A wave energy converter has been constructed and its function and operational characteristics have been thoroughly investigated and published. The wave energy converter was installed in March of 2006 approximately two kilometers off the Swedish west coast in the proximity of the town Lysekil. Since then the converter has been submerged at the research site for over two and a half years and in operation during three time periods for a total of 12 months, the latest being during five months of 2008. Throughout this time the generated electricity has been transmitted to shore and operational data has been recorded. The wave energy converter and its connected electrical system has been continually upgraded and each of the three operational periods have investigated more advanced stages in the progression toward grid connection. The wave energy system has faced the challenges of the ocean and initial results and insights have been reached, most important being that the overall wave energy concept has been verified. Experiments have shown that slowly varying power generation from ocean waves is possible. Apart from the wave energy converter, three shorter studies have been performed. A sensor was designed for measuring the air gap width of the linear generator used in the wave energy converter. The sensor consists of an etched coil, a search coil, that functions passively through induction. Theory and experiment showed good agreement. The Swedish west coast wave climate has been studied in detail. The study used eight years of wave data from 13 sites in the Skagerrak and Kattegatt, and data from a wave measurement buoy located at the wave energy research site. The study resulted in scatter diagrams, hundred year extreme wave estimations, and a mapping of the energy flux in the area. The average energy flux was found to be approximately 5.2 kW/m in the offshore Skagerrak, 2.8 kW/m in the near shore Skagerrak, and 2.4 kW/m in the Kattegat. A method for evaluating renewable energy technologies in terms of economy and engineering solutions has been investigated. The match between the technologies and the fundamental physics of renewable energy sources can be given in terms of the technology’s utilization. It is argued that engineers should strive for a high utilization if competitive technologies are to be developed.

This thesis is focused on development of models and modelling of a wave energy converter in operation. Through the thesis linear potential wave theory has been used to describe the wave-buoy interaction. The differences lie in the generator models, in the simplest model the generator is a mechanical damper characterized by a damping factor. In the most advanced generator model the magnetic fields is calculated the by a FE-method, which gives detailed description of the electric properties and the effect it has on the buoy dynamics. Moreover, an equivalent circuit description of the generator has been tested. It has the same accuracy as the field based model but with a strongly enhanced CPU time. All models are verified against full scale experiments. The models are intended to be used for design of the next generation wave energy converters. Further, the developed models have also been used to study what effect buoy geometry and generator damping have on the ability to energy absorption. In the spring 2006 a full scale wave energy converter was installed at the west coast of Sweden. It was in operation and collected data during three months. During that period the load resistance was varied in order to study the effect on the energy absorption. These collected data was then used in the verification of the developed models. In the year 2002 a wave energy project started at Uppsala University; this work is a part of that larger project which intendeds to develop a viable wave energy conversion concept.

This thesis studies the electric aspects of a linear synchronous permanent magnet generator. The generator is designed for use in a wave energy converter, which determines the fundamental requirements of the generator. The electromagnetic properties of the generator are investigated with a finite element based simulation tool. These simulations formed the base of the design and construction of a laboratory prototype. Several experiments where conducted on the prototype generator. The results verify at large the simulation tool. However, a difference between the measured and simulated air gap flux was discovered. This was attributed to the longitudinal ends of the generator, which are ignored in the simulation tool. Experiences from the construction, and further finite element studies, led to a significant change in the support structure of the first offshore prototype generator. A complete wave energy converter was constructed and launched, the 13th of March, on the west coast of Sweden. A study of the load resistance impact on the power absorption has been carried out. An optimal load interval, with regard to power absorption, has been identified. Furthermore, the generator has proofed to withstand short term overload several times larger than the nominal load. Finally, the longitudinal ends’ influence on the flux distribution was investigated with an analytical model, as well as finite element simulations. A possible problem with large induction of eddy currents in the actuator back steel was identified. This work is a part of a larger project, which aims do develop a viable wave energy conversion system.

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.

In this thesis, a model has been developed to analyze the behavior of wave energy converter arrays in the frequency domain. This development serves the purpose of establishing an in-house model tool for array modelling for CorPower Ocean. A literature review has been conducted to compare various modelling approaches and prior studies on different configurations of wave energy converter arrays have been examined. The literature review is followed by theory that includes linear wave theory and the equation of motion. Following this, the model is introduced, accompanied by behavior validation in comparison to similar models. The selected case studies for this thesis are divided into two parts. Firstly, the investigation of different layout configurations with 16 Wave Energy Converters: 1) Circular configuration, 2) Double Circular configuration, 3) Double Row configuration (2x8), 4) Square Grid configuration (4x4), and 5) Randomized layout. The second chosen study case involves investigating layout 3) Double Row configuration (2x8) with four different distances between each Wave Energy Converter, 50, 100, 150, and 200 meters. The results demonstrate the presence of interactions within the wave energy converter arrays. The Double row layout exhibits the largest power outputs but power drops at certain waveperiods were also observed. Additionally, the results of different distances between the Wave Energy Converters demonstrate that larger spacings result in reduced interactions.

