Dissertations / Theses on the topic 'SAND BATTERY'

Ces travaux portent sur la récupération et le stockage d’énergie pour l’alimentation de capteurs sans fil dans un contexte aéronautique. Dans un premier temps, nous présentons la problématique particulière de l’alimentation des capteurs sans fil dans un tel domaine et dressons un état de l’art des différentes technologies de stockage et de récupération pouvant répondre à ce besoin. Dans un deuxième temps, à travers l’étude et la réalisation de deux récupérateurs, nous montrons les possibilités qu’apporte cette technologie et détaillons les contraintes de conception qu’impose le milieu afin d’obtenir une alimentation robuste et fiable. Le premier récupérateur présenté est une alimentation photovoltaïque située sur l’extrados de l’aile d’un A321 alimentant des bandes de capteurs sans fil proches. Le système fournit 2 watts, fonctionne par temps couvert et résiste aux températures fortement négatives (-50°C) et aux basses pressions (200hPa) qui sont rencontrées à l’altitude de croisière de cet appareil. Le deuxième récupérateur est une alimentation thermoélectrique placée dans le mât réacteur d’un A380 pour alimenter un système de capteurs dédié à la surveillance de l’état de structure. Le système résiste aux températures élevées (300°C) et aux importantes vibrations de la zone d’installation et produit l’énergie nécessaire à l’alimentation du système de capteurs. Les choix et les étapes de conception ayant menés aux deux systèmes sont détaillés, tant au niveau de l’assemblage mécanique que des circuits électroniques<br>This work deals with energy harvesting and storage to power aircraft embedded wireless sensors. First, we discuss the issue of powering wireless sensors in an aircraft and we present a state of the art of the various energy harvesting and storage technologies that could be used. Then, through the design and construction of two harvesters, we show the possibilities offered by this technology and we explain the design constraints imposed by the application to get a reliable and robust power supply. The first harvester is a photovoltaic power supply located on the upper surface of an A321’s wing supplying a wireless sensors belt nearby. The systems provides 2 watts to the load, works with cloudy weather and is highly resistant to negative temperature (-50°C) and low pressure (200hPa) that are met at aircraft cruising altitude. The second harvester is a thermoelectric power supply located in an A380 pylon supplying a structural health monitoring system. The harvester is highly resistant to high temperature (300°C) and severe vibrations of the installation area and manages to generate the required energy to supply the structural health monitoring sensors. Mechanical and electronic design steps and choices that led to both harvesters are detailed and discussed

Les réseaux de capteurs sans fil sont constitués de noeuds capteurs, capables de récolter des données, de les analyser et de les transmettre. Ces réseaux ont plusieurs applications, en fonction de la zone où ils sont déployés. Application militaire ou de sauvetage dans des zones pouvant être inaccessibles aux humains ; application sanitaire avec des capteurs déployés sur et dans le corps humain ; application de surveillance avec des capteurs sur les voitures d'un ville, ou les arbres d'une forêt. Les noeuds sont autonomes en énergie et il est primordial d'assurer leur longévité sans retarder la récolte des données. La tache principale réalisée par les réseaux de capteurs sans fils consiste à effectuer des mesures et à envoyer ces données jusqu'à un noeud coordinateur. Cette tache d'agrégation est effectuée régulièrement, ce qui en fait la plus consommatrice d'énergie. L'étude approfondie de la consommation d'énergie des capteurs, qui au centre de ma thèse, peut se traduire de différentes manières. Premièrement, nous avons étudié la complexité du problème de l'agrégation de données en utilisant un modèle simplifié pour représenter un réseau de capteurs sans fils. Secondement, nous nous sommes concentrés sur l'estimation de cette durée de vie. Nous présentons WiSeBat, un modèle de batterie et de consommation d'énergie optimisé pour les réseaux de capteurs, implémenté dans le simulateur WSNET. Après validation, nous l'utilisons pour comparer les performances des algorithmes de broadcast efficaces en énergie<br>A wireless sensor network is an ad-hoc network connecting small devices equipped with sensors. Such networks are self-organized and independent of any infrastructure. The deployment of a WSN is possible in areas inaccessible to humans, or for applications with a long lifetime requirement. Indeed, devices in a wireless sensor network are usually battery-powered, tolerate failure, and may use their own communication protocols, allowing them to optimize the energy consumption. The main application of WSNs it to sense the environment at different locations and aggregate all the data to a specific node that logs it and can send alerts if necessary. This task of data aggregation is performed regularly, making it the most energy consuming. As reducing the energy consumed by sensor is the leading challenge to ensure sustainable applications, we tackle in this thesis the problem of aggregating efficiently the data of the network. Then, we study lifetime evaluation techniques and apply it to benchmark existing energy-centric protocols

Ces travaux portent sur la question de l’autonomie énergétiquedes capteurs sans fil dans un contexte aéronautique, à laquelle la récupérationet le stockage d’énergie ambiante sont susceptibles d’apporter uneréponse. Nous étudions dans un premier temps la génération thermoélectrique,destinée à être appliquée au suivi du vieillissement structurelprès de la zone moteur, et débouchant sur la réalisation d’un démonstrateur.Nous proposons ensuite une architecture de stockage capacitif qui,en s’adaptant à son état de charge, vise à améliorer la performance de cettesolution de stockage en termes de temps de démarrage, de taux d’utilisationd’énergie et sous certaines conditions, de transfert d’énergie. Finalement,nous rapportons les résultats d’une étude prospective sur la récupérationd’énergie du vent relatif grâce au phénomène aéroacoustique. Nousmontrons que cette méthode présente un potentiel énergétique intéressant,puis nous présentons la conception et la réalisation d’un circuit optimiséde gestion de l’énergie, permettant d’alimenter grâce à cette technique uncapteur sans fil de température<br>This work adresses the issue of energy autonomy within wirelesssensor networks embedded in aircrafts, which may be solved throughambient energy harvesting and storage. In a first study, we develop a demonstratorbased on thermal gradients energy harvesting, which is designedto supply power to a structural health monitoring system implementednear the engine zone. Thereafter, we introduce a capacitive storagearchitecture which self-adapts to its own state of charge, aiming at improvingits performance in terms of startup time, the energy utilization ratioand under some conditions, the energy transfer. Finally, we report the resultsof a prospective study on aeroacoustic energy harvesting appliedto the relative wind. It is shown that this method exhibits an interestingpotential in terms of generated power, then we introduce the design andthe realization of an optimized energy management circuit, allowing ourtechnique to supply power to a wireless temperature sensor

