Download or read book Development of the Second Generation Oscillating Surge Wave Energy Converter with Variable Geometry Preprint written by and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study investigates the effect of design changes on the hydrodynamics of a novel oscillating surge wave energy converter being developed at the National Renewable Energy Laboratory. The design utilizes controllable geometry features to shed structural loads while maintaining a rated power over a greater number of sea states. The second-generation design will seek to provide a more refined control of performance because the first-generation design demonstrated performance reductions considered too large for smooth power output. Performance is evaluated using frequency domain analysis with consideration of a nonideal power-take-off system, with respect to power absorption, foundation loads, and power-take-off torque.

Download or read book Preliminary Analysis of an Oscillating Surge Wave Energy Converter with Controlled Geometry Preprint written by and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of this paper is to present a novel wave energy converter device concept that is being developed at the National Renewable Energy Laboratory. The proposed concept combines an oscillating surge wave energy converter with active control surfaces. These active control surfaces allow for the device geometry to be altered, which leads to changes in the hydrodynamic properties. The device geometry will be controlled on a sea state time scale and combined with wave-to-wave power-take-off control to maximize power capture, increase capacity factor, and reduce design loads. The paper begins with a traditional linear frequency domain analysis of the device performance. Performance sensitivity to foil pitch angle, the number of activated foils, and foil cross section geometry is presented to illustrate the current design decisions; however, it is understood from previous studies that modeling of current oscillating wave energy converter designs requires the consideration of nonlinear hydrodynamics and viscous drag forces. In response, a nonlinear model is presented that highlights the shortcomings of the linear frequency domain analysis and increases the precision in predicted performance.

Download or read book Optimizing Power Generation of a Bottom Raised Oscillating Surge Wave Energy Converter Using a Theoretical Model Preprint written by and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Preliminary sizing of an oscillating surge wave energy converter (OSWEC) is an iterative process that relies on knowledge of the relevant hydrodynamic coefficients for a given geometry. Often, the complex definition of the device geometry requires coefficients to be obtained through experiments or numerical boundary element solvers such as WAMIT. These techniques demand significant user and computational effort, therefore inhibiting the fine scale parametrization of object dimensions. In this study, a theoretical model, originally presented in Michele et al. (2016), is developed and demonstrated to efficiently optimize the power production for an OSWEC device (subjected to certain environmental conditions) with variations in device widths, heights, and distances from the seabed. Assuming negligible device thickness, the OSWEC motions are modelled as a bottom-raised two-dimensional flap in regular waves using potential flow theory formulated in elliptical coordinates. The solutions to this diffraction-radiation problem are obtained using Mathieu functions with appropriate boundary conditions. The resulting potentials are then used to derive frequency-dependent expressions for the added mass and radiation damping coefficients, along with wave excitation magnitude in surge, pitch, and coupled surge-pitch motions. Good agreement in hydrodynamic coefficient curves is shown between the theoretical model and the numerical results obtained from the boundary element-based program WAMIT. The theoretical model is then employed to maximize the time-averaged output power while maintaining or reducing the hinge reaction force, with variations in device dimensions, wave frequency and amplitude.

Download or read book Numerical Model Development of a Variable geometry Attenuator Wave Energy Converter written by Nathan Tom and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Design of a Two Body Wave Energy Converter Featuring Controllable Geometry Preprint written by and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: While the field of wave energy has been the subject of numerical simulation, scale model testing, and precommercial project testing for decades, wave energy technologies remain in the early stages of development and must continuing proving themselves as a promising modern renewable energy field. A wave energy converter (WEC) concept, currently being explored, is hoping to add an extra control option to WEC design is the variable-geometry WEC (VGWEC). These VGWECs attempt to incorporate controllable geometric features to adjust the floating body hydrodynamics to favor either power absorption, load shedding, or other operational goals. These variable geometry components have been proposed to be controlled on a sea-state-to-sea-state or wave-to-wave time scale depending on the force (or toque) and bandwidth limitations of the actuators required to manipulate just the controllable geometric hull features. The opportunities of having control over both the WEC geometry components and the power-take-off (PTO) have the potential to improve overall system performance and reliability if a cost-effective solution can be found for a given WEC architecture. This paper will present the recent developments and results of a VGWEC concept that incorporates variable geometry modules into a two-body WEC. In the proposed VGWEC concept, the variable geometry modules consist of air inflatable bags in the surface float and a water inflatable ring in the subsurface body. The surface float is tethered directly to the subsurface body through tether lines each connected to a separate PTO. Adjusting the geometry of both the surface and subsurface bodies along with the PTO coefficients can be shown to maximize power in design sea states while reducing motion response and PTO forces when transitioning to sea states where rated power is reached and load shedding is prioritized in hopes of increasing the sea state operational map.

