A COMPARATIVE NUMERICAL ANALYSIS OF THE AVAILABLE POWER BETWEEN REGULAR AND IRREGULAR WAVES: CASE STUDY OF AN OSCILLATING WATER COLUMN CONVERTER IN RIO GRANDE COAST, BRAZIL

In this work, a novel Boundary Element Method (BEM) is developed and applied to the investigation of the performance of Oscillating Water Column (OWC) systems, taking into account the interaction of the incident wave field with the bottom topography. The modelling includes the effect of additional upwave walls and barriers used to modify the resonance characteristics of the device and improve its performance as the U-OWC configuration. Numerical results illustrating the effects of depth variation in conjunction with other parameters—such as chamber dimensions as well as the parameters associated with the turbine and power take-off system—on the device performance are presented and discussed. Finally, a case study is presented regarding the potential installation of an OWC in a selected port site in the Black Sea, characterized by a good wave energy potential, on the coast of Romania.

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Numerical analysis of the oscillating water column wave energy extraction system

Mathematical Modelling ◽

10.1016/0270-0255(87)90637-3 ◽

1987 ◽

Vol 8 ◽

pp. 524-531 ◽

Cited By ~ 3

Author(s):

H.C. Alexander ◽

K.C. Watts ◽

J.W. Graham

Keyword(s):

Numerical Analysis ◽

Water Column ◽

Wave Energy ◽

Extraction System ◽

Energy Extraction ◽

Oscillating Water Column

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Latching Control of a Floating Oscillating Water Column Wave Energy Converter in Irregular Waves

Volume 9A: Ocean Renewable Energy ◽

10.1115/omae2014-23260 ◽

2014 ◽

Cited By ~ 3

Author(s):

João C. C. Henriques ◽

Juan C. Chong ◽

António F. O. Falcão ◽

Rui P. F. Gomes

Keyword(s):

Water Column ◽

Wave Energy ◽

Rotational Speed ◽

Phase Control ◽

Wave Energy Converter ◽

Irregular Waves ◽

Oscillating Water Column ◽

Random Waves ◽

Energy Converter ◽

Excitation Force

The paper concerns the phase control by latching of a floating oscillating-water-column (OWC) wave energy converter of spar-buoy type in irregular random waves. The device is equipped with a two-position fast-acting valve in series with the turbine. The instantaneous rotational speed of the turbine is controlled through the power electronics according to a power law relating the electromagnetic torque on the generator rotor to the rotational speed, an algorithm whose adequacy had been numerically tested in earlier papers. Two alternative strategies (1 and 2) for the latching/unlatching timings are investigated. Strategy 1 is based on the knowledge of the zero-crossings of the excitation force on the floater-tube set. This is difficult to implement in practice, since the excitation force can neither be measured directly nor predicted. Strategy 2 uses as input easily measurable physical variables: air pressure in the chamber and turbine rotational speed. Both strategies are investigated by numerical simulation based on a time-domain analysis of a spar-buoy OWC equipped with a self-rectifying radial-flow air turbine of biradial type. Air compressibility in the chamber plays an important role and was modelled as isentropic in a fully non-linear way. Numerical results show that significant gains up to about 28% are achievable through strategy 1, as compared with no phase control. Strategy 2, while being much easier to implement in practice, was found to yield more modest gains (up to about 15%).

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