Cette thèse s’inscrit dans le cadre de la validation du concept « Flexy Energy » developpé par le laboratoire Energie Solaire et Economie d'Energie de la fondation 2iE. Qui consiste en la production décentralisée d’électricité via les centrales hybrides PV/diesel (gasoil et biocarburant) sans stockage d’énergie dans les batteries d’accumulateurs et avec une gestion intelligente de la production et des charges à alimenter. Une installation pilote basée sur ce concept, constituée d’un groupe électrogène de 11,5 kVA couplé à un champ PV de 2,85 kWc via un onduleur de 3,3 kW, a été mise en place dans le cadre de cette thèse. L’étude expérimentale du prototype «Flexy Energy» a permis dans un premier temps d’évaluer les performances du système (consommation spécifique du groupe Diesel et production du champ PV) pour différents profils de charge et d’ensoleillement. Cette partie de l’étude a fait ressortir la nécessité d’une gestion intelligente de la production et des charges au sein du système afin de toujours lui garantir une meilleure efficacité quelles que soient les conditions de charge. Ensuite, l’étude expérimentale a porté sur l’impact du générateur PV sur les paramètres électriques du réseau local. A ce niveau les distorsions harmoniques (en tension et en courant) ainsi que la stabilité de la tension du réseau ont été étudiés. La dernière partie de cette thèse a consisté en la modélisation et l’optimisation des systèmes hybrides PV/Diesel sans stockage. Le travail réalisé ici se positionne comme un premier pas vers des applications numériques (solutions logicielles ou progicielles) en mesure de dimensionner et d’optimiser les systèmes hybrides PV/Diesel sans stockage avec une gestion intelligente de laproduction et des charges<br>An original ‘‘Flexy Energy’’ concept of hybrid solar PV/Diesel power plant, without battery storage has been developed by the Solar Energy and Energy Saving laboratory (SEESL) of 2iE foundation. This concept consists of decentralized electricity generation trough hybrid solar PV/Diesel generators systems without energy storage in batteries and with a smart management of the energy production and loads in the system. This thesis joins in the framework of the validation of this concept. In this sense, an experimental prototype based on this concept has been set up. This facility consists of a PV array of 2. 85 kWp coupled with a diesel generator rated at 9. 2 kW via a single phase inverter of 3. 3 kW. First, the experimental study of the “Flexy Energy” prototype shows that the system is efficient for periods of higher solar radiations and for higher loads. Indeed, this situation allows each generator (PV and Diesel) to operate in optimal way. This part of the study has pointed out the importance of a smart management of the energy production and loads in such a facility, in order to enhance its efficiency whatever are load conditions. A second aspect of the experimental study has concerned the impact of the PV generator on the grid electrical parameters. The voltage and current harmonic distortions, voltage unbalance and voltage rise are studied. Finally, this work concerns the modeling of hybrid PV/Diesel systems without storage. The model developed is a first stage for numerical applications (software or software package), useful in the sizing and the optimization of such systems with a smart management of energy production and loads

Face à l'explosion du trafic mobile entraînée par le succès des smartphones, les opérateurs de réseaux mobiles (MNOs) densifient leurs réseaux à travers le déploiement massif des stations de base à faible portée (SBS), capable d’offrir des services très haut débit et de remplir les exigences de capacité et de couverture. Cette nouvelle infrastructure, appelée réseau cellulaire hétérogène (HetNet), utilise un mix de stations de base hiérarchisées, comprenant des macro-cellule à forte puissance et des SBS à faible puissance.La prolifération des HetNets soulève une nouvelle préoccupation concernant leur consommation d'énergie et empreinte carbone. Dans ce contexte, l'utilisation de technologies de production d'énergie dans les réseaux mobiles a suscité un intérêt particulier. Les sources d'énergie respectueuses de l'environnement couplées à un système de stockage d'énergie ont le potentiel de réduire les émissions carbone ainsi que le coût opérationnel énergétique des MNOs.L'intégration des énergies renouvelables (panneau solaire) et du stockage d'énergie (batterie) dans un SBS gagne en efficacité grâce aux leviers technologiques et économiques apportés par le smart grid (SG). Cependant, l'architecture résultante, que nous appelons Green Small-Cell Base station (GSBS), est complexe. Premièrement, la multitude de sources d'énergie, le phénomène de viellissement du système et le prix dynamique de l'électricité dans le SG sont des facteurs qui nécessitent planification et gestion pour un fonctionnement plus efficace du GSBS. Deuxièmement, il existe une étroite dépendance entre le dimensionnement et le contrôle en temps réel du système, qui nécessite une approche commune capable de résoudre conjointement ces deux problèmes. Enfin, la gestion holistique d’un HetNet nécessite un schéma de contrôle à grande échelle pour optimiser simultanément les ressources énergétiques locales et la collaboration radio entre les SBSs.Par conséquent, nous avons élaboré un cadre d'optimisation pour le pré-déploiement et le post-déploiement du GSBS, afin de permettre aux MNOs de réduire conjointement leurs dépenses d'électricité et le vieillissement de leurs équipements. L'optimisation pré-déploiement consiste en un dimensionnement du GSBS qui tient compte du vieillissement de la batterie et de la stratégie de gestion des ressources énergétiques. Le problème associé est formulé et le dimensionnement optimal est approché en s'appuyant des profils moyens (production, consommation et prix de l'électricité) à travers une méthode itérative basée sur le solveur non-linéaire “fmincon”. Le schéma de post-déploiement repose sur des capacités d'apprentissage permettant d'ajuster dynamiquement la gestion énergétique du GSBS à son environnement (conditions météorologiques, charge de trafic et coût de l'électricité). La solution s'appuie sur le fuzzy Q-learning qui consiste à combiner le système d'inférence floue avec l'algorithme Q-learning. Ensuite, nous formalisons un système d'équilibrage de charge capable d'étendre la gestion énergétique locale à une collaboration à l'échelle réseau. Nous proposons à ce titre un algorithme en deux étapes, combinant des contrôleurs hiérarchiques au niveau du GSBS et au niveau du réseau. Les deux étapes s'alternent pour continuellement