Les fermes houlomotrices de seconde génération qui seront déployées dans les années qui viennent seront composées d’un grand nombre de modules identiques mouillés en mer et rapportant au rivage l’électricité produite par câbles sous-marins. Il a été montré que le contrôle des machines houlomotrices permet d’augmenter significativement leur rendement. Cependant, le contrôle optimal d’un système houlomoteur est non causal, i.e. son application nécessite la prévision de la force d’excitation soumise par le champ de vague sur chacun des éléments de la ferme. Les travaux présentés dans ce manuscrit ont consisté à mettre en place une stratégie de contrôle permettant une récupération d’énergie proche de l’optimum théorique en tenant compte des interactions hydrodynamiques liées à la configuration de ferme et permettant de résoudre la non-causalité d’un tel contrôleur en utilisant uniquement l’information contenue dans les vecteurs d’états des machines de la ferme. Dans un premier temps, les équations reliant les différents états des machines de la ferme ont été établies puis ont été utilisées afin d'effectuer une prévision des états sur les corps contrôlés permettant ainsi d’appliquer un contrôle réactif pseudo causal. Afin de contraindre la dynamique des corps et maitriser l’horizon de non causal du contrôleur, une méthode de fenêtrage a été appliquée à l’impédance du contrôleur. À l’aide d’un simulateur temporel développé spécifiquement, une étude de sensibilité a été conduite pour définir les paramètres optimaux et le comportement de la stratégie de contrôle et de son fenêtrage. La robustesse et la performance du contrôleur ont ensuite été évaluées pour différents changements extérieurs comme la dérive des corps, les variations d’orientation de houle, et l’étalement spectral directionnel. L’application de la stratégie de contrôle à une ferme de 10 corps a montré une récupération d’énergie supérieure à 83% de la limite théorique maximale. / The next generation of wave farms will becomposed of a large number of identical devices deployed offshore, which will transfer the retrieved energy to the shore using submarine cables. It hasbeen proven that the control of Wave Energy Converters can improve their efficiency. However, one of the main challenges of WEC control is the noncausality of the optimal controller. Indeed, the time domain application of this kind of control requires the forecast of the excitation force applied by the wavefield on each device of the farm. The work presented in this thesis aimed at developing and assessing a control strategy with an energy efficiency close to the theoretical optimum, taking into account the hydrodynamic interactions between the farm devices, and solving the non-causality issue using the measurements of the states of the device of the array. First, the equations linking the devices’ states within the array have been established and used to performa deterministic forecast of the states of the controlled bodies, which allowed to apply a pseudo-causal reactive control. Moreover, a window function hasbeen applied to the controller impedance in order to constrain the dynamic of the controlled bodies, and also to regulate the non-causal horizon of the controller. Then, using a time domain simulator developed specifically, a sensibility analysis has been performed to define the optimal parameters and the behavior of the controller with the window function.The robustness and the performances of the controller have also been assessed when affected by exterior changes such as device drift, wave orientation modification, and directional spreading of the wave spectrum. The collaborative controlled strategy applied to a farm of 10 devices has shown an energy efficiency over 83% of the theoretical bound.

Renewable energies are believed to play the key role in assuring a future of sustainable energy supply and low carbon emissions. Particularly, this thesis focus on wave energy, which is created by extracting the power stored in the waves of the oceans. In order for wave energy to become a commercialized form of energy, modular deployment of many wave energy converters (WECs) together will be required in the upcoming future. This design will thus allow to benefit, among others, from the modular construction, the shared electrical cables connections and moorings, the reduction in the power fluctuations and reduction of deployment and maintenance costs. When it comes to arrays, the complexity of the design process increase enormously compared with the single WEC, given the mutual influence of most of the design parameters (i.e. hydrodynamic and electrical interactions, dimensions, geometrical layout, wave climate etc.). Uppsala University has developed and tested WECs since 2001, with the first offshore deployment held in 2006. The device is classified as a point absorber and consists in a linear electric generator located on the seabed, driven in the vertical direction by the motion of a floating buoy at the surface. Nowadays, one of the difficulties of the sector is that the cost of electricity is still too high and not competitive, due to high capital and operational costs and low survivability. Therefore, one step to try to reduce these costs is the development of reliable and fast optimization tools for parks of many units. In this thesis, a first attempt of systematic optimization for arrays of the Uppsala University WEC has been proposed. A genetic algorithm (GA) has been used to optimize the geometry of the floater and the damping coefficient of the generator of a single device. Afterwards, the optimal layout of parks up to 14 devices has been studied using two different codes, a continuous and a discrete variables real coded GA. Moreover, the method has been extended to study arrays with devices of different dimensions. A deterministic evaluation of small array layouts in real wave climate has also been carried out. Finally, a physical scale test has been initiated which will allow the validation of the results. A multi--parameter optimization of wave power arrays of the Uppsala University WEC has been shown to be possible and represents a tool that could help to reduce the total cost of electricity, enhance the performance of wave power plants and improve the reliability.

