One of the key points to reduce the world dependence on fossil fuels and the emissions of greenhouse gases is the use of renewable energy sources. Recent studies showed that wind energy is a significant source of renewable energy which is capable to meet the global energy demands. However, such energy cannot be harvested by today’s technology, based on wind towers, which has nearly reached its economical and technological limits. The major part of the atmospheric wind is inaccessible to the conventional wind turbines and wind at higher altitude is the major source of potential energy which has not been fully exploited yet. The thesis paper has presented a study aimed to devise a new class of wind generator based on extracting energy from high altitude wind.A brief theoretical study is presented to evaluate the potential of an innovative high altitude wind power technology which exploits a tethered airfoil to extract energy from wind at higher altitude. Among the various concepts proposed over last few decades, a kite power system with a single kite is selected for the design purpose.The designed ground station is an improvisation over existing prototypes with an energy reservoir for having a continuous power output. A flywheel is used as the energy storage system which stores the extra energy during traction phases and supplies it during recovery phases and thus giving a continuous power generation regardless of the kite’s motion and keeping the rotor speed in a permissible range defined by the design constraints. Manufacturability of the structure, availability of the components, safety and maintenance criteria have been taken into account while building the ground station CAD model.A dynamic simulation model is developed to investigate the power transmission system of the kite power unit which reflects the torque, speed and power behaviour of the modelled ground station driveline. The functionality of the designed model for the selected concept is tested with several numerical and graphical examples.

La thèse porte sur l'étude de générateurs utilisant un cerf-volant pour capter l'énergie éolienne. Ces systèmes permettent de générer de l'énergie éolienne sans avoir besoin de construire les pylônes et les fondations étant nécessaires pour construire une éoliennes classiques.Ces systèmes on commencé à être étudiés il y a une dizaine d'années, une vingtaine d'entreprises et à peu près autant d'universités étudient le problème. Il existe plusieurs types de générateurs étudiés mais jusqu'ici, aucun système n'a démontré que son concept est économiquement viable.La grande variété de systèmes étant étudiés fait penser aux débuts de l'aviation, ou toutes sortes de concepts ont été testés. Il a fallu environ 50 ans de développements de prototypes entre 1870 et 1910 pour que le principe de fonctionnement des avions se standardise autour de celui qui est est encore utilisé aujourd'hui. Pendant cette période, un grand nombre de concepts ont été testés et beaucoup d'erreurs ont étés faites au niveau de la conception du modèle, des techniques expérimentales utilisées et du management des projet.Les systèmes étudiés de génération d'énergie utilisant des cerf-volants tentent répondre à un même cahier des charges d'une vingtaine de façons différentes. Ceci fait penser que le concept de génération d'énergie n'a pas trouvé un principe de fonctionnement optimal et qu'il n'en est qu'à une phase de prospection de concepts.En cela, le récent essor des générateurs cerf-volants ressemble beaucoup au débuts de l'aviation. Nous avons donc cherché à comprendre les erreurs ayant été faites lors des débuts de l'aviation pour essayer de mieux comprendre les erreurs qui pourraient être faites avec les systèmes de générateurs cerf-volants.Cette étude a permis de fixer quelques règles de travail qui ont servi pour développer les prototypes mis au point pendant de thèse.Une soufflerie à été construite pour tester dans des environnements restreints plusieurs modèles de cerf-volants. Plusieurs objectifs ont été atteints pendant la thèse, entre autres le contrôle de la puissance générée par un cerf-volant volant en présence de rafales de vent et l'étude d'un plan de vol permettant au cerf-volant de rester en vol sans vent et sans utiliser d'énergie embarquée.Au total, 13 prototypes ont été mis au point pendant cette thèse, un brevet est en cours de dépôt et une entreprise utilisant les résultats de la thèse est en train d'être créée. / The PhD focuses on the study of electric generators using a kite to capture wind energy. These systems generate wind energy without having to build the towers and foundations are needed to build conventional wind turbines.These systems started being studied around ten years ago, twenty companies and nearly as many universities are studying the problem. There are several types of generators studied, but so far, none has demonstrated that the concept is economically viable.The variety of systems being studied is reminiscent of early aviation, because many kinds of different concepts were tested. It took about 50 years of development of prototypes between 1870 and 1910 for the principle of operation of aircraft got standardized around one that is still used today. During this period, a large number of concepts have been tested and many mistakes have made ​​on the model design, the experimental techniques and on the management of the project.The nowadays studied kite power systems tries to answer to the same specifications by around twenty different ways. This suggests that the concept of power generation has not yet found an optimal principle of functioning and that it is only at a phase of concepts exploration.The recent surge of kite power systems reminds of the early days of aviation. We sought to understand the mistakes that were made ​​during the early days of aviation to try to understand the mistakes that could be made with modern kite power systems.This study has set some guidelines that were used for developing the prototypes built during thesis .A wind tunnel was built for testing in simplified environments several models of kites. Several objectives were achieved during the thesis, including the control of the power generated by a kite flying in the presence of wind gusts and the study of a flight plan allowing the kite to stay in flight without wind and without the use of embedded energy.A total of 13 prototypes were developed during this thesis, a patent is being filed and a company using the results of the thesis is being created.

