Abstract : This study explored optimal configuration of both the array layout and the dimension of each WEC in the array. The array contains heaving buoys with full interaction and exact hydrodynamics. Optimization of dimension was done on each WEC in the array with a given optimal layout, and a higher q-factor was achieved. Both impedance matching optimal control and derivative control were employed, which provides both theoretical maximum energy and a more realistic case. Then the work was expanded to optimization of both the array layout and the dimension of each WEC in the array. An average of 39.21% higher q-factor can be achieved with the optimal control and an average of 8.87% higher q-factor can be achieved with the derivative control. Optimization of both the layout of array and the dimension of each WEC was done under irregular wave. The irregular wave was formulated with Bretschneider spectrum. Preliminary results from the irregular wave optimization indicates an asymmetric layout of array is needed.
Abstract : Wave Energy Converter Array is a practical approach to harvest ocean wave energy. To leverage the potential of the WEC array in terms of energy extraction, it is essential to have a properly designed array configuration and control system. This thesis explores the optimal configuration of Wave Energy Converters (WECs) arrays and their optimal control. The optimization of the WEC array allows both dimensions of individual WECs as well as the array layout to varying. In the first optimization problem, cylindrical buoys are assumed in the array where their radii and drafts are optimization parameters. Genetic Algorithms are used for optimization. Three case studies are investigated of different array sizes: 3, 5, and 7 devices in the array. Two types of controls are assumed; the first is the standard impedance matching control while the second is a derivative control. The numerical test cases demonstrate that a higher q-factor is achieved when optimizing the buoys dimensions simultaneously with the array layout. In the conducted test cases, it is shown that optimizing the array layout can increase the q-factor on average by 39.21% when using optimal control, and increase it on average by a factor of 8.87% when using a derivative control. Arrays of wave energy converters (WECs) usually have large spacing between members of the array to avoid negative hydrodynamic interaction between members in the array. Errors in estimating the spacing between members may result in a significant degradation in the performance of the array in terms of the total harvested energy, due to destructive hydrodynamic interaction between members of the array. In this thesis, a hybrid design of wave energy converter arrays, that contains two types of WECs, the heaving buoys, and the floating flap-type devices, is investigated and compared against traditional WEC arrays of heaving buoys. The resulting q-factor is less sensitive to deviations in the spacing from the design layout. This hybrid array, hence, enables more WECs in the same ocean area. The two types of arrays are tested using 40 layouts that have different separation distances ranging from small to large. With the hybrid configuration, the array achieved a variance of the q-factor as low as 0.006. The traditional array has a variance of 0.024 which is four times larger. The optimization is conducted on the hybrid array with both layout and dimension as design variables. The optimal control algorithm for the WEC array is developed using the optimality condition. Devices in the array are assumed to be identical heaving buoys. The optimization objective is to maximize energy extraction at each time step. Both regular and irregular waves are used to excite the array. The unconstrained optimal control problem is solved with saturation on the control force. The solutions show that good wave estimations and sufficient accuracy of the radiation sub-system are the keys to the desired WEC array performance.
Numerical Modelling of Wave Energy Converters: State-of-the Art Techniques for Single WEC and Converter Arrays presents all the information and techniques required for the numerical modelling of a wave energy converter together with a comparative review of the different available techniques. The authors provide clear details on the subject and guidance on its use for WEC design, covering topics such as boundary element methods, frequency domain models, spectral domain models, time domain models, non linear potential flow models, CFD models, semi analytical models, phase resolving wave propagation models, phase averaging wave propagation models, parametric design and control optimization, mean annual energy yield, hydrodynamic loads assessment, and environmental impact assessment. Each chapter starts by defining the fundamental principles underlying the numerical modelling technique and finishes with a discussion of the technique’s limitations and a summary of the main points in the chapter. The contents of the chapters are not limited to a description of the mathematics, but also include details and discussion of the current available tools, examples available in the literature, and verification, validation, and computational requirements. In this way, the key points of each modelling technique can be identified without having to get deeply involved in the mathematical representation that is at the core of each chapter. The book is separated into four parts. The first two parts deal with modelling single wave energy converters; the third part considers the modelling of arrays; and the final part looks at the application of the different modelling techniques to the four most common uses of numerical models. It is ideal for graduate engineers and scientists interested in numerical modelling of wave energy converters, and decision-makers who must review different modelling techniques and assess their suitability and output. Consolidates in one volume information and techniques for the numerical modelling of wave energy converters and converter arrays, which has, up until now, been spread around multiple academic journals and conference proceedings making it difficult to access Presents a comparative review of the different numerical modelling techniques applied to wave energy converters, discussing their limitations, current available tools, examples, and verification, validation, and computational requirements Includes practical examples and simulations available for download at the book’s companion website Identifies key points of each modelling technique without getting deeply involved in the mathematical representation
Wave energy offers a promising renewable energy source, however, technologies converting wave energy into useful electricity face many design challenges. This guide presents numerical modelling and optimization methods for the development of wave energy converter technologies, from principles to applications. It covers the development status and perspectives of wave energy converter systems; the fundamental theories on wave power absorption; the modern wave energy converter concepts including oscillating bodies in single and multiple degree of freedom and oscillating water column technologies; and the relatively hitherto unexplored topic of wave energy harvesting farms. It can be used as a specialist student textbook as well as a reference book for the design of wave energy harvesting systems, across a broad range of disciplines, including renewable energy, marine engineering, infrastructure engineering, hydrodynamics, ocean science, and mechatronics engineering. The Open Access version of this book, available at www.routledge.com has been made available under a Creative Commons Attribution-Non Commercial-No Derivatives 4.0 license.
