Nas últimas décadas, a fonte eolielétrica é a que sinaliza maior crescimento mundial dentre as demais. A curva de aprendizagem tecnológica do setor mostra queda do custo entre 15% a 20% a cada 3 anos. Países ativos no setor eólico se esforçam pela meta de 12% de participação na produção elétrica mundial em 2020. A contribuição da geração eolielétrica offshore é fundamental para essa meta, pela proximidade aos centros de carga, com ganhos de eficiência, de escala e reduzido impacto ambiental e visual. Apesar do crescimento do parque gerador nacional em 2006, há carência na produção no curto prazo. Contraditoriamente, há ventos abundantes para geração eolielétrica e o prévio arcabouço industrial que seria necessário para desenvolver o setor. Apesar do incentivo governamental (PROINFA), o setor eólico brasileiro ainda não decolou como esperado. O objetivo deste trabalho é reforçar o debate sobre a importância da diversificação da matriz, em prol da estratégia de segurança do suprimento energético nacional e da redução da emissão de gases de efeito estufa. Em rumo a esse objetivo, são colocados argumentos com abordagem ampla e com abordagem específica. Na abordagem ampla, esta pesquisa propõe uma maior inserção da fonte eólica na matriz elétrica nacional como uma das opções a serem consideradas de maneira mais relevante nas táticas de diversificação da matriz, a exemplo do que já fazem países com maior abundância de gás natural que o Brasil, como o Reino Unido. Sob um ponto de vista específico, a investigação exemplifica possibilidades de contribuição da fonte eolielétrica, na sua versão offshore, para as táticas de diversificação da matriz nacional que se entendem importantes, a exemplo do já fazem países com maior predominância da fonte hidráulica que o Brasil, como a Noruega. O método utilizado para se alcançar o objetivo desta dissertação envolve os seguintes passos: (1) esclarecer quanto aos principais aspectos do setor energético a nível mundial e o problema ambiental que está vinculado à produção de energia por fontes fósseis; (2) esclarecer quanto aos aspectos do desenvolvimento de sistemas eolielétricos onshore no Brasil e no mundo e também do desenvolvimento de sistemas offshore em países de interesse; (3) explorar exemplos de articulação dos sistemas eólicos offshore com projetos de produção de energia fóssil em ambiente marítimo, como forma de produzir sinergia útil a ambos os setores; (4) analisar e debater sobre as propostas do governo brasileiro para o futuro da matriz elétrica do país; (5) propor algumas possibilidades de desenvolvimento de sistemas eólicos offshore no Brasil, partindo de pequenos projetos-piloto. Caso as propostas deste trabalho se tornem realizadas, os resultados para este país líder em energia limpa e renovável seriam: a criação de valor nas operações offshore de produção de energia fóssil, o ganho de aprendizagem sobre a tecnologia eólica, o alívio parcial da oferta energética para centros litorâneos no curto prazo; a racionalização do uso, transporte e dependência externa do gás natural; a dinamização dos Mecanismos de Desenvolvimento Limpo (CDM / MDL) e de novos mercados e empregos para a indústria. / In the last decade wind power source was the fastest-growing energy source. Technological learning curves for this sector fall down by a 15% a 20% rate each 3 years. Countries which are committed with wind power are running after the target of 12% wind into the worlds electrical production by 2020. The contribution of the offshore wind power (OWP) source is fundamental on covering such target, due to the proximity to load centers, efficiency & scale savings and reduced environmental and visual impact. Although the growth of the Brazilian power generation system in 2006, there is a gap on fulfilling demand in the short run. Nevertheless, Brazil has abundance of winds suitable for power generation, as a previous industrial framework, necessary on developing this sector. Even that a governmental program has come (PROINFA), wind power sector has not risen as expected yet. The goal of this thesis is to reinforce the debate about the importance on diversifying the Brazilian power matrix, towards the strategy of energy security supply as the reduction of greenhouse gases emissions. On reaching such a goal, this thesis states arguments by a generic approach and also by a specific approach. In the generic approach, it proposes a larger share for wind into the Brazilian electrical matrix as one of the options that should be considered in a more relevant manner for the tactics of diversifying the electrical matrix, following the example given by countries with larger abundance than Brazil regarding on natural gas production, as it is the case of the United Kingdom. In the specific approach, this investigation exemplifies possibilities of contributions from the OWP for the tactics of diversifying the matrix, following the example given by a country with higher predominance than Brazil regarding on using large hydropower as the main national power source, which is the case of Norway. The method taken for reaching the thesis goal involves the following steps: (1) to clarify on some aspects regarding energy production and its respective environmental problem related to the greenhouse gases emissions;(2) to clarify some aspects about the development of wind energy systems in Brazil and in the world and also some aspects about the development of OWP projects in selected countries; (3) to explore examples of articulation between OWP systems with offshore fossil energy production systems, in order to argue about the synergy that is possible between them; (4) to analyze and debate about the Brazilian governments proposal for the electrical matrix in the long run; (5) to propose some possibilities of developing OWP systems in Brazil, starting by small-scale pilot projects. If the case the propositions of this thesis come true in the future, the earnings for this country, which a world leader in clean & renewable energy, would be the following: value creation into the offshore fossil energy production; growth of learning about the OWP technologies; the partial relief of power supply for the coastal load centers; rationalization on the use, transport and foreign dependence of natural gas resources; pushing dynamics for Clean Development Mechanisms (CDM), as for industrial markets and employment.