Airborne Wind Energy is an emerging technology that harnesses the power of the wind by using tethered wings. Among the flying devices are ram-air wings made from coated textiles that utilize dynamic pressure to gain their shape. During flight operation, the textiles are subject to long-term weathering exposure and high aerodynamic loads, leading to degradation processes and the ultimate loss of functional properties. Therefore, a key challenge in the Airborne Wind Energy industry is the improvement of the textile durability of ram-air kites. This thesis contributes to solving this problem by investigating the effects of 200 hours of artificial weathering and 36 weeks of natural weathering on the mechanical properties of selected state-of-the-art kite textiles and the underlying principles of degradation. The tested materials involve two polyamide 6.6 rip-stop weaves coated with polyurethane and silicone, as well as a coated plain weave and a flexible laminate made from high-modulus polyethylene. The results show that all materials are clearly affected by the exposure to weathering, but the implications on the mechanical properties and the rate of degradation vary significantly. The high-modulus polyethylene textiles demonstrate superior tensile properties, but severe coating degradation causes a significant rise in air permeability. Consequently, the high-modulus polyethylene textiles are considered unsuitable for application in ram-air kites, as the high permeability prevents the kite from maintaining sufficiently high pressure. In contrast, the silicone coated polyamide 6.6 textile exhibits superior air permeability after long-term exposure to weathering conditions. FTIR spectroscopy and TGA indicate that the reduced permeability could arise from curing processes in the silicone coating.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on October 9, 2007) Vita. Includes bibliographical references.

Les énergies renouvelables représentent aujourd'hui un domaine de développement de plus en plus important, au vu de la consommation énergétique mondiale et de ses conséquences désastreuses sur l'environnement. Les différents accords politiques, notamment l'accord de Paris, ne peuvent à eux seuls apporter une solution définitive au changement climatique actuel. Les contraintes imposées par la réduction des émissions de CO_2 et l’augmentation du prix du pétrole dans l’industrie maritime ont poussé Yves Parlier à lancer le projet « beyond the sea » dans le but de développer des cerfs-volants (kites) dédiés à la propulsion auxiliaire des navires. L'objectif principal de cette étude est donc la modélisation et la commande robuste d'une aile de kite en vol dynamique. Le but à terme étant l'élaboration d'un pilote automatique dédié à la traction d'un navire par kite. Un modèle « point-masse » du kite est proposé afin de comprendre et contrôler sa dynamique. Les différents paramètres du modèle sont estimés à partir de données expérimentales obtenues lors d’essais en conditions réelles. Des simulations en boucle ouverte sont proposées afin de valider la cohérence du modèle. Pour effectuer un vol dynamique, une trajectoire en forme de huit est définie dans la fenêtre de vol. La position, la taille et l’orientation de cette trajectoire sont des paramètres ajustables par l’utilisateur. Un algorithme de suivi de trajectoire est développé permettant ensuite de synthétiser une loi de commande robuste intégrant le modèle du kite. Ce pilote automatique permet donc d’effectuer une grande variété de trajectoires pour toute une gamme de vitesses de vent. Enfin, des simulations en boucle fermée montrant les performances théoriques du système mettent en évidence l’intérêt de la propulsion auxiliaire des navires par kite. / The need in reducing the CO_2 emissions and the increase of oil prices affect all transportation industries and especially the maritime industry. This has led to the search for more energy-saving ship propulsion systems. Taking advantage of wind energy by using tethered wings, or kites, as an alternative propulsion source can be an effective solution. The "beyond the sea" project, led by Yves Parlier, aims to provide ships an alternative green energy source. In most wind conditions, compared to a static flight, a dynamic motion of a tethered wing with an eight-shaped pattern can provide sufficient force through traction to tow a ship. Therefore, the main objective of this study is the modeling and robust control of a tethered kite in dynamic flight. To this end, a point mass model is first used to describe the kite dynamics. The model parameters are estimated from experimental data and the aerodynamic coefficients are identified using data from a quasi-static flight. Open loop simulations are conducted to verify the kite behavior and the overall coherence of the model. To ensure a dynamic flight, an eight-shaped trajectory is defined within the wind window. Its position, size, orientation and direction are all adjustable parameters. A path-following strategy is then developed in order to design a robust control law including the kite model. This allows the system to be used in different trajectories with a wide range of wind speeds. Closed-loop simulations are presented to show the efficiency of the path-following algorithm, and the various theoretical performances obtained shows the efficiency of a kite dedicated to vessels auxiliary propulsion.

