énergie intermittente, mais très prévisible, ce qui facilite son intégration au réseau. Les travaux réalisés dans cette thèse rentrent dans ce contexte et ont pour objectif la modélisation et la commande d’une chaîne de conversion d’énergie hydrolienne. Cela nécessite une modélisation multiphysique allant de la ressource jusqu’à l’intégration au réseau électrique, la conception et la commande d’une génératrice innovante à attaque directe et des interfaces d’électronique de puissance associés. Les concepts de turbines hydroliennes, les projets existants ou en cours ainsi que les structures usuelles de chaînes de conversion sont présentés. Les modèles de la ressource et de la turbine sont dressés. Un modèle dynamique d’une génératrice synchrone à aimants permanents doublement saillante basé sur la méthode des éléments finis et la transformation de Park est ensuite développé. Les résultats obtenus sont comparés à ceux d'une génératrice synchrone à aimants permanents classique montrant ainsi l’originalité, la complexité et les principales caractéristiques de la structure proposée. L’impact de la mutuelle inductance entre les phases statoriques sur les performances de la machine est détaillé. Des formes particulières de courants d’alimentation sont recherchés et testés par simulation en vue de délivrer un couple quasi constant et de minimiser les pertes Joule. Différentes stratégies de contrôle sont ensuite élaborées et appliquées à l’ensemble génératrice – convertisseurs bidirectionnels à MLI. Les résultats obtenus en mode de fonctionnement MPPT ou défluxé à l’aide de l’outil de simulation développé sont présentés et discutés pour des cas tests réalistes réalisés sous l’environnement Matlab/SimulinkSeveral techniques to extract and exploit ocean energy have been recently suggested. The most studied ones are: marine current energy, wave energy and ocean ̐thermal energy. This Ph. D. Thesis fits in this context and its main objective is to contribute on control and modelling of a Marine Current Energy Conversion System (MCECS). This requires multi-physics modelling from the hydrokinetic resource to the electricity grid, design and control of an innovative low speed non-conventional generator and its associated power electronic interfaces. At first, turbine concepts, relative projects and usual chain of tidal energy conversion are presented. Tidal current and turbine modelling are secondly addressed. The dynamic modelling of a low speed Double Salient Permanent Magnet Generator (DSPMG) based on finite element method and Park transformations is developed. Results are compared to classical Permanent Magnet Synchronous Generator (PMSG) to highlight advantages, originality, complexity and principal characteristics of the proposed structure. Suitable currents are then determined and tested by simulation in order to deliver a quasi-constant torque and minimise Joule losses. The mutual effect on the generator performances is detailed. Finally, several control strategies are applied to DSPMG associated to a bidirectional back-to-back converter and are analysed. The main results, based on the developed marine current turbine simulation tool, are presented and discussed with illustration by several realistic studies and Matlab/Simulink assessment
26
Hassan, Najeeb ul, Ali E. Pusane, Michael Lentmaier, Gerhard P. Fettweis, and Daniel J. Costello. "Reduced Complexity Window Decoding Schedules for Coupled LDPC Codes." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-105936.
Анотація:
Window decoding schedules are very attractive for message passing decoding of spatially coupled LDPC codes. They take advantage of the inherent convolutional code structure and allow continuous transmission with low decoding latency and complexity. In this paper we show that the decoding complexity can be further reduced if suitable message passing schedules are applied within the decoding window. An improvement based schedule is presented that easily adapts to different ensemble structures, window sizes, and channel parameters. Its combination with a serial (on-demand) schedule is also considered. Results from a computer search based schedule are shown for comparison.
27
Hassan, Najeeb ul, Ali E. Pusane, Michael Lentmaier, Gerhard P. Fettweis, and Daniel J. Costello. "Reduced Complexity Window Decoding Schedules for Coupled LDPC Codes." Technische Universität Dresden, 2012. https://tud.qucosa.de/id/qucosa%3A26634.
Анотація:
Window decoding schedules are very attractive for message passing decoding of spatially coupled LDPC codes. They take advantage of the inherent convolutional code structure and allow continuous transmission with low decoding latency and complexity. In this paper we show that the decoding complexity can be further reduced if suitable message passing schedules are applied within the decoding window. An improvement based schedule is presented that easily adapts to different ensemble structures, window sizes, and channel parameters. Its combination with a serial (on-demand) schedule is also considered. Results from a computer search based schedule are shown for comparison.
28
Mohd, Thiyahuddin Mohd Izzat. "Experimental and numerical characteristics of portable water-filled road safety barrier system under different impact conditions." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/71458/1/Mohd%20Izzat_Mohd%20Thiyahuddin_Thesis.pdf.
Анотація:
This research has developed an innovative road safety barrier system that will enhance roadside safety. In doing so, the research developed new knowledge in the field of road crash mitigation for high speed vehicle impact involving plastic road safety barriers. This road safety barrier system has the required feature to redirecting an errant vehicle with limited lateral displacement. Research was carried out using dynamic computer simulation technique support by experimental testing. Future road safety barrier designers may use the information in this research as a design guideline to improve the performance and redirectional capability of the road safety barrier system. This will lead to better safety conditions on the roadways and potentially save lives.
29
Smilek, Jan. "Energy Harvesting Power Supply for MEMS Applications." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-386765.
Анотація:
Tato práce se zabývá vývojem nezávislého elektrického zdroje pro moderní nízkopříkonové elektrické aplikace. Protože tradiční řešení napájení drobných spotřebičů s využitím baterií či akumulátorů snižuje uživatelský komfort kvůli potřebě pravidelné údržby, navrhovaný zdroj využívá principu energy harvesting. Tento princip spočívá v získávání energie přímo z okolního prostředí napájené aplikace a její přeměně na energii elektrickou, která je dále využita pro na-pájení moderních MEMS (mikroelektromechanických) zařízení. Potenciální aplikací vyvíjeného zdroje je především moderní nositelná elektronika a biomedicínské senzory. Tato oblast využití ovšem klade zvýšené nároky na parametry generátoru, který musí zajistit dostatečný generovaný výkon z energie, dostupné v okolí lidského těla, a to při zachování prakticky využitelné velikosti a hmotnosti. Po stanovení předběžných požadavků a provedení analýz vhodnosti dostupných zdrojů energie ke konverzi byla k využití vybrána kinetická energie lidských aktivit. Byla provedena série měření zrychlení na lidském těle, především v místě předpokládaného umístění generátoru, aby bylo možno analyzovat a generalizovat hodnoty energie dostupné ke konverzi v daném umístění. V návaznosti na tato měření a analýzy byl vyvinut inovativní kinetický energy harvester, který byl následně vyroben jako funkční vzorek. Tento vzorek byl pak testován v reálných podmínkách pro verifikaci simulačního modelu a vyhodnocení reálné použitelnosti takového zařízení. Kromě samotného vývoje generátoru je v práci popsán i originální způsob zvýšení generovaného výkonu pro kinetické energy harvestery a jsou prezentována statistická data a modely pro predikci využitelnosti kinetických harvesterů pro získávání energie z lidské aktivity.