Durch Umwandlung unterschiedlichster Formen von Energie in mechanische oder elektrische Energie wird die Menschheit seit Jahrhunderten bei der Umsetzung von Arbeitsprozessen im Alltag und bei der industriellen Nutzung unterstützt. Strömende Medien wie Wasser oder Wind gelten dabei als die ältesten Energielieferanten. Im Rahmen der Dissertation wird das Konzept einer zugspannungsverankerten Plattform für Offshore Windenergieanlagen (WEA) vorgestellt, wobei neben den, für diesen Plattformtyp typischen, vertikalen auch geneigte Verankerungselemente Verwendung finden. Diese Art der Verspannung einer zugspannungsverankerten Plattform, respektive ’Tension Leg Platfrom’ (TLP) ist bisher von keiner Quelle bekannt und stellt ein Alleinstellungsmerkmal dar. Folglich sollen Untersuchungen zum dynamischen Verhalten schwimmender Gründungen für Offshore WEA, im Speziellen zu einer TLP mit vertikalen und geneigten Ankerelementen, im Rahmen dieser Arbeit erstmalig vorgestellt werden. Die Plattform ist ein modular gestaltetes Tragwerk bestehend aus großen Rohren und mit integrierten zylindrischen Auftriebskörpern. Diese erzeugen im Transportzustand der Plattform vom Hafen zum Einsatzort und im Betriebszustand innerhalb eines Windparks den nötigen Auftrieb. Infolge der speziellen Art der Verspannung werden die Bewegungen der TLP durch die, aus den Belastungen resultierenden, Seildehnungen dominiert. Damit stellte die TLP im Vergleich zu anderen schwimmenden Gründungen ein bewegungsarmes System dar. Inhalt der hier vorgelegten Arbeit sind Untersuchungen zum dynamischen Verhalten schwimmender Offshoregründungen, im speziellen einer TLP für Windenergieanlagen. Es wurden unterschiedliche Tragstrukturen für TLP-Systeme entwickelt und im Rahmen von Modellversuchen getestet. Den Kern der Arbeit bildet der Vergleich des dynamischen Tragverhaltens der unterschiedlichen Plattformen unter Berücksichtigung der geometrischen und strukturellen Randbedingungen.

Transportation and installation of offshore wind turbines (Tower, Nacelle and Rotor) is a complete process conducted over several phases, usually in sequence. There are several factors that can turn this process into a challenge. These factors can either be due to offshore site conditions or the technical limitations of the installation vessels. Each project has its own characteristic parameters and requires a unique optimum solution. This paper identifies the dynamics of the installation process and analyzes the effects of each phase on the progression of events.The challenges in wind turbine installations due to offshore environment were investigated, the effects of each were explained and their significances were stressed. Special installation vessels were examined and their technical specifications were analyzed in terms of working conditions, dimensions, service performances, and crane capacities as well as projecting future design trends. Several offshore wind farm projects were analyzed; their installation methods were specified, and compared to each other to determine advantages and disadvantages of different pre-assembly concepts. The durations of the sub-phases of the process were defined in terms of different variables such as site conditions and individual vessel performance. These definitions were used for making time estimations, and conducting further analyses regarding the effects of different site specific parameters on the overall project duration.In conclusion, this study considered the main operation parameters in an offshore wind turbine installation context: the benefits and drawbacks of different pre-assembly methods were researched and evaluated resulting in new knowledge and a productive contribution for optimizing “the offshore turbine transportation and installation process”, based on actual time usage.