Obtaining the perfect renewable energy source is one of the most important questions of our lifetime. One renewable energy source that could be of interest in this question because of the characteristics of the power that could be extracted from it is wave energy. There has however not been enough research done to reach a technology viable enough for large scale adoption. This study was made to investigate how to formulate the optimum design guidelines and criteria for a chain and shackle in the connection line between buoy and wave energy converter (WEC). Firstly, by conducting a literature study the material and design of the system was chosen. A main goal of the report was to make it have value in the industry, because of this the choice of design and material was based on industry standards. The material choice became the austenitic stainless steel with the grade R4, and the design of choice became the stud less chain link and the forelock shackle. A value of the expected force in the buoy WEC connection line (buoy line) was extracted from sixteen different data sets given from a wave tank test done in COAST Laboratory of Plymouth University, UK. These tests were done with two different buoys, one with a cylindrical shape and one with a torus shape. They were also done with and without dampening (the dampening was equal to 59 kN). Each of these four configurations had four different tests conducted on them resulting in a total of sixteen different data sets. The force value that occurs in the buoy line from the sixteen different wave tank tests was then scaled up and used in calculating the final diameter of the chain link. A safety factor of 1.35 was used to account for the statistical uncertainties in the characteristic properties of the specific part. These calculations were based on the fact that all chains have to be proof loaded at 70 % of their minimum theoretical breaking load and that a chain should at maximum undergo a force that is equal to 25 % of its minimum breaking load. Extra material was also added to accommodate for the corrosion that will occur in submerged environments. Finally, a finite element analysis was done on one of the chains links. The results showed that the biggest amount of von Mises stress and equivalent plastic strain occur in the inner corner of the chain link. All the contact area and the “crown” were however also shown to have plastically deformed. The plastic deformation in the contact area does not discredit the design because it is a local plasticity in a small region which leads to work hardening which in turn means that the new yield strength is higher at the deformed points, this in turn means that the wave climate will only elastically deform the system under its cyclic load and that the system will not plastically deform more than the results from the proof loading. This is very positive and will give the system a prolonged lifetime. However plastic deformation in the “crown” contributes to crack initiation which with time may lead to fatigue failure and should be considered in future studies.