This thesis deals with a system for operation of directly driven offshore wave energy converters. The work that has been carried out includes laboratory testing of a permanent magnet linear generator, wave energy converter mechanical design and offshore testing, and finally design, implementation, and offshore testing of an underwater collector substation. Long-term testing of a single point absorber, which was installed in March 2006, has been performed in real ocean waves in linear and in non-linear damping mode. The two different damping modes were realized by, first, a resistive load, and second, a rectifier with voltage smoothing capacitors and a resistive load in the DC-link. The loads are placed on land about 2 km east of the Lysekil wave energy research site, where the offshore experiments have been conducted. In the spring of 2009, another two wave energy converter prototypes were installed. Records of array operation were taken with two and three devices in the array. With two units, non-linear damping was used, and with three units, linear damping was employed. The point absorbers in the array are connected to the underwater substation, which is based on a 3 m3 pressure vessel standing on the seabed. In the substation, rectification of the frequency and amplitude modulated voltages from the linear generators is made. The DC voltage is smoothened by capacitors and inverted to 50 Hz electrical frequency, transformed and finally transmitted to the on-shore measuring station. Results show that the absorption is heavily dependent on the damping. It has also been shown that by increasing the damping, the standard deviation of electrical power can be reduced. The standard deviation of electrical power is reduced by array operation compared to single unit operation. Ongoing and future work include the construction and installation of a second underwater substation, which will connect the first substation and seven new WECs.

A relative motion based heaving point absorber wave energy converter is being co-developed by researchers at the University of Victoria and SyncWave Systems Inc. To that end---this thesis represents a multi-faceted contribution to the development effort. A small scale two-body prototype wave energy converter was developed and tested in a wave tank. Although experimental problems were encountered, the results compare reasonably well to the output of a two degree of freedom linear dynamics model in the frequency domain. A two-body wave energy converter design is parameterized as a basis for an optimization and sensitivity study undertaken to illustrate the potential benefits of frequency response tuning. Further, a mechanical system concept for frequency response tuning is presented. The two degree of freedom model is expanded to three degrees of freedom to account for the tuning system. An optimization procedure, utilizing a Sequential Quadratic Programming algorithm, is developed to establish control schedules to maximize power capture as a function of the control variables. A spectral approach is developed to estimate WEC power capture in irregular waves. Finally, as a case study, the modeling, optimization, and spectral methods are applied to predict performance for a large scale wave energy converter deployed offshore of a remote Alaskan island. Using archived sea-state data and community electrical load profiles, a wave/diesel hybrid integration with the remote Alaskan community power system is assessed to be technologically feasible.

O uso contínuo de combustíveis fósseis já se mostrou deletério há anos, além de ser um meio energético finito. Por este motivo, a demanda atual e futura por sistemas de energia limpa é grande. Muito embora já existam diversas estruturas dedicadas a extrair energia do mar, o conceito em que se pretende trabalhar é inovador e de tecnologia nacional. Este tema foi desenvolvido inicialmente em uma abordagem teórica pelo então aluno de engenharia naval Daniel Prata Vieira e sua colega Ana Luísa Orsolini, como Trabalho Final do curso de Engenharia Naval e Oceânica da Escola Politécnica da USP, orientados pelo Prof. Dr. André Luis Condino Fujarra. Vieira & Orsolini (2011) [1] abordaram de uma forma diferente o tema de geração de energia por ondas do mar, trazendo à tona o uso da já consagrada plataforma monocoluna - protótipo que rendeu diversos prêmios de inventor do ano da Petrobrás, além de patente, ao Tanque de Provas Numérico, laboratório do departamento de engenharia naval da POLI-USP. O trabalho dos alunos Daniel e Ana também foi reconhecido nacionalmente recebendo o Prêmio Petrobras de Tecnologia 2011 no tema de Tecnologia de Energia. A continuação do trabalho consiste em levar a fundo alguns pontos importantes relacionados ao dimensionamento da plataforma para otimizar a geração de energia através do movimento relativo entre ela e um corpo flutuante interno ao seu moonpool. O objetivo do trabalho é definir melhores geometrias através da parametrização das dimensões principais e da utilização de métodos numéricos num estudo mais detalhado e aprofundado. O método de desenvolvimento leva em conta todos os fatores que influenciam na dinâmica do sistema como a hidrodinâmica de dois corpos (plataforma e corpo interno flutuante) e a dinâmica do gerador de energia (tipo de gerador e seu impacto no amortecimento do sistema global). / The continued use of fossil fuels has proved harmful for years, besides being a means finite energy. For this reason, the current and future demand for clean energy systems are great. Although there are already several structures dedicated to extracting energy from the sea, the concept on which it intends to work is innovative and with local technology. This theme has been already developed in a theoretical approach by the student of naval engineering Daniel Prata Vieira and his classmate Ana Luisa Orsolini, such as Final Paper Course of Naval Architecture and Ocean Engineering from the Escola Politécnica of USP, directed by Prof. Dr. André Luis Condino Fujarra. Vieira \\& Orsolini (2010) [1] studied in a different way the theme of energy generation from ocean waves, bringing up the use of already established monocolumn platform - prototype that earned several inventor of the year from Petrobras awards, besides patent, to the Numerical Offshore Tank, laboratory of the Naval Engineering Department of Poli - USP. The work of students Daniel and Ana was also recognized nationally getting the Petrobras Technology Award 2011 in the Energy Technology theme. The continuation of this work is to bring the background some important points related to platform design to optimize power generation through the relative motion between it and an internal floating body into moonpool. The objective is to define best geometries through the parameterization of the key dimensions and the use of numerical methods in a more detailed and in-depth study. The development method takes into account all the factors that influence the dynamics of the system such as the hydrodynamics of two bodies (platform and floating internal body) and the dynamics of the generator (type of generator and its impact on the damping of the global system).

