scholarly journals A Wave Energy Converter Design Load Case Study

2019 ◽  
Vol 7 (8) ◽  
pp. 250 ◽  
Author(s):  
van Rij ◽  
Yu ◽  
Guo ◽  
Coe
Keyword(s):  
Wave Energy ◽  
Domain Boundary ◽  
Wave Energy Converter ◽  
High Fidelity ◽  
Energy Converter ◽  
Design Load ◽  
Highly Nonlinear ◽  
Extreme Response ◽  
Design Loads ◽  
High Fidelity Simulations

This article presents an example by which design loads for a wave energy converter (WEC) might be estimated through the various stages of the WEC design process. Unlike previous studies, this study considers structural loads, for which, an accurate assessment is crucial to the optimization and survival of a WEC. Three levels of computational fidelity are considered. The first set of design load approximations are made using a potential flow frequency-domain boundary-element method with generalized body modes. The second set of design load approximations are made using a modified version of the linear-based time-domain code WEC-Sim. The final set of design load simulations are realized using computational fluid dynamics coupled with finite element analysis to evaluate the WEC’s loads in response to both regular and focused waves. This study demonstrates an efficient framework for evaluating loads through each of the design stages. In comparison with experimental and high-fidelity simulation results, the linear-based methods can roughly approximate the design loads and the sea states at which they occur. The high-fidelity simulations for regular wave responses correspond well with experimental data and appear to provide reliable design load data. The high-fidelity simulations of focused waves, however, result in highly nonlinear interactions that are not predicted by the linear-based most-likely extreme response design load method.

Design Load Analysis for Wave Energy Converters

2018 ◽  
Author(s):  
Jennifer van Rij ◽  
Yi-Hsiang Yu ◽  
Ryan G. Coe
Keyword(s):  
Wave Energy ◽  
Design Guidelines ◽  
Wave Energy Converter ◽  
Energy Converter ◽  
Stage Design ◽  
Design Load ◽  
Wave Energy Converters ◽  
Order Of Magnitude ◽  
Design Loads ◽  
Computationally Intensive

This study demonstrates a systematic methodology for establishing the design loads of a wave energy converter. 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 wave energy converter, loads, and site conditions considered, this study demonstrates an efficient and accurate methodology of evaluating the design loads.

scholarly journals Study of Snap Loads for Idealized Mooring Configurations with a Buoy, Inextensible and Elastic Cable Combinations for the Multi-Float M4 Wave Energy Converter

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2818
Author(s):  
Peter Stansby ◽  
Efrain Carpintero Moreno
Keyword(s):  
Wave Energy ◽  
Dry Weight ◽  
Wave Energy Converter ◽  
Slight Reduction ◽  
Diffraction Radiation ◽  
Energy Converter ◽  
Operational Conditions ◽  
Highly Nonlinear ◽  
Wave Basin ◽  
Mooring Forces

There has been considerable modelling and wave basin validation of the multi-mode, multi-float, moored wave energy converter M4. The 6 float (2 power take off) (PTO) configuration is considered here with mooring from a buoy with light inextensible cables. Large mean mooring forces and very large peak or snap forces were measured in large waves while the rotational response about the hinges (for power take off in operational conditions) was predominantly linear. Modelling has been extended with elastic mooring cables connected directly to the base of the bow float and to the buoy. The experimental mean force is input to the linear diffraction/radiation model. The device response is effectively unchanged. The peak mooring force and tensions remain large with direct connection to the base of the bow float but are only slightly greater than the mean forces with elastic cables to the buoy, and an elastic hawser provides a further slight reduction. For the largest waves measured, the force was about 10% of the dry weight of the platform. The idealized efficient modelling may inform more detailed design while efficient methods for determining highly nonlinear mean forces remain to be established.