This research revolves around the concept design and theoretical validation of a new type of wave energy converter (WEC), comprising a pitching floater integrated with a resonant U-tank (RUT) and a Wells turbine as power take-off (PTO). Theoretical formulation of a fully coupled multi-body dynamic system, incorporating the thermodynamic processes of the RUT air chamber, its interaction with the PTO dynamics and their coupling with the floater is presented. Inaccuracies of the dynamic modeling of RUT based on Lloyd's low order model, which assumes constant hydrodynamic parameters irrespective of the frequency, are demonstrated by a series of high fidelity CFD simulations. These simulations are a systematic series of fully viscous turbulent simulations, using unsteady RANSE solvers, of the water sloshing at different frequencies of oscillation. Calibration of Lloyd’s model with CFD results evidenced that the RUT hydrodynamic parameters are not invariant to frequency. A numerical model was developed based on Simulink WEC-Sim libraries to solve the non-linear thermo-hydrodynamic equations of the device in time domain. For power assessment, parametric investigations are conducted by varying the main dimensions of the RUT and power RAOs were computed for each iteration. Performance in irregular sea state are assessed using a statistical approach with the assumption of linear wave theory. By superimposing spectrum energy density from two resource sites with RAO, mean annual energy production (MEAP) are computed. The predicted MEAP favorably compares with other existing devices, confirming the superior efficiency of the new proposed device over a larger range of incident wave frequency. / M.S. / This study present results of an investigation into a new type of wave energy converter which can be deployed in ocean and by its pitch response motion, it can harvest wave energy and convert it to electrical energy. This device consist of a floater, a U-tank (resonant U-tank) with sloshing water free to oscillate in response to the floater motion and a pneumatic turbine which produces power as air is forced to travel across it. The pneumatic turbine is used as the power take-off (PTO) device. A medium fidelity approach was taken to carry out this study by applying Lloyd’s model which describes the motion of the sloshing water in a resonant U-tank. Computational fluid dynamics (CFD) studies were carried out to calibrate the hydrodynamic parameters of the resonant U-tank as described by Lloyd and it was discovered that these parameters are frequency dependent, therefore Lloyd’s model was modelled to be frequency dependent. The mathematical formulation coupling the thermodynamic evolution of air in the resonant U-tank chamber, modified Lloyd’s sloshing water equation, floater dynamics and PTO were presented for the integrated system. These set of thermo-hydrodynamic equations were solved with a numerical model developed using MATLAB/Simulink WEC-Sim Libraries in time domain in other to capture the non-linearity arising from the coupled dynamics. To assess the annual energy productivity of the device, wave statistical data from two resource sites, Western Hawaii and Eel River were selected and used to carrying out computations on different iterations of the device by varying the tank’s main dimensions. This results were promising with the most performing device iteration yielding mean annual energy production of 579 MWh for Western Hawaii.

As a clean, abundant, and renewable source of energy with a strategic location in close proximity to global population regions, ocean wave energy shows major promise. Although much wave energy converter development has focused on large-scale power generation, there is also increasing interest in small-scale applications for powering the blue economy. In this thesis, the objective was to optimize the performance of small-sized, portable, oscillating-body wave energy converters (WECs). Two types of oscillating body WECs were studied: bottom hinged and two-body attenuator. For the bottom-hinged device, the goal was to show the feasibility of an oscillating surge WEC and desalination system using numerical modeling to estimate the system performance. For a 5-day test period, the model estimated 517 L of freshwater production with 711 ppm concentration and showed effective brine discharge, agreeing well with preliminary experimental results. The objective for the two-body attenuator was to develop a method of power maximization through resonance tuning and numerical simulation. Three different geometries of body cross sections were used for the study with four different drag coefficients for each geometry. Power generation was maximized by adjusting body dimensions to match the natural frequency with the wave frequency. Based on the time domain simulation results, there was not a significant difference in power between the geometries when variation in drag was not considered, but the elliptical geometry had the highest power when using approximate drag coefficients. Using the two degree-of-freedom (2DOF) model with approximate drag coefficients, the elliptical cross section had a max power of 27.1 W and 7.36% capture width ratio (CWR) for regular waves and a max power of 8.32 W and 2.26% CWR for irregular waves. Using the three degree-of-freedom (3DOF) model with approximate drag coefficients, the elliptical cross section had a max power of 22.5 W and 6.12% CWR for regular waves and 6.18 W and 1.68% CWR for irregular waves. A mooring stiffness study was performed with the 3DOF model, showing that mooring stiffness can be increased to increase relative motion and therefore increase power. / Master of Science / As a clean, abundant, and renewable source of energy with a strategic location in close proximity to global population centers, ocean wave energy shows major promise. Although much wave energy converter development has focused on large-scale power generation, there is also increasing interest in small-scale applications for powering the blue economy. There are many situations where large-scale wave energy converter (WEC) devices are not necessary or practical, but easily-portable, small-sized WECs are suitable, including navigation signs, illumination, sensors, survival kits, electronics charging, and portable desalination. In this thesis, the objective was to optimize the performance of small-sized, oscillating body wave energy converters. Oscillating body WECs function by converting a device's wave-driven oscillating motion into useful power. Two types of oscillating body WECs were studied: bottom hinged and two-body attenuator. For the bottom-hinged device, the goal was to show the feasibility of a WEC and desalination system using numerical modeling to estimate the system performance. Based on the model results, the system will produce desirable amounts of fresh water with suitably low concentration and be effective at discharging brine. The objective for the two-body attenuator was to develop a method of power maximization through resonance tuning and numerical simulation. Based on the two- and three-degree-of-freedom model results with approximate drag coefficients, the elliptical cross section had the largest power absorption out of three different geometries of body cross sections. A mooring stiffness study with the three-degree-of-freedom model showed that mooring stiffness can be increased to increase power absorption.