30
Ayele, Getnet Tadesse. "Exploiting the synergies from coupled electricity and heat distribution networks : modelling, simulation and optimization based on an extended energy hub approach." Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2020. http://www.theses.fr/2020IMTA0215.
Анотація:
La littérature récente montre qu'il existe un potentiel important de décarbonation et d'amélioration de l'efficacité des réseaux d’énergie, qui peut être exploité grâce à la synergie offerte par les systèmes multi-énergies (MES). Les technologies de couplages, telles que les centrales de cogénération, les pompes à chaleur et les stockages thermiques, sont largement recommandées pour une flexibilité accrue et un meilleur taux de pénétration des énergies renouvelables dans les secteurs du chauffage et de l'électricité. Sur la base de ce constat, la taille et le nombre de technologies de couplage dans les réseaux de distribution de chaleur, telles que les centrales de production combinée de chaleur et d'électricité (cogénération) et les pompes à chaleur (PAC), augmentent. Ces technologies étant exclusivement gérées par les gestionnaires de réseaux de chauffage urbain, leur fonctionnement devient parfois sous-optimal du point de vue du réseau électrique et elles peuvent entraîner une surcharge des réseaux de distribution d'électricité basse tension (en particulier pour les grandes puissances installées). Des modèles de simulation et d'optimisation intégrés sont nécessaires pour exploiter efficacement les synergies sans compromettre les réseaux de distribution composants les MES. Ces modèles ne sont pas encore développés. Les outils classiques de simulation mono-vecteur d’énergie ne sont pas capables d’intégrer les paramètres de fonctionnement couplé clés des réseaux de distribution multi vecteurs. Une nouvelle méthodologie de simulation et d'optimisation de MES est développée dans cette thèse, basée sur une approche d'Extended Energy Hub (EEH). Une structure générale de modélisation est d'abord proposée sous forme modulaire, afin de pouvoir être facilement adaptée à tout type de réseaux énergétiques multi vecteurs. Celle-ci est ensuite utilisée pour développer les détails d'un modèle intégré de flux de charges régissant les réseaux couplés de chauffage et de distribution d'électricité. Plusieurs études de cas, traitant de topologies de réseaux radiales et maillées, sont considérées pour la démonstration et la validation numérique du modèle proposé. Ce modèle de flux de charges est en outre combiné avec un algorithme d'optimisation (PSO) afin de mener des études de flux de puissances intégrées optimaux. Le potentiel offert par cette démarche est illustré par l'étude du placement optimal des technologies de couplage, comme les pompes à chaleur (PAC), dans les réseaux couplés de chauffage et de distribution d'électricité. La capacité de l'outil développé est de plus illustrée par l'exploitation des synergies des réseaux couplés en présence d'énergies renouvelables intermittentes et d'un signal de prix de l'électricité variable. Il est démontré que les méthodologies de simulation et d'optimisation basées sur l'EEH, proposées dans cette thèse sont très efficaces, flexibles et facilement évolutives pour intégrer les paramètres de fonctionnement clés des réseaux intégrés d'électricité et de chauffage urbain. Les modèles développés peuvent ainsi être utilisés comme plate-forme d’études de l'intégration des réseaux intelligents et des réseaux thermiques intelligentsRecent literature shows that there is a significant potential of decarbonisation and efficiency improvement that can be achieved through the synergy from multi-energy systems (MESs). Coupling technologies, such as co-generation plants, heat pumps and thermal storages are widely recommended as means of unlocking additional flexibility and increasing the penetration of renewables in the heating and electricity sectors. In view of that, the size and number of coupling technologies, such as combined heat and power plants and heat pumps (HPs), being installed in the heat distribution networks are increasing. As these technologies are exclusively managed by the district heating network operators, their operation sometimes becomes suboptimal from the electricity network point of view, and they (in particular large HPs) may cause overloading of the low voltage electricity distribution networks. Integrated simulation and optimisation models are required to exploit the synergies effectively without compromising the constituent distribution networks of MES. Such models are not yet well developed. The conventional single-energy-carrier simulation tools are not capable of capturing key operating parameters of the multi-carrier distribution networks either. A novel methodology for simulation and optimisation of MES is developed in this thesis based on an Extended Energy Hub (EEH) approach. The general framework is first developed in modular form so that it can be easily adapted for any type of multi-carrier energy networks. The framework is then used to develop the details of an integrated load flow model governing coupled heating and electricity distribution networks. Various load flow case studies with radial and meshed topologies are considered for demonstration and numerical validation of the proposed model. The load flow model is further combined with a particle swarm optimisation algorithm in order to conduct integrated optimal power flow studies. Its contribution to the state of art is demonstrated by studying the optimal placement of coupling technologies, such as HPs and boilers in coupled heating and electricity distribution networks. The capacity of the model is further illustrated by exploiting the synergies using HPs together with thermal storage in the presence of intermittent renewables and variable electricity price signal. It is shown that the EEH-based simulation and optimisation methodologies proposed in this thesis are very effective, flexible and easily scalable in capturing the key operating parameters of integrated electricity and district heating networks. The models can be used as a platform for further studies on integration of smart grids and smart thermal networks
31
Kaplan, Marcus [Verfasser]. "Agent-based modeling of land-use changes and vulnerability assessment in a coupled socio-ecological system in the coastal zone of Sri Lanka / Marcus Kaplan." Bonn : Universitäts- und Landesbibliothek Bonn, 2011. http://d-nb.info/1016145586/34.
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Hamidouche, Ziad. "Modeling and numerical simulation of coupled reactive fluidized beds in a Chemical Looping Combustion system." Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/17921/1/hamidouche.pdf.
Анотація:
In this work, reactive unsteady three-dimensional numerical simulations of a Chemical Looping Combustion (CLC) plant are performed. The plant is a 120 kWth pilot working with Ca-Mn-based material as selected oxygen carrier. Numerical simulations are performed by NEPTUNE_CFD code using an Euler-Euler approach which computes both the gas and the solid phases in an Eulerian fashion accounting for specific closures in order to model interphase mass, momentum and energy transfers. Reduction and oxidation heterogeneous (i.e. gas-solid) reactions are modeled by means of a grain model (shrinking core model in the grain) accounting for both the competing mechanisms of chemical reaction at the particle internal surface and gaseous diffusion through the product layer. Results from numerical simulations are validated against experimental measurements and analyzed in order to gain insight in the local behaviour of the reactive gas-particle flow in the CLC system. The theoretical/numerical tool developed in this work will be used for design upgrade recommendation in the stage of scaling-up from pilot to industrial facilities.