Mathematical modeling and simulations of a submerged renewable storage system integrated to a wind farm, chosen based on the geographical and wind conditions at the Baltic Sea, gives insight on the feasibility of the submerged renewable storage and an approximation of the payback period and profits that could be generated. Genetic Algorithms were used to obtain the optimal number of spheres for a certain depth, based on 2 objective functions I.e. Minimum Life Cycle Cost (LCC) and maximum reduction in wind curtailment. The new arrangement concept shows that the Initial Capital Cost (ICC) could be decreased by 25% to 60% depending upon the number of sphere employed. Based on the inputs considered in the study, the results prove that the submerged renewable storage system would be feasible, and the profits ranging from 15 Million Euro to 29 Million Euro can be achieved at the chosen location, towards the Swedish side of the Baltic sea. Although, in a real life scenario it is assumed that only up to half of the profits obtained in the results would be achievable. The results also show that, the Pump/Turbine with a high turbine efficiency and lower pump efficiency, generated better profits, compared to a Pump/Turbine running with a higher pump efficiency and lower turbine efficiency. An attempt to increase the round-trip efficiency by adding a multi stage submersible pump, resulted in additional ICC and LCC, which saw a decrease in profits.

Co-location of offshore wind turbines at sites being developed for tidal stream arrays has been proposed as a method to increase capacity and potentially reduce the cost of electricity compared to operating either technology independently. This research evaluates the cost of energy based on capital expenditure and energy yield. It is found that, within the space required around a single 3 MW wind turbine, co-location provides a 10-16% cost saving compared to operating the same size tidal-only array without a wind turbine. Furthermore, for the same cost of electricity, a co-located farm could generate 20% more yield than a tidal-only array. These results are based on analysis of a case-study site in the Pentland Firth. Wind energy is assessed using an eddy viscosity wake model in OpenWind, with a 3 MW rated power curve and thrust coefficient from a Vestas V90 turbine. Three years of wind resource data is from the UK Met Office UK Variable (UKV) 1.5 km numerical model and corrected against a 400 m Weather Research and Forecasting (WRF) model run over the site. Tidal stream energy is modelled using a semi-empirical superposition of self-similar plane wakes, with a generic 1 MW rated power curve and thrust based on a full-scale, fixed-pitch turbine. Coincident tidal resource data is from the Forecasting Ocean Assimilation Model (FOAM) at 7.5 km resolution and correlated with a 150 m ADvanced CIRCulation model (ADCIRC). Wave parameters are corrected from ERA-Interim data with six months of wave buoy data. Multiple tidal turbine array layouts are considered, with maximum tidal energy generated for a staggered array with spacing of 20 tidal turbine diameters, Dt , streamwise and 1.5Dt cross-stream. However, cheapest cost of electricity from the tidal-only array, was found for a single row of turbines, due to minimal wake effects. Laboratory experiments were undertaken to validate the superposition wake model for use with large, shared support structures. Two rotors mounted either side of a central tower generate a peak wake velocity deficit 70% greater than predicted by superposition. This was due to high local blockage and a complex near-wake structure, with a corresponding increase in tower drag of 9%. Further experiments evaluated the impact of oblique inflow on turbines yawed at +/-15 degrees. These results validated a theoretical cosine correction for thrust coefficient and characterised the centreline wake drift with downstream distance. Extreme environmental loads for a shared support structure, compared to structures for wind-only and tidal-only, have also been modelled. A non-linear wave model was used to represent a single wave form with 1% occurrence for each hour of time-series data. Overturning moment about the base of a shared support, with one wind and two tidal turbines, was found to be 4.5% larger than for a wind-only turbine in strong current and with turbines in different operational states. Peak loads across the tidal array were found to vary by 2.5% and so little load reduction benefit could be gained by locating a shared support in a more sheltered area of the array.

