scholarly journals Efficiency and Survivability of a Floating Oscillating Water Column Wave Energy Converter Moored to the Seabed: An Overview of the EsflOWC MaRINET2 Database

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 992 ◽  
Author(s):  
Dogan Kisacik ◽  
Vasiliki Stratigaki ◽  
Minghao Wu ◽  
Lorenzo Cappietti ◽  
Irene Simonetti ◽  
...  
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Degrees Of Freedom ◽  
Mooring Line ◽  
Oscillating Water Column ◽  
Flume Experiments ◽  
Large Wave ◽  
Wave Flume ◽  
Wave Conditions ◽  
University Of Florence

Floating oscillating water column (OWC) type wave energy converters (WECs), compared to fixed OWC WECs that are installed near the coastline, can be more effective as they are subject to offshore waves before the occurrence of wave dissipation at a nearshore location. The performance of floating OWC WECs has been widely studied using both numerical and experimental methods. However, due to the complexity of fluid–structure interaction of floating OWC WECs, most of the available studies focus on 2D problems with WEC models of limited degrees-of-freedom (DOF) of motion, while 3D mooring effects and multiple-DOF OWC WECs have not been extensively investigated yet under 2D and 3D wave conditions. Therefore, in order to gain a deeper insight into these problems, the present study focuses on wave flume experiments to investigate the motion and mooring performance of a scaled floating OWC WEC model under 2D wave conditions. As a preparatory phase for the present MaRINET2 EsflOWC (efficiency and survivability of floating OWC) project completed at the end of 2017, experiments were also carried out in advance in the large wave flume of Ghent University. The following data were obtained during these experimental campaigns: multiple-DOF OWC WEC motions, mooring line tensions, free surface elevations throughout the wave flume, close to and inside the OWC WEC, change in the air pressure inside the OWC WEC chamber and velocity of the airflow through the vent on top of the model. The tested wave conditions mostly include nonlinear intermediate regular waves. The data obtained at the wave flume of Ghent University, together with the data from the EsflOWC tests at the wave flume of LABIMA, University of Florence, provide a database for numerical validation of research on floating OWC WECs and floating OWC WEC farms or arrays used by researchers worldwide.

scholarly journals Experimental Study of a Moored Floating Oscillating Water Column Wave-Energy Converter and of a Moored Cubic Box

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1834 ◽  
Author(s):  
Minghao Wu ◽  
Vasiliki Stratigaki ◽  
Peter Troch ◽  
Corrado Altomare ◽  
Tim Verbrugghe ◽  
...  
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Water Surface ◽  
Wave Energy Converter ◽  
Surface Elevation ◽  
Mooring Line ◽  
Oscillating Water Column ◽  
Energy Converter ◽  
Large Wave ◽  
Water Surface Elevation

This paper describes experimental research on a floating moored Oscillating Water Column (OWC)-type Wave-Energy Converter (WEC) carried out in the wave flume of the Coastal Engineering Research Group of Ghent University. This research has been introduced to cover the existing data scarcity and knowledge gaps regarding response of moored floating OWC WECs. The obtained data will be available in the future for the validation of nonlinear numerical models. The experiment focuses on the assessment of the nonlinear motion and mooring-line response of a 1:25 floating moored OWC WEC model to regular waves. The OWC WEC model motion has 6 degrees of freedom and is limited by a symmetrical 4-point mooring system. The model is composed of a chamber with an orifice on top of it to simulate the power-take-off (PTO) system and the associated damping of the motion of the OWC WEC model. In the first place, the motion response in waves of the moored floating OWC WEC model is investigated and the water surface elevation in the OWC WEC chamber is measured. Secondly, two different mooring-line materials (iron chains and nylon ropes) are tested and the corresponding OWC WEC model motions and mooring-line tensions are measured. The performance of these two materials is similar in small-amplitude waves but different in large wave-amplitude conditions. Thirdly, the influence of different PTO conditions is investigated by varying the diameter of the top orifice of the OWC WEC model. The results show that the PTO damping does not affect the OWC WEC motion but has an impact on the water surface elevation inside the OWC chamber. In addition, an unbalanced mooring configuration is discussed. Finally, the obtained data for a moored cubic model in waves are presented, which is a benchmarking case for future validation purposes.