planifier et adapter la gestion de l'énergie à la collaboration radio dans le HetNet.Les résultats de la simulation montrent que, en considérant le vieillissement de la batterie et l'impact mutuel de la conception du système sur la stratégie énergétique (et vice-versa), le dimensionnement optimal du GSBS est capable de maximiser le retour sur investissement. En outre, grâce à ses capacités d'apprentissage, le GSBS peut être déployé de manière plug-and-play, avec la possibilité de s'auto-organiser, d'améliorer le coût énergétique du système et de préserver la durée de vie de la batterie<br>Pushed by an unprecedented increase in data traffic, Mobile Network Operators (MNOs) are densifying their networks through the deployment of Small-cell Base Stations (SBS), low-range radio-access transceivers that offer enhanced capacity and improved coverage. This new infrastructure – Heterogeneous cellular Network (HetNet) -- uses a hierarchy of high-power Macro-cell Base Stations overlaid with several low-power (SBSs).The augmenting deployment and operation of the HetNets raise a new crucial concern regarding their energy consumption and carbon footprint. In this context, the use of energy-harvesting technologies in mobile networks have gained particular interest. The environment-friendly power sources coupled with energy storage capabilities have the potential to reduce the carbon emissions as well as the electricity operating expenditures of MNOs.The integration of renewable energy (solar panel) and energy storage capability (battery) in SBSs gain in efficiency thanks to the technological and economic enablers brought by the Smart Grid (SG). However, the obtained architecture, which we call Green Small-Cell Base Station (GSBS), is complex. First, the multitude of power sources, the system aging, and the dynamic electricity price in the (SG) are factors that require design and management to enable the (GSBS) to efficiently operate. Second, there is a close dependence between the system sizing and control, which requires an approach to address these problems simultaneously. Finally, the achievement of a holistic management in a (HetNet) requires a network-level energy-aware scheme that jointly optimizes the local energy resources and radio collaboration between the SBSs.Accordingly, we have elaborated pre-deployment and post-deployment optimization frameworks for GSBSs that allow the MNOs to jointly reduce their electricity expenses and the equipment degradation. The pre-deployment optimization consists in an effective sizing of the GSBS that accounts for the battery aging and the associated management of the energy resources. The problem is formulated and the optimal sizing is approximated using average profiles, through an iterative method based on the non-linear solver “fmincon”. The post-deployment scheme relies on learning capabilities to dynamically adjust the GSBS energy management to its environment (weather conditions, traffic load, and electricity cost). The solution is based on the fuzzy Q-learning that consists in tuning a fuzzy inference system (which represents the energy arbitrage in the system) with the Q-learning algorithm. Then, we formalize an energy-aware load-balancing scheme to extend the local energy management to a network-level collaboration. We propose a two-stage algorithm to solve the formulated problem by combining hierarchical controllers at the GSBS-level and at the network-level. The two stages are alternated to continuously plan and adapt the energy management to the radio collaboration in the HetNet.Simulation results show that, by considering the battery aging and the impact of the system design and the energy strategy on each other, the optimal sizing of the GSBS is able to maximize the return on investment with respect to the technical and economic conditions of the deployment. Also, thanks to its learning capabilities, the GSBSs can be deployed in a plug-and-play fashion, with the ability to self-organize, improve the operating energy cost of the system, and preserves the battery lifespan

Ce mémoire de maîtrise en histoire a pour objet le mouvement des sans-emploi et le Parti communiste du Canada (PCC) à Montréal au cours de la Grande Dépression (1930-1935). À ce sujet, les historiographies canadienne et québécoise sont lacunaires. Cette recherche a pour objectif de répondre aux questions suivantes : quelles revendications sont portées par le PCC et les sans-travail qui participent au mouvement? Quelles sont leurs stratégies de mobilisation? Quels sont les obstacles auxquels ils sont confrontés? Comment se développent des "cultures de solidarité" au sein du mouvement? Ce mémoire défend l'hypothèse que la Crise, en tant qu'événement-matrice, bouleverse les rapports sociaux et favorise la mobilisation et l'organisation massive des sans-emploi. Cette situation particulière, par son impact sur les structures sociales, économiques et politiques, permet au PCC d'organiser un pan de la classe ouvrière délaissé par ses organisations traditionnelles. À travers leurs combats quotidiens pour la survie et la dignité, les sans-emploi développent des pratiques sociales et culturelles de résistance auxquelles l'État répond par la répression. Cette dynamique permet l'émergence d'une conscience qui se mesure à l'expression de "cultures de solidarité". Cette expérience de classe permet ainsi de dévoiler l'agencéité des sans-travail. Ces événements démontrent que le PCC à Montréal remporte un succès certes relatif, mais plus important que ce qu'en en dit l'historiographie, notamment auprès des sans-emploi.

Le projet SACER vise à répondre aux demandes d'Airbus qui ont besoin de disposer de données décrivant le comportement d'un avion ou d'un satellite avant commercialisation ou lancement. Pour mieux répondre à cette demande, un réseau de capteurs sans fil remplacerait les équipements de test filaires existants. Le but est d'apporter des avantages tels qu'une réduction de poids, de coût et de connectique. Pour notre part, nous n'avons travaillé que sur l'application aéronautique. Pour alimenter les capteurs autonomes sans fil embarqués, dans le cadre de cette thèse, il faut concevoir une architecture de récupération d'énergie, un système de stockage de l'énergie ainsi que un circuit de gestion de ces énergies. La principale contrainte pour le système est qu'il doit pouvoir fonctionner de -50C à 100°C, tout en délivrant une puissance de sortie de 3 watts. De plus, l'épaisseur du système doit être inférieure à 3,2 mm. Pour notre travail, nous avons cherché, dans un premier temps, la meilleure solution possible sur le choix du type de cellules solaires. Le résultat sur les tests des cellules à différentes températures et irradiations dans les conditions de notre application est présenté. Dans un second temps, nous avons testé plusieurs types de systèmes de stockage d'énergie aux températures extrêmes. Enfin, la conception de l'architecture pour la gestion de l'énergie (vue d'ensemble des panneaux photovoltaïques, d'un circuit MPPT, des super condensateurs, et d'un régulateur) est présentée.