Un de nos grands défis actuels est la décarbonisation du réseau électrique en éliminant les générateurs d'électricité à base de carburant, et de les remplacer de préférence par des ressources publiquement acceptés et qui respectent la nature de l'environnement. C'est où les ressources énergétiques renouvelables soulèvent comme une solution prometteuse. Les Systèmes de génération d'électricité à cycle de relaxation représentent notamment une classe intéressante des énergies renouvelables. Un tel système doit retrouver périodiquement un état qui permet la production d'énergie, ce qui entraîne un cycle à deux phases : une phase de génération et une phase de récupération qui consomme l'énergie. L'intérêt principal de cette thèse est focaliser sur le système de traction à base de cerf-volant, appelé par la suite le Kite Generator System (KGS). Il s'agit d'une solution proposée pour extraire l'énergie du vent stable et forte dans les hautes altitudes. Son principe de fonctionnement est d'entraîner mécaniquement un générateur électrique au sol en utilisant un ou plusieurs cerfs-volants captifs. La problématique est divisée en deux objectifs : 1 - L'optimisation et le contrôle du cycle de relaxation afin de maximiser la puissance moyenne produite par le système. Deux stratégies de contrôle sont proposées à cet effet : une basée sur un contrôle du modèle non linéaire prédictif (Nonlinear model predictive control - NMPC), et la deuxième basée sur l'application des contraintes virtuel (Virtual Constraints Control - VCC). 2 - L'Intégration du système sur le réseau électrique ou l'employer pour alimenter une charge isolée. Ces problèmes sont abordés dans cette thèse, réalisée au laboratoire de génie électrique de Grenoble (G2ELab) en collaboration avec le laboratoire d'Image Parole Signal Automatique de Grenoble (GIPSA-Lab). / One of our current major challenges is decarbonizing the electric grid by eliminating fuel based electricity generators, and replacing them preferably by nature-friendly publicly accepted resources. That is where renewable energy resources raise as a promising solution. Power relaxation-cycle systems represent an interesting and particular class of renewable. Such a system needs to regain periodically a state that allows energy production. Hence, it has two phases: A generation during which the system is working in its "power" region and is able to generate power and a recovery phase that starts when the system reaches its power region boundaries and resets the system's state to start a new generation phase, which results in power consumption. The main focus of this PhD dissertation is the kite-based traction system, named thereafter the kite generator system (KGS), which emerged as an important class of renewable energy systems that uses relaxation phases. It is a solution proposed to extract energy from the steady and strong wind found in high altitudes. Its operation principle is to mechanically drive a ground-based electric generator using one or several tethered kites. The problematic is divided into two objectives: 1 - Optimization and control of the relaxation cycle to maximize the system's average produced power. Two control strategies are proposed for this purpose: A nonlinear model predictive control (NMPC) based and virtual constraints control (VCC) based one. 2 - Integration of the system on the electric grid or employing it to supply an isolated load. These problems are addressed in this thesis, realized in Grenoble Electrical Engineering laboratory (G2ELab) with collaboration with Grenoble Image Parole Signal Automatique laboratory (GIPSA-Lab).