Floating offshore wind power is a relatively new technology that enables wind turbines to float above the sea level, tied by anchors at the seabed. The purpose of this work is to develop an economic model for the technology in order to calculate the total cost of a planned wind farm. Cost data are retrieved from reports and academic journals available online. Based on these data, a model in Microsoft Excel is developed which calculates the Levelized cost of energy (LCOE) for floating wind power plants as a function of several input values. As an addition to this model, financing offshore projects are described using literature study and by doing interviews with three major companies, currently investing in offshore wind. As a result, the model allows the user to calculate Capital expenditures, Operating expenditures and LCOE for projects at any given size and at any given site. The current LCOE for a large floating offshore wind farm is indicated to be in the range of 138-147 £/MWh. The outline from interviews was that today there is no shortage of capital for funding wind projects. However, in order to attract capital, the governmental regulatory of that market has to be suitable since it has a crucial impact on price risks of a project.

L’intégration massive de la production d’énergie éolienne intermittente au niveau des réseaux électriques pose un problème de stabilité du système électrique. En effet les caractéristiques sont très différentes de celles de sources conventionnelles maîtrisées par les gestionnaires de réseau. Par conséquent, l’injection de cette énergie induit de nouveaux challenges pour les gestionnaires de réseaux électriques. De plus, les conditions de raccordement évoluent et tendent à ce que toutes les sources participent aux services rendus aux systèmes électriques. Les travaux de cette thèse sont focalisés sur la proposition d’une nouvelle stratégie de commande non-linéaire basée sur la commande par « platitude à une boucle » d’un système de conversion d’énergie éolienne. Cette stratégie de contrôle vise la gestion des interactions au point de connexion par la génération et le suivi de trajectoires de références. De par le fait que toutes les variables du système sont liées à la « sortie plate » de ce système, cette commande procure une rapidité de réponse et une bonne maitrise des régimes transitoires. La mise en œuvre de cette nouvelle stratégie de contrôle pour la constitution d’un parc éolien offshore, capable de satisfaire différentes conditions de raccordement a été simulée avec succès. Plus particulièrement, l’évaluation de l’impact de différents défauts du réseau sur les services proposés (Régulation de fréquence et de tension, la tenue aux creux de tension.) a été réalisée. / The massive integration of intermittent production of wind energy in electrical networks creates an electrical system stability problem. Indeed, its characteristics are very different from those of conventional sources controlled by Grid managers. Therefore, the injection of this energy makes new challenges for power Grid operators. Moreover, the connection conditions are evolving and go towards the situations that all different sources participate into services of electrical systems. This thesis proposes a new nonlinear control strategy based on a « one loop flatness control » of a wind energy conversion system. This control strategy has aim of energy interactions management at the connection point through generation and tracking of reference trajectories. As all system variables are functions of the « flat output » of the system, this control provides fast response and good control in transient state. The application of this new control strategy into an offshore wind farm which is able to satisfy different connection conditions was simulated successfully. Specifically, effects of various grid faults on the proposed ancillary services (frequency and voltage regulation, and low-voltage ride through capabilities) were performed.

