scholarly journals Hydrodynamic Performance of a Pitching Float Wave Energy Converter

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1801
Author(s):  
Yong Ma ◽  
Shan Ai ◽  
Lele Yang ◽  
Aiming Zhang ◽  
Sen Liu ◽  
...  
Keyword(s):  
Energy Conversion ◽  
Frequency Domain ◽  
Wave Energy ◽  
Center Of Mass ◽  
Hydrodynamic Performance ◽  
Irregular Waves ◽  
Wave Energy Conversion ◽  
Wave Direction ◽  
Improved Stability ◽  
The Time Domain

This study analyzes the hydrodynamic performance and application of a pitching float-type wave energy conversion device under complex sea conditions in the South China Sea. Potential flow theory and ANSYS-AQWA software are used to establish a method for analyzing hydrodynamic performance in both time and frequency domains, as well as the various factors that influence hydrodynamic performance. The frequency domain characteristics of the conversion device are explored, as well as the time-domain characteristics when exposed to regular and irregular waves. The results show that the frequency domain of hydrodynamic performance conforms to the requirements of an offshore mobile platform. A mooring point that is closer to the center of mass leads to improved stability of the conversion device. The angle arrangement of the anchor-chain mooring method fully conforms to safety requirements. When the wave direction is 45°, the conversion device is highly stressed and its movement is the most strenuous; however, the device can operate safely and stably under all working conditions. These results provide a significant reference for expanding the wave-energy capture range and the hydrodynamic performance of floating wave-energy conversion devices.

scholarly journals Analytical and Numerical Analysis of the Dynamics of a Moonpool Platform–Wave Energy Buoy (MP–WEB)

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4083
Author(s):  
Kong ◽  
Liu ◽  
Su ◽  
Ao ◽  
Chen ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Wave Energy ◽  
Time Domain ◽  
Impulse Response Function ◽  
Radiation Force ◽  
Resonance Phenomenon ◽  
Hydrodynamic Performance ◽  
Wave Forces ◽  
Diffraction Radiation ◽  
The Time Domain

In this work the hydrodynamic performance of a novel wave energy converter configuration was analytically and numerically studied by combining a moonpool and a wave energy buoy, called the moonpool platform–wave energy buoy (MP–WEB). A potential flow, semi-analytical approach was adopted to assess the total (incident, diffraction, radiation) wave forces acting on the device, and the wave capture and energy efficiency performance of this configuration was assessed, both in the time and frequency domain. The performance of the two configurations, single float and double float, were analyzed and compared in terms of diffraction force, added mass radiation force, motion, and power in the frequency domain. Using an impulse response function-based (IRF) method, the frequency domain results were converted in the time domain. The same parameters in the time domain were derived and the main results were confirmed. Wave energy conversion efficiency was significantly increased due to the resonance phenomenon inside the moonpool.

‘Inverse’ Concept: Wave Energy Generation by Motion and Green Water Maximisation

2009 ◽  
Author(s):  
Bas Buchner ◽  
Frederick Jaouen
Keyword(s):  
Renewable Energy ◽  
Energy Conversion ◽  
Frequency Domain ◽  
Water Flow ◽  
Wave Energy ◽  
Volume Of Fluid ◽  
Green Water ◽  
Wave Energy Conversion ◽  
Energy Concept ◽  
The Waves

This paper presents the initial investigations into the ‘Inverse’ concept for wave energy conversion, based on the maximisation of motions and green water. The ‘Inverse’ concept combines aspects of ‘overtopping’, ‘heaving’ and ‘pitching’ wave energy conversion concepts, but also adds specific aspects such as the use of green water. Instead of reducing the motions and green water as is done in normal offshore hydrodynamics, the ‘Inverse’ concepts tries to maximise the motions and green water to generate energy from the waves. Results are presented of frequency domain calculations for the motion (de-) optimisation. Improved Volume Of Fluid (iVOF) simulations are used to simulate the green water flow on the deck. It is concluded that the potential of the ‘Inverse’ concept is clear. As a result of the double connotation of the word ‘green’, this renewable energy concept could also be called the ‘green water’ concept. Further work needs to be carried out on the further optimisation of the concept.

Latching Control of an OWC Spar-Buoy Wave Energy Converter in Regular Waves

2012 ◽  
Author(s):  
J. C. C. Henriques ◽  
A. F. O. Falcão ◽  
R. P. F. Gomes ◽  
L. M. C. Gato
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Phase Control ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Wave Direction ◽  
Regular Waves ◽  
Energy Converter ◽  
Chamber Volume ◽  
The Time Domain

The present paper concerns an OWC spar-buoy, possibly the simplest concept for a floating oscillating-water-column (OWC) wave energy converter. It is an axisymmetric device (and so insensitive to wave direction) consisting basically of a (relatively long) submerged vertical tail tube open at both ends, fixed to a floater that moves essentially in heave. The length of the tube determines the resonance frequency of the inner water column. The oscillating motion of the internal free surface relative to the buoy, produced by the incident waves, makes the air flow through a turbine that drives an electrical generator. It is well known that the frequency response of point absorbers like the spar buoy is relatively narrow, which implies that their performance in irregular waves is relatively poor. Phase control has been proposed to improve this situation. The present paper presents a theoretical investigation of phase control by latching of an OWC spar-buoy in which the compressibility of air in the chamber plays an important role (the latching is performed by fast closing and opening an air valve in series with the turbine). In particular such compressibility may remove the constraint of latching threshold having to coincide with an instant of zero relative velocity between the two bodies (in the case under consideration, between the floater and the OWC). The modelling is performed in the time domain for a given device geometry, and includes the numerical optimization of the air turbine rotational speed, chamber volume and latching parameters. Results are obtained for regular waves.

