Performance evaluation of a dual resonance wave-energy convertor in irregular waves

For renewable wave energy to operate at grid scale, large arrays of Wave Energy Converters (WECs) need to be deployed in the ocean. Due to the hydrodynamic interactions between the individual WECs of an array, the overall power absorption and surrounding wave field will be affected, both close to the WECs (near field effects) and at large distances from their location (far field effects). Therefore, it is essential to model both the near field and far field effects of WEC arrays. It is difficult, however, to model both effects using a single numerical model that offers the desired accuracy at a reasonable computational time. The objective of this paper is to present a generic coupling methodology that will allow to model both effects accurately. The presented coupling methodology is exemplified using the mild slope wave propagation model MILDwave and the Boundary Elements Methods (BEM) solver NEMOH. NEMOH is used to model the near field effects while MILDwave is used to model the WEC array far field effects. The information between the two models is transferred using a one-way coupling. The results of the NEMOH-MILDwave coupled model are compared to the results from using only NEMOH for various test cases in uniform water depth. Additionally, the NEMOH-MILDwave coupled model is validated against available experimental wave data for a 9-WEC array. The coupling methodology proves to be a reliable numerical tool as the results demonstrate a difference between the numerical simulations results smaller than 5% and between the numerical simulations results and the experimental data ranging from 3% to 11%. The simulations are subsequently extended for a varying bathymetry, which will affect the far field effects. As a result, our coupled model proves to be a suitable numerical tool for simulating far field effects of WEC arrays for regular and irregular waves over a varying bathymetry.

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BREAKWATER ARMOR DISPLACEMENT THRESHOLDS: A POSSIBLE CORRELATION WITH CUMULATIVE WAVE ENERGY

Coastal Engineering Proceedings ◽

10.9753/icce.v19.186 ◽

1984 ◽

Vol 1 (19) ◽

pp. 186

Author(s):

Daniel L. Behnke ◽

Frederic Raichlen

Keyword(s):

Wave Energy ◽

Wave Train ◽

Wave Length ◽

Simple Wave ◽

Wave Theory ◽

Irregular Waves ◽

Reconstruction Technique ◽

Regular Wave ◽

Regular Waves ◽

Three Dimensional Model

An extensive program of stability experiments in a highly detailed three-dimensional model has recently been completed to define a reconstruction technique for a damaged breakwater (Lillevang, Raichlen, Cox, and Behnke, 1984). Tests were conducted with both regular waves and irregular waves from various directions incident upon the breakwater. In comparison of the results of the regular wave tests to those of the irregular wave tests, a relation appeared to exist between breakwater damage and the accumulated energy to which the structure had been exposed. The energy delivered per wave is defined, as an approximation, as relating to the product of H2 and L, where H is the significant height of a train of irregular waves and L is the wave length at a selected depth, calculated according to small amplitude wave theory using a wave period corresponding to the peak energy of the spectrum. As applied in regular wave testing, H is the uniform wave height and L is that associated with the period of the simple wave train. The damage in the model due to regular waves and that caused by irregular waves has been related through the use of the cumulative wave energy contained in those waves which have an energy greater than a threshold value for the breakwater.

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OPTIMIZATION OF THE WAVECAT WAVE ENERGY CONVERTER

Coastal Engineering Proceedings ◽

10.9753/icce.v33.structures.5 ◽

2012 ◽

Vol 1 (33) ◽

pp. 5 ◽

Cited By ~ 5

Author(s):

Hernan Fernandez ◽

Gregorio Iglesias ◽

Rodrigo Carballo ◽

Alberte Castro ◽

Marcos Sánchez ◽

...

Keyword(s):

Physical Model ◽

Wave Energy ◽

Model Tests ◽

Irregular Waves ◽

Intermediate Water ◽

Plan View ◽

Santiago De Compostela ◽

Wave Energy Converters ◽

Physical Model Tests ◽

The Difference

The development of efficient, reliable Wave Energy Converters (WECs) is a prerequisite for wave energy to become a commercially viable energy source. Intensive research is currently under way on a number of WECs, among which WaveCat©—a new WEC recently patented by the University of Santiago de Compostela. In this sense, this paper describes the WaveCat concept and its ongoing development and optimization. WaveCat is a floating WEC intended for operation in intermediate water depths (50–100 m). Like a catamaran, it consists of two hulls—from which it derives its name. The difference with a conventional catamaran is that the hulls are not parallel but convergent; they are joined at the stern, forming a wedge in plan view. Physical model tests of a 1:30 model were conducted in a wave tank using both regular and irregular waves. In addition to the waves and overtopping rates, the model displacements were monitored using a non-intrusive system. The results of the physical model tests will be used to validate the 3D numerical model, which in turn will be used to optimize the design of WaveCat for best performance under a given set of wave conditions.

