Design and Analysis of a Novel Wave Energy Converter with a Tension Leg Platform and Oscillating Proof Masses

Design and Analysis of a Novel Wave Energy Converter with a Tension Leg Platform and Oscillating Proof Masses
Author: Franklin J. Zhang
Publisher:
Total Pages: 0
Release: 2022
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A design of novel wave energy converter with an oscillating proof mass and an electromagnetic power takeoff mechanism was considered. The wave energy converter has two parts, a tension leg platform connected by tether lines to the sea floor and inside of it, proof mass oscillators with motions which are coupled to those of the tension leg platform. In order to simplify the analysis, the system was constrained to only oscillate in the direction of surge. Complex hydrodynamic forces caused by ocean waves will excite the system and the surge motion of the proof mass relative to the tension leg platform will generate power via the electromagnetic power takeoff mechanism. First a model of the system with a linear restoring force exerted on the proof mass is analyzed using linear theory. Following the development of the linear theory, a more complex model with a nonlinear restoring force was considered. Using both a frequency-domain approach and a time-domain simulation, the average power of these systems were calculated. To further maximize power, a control circuit and control law are introduced which increase the average power by multiple factors. By introducing nonlinear restoring force and a control law, the performance of the system was shown to be further improved.

Design and Analysis for a Floating Oscillating Surge Wave Energy Converter

Design and Analysis for a Floating Oscillating Surge Wave Energy Converter
Author:
Publisher:
Total Pages: 11
Release: 2014
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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.

Preliminary Analysis of an Oscillating Surge Wave Energy Converter with Controlled Geometry: Preprint

Preliminary Analysis of an Oscillating Surge Wave Energy Converter with Controlled Geometry: Preprint
Author:
Publisher:
Total Pages: 0
Release: 2015
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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.

Design Load Analysis for Wave Energy Converters: Preprint

Design Load Analysis for Wave Energy Converters: Preprint
Author:
Publisher:
Total Pages: 0
Release: 2018
Genre:
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This study demonstrates a systematic methodology for establishing the design loads of a wave energy converter (WEC). The proposed design load methodology incorporates existing design guidelines, where they exist, and follows a typical design progression; namely, advancing from many, quick, order-of-magnitude accurate, conceptual stage design computations to a few, computationally intensive, high-fidelity, design validation simulations. The goal of the study is to streamline and document this process based on quantitative evaluations of the design loads' accuracy at each design step and consideration for the computational efficiency of the entire design process. For the WEC, loads, and site conditions considered, this study demonstrates an efficient and accurate methodology of evaluating the design loads.

Development of the Second-Generation Oscillating Surge Wave Energy Converter with Variable Geometry: Preprint

Development of the Second-Generation Oscillating Surge Wave Energy Converter with Variable Geometry: Preprint
Author:
Publisher:
Total Pages: 0
Release: 2017
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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.

Conceptual Design of Wave Energy Converters

Conceptual Design of Wave Energy Converters
Author: Kush Bubbar
Publisher:
Total Pages:
Release: 2018
Genre:
ISBN:

Despite presenting a vast opportunity as a renewable energy resource, ocean wave energy has yet to gain commercial success due to the design space being divergent. To facilitate convergence, this dissertation has proposed a method using the mechanical circuit framework to transform a linear representation of any wave energy converter into an equivalent single body absorber, or canonical form, through the systematic application of Thévenin's theorem. Once the canonical form for a WEC has been established, criteria originally derived to maximize power capture in single body absorbers is then applied. Through this process, a master-slave relationship was introduced that relates the geometry and PTO parameters of a wave energy converter device to one another and presents a new method to establish the best possible power capture in analytical form based on dynamic response. This method has been applied to reprove the power capture limits derived by Falnes and Korde for their point absorber devices, and proceeds to introduce a new analytical power capture limit for the self-reacting point absorber architecture, while concurrently establishing design criteria required to achieve the limit. A new technology, the inerter, has been introduced as a means to implement the design criteria. The method has been further developed to establish the generic optimal phase control conditions for complex WEC architectures. In doing so, generic equations have been derived that describe how a geometry control feature set is used to satisfy the required optimal phase criteria. Finally, this dissertation has demonstrated that applying this method with a generic reactive force source enacting the geometry control establishes analytical optimal conditions on the force source to achieve optimal power capture. This work revealed how the analytical equations defining the optimal force source reactance derived in this dissertation for self-reacting point absorbers represents a tangible design constraint prior to specifying how that constraint must be satisfied. As the force source is generic and conceptual, substitution with a physical embodiment must adhere to this constraint thus, steering technology innovation.