O uso contínuo de combustíveis fósseis já se mostrou deletério há anos, além de ser um meio energético finito. Por este motivo, a demanda atual e futura por sistemas de energia limpa é grande. Muito embora já existam diversas estruturas dedicadas a extrair energia do mar, o conceito em que se pretende trabalhar é inovador e de tecnologia nacional. Este tema foi desenvolvido inicialmente em uma abordagem teórica pelo então aluno de engenharia naval Daniel Prata Vieira e sua colega Ana Luísa Orsolini, como Trabalho Final do curso de Engenharia Naval e Oceânica da Escola Politécnica da USP, orientados pelo Prof. Dr. André Luis Condino Fujarra. Vieira & Orsolini (2011) [1] abordaram de uma forma diferente o tema de geração de energia por ondas do mar, trazendo à tona o uso da já consagrada plataforma monocoluna - protótipo que rendeu diversos prêmios de inventor do ano da Petrobrás, além de patente, ao Tanque de Provas Numérico, laboratório do departamento de engenharia naval da POLI-USP. O trabalho dos alunos Daniel e Ana também foi reconhecido nacionalmente recebendo o Prêmio Petrobras de Tecnologia 2011 no tema de Tecnologia de Energia. A continuação do trabalho consiste em levar a fundo alguns pontos importantes relacionados ao dimensionamento da plataforma para otimizar a geração de energia através do movimento relativo entre ela e um corpo flutuante interno ao seu moonpool. O objetivo do trabalho é definir melhores geometrias através da parametrização das dimensões principais e da utilização de métodos numéricos num estudo mais detalhado e aprofundado. O método de desenvolvimento leva em conta todos os fatores que influenciam na dinâmica do sistema como a hidrodinâmica de dois corpos (plataforma e corpo interno flutuante) e a dinâmica do gerador de energia (tipo de gerador e seu impacto no amortecimento do sistema global). / The continued use of fossil fuels has proved harmful for years, besides being a means finite energy. For this reason, the current and future demand for clean energy systems are great. Although there are already several structures dedicated to extracting energy from the sea, the concept on which it intends to work is innovative and with local technology. This theme has been already developed in a theoretical approach by the student of naval engineering Daniel Prata Vieira and his classmate Ana Luisa Orsolini, such as Final Paper Course of Naval Architecture and Ocean Engineering from the Escola Politécnica of USP, directed by Prof. Dr. André Luis Condino Fujarra. Vieira \\& Orsolini (2010) [1] studied in a different way the theme of energy generation from ocean waves, bringing up the use of already established monocolumn platform - prototype that earned several inventor of the year from Petrobras awards, besides patent, to the Numerical Offshore Tank, laboratory of the Naval Engineering Department of Poli - USP. The work of students Daniel and Ana was also recognized nationally getting the Petrobras Technology Award 2011 in the Energy Technology theme. The continuation of this work is to bring the background some important points related to platform design to optimize power generation through the relative motion between it and an internal floating body into moonpool. The objective is to define best geometries through the parameterization of the key dimensions and the use of numerical methods in a more detailed and in-depth study. The development method takes into account all the factors that influence the dynamics of the system such as the hydrodynamics of two bodies (platform and floating internal body) and the dynamics of the generator (type of generator and its impact on the damping of the global system).