33
Marion, Candice. "Novel insights on ghrelin receptor signaling in energy homeostasis and feeding behavior using the GhsrQ343X mutant rat model." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCB109.
Анотація:
La ghréline acylée, une hormone produite par l’estomac, favorise la prise de poids corporel, majoritairement sous forme de masse grasse, par le biais de divers mécanismes centraux et périphériques via le récepteur sécrétagogue de l’hormone de croissance (GHSR). Le GHSR est un récepteur couplé aux protéines G qui, en plus de répondre à la ghréline acylée, possède une signalisation indépendante de la ghréline par le biais de son activité constitutive ou par une modulation de réponses dopaminergiques via oligomérisation du GHSR avec des récepteurs dopaminergiques. Malgré les puissantes réponses pharmacologiques à la ghréline acylée, des modèles animaux capables d’appréhender la complexité du système ghréline acylée-GHSR in vivo manquent, ce qui a considérablement ralenti l’élucidation des rôles physiologiques de cette hormone et de son récepteur. En effet, les modèles génétiques murins générés jusqu’à présent manquent de spécificité au niveau de l’hormone (incapacité à discriminer la ghréline acylée de la ghréline désacylée), et/ou au niveau du GHSR (incapacité à discriminer les différents modes de signalisation du GHSR). Dans ce contexte, de nouveaux modèles qui impacteraient de façon différentielle les voies de signalisation du GHSR seraient des outils pertinents pour contribuer au déchiffrage du système ghréline acylée-GHSR in vivo. Nous nous sommes ainsi attachés à caractériser un modèle de rats porteur d’une mutation ponctuelle dans le Ghsr qui prédit la délétion d’un domaine régulateur dans l’extrémité C-terminale du GHSR (GhsrQ343X). Dans des modèles cellulaires, nous avons montré que cette mutation découple le GHSR des processus d’internalisation du récepteur et de recrutement de la β-arrestine induits par la ghréline acylée, tout en augmentant la réponse aux agonistes du GHSR dans la voie des protéines G. Conformément à ce mécanisme, les rats mutants homozygotes GhsrM/M ont une réponse accrue à l’administration d’agonistes du GHSR sur le plan de la libération d’hormone de croissance, de la prise alimentaire ou de l’activité locomotrice. L’exploration physiologique et comportementale des rats GhsrM/M indique que la mutation GhsrQ343X est associée à une augmentation du poids et de l’adiposité indépendamment de la prise alimentaire, une diminution de l’oxydation globale des acides gras, de la flexibilité métabolique et de la tolérance au glucose, sans impact critique sur la prise alimentaire homéostatique. En outre, étant donné que la mutation GhsrQ343X n’augmente pas les niveaux circulants de ghréline, le phénotype métabolique général des rats GhsrM/M est en accord avec une sensibilité augmentée du GHSR en réponse au tonus endogène de ghréline acylée. Enfin, des résultats préliminaires suggèrent que la mutation GhsrQ343X pourrait être associée à des altérations relatives aux fonctions de récompense et de mémoire dont les mécanismes sous-jacents restent à décrypter. En résumé, nous proposons le modèle de rat mutant GhsrQ343X comme un nouvel outil, plus spécifique que les modèles murins d’invalidation génétique, pour explorer in vivo la signalisation du GHSR dans diverses fonctions biologiques, et à plus long terme aider au design de composés pharmacologiques ciblant le GHSR efficaces dans un cadre cliniqueThe stomach-derived hormone acyl ghrelin promotes body weight gain, mostly in the form of fat mass, by means of several central and peripheral mechanisms mediated by the growth hormone secretagogue receptor (GHSR). The GHSR is a G protein-coupled receptor that, in addition to respond to acyl ghrelin, displays agonist-independent signaling through high constitutive activity and possibly heteromerization with dopamine receptors. Despite the potent biological properties of exogenous acyl ghrelin, the lack of animal models able to apprehend the complexity of the acyl ghrelin-GHSR system in vivo has been hampering the elucidation of its physiological roles. Indeed, genetic mouse models generated so far lack specificity either at the level of the hormone (not able to discriminate between acyl ghrelin versus desacyl ghrelin) and/or at the level of the GHSR (not able to discriminate between GHSR signaling modes). In this context, new models differentially affecting GHSR signaling pathways would represent valuable tools to decipher the acyl ghrelin-GHSR system in vivo. We therefore aimed at characterizing a new rat model carrying a point mutation in Ghsr that predicts truncation of a regulatory domain in the C-terminus, the GhsrQ343X mutation. In cellular models, this mutation was found to uncouple the GHSR from agonist-dependent receptor internalization and β-arrestin recruitment, while enhancing GHSR responsiveness in the G protein pathway. Accordingly, homozygous mutant GhsrM/M rats show enhanced responsiveness to exogenous GHSR agonists in terms of growth hormone release, food intake and locomotor activity. Physiological and behavioral exploration of GhsrM/M rats supports that the GhsrQ343X mutation is associated with increased body weight gain and adiposity independently of calorie intake, reduced whole-body fat oxidation, metabolic flexibility and glucose tolerance, without any critical impact on homeostatic feeding behavior. Moreover, given that circulating ghrelin levels are not increased by the GhsrQ343X mutation, the overall metabolic phenotype of GhsrM/M rats is consistent with enhanced GHSR sensitivity to the endogenous tone of acyl ghrelin. Furthermore, preliminary results suggest that the GhsrQ343X mutation could be associated with behavioral alterations related to reward and memory functions, through mechanisms that remain to be elucidated. Altogether, we propose the GhsrQ343X mutant rat model as a novel tool, more specific than knockout mouse models in its mechanism-of-action, to explore GHSR signaling across biological functions in vivo, and ultimately help in the design of efficient GHSR-targeting drugs
34
Raymond, Alexander William. "Investigation of microparticle to system level phenomena in thermally activated adsorption heat pumps." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34682.
Анотація:
Heat actuated adsorption heat pumps offer the opportunity to improve overall energy efficiency in waste heat applications by eliminating shaft work requirements accompanying vapor compression cycles. The coefficient of performance (COP) in adsorption heat pumps is generally low. The objective of this thesis is to model the adsorption system to gain critical insight into how its performance can be improved. Because adsorption heat pumps are intermittent devices, which induce cooling by adsorbing refrigerant in a sorption bed heat/mass exchanger, transient models must be used to predict performance. In this thesis, such models are developed at the adsorbent particle level, heat/mass exchanger component level and system level.