Les objets connectés sont des systèmes embarqués communicants, généralement alimentés par des sources d’énergie limitées comme des batteries. Leur durée de vie devient alors une contrainte importante qu’il est nécessaire de prendre en compte dès les premières étapes de leur conception. Dans le contexte de ces travaux de thèse, cette durée de vie est définie comme étant le temps qui s’écoule depuis le démarrage du système jusqu’à l’épuisement de sa source d’alimentation. Nous nous intéressons ici à l’estimation de cette durée de vie lors des phases de conception amont. Une étude de l’état de l’art nous a montré que les solutions d’estimation proposées par la communauté scientifique ne sont pas assez précises. Aussi, afin de remédier à ce manque de précision, nous présentons une méthode permettant d’estimer cette durée de vie dans le cas d’application des réseaux de capteurs sans fils. Cette méthode prend en considération trois aspects fondamentaux, à savoir, l’application logicielle embarquée sur le nœud de capteur, sa plateforme matérielle et la batterie qui l’alimente. Cette méthode a été implémentée sous la forme d’un environnement (framework) pour le simulateur de réseaux à évènement discret OMNeT++. Nous avons évalué la précision et les performances de simulation de notre méthode. Par ailleurs, dans le cadre d’une collaboration scientifique avec le SICS (Suède) notre méthode a été appliquée à l’étude d’un réseau de capteurs composé de 25 nœuds exploitant la plateforme matérielle T-Mote Sky, le protocole de communication 6LowPan et le système d’exploitation ContikiOS. Lors de cette étude, nous avons étendu la durée de vie du réseau de quelque mois à plus d’une année. Enfin, nous avons confronté nos résultats de simulation à des mesures expérimentales. L’erreur moyenne absolue obtenue, tous modèles confondus, est comprise entre 6,17% et 11,56% de la durée de vie totale. En comparaison, les méthodes de l’état de l’art ont une erreur d’estimation supérieure à 35%. Soulignons que tous nos résultats de simulation ont été obtenus avec des modèles établis à partir des données disponibles dans les documentations techniques et qu’aucune calibration n’a été nécessaire<br>Connected devices are embedded electronic systems that are powered by batteries. Their lifetime is an important constraint to take into account at very early design stages. In the context of this work, the lifetime is defined as being the time elapsed from the device very first boot until its battery does not contain enough energy to supply it. Thus, in this work, we investigate lifetime estimation in early design stages. A deep state-of-the-art's study showed that existing solutions were not accurate enough to do such estimation. Therefore, we introduce an original method oriented toward lifetime estimation in order to address this limitation. Our method relies on three fundamental aspects that are the software running on the device, its hardware platform and the battery that supplies it. This method has been implemented as a framework for the OMNeT++ network simulator. We evaluate the simulation performances of our implementation as well as the precision of our method. Moreover, in the context of a scientific collaboration with the SICS (Sweden), this method has been applied to a case study that implies several TMote Sky nodes running ContikiOS with a RPL/6LowPan communication's stack. Actually, our method gave us access to useful insights. These latter were used to improve the lifetime from 4 months to more than a year. We also compare our method’s simulation results to real experiment's measures. The absolute mean error is going from 6.17% to 11.56% depending on the model. In comparison, the state-of-the-art methods/solutions lead to an error that is greater than 35% - which highlights their inaccuracies. We also need to mention that the models that we have designed in our method were built using only the technical specifications and do not require any calibration

Les systèmes embarqués tels que les téléphones portables ou les lecteurs multimédia intègrent de plus en plus de fonctions consommatrices d'énergie ce qui a pour conséquence directe une diminution de leurs autonomies. Les applications audio dans les téléphones cellulaires et en particulier l'application casque font partie des fonctions les plus consommatrices d'énergie. Après un état de l'art des solutions permettant l'amplification de signaux audio, l'amplificateur de classe G à été identifié comme étant le meilleur candidat pour obtenir une amélioration du rendement tout en fournissant une bonne qualité de reproduction sonore. Nos travaux se sont plus particulièrement focalisés sur la détection d'enveloppe de ces architectures qui est un facteur clé dans la maximisation du rendement. Une étude des propriétés temporelles, fréquentielles et statistiques des signaux présents en entrée de l'amplificateur a ainsi été menée pour mettre en évidence les différences entre les signaux classiquement utilisés (signal sinusoïdal) et les signaux réellement écoutés par les utilisateurs (musique). Après avoir effectué une sélection de signaux pour la suite de notre étude, nous avons également caractérisé la puissance correspondant à des conditions normales d'écoute afin d'obtenir par la suite un environnement de test proche des conditions réelles de fonctionnement. Un modèle simplifié et rapide d'amplificateur hybride permettant d'obtenir en quelques dizaines de secondes, l'évaluation du rendement, de la consommation et de la qualité sonore dans des conditions réelles de fonctionnement a été développé. Notre modèle, entièrement configurable et réadaptable à d'autres types de circuits a été validé par mesures pratiques des performances d'un amplificateur existant. Les paramètres de la détection d'enveloppe de ce modèle ont fait l'objet d'une optimisation basée sur le couplage séquentiel de deux algorithmes d'optimisation, permettant ainsi dans un temps limité d'obtenir une solution optimale sans solution de départ sous des conditions réelles d'utilisation. La suite de notre étude nous a conduit à étudier, modéliser, optimiser et comparer des amplificateurs de classe G possédant un nombre de tensions d'alimentation supérieur (3, 4) ainsi que des amplificateurs de classe H (alimentations continues) afin d'améliorer encore le rendement. Enfin, nous avons proposé une nouvelle détection d'enveloppe permettant d'améliorer le rendement à faible puissance. Cette nouvelle détection d'enveloppe permet à l'amplificateur de classe G un fonctionnement en " multi niveau " et d'être auto adaptatif au signal audio présent en entrée de l'amplificateur. Après avoir développé des méta-modèles pour optimiser les paramètres de la détection d'enveloppe, cette détection d'enveloppe a été implémentée au niveau transistor en technologie 0.25μm de ST Microelectronics.

