Wave power extraction by arbitrary arrays of non-diffracting oscillating water columns

The integration of oscillating water column (OWC) wave energy converters into a coastal structure (breakwater, jetty, pier, etc.) or, more generally, their installation along the coast is an effective way to increase the accessibility of wave power exploitation. In this paper, a theoretical model is developed based on the linear potential flow theory and eigenfunction matching method to evaluate the hydrodynamic performance of an array of OWCs installed along a vertical straight coast. The chamber of each OWC consists of a hollow vertical circular cylinder, which is half embedded in the wall. The OWC chambers in the theoretical model may have different sizes, i.e. different values of the radius, wall thickness and submergence. At the top of each chamber, a Wells turbine is installed to extract power. The effects of the Wells turbine together with the air compressibility are taken into account as a linear power take-off system. The hydrodynamic and wave power extraction performance of the multiple coast-integrated OWCs is compared with that of a single offshore/coast-integrated OWC and of multiple offshore OWCs. More specifically, we analyse the role of the incident wave direction, chamber size (i.e. radius, wall thickness and submergence), spacing between OWCs and number of OWCs by means of the present theoretical model. It is shown that wave power extraction from the coast-integrated OWCs for a certain range of wave conditions can be significantly enhanced due to both the constructive array effect and the constructive coast effect.

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Experimental Investigation of the Small-scale Fixed Multi-chamber OWC Device

Chinese Journal of Mechanical Engineering ◽

10.1186/s10033-021-00641-9 ◽

2021 ◽

Vol 34 (1) ◽

Author(s):

Mohammad Shalby ◽

Ahmed Elhanafi ◽

Paul Walker ◽

David G. Dorrell ◽

Ahmad Salah ◽

...

Keyword(s):

Flow Characteristics ◽

Scale Model ◽

Small Scale ◽

Test Results ◽

Wave Condition ◽

Power Extraction ◽

Physical Experiments ◽

Water Columns ◽

Measurement Wave ◽

Oscillating Water Columns

AbstractSea wave energy generators or converters (WECs) have the potential to become a viable technology for clean, renewable energy production. Among the WEC technologies, the oscillating water columns (OWCs) are the most common WEC devices studied. These have been studied and developed over many years. Multi-chamber oscillating water columns (MC-OWC) have the potential to have a higher energy conversion when extracting energy in mixed sea states than single-chamber devices. In the work reported in this paper, physical experiments are carried under regular wave conditions to test the wave power extraction of a fixed MC-OWC small-scale model. The Power Take-Off (PTO) of the device is simulated using orifice plates. The flow characteristics through these orifices are pre-calibrated such that the extracted power can be obtained only using the pressure measurement. Wave condition effects on the damping of the PTO of the device power extraction are addressed. The test results illustrate that the PTO system damping is critical and affects device performance.

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Wave-power absorption by a periodic linear array of oscillating water columns

Ocean Engineering ◽

10.1016/s0029-8018(01)00076-2 ◽

2002 ◽

Vol 29 (10) ◽

pp. 1163-1186 ◽

Cited By ~ 33

Author(s):

A.F. de O. Falcão

Keyword(s):

Linear Array ◽

Wave Power ◽

Power Absorption ◽

Periodic Linear ◽

Water Columns ◽

Oscillating Water Columns

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Wave-power absorption by a finite row of oscillating water columns in a reflecting wall

Applied Ocean Research ◽

10.1016/s0141-1187(86)80005-0 ◽

1986 ◽

Vol 8 (2) ◽

pp. 105-109 ◽

Cited By ~ 9

Author(s):

Oddbjørn Malmo ◽

Arne Reitan

Keyword(s):

Wave Power ◽

Power Absorption ◽

Water Columns ◽

Oscillating Water Columns

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Comparison of the performance of oscillating water column devices based on arrangements of water columns

JOURNAL OF MECHANICAL ENGINEERING AND SCIENCES ◽

10.15282/jmes.14.3.2020.10.0555 ◽

2020 ◽

Vol 14 (3) ◽

pp. 7082-7093

Author(s):

Jahirwan Ut Jasron ◽

Sudjito Soeparmani ◽

Lilis Yuliati ◽

Djarot B. Darmadi

Keyword(s):

Wave Propagation ◽

Water Column ◽

Water Depth ◽

Graphical Form ◽

Wave Power ◽

Oscillating Water Column ◽

Power Absorption ◽

Water Columns ◽

Single Column ◽

Parallel Arrangement

The hydrodynamic performance of oscillating water column (OWC) depends on the depth of the water, the size of the water column and its arrangement, which affects the oscillation of the water surface in the column. An experimental method was conducted by testing 4 water depths with wave periods of 1-3 s. All data recorded by the sensor is then processed and presented in graphical form. The research focused on analyzing the difference in wave power absorption capabilities of the three geometric types of OWC based on arrangements of water columns. The OWC devices designed as single water column, the double water column in a series arrangement which was perpendicular to the direction of wave propagation, and double water column in which the arrangement of columns was parallel to the direction of wave propagation. This paper discussed several factors affecting the amount of power absorbed by the device. The factors are the ratio of water depth in its relation to wavelength (kh) and the inlet openings ratio (c/h) of the devices. The test results show that if the water depth increases in the range of kh 0.7 to 0.9, then the performance of the double chamber oscillating water column (DCOWC) device is better than the single chamber oscillating water column (SCOWC) device with maximum efficiency for the parallel arrangement 22,4%, series arrangement 20.8% and single column 20.7%. However, when referring to c/h, the maximum energy absorption efficiency for a single column is 27.7%, double column series arrangement is 23.2%, and double column parallel arrangement is 29.5%. Based on the results of the analysis, DCOWC devices in parallel arrangement showed the ability to absorb better wave power in a broader range of wave frequencies. The best wave of power absorption in the three testing models occurred in the wave period T = 1.3 seconds.