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Performance Evaluation of Wave Energy Converters

Performance Evaluation of Wave Energy Converters ◽

10.13052/rp-9788792982278 ◽

2013 ◽

pp. 1-107 ◽

Cited By ~ 4

Author(s):

Arthur Pecher

Keyword(s):

Performance Evaluation ◽

Wave Energy ◽

Wave Energy Converters ◽

Energy Converters

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Numerical and experimental analysis of the power output of a point absorber wave energy converter in irregular waves

Ocean Engineering ◽

10.1016/j.oceaneng.2015.11.011 ◽

2016 ◽

Vol 111 ◽

pp. 483-492 ◽

Cited By ~ 13

Author(s):

M.T. Rahmati ◽

G.A. Aggidis

Keyword(s):

Wave Energy ◽

Power Output ◽

Experimental Analysis ◽

Wave Energy Converter ◽

Irregular Waves ◽

Energy Converter ◽

Point Absorber

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Experimental Assessment of the Performance of CECO Wave Energy Converter in Irregular Waves

Volume 10: Ocean Renewable Energy ◽

10.1115/omae2018-77686 ◽

2018 ◽

Cited By ~ 1

Author(s):

Claudio A. Rodríguez ◽

F. Taveira-Pinto ◽

P. Rosa-Santos

Keyword(s):

Wave Energy ◽

Transfer Functions ◽

Nonlinear Effects ◽

Model Tests ◽

Experimental Results ◽

Irregular Waves ◽

Scale Model ◽

Experimental Assessment ◽

Simplified Approach ◽

Wave Basin

A new concept of wave energy device (CECO) has been proposed and developed at the Hydraulics, Water Resources and Environment Division of the Faculty of Engineering of the University of Porto (FEUP). In a first stage, the proof of concept was performed through physical model tests at the wave basin (Rosa-Santos et al., 2015). These experimental results demonstrated the feasibility of the concept to harness wave energy and provided a preliminary assessment of its performance. Later, an extensive experimental campaign was conducted with an enhanced 1:20 scale model of CECO under regular and irregular long and short-crested waves (Marinheiro et al., 2015). An electric PTO system with adjustable damping levels was also installed on CECO as a mechanism of quantification of the WEC power. The results of regular waves tests have been used to validate a numerical model to gain insight into different potential configurations of CECO and its performance (López et al., 2017a,b). This paper presents the results and analyses of the model tests in irregular waves. A simplified approach based on spectral analyses of the WEC motions is presented as a means of experimental assessment of the damping level of the PTO mechanism and its effect on the WEC power absorption. Transfer functions are also computed to identify nonlinear effects associated to higher waves and to characterize the range of periods where wave absorption is maximized. Furthermore, based on the comparison of the present experimental results with those corresponding to a linear numerical potential model, some discussions are addressed regarding viscous and other nonlinear effects on CECO performance.

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Experimental Analysis of a Novel Adaptively Counter-Rotating Wave Energy Converter for Powering Drifters

Journal of Marine Science and Engineering ◽

10.3390/jmse7060171 ◽

2019 ◽

Vol 7 (6) ◽

pp. 171 ◽

Cited By ~ 1

Author(s):

Guoheng Wu ◽

Zhongyue Lu ◽

Zirong Luo ◽

Jianzhong Shang ◽

Chongfei Sun ◽

...

Keyword(s):

Wave Energy ◽

Wave Energy Converter ◽

Irregular Waves ◽

Surface Velocity ◽

Small Scale ◽

Power Constraint ◽

Energy Converter ◽

Wave Tank ◽

Wide Range ◽

Rotating Wave

Nowadays, drifters are used for a wide range of applications for researching and exploring the sea. However, the power constraint makes it difficult for their sampling intervals to be smaller, meaning that drifters cannot transmit more accurate measurement data to satellites. Furthermore, due to the power constraint, a modern Surface Velocity Program (SVP) drifter lives an average of 400 days before ceasing transmission. To overcome the power constraint of SVP drifters, this article proposes an adaptively counter-rotating wave energy converter (ACWEC) to supply power for drifters. The ACWEC has the advantages of convenient modular integration, simple conversion process, and minimal affection by the crucial sea environment. This article details the design concept and working principle, and the interaction between the wave energy converter (WEC) and wave is presented based on plane wave theory. To verify the feasibility of the WEC, the research team carried out a series of experiments in a wave tank with regular and irregular waves. Through experiments, it was found that the power and efficiency of the ACWEC are greatly influenced by parameters such as wave height and wave frequency. The maximum output power of the small scale WEC in a wave tank is 6.36 W, which allows drifters to detect ocean data more frequently and continuously.

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