Cette thèse fait partie du projet beyond the sea® qui a pour but de développer la traction par cerf-volant à boudins gonflés (kite) comme système de propulsion auxiliaire des navires. Comme le kite est une structure souple, il est nécessaire de mettre en place une boucle d’interaction fluide-structure pour calculer la géométrie du kite en vol et ses performances aérodynamiques. Un modèle de Ligne Portante 3D Non-Linéaire a été développé pour pouvoir gérer ces ailes non planes, avec des angles de dièdre et de flèche qui varient le long de l’envergure, et également pour pouvoir prendre en compte la non-linéarité du coefficient de portance de la section aérodynamique. Le modèle a été vérifié par des simulations RANSE sur différentes géométries et donne des résultats satisfaisants pour des angles d’incidence et de dérapage variant jusqu’à 15°, avec des différences relatives de quelques pour cent pour l’estimation de la portance globale de l’aile. Les résultats locaux sont aussi correctement estimés, le modèle est capable d’estimer la position du minimum et du maximum de chargement local, selon l’envergure de l’aile, et cela même pour une aile en dérapage. En parallèle, un modèle structure a été développé. L’idée principale du modèle Kite as a Beam est de réduire le kite à un ensemble d’éléments poutre, chacun équivalent à une partie du kite composé d’une section du boudin d’attaque, de deux lattes gonflées et de la canopée correspondante. Le modèle Kite as a Beam a été comparé à un modèle éléments finis complet du kite sur des cas de déplacements élémentaires. Les résultats montrent certaines différences de comportement entre les deux modèles, avec notamment une surestimation de la raideur en torsion pour le modèle Kite as a Beam. Finalement, le modèle Kite as a Beam a été couplé avec la Ligne Portante 3D Non-Linéaire, puis comparé au modèle éléments finis, couplé également avec la Ligne Portante. La réduction du temps de calcul est réellement importante mais les résultats de la comparaison montrent la nécessité de calibrer le modèle Kite as a Beam pour pouvoir retrouver correctement les résultats du modèle éléments finis. / The present thesis is part of the beyond the sea® project which aims to develop tethered kite systems as auxiliary devices for ship propulsion. As a kite is a flexible structure, fluid-structure interaction has to be taken into account to calculate the flying shape and aerodynamic performances of the wing. A 3D Non-Linear Lifting Line model has been developed to deal with non-straight kite wings, with dihedral and sweep angles variable along the span and take into account the non-linearity of the section lift coefficient. The model has been checked with 3D RANSE simulations over various geometries and produces satisfactory results for range of incidence and sideslip up to 15°, with typical relative differences of few percent for the overall lift. The local results are also correctly estimated, the model is able to predict the position of the minimum and maximum loading along the span, even for a wing in sideslip. Simultaneously, a structure model has been developed. The core idea of the Kite as a Beam model is to approximate a Leading Edge Inflatable kite by an assembly of beam elements, equivalent each to a part of the kite composed of a portion of the inflatable leading edge, two inflatable battens and the corresponding canopy. The Kite as a Beam model has been compared to a complete kite Finite Element model over elementary comparison cases. The results show the behaviour differences of the two models, for example the torsion stiffness is globally overestimated by the Kite as a Beam model. Eventually, the Kite as a Beam model coupled with the 3D Non-Linear Lifting Line model is compared to the complete finite element model coupled with the 3D Non-Linear Lifting Line model. The gain in computation time is really significant but the results show the necessity of model calibration if the Kite as a Beam model should be used to predict the results of the complete finite element model.

The purpose of this report has been to examine reason(s) behind the return of the red kite (Milvus milvus) to Hornborgasjön (a government-protected lake situated in the southwest of Sweden). The method of the study has been mainly based on observation-data reaching back to the latter part of the 19th century and ending with the year 2018, with the emphasis on the increasing numbers of nesting red kites during the 21st century. As a part of the study, email correspondence with ornithologists, mainly from Hornborgasjön field station, was also conducted, as well as comparison with other scientific research studies on the red kite. The results indicate that the red kite was a common bird of prey in the southern part of Sweden until the mid-19th century, after which the population started to decline. The main reasons seem to be both direct and indirect persecution. As a part of this the red kite, as well as many other birds of prey, were severely affected by different kinds of biocides used in the agriculture and in the forest industry. The return of the red kite seem to be a result of three factors, firstly it became protected in the 1920th, secondly a cease of the use of the most severely effecting biocides and thirdly a conservation project that started in Skåne in the mid-1970s. As the population of red kites increased in Skåne they started to extend their population northwards and thereby made their way back to Hornborgasjön. / <p>På grund av Covid-19 hölls presentationen via zoom</p>