scholarly journals The Effect of Mooring Line Parameters in Inducing Parametric Resonance on the Spar-Buoy Oscillating Water Column Wave Energy Converter

2020 ◽  
Vol 8 (1) ◽  
pp. 29 ◽  
Author(s):  
Giuseppe Giorgi ◽  
Rui P. F. Gomes ◽  
Giovanni Bracco ◽  
Giuliana Mattiazzo
Keyword(s):  
Water Column ◽  
Parametric Resonance ◽  
Wave Energy ◽  
Degrees Of Freedom ◽  
Production Efficiency ◽  
Parametric Instability ◽  
Mooring Line ◽  
Nonlinear Phenomenon ◽  
Oscillating Water Column ◽  
Highly Nonlinear

Although it is widely accepted that accurate modeling of wave energy converters is essential for effective and reliable design, it is often challenging to define an accurate model which is also fast enough to investigate the design space or to perform extensive sensitivity analysis. In fact, the required accuracy is usually brought by the inclusion of nonlinearities, which are often time-consuming to compute. This paper provides a computationally efficient meshless nonlinear Froude–Krylov model, including nonlinear kinematics and an integral formulation of drag forces in six degrees of freedom, which computes almost in real-time. Moreover, a mooring system model with three lines is included, with each line comprising of an anchor, a jumper, and a clump weight. The mathematical model is used to investigate the highly-nonlinear phenomenon of parametric resonance, which has particularly detrimental effects on the energy conversion performance of the spar-buoy oscillating water column (OWC) device. Furthermore, the sensitivity on changes to jumper and clump-weight masses are discussed. It is found that mean drift and peak loads increase with decreasing line pre-tension, eventually leading to a reduction of the operational region. On the other hand, the line pre-tension does not affect power production efficiency, nor is it able to avoid or significantly limit the severity of parametric instability.

Evaluation of 3-D Computational Model of Oscillating Water Column Converter with Constructal Design with Three Degrees of Freedom and Limited Chimney Height

2021 ◽  
Vol 407 ◽  
pp. 128-137
Author(s):  
Vinícius Bloss ◽  
Camila Fernandes Cardozo ◽  
Flávia Schwarz Franceschini Zinani ◽  
Luiz Alberto Oliveira Rocha
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Mechanical Energy ◽  
Ocean Waves ◽  
Response Surfaces ◽  
Oscillating Water Column ◽  
Promising Source ◽  
Three Degrees Of Freedom

Theoretically, ocean waves contain enough mechanical energy to supply the entire world’s demand and, as of late, are seen as a promising source of renewable energy. To this end, several different technologies of Wave Energy Converters (WEC) have been developed such as Oscillating Water Column (OWC) devices. OWCs are characterized by a chamber in which water oscillates inside and out in a movement similar to that of a piston. This movement directs air to a chimney where a turbine is attached to convert mechanical energy. The analysis conducted was based on the Constructive Design Method, in which a numerical study was carried out to obtain the geometric configuration that maximized the conversion of wave energy into mechanical energy. Three degrees of freedom were used: the ratio of height to length of the hydropneumatic chamber (H1/L), the ratio of the height of the chimney to its diameter (H2/d) and the ratio of the width of the hydropneumatic chamber to the width of the wave tank (W/Z). A Design of Experiments (DoE) technique coupled with Central Composite Design (CCD) allowed the simulation of different combinations of degrees of freedom. This allowed the construction of Response Surfaces and correlations for the efficiency of the system depending on the degrees of freedom (width and height of the chamber), as well as the optimization of the system based on the Response Surfaces.

Numerical and Geometrical Analysis of the Onshore Oscillating Water Column Wave Energy with a Ramp

2021 ◽  
Vol 412 ◽  
pp. 11-26
Author(s):  
Marla Rodrigues Oliveira ◽  
Elizaldo Domingues Santos ◽  
Liércio André Isoldi ◽  
Luiz Alberto Oliveira Rocha ◽  
Mateus das Neves Gomes
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Degrees Of Freedom ◽  
Design Method ◽  
Geometric Analysis ◽  
Relative Difference ◽  
Front Wall ◽  
Multiphase Model ◽  
Oscillating Water Column ◽  
Worst Case

