scholarly journals Modelling of a wave energy converter array with non‐linear power take‐off using a mixed time‐domain/frequency‐domain method

2021 ◽  
Author(s):  
Y. Wei ◽  
A. Bechlenberg ◽  
B. Jayawardhana ◽  
A. I. Vakis
Keyword(s):  
Frequency Domain ◽  
Wave Energy ◽  
Time Domain ◽  
Wave Energy Converter ◽  
Frequency Domain Method ◽  
Energy Converter ◽  
Domain Method ◽  
Non Linear

scholarly journals The performance of the Mocean M100 wave energy converter described through numerical and physical modelling

2020 ◽  
Vol 3 (1) ◽  
pp. 11-19
Author(s):  
J. Cameron McNatt ◽  
Christopher H. Retzler
Keyword(s):  
Frequency Domain ◽  
Wave Energy ◽  
Time Domain ◽  
Numerical Models ◽  
Average Power ◽  
Physical Modelling ◽  
Wave Energy Converter ◽  
Domain Model ◽  
Energy Converter ◽  
Cost Of Energy

Mocean Energy has designed a 100-kW hinged-raft wave energy converter (WEC), the M100, which has a novel geometry that reduces the cost of energy by improving the ratios of power per size and power per torque. The performance of the M100 is shown through the outputs of frequency-domain and time-domain numerical models, which are compared with those from 1/20th scale wave-tank testing. Results show that for the undamped, frequency-domain model, there are resonant peaks in the response at 6.6 and 9.6 s, corresponding to wavelengths that are 1.9 and 3.7 times longer than the machine. With the inclusion of power-take-off and viscous damping, the power response as a function of frequency shows a broad bandwidth and a hinge flex amplitude of 12-20 degrees per meter of wave amplitude. Comparison between the time-domain model and physical data in a variety of sea states, up to a significant wave height of 4.5 m, show agreements within 10% for average power absorption, which is notable because only simple, nonlinear, numerical models were used. The M100 geometry results in a broad-banded, large amplitude response due to its asymmetric shape, which induces coupling between modes of motion.

scholarly journals Design and Simulation of a Novel Mechanical Power Take-Off for a Two-Body Wave Energy Point Absorber

2018 ◽  
Author(s):  
Xiaofan Li ◽  
Chien-An Chen ◽  
Qiuchi Xiong ◽  
Robert Parker ◽  
Lei Zuo
Keyword(s):  
Frequency Domain ◽  
Output Power ◽  
Wave Energy ◽  
Time Domain ◽  
Wave Energy Converter ◽  
Mechanical Power ◽  
Total Output ◽  
Test Machine ◽  
Mechanical Motion ◽  
Energy Converter

In this paper, a two-body self-react wave energy converter with a novel mechanical Power Take-off (PTO) is introduced. The PTO rectifies the mechanical motion and regulates the flow with a mechanism called Mechanical Motion Rectifier (MMR), which converts the reciprocating motion of the ocean wave into unidirectional rotation of the generator. The overall system is analyzed in both time and frequency domain. In time domain, the piecewise non-linear dynamic model of the MMR PTO is derived, and parameters that could significantly influence the MMR property is extracted. By building the model into WEC-Sim, a time domain wave energy converter (WEC) simulation tool, to simulate and evaluate the performance of the PTO. In addition, the system is modelled as a two-body vibration system for frequency domain analysis in order to further investigate and optimize the proposed wave energy converter. The tunable parameters within the system, including the equivalent mass, the equivalent damping coefficient, and the PTO stiffness, are discussed based on the criteria of maximization of the total output power. To verify the theoretical analysis, a bench test prototype is developed and tested on a hydraulic test machine. The experimental results in line with the derived model and can be used for reasonable estimation on the output power of the proposed system in real ocean conditions.

Time Domain Modeling and Power Output for a Heaving Point Absorber Wave Energy Converter

2014 ◽  
Author(s):  
Jeremiah Pastor ◽  
Yucheng Liu
Keyword(s):  
Frequency Domain ◽  
Wave Energy ◽  
Time Domain ◽  
Power Output ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Wave Energy Converter ◽  
Energy Converter ◽  
Power Absorption ◽  
Point Absorber

This paper presents, assesses, and optimizes a point absorber wave energy converter (WEC) through numerical modeling, simulation, and analysis in time domain. Wave energy conversion is a technology especially suited for assisting in power generation in the offshore oil and gas platforms. A linear frequency domain model is created to predict the behavior of the heaving point absorber WEC system. The hydrodynamic parameters are obtained with AQWA, a software package based on boundary element methods. A linear external damping coefficient is applied to enable power absorption and an external spring force is introduced to tune the point absorber to the incoming wave conditions. The external damping coefficient and external spring forces are the control parameters, which need to be optimized to maximize the power absorption. Two buoy shapes are tested and a variety of diameters and drafts are compared. Optimal shape, draft, and diameter of the model are then determined to maximize its power absorption capacity. Based on the results generated from the frequency domain analysis, a time domain analysis was also conducted to derive the responses of the WEC in the hydrodynamic time response domain. The time domain analysis results allowed us to estimate the power output of this WEC system.