<p>Denna rapport ger förslag på olika metoder att automatiskt justera flytläget på en statiskt förankrad boj, en överblick över de processer som styr ändringen av vattennivån och en statisktisk analys på vattennivåförändringarna vid Stockholm, Kungsholmsfort och Kungsvik.</p><p>Beroende på vattenivåns variation finns olika metoder för justering. Områden med små variationer av vattennivå lämpar det sig bäst utan någon som helst justering av flytläget. Områden med inte för stora tidvattensförändringar bör justeras med ett system bestående av vinsch, växellåda med en utväxling på 10 000:1, en 12 V DC motor, ett skötselfritt 12 V batteri, en luftlindad linjärgenerator och en trådtöjningsgivare. Områden med stora variationer i tidvatten behöver en avlastning för motorn i form av en fjäder och dämpare. De monteras horizontellt inuti bojen för att skyddas från den yttre miljön.</p><p>Den statistiska analysen påvisade de största vattennivåändringarna vid både Kungsviks och Kungsholmsforts mätstationer, båda uppvisade ett intervall på 1,6 m mellan minimum och maximum. Kungsvik var den station med de största dagliga variationerna, detta på grund av tidvattnets påverkan i området.</p> / <p>This thesis gives examples of different methods of automated adjustment of floatation level for a static moored buoy, an overview of the theories behind water level change and a statistical analysis of the water level changes for Stockholm, Kungsholmsfort and Kungsvik.</p><p>Depending on the range and frequency of the water level change different methods of adjustment are recommended. For areas with small changes in sea level the best choice would be no adjustment of the floatation level. Areas that are influenced by moderate tidal ranges should incorporate a system of regulation consisting of a winch, gearbox with a gear ratio of around 10,000:1, 12 V DC motor, 12 V maintenance free battery, air coiled linear generator and a strain gauge. For areas with large tidal ranges the previous system should be complimented with a horizontally mounted spring, inside the buoy, to lessen the loads on the motor.</p><p>The statistical analysis found the largest extremes in water level of the three sites to be at Kungsvik and Kungsholmsfort, both exhibiting a range of almost 1.6 m. Kungsvik was the station with the largest daily variations, this is because this is the only station influenced by tidal variations.</p>

Denna rapport ger förslag på olika metoder att automatiskt justera flytläget på en statiskt förankrad boj, en överblick över de processer som styr ändringen av vattennivån och en statisktisk analys på vattennivåförändringarna vid Stockholm, Kungsholmsfort och Kungsvik. Beroende på vattenivåns variation finns olika metoder för justering. Områden med små variationer av vattennivå lämpar det sig bäst utan någon som helst justering av flytläget. Områden med inte för stora tidvattensförändringar bör justeras med ett system bestående av vinsch, växellåda med en utväxling på 10 000:1, en 12 V DC motor, ett skötselfritt 12 V batteri, en luftlindad linjärgenerator och en trådtöjningsgivare. Områden med stora variationer i tidvatten behöver en avlastning för motorn i form av en fjäder och dämpare. De monteras horizontellt inuti bojen för att skyddas från den yttre miljön. Den statistiska analysen påvisade de största vattennivåändringarna vid både Kungsviks och Kungsholmsforts mätstationer, båda uppvisade ett intervall på 1,6 m mellan minimum och maximum. Kungsvik var den station med de största dagliga variationerna, detta på grund av tidvattnets påverkan i området. / This thesis gives examples of different methods of automated adjustment of floatation level for a static moored buoy, an overview of the theories behind water level change and a statistical analysis of the water level changes for Stockholm, Kungsholmsfort and Kungsvik. Depending on the range and frequency of the water level change different methods of adjustment are recommended. For areas with small changes in sea level the best choice would be no adjustment of the floatation level. Areas that are influenced by moderate tidal ranges should incorporate a system of regulation consisting of a winch, gearbox with a gear ratio of around 10,000:1, 12 V DC motor, 12 V maintenance free battery, air coiled linear generator and a strain gauge. For areas with large tidal ranges the previous system should be complimented with a horizontally mounted spring, inside the buoy, to lessen the loads on the motor. The statistical analysis found the largest extremes in water level of the three sites to be at Kungsvik and Kungsholmsfort, both exhibiting a range of almost 1.6 m. Kungsvik was the station with the largest daily variations, this is because this is the only station influenced by tidal variations.