Thesis (MA (English))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This thesis explores the themes of representation and identity in four post-9/11 novels: Khaled Hosseini’s The Kite Runner, Mohsin Hamid’s The Reluctant Fundamentalist, Frédéric Beigbeder’s Windows on the World and Don DeLillo’s Falling Man. The novels of Hosseini and Hamid represent the experience of two Muslim protagonists from Afghanistan and Pakistan who immigrate to the US. The protagonists offer two contrasting understandings of fundamentalism, using this lens to understand the terrorist figure and American society respectively. The construction of power for both the American society and the terrorist is argued to be located in images which are linked to masculinity: money, sport, militancy, sex and religious devotion. The personal experiences of these protagonists reflect the political circumstances which they encounter, and both characters identify with national identities in ways which relate to their readings of representations of identity and news media. Beigbeder and DeLillo’s novels are discussed using the theme of trauma. The novels portray the experiences of American characters who are confronted with 9/11 and suffer from disorientation and loss. The negotiation of this loss takes place in relation to entanglements with the terrorist figure, who penetrates the physical and psychological spaces of these characters. Images of masculinity are evoked in order to signify this loss of power, where the destabilising of the paternal role is linked to the pervasive sense of vulnerability which the characters experience after the attacks. Memorials and rituals become ways of dealing with disorientation. The two novels unsettle the distinction between terrorist and terrorised in order to negotiate a new American identity after 9/11. / AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek temas van representasie en identiteit in vier post-9/11 romans, naamlik Khaled Hosseini se The Kite Runner, Mohsin Hamid se The Reluctant Fundamentalist, Frédéric Beigbeder se Windows on the World en Don DeLillo se Falling Man. Hosseini en Hamid se romans verbeeld die ervarings van twee Muslim-protagoniste, onderskeidelik afkomstig van Afghanistan en Pakistan wat na die VSA immigreer. Hierdie protagoniste verbeeld twee uiteenlopende beskouïngs van fundamentalisme wat gevolglik aangewend word om die terroris-figuur en die Amerikaanse gemeenskap te verstaan. Die konstruksie van mag vir die Amerikaanse gemeenskap en die terroris-figuur word getoon, is geleë in beelde wat verband hou met manlikheid, naamlik geld, sport, militarisme, seks en toegewydheid. Die persoonlike ervarings van hierdie protagoniste weerspieël die politieke omstandighede waarmee hulle kennis maak. Beide hierdie karakters vereenselwig hulself met nasionale identiteite op grond van hul begrip van representasie van identiteit en die media. Beigbeder en DeLillo se romans word volgens die tema van trauma vergelyk. Hierdie romans beeld die ervarings van Amerikaanse karakters wat met 9/11 gekonfronteer word en met disoriëntasie en verlies worstel, uit. Die oorweging van hierdie verlies vind plaas in verhouding tot ontmoetings met die terroris-figuur wat die fisiese en psigiese ruimtes van hierdie karakters binnedring. Voorstellings van manlikheid word opgeroep om die verlies van mag ten toon te stel. Hierdie verlies van mag word gekenmerk deur die destabilisering van die vaderlike rol tesame met die diepgaande sin van weerloosheid wat die karakters na die aanval ervaar. Gedenktekens en rituele word vervolgens instellings om met die disoriëntasie om te gaan. Uiteindelik problematiseer die twee romans die onderskeid tussen terroris en geterroriseerde om sodoende ’n nuwe Amerikaanse identiteit ná 9/11 tot stand te bring.

This thesis is concerned with transnational literature and writers of the Middle Eastern and South Asian diasporas. It argues that the diasporic position of the authors enables their roles as comprador subjects. The thesis maintains that the figure of the comprador is always acted upon by its ontological predisposition, so that diasporic positionality often involves a single subject which straddles and speaks from two or more different subject positions. Comprador authors can be said to be co-opted by Western metropolitan publishing companies who stand to benefit by marketing the apparent marginality of the homelands about which these authors write. The thesis therefore proceeds from the notion that such a diasporic position is the paradoxical condition of the transnational subject or writer. I submit that there is, to some degree, a questionable element in the common political and cultural suggestions that emerge upon closer evaluation of diasporic literature. Indeed, a charge of complicity has been levelled against authors who write, apparently, to service two distinct entities – the wish to speak on behalf of a minority collective, as well as the imperial ‘centre’ which is the intended interlocutor of the comprador author. However, it is this difference, the implied otherness or marginality of the outsider within, which I argue is sometimes used by diasporic writers as a way of articulating with ‘authenticity’ the cultures and politics of their erstwhile localities. This thesis is concerned, therefore, with the representation of ‘the East’ in four novels by diasporic, specifically comprador writers, namely Salman Rushdie’s Midnight’s Children, Hanif Kureishi’s The Buddha of Suburbia, and Khaled Hosseini’s The Kite Runner and A Thousand Splendid Suns. I suggest that the ‘third-world’ and transnational literature can also be a selling point for the transnational subject, whose representations may at times pander to preconceived ideas about ‘the Orient’ and its people. As an illustration of this double-bind, I offer a close reading of all the novels to suggest that on the one hand, the comprador author writes within the paradigm of the ‘writing back’ movement, as a counter-discourse to the Orientalist representations of the homeland. However, the corollary is that such an attempt to ‘write back’, in a sense, re-inscribes the very discourse it wishes to subvert, especially because the literature is aimed at a ‘Western’ audience. Moreover, the template of the comprador could be used to explain how a transnational post-9/11 text from an Afghan-American, for instance, may be put to the service of the imperial machine, and read, therefore, as a supporting document to the U.S. policy on Afghanistan.