Dynamic Tilt Correction Using Direct Rotational Motion Measurements

2020 ◽  
Vol 91 (5) ◽  
pp. 2872-2880 ◽  
Author(s):  
Felix Bernauer ◽  
Joachim Wassermann ◽  
Heiner Igel
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Ground Deformation ◽  
Time Domain Method ◽  
Caldera Collapse ◽  
Frequency Domain Method ◽  
Test Cases ◽  
Ground Acceleration ◽  
Data Set ◽  
Domain Method

Abstract Inertial sensors like seismometers or accelerometers are sensitive to tilt motions. In general, from pure acceleration measurements, it is not possible to separate the tilt acceleration from the translational ground acceleration. This can lead to severe misinterpretation of seismograms. Here, we present three different methods that can help solving this problem by correcting translational records for dynamic tilt induced by ground deformation with direct measurements of rotational motions: (1) a simple time-domain method, (2) a frequency-domain method proposed by Crawford and Webb (2000) using a coherence-weighted transfer function between rotation and acceleration, and (3) an adapted frequency-domain method that corrects only those parts of the spectrum with coherence between translational acceleration and rotation angle higher than 0.5. These three methods are discussed in three different experimental settings: (1) a reproducible and precisely known laboratory test using a high-precision tilt table, (2) a synthetic test with a simulated volcanic very-long-period event, and (3) a real data set recorded during the 2018 Mt. Kīlauea caldera collapse. All the three test cases show severe influence of tilt motion on the acceleration measurements. The time-domain method and the adapted frequency-domain method show very similar performance in all three test cases. Those two methods are able to remove the tilt component reliably from the acceleration record.

Estimating interannual variability arising from weather events

2001 ◽  
Vol 38 (A) ◽  
pp. 274-288 ◽  
Author(s):  
Xiaogu Zheng ◽  
James Renwick
Keyword(s):  
Frequency Domain ◽  
Interannual Variability ◽  
Time Domain ◽  
Synthetic Data ◽  
Estimation Procedure ◽  
Frequency Domain Method ◽  
Domain Method ◽  
Weather Events ◽  
Long Time ◽  
The Time Domain

The advantages and limitations of frequency domain and time domain methods for estimating the interannual variability arising from day-to-day weather events are summarized. A modification of the time domain method is developed and its application in examining a precondition for the frequency domain method is demonstrated. A combined estimation procedure is proposed: it takes advantage of the strengths of both methods. The estimation procedures are tested with sets of synthetic data and are applied to long time series of three meteorological parameters. The impacts of the different methods on tests of potential long-range predictability for seasonal means are also discussed.

A Joint Numerical and Experimental Study of a Surging Point Absorbing Wave Energy Converter (WRASPA)

2009 ◽  
Author(s):  
Majid A. Bhinder ◽  
Clive G. Mingham ◽  
Derek M. Causon ◽  
Mohammad T. Rahmati ◽  
George A. Aggidis ◽  
...  
Keyword(s):  
Wave Energy ◽  
Informed Choice ◽  
Wave Energy Converter ◽  
Body Motion ◽  
Numerical Dissipation ◽  
Small Scale ◽  
Linear Wave ◽  
Energy Converter ◽  
Non Linear ◽  
Experimental Project

This paper presents the findings from using several commercial computational fluid dynamics codes in a joint numerical and experimental project to simulate WRASPA, a new wave energy converter (WEC) device. A series of fully 3D non-linear simulations of WRASPA are presented. Three commercial codes STAR-CCM, CFX and FLOW-3D are considered for simulating the WRASPA device and final results are presented based on the use of Flow-3D. Results are validated by comparison to experimental data obtained from small scale tank tests undertaken at Lancaster University (LU). The primary aim of the project is to use numerical simulation to optimize the collector geometry for power production over a range of likely wave climates. A secondary aim is to evaluate the ability of commercial codes to simulate rigid body motion in linear and non-linear wave climates in order to choose the optimal code with respect to compute speed and ease of problem setup. Issues relating to the ability of a code in terms of numerical dissipation of waves, wave absorption, wave breaking, grid generation and moving bodies will all be discussed. The findings of this paper serve as a basis for an informed choice of commercial package for such simulations. However the capability of these commercial codes is increasing with every new release.

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