Le gouvernement français s'est engagé sur un ambitieux objectif de développer l'éolien offshore pour atteindre une capacité de 6 GW d'ici 2020. La construction d'éoliennes terrestres, tout comme les éoliennes offshore, est très contestée en raison de leur impact visuel sur le paysage. Dans la région française du Languedoc Roussillon, les acteurs concernés (industrie touristique, commerces, pêcheurs, élus locaux), craignent que la construction de parc éoliens offshore aie des effets néfastes sur le tourisme, en donnant à la région une image industrialisée et « bétonnée ». Jusqu'à présent, en mer du Nord, il n'a jamais été mis en évidence que la construction de parcs éoliens offshore ait réellement affecté l'attractivité touristique des côtes environnantes. On peut se demander si ce constat peut être extrapolé à la cote méditerranéenne. Depuis une dizaine d'années, lorsqu'ont débuté les débats sur la possibilité d'exploiter les vents méditerranéens, beaucoup de préjugés sont apparus sur l'impact potentiel négatif que cela pourrait avoir sur le tourisme. La réticence a d'autant plus augmenté lorsque le Languedoc Roussillon a été inclus dans le zonage de l'appel d'offre concernant la construction de 2 GW de parcs éoliens.Il était donc pertinent de mener une enquête auprès des touristes du littoral pour évaluer comment l'installation de parcs éoliens, installés à des distances réalistes des côtés, pourrait affecter le tourisme balnéaire. Par ailleurs, il était également intéressant de proposer des stratégies que les stations balnéaires pourraient adopter pour augmenter le nombre de touristes et leurs profits, avec ou sans parc éolien. Pour répondre à ces questions, une enquête d'évaluation mobilisant la méthode des « choice experiment », a été réalisée durant l'été 2010, auprès de plus de 350 touristes, sur les plages languedociennes.Les résultats de cette enquête, présentés au chapitre 3, montrent que les coûts liés à la nuisance visuelle s'annulent lorsque le parc éolien est installé à des distances comprises entre 8 et 12 km de la côte. L'enquête a également mis en évidence une forte demande pour la mise en place de démarches éco responsable (favorisant les produits locaux, le vélo, les transports publics et les économies d'eau et d'énergie) par les stations balnéaires. Ainsi, nos résultats montrent que la nuisance vécue par l'installation d'un parc à 8 km de la cote serait compensée par la mise en place simultanée d'une « démarche verte ». Par ailleurs, la construction de récifs artificiels associé au parc éolien, qui permettrait l'accès à des loisirs récréatifs (plongée sous marine par ex.) générerait, d'après nos résultats, une augmentation des dépenses des touristes, si ce parc était installé à une distance d'au moins 5 km de la côte.De nos résultats émergent deux principaux constats :- L'implantation d'une éolienne à 12 km de la côte, sans aucune évolution de la station par ailleurs, n'aurait pas d'incidence négative sur le tourisme.- Si la station balnéaire met simultanément en place des actions environnementales et des activités récréatives, le parc éolien peut alors être conçu à partir d'une distance de 5 km de la côte.L'écart entre le Consentement à Payer pour un bien et le Consentement à Recevoir une compensation pour renoncer à ce même bien est un phénomène très largement mis en évidence en économie de l'environnement. Dans une seconde partie de la thèse, nous prenons en compte dans nos estimations économétriques cet écart entre les pertes et des gains dans la fonction d'utilité. En tenant compte de cette asymétrie, nous estimons une réduction de moitié de la nuisance vécue par rapport aux éoliennes si le parc éolien est déjà installé. D'un autre côté, les bénéfices liés aux activités récréatives et à une démarche éco responsable sont perçu comme plus élevés si ces activités étaient déjà mises en place. / The French government has committed itself to an ambitious target of boosting the offshore wind power capacity to reach 6 GW by 2020. Wind turbines onshore as well as offshore are highly contested on visual grounds. Affected stakeholders, ranging from business and property owners, fishermen and elected municipal planners, fear significant negative economic impacts on their ‘business' or their ‘property'. In the French Mediterranean region of the Languedoc Roussillon, the expectation is that the tourist industry will be chagrined in the presence of an offshore wind farm – giving a windy and cemented image of the region. Since talks began about 10 years ago, on the potential for ‘harvesting' the winds of the Mediterranean Sea, many postulates have been made with regard to the impact on coastal tourism. In particular, resistance mounted when plans to include the Languedoc Roussillon in the 2011 tender for the construction of 2 GW wind power capacity were materialising. In this light, it was considered of pertinence to investigate how offshore wind farms, installed at realistic distances from the coast (5, 8 or 12 km), would affect coastal tourism. Additionally, it was considered of interest to help define strategies that coastal community resort may adopt to boost visiting numbers or profit margins with or without wind farms. To answer these questions a full-scale choice experiment valuation survey with over 350 tourists was undertaken in the summer of 2010 on Languedoc beaches.Our survey results show (in chapter 3) that average visual disamenity costs tends to zero, when an offshore wind farm is installed somewhere between 8 and 12 km from the shore. We also find that there is considerable demand for “sustainable” coastal community resorts that favours local produce, bicycling, public transport, energy and water saving devices. Thus, our estimates show that a wind farm installed 8 km from the shore could be ‘compensated for' through the simultaneous ‘greening' of the coastal community resort. If in addition a wind farm is associated with artificial reefs and recreational user access, our results point to an actual rise in tourist related revenues when the wind farm is located min. 5 km from the coast. The policy recommendation is thus two fold: Everything else equals, a wind farm located 12 km offshore will have no negative incidence on tourism. With simultaneous application of a coherent environmental policy and wind farm associated recreational activities, wind farm siting can be conceived from 5 km and outwards.In a latter stage (chapter 5) we explicit account for the well-established fact that humans' over-estimate losses compared with equal-sized gains, in our econometric estimations. By incorporating so-called gain-loss asymmetry in the utility function, we observe that the WTP to remove wind farms had they already been installed is half the compensation required to accept their presence during a vacation. The disamenity costs associated with wind farm installation are thus of a significantly smaller magnitude had the wind farms already been installed. On the other hand, the welfare benefits associated with eco-efficiency and wind farm associated recreational activities are larger had they already been invigorated. The verdict is that asymmetry should be accounted for, or at least recognised in stated preference valuation studies that simultaneously use utility increasing and utility decreasing attributes.