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Performance Analysis on the Use of Oscillating Water Column in Barge-Based Floating Offshore Wind Turbines

Mathematics ◽

10.3390/math9050475 ◽

2021 ◽

Vol 9 (5) ◽

pp. 475

Author(s):

Payam Aboutalebi ◽

Fares M’zoughi ◽

Izaskun Garrido ◽

Aitor J. Garrido

Keyword(s):

Wind Turbines ◽

Positive Impact ◽

Offshore Wind ◽

Offshore Wind Turbines ◽

Floating Offshore Wind Turbines ◽

Water Columns ◽

Numerical Tools ◽

Oscillating Water Columns ◽

The Given ◽

The Waves

Undesired motions in Floating Offshore Wind Turbines (FOWT) lead to reduction of system efficiency, the system’s lifespan, wind and wave energy mitigation and increment of stress on the system and maintenance costs. In this article, a new barge platform structure for a FOWT has been proposed with the objective of reducing these undesired platform motions. The newly proposed barge structure aims to reduce the tower displacements and platform’s oscillations, particularly in rotational movements. This is achieved by installing Oscillating Water Columns (OWC) within the barge to oppose the oscillatory motion of the waves. Response Amplitude Operator (RAO) is used to predict the motions of the system exposed to different wave frequencies. From the RAOs analysis, the system’s performance has been evaluated for representative regular wave periods. Simulations using numerical tools show the positive impact of the added OWCs on the system’s stability. The results prove that the proposed platform presents better performance by decreasing the oscillations for the given range of wave frequencies, compared to the traditional barge platform.

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Hardware-in-the-Loop Validation of Model Predictive Control of a Discrete Fluid Power Power Take-Off System for Wave Energy Converters

Energies ◽

10.3390/en12193668 ◽

2019 ◽

Vol 12 (19) ◽

pp. 3668

Author(s):

Anders H. Hansen ◽

Magnus F. Asmussen ◽

Michael M. Bech

Keyword(s):

Model Predictive Control ◽

Predictive Control ◽

Wave Energy ◽

Fluid Power ◽

Wave Power ◽

Reactive Control ◽

Power Extraction ◽

Wave Energy Converters ◽

Extraction Algorithm ◽

Energy Converters

Model predictive control based wave power extraction algorithms have been developed and found promising for wave energy converters. Although mostly proven by simulation studies, model predictive control based algorithms have shown to outperform classical wave power extraction algorithms such as linear damping and reactive control. Prediction models and objective functions have, however, often been simplified a lot by for example, excluding power take-off system losses. Furthermore, discrete fluid power forces systems has never been validated experimentally in published research. In this paper a model predictive control based wave power extraction algorithm is designed for a discrete fluid power power take-off system. The loss models included in the objective function are based on physical models of the losses associated with discrete force shifts and throttling. The developed wave power extraction algorithm directly includes the quantized force output and the losses models of the discrete fluid power system. The experimental validation of the wave power extraction algorithm developed in the paper shown an increase of 14.6% in yearly harvested energy when compared to a reactive control algorithm.

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Switching Control Strategy for Oscillating Water Columns Based on Response Amplitude Operators for Floating Offshore Wind Turbines Stabilization

Applied Sciences ◽

10.3390/app11115249 ◽

2021 ◽

Vol 11 (11) ◽

pp. 5249

Author(s):

Payam Aboutalebi ◽

Fares M’zoughi ◽

Itziar Martija ◽

Izaskun Garrido ◽

Aitor J. Garrido

Keyword(s):

Switching Control ◽

Response Amplitude ◽

Offshore Wind ◽

Oscillating Water Column ◽

Offshore Wind Turbines ◽

Floating Offshore Wind Turbines ◽

Water Columns ◽

Switching Control Strategy ◽

Response Amplitude Operators ◽

Oscillating Water Columns

In this article, a new strategy for switching control has been proposed with the aim of reducing oscillations in floating offshore wind turbines. Such oscillations lead to a shortage in the system’s efficiency, lifespan and harvesting capability of wind and wave energies. In order to study the decreasing of undesired oscillations in the system, particularly in pitch and top tower fore-aft movements, a square-shaped platform barge equipped with four symmetric oscillating water columns has been considered. The oscillating water columns’ air flux valves allow to operate the air columns so that to control the barge movements caused by oscillatory motion of the waves. In order to design the control scheme, response amplitude operators have been used to evaluate the performance of the system for a range of wave frequency profiles. These response amplitude operators analysis makes it possible to implement a switching control strategy to adequately regulate the valves opening/closing transition. The obtained results show that the proposed controlled oscillating water column-based barge present a better performance compared to the traditional barge one. In the case study with the period of 10 s, the results indicate the significant oscillation reduction for the controlled oscillating water column-based system compared to the standard barge system by 30.8% in pitch angle and 25% in fore-aft displacement.

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