Energy is a basic necessity shared by all living things on the planet, much like water, food, and shelter. The main source of producing usable kinds of energy is fossil fuels. In light of this, the main cause of ozone depletion and global-warming are the fossil fuels. The search for energy sources that are independent of fossil fuels and have a smaller impact on global warming has been reignited by the recent rise in awareness of it. Renewable-Energy Sources (RES) like wind and solar and hydropower are more accessible when compared to fossil fuel alternatives. It is appropriate to use thermal energy from the sun for both heating purpose and cooling purpose. Low temperature heating processes like household heating of water, household and industrial heating of areas and spaces, heating of swimming pool, ventilation operations, and some manufacturing processes and industrial processes are among the main applications for solar technologies. This research aims to investigate the possibility of using Indian desert sand as a material for energy storage in a high-temperature TESs. Sand has the potential to be a novel and environmentally friendly storage medium with low maintenance and operating costs. The Thermal Energy Storage Element will store thermally charged sand. It will need to be stored for a particular amount of time after achieving the right temperature in the sand to assess its efficiency. The remaining heat will then be released and absorbed by the oil, and it will employ a Peltier Element to produce electricity. The experiments are divided into three sections : Charging Phase, Storing Phase, and Discharging Phase, but the simulation has been performed only for the charging part. Certain design constraints are addressed, as well as several methods for improving system functionality for future optimization.

The present thesis deals with the beneficial influence of nanostructuring on electrochemical performance of certain promising electrode and electrolyte materials for lithium-ion batteries (LIBs). Electrochemical performances of chosen electrodes and electrolytes have been presented in a systematic and detailed manner via studies related to both transport and lithium storage. Titanium dioxide (TiO2) or titania, a promising non-carbonaceous anode material for LIBs was chosen for the study. As part of the study, variety of nanostructured titania were synthesized. In general, all materials exhibited high lithium storage ( theoretical value for lithium storage in titania) and some of them showed exemplary rate capability, typically desired for modern lithium-ion batteries. Studies related to performance of these materials and mechanistics of lithium storage and kinetics are presented in Chapters 2-5. “Soggy sand” electrolyte, a promising soft matter electrolyte for LIBs was studied on the electrolyte side. Ion transport, mechanical strength and electrochemical properties of “soggy sand” electrolytes synthesized via dispersion of various surface chemically functionalized silica particles dispersed in model as well as LIB relevant electrolytes were studied in this thesis. Extensive physico-chemical and battery performance studies of “soggy sand” electrolytes are discussed in Chapters 6-8. A brief discussion of the contents and highlights of the individual chapters are described below: Chapter 1 briefly discusses the importance of electrochemical power sources as a viable green alternative to the combustion engine. Various facets of rechargeable LIBs, one of the most important electrochemical storage devices, are presented following the general discussion on electrochemical power devices. The importance of nanostructuring of electrodes with special emphasis on anodes for high lithium storage capacities and rate capabilities are also discussed in the opening chapter. The various advantages and disadvantages of the most commonly used electrolytes in LIB i.e. the liquid electrolytes are also discussed in Chapter 1. Suggestions for improvement of the physico-chemical properties of liquid electrolytes especially via nanostructuring (demonstrated via dispersions of fine oxide particles in liquid electrolytes in Chapters 6-8) using the concept of Heterogeneous doping are discussed in detail. A brief description on the importance of rheology for comprehension of soft matter microstructure is also provided in this chapter. Chapter 2 discusses composite of anatase titania (TiO2) nanospheres and carbon grown and self-assembled into micron-sized mesoporous spheres via a solvothermal synthesis route as prospective anode for rechargeable lithium-ion battery. The morphology and carbon content and hence the electrochemical performance are observed to be significantly influenced by the synthesis parameters. Synthesis conditions resulting in a mesoporous arrangement of an optimized amount of carbon and TiO2 exhibited the best lithium battery performance. The first discharge cycle capacity of carbon-titania mesoporous spheres (solvothermal reaction at 150 oC at 6 h, calcination at 500 oC under air, BET surface area 80 m2g-1) was 334 mAhg-1 (approximately 1 Li) at current rate of 66 mAg-1. High storage capacity and good cyclability is attributed to the nanostructuring (i.e. mesoporosity) of TiO2 as well as due to formation of a percolation network of carbon around the TiO2 nanoparticles. The micron-sized mesoporous spheres of carbon-titania composite nanoparticles also show good rate cyclability in the range (0.066-6.67) Ag-1. The electrochemical performance of the mesoporous carbon-TiO2 spheres has been compared with nonporous TiO2 spheres, normal mesoporous TiO2 and bulk TiO2. Implications of nanostructuring and conductive carbon interface on lithium insertion/removal capacity and insertion kinetics in nanoparticles of anatase polymorph of titania is discussed in Chapter 3. Sol-gel synthesized nanoparticles of titania (particle size ~ 6 nm) were hydrothermally coated ex situ with a thin layer of amorphous carbon (layer thickness: 2-5 nm) and calcined at a temperature much higher than the sol-gel synthesis temperature. The carbon-titania composite particles (resulting size  10 nm) displayed immensely superior cyclability and rate capability (higher current rates  4 Ag-1) compared to unmodified calcined anatase titania. The conductive carbon interface around titania nanocrystals enhances the electronic conductivity and inhibits crystallite growth during electrochemical insertion/removal thus preventing detrimental kinetic effects observed in case of un-modified anatase titania. The carbon coating of the nanoparticles also stabilized the titania crystallographic structure via reduction in the accessibility of lithium ions to the trapping sites. This resulted in decrease in the irreversible capacity observed in case of nanoparticles without any carbon coating. Chapter 4 discusses the morphology and electrochemical performance of mixed crystallographic phase titania nanotubes and nanosheets for prospective application as anode in rechargeable lithium-ion batteries. Hydrothermally grown nanotubes/nanosheets of titania (TiO2) and carbon/silver-titania (C/Ag-TiO2) comprise a mixture of both anatase and TiO2(B) crystallographic phases. The first cycle capacity (at current rate = 10 mAg-1) for bare TiO2 nanotubes was 355 mAhg-1 (approximately 