Adsorption heat pump modeling is a coupled heat and mass transfer problem. Intra-particle mass transfer resistance and sorption bed heat transfer resistance are shown to be significant, but for very fine particle sizes, inter-particle resistance may also be important. The diameter of the adsorbent particle in a packed bed is optimized to balance inter- and intra-particle resistances and improve sorption rate. In the literature, the linear driving force (LDF) approximation for intra-particle mass transfer is commonly used in place of the Fickian diffusion equation to reduce computation time; however, it is shown that the error in uptake prediction associated with the LDF depends on the working pair, half-cycle time, adsorbent particle radius, and operating temperatures at hand.
Different methods for enhancing sorption bed heat/mass transfer have been proposed in the literature including the use of binders, adsorbent compacting, and complex extended surface geometries. To maintain high reliability, the simple, robust annular-finned-tube geometry with packed adsorbent is specified in this work. The effects of tube diameter, fin pitch and fin height on thermal conductance, metal/adsorbent mass ratio and COP are studied. As one might expect, many closely spaced fins, or high fin density, yields high thermal conductance; however, it is found that the increased inert metal mass associated with the high fin density diminishes COP. It is also found that thin adsorbent layers with low effective conduction resistance lead to high thermal conductance. As adsorbent layer thickness decreases, the relative importance of tube-side convective resistance rises, so mini-channel sized tubes are used. After selecting the proper tube geometry, an overall thermal conductance is calculated for use in a lumped-parameter sorption bed simulation. To evaluate the accuracy of the lumped-parameter approach, a distributed parameter sorption bed simulation is developed for comparison. Using the finite difference method, the distributed parameter model is used to track temperature and refrigerant distributions in the finned tube and adsorbent layer. The distributed-parameter tube model is shown to be in agreement with the lumped-parameter model, thus independently verifying the overall UA calculation and the lumped-parameter sorption bed model.
After evaluating the accuracy of the lumped-parameter model, it is used to develop a system-level heat pump simulation. This simulation is used to investigate a non-recuperative two-bed heat pump containing activated carbon fiber-ethanol and silica gel-water working pairs. The two-bed configuration is investigated because it yields a desirable compromise between the number of components (heat exchangers, pumps, valves, etc.) and steady cooling rate. For non-recuperative two-bed adsorption heat pumps, the average COP prediction in the literature is 0.39 for experiments and 0.44 for models. It is important to improve the COP in mobile waste heat applications because without high COP, the available waste heat during startup or idle may be insufficient to deliver the desired cooling duty. In this thesis, a COP of 0.53 is predicted for the non-recuperative, silica gel-water chiller. If thermal energy recovery is incorporated into the cycle, a COP as high as 0.64 is predicted for a 90, 35 and 7.0°C source, ambient and average evaporator temperature, respectively. The improvement in COP over heat pumps appearing in the literature is attributed to the adsorbent particle size optimization and careful selection of sorption bed heat exchanger geometry.
35
Sandoval, reyes Mexitli Eva. "Methodology to identify the key variables driving the techno-economic feasibility of Trigeneration – Thermal Storage systems." Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2020. http://www.theses.fr/2020IMTA0182.
Анотація:
Les systèmes de trigénération couplés à du stockage thermique (CCHP-TS) contribuent à la production distribuée d'énergie et à la réduction des émissions de gaz à effet de serre. Néanmoins, il est important d'évaluer leur faisabilité technico-économique pour assurer une mise en oeuvre à long terme. Par ailleurs, la détermination et la caractérisation des variables influentes sont essentielles pour identifier les domaines d'application les plus viables. Potentiellement, cela peut stimuler l'intérêt des chefs de projet, des investisseurs et des décideurs politiques, encourageant ainsi l'adoption de cette technologie. Plusieurs auteurs suggèrent que les prix et les demandes en énergies (électricité, chaleur et froid) sont des variables importantes de la faisabilité technico-économique des systèmes CCHP-TS. Ils ont notamment utilisé le ratio Spark Spread (SS) qui est le rapport entre le coût de l'électricité du réseau et le combustible de cogénération. Cependant, seules quelques études évaluent l’influence combinée des prix et de la demande en énergies, avec certaines limites dans leur modèle, la technologie analysée ou même la résolution temporelle de la demande. Comme la littérature révèle que les prix de l'énergie et les niveaux de demandes sont des variables importantes, cette étude propose et analyse deux hypothèses : 1) Il existe un couplage entre les prix de l'énergie et la variabilité des demandes en énergies qui influe techniquement et économiquement sur la faisabilité des systèmes CCHP-TS; 2) Les prix de l'énergie (électricité et gaz naturel) doivent être considérés séparément plutôt que d’utiliser le ratio Spark Spread. Le travail est divisé en deux phases. La première est une analyse exploratoire visant à démontrer que le modèle utilisé de CCHP-TS est pertinent et sensible aux variables d'analyse (prix et demandes énergétiques). La seconde est une analyse de sensibilité rigoureuse qui permet de plus une comparaison de trois «approches» : Morris, Sobol et VARS. Les résultats indiquent que les prix de l'énergie et l’importance de la demande électrique sont les variables les plus importantes pour garantir la faisabilité d'un système CCHP-TS. L'ordre d’importance entre les prix de l'énergie diffère selon que l’indicateur de performance économique utilisé soit absolu (montant d'économies réalisées [en dollar(s) US]) ou relatif (pourcentage d'économies réalisées [%]). Dans les deux cas, le prix du carburant est la variable ayant un effet d'interaction avec les autres variables le plus importants. La méthodologie de la première phase intègre des outils tels que le plan d'expériences factoriel complet, l'outil de simulation et d'optimisation DER-CAM et une nouvelle combinaison de la méthode de clustering k-Means et d’une méthode d’aide à la décision multicritère (MCDM). Pour la deuxième phase, il s'agit principalement de l'utilisation des méthodes globales d'analyse de sensibilité et de l'adaptation d'un modèle CCHP-TS programmée en langage Python qui utilise la bibliothèque d'optimisation PYOMO et le solveur CPLEX. Dans cette deuxième phase, la mise en oeuvre des trois méthodes d’analyse de sensibilité a permis une identification des avantages et limites de chacune. L’analyse de la faisabilité techno-économique s’en trouve renforcée en utilisant leurs complémentaritésTrigeneration systems with thermal storage (CCHP-TS) contribute to the distributed generation of energy and the reduction of greenhouse gas emissions. Nevertheless, it is important to assess their techno-economic feasibility to ensure long-term implementation. Moreover, determining and characterizing the influential variables is essential to identify the most viable application fields. Potentially, this could foster the interest of project managers, investors, and policymakers, therefore encouraging the adoption of this technology. Several authors suggest that energy prices and loads are important variables for the techno-economic feasibility of CCHP-TS systems. Particularly they have explored the Spark Spread rate, a ratio between the cost of electricity from the grid and the CHP fuel. However, just a few studies are assessing the prices and loads together, with some limitations in their model, the technology analyzed, or even the resolution of the loads. As the literature reveals that energy prices and loads size are important variables, this study aims to analyze two hypotheses proposed: 1) There is a combination of energy prices and the size of the annual energy loads that makes techno-economically feasible a CCHP-TS system; 2) The energy prices (electricity and natural gas) should be considered separately instead of consolidating them into the spark spread rate (SS). The analysis is divided into two phases. The first one is an exploratory analysis aiming to demonstrate that the model for CCHP-TS is relevant and sensitive to the variables of analysis (energy prices and loads). The second is a rigorous sensitivity analysis and the comparison of three approaches: Morris, Sobol, and VARS. The results state that energy prices and the annual size of the electric load are the most relevant variables on the feasibility of a CCHP-TS system. The order of relevance between the energy prices relies on the measure used for the economic performance: either absolute (expressed in the amount of savings [in US dollar(s)]) or relative (expressed in the percentage of savings [%]). But in both cases, the price of the fuel is the variable with the largest interaction effects. The methodology of the first phase incorporates tools such as full factorial design of experiments (DoE), DER-CAM simulation and optimization tool, and a novel combination of k-Means clustering and multicriteria decision making (MCDM). For the second phase, it is mainly the use of global sensitivity analysis methods and the adaptation of a CCHP-TS model into the programming language Python, using the optimization library PYOMO and the solver CPLEX. In this second phase, the implementation of the three sensitivity analysis methods allowed identifying their advantages and limitations. Moreover, this complementarity thereby reinforced the techno-economic feasibility analysis
36
Ercolanelli, Julien. "Étude numérique et expérimentale d'un système couplé stabilisateur et récupérateur d'énergie des vagues Experimental and numerical investigation of sloshing in anti-roll tank using effective gravity angle Experimental and numerical assessment of the performance of a new type passive anti-roll stabilisation system." Thesis, Brest, École nationale supérieure de techniques avancées Bretagne, 2019. http://www.theses.fr/2019ENTA0008.