Design of a Mooring System With Synthetic Ropes for the FLOW Wave Energy Converter

2009 ◽  
Author(s):  
Nuno Fonseca ◽  
Ricardo Pascoal ◽  
Tiago Morais ◽  
Renato Dias
Keyword(s):  
Wave Energy ◽  
Domain Boundary ◽  
Angular Separation ◽  
Development Stage ◽  
Wave Energy Converter ◽  
Design Solution ◽  
Mooring System ◽  
Energy Converter ◽  
Mooring Lines ◽  
Global Cost

Martifer Energia is developing a concept of a wave energy converter (WEC) to be used at near shore locations with water depths starting at around 40m. It is a floating device composed of two bodies connected by a one degree of freedom articulation. The energy is extracted at the articulation by a power takeoff system actuated by the relative motion between the bodies. One of the important components of many WECs is the mooring system, since usually the cost is large compared global cost of the device. In this case the WEC will be moored by a spread mooring that allows the device to weathervane with the environmental loads. The paper presents one design solution for the mooring system investigated during the development stage of the concept. It is composed of four hybrid lines, each one with a segment of nylon rope connected to the floating device and a part of chain that contacts with the sea bottom and ends at the anchor. The wave frequency hydrodynamics are first calculated with a frequency domain boundary element method. The nonlinear cable dynamics problem, which is coupled to the slow drift motions of the floater, is solved in the time domain by a finite difference method. The design considers the climatology of the future area of operation of the prototype. Since the loads on the lines depend on the characteristics of the lines themselves, the design solution is obtained iteratively. Appropriate safety factors are considered. The result is the number of mooring lines, their angular separation, length and diameter of each line component.

scholarly journals Efficient Nonlinear Hydrodynamic Models for Wave Energy Converter Design—A Scoping Study

2020 ◽  
Vol 8 (1) ◽  
pp. 35 ◽  
Author(s):  
Josh Davidson ◽  
Ronan Costello
Keyword(s):  
Wave Energy ◽  
Wave Energy Converter ◽  
Navier Stokes ◽  
High Fidelity ◽  
Linear Potential ◽  
Hydrodynamic Models ◽  
Energy Converter ◽  
Suitable Form ◽  
Computational Fluid Dynamics Cfd ◽  
Converter Design

This review focuses on the most suitable form of hydrodynamic modeling for the next generation wave energy converter (WEC) design tools. To design and optimize a WEC, it is estimated that several million hours of operation must be simulated, perhaps one million hours of WEC simulation per year of the R&D program. This level of coverage is possible with linear potential flow (LPF) models, but the fidelity of the physics included is not adequate. Conversely, while Reynolds averaged Navier–Stokes (RANS) type computational fluid dynamics (CFD) solvers provide a high fidelity representation of the physics, the increased computational burden of these models renders the required amount of simulations infeasible. To scope the fast, high fidelity options, the present literature review aims to focus on what CFD theories exist intermediate to LPF and RANS as well as other modeling options that are computationally fast while retaining higher fidelity than LPF.

scholarly journals CFD design-load analysis of a two-body wave energy converter

2019 ◽  
Vol 5 (2) ◽  
pp. 99-117 ◽  
Author(s):  
Ryan G. Coe ◽  
Brian J. Rosenberg ◽  
Eliot W. Quon ◽  
Chris C. Chartrand ◽  
Yi-Hsiang Yu ◽  
...  
Keyword(s):  
Wave Energy ◽  
Body Wave ◽  
Wave Energy Converter ◽  
Energy Converter ◽  
Design Load ◽  
Load Analysis

scholarly journals The Effect of Environmental Contour Selection on Expected Wave Energy Converter Response

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Samuel J. Edwards ◽  
Ryan G. Coe
Keyword(s):  
Wave Energy ◽  
Reference Model ◽  
Wave Energy Converter ◽  
Contour Method ◽  
Response Analysis ◽  
Extreme Conditions ◽  
Force Response ◽  
Energy Converter ◽  
Extreme Response ◽  
Insight Into