This study is about a two-dimensional numerical analysis of the influence of a ramp in front on an oscillating water column wave energy converter (OWC-WEC). The main purpose was to evaluate, numerically and geometrically, the effect of using a ramp variation in relation to the frontal wall on the hydropneumatic power of the OWC-WEC. The constructal design method was applied for geometric analysis. The problem had a geometric constraint: the area of the ramp (A2) and two degrees of freedom: H2 / L2 (ratio of the height and length of the ramp) and L4 (the distance of the ramp concerning the OWC-WEC front wall). In numerical simulations, the equations of conservation of mass, momentum, and an equation for the transport of volumetric fraction were solved using the finite volume method (FVM). The multiphase model volume of fluid (VOF) was applied for the air-water interaction. Thus, the increase in the H2/L2 ratio resulted in a decrease of the root mean square (RMS) of the available hydropneumatic power (Phyd). By varying the distance L4, the better case was = 6 m and / = 0.025 and the worst case was = 1 m and / = 0.2. The relative difference between the better RMS Phyd = 150.7957 W and the worst Phyd = 73.1164 W reached up to a hundred and six percent.

Experimental Study the Performance of a Compact Mooring System for a Dual Chamber Floating Oscillating Water Column Device

2020 ◽  
Author(s):  
Sheng Xu ◽  
K. Rezanejad ◽  
Shan Wang ◽  
J. F. M. Gadelho ◽  
C. Guedes Soares
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Degrees Of Freedom ◽  
Wave Energy Converter ◽  
Air Pressure ◽  
Mooring System ◽  
Oscillating Water Column ◽  
Energy Converter ◽  
Six Degrees Of Freedom ◽  
Motion Responses

Abstract A compact mooring system concept is proposed. This novel mooring is composed of submerged buoy and three segments of nylon ropes, which is suitable for the large wave energy converters and wave energy converter array due to its high flexibility and small mooring radius. The performance of this mooring concept was studied experimentally when it was moored to an oscillating water column. The damping of the oscillating water column was modelled by an orifice on top of the chamber. Both regular and irregular head sea wave tests were conducted. In order to study the influence of wave height on system dynamics, two series of regular wave tests with same periods but different wave heights were conducted. An optical tracking system was installed to capture six degrees of freedom motion responses of oscillating water column. The air pressure in the chamber was measured by the air pressure sensor. Two load cells were installed on the top of mooring lines to measure mooring tension time series. Besides, the wave surface elevations inside the chamber were measured by the wave gauges. According to the experimental results, the six degrees of freedom motion responses of floating wave energy converter and mooring tensions are analyzed. Besides, the energy conversion efficiency is evaluated based on the measured data.

Floating Moored Oscillating Water Column With Meshless SPH Method

2018 ◽  
Author(s):  
Alejandro J. C. Crespo ◽  
Matthew Hall ◽  
José M. Domínguez ◽  
Corrado Altomare ◽  
Minghao Wu ◽  
...  
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Coupled Model ◽  
Physical Modelling ◽  
Numerical Results ◽  
Mooring Line ◽  
Oscillating Water Column ◽  
Mooring Lines ◽  
Wave Energy Converters ◽  
Energy Converters

The meshless method called Smoothed Particle Hydrodynamics (SPH) is here proposed to simulate floating Oscillating Water Column (OWC) Wave Energy Converters (WECs). The SPH-based DualSPHysics code is coupled with MoorDyn, an open-source dynamic mooring line model. The coupled model is first validated using laboratory tests of a floating solid box moored to the wave flume bottom using four mooring lines interacting with regular waves. The numerical free-surface elevation at different locations, the motions of the floating solid box (heave, surge and pitch) and the tensions in the mooring lines are compared with the experimental data. Secondly, the coupled model is employed to simulate a floating OWC WEC moored to the sea bottom, while numerical results are also validated using data from physical modelling. The numerical results are promising to simulate floating OWC WECs. However, some discrepancies are noticed since the simulations presented in this work only consider a single-phase (water) so the full OWC WEC behaviour is only partially reproduced. Nevertheless, considering the aforementioned limitations, DualSPHysics can be used at this stage as complementary tool to physical modelling for a preliminary design of floating wave energy converters.

Sign in / Sign up

Export Citation Format

Share Document