Анотація:
Le développement de Geps Techno est basé sur un concept innovant de structure flottante destinée à produire de l'énergie électrique à partir de plusieurs sources d'énergies marines renouvelables dont la source houlomotrice. Le système houlomoteur développé par Geps Techno repose sur la mise en circulation d'eau et la création d'un tourbillon en son sein. En profitant du phénomène de carène liquide, le concept est également déclinable en un système de stabilisation de navire ou de toute autre plateforme flottante. L'objectif à court terme de la société est le développement de cette technologie permettant la stabilisation et la récupération de l'énergie des vagues et pour lequel il reste des verrous technologiques à lever afin d'arriver à la viabilité et la rentabilité du système. Pour cela, Geps Techno a lancé en octobre 2015 le projet IHES (Integrated Harvesting Energy System) qui consiste à construire un démonstrateur de son concept de plateforme houlomotrice. Le projet IHES est un des projets de la feuille de route du plan "Navires écologiques" de la Nouvelle France Industrielle. Il est soutenu par Bpifrance dans le cadre du programme d'Investissements d'Avenir - Projets Industriels d'Avenir. Afin de maîtriser les objectifs de stabilisation et de récupération d'énergie, Geps Techno étudie les volets technologiques nécessaires permettant de passer de l'énergie disponible au niveau des vagues jusqu'à celle disponible au niveau de la turbine du houlomoteur. Les travaux de thèse soutenus par Fourestier en mai 2017 portaient sur un premier volet "Définition et contrôle des écoulements internes au système houlomoteur". A l'aide d'une modélisation des fluides numériques, ces derniers ont abouti à des modèles opérationnels caractérisant les écoulements internes. La présente thèse Cifre s'inscrit dans la continuité des travaux de Fourestier et traite d'un second volet "Modélisation du système couplé plateforme / houlomoteur". L'ensemble de ces travaux devra aboutir à un code de calcul opérationnel et corrélé à des résultats expérimentaux permettant d'étudier l'écoulement interne et le comportement du flotteur soumis à la houleGeps Techno's development is based on an innovative concept of a floating structure intended to produce electrical energy from several renewable marine energy sources, including wave power. The wave power system developed by Geps Techno is based on circulating water and creating a vortex within it. By taking advantage of the liquid hull phenomenon, the concept can also be used as a stabilization system for a ship or any other floating platform. The short-term objective of the company is the development of this technology allowing the stabilization and recovery of wave energy and for which there remain technological obstacles to be removed in order to achieve the viability and profitability of the system. To do this, in October 2015 Geps Techno launched the IHES (Integrated Harvesting Energy System) project, which consists of building a demonstrator of its wave power platform concept. The IHES project is one of the projects of the roadmap of the "Ecological ships" plan of New Industrial France. It is supported by Bpifrance within the framework of the Investments for the Future - Industrial Projects for the Future program. In order to master the objectives of stabilization and energy recovery, Geps Techno is studying the technological aspects necessary to switch from the energy available at wave level to that available at the wave turbine turbine. The Ph.D. thesis work supported by Fourestier in May 2017 focused on a first part "Definition and control of internal flows in the wave power system". Using CFD modeling, the latter resulted in operational models characterizing internal flows. This Cifre Ph.D. thesis follows on from Fourestier's work and deals with a second part "Modeling of the coupled platform / wave power system". All of this work should lead to an operational computer code correlated with experimental results making it possible to study the internal flow and the behavior of the float subjected to swell
37
Norberg, Daniel. "Quantum Chemical Studies of Radical Cation Rearrangement, Radical Carbonylation, and Homolytic Substitution Reactions." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8178.
38
Friis, Cecilie. "Land use change in a globalised world." Doctoral thesis, Humboldt-Universität zu Berlin, 2017. http://dx.doi.org/10.18452/18180.
