<p>Low-frequency, long-range sound propagation over a seasurface has been calculated using a wide-angel Cranck-NicholsonParabolic Equation method. The model is developed toinvestigate noise from off-shore wind turbines. Thecalculations are made using normal meteorological conditions ofthe Baltic Sea. Special consideration has been made to a windphenomenon called low level jet with strong winds on rather lowaltitude.</p><p>The effects of water waves on sound propagation have beenincorporated in the ground boundary condition using a bossmodel. This way of including roughness in sound propagationmodels is valid for water wave heights that are small comparedto the wave length of the sound. Nevertheless, since only lowfrequency sound is considered, waves up to the mean wave heightof the Baltic Sea can be included in this manner.</p><p>The calculation model has been tested against benchmarkcases and agrees well with measurements. The calculations showthat channelling of sound occurs at downwind conditions andthat the sound propagation tends towards cylindrical spreading.The effects of the water waves are found to be fairlysmall.</p><p><b>Keywords:</b>wind turbine noise, off-shore wind power,long-range sound propagation, parabolic equation, scattering,water waves</p>

This thesis investigates the computation of invariance kernels for planar nonlinear systems with one input, with application to wind turbine stability. Given a known bound on the absolute value of the input variations (possibly around a fixed non-zero value), it is of interest to determine if the system's state can be guaranteed to stay within a desired region K of the state space irrespective of the input variations. The collection of all initial conditions for which trajectories will never exit K irrespective of input variations is called the invariance kernel. This thesis develops theory to characterize the boundary of the invariance kernel and develops an algorithm to compute the exact boundary of the invariance kernel. The algorithm is applied to two simplified wind turbine systems that tap kinetic energy of the turbine to support the frequency of the grid. One system provides power smoothing, and the other provides inertial response. For these models, limits on speed and torque specify a desired region of operation K in the state space, while the wind is represented as a bounded input. The theory developed in the thesis makes it possible to define a measure called the wind disturbance margin. This measure quantifies the largest range of wind variations under which the specified type of grid support may be provided. The wind disturbance margin quantifies how the exploitation of kinetic energy reduces a turbine's tolerance to wind disturbances. The improvement in power smoothing and inertial response made available by the increased speed range of a full converter-interfaced turbine is quantified as an example.

This thesis focuses on modelling of wind turbine wakes when they are affected by real complex terrain features, such as hills and forests, and also examines the effect of the rotational momentum imparted to the downstream wake from the rotor blades. Modelling work is carried out using the commercial Computational Fluid Dynamics (CFD) solver FLUENT. Motivation for this project was the fact that there is currently limited knowledge on several issues that affect the operation of a wind farm in a complex terrain environment. Wind developers normally use commercial, easy-to-use software (such as WAsP) to predict the potential wind farm output , which are based on simple linear models to model wakes and wind flow orographic effects and have been calibrated for cases of simple terrain. In cases of complex terrain, they are expected to give errors due to arising non-linearities. After a review of the relevant literature, the chosen CFD procedure is explained. This involves the use of 3-D Reynolds Averaged Navier-Stokes equations using the Reynolds Stress Model for the turbulence closure, in order to account for the anisotropy in atmospheric turbulence. The Virtual Blade Model in FLUENT is demonstrated as a useful tool for modelling the rotor effects without the need of meshing the rotor geometry in detail and avoiding significant computational cost. The approach is initially validated with the widely documented Nibe measurements, which involved full-scale observations of a single wake over at terrain. The model is also tested in the case of a wind turbine operating at the summit of an ideal, Gaussian hill. The wake development is examined in detail and in comparison with another CFD approach. Most notably, a slight divergence is found in the wake path as it evolves downwind. Additionally, the proposed approaches of modelling the neutral atmospheric ow over a real hill and over a forest are validated with full-scale measurements. Ultimately, the work includes the modelling of real wind farms over complex terrain and validating the results with measurements. A coastal complex terrain wind farm is initially examined and results are validated with SCADA measurements and compared with results using the WAsP wind modelling software. Finally, a wind farm over hilly terrain and near forests is also considered and the effect of the forest in the wake is studied. Results are also validated with full-scale measurements.

