Cette thèse vise à étudier les effets de la transition laminaire - turbulent et du contrôle actif de l’angle de calage des pales sur les performances de l’hydrolienne à axe transverse SHIVA (Système Hydrolien Intelligent à Variation d’Angle) développée à l’institut de Recherche de l’Ecole-Navale (IRENav). L’écoulement transitionnel autour d’un hydrofoil est, d’abord étudié en comparant des résultats expérimentaux et numériques. Les résultats expérimentaux ont été obtenus dans le tunnel hydrodynamique de l’IRENav. La transition s’effectue par un mécanisme de bulbe de séparation laminaire. Les comparaisons sont fondées sur l’analyse locale des pressions, des profils de vitesse dans la zone du bulbe de séparation laminaire et sur l’analyse des portances, traînées et moments mesurés sur un profil fixe et en mouvement de tangage forcé. Des calculs RANS 2D, avec et sans modèle de transition (ɣ— Reo), RANS 3D et LES 2.5D ont été menés afin de comparer les approches et évaluer la précision des simulations. L’étude montre que le modèle de transition ɣ — Reo améliore nettement les résultats obtenus par rapport à un modèle tout turbulent (k — w SST) dans le cas d’un écoulement transitionnel. L’influence de la transition laminaire - turbulent sur les performances de la turbine SHIVA est ensuite étudiée en comparant les résultats de calculs effectués avec et sans modèle de transition. L’approche est bidimensionnelle. L’utilisation du modèle de transition est intéressante au paramètre d’avance ʎ = 2 pour lequel les pales subissent un décrochage dynamique important. Le développement du tourbillon de bord d’attaque, favorisé par le modèle de transition, permet en effet une meilleure prédiction du décrochage. Les valeurs de ʎ supérieures sont moins concluantes du fait de la prédiction d’une tramée trop faible par le modèle de transition. Enfin, l’influence du contrôle actif du calage des pales sur les performances de la turbine est étudiée au point de fonctionnement optimal de la turbine ʎ = 3. Des lois de calage avancées sont développées, permettant d’agir indépendamment sur la moitié amont ou aval de la turbine. La meilleure loi testée permet une augmentation du coefficient de puissance de 34% tout en lissant la répartition du couple. / This work studies the laminar-turbulent transition and the pitch control effects on the performances of a vertical axis tidal turbine (SHIVA) developed at the French naval academy research institute. Firstly, experimental and numerical results are compared to study the transitional flow around a hydrofoil. The experiments were carried out in the hydrodynamic tunnel of the French naval academy research institute and the laminar-turbulent transition was triggered by a laminar separation bubble mechanism. Comparisons are based on the local analysis of pressure data and velocity profiles in the vicinity of the laminar separation bubble. Lift, drag and moment coefficients measured on a fixed hydrofoil and on a hydrofoil undergoing a pitching movement are also used for comparison. 2D RANS calculations carried out with or without a transition modal (ɣ — Reo), 3D RANS calculations and 2.5D LES calculations were run so as to assess the accuracy of each type of simulation. This study shows that the ‘y Reo transition modal clearly improves the accuracy of the results compared to a fully turbulent turbulence model (k— w SST) when considering a transitional flow. The influence of the laminar-turbulent transition on the performance of the SHIVA turbine is then studied. Results of 2D calculations run with and without transition model are compared. The use of the transition modal is relevant at the tip speed ratio value ʎ = 2 for which the blades undergo dynamic stall. The transition modal leads to a better prediction of the leading edge vortex development and then allows a better prediction of the dynamic stall. The use of the transition model at higher ʎ values is less relevant since the transition modal appears to predict a drag too low. Finally, the effect of the pitch control on the SHIVA turbine performance is .studied at ʎ = 3, for which the power coefficient is the highest. Advanced pitching laws are developed to modify the blades’ angle of attack independently on the upstream and downstream halves of the turbine. The best pitching law tested in this study leads to an improvement of the power coefficient by 34% and smooths the torque distribution.