Анотація:
Die weltweit steigende Nachfrage nach land-basierten Rohstoffen erhöht stetig den Druck auf Land und Landnutzung, vor allem in ressourcenreichen Frontierregionen. Eine gegenwärtige Erscheinungsform dessen stellen Transnationale Landnahmen dar, die den Landnutzungswandel vorantreiben und die landbasierte Lebensgrundlage insbesondere der ländlichen Bevölkerung in vielen Teilen der Welt massiv bedroht. Ziel dieser Doktorarbeit ist es, ein besseres Verständnis der komplexen Prozesse zu schaffen, die Landnahmen befördern. Erstens untersucht sie die rezente Konjunktur des Bananenanbaus in der Provinz Luang Namtha, Laos, die von Chinesischen Investoren getrieben wird. Zweitens zieht die Arbeit das telecoupling Konzept heran und unterzieht es einer kritischen Diskussion in Bezug auf seinen Mehrwert für die Analyse räumlich entkoppelter sozioökonomischer und ökologischer Wechselwirkungen. Eine mehrmonatige ethnographische Feldforschung und deren qualitative Analyse stellen die Grundlage dieser Arbeit dar. Ausgehend von zwei Bananenplantagen in einer kleinen ländlichen Gemeinde fokussiert die Arbeit die Mechanismen und Prozesse, die die Bananenexpansion befördern. Das telecoupling Konzept dient als Instrument, um zu analysieren, welchen Einfluss die multiplen und ko-konstitutiven Interaktionen auf den Vorstoß des Bananenanbaus haben. Darüber hinaus verdeutlichen die tiefgehenden lokalitätsbezogenen Analysen die verschiedenen Kontexte auf, die dieses Wechselspiel spezifisch lokal verorten und gestalten. Die Fallstudie zeigt auf, wie die räumlich entkoppelten Beziehungen durch ein grenzüberspannendes Netzwerk chinesischer Investoren mit sozialen Verbindungen in die Provinz hinein, sowie auf den (chinesischen) Obstmarkt vermittelt werden. Außerdem stellt die Studie heraus, dass die Strategien der Investoren zur Landgewinnung und der daraus resultierende verheerende Landnutzungswandel einer Entfremdung der Dorfbewohner_innen ‘vom Boden’ gleichkommen. Durch die empirische, methodologische sowie konzeptuelle Auseinandersetzung mit dem telecoupling Konzept verweist die Arbeit letztlich auf den Wert qualitativer Analysen für die schwer greifbaren, ‚immateriellen’ Interaktionen sowie mögliche Feedbackmechanismen, welche Landnutzungswandel in einer globalisierten Welt bestimmen.The global demand for land resources has increased the pressures on land, especially in resource-rich frontier regions. Transnational land acquisitions constitute one of these pressures that currently shape land use change and threaten land access and land-based livelihoods in rural areas. This thesis contributes to create a better understanding of the complex processes involved in such land acquisitions in two ways. First, it examines a recent boom in banana cultivation in Luang Namtha Province, Lao PDR driven by Chinese investors leasing land from Lao farmers and exporting the bananas to China. Second, it critically engages with the emerging telecoupling framework proposed in Land System Science as an analytical framework for dealing with distal causal interactions. Based on ethnographic fieldwork and using qualitative analyses, the thesis examines two plantations in a small village and traces the actors, mechanisms and processes driving the banana expansion. Using the telecoupling framework as a heuristic device, the study illuminates how multiple and co-constitutive economic, environmental, political and discursive interactions influence the banana expansion. Furthermore, the in-depth place-based analyses reveal how different contextual factors ground and shape these interactions in this particular location. In this case, the distal interactions are mediated through a cross-border network of Chinese investors with social ties in the local area, as well as in the fruit market in China. The study shows that the investors’ strategies to obtain access to the land combined with the resulting destructive land use conversion amount to an alienation of land from the villagers. By engaging empirically, methodologically and conceptually with the telecoupling framework, the thesis advances the discussion on telecoupling by demonstrating the value of qualitative analysis for capturing some of the more elusive and immaterial interactions, as well as potential feedbacks influencing land use change in a globalised world.
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Bernard, Brian Patrick. "Wave Propagation in Nonlinear Systems of Coupled Oscillators." Diss., 2014. http://hdl.handle.net/10161/9111.
Анотація:
Mechanical oscillators form the primary structure of a wide variety of devices including energy harvesters and vibration absorbers, and also have parallel systems in electrical fields for signal processing. In the area of wave propagation, recent study in periodic chains have focused on active tuning methods to control bandgap regions, bands in the frequency response in which no propagating wave modes exist. In energy harvesting, several coupled systems have been proposed to enhance the peak power or bandwidth of a single harvester through arrays or dynamic magnification. Though there are applications in several fields, the work in this dissertation can all fit into the category of coupled non-linear oscillators. In each sub-field, this study demonstrates means to advance state of the art techniques by adding nonlinearity to a coupled system of linear oscillators, or by adding a coupled device to a nonlinear oscillator.
The first part of this dissertation develops the analytical methods for studying wave propagation in nonlinear systems. A framework for studying rotational systems is presented and used to design an testbed for wave propagation experiments using a chain of axially aligned pendulums. Standard analytical methods are also adapted to allow uncertainty analysis techniques to provide insight into the relative impact of variations in design parameters. Most analytical insight in these systems is derived from a linearlized model and assumes low amplitude oscillations. Additional study on the nonlinear system is performed to analyze the types of deviations from this behavior that would be expected as amplitudes increase and nonlinear effects become more prominent.
The second part of this dissertation describes and demonstrates the first means of passive control of bandgap regions in a periodic structure. By imposing an asymmetrical bistability to an oscillator in each unit cell, it is analytically shown that each potential well has different wave propagation behaviors. Experimental demonstrations are also provided to confirm the simulated results.
The final section performs analytical and numerical analysis of a new system design to improve the performance of a nonlinear energy harvester by adding an excited dynamic magnifier. It is shown that this addition results in higher peak power and wider bandwidth than the uncoupled harvester. Unlike standard dynamic magnifiers, this performance does not come at the expense of power efficiency, and unlike harvester arrays, does not require the added cost of multiple energy harvesters.
Dissertation
40
Ribeiro, José Luís Baía. "Integration and Optimization of Energy Data Analysis Systems." Master's thesis, 2014. http://hdl.handle.net/10316/35610.
Анотація:
Dissertação de Mestrado em Engenharia Informática apresentada à Faculdade de Ciências e Tecnologia da Universidade de CoimbraInternet of Things (IoT) is a concept that recently became mainstream with the launch of numerous consumer products, some of them dedicated to Home Energy Management. Due of its novelty and immaturity, IoT Platforms should be designed for change. This project aimed to provide an existing data analysis mechanism as a service to third-parties and enable the usage of custom energy management devices by an existing data monitoring application. To achieve this, a service-oriented system was created that allows third-parties to send energy consumption data and receive the classi cation's result as soon as possible, in isolation of the remaining system; an IoT communication protocol was used to allow energy management devices to send data in degraded network conditions and with low power consumption. This solution enables future projects of the company to reuse its components, such as the generic time-series storage platform developed in the process.
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"Molecules for Energy and Charge Transfer for Biomimetic Systems: Synthesis, Characterization and Computational Studies." Doctoral diss., 2016. http://hdl.handle.net/2286/R.I.40346.