Gegenstand des Vortrages ist Entwicklung und Validierung eines elastischen Mehrkörpermodells der Prototypenanlage W2E-120/3.0fc der Frima W2E Wind to Energy GmbH. Folgende Schwerpunkte werden gesetzt: - Anforderungen an die Modellierung - Topologie des Mehrkörpermodells - Einbindung elastischer Körper - Einbindung aerodynamischer Lasten - Einbindung des Anlagenreglers - Experimentelle Validierung anhand von Produktionslastfällen Die vorgestellte Arbeit ist Teil des aktuellen Forschungsprojektes "DynAWind– Leichtbauoptimierte Konstruktionen von Windenergieanlagen" am Lehrstuhl für Technische Mechanik/Dynamik in Zusammenarbeit mit der W2E Wind to Energy GmbH.

Doctor of Philosophy / Department of Electrical and Computer Engineering / Behrooz Mirafzal / In this dissertation, a new topology for Direct-Drive Wind Turbines (DDWTs) with a new power electronics interface and a low-voltage generator design is presented. In the presented power electronics interface, the grid - side converter is replaced by a boost Current Source Inverter (CSI) which eliminates the required dc-bus capacitors resulting in an increase in the lifetime of DDWTs. The inherently required dc-link inductor for this topology is eliminated by utilizing the inductance of the Permanent Magnet Synchronous Generator (PMSG). The proposed three-phase boost CSI is equipped with Reverse-Blocking IGBTs (RB-IGBT) and the Phasor Pulse Width Modulation (PPWM) switching pattern to provide a 98% efficiency and high boost ratios ([superscript V]LL/V[subscript dc]) up to 3.5 in a single stage. In this dissertation, Phasor Pulse Width Modulation (PPWM) pattern for the boost – CSI is also modified and verified through simulation and experimental results. In order to realize potential capabilities of the boost inverter and to assist its penetration into renewable energy systems, the boost inverter dynamic behaviors are studied in this dissertation. Then, the developed models are verified using circuit simulations and experiments on a laboratory-scale boost – CSI equipped with RB-IGBTs. The developed dynamic models are used to study the stability of the boost – CSI through root locus of small signal poles (eigenvalues) as control inputs and load parameters vary within the boost inverter's operating limits. The dynamic models are also used to design the control schemes for the boost – CSI for both stand-alone and grid-tied modes of operation. The developed controllers of the boost – CSI are verified through simulation and experimental results. In this dissertation, the boost – CSI steady-state characterization equations are also developed and verified. The developed boost – CSI is used to replace the grid - side converter in a DDWT. A reliability analysis on the power electronics interface of an existing and developed topology is presented to demonstrate the increase in the mean time between failures. The boost – CSI enables conversion of a low dc voltage to a higher line-to-line voltage enabling the implementation of a low-voltage generator. This further enables a reduction in the number poles required in DDWT generators. The feasibility of the presented low-voltage generator is investigated through finite element computations. In this dissertation, a 1.5MW low-voltage generator designed for the proposed topology is compared with an existing 1.5MW permanent magnet synchronous generator for DDWTs to demonstrate the reduction in the volume, weight, and amount of permanent magnet materials required in the generator. The feasibility of the developed system is supported by a set of MATLAB/Simulink simulations and laboratory experiments on the closed-loop stand-alone and grid-tied systems.

Ce travail porte sur la mise en œuvre de simulations sur des pales de machines tournantes. Une première partie de la thèse porte sur l’amélioration des performances du couplage fluide-structure. Des nouveaux algorithmes sont présentés. Une nouvelle méthode de déformation de maillage est évaluée. Les développements sont validés à partir de plusieurs cas tests. La deuxième partie porte sur l’application des avancées à des machines tournantes. Une première validation est faite sur une hydrolienne. La vibration d’une pale au passage du mat est étudiée. Enfin, des résultats sur une hydrolienne industrielle sont exposés. / A methodology to simulate blades of turbines is developed. A first part is dedicated to improving the performance of the fluid-structure coupling. New algorithms are presented. A new mesh morphing solution is shown. Developments are validated on many test cases. A second part is dedicated to applying the developments on turbines. A first validation is made on a water turbine. The vibration of a blade interacting with a mast is studied. Finally, some results of an industrial water turbine are shown.

