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.
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
With the need to integrate renewable energy sources into the current energy portfolio and the proximity of many population centers to an ocean coastline, it is pressing that marine energy systems, specifically wave energy converters (WECs), are evaluated as potential solutions for meeting energy needs. In order to best understand power development, economics, grid integration requirements, and other aspects prior to installation, the ability to model these systems computationally is vital to their eventual deployment. However, the research area of WEC array optimization is young, and as such, results from previously implemented optimization methods are both few in number and preliminary in nature. The goal of this research is to investigate the economics of implementing WEC arrays, determine viable cost models, create an optimization framework for WEC arrays that will enable developers to - for the first time - understand the tradeoff between power development and cost for potential WEC arrays, and to explore preliminary systems-level issues, such as WEC layout and device spacing. A genetic algorithm approach that utilizes an analytic hydrodynamic model and introduces the use of an array cost model is presented. The resulting optimal layouts for two studies are then discussed. This work is integral in providing an understanding of device layout and spacing and is a foundational starting point for subsequent and more advanced WEC array optimization research.
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.
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.
Eine umfassende Publikation zu sämtlichen Aspekten der Wellen- und Gezeitenenergie. Wave and Tidal Energy gibt einen ausführlichen Überblick über die Entwicklung erneuerbarer Energie aus dem Meer, bezieht sich auf die neueste Forschung und Erfahrungen aus Anlagentests. Das Buch verfolgt zwei Ziele, zum einen vermittelt es Einsteigern in das Fachgebiet eine Überblick über die Wellen- und Gezeitenenergie, zum anderen ist es ein Referenzwerk für komplexere Studien und die Praxis. Es vermittelt Detailwissen zu wichtigen Themen wie Ressourcencharakterisierung, Technologie für Wellen- und Gezeitenanlagen, Stromversorgungssysteme, numerische und physikalische Modellierung, Umwelteffekte und Politik. Zusätzlich enthält es eine aktuelle Übersicht über Entwicklungen in der ganzen Welt sowie Fallstudien zu ausgewählten Projekten. Hauptmerkmale: - Ausführliches Referenzwerk zu allen Aspekten der interdisziplinären Fachrichten Wellen- und Gezeitenenergie. - Greift auf die neuesten Forschungsergebnisse und die Erfahrung führender Experten in der numerischen und laborgestützten Modellierung zurück. - Gibt einen Überblick über regionale Entwicklungen in aller Welt, repräsentative Projekte werden in Fallstudien vorgestellt. Wave and Tidal Energy ist ein wertvolles Referenzwerk für eine breite Leserschaft, von Studenten der Ingenieurwissenschaften und technischen Managern über politische Entscheidungsträger bis hin zu Studienabsolventen und Forschern.
Wave energy has a higher potential than most of the available ocean energy resources; however, it fluctuates dramatically depending on geographical and temporal baselines. The complexity of wave energy is only exacerbated by that fact that the cycle of creation, transport, and disappearance of wave energy is influenced by a wide variety of factors. This Special Issue of Energies explores the latest developments in wave energy potential, behavior, and extraction. This Special Issue introduces 1) thorough reviews on the status of wave energy development, 2) novel technologies to extract wave energy including wave energy converter design, and 3) latest methodologies applied in analyzing wave energy potentials.
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.