Climate change is a critical global issue that continues to shape the way we understand and interact with the world around us. It is discussed more than ever before, especially in politics. To slow down the temperature rise of our planet, decreasing the amount of green house gas emissions produced by our way of living, industries, and the production of energy is necessary. Ocean Harvesting Technologies (OHT), a company from Sweden based in Blekinge, is currently developing a new iteration of renewable, wave energy converters (WEC) that they claim to be ecient from both an energy and cost perspective. A new prototype is in development where thermal and fluid characteristics inside the WEC during operation, are important aspects that need to be evaluated. This project is aimed to develop a computational simulation model of the WEC and perform simulations in order to evaluate the cooling and heating performance of the current model that is under development. The methodology used for this project was divided into three stages to streamline the work: steady-state stationary conjugate heat transfer(CHT) simulations, and transient airflow simulations with motion and compressible air, that are combined into a full-system transient CHT model for operational conditions. CAD models and delimi- tations were provided by OHT and the model was broken down, simplified and assessed to begin the work. The computational software used for the simulations in this project was STAR-CCM+ and the complete process of pre-processing, simulation setup/run and post-processing was executed using the same software. To simulate the fluid and the oper- ational motion of the WEC, the Overset mesh methodology was used, and to resolve the turbulent flow, URANS k! SST was used in the solver. The thermodynamic simulations were initially set up and simulated in two sub-models in order to speed up the method development and to get an early indication of the performance of the WEC. The first sub-simulation handled the compressible air together with the Overset mesh motion while the second simulation aimed to model the thermodynamics of the generator components, ball screw, and other solids. Since OHT is in a relatively early development phase, no experimental data could be used for validation, however, data sheets for generator com- ponents and simple handbook calculations were used to validate the simulation models performance. The sub-simulations resulted in an ecient simulation strategy and a lot of knowledge and understanding of the system performance was gained to implement in the full-system model The final outcome of this thesis work was a complete CHT model that showed the ca- pability of running several hundreds of seconds of operational time while producing a significant amount of performance data such as temperature profiles of critical parts, air pressure/temperature fluctuations, and drag losses of the complete WEC. Furthermore, the sub-simulation models can be used individually as stand-alone models in order to op- timize the system on a component level, e.g., drag losses from the generator components during motion.

The Complimentary Energy Decision Support Tool (CEDST) was conceived to be a renewable energy calculator designed specifically for rural sites and agricultural operations in Ontario, though could easily assess urban sites as well, and equipped with the ability to compare the feasibility of different technologies. The Wind Energy Calculator (WEC) component of the CEDST project was the focus of this thesis and was developed since research revealed no current wind prediction tools that met CEDST needs. Verification of WEC predictions found prediction accuracy to have bounds of +/- 60% on actual turbine energy production and was equivalent to the actual generation for 21% of cases. The discrepancy could have resulted from unusual annual wind speeds, which had no significant impact on project economics when analysed. Many cases revealed that 10 kW turbines are not feasible projects under the Feed-in Tariff program and that turbines begin to become economical around 35 kW. / University of Guelph, Natural Sciences and Engineering Research Council of Canada (NSERC), the Poultry Industry Council (PIC), Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), and Egg Farmers of Ontario