The 21st century would be a nightmare for Don Quijote: thousands of windmills are installed all over the globe and the number will increase tremendously over the next years. If climate change was an issue in the early 17th century, Don Quijote might have specialized in fighting nuclear or fossil fuel power plants. The change in power production is clearly pronounced, and it inspires the market to respond immediately. Numerous wind turbine manufacturers emerge, developing one technological innovation after another. The trend clearly goes in one direction: horizontal axis wind turbines in all possible variations. However, there are a few companies that do not follow the mainstream – they swim against the current and introduce new concepts, with the potential to set new standards in the industry. Nevertheless, the question whether these companies can establish operations and survive in an industry dominated by large multinational corporations arises. If these companies want to become recognized, they need to compete on an international scale from the outset – they become born globals. This master’s thesis investigates the preconditions under which an innovative start-up company can become born global in the wind turbine industry. For that, distinctive resources and capabilities of such companies, as well as key success factors for the industry are defined. Furthermore, enhancing or restricting parameters lying within company’s environment – in particular, within its networks – are discovered. These findings are based on and supported by the case study of an innovative vertical axis wind turbine manufacturer. In addition, the influence of this company’s university spin-off origin is investigated.

La technique d'intégration des systèmes éoliens verticaux (VAWT) au service des logements individuels, collectifs et tertiaires est une approche intéressante pour les acteurs de la maitrise d'énergie pour promouvoir une utilisation rationnelle de l'énergie. Le choix de l'implantation d'une éolienne en milieu urbain est déterminé par la hauteur des bâtiments, la vitesse du vent et l'intensité de turbulence du site. Les conditions de vents sévères à faible altitude sont favorables à une implantation de VAWT. Dans certaines villes, la hauteur moyenne des bâtiments est relativement faible et ceci fait qu'en ces lieux, les VAWTs sont appréciables par rapport aux HAWTs. La mécanique des fluides numériques (CFD) est mise en œuvre pour modéliser les écoulements d'air au travers d'éoliennes et des bâtiments. Un problème CFD modélisé avec un modèle de turbulence approprié donneront des résultats de simulations qui s'approcheront des réalités physiques et des résultats de l'expérimentation. Dans cette étude, les modèles standard k-" et SST k-! ont été utilisés. Après analyse des possibilités d'intégration d'une VAWT, la toiture reste la zone d'intégration la plus intéressante. En plus de l'étude aérodynamique, nous avons entamé une modélisation électrique de la chaîne de conversion de l'éolienne en utilisant le logiciel Matlab/Simulink. Le travail a été effectué dans le but de déterminer la puissance électrique susceptible d'être produite par l'éolienne. Pour finaliser cette étude, un modèle de couplage électrique de VAWTs avec un bâtiment considéré comme un modèle de charge est présenté. / The building integration of the vertical axis wind turbine (VAWT) to supply the individual, collective and tertiary residences consumption is an interesting approach that can help architects and the actors of the energy control to promote a rational use of renewable energy in the in homes. The choice of the location of the urban wind turbine type is determined by building height, wind speed and turbulence intensity of the site. The severe conditions of wind at low altitude are favorable for a VAWT installation. In some cities, the average buildings height is low, in these places, the VAWTs must be appreciable compared to the HAWTs. The modelling of the air flow through the wind turbine and the couple building-wind turbine involves the computation fluid dynamics (CFD). A problem modeled with a suitable turbulence model will give results that approach the physical reality and the experiment results. In this study, the standard k-" and SST k-! models were used. After analyzing the possibilities of VAWT integration, the roof is the most interesting integration area. In addition to CFD method, we have started to study the electrical model of the VAWT. The work was conducted to determine the electrical power generated by the wind turbine using Matlab/Simulink software. To complete the study, a VAWT model coupled with a building where the building is considered as a consumption model is presented.

