Analysis of the Geometric Tunability of a WEC From a Worldwide Perspective

Nowadays the goal of WEC developers is to reduce the price of the harvested energy for its own technology, via either decreasing the cost of WECs or increasing the power production. In order to increase the power production of a particular WEC, usually the WECs are tuned with the wave climate at the target location. However, in order to achieve the maximum profitability, the WECs must be able to be deployed in a bunch of locations with different wave climates. Therefore WECs must be flexible to be adapted to different kind of locations. The matchability of a device could be achieved via the PTO control or changing the geometric characteristics of a particular device. In this study, an analysis about how the geometric tuning of a generic wave energy converter affects to different climate scenarios is performed. Firstly, a generic wave energy converter is assumed to be formed by an array of floating cylinders that absorb in heave. Three options are proposed in the present study, a cylinder with its natural period on 4 s, typical of enclosed seas, another option with a natural period of 8 s (mean Atlantic swell) and an option that is tunable as a function of the location in order to evaluate the influence of tuning on the power performance. The power matrix is computed with a frequency domain model and then, the converters are evaluated worldwide, taking the met-ocean data from a global reanalysis database (GOW) from Reguero et al (2012). The results are presented in terms of two main indicators, on one hand, the capture width ratio, that evaluates the efficiency of the converter on each location, and the kW/Ton parameter that evaluates the efficiency of the converter on “economic” terms. Finally, tuning a converter for each location of deployment resulted positive in terms of capture width ratio, however regarding the kW/Ton indicator tuning resulted useless due to the heaviness of the structures needed to tune the converter with high peak periods. The number of suitable locations (in terms of an acceptable kW/Ton indicator) was higher as the mass of the structure is reduced, regardless of the natural period of the converter, thanks to a good performance of high natural periods converters.

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Power Take-Off Selection for a U-Shaped OWC Wave Energy Converter

Volume 10: Ocean Renewable Energy ◽

10.1115/omae2019-96368 ◽

2019 ◽

Author(s):

Alessandra Romolo ◽

João C. C. Henriques ◽

Luís M. C. Gato ◽

Giovanni Malara ◽

Valentina Laface ◽

...

Keyword(s):

Water Column ◽

Wave Energy ◽

Time Domain ◽

Wave Energy Converter ◽

Domain Model ◽

Ocean Engineering ◽

Energy Converter ◽

Natural Period ◽

Air Pocket ◽

Air Turbine

Abstract The REWEC3 (Resonant Wave Energy Converter) is a fixed oscillating water column (OWC) wave energy converter (WEC) incorporated in upright breakwaters. The device is composed by a chamber containing a water column in its lower part and an air pocket in its upper part. The air pocket is connected to the atmosphere via a duct hosting a self-rectifying air turbine. In addition, a REWEC3 includes a vertical U-shaped duct for connecting the water column to the open sea (for this reason it is known also as U-OWC). The working principle of the system is quite simple: by the action of the incident waves, the water inside the U-shaped duct is subject to a reciprocating motion, which induces alternately a compression and an expansion of the air pocket. The pressure difference between the air pocket and the atmosphere is used to drive an air turbine coupled to an off-the-shelf electrical generator connected to the grid. The main feature of the REWEC3 is the possibility of tuning the natural period of the water column in order to match a desired wave period through the size of the U-duct. The REWEC3 technology has been theoretically developed by Boccotti, later tested at the natural basin of the Natural Ocean Engineering Laboratory (NOEL, Italy), and finally proved at full scale with REWEC3 prototype built in the Port of Civitavecchia (Rome, Italy). The objective of this paper is to select and optimize a turbine/generator set of a U-shaped OWC installed in breakwaters located in the Mediterranean Sea, such as the Port of Civitavecchia, where the first prototype of REWEC3 has been realized, or the Port of Salerno or Marina delle Grazie of Roccella (Italy). The computations were performed using a time domain model based on the unsteady Bernoulli equation. Based on the time-domain model of the power plant, the following data is computed for the turbines: i) the ideal turbine diameter; ii) the generator feedback control law aiming to maximize the turbine power output for turbine coupled to the REWEC3 device for Mediterranean applications.