Este trabalho tem como proposta desenvolver um difusor aerodinâmico compacto para uma turbina eólica de pequena escala, objetivando alcançar um melhor start rotacional (menor torque de partida para rotacionar) em baixas velocidades de vento. Um difusor é uma estrutura em forma de aro envolta ao rotor da turbina eólica, sua função é amplificar a captação e aceleração do vento, explorando os efeitos aerodinâmicos das zonas de vórtices de baixa pressão na saída do difusor. O estudo concentrar-se-á na manipulação da geometria dos difusores, analisando como seu design impacta no seu comportamento aerodinâmico impacta na capacidade do difusor equacionar as zonas de alta e baixa pressão ao longo de sua estrutura, essa relação é determinante para o efeito aerodinâmico que acelera o escoamento de ar, resultando em um start rotacional em baixas velocidade de vento. O ponto de partida para este trabalho são os estudos desenvolvidos por Ohya et al. (2010) sobre difusores compactos-flangeados (compact-type brimmed diffuser) para turbinas eólicas, denominado Wind-lens Technology. Para alcançar os objetivos, esta pesquisa vai utilizar simulações por CFD com software de túnel de vento virtual e ensaios experimentais em túnel de vento físico para avaliar o comportamento dinâmico (turbina + difusor). Foram desenvolvidas dezenove geometrias a partir de uma área construtiva padronizada para o design de difusores. Desenvolveu-se também, a partir dos resultados encontrados, um MFI (microseparador de fluxo interno), que consiste em uma estrutura adicional com função de potencializar as zonas de vórtices (baixa pressão) no plano de saída do escoamento de ar dos difusores. Os resultados mostraram que a manipulação da geometria do difusor produziu resultados promissores em comparação com o modelo de referência, alcançando em algumas geometrias de difusores um melhor start rotacional. O MFI mostrou-se eficaz para potencializar as zonas de baixa pressão e melhorou o start rotacional. Ao final, definiu-se dois modelos de difusores e suas respectivas versões com MFI como as melhores opções para o start rotacional. / This work aims to develop a compact wind turbine for a turbine and a small scale, aiming at a better rotational start at low wind speeds (lower starting torque to rotate). A diffuser is a rim-shaped structure wrapped around the wind turbine rotor, its function is to amplify the wind uptake and acceleration, exploiting the aerodynamic effects of the low-pressure vortex zones at the diffuser outlet. The study will focus on the manipulation of the diffuser geometry, analyzing how its design impacts on its aerodynamic behavior, especially on the diffuser's ability to equate the high and low pressure zones along its structure, this relation is decisive for the aerodynamic effect that accelerates the air flow, resulting in a rotational start at low wind speeds. The basis for this work are studies developed by Ohya et al. (2010) on compact-flanged diffusers for wind turbines, called Wind-lens Technology. To achieve the objectives, this research will use CFD simulations with virtual wind tunnel software and experimental tests in physical wind tunnel to evaluate the dynamic behavior (turbine + diffuser). Nineteen geometries were developed from a standardized design area for the design of diffusers. An MFI (internal flow microseparator) has also been developed, which is an additional structure whose function is to potentiate the low pressure zones of the diffusers. The results showed that the manipulation of the diffuser geometry produced promising results in comparison to the reference model, reaching in some conditions superior results in RPM and initial start. The MFI proved to be effective in boosting the low pressure zones and improved the initial start. At the end, two models of diffusers and their respective versions with MFI were defined as the best options for the initial start.