Cette thèse porte sur le développement d'un ensemble d'outils numériques destinés à simuler différents aspects des interactions vagues-structure appliquées à l'exploitation des systèmes de récupération de l'énergie des vagues (SREV). Elle a été réalisée dans le cadre du projet ANR Monacorev (projet ANR11-MONU-018-01, 2012-2015).L'objectif est de pouvoir traiter la question des interactions à l'échelle d'une ferme de SREVs (≈ 1 km), et d'étudier l'impact d'une ou plusieurs fermes de SREVs à l'échelle régionale (≈ 10km) sur le champ de vague total. Des méthodes de modélisation et de simulation adaptées sont développées pour chacune de ces deux échelles. Jusqu'à présent, les interactions entre les SREVs étaient bien souvent étudiées en considérant que le fond était plat (l'influence d'un fond variable sur le champ de houle au niveau de la ferme étant alors jugé négligeable), ce qui permet de calculer facilement et rapidement le champ de vagues et les interactions grâce à l'utilisation de la théorie linéaire potentielle. Une application pratique de cette méthode est le calcul du rendement d'une ferme de SREVs, et l'optimisation de leurs positions relatives au sein d'un parc. Dans le cadre de la théorie linéaire, cette thèse propose une méthodologie de couplage originale entre un code de tenue à la mer (Aquaplus) et un code de propagation de la houle en zone côtière (Artemis), laquelle a été développée et qualifiée. Les simulations réalisées montrent que, pour une configuration de ferme de SREVs donnée, on ne peut pas toujours négliger les effets de la bathymétrie. Par exemple, la présence d'une plage de pente 10% au large d'une ferme de SREV peut modifier la hauteur des vagues de manière significative, et affecter ainsi le rendement de la ferme de manière significative par rapport au cas où le fond est uniformément plat. A l'échelle côtière régionale, il est aussi intéressant de simuler et prédire l'impact de fermes de SREVs sur le champ de vagues. Pour des raisons d'efficacité, une approche à phases moyennées de modélisation des vagues a été privilégiée, fondée sur le code spectral d'états de mer Tomawac. La représentation des effets d'un SREV à travers l'utilisation d'un terme puits (concept permettant de soustraire au spectre d'énergie d'état de mer local l'énergie correspondant à celle absorbée par le SREV), bien qu'incomplète du fait que les effets de radiation/diffraction ne sont pas pris en compte, a été étudiée et testée. Une nouvelle méthodologie prenant en compte ces effets dans un code spectral est présentée ici et testée, avec l'objectif de pallier à ces limitations. Les discussions sur la validité de deux approches permettent d'esquisser des pistes de développements ultérieurs pour la représentation des fermes de SREV à l'échelle régionale / This thesis focuses on the development of a set of numerical tools to simulate different aspects of the wave-body interactions applied to the exploitation of wave energy converters (WEC). It was conducted under the ANR Monacorev project (project-ANR11 MONU-018-01, 2012-2015).The objective is to address the issue of the interactions at the scale of a farm of WECs (≈ 1 km), and to study the impact of one or more WEC farms at the regional scale (≈ 10km ) on the total wave field. Modeling and simulation methods adapted for each of these two scales are developed. Until now, the interactions between WECs was often studied by considering that the bottom was flat (the influence of a variable bathymetry on the wave field at the farm site being considered to be negligible), allowing to easily and quickly calculate the wave field and interactions through the use of linear potential theory. A practical application of this method is the yield estimation for a WEC farm and the optimization of the WEC position within a park. In the framework of the linear theory, this thesis proposes an original coupling methodology between a seakeeping (Aquaplus) and a wave propagation code in coastal areas (Artemis), which was developed and qualified. Simulations show that, for a given WEC farm configuration, effects of the bathymetry cannot systematically ignored. For example, the presence of a 10% slope close to a WEC farm can significantly modify the wave height, and thus affect the performance of the farm by several percent compared to the case with a uniformly flat bottom. At the regional coastal scale, it is also interesting to simulate and predict the impact of WEC farms on the wave field. At this scale, for efficiency reasons, a phase-averaged simulation of waves was preferred, based on the sea state spectral code TOMAWAC. The representation of the effects of a WEC through the use of a sink-term (concept for subtracting the energy equivalent to that absorbed by the WEC to the sea state energy spectrum), though incomplete due to the fact that the scattering effects are not taken into account, has been studied and tested. A new methodology taking into account these effects in a spectral code is presented here and tested with the aim to overcome these limitations. Discussions on the validity of these approaches allow us to propose possible future developments for the modeling of WEC farm at the regional scale