A wave energy converter must be designed to both maximize power production and to ensure survivability, which requires the prediction of future sea states. It follows that precision in the prediction of those sea states should be important in determining a final WEC design. One common method used to estimate extreme conditions employs environmental contours of extreme conditions. This report compares five environmental contour methods and their repercussions on the response analysis of Reference Model 3 (RM3). The most extreme power take-off (PTO) force is predicted for the RM3 via each contour and compared to identify the potential difference in WEC response due to contour selection. The analysis provides insight into the relative performance of each of the contour methods and demonstrates the importance of an environmental contour in predicting extreme response. Ideally, over-predictions should be avoided, as they can add to device cost. At the same time, any “exceedances,” that is to say sea states that exceed predictions of the contour, should be avoided so that the device does not fail. For the extreme PTO force response studied here, relatively little sensitivity to the contour method is shown due to the collocation of the device's resonance with a region of agreement between the contours. However, looking at the level of observed exceedances for each contour may still give a higher level of confidence to some methods.

On the Long-Term Reliability Analysis of a Point Absorber Wave Energy Converter

2017 ◽  
Author(s):  
Jarred Canning ◽  
Phong Nguyen ◽  
Lance Manuel ◽  
Ryan G. Coe
Keyword(s):  
Wave Energy ◽  
Reference Model ◽  
Wave Energy Converter ◽  
Environmental Data ◽  
Energy Converter ◽  
Short Term ◽  
Point Absorber ◽  
Extreme Response ◽  
Term Response

Of interest in this study is the long-term response and performance of a two-body wave point absorber (“Reference Model 3”), which serves as a wave energy converter (WEC). In a previous study, the short-term uncertainty in this device’s response was studied for an extreme sea state. We now focus on the assessment of the long-term response of the device where we consider all possible sea states at a site of interest. We demonstrate how simulation tools may be used to evaluate the long-term response and consider key performance parameters of the WEC device, which are the heave and surge forces on the power take-off system and the power take-off extension. We employ environmental data at a designated deployment site in Northern California. Metocean information is generated using approximately 15 years of data from this site (National Data Buoy Center site no. 46022). For various sea states, a selected significant wave height and peak period are chosen to describe representative conditions. Then, using a public-domain simulation tool (Wave Energy Converter Simulator or WEC-Sim), we generate various short-term time-domain response measure for these sea states. Distribution fits to extreme response statistics are generated, for each bin that represents a cluster of sea states, using the open-source toolbox, WDRT (WEC Design Response Toolbox). Long-term distributions for each response variable of interest are estimated by weighting short-term distributions by the likelihood of the sea states; from these distributions, the 50-year response can be derived. The 50-year response is also estimated using an approximate but more efficient inverse reliability approach. Comparisons are made between the two approaches.

Wave Carpet Optimization via Real Time Hybrid Modeling

2015 ◽  
Author(s):  
Thomas Börner ◽  
M.-Reza Alam
Keyword(s):  
Real Time ◽  
Wave Energy ◽  
Broad Band ◽  
Wave Energy Converter ◽  
Hybrid Modeling ◽  
Computational Domain ◽  
Energy Converter ◽  
Modeling Framework ◽  
Study Results ◽  
Highly Nonlinear

Real time hybrid modeling as a structured approach of implementing a real time control system has been proven as an efficient strategy to assess and optimize wave energy converter. In this paper an existing real time hybrid modeling framework for wave energy converter is reviewed, in which the main problem is divided into multiple sub-domains. Each sub-domain uses a preferred method, e.g. experimentally and/or computationally, which contributes to solve the main initial problem as a whole. An interface including actuators and sensors enables the simultaneously running sub-domains to communicate in a closed control loop in “real time”. Specifically, the entire power takeoff of a novel WEC called the “Wave Carpet”, which is classified as a submerged pressure differential device, is shifted into the computational domain. The interaction of the WEC’s absorber unit with incident waves is left in the experiment due to its highly nonlinear characteristics. An extended setup allows to reveal further optimization potential of the novel converter design as a case study. Results of the converter behavior under variable wave states, and for different characteristics of the simulated PTO units are presented. In particular, the presented results show the expected broad band absorption capability of the Wave Carpet by closer examination of the influence of variable PTO unit resistance coefficients on the total, and also on the individual units’ performance.

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