L’étude de cas de l’« éolienne » est abordée au travers de quatre scènes techniques : moulins à huile à Lille à la fin du XVIIIe siècle, moulins électriques au Danemark au tournant du XXe siècle, aérogénérateurs en France dans les années 1950, éoliennes modernes à la fin du XXe siècle en Allemagne du Nord. Chacune de ces scènes techniques fait l’objet d’une analyse technique articulée autour de la connaissance du vent, de l’aérodynamique et de la mécanique des structures et d’une analyse socio-économique centrée sur le secteur d’activité dans lequel elles sont intégrées, pour comprendre ce que les gens font avec cet objet technique. Cette recherche montre que toutes les éoliennes ayant connu une large diffusion sont fondées sur une même architecture globale et sur un même principe physique permettant de définir des indicateurs de performance et de régularité sur une longue période. Envisagée comme machine de production et non comme convertisseur d’énergie, chaque éolienne est optimale dans le contexte technique et socio-économique de son époque. L’histoire des techniques proposée s’articule autour de la notion de fonction en relation d’une part avec le fonctionnement opératoire d’une combinaison de structures matérielles, d’autre part, l’intention de concepteurs et d’utilisateurs agissant suivant des normes sous-tendues par des valeurs morales, esthétiques et culturelles. / The case study of the "wind turbine" is analyzed through four technical scenes: oil mills in Lille at the end of the 18th century, electric mills in Denmark at the turn of the 20th century, aerogenerators in France in the 1950s, modern wind turbines in the late twentieth century in northern Germany. Each of these technical scenes is the subject of a technical analysis based on the knowledge of wind, aerodynamics and structural mechanics and a socio-economic analysis centered on the sector of activity in which they are integrated, to understand what people are doing with this technical object.This research shows that all wind turbines that have been widely distributed are based on the same global architecture and on the same physical principle allowing the definition of indicators of performance and regularity over a long period. Considered as a production machine and not as an energy converter, each wind turbine is optimal in the technical and socio-economic context of its time.The proposed history of the techniques revolves around the notion of function in relation, on the one hand, to the operation of a combination of material structures and on the other to the intention of designers and users acting according to standards underpinned by moral, aesthetic and cultural values.

Energy is part of everyday life and renewable energy technologies are increasingly becoming part of our lived environments. Social scientists are responding to renewable energy technologies by investigating what people think about wind turbines (Aitken, 2010; Pasqualetti, 2011a, 2011b) and the distribution of community benefits (Cowell et al, 2011; Bristow et al 2012). This thesis adds to this body of research by describing Udny's renewable energy project and its capacity to effect change. More specifically, I examine what this community-owned wind turbine does with other situational elements to transform life within the community. Using the cartographic methods developed by Adele E. Clarke (2005), I map out the situation by drawing out the elements – this includes objects, people, organisations and discursive practices – and tracing their relations. Thinking sociologically about situational elements and their relational effects provokes a move towards ecological sociology and re-imagines social life as the effect of interconnected entities, such as materials and meanings, thoughts and actions, people and objects (Morton, 2007, 2010). Mapping the interconnectedness of societal ecologies depicts social life as neither distinct from the natural world (Catton and Dunlap, 1978, 1980) nor symmetrical with natures (Callon, 1986; Akrich and Latour, 1992; Asdal, 2008) but, rather, as part of relationally emergent ecologies. Udny's community renewable energy project illustrates the relational emergence of a social ecology, as the turbine and trust work with existing and emergent entities to enact change (Barad, 2007; Harman, 2009; Bennett, 2010; Morton, 2010, 2016). It is by doing things together that situational elements transform life within Udny (Clarke, 2005; Yusoff, 2013).

The renewable energy sources are the primary solution for energy demand in all the countries because it’s being harmless to the environment. In the short term, wind energy has the most potential among all the renewable energy technologies. In the European Union, Sweden is largely based on renewable energy for their energy demand. Sweden is one of the leading country in the EU where wind power has been growing rapidly. As wind turbines in recent time have been more and more commonly placed in forestal terrain in Sweden, it is of interest to know the difference in annual output compared to the flat terrain which was the earlier dominant terrain type for wind turbines. In this thesis, the difference between the two terrain types is investigated for a number of wind turbine models. This paper presents the study from the annual Vindstat report of the year 2015 and 2016. The data were accumulated in the Excel file and the terrain for turbine locations was classified using Google Earth. Finally, the power generation in both areas are compared by graphs and tables. The results indicate the difference in production according to the terrain and turbine rating. And it was a surprising finding that the difference between them is not more as we expected. Even more, further study is required to find the difference between in forest and flat wind turbines in all the aspects.