Анотація:
abstract: Sunlight, the most abundant source of energy available, is diffuse and intermittent; therefore it needs to be stored in chemicals bonds in order to be used any time. Photosynthesis converts sunlight into useful chemical energy that organisms can use for their functions. Artificial photosynthesis aims to use the essential chemistry of natural photosynthesis to harvest solar energy and convert it into fuels such as hydrogen gas. By splitting water, tandem photoelectrochemical solar cells (PESC) can produce hydrogen gas, which can be stored and used as fuel. Understanding the mechanisms of photosynthesis, such as photoinduced electron transfer, proton-coupled electron transfer (PCET) and energy transfer (singlet-singlet and triplet-triplet) can provide a detailed knowledge of those processes which can later be applied to the design of artificial photosynthetic systems. This dissertation has three main research projects. The first part focuses on design, synthesis and characterization of suitable photosensitizers for tandem cells. Different factors that can influence the performance of the photosensitizers in PESC and the attachment and use of a biomimetic electron relay to a water oxidation catalyst are explored. The second part studies PCET, using Nuclear Magnetic Resonance and computational chemistry to elucidate the structure and stability of tautomers that comprise biomimetic electron relays, focusing on the formation of intramolecular hydrogen bonds. The third part of this dissertation uses computational calculations to understand triplet-triplet energy transfer and the mechanism of quenching of the excited singlet state of phthalocyanines in antenna models by covalently attached carotenoids.Dissertation/Thesis
Doctoral Dissertation Chemistry 2016
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Sen, Sangita. "Multi-reference coupled-cluster studies on the effect of dynamical and non-dynamical correlation on molecular energies and properties." Thesis, 2019. http://hdl.handle.net/10821/8223.
Анотація:
In this thesis it has been formulated and implemented a suite of related multi-reference coupled cluster theories to describe open-shell molecular systems taking care to maintain spin-adaptation of the wave function and incorporate the effects of electron correlation and orbital relaxation to the greatest extent possible within the limits of computational and theoretical viability.Research was carried out under the supervision of Prof. Debasish Mukherjee and Dr. Ankan Paul of RCAMOS under SCS [School of Chemical Sciences]
Research was conducted under grant of CSIR, India for the Shyama Prasad Mukherjee Fellowship, and DST, India. Also there are sponsorship from abroad , i.e. CEFIPRA/IFCPAR for funding academic visits to Toulouse, France, CTCC, Oslo, Norway.
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Zheng, Tianyuan. "A fully coupled thermo-hydro-mechanical finite element model of freezing in porous media and its application for ground source heat pump systems." Doctoral thesis, 2018. https://tud.qucosa.de/id/qucosa%3A34033.
Анотація:
To uilize the shallow geothermal energy, heat pumps are often coupled with borehole heat exchangers (BHE) for heating and cooling buildings. In cold regions, soil freezing around the BHE is a potential
problem which can seriously influence the underground soil temperature distribution, inlet and outlet fluid temperature of the BHE, and thus the efficiency of the whole GSHP system. The influence of the
freezing process on the overall system performance is investigated by comparing different BHE configuration with and without latent heat effect from the frozen groundwater. The coefficient of performance (COP) of the heat pump will alter when freezing process in taken into account and lead to various electricity consumption. Except for the efficiency aspect, the freezing behavior can also lead to the redistribution of pore pressure and fluid flow, and in some extreme cases can even result in frost damage to the BHEs. A fully coupled thermohydro-mechanical model is required for advanced system design and scenario analyses. Based on the framework of the Theory of Porous Media, a triphasic freezing model is derived and solved with the finite element method. Ice formation in the porous medium results from a coupled heat and mass transfer problem with phase transition and is accompanied by volume expansion. The model is able to capture various coupled physical phenomena through the freezing process including the latent heat effect, groundwater flow with porosity change and mechanical deformation. With this kind of THM freezing model, we are also able to solve different kinds of engineering problem, e.g. geotechnics, construction engineering and material engineering.
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Smith, Keith Cameron. "Coupled Dynamic Analysis of Flow in the Inlet Section of a Wave Rotor Constant Volume Combustor." 2011. http://hdl.handle.net/1805/2969.
Анотація:
Indiana University-Purdue University Indianapolis (IUPUI)A wave rotor constant volume combustor (WRCVC) was designed and built as a collaborative work of Rolls Royce LibertyWorks, Indiana University-Purdue University at Indianapolis (IUPUI), and Purdue University, and ran experimental tests at Purdue's Zucrow Laboratories in 2009. Instrumentation of the WRCVC rig inlet flow included temperature and pressure transducers upstream of the venturi and at the fuel delivery plane. Other instrumentation included exhaust pressures and temperatures. In addition, ion sensors, dynamic pressure sensors, and accelerometers were used to instrument the rotating hardware. The rig hardware included inlet guide vanes directly in front of the rotating hardware, which together with concern for damage potential, prevented use of any pressure transducers at the entrance to the rotor. For this reason, a complete understanding of the conditions at the WRCVC inlet is unavailable, requiring simulations of the WRCVC to estimate the inlet pressure at a specific operating condition based on airflow. The operation of a WRCVC rig test is a sequence of events over a short time span. These events include introduction of the main air flow followed by time-sequenced delivery of fuel, lighting of the ignition source, and the combustion sequence. The fast changing conditions in the rig inlet hardware make necessary a time-dependent computation of the rig inlet section in order to simulate the overall rig operation. The chosen method for computing inlet section temperature and pressure was a time-dependent lumped volume model of the inlet section hardware, using a finite difference modified Euler predictor-corrector method for computing the continuity and energy equations. This is coupled with perfect gas prediction of venturi air and fuel flow rates, pressure drag losses at the fuel nozzles, pressure losses by mass addition of the fuel or nitrogen purge, friction losses at the inlet guide vanes, and a correlation of the non-dimensional flow characteristics of the WRCVC. The flow characteristics of the WRCVC are computed by varying the non-dimensional inlet stagnation pressure and the WRCVC's operational conditions, assuming constant rotational speed and inlet stagnation temperature. This thesis documents the creation of a computer simulation of the entire WRCVC rig, to understand the pressure losses in the inlet system and the dynamic coupling of the inlet section and the WRCVC, so that an accurate prediction of the WRCVC rotor inlet conditions can be computed. This includes the computational development of the WRCVC upstream rig dynamic model, the background behind supporting computations, and results for one test sequence. The computations provide a clear explanation of why the pressures at the rotor inlet differ so much from the upstream measured values. The pressure losses correlate very well with the computer predictions and the dynamic response tracks well with the estimation of measured airflow. A simple Fortran language computer program listing is included, which students can use to simulate charging or discharging of a container.
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Lozano, Adolfo. "Analysis of a novel thermoelectric generator in the built environment." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-08-4131.
Анотація:
This study centered on a novel thermoelectric generator (TEG) integrated into the built environment. Designed by Watts Thermoelectric LLC, the TEG is essentially a novel assembly of thermoelectric modules whose required temperature differential is supplied by hot and cold streams of water flowing through the TEG. Per its recommended operating conditions, the TEG nominally generates 83 Watts of electrical power. In its default configuration in the built environment, solar-thermal energy serves as the TEG’s hot stream source and geothermal energy serves as its cold stream source. Two systems-level, thermodynamic analyses were performed, which were based on the TEG’s upcoming characterization testing, scheduled to occur later in 2011 in Detroit, Michigan.