The selection of the bulk power transmission technology in offshore wind farms is strongly related to the wind farm size and its distance to shore. Several alternatives can be evaluated depending on the rated power of the offshore wind farm, the transmission losses and the investment cost for constructing the transmission system. However, when is necessary to connect larger and more distant offshore wind farms; the best technological solution tends to the transmission system based on highvoltage and direct-current with line commutated converters (LCC-HVdc). This dissertation proposes the use of diode-based rectifers as a technical alternative to replace the thyristor-based rectifers in an LCC-HVdc link with unidirectional power flow. This alternative shows advantages with regard to lower conduction losses, lower installation costs and higher reliability. Nonetheless, as a counterpart the offshore ac-grid control performed by the thyristor-based HVdc rectifer is no longer available. This lack of control is compensated by using new control strategies over an offshore wind farm composed by wind turbines with permanent-magnet generators and fully-rated converters. The control strategies have been based mainly on the ability of the wind turbine grid-side converter to perform the control of the offshore ac-grid voltage and frequency. The performance has been evaluated by using PSCAD. Wherein, the most common grid disturbances have been used to demonstrate the fault-ride-through capability as well as the adequate steady state and transient response. / Rodríguez D'derlée, JJ. (2013). Control strategies for offshore wind farms based on PMSG wind turbines and HVdc connection with uncontrolled rectifier [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34510 / TESIS

The trend of offshore wind power is bigger and bigger wind turbines. Turbines are now becoming so big that existing installation vessels no longer are feasible and new bigger installation vessels are needed. Ship owners hesitate to order new vessels worried that the rapid turbine growth will continue and make also the new vessels obsolete in a few years. This can create a bottleneck in the offshore wind market.   This thesis assignment attempts to develop a telescopic tower as an alternative way of installing offshore wind turbines. A telescopic tower can decrease overall height and COG during marine installation, giving opportunity to install the largest wind turbines also with existing vessel fleet.   The method for developing the telescopic tower is to first find the main problems and functions of the concept. A design basis based on a 12 MW reference wind turbine is developed. Based on this reference turbine different solutions to the main problems and functions are developed by creative thinking, literature research, modelling, calculations and analysis. A cost/benefit analysis is performed to investigate if there is any economic potential in the developed solution. To complete the study other installation methods and telescopic tower concepts are investigated for benchmark comparison.   The telescopic tower will have two sections. Shoulders are welded to the inner wall of the lower tower. The upper tower fit inside the lower tower and a telescopic mechanism is installed below to lift the assembly as the mechanism climb the shoulders of the lower tower. The telescopic mechanism works much like a pin and hole mechanism used for jack-up rigs. The pins engage/disengage with the shoulders by the movement of linear actuators. The vertical climbing motion is provided by hydraulic cylinders. The power source is an HPU placed on the wind turbine external platform.   To connect the upper and lower tower permanently a friction connection with long slotted holes is used. This connection is developed for assembly of onshore towers in an EU-sponsored project called Histwin. The walls of the lower and the upper tower overlap at the connection and are pressed together by pretensioned bolts to create a friction surface that hold the loads from the upper tower.   The conclusion is that the telescopic tower is technically feasible and can be installed by the existing installation vessel fleet. The economic feasibility is dependent on the specific project characteristics, but there are scenarios where the telescopic tower can have great economical upside.