Download or read book Design and Analysis for a Floating Oscillating Surge Wave Energy Converter written by and published by . This book was released on 2014 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper presents a recent study on the design and analysis of an oscillating surge wave energy converter. A successful wave energy conversion design requires the balance between the design performance and cost. The cost of energy is often used as the metric to judge the design of the wave energy conversion system. It is often determined based on the device power performance, the cost for manufacturing, deployment, operation and maintenance, as well as the effort to ensure the environmental compliance. The objective of this study is to demonstrate the importance of a cost driven design strategy and how it can affect a WEC design. Three oscillating surge wave energy converter (OSWEC) designs were used as the example. The power generation performance of the design was modeled using a time-domain numerical simulation tool, and the mass properties of the design were determined based on a simple structure analysis. The results of those power performance simulations, the structure analysis and a simple economic assessment were then used to determine the cost-efficiency of selected OSWEC designs. Finally, a discussion on the environmental barrier, integrated design strategy and the key areas that need further investigation is also presented.

Download or read book Study of a Novel Oscillating Surge Wave Energy Converter Preprint written by and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study investigates the performance of an oscillating surge wave energy converter (OSWEC) that utilizes adjustable geometry as a means of controlling the hydrodynamic coefficients, a concept originally proposed by [1]. The body of the device consists of a bottom-hinged solid rectangular frame with five horizontal flaps spanning the interior of the frame. The flaps can rotate independently about their center of rotation within the frame like a large window shutter. Changing the orientation of the flaps alters the hydrodynamic coefficients and natural frequency of the device as well as the ability to shed or absorb structural loads accordingly. This ability may allow the device to operate in a wider range of sea states than other current wave energy converter designs. This paper presents and compares the results of numerical simulations and experimental testing of the OSWEC's response to regular waves with all five of the horizontal fin configurations sharing the same orientation of 0 degrees (fully closed interior) and 90 degrees (fully open). The numerical simulations were performed using WAMIT, which calculates hydrodynamic coefficients using a boundary element method code to solve the linear potential flow problem, and WEC-Sim, a MATLAB-based tool that simulates multibody devices in the time domain by solving the governing equations of motion. A 1:14 scale model of the device was built for experimental evaluation in an 8-m-long, 1-m wide wave tank, which supports a water depth of 0.7 m. The OSWEC motion in different wave conditions was measured with displacement sensors while nonlinear wave-structure interaction effects like slamming and overtopping were captured using a high-speed camera and used to understand differences between the simulation and experiments.

Download or read book Design and analysis for a floating oscillating surge wave energy converter written by Y-H. Yu and published by . This book was released on 2014 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book PERFORMANCE OF A NEAR SHORE OSCILLATING WAVE SURGE CONVERTER WITH VARIABLE FLAP CONFIGURATIONS written by Landon Sugar and published by . This book was released on 2021 with total page 197 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most oscillating wave surge converters (OWSCs) are designed to enter survival mode during energetic wave conditions where they forego the opportunity to extract energy in an attempt to preserve structural integrity. While this is a good tradeoff, it is important that OWSC technology progresses to a point where energy is constantly extracted when waves are present. The OWSC studied here is a variation of a device that was conceptually designed and patented by researchers at the National Renewable Energy Laboratory (NREL) and consists of multiple adjustable vanes that, when opened, allow some of the wave force to pass through the device. Currently, NREL's investigations have been limited to a single OWSC consisting of 4 and 5 adjustable vanes. Therefore, there exists a need to further investigate the performance of this nearshore variable geometry OWSC in various arrangements and configurations. This research analyzes the hydrodynamic response of a 2-vane OWSC, a 4-vane OWSC, and an array of OWSCs in a frequency-domain code, a 2-vane OWSC's power generation capabilities in a wide range of sea states in a time-domain wave energy converter simulation tool, and a fluid flow analysis of the 2-vane OWSC in standard and energetic sea states using computational fluid dynamics (CFD). It was hypothesized that opening the vane angles would significantly and consistently reduce the OWSC's hydrodynamic response to various wave frequencies, its power production capabilities, its oscillatory motions, and the potential for wave slamming. The frequency- and time-domain results indicated that most configurations had consistent and predictable responses, while other configurations were more sensitive to the vane angle changes. The CFD results indicated that opening the vanes led to a reduction in wave slamming. However, the fluid flow became highly unpredictable as the vane angles changed, resulting in incident wave damping, inconsistent OWSC oscillations, and hydraulic jump formation.