1.06 Li), which is higher than both the theoretical capacity (335 mAhg-1) as well as reported values for pure anatase and TiO2(B) nanotubes. Higher capacity is attributed to a combination of presence of mixed crystallographic phases of titania as well as trivial size effects. The surface area of bare TiO2 nanotubes was very high being equal to 340 m2g-1. Surface modification of the TiO2 nanotubes via amorphous carbon and Ag nanoparticles resulted in significant improvement in battery performance. The first cycle irreversible capacity loss can be minimized via effective coating of the surface. Carbon coated TiO2 nanotubes showed superior performance than Ag nanoparticle coated TiO2 nanotubes in terms of long term cyclability. Unlike Ag nanoparticles which are randomly distributed over the TiO2 nanotubes, the effective homogeneous carbon coating forms an efficient percolation network for the conducting species thus exhibiting better battery performance. The C-TiO2 and Ag-TiO2 nanotubes showed a better rate capability i.e. higher capacities compared to bare TiO2 nanotubes in the current range 0.055-2 Ag-1. Although titania nanosheets retains mixed crystallographic phases, the lithium battery performance (first cycle capacity = 225 mAhg-1) is poor compared to TiO2 nanotubes. It is attributed to lower surface area (22 m2g-1) which resulted in lesser electrode/electrolyte contact area and inefficient transport pathways for Li+ and e-. Implications of iron on electrochemical lithium insertion/removal capacity of iron (Fe3+) doped anatase TiO2 is discussed in Chapter 5. Iron doped anatase TiO2 nanoparticles with different doping concentrations were synthesized by simple sol-gel method. The electrochemistry of anatase TiO2 is observed to be a strong function of concentration of iron (Fe3+). A high 1st cycle discharge capacity of 704 mAhg−1 (2.1 mol of Li) and 272 mAhg−1 (0.81 mol of Li) at the 30th discharge cycle with Coulombic efficiency greater than 96% has been observed for 5% iron (Fe3+) doped TiO2 at a current density of 75 mAg−1. Additional increase in the iron (Fe3+) concentrations deteriorates the lithium storage of TiO2. An improvement in lithium storage of more than 50% is noticed for 5% iron (Fe3+) doped TiO2 compared to pure anatase TiO2 which shows an initial discharge capacity of 279 mAhg−1. The anomalous lithium storage behavior in all the iron (Fe3+) doped TiO2 has been accounted, in addition to homogeneous Li insertion in the octahedral sites, on the basis of formation of metallic Fe and Li2O during initial lithiation process and subsequent heterogeneous interfacial storage between Fe and Li2O interface. Chapter 6 discusses in a systematic manner the crucial role of oxide surface chemical composition on ion transport in “soggy sand” electrolytes. A “soggy sand” electrolytic system comprising of aerosil silica functionalized with various hydrophilic and hydrophobic moeities dispersed in lithium perchlorate ethylene glycol solution ( = 37.7) was used for the study. Detailed rheology studies show that the attractive particle network in case of the composite with unmodified aerosil silica (with surface silanol groups) is most favorable for percolation in ionic conductivity as well as rendering the composite with beneficial elastic mechanical properties. Though weaker in strength compared to the composite with unmodified aerosil particles, attractive particle networks are also observed in composites of aerosil particles with surfaces partially substituted with hydrophobic groups. However, ionic conductivity is observed to be dependent on the size of the hydrophobic moiety. No spanning attractive particle network was formed for aerosil particles with surfaces modified with stronger hydrophilic groups (than silanol) and as a result no percolation in ionic conductivity was observed. The composite with hydrophilic particles was a sol contrary to gels obtained in case of unmodified aerosil and partially substituted with hydrophobic groups. Chapter 7 also discusses the influence of oxide surface chemical composition but additionally the role of solvent on ion solvation and ion transport of “soggy sand” electrolytes. Compared to the liquid electrolyte in Chapter 6, a lower dielectric constant liquid electrolyte was employed for the study in this chapter. A “soggy sand” electrolyte system comprising of dispersions of hydrophilic/hydrophobic functionalized aerosil silica in lithium perchlorate-methoxy polyethylene glycol solution ( = 10.9) was employed for the study. Static and dynamic rheology measurements again showed formation of an attractive particle network in case of the composite with unmodified aerosil silica (i.e. with surface silanol groups) as well as composites with hydrophobic alkane groups. While particle network in the composite with hydrophilic aerosil silica (unmodified) were due to hydrogen bonding, hydrophobic aerosil silica particles were held together via van der Waals forces. The network strength in the latter case (i.e. for hydrophobic composites) were weaker compared with the composite with unmodified aerosil silica. Both unmodified silica as well as hydrophobic silica composites displayed solid-like mechanical strength. However, this time around no enhancement in ionic conductivity compared to the liquid electrolyte was observed in case of the unmodified silica. This is attributed to the existence of a very strong particle network which leads to the “expulsion” of all conducting entities from the interfacial region between adjacent particles. The ionic conductivity for composites with hydrophobic aerosil particles displayed ionic conductivity as a function of the size of the hydrophobic chemical moiety. No spanning attractive particle network was observed for aerosil particles with surfaces modified with stronger hydrophilic groups (than silanol). The composite resembled a sol and no percolation in ionic conductivity was observed. Chapter 8 describes the influence of dispersion of uniformly sized mono-functional or bi-functional (“Janus”) particles on ionic conductivity in lithium battery solutions and it’s implications on battery performance. Mono-functionalized (hydrophilic or hydrophobic) and bi-functionalized Janus (hydrophilic and hydrophobic) particles form physical gels of varying strength over a wide range of concentration (0.1    0.4; , oxide volume fraction). While the composites with mono-functionalized particles display shear thinning typical of gels (due to gradual breaking up spanning particle network held together by hydrogen/van der Walls force), the bi-functionalized “Janus” particles exhibit both complementary properties of gel and sol. The latter observation is interpreted in terms of existence of both hydrogen and van der Waals force arising out of the particle arrangement which get perturbed under the influence of external shear. Composites with homogeneous hydrophilic surface group show the highest ionic conductivity whereas the homogeneous hydrophobic surfaces exhibit superior electrode/electrolyte interface stability and battery cyclability. The Janus particles did not show any enhancement in ionic conductivity however, battery performance is highly satisfactory taking intermediate values between the homogeneously functionalized hydrophilic and hydrophobic particle composites.