On the Further Optimization of the “Green Water Concept” for Wave Energy Conversion

2012 ◽  
Author(s):  
Joop A. Helder ◽  
Christian Schmittner ◽  
Bas Buchner
Keyword(s):  
Energy Conversion ◽  
Wave Energy ◽  
Green Water ◽  
Wave Energy Conversion ◽  
Pilot Model ◽  
Wide Range ◽  
Water Columns ◽  
Relative Water ◽  
Entrapped Air ◽  
The Time Domain

This paper presents initial results from the following-up study of the ‘inverse’ or ‘green water concept’ for wave energy conversion. Initially presented in 2009, the ‘inverse concept’ was developed by MARIN as a vehicle for open discussion and exchange of ideas in the field of wave energy conversion. Pilot model tests presented in 2010 showed the great potential of the concept, but also revealed the challenges associated with Power Take Off design. The present study aims to further optimize the inverse concept. A new PTO system has been incorporated, based on robustness and effective use of the structure’s (de)optimized hull. The resulting renewed concept combines maximized vessel motions with OWC-type of wave energy conversion. This paper focuses on the motion response of the renewed concept. Frequency domain calculations show the response of the concept with water columns (moonpools) at the bow and stern. Remarkably, the already maximized motions of the hull become even more extreme when moonpools are incorporated. Special attention is given to the relative motions of the water inside the moonpools, as these give an indication of the wave energy conversion potential of the concept. The relative water motions inside the moonpools show a large response that is characterized by multiple peaks. This indicates the concept’s ability to convert energy in a wide range of sea states. Results from additional diffraction analysis show that through proper tuning, the water columns inside the moonpools can be modeled as solid water-bodies. This allows for a future numerical modeling of the hydrodynamic interaction between structure, water columns, entrapped air and PTO damping in the time domain.

scholarly journals Hydrodynamic Performance of an Asymmetry OWC Device Mounted on a Box-Type Breakwater

2021 ◽  
Vol 8 ◽  
Author(s):  
Zhengzhi Deng ◽  
Pinjie Wang ◽  
Pengda Cheng
Keyword(s):  
Energy Conversion ◽  
Wave Height ◽  
Incident Wave ◽  
Wave Energy ◽  
Short Wave ◽  
Absorption Efficiency ◽  
Hydrodynamic Performance ◽  
Maintenance Cost ◽  
Wave Energy Conversion ◽  
Coupling System

To share the construction and maintenance cost, an asymmetric oscillating water column (OWC) device integrated with a pile-fixed box-typed offshore breakwater is considered experimentally and numerically. A fully nonlinear numerical wave tank is established and validated with the open source solver OpenFOAM. The effects of the width and draft of rear box, and the incident wave height on the wave energy conversion efficiency, reflection and transmission coefficients, and energy dissipation coefficient are examined. In addition, the superiority of the present coupling system, compared to the traditional box-type breakwater, is discussed. With well comparisons, the results show that the existence of the rear breakwater is beneficial for the formation of partial standing waves and further wave energy conversion. In the range of wave heights tested, the higher the incident wave height, the larger the energy absorption efficiency except for the short-wave regimes. Moreover, the OWC-breakwater coupling system can obtain a similar wave blocking ability to the traditional one, and simultaneously extract wave energy and decrease wave reflection.

Comparison of Physical Model Tests With a Time Domain Simulation Model of a Wave Energy Converter

2012 ◽  
Author(s):  
Ryan S. Nicoll ◽  
Charles F. Wood ◽  
André R. Roy
Keyword(s):  
Energy Conversion ◽  
Wave Energy ◽  
Time Domain ◽  
Wave Energy Converter ◽  
Ocean Dynamics ◽  
Time Domain Simulation ◽  
Wave Energy Conversion ◽  
Energy Converter ◽  
Energy Conversion Systems ◽  
The Time Domain

Development of wave energy conversion systems may yield many key benefits for society such as the production of electrical power or fresh water for remote communities. However, complex ocean dynamics make it difficult for technology developers to not only address the stability and survivability of their systems, but also to establish energy conversion rates that are fundamental to proving economic viability. Building physical prototypes presents many challenges in terms of cost, accessible facilities, and time requirements. The use of accurate numerical modelling and computer simulation can help guide design and significantly reduce the number of physical prototype tests required and as a result play a primary role in the development of wave energy conversion systems that have to operate in challenging marine environments. SurfPower is an ocean wave energy converter (WEC) that converts wave motion into useful energy through surge and heave motion of a point absorber. The system pumps seawater into a high pressure hydraulic network that generates electricity via a turbine or freshwater via desalination at a facility onshore. The system is nonlinear due to the significant change in draft and mooring reaction load through the energy capture cycle of the device. This makes the use of nonlinear time domain simulation ideal for analysis and design of the system. Furthermore, utilizing a simplified nonlinear hydrodynamic model available in the time domain results in a practical early-stage design tool for system refinement. The focus of this work is to compare the results of scale model testing completed at the Institute for Ocean Technology in St. John’s, Newfoundland, with results produced from an equivalent system simulated in the time domain simulation software ProteusDS. The results give an assessment of the range of error that can be used to assess other experiments of the SurfPower WEC at full scale.

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