Download or read book Design and Analysis for a Floating Oscillating Surge Wave Energy Converter written by Y-H. Yu and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book 2 2 1 410 Significant Cost Reduction Potential for Wave Energy Conversion Devices with Variable Geometry Modules written by and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Technology Commercialization Fund (TCF) award is built upon NREL's previous research exploring a bottom-fixed variable-geometry oscillating surge wave energy converter (VGOSWEC); however, unlike previous investigations, the VGOSWEC will be raised off the sea floor. Researchers believe that advances in offshore pilings and foundations, such as 3D printing, will provide low cost and easily deployable structures. There are several benefits to designing a raised VGOSWEC such as 1) reducing issues with sediment transport and environmental impacts near shore, 2) less expensive deployment and installation as work boats will not risk grounding in shallow water, and 3) deeper water deployments improve the wave resource.

Download or read book Balancing Power Absorption and Fatigue Loads in Irregular Waves for an Oscillating Surge Wave Energy Converter Preprint written by and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of this paper is to describe how to control the power-to-load ratio of a novel wave energy converter (WEC) in irregular waves. The novel WEC that is being developed at the National Renewable Energy Laboratory combines an oscillating surge wave energy converter (OSWEC) with control surfaces as part of the structure; however, this work only considers one fixed geometric configuration. This work extends the optimal control problem so as to not solely maximize the time-averaged power, but to also consider the power-take-off (PTO) torque and foundation forces that arise because of WEC motion. The objective function of the controller will include competing terms that force the controller to balance power capture with structural loading. Separate penalty weights were placed on the surge-foundation force and PTO torque magnitude, which allows the controller to be tuned to emphasize either power absorption or load shedding. Results of this study found that, with proper selection of penalty weights, gains in time-averaged power would exceed the gains in structural loading while minimizing the reactive power requirement.

Download or read book Submerged Pressure Differential Plate Wave Energy Converter with Variable Geometry written by Nathan Tom and published by . This book was released on 2019 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Balancing the Power to Load Ratio for a Novel Variable Geometry Wave Energy Converter with Nonideal Power Take Off in Regular Waves Preprint written by and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work attempts to balance power absorption against structural loading for a novel variable geometry wave energy converter. The variable geometry consists of four identical flaps that will be opened in ascending order starting with the flap closest to the seafloor and moving to the free surface. The influence of a pitch motion constraint on power absorption when utilizing a nonideal power take-off (PTO) is examined and found to reduce the losses associated with bidirectional energy flow. The power-to-load ratio is evaluated using pseudo-spectral control to determine the optimum PTO torque based on a multiterm objective function. The pseudo-spectral optimal control problem is extended to include load metrics in the objective function, which may now consist of competing terms. Separate penalty weights are attached to the surge-foundation force and PTO control torque to tune the optimizer performance to emphasize either power absorption or load shedding. PTO efficiency is not included in the objective function, but the penalty weights are utilized to limit the force and torque amplitudes, thereby reducing losses associated with bidirectional energy flow. Results from pseudo-spectral control demonstrate that shedding a portion of the available wave energy can provide greater reductions in structural loads and reactive power.

Download or read book Investigation of Theoretical Solutions to a Bottom Raised Oscillating Surge Wave Energy Converter OSWEC Through Experimental and Parametric Studies Preprint written by and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experiments were conducted on wave tank model of a bottom raised OSWEC model in regular waves. The OSWEC model shape was a thin rectangular flap, which was allowed to pitch in response to incident waves, about a hinge located at the intersection of the flap and the top of the supporting foundation. Torsion springs were added to the hinge in order to position the pitch natural frequency at the center of the wave frequency range of the wave maker. The flap motion as well as the loads at the base of the foundation were measured. The OSWEC was modeled analytically using elliptic functions in order to obtain closed form expressions for added mass and radiation damping coefficients, along with the excitation force and torque. These formulations were derived and reported in a previous publication by the authors. While analytical predictions of the foundation loads agree very well with experiments, large discrepancies are seen in the pitch response close to resonance. These differences are analyzed by conducting a sensitivity study, in which system parameters, including damping and added mass values, are varied. The likely contributors to the differences between predictions and experiments are attributed to tank reflections, standing waves that can occur in long narrow wave tanks, as well as the thin plate assumption employed in the analytical approach.

Download or read book Numerical Modelling of Wave Energy Converters written by Matt Folley and published by Academic Press. This book was released on 2016-06-14 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

Download or read book Ocean Wave Energy written by Joao Cruz and published by Springer Science & Business Media. This book was released on 2007-12-22 with total page 435 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors of this timely reference provide an updated and global view on ocean wave energy conversion – and they do so for wave energy developers as well as for students and professors. The book is orientated to the practical solutions that this new industry has found so far and the problems that any device needs to face. It describes the actual principles applied to machines that convert wave power to electricity and examines state-of-the-art modern systems.