The present thesis deals with the beneficial influence of nanostructuring on electrochemical performance of certain promising electrode and electrolyte materials for lithium-ion batteries (LIBs). Electrochemical performances of chosen electrodes and electrolytes have been presented in a systematic and detailed manner via studies related to both transport and lithium storage. Titanium dioxide (TiO2) or titania, a promising non-carbonaceous anode material for LIBs was chosen for the study. As part of the study, variety of nanostructured titania were synthesized. In general, all materials exhibited high lithium storage ( theoretical value for lithium storage in titania) and some of them showed exemplary rate capability, typically desired for modern lithium-ion batteries. Studies related to performance of these materials and mechanistics of lithium storage and kinetics are presented in Chapters 2-5. “Soggy sand” electrolyte, a promising soft matter electrolyte for LIBs was studied on the electrolyte side. Ion transport, mechanical strength and electrochemical properties of “soggy sand” electrolytes synthesized via dispersion of various surface chemically functionalized silica particles dispersed in model as well as LIB relevant electrolytes were studied in this thesis. Extensive physico-chemical and battery performance studies of “soggy sand” electrolytes are discussed in Chapters 6-8. A brief discussion of the contents and highlights of the individual chapters are described below: Chapter 1 briefly discusses the importance of electrochemical power sources as a viable green alternative to the combustion engine. Various facets of rechargeable LIBs, one of the most important electrochemical storage devices, are presented following the general discussion on electrochemical power devices. The importance of nanostructuring of electrodes with special emphasis on anodes for high lithium storage capacities and rate capabilities are also discussed in the opening chapter. The various advantages and disadvantages of the most commonly used electrolytes in LIB i.e. the liquid electrolytes are also discussed in Chapter 1. Suggestions for improvement of the physico-chemical properties of liquid electrolytes especially via nanostructuring (demonstrated via dispersions of fine oxide particles in liquid electrolytes in Chapters 6-8) using the concept of Heterogeneous doping are discussed in detail. A brief description on the importance of rheology for comprehension of soft matter microstructure is also provided in this chapter. Chapter 2 discusses composite of anatase titania (TiO2) nanospheres and carbon grown and self-assembled into micron-sized mesoporous spheres via a solvothermal synthesis route as prospective anode for rechargeable lithium-ion battery. The morphology and carbon content and hence the electrochemical performance are observed to be significantly influenced by the synthesis parameters. Synthesis conditions resulting in a mesoporous arrangement of an optimized amount of carbon and TiO2 exhibited the best lithium battery performance. The first discharge cycle capacity of carbon-titania mesoporous spheres (solvothermal reaction at 150 oC at 6 h, calcination at 500 oC under air, BET surface area 80 m2g-1) was 334 mAhg-1 (approximately 1 Li) at current rate of 66 mAg-1. High storage capacity and good cyclability is attributed to the nanostructuring (i.e. mesoporosity) of TiO2 as well as due to formation of a percolation network of carbon around the TiO2 nanoparticles. The micron-sized mesoporous spheres of carbon-titania composite nanoparticles also show good rate cyclability in the range (0.066-6.67) Ag-1. The electrochemical performance of the mesoporous carbon-TiO2 spheres has been compared with nonporous TiO2 spheres, normal mesoporous TiO2 and bulk TiO2. Implications of nanostructuring and conductive carbon interface on lithium insertion/removal capacity and insertion kinetics in nanoparticles of anatase polymorph of titania is discussed in Chapter 3. Sol-gel synthesized nanoparticles of titania (particle size ~ 6 nm) were hydrothermally coated ex situ with a thin layer of amorphous carbon (layer thickness: 2-5 nm) and calcined at a temperature much higher than the sol-gel synthesis temperature. The carbon-titania composite particles (resulting size  10 nm) displayed immensely superior cyclability and rate capability (higher current rates  4 Ag-1) compared to unmodified calcined anatase titania. The conductive carbon interface around titania nanocrystals enhances the electronic conductivity and inhibits crystallite growth during electrochemical insertion/removal thus preventing detrimental kinetic effects observed in case of un-modified anatase titania. The carbon coating of the nanoparticles also stabilized the titania crystallographic structure via reduction in the accessibility of lithium ions to the trapping sites. This resulted in decrease in the irreversible capacity observed in case of nanoparticles without any carbon coating. Chapter 4 discusses the morphology and electrochemical performance of mixed crystallographic phase titania nanotubes and nanosheets for prospective application as anode in rechargeable lithium-ion batteries. Hydrothermally grown nanotubes/nanosheets of titania (TiO2) and carbon/silver-titania (C/Ag-TiO2) comprise a mixture of both anatase and TiO2(B) crystallographic phases. The first cycle capacity (at current rate = 10 mAg-1) for bare TiO2 nanotubes was 355 mAhg-1 (approximately 1.06 Li), which is higher than both the theoretical capacity (335 mAhg-1) as well as reported values for pure anatase and TiO2(B) nanotubes. Higher capacity is attributed to a combination of presence of mixed crystallographic phases of titania as well as trivial size effects. The surface area of bare TiO2 nanotubes was very high being equal to 340 m2g-1. Surface modification of the TiO2 nanotubes via amorphous carbon and Ag nanoparticles resulted in significant improvement in battery performance. The first cycle irreversible capacity loss can be minimized via effective coating of the surface. Carbon coated TiO2 nanotubes showed superior performance than Ag nanoparticle coated TiO2 nanotubes in terms of long term cyclability. Unlike Ag nanoparticles which are randomly distributed over the TiO2 nanotubes, the effective homogeneous carbon coating forms an efficient percolation network for the conducting species thus exhibiting better battery performance. The C-TiO2 and Ag-TiO2 nanotubes showed a better rate capability i.e. higher capacities compared to bare TiO2 nanotubes in the current range 0.055-2 Ag-1. Although titania nanosheets retains mixed crystallographic phases, the lithium battery performance (first cycle capacity = 225 mAhg-1) is poor compared to TiO2 nanotubes. It is attributed to lower surface area (22 m2g-1) which resulted in lesser electrode/electrolyte contact area and inefficient transport pathways for Li+ and e-. Implications of iron on electrochemical lithium