The book, "Optimization and Energy Maximizing Control Systems for Wave Energy Converters", presents eleven contributions on the latest scientific advancements of 2020-2021 in wave energy technology optimization and control, including holistic techno-economic optimization, inclusion of nonlinear effects, and real-time implementations of estimation and control algorithms.
The book, “Optimization and Energy Maximizing Control Systems for Wave Energy Converters”, presents eleven contributions on the latest scientific advancements of 2020-2021 in wave energy technology optimization and control, including holistic techno-economic optimization, inclusion of nonlinear effects, and real-time implementations of estimation and control algorithms.
With this self-contained and comprehensive text, students and researchers will gain a detailed understanding of the fundamental aspects of the hydrodynamic control of wave energy converters. Such control is necessary to maximise energy capture for a given device configuration and plays a major role in efforts to make wave energy economic. Covering a wide range of disciplines, the reader is taken from the mathematical and technical fundamentals, through the main pillars of wave energy hydrodynamic control, right through to state-of-the-art algorithms for hydrodynamic control. The various operating principles of wave energy converters are exposed and the unique aspects of the hydrodynamic control problem highlighted, with a variety of potential solutions discussed. Supporting material on wave forecasting and the interaction of the hydrodynamic control problem with other aspects of wave energy device optimisation, such as device geometry optimisation and optimal device array layout, is also provided.
Understand the absorption of energy from ocean waves by means of oscillating systems with this useful new edition. Essential for engineers, researchers, and graduate students, and an indispensable tool for those who work in this field.
Abstract : Many governments around the world are pledging to reduce their consumption of fossil fuels as they look to curb the amount of green house gasses they release into the atmosphere. These green house gasses are what scientists blame for global warming and the recent increase in extreme weather events. Producing electricity is one of the largest producers of these gasses but utilizing renewable sources can greatly decrease the amount of green house gasses produced. Common forms of renewable energies are wind and solar and both of these green energies have reached a state of maturation where they are economically viable to implement into full scale electrical grids. Wave energy is a less developed renewable energy and it has not yet reached the level of maturation where it can readily be implemented into the electric grid. Marine energy sources are a promising new source of energy as the majority of Americas population lives along the coast and the energy in water is more energy dense that of solar and wind powers. However, in order to implement full scale wave energy converters there needs to be additional development in wave forecasting, controls systems, power electronics, energy storage systems, grid integration, and the overall efficiency of the system. In this study wave energy converters are modelled from the excitation force of the water interacting with the buoy to the grid current being injected into the onshore electrical grid. The power and the efficiency of the system is analyzed from wave to wire and a control system is implemented to increase the efficiency of the system in a multi-frequency irregular wave environment. Additionally, the positioning of wave energy converters is an array is studied to determine the optimal placement of each buoy in order to maximize the energy delivered to the onshore electrical grid.
The waves that animate the surface of the oceans represent a deposit of renewable energy that for the most part is still unexploited today. This is not for lack of effort, as for more than two hundred years inventors, researchers and engineers have struggled to develop processes and systems to recover the energy of the waves. While all of these efforts have failed to converge towards a satisfactory technological solution, the result is a rich scientific and technical literature as well as extensive and varied feedback from experience. For the uninitiated, this abundance is an obstacle. In order to facilitate familiarization with the subject, we propose in this work a summary of the state of knowledge on the potential of wave energy as well as on the processes and technologies of its recovery (wave energy converters). In particular, we focus on the problem of positioning wave energy in the electricity market, the development of wave energy conversion technologies from a historical perspective, and finally the energy performance of the devices. This work is aimed at students, researchers, developers, industry professionals and decision makers who wish to acquire a global perspective and the necessary tools to understand the field. Reviews the state of knowledge and developments on wave energy recovery Presents the history of wave energy recovery Classifies the various systems for recovering this type of energy