A Savonius wind turbine is a self-starting vertical axis rotor. It can be designed to be compact in size and also produces less noise which makes it suitable to integrate into urban spaces such as rooftops and sign-poles. These characteristics make it interesting from a sustainability point of view, especially when aiming to increase the decentralization of electricity production. This thesis aimed to investigate the aerodynamic performance of different two-bladed Savonius profiles by varying the blade arc angle and the overlap ratio. For evaluation, the dimensionless power coefficient and torque coefficient were investigated over different tip speed ratios. The study was conducted numerically with 2D simulations in Ansys Fluent. The partial differential equations describing the characteristics of the flow, including the flow turbulence effects, were solved with the Reynolds-average Navier Stokes in combination with the k-omega SST model. A validation was performed by comparing data from simulated and experimental tests of a semi-circular profile and a Benesh profile. The investigation of the blade arc angle and overlap ratio was performed on a Modified Bach profile. The profile with a blade arc angle of 130 degrees and an overlap ratio of 0.56 generated a maximal power coefficient of 0.267 at a tip speed ratio of 0.9. This blade configuration generated the best performance of all conducted simulations in this project. However, this project contained uncertainties since simulations can never be an exact description of reality. The project was also limited by the computational power available. Nevertheless, according to the conducted simulations, it was observed that a higher blade arc angle and a larger overlap ratio seem to generate higher efficiency. / En Savonius vindturbin är en självstartande vertikalaxlad rotor som kan utformas i en kompakt design samtidigt som den producerar mindre oljud än horisontalaxlade vindkraftverk. Dagens hållbarhetssträvan i kombination med Savonius turbinens karakteristiska egenskaper gör den till ett potentiellt starkt vertyg för vindenergi. Då den kan placeras på exempelvis hustak eller skyltstolpar, utan att störa närliggande omgivning, finns det många möjliga sätt att implementera och integrera den i samhällets infrastruktur. Målet med detta projekt var att undersöka den aerodynamiska prestationen för Savoniusturbiner med två blad genom att variera bladvinkeln och överlappningsförhållandet. För att jämföra de olika profilerna användes den dimensionslösa effektkoefficienten och momentkoefficienten. Dessa koefficienter beräknades i förhållande till löptalet. Studien utfördes numeriskt med 2D-simuleringar i Ansys Fluent. De partiella differentialekvationerna som beskriver flödets egenskaper, inkluderat turbulenseffekterna, löstes med Reynolds-average Navier Stokes i kombination med k-ω SST modellen. En validering utfördes genom att jämföra data med simulerade och experimentella värden av en Semi-circular profil och en Benesh profil. Studien av bladvinkel och överlappningsförhållandet utgick från en Modified Bach profil. Den mest effektiva profilen hade en bladvinkel av 130 grader och ett överlappsförhållande på 0,56. Den genererade en maximal effektkoefficient av 0,267 vid löptal 0,9. Projektet innehöll en del osäkerheter då simuleringar aldrig kan beskriva verkligheten till fullo. Den tillgängliga beräkningskapaciteten begränsade även projektet ytterligare. Trots vissa begränsningar, visar ändå utförda simuleringar att ökad bladvinkel och ökat överlappningsförhållande genererar högre effekt. / <p>This project was conducted within Stand up for wind and Stand up for energy.</p>

Anthropogenic climate change is approaching predicted tipping points and there is an urgent need to de-carbonize energy systems on a global scale. Generation technologies that do not emit greenhouse gas need to be rapidly deployed, and energy grids need to be updated to accommodate an intermittent fluctuating supply. Rapidly advancing battery technology, cost reduction of solar and wind power and other emerging generation technologies are making the needed changes technically and economically feasible. Extracting energy from fast-flowing tidal currents using turbines akin to those used in wind farms, offers a reliable and predictable source of GHG free energy. The tidal power industry has established the technical feasibility of tidal turbines, and is presently up-scaling deployments from single isolated units to large tidal farms containing many turbines. However there remains significant economic uncertainty in financing such projects, partially due to uncertainty in predicting the long-term energy yield. Since energy yield is used in calculating the project revenue, it is of critical importance. Predicting yield for a prospective farm has not received sufficient attention in the tidal power literature. this task has been the primary motivation for this thesis work, which focuses on establishing and validating simulation-based procedures to predict flows through large tidal farms with many turbines, including the back effects of the turbines. This is a challenging problem because large tidal farms may alter tidal flows on large scales, and the slow-moving wake downstream of each rotor influences the inflow to other rotors, influencing their performance and loading. Additionally, tidal flow variation on diurnal and monthly timescales requires long-duration analysis to obtain meaningful statistics that can be used for forecasting. This thesis presents a hybrid simulation method that uses 2D coastal flow simulations to predict tidal flows over long durations, including the influence of turbines, combined with higher-resolution 3D simulations to predict how wakes and local bathymetry influence the power of each turbine in a tidal farm. The two simulation types are coupled using a method of bins to reduce the computational cost within reasonable limits. The method can be used to compute detailed 3D flow fields, power and loading on each turbine in the farm, energy yield and the impact of the farm on tidal amplitude and phase. The method is demonstrated to be computationally tractable with modest high-performance computing resources and therefore are of immediate value for informing turbine placement, comparing turbine farm-layout cases and forecasting yield, and may be implemented in future automated layout optimization algorithms. / Graduate

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