The first analysis considered the TEG coupled with a solar collector system. A numerical model of the coupled system was constructed in order to estimate the system’s annual energetic performance. It was determined numerically that over the course of a sample year, the solar collector system could deliver 39.73 megawatt-hours (MWh) of thermal energy to the TEG. The TEG converted that thermal energy into a net of 266.5 kilowatt-hours of electricity in that year. The second analysis focused on the TEG itself during operation with the purpose of providing a preliminary thermodynamic characterization of the TEG. Using experimental data, this analysis found the TEG’s operating efficiency to be 1.72%.
Next, the annual emissions that would be avoided by implementing the zero-emission TEG were considered. The emission factor of Michigan’s electric grid, RFCM, was calculated to be 0.830 tons of carbon dioxide-equivalent (CO2e) per MWh, and with the TEG’s annual energy output, it was concluded that 0.221 tons CO2e would be avoided each year with the TEG. It is important to note that the TEG can be linearly scaled up by including additional modules. Thus, these benefits can be multiplied through the incorporation of more TEG units.
Finally, the levelized cost of electricity (LCOE) of the TEG integrated into the built environment with the solar-thermal hot source and passive ground-based cold source was considered. The LCOE of the system was estimated to be approximately $8,404/MWh, which is substantially greater than current generation technologies. Note that this calculation was based on one particular configuration with a particular and narrow set of assumptions, and is not intended to be a general conclusion about TEG systems overall. It was concluded that while solar-thermal energy systems can sustain the TEG, they are capital-intensive and therefore not economically suitable for the TEG given the assumptions of this analysis. In the end, because of the large costs associated with the solar-thermal system, waste heat recovery is proposed as a potentially more cost-effective provider of the TEG’s hot stream source.text
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Mays, Mona Leila. "The study of interplanetary shocks, geomagnetic storms, and substorms with the WINDMI model." 2009. http://hdl.handle.net/2152/10703.
Анотація:
WINDMI is a low dimensional plasma physics-based model of the coupled magnetosphere-ionosphere system. The nonlinear system of ordinary differential equations describes the energy balance between the basic nightside components of the system using the solar wind driving voltage as input. Of the eight dynamical variables determined by the model, the region 1 field aligned current and ring current energy is compared to the westward auroral electrojet AL index and equatorial geomagnetic disturbance storm time Dst index. The WINDMI model is used to analyze the magnetosphere-ionosphere system during major geomagnetic storms and substorms which are community campaign events. Numerical experiments using the WINDMI model are also used to assess the question of how much interplanetary shock events contribute to the geoeffectiveness of solar wind drivers. For two major geomagnetic storm intervals, it is found that the magnetic field compressional jump is important to producing the changes in the AL index. Further, the WINDMI model is implemented to compute model AL and Dst predictions every ten minutes using real-time solar wind data from the ACE satellite as input. Real-Time WINDMI has been capturing substorm and storm activity, as characterized by the AL and Dst indices, reliably since February 2006 and is validated by comparison with ground-based measurements of the indices. Model results are compared for three different candidate input solar wind driving voltage formulas. Modeling of the Dst index is further developed to include the additional physical processes of tail current increases and sudden commencement. A new model, based on WINDMI, is developed using the dayside magnetopause and magnetosphere current systems to model the magnetopause boundary motion and the dayside region 1 field aligned current which is comparable to the auroral upper AU index.text
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Michaud, Douce. "Effet de chaperones pharmacologiques sur les formes mutantes du récepteur mélanocortine de type 4 responsables de l'obésité morbide précoce." Thèse, 2009. http://hdl.handle.net/1866/3347.
Анотація:
Le récepteur mélanocortine de type 4 (MC4R) est un récepteur couplé aux protéines G impliqué dans la régulation de la prise alimentaire et de l’homéostasie énergétique. Quatre-vingt pour cent des mutants du MC4R reliés à l’obésité morbide précoce (OMP) sont retenus à l’intérieur de la cellule. Le système de contrôle de qualité (SCQ) est probablement responsable de cette rétention, par la reconnaissance d’une conformation inadéquate des mutants. Le rétablissement de l’expression à la surface cellulaire et de la fonctionnalité de ces mutants est donc d’intérêt thérapeutique. Dans cette optique, des composés lipophiles spécifiques pour le MC4R ont été sélectionnés sur la base de leur sélectivité. Nous avons démontré qu’ils agissent à titre de chaperone pharmacologique (CP) en rétablissant l’expression à la surface cellulaire et la fonctionnalité des récepteurs mutants S58C et R165W, et qu’ils favorisent leur N-glycosylation complexe (maturation). Le suivi par BRET du site d’action des CP du MC4R suggère une action en aval de l’interaction calnexine-MC4R. De manière générale, une CP peut avoir un effet différent selon le mutant traité en induisant des conformations distinctes du récepteur plus ou moins aptes à se dissocier du SCQ et à activer la voie de signalisation, et un mutant peut répondre différemment selon la CP utilisée par des différences d’affinité pour le ligand, la CP et les effecteurs. Une meilleure compréhension du mode d’action des CP pourrait aider au développement de nouvelles approches thérapeutiques non seulement pour l’OMP, mais aussi pour d’autres maladies conformationnelles causées par le mauvais repliement de protéines.The MC4R is a G-protein coupled receptor involved in the central regulation of food intake and energy homeostasis. Eighty percent of childhood obesity-related MC4R mutants are retained intracellularly, probably via the quality control system acting on misfolded receptors. Thus, rescuing cell surface targeting and functionality of these mutant receptors could be of therapeutic value. Cell permeable MC4R selective ligands have been tested and were able to restore cell surface expression and signalling activity of S58C and R165W MC4R mutants. Those compounds, according to their mode of action, are described as pharmacological chaperones (PC). The MC4R-PCs also helps to rescue the glycosylation pattern (maturation) of the MC4R mutants. The site of action of MC4R-PCs of the MC4R mutants monitored by BRET suggests an action downstream of the calnexin-MC4R interaction, most likely at the level of the Golgi apparatus. Generally, a CP can have different effects according to the mutant by stabilizing distinct conformations of the receptor that are more or less able to exit the quality control system and to activate the signaling pathway, and a mutant can respond differently according to the CP used by its distinct affinity to the ligand, the CP itself and the effectors. A better understanding of PCs’ mode of action could help in the design of novel therapeutic approaches not only for early-onset morbid obesity (EOMO) but also for other conformational diseases resulting from protein misfolding.