insertion/removal capacity of iron (Fe3+) doped anatase TiO2 is discussed in Chapter 5. Iron doped anatase TiO2 nanoparticles with different doping concentrations were synthesized by simple sol-gel method. The electrochemistry of anatase TiO2 is observed to be a strong function of concentration of iron (Fe3+). A high 1st cycle discharge capacity of 704 mAhg−1 (2.1 mol of Li) and 272 mAhg−1 (0.81 mol of Li) at the 30th discharge cycle with Coulombic efficiency greater than 96% has been observed for 5% iron (Fe3+) doped TiO2 at a current density of 75 mAg−1. Additional increase in the iron (Fe3+) concentrations deteriorates the lithium storage of TiO2. An improvement in lithium storage of more than 50% is noticed for 5% iron (Fe3+) doped TiO2 compared to pure anatase TiO2 which shows an initial discharge capacity of 279 mAhg−1. The anomalous lithium storage behavior in all the iron (Fe3+) doped TiO2 has been accounted, in addition to homogeneous Li insertion in the octahedral sites, on the basis of formation of metallic Fe and Li2O during initial lithiation process and subsequent heterogeneous interfacial storage between Fe and Li2O interface. Chapter 6 discusses in a systematic manner the crucial role of oxide surface chemical composition on ion transport in “soggy sand” electrolytes. A “soggy sand” electrolytic system comprising of aerosil silica functionalized with various hydrophilic and hydrophobic moeities dispersed in lithium perchlorate ethylene glycol solution ( = 37.7) was used for the study. Detailed rheology studies show that the attractive particle network in case of the composite with unmodified aerosil silica (with surface silanol groups) is most favorable for percolation in ionic conductivity as well as rendering the composite with beneficial elastic mechanical properties. Though weaker in strength compared to the composite with unmodified aerosil particles, attractive particle networks are also observed in composites of aerosil particles with surfaces partially substituted with hydrophobic groups. However, ionic conductivity is observed to be dependent on the size of the hydrophobic moiety. No spanning attractive particle network was formed for aerosil particles with surfaces modified with stronger hydrophilic groups (than silanol) and as a result no percolation in ionic conductivity was observed. The composite with hydrophilic particles was a sol contrary to gels obtained in case of unmodified aerosil and partially substituted with hydrophobic groups. Chapter 7 also discusses the influence of oxide surface chemical composition but additionally the role of solvent on ion solvation and ion transport of “soggy sand” electrolytes. Compared to the liquid electrolyte in Chapter 6, a lower dielectric constant liquid electrolyte was employed for the study in this chapter. A “soggy sand” electrolyte system comprising of dispersions of hydrophilic/hydrophobic functionalized aerosil silica in lithium perchlorate-methoxy polyethylene glycol solution ( = 10.9) was employed for the study. Static and dynamic rheology measurements again showed formation of an attractive particle network in case of the composite with unmodified aerosil silica (i.e. with surface silanol groups) as well as composites with hydrophobic alkane groups. While particle network in the composite with hydrophilic aerosil silica (unmodified) were due to hydrogen bonding, hydrophobic aerosil silica particles were held together via van der Waals forces. The network strength in the latter case (i.e. for hydrophobic composites) were weaker compared with the composite with unmodified aerosil silica. Both unmodified silica as well as hydrophobic silica composites displayed solid-like mechanical strength. However, this time around no enhancement in ionic conductivity compared to the liquid electrolyte was observed in case of the unmodified silica. This is attributed to the existence of a very strong particle network which leads to the “expulsion” of all conducting entities from the interfacial region between adjacent particles. The ionic conductivity for composites with hydrophobic aerosil particles displayed ionic conductivity as a function of the size of the hydrophobic chemical moiety. No spanning attractive particle network was observed for aerosil particles with surfaces modified with stronger hydrophilic groups (than silanol). The composite resembled a sol and no percolation in ionic conductivity was observed. Chapter 8 describes the influence of dispersion of uniformly sized mono-functional or bi-functional (“Janus”) particles on ionic conductivity in lithium battery solutions and it’s implications on battery performance. Mono-functionalized (hydrophilic or hydrophobic) and bi-functionalized Janus (hydrophilic and hydrophobic) particles form physical gels of varying strength over a wide range of concentration (0.1    0.4; , oxide volume fraction). While the composites with mono-functionalized particles display shear thinning typical of gels (due to gradual breaking up spanning particle network held together by hydrogen/van der Walls force), the bi-functionalized “Janus” particles exhibit both complementary properties of gel and sol. The latter observation is interpreted in terms of existence of both hydrogen and van der Waals force arising out of the particle arrangement which get perturbed under the influence of external shear. Composites with homogeneous hydrophilic surface group show the highest ionic conductivity whereas the homogeneous hydrophobic surfaces exhibit superior electrode/electrolyte interface stability and battery cyclability. The Janus particles did not show any enhancement in ionic conductivity however, battery performance is highly satisfactory taking intermediate values between the homogeneously functionalized hydrophilic and hydrophobic particle composites.

Pile foundations are usually recommended when soil capacity is not sufficient for the expected loads of the structure with conventional foundation techniques. While the case . of vertical piles is reasonably documented in the literature, the case of batter piles in sand has received little attention from the researchers. This is mainly due to the complexity of modeling the earth pressure distribution around the pile's shaft. Attempts were made to model the pullout behavior of vertical piles numerically using two-dimensional approaches, which does not represent the field condition and accordingly the results are scattering. In this study a 3D numerical model was developed to investigate the uplift capacity of single batter piles in sand. The model utilizes the powerful software "ABAQUS" version 6.6, which is capable to model such complex interaction in three-dimensional stress analysis. The model was validated with the prototype test results of Hanna and Afram (1986) and field work of Alewnah (1999) Design procedure and design charts have been presented to assist foundation engineers to predict the uplift capacity of batter piles in sand.