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Experimental investigation on hydrodynamic performance of a dual pontoon–power take-off type wave energy converter integrated with floating breakwaters

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

10.1177/1475090218804677 ◽

2018 ◽

Vol 233 (4) ◽

pp. 991-999 ◽

Cited By ~ 1

Author(s):

Dezhi Ning ◽

Xuanlie Zhao ◽

Ming Zhao ◽

Haigui Kang

Keyword(s):

Transmission Coefficient ◽

Wave Energy ◽

Wave Energy Converter ◽

Hydrodynamic Performance ◽

Width Ratio ◽

Frequency Range ◽

Effective Frequency ◽

Energy Converter ◽

Damping Force ◽

Capture Width Ratio

As an extension of the single pontoon wave energy converter–type breakwater, a wave energy converter–type breakwater equipped with dual pontoon–power take-off system is proposed to broaden the effective frequency range (for transmission coefficient KT < 0.5 and capture width ratio η > 20%). The wave energy converter–type breakwater with dual pontoon–power take-off system consists of a pair of heave-type pontoons and power take-off systems for which the power take-off system is installed to harvest the kinetic energy of heave motion of the pontoon. In this paper, we experimentally confirm the advantage of the wave energy converter–type breakwater with dual pontoon–power take-off system over the one with a single pontoon–power take-off system. Both wave energy converter–type breakwater with dual pontoon–power take-off system and that with single pontoon–power take-off system are tested in regular waves. A (electronic) current controller–magnetic powder brake system is used to simulate the power take-off system. The characteristics of power take-off system are investigated and results showed that the power take-off system can simulate the (approximate) Coulomb damping force well. Experimental results reveal that the wave energy converter–type breakwater with dual pontoon–power take-off system broadens the effective frequency range compared with the single pontoon–power take-off system with the same pontoon volume (i.e. the displacement of the pontoon). Specifically, the transmission coefficient of the system is smaller while the system in relative longer waves. Furthermore, the capture width ratio of system can be improved.

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Methodology for Performance Assessment of a Two-Body Heave Wave Energy Converter

Volume 8: Ocean Renewable Energy ◽

10.1115/omae2013-11311 ◽

2013 ◽

Cited By ~ 1

Author(s):

Adrian de Andrés ◽

Raúl Guanche ◽

José A. Armesto ◽

Fernando del Jésus ◽

César Vidal ◽

...

Keyword(s):

Time Series ◽

State Space ◽

Wave Energy ◽

Time Domain ◽

Classical Method ◽

Power Production ◽

Wave Energy Converter ◽

Domain Model ◽

Energy Converter

A wave energy farm composed by several two-body heaving wave energy converters is being developed by IH Cantabria. This study presents a methodology to obtain the power performance of an isolated two-body heaving wave energy converter, previously presented and analyzed by [1]. The methodology relies on a numerical model which represents the motion of the two bodies in the time domain. This time domain model has been built substituting the entire Cummins equation system with a state-space system, thereby avoiding the convolution integral of the radiation force term with a state-space subsystem, previously used in [2] and [3]. The performance of the device along its life cycle has been estimated based on a proposed new methodology. The new method is proposed in order to obtain the long term power production of a device with the same computational effort than the classical method based on the power matrix. The proposed method is able to estimate long term power production time series. This long time series is obtained using the MaxDiss selection technique from [4] in order to compute only the power of the most representative sea states and the Radial Basis Function interpolation technique (RBF) to obtain the complete power series.

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On the power performance of a wave energy converter with a direct mechanical drive power take-off system controlled by latching

Renewable Energy ◽

10.1016/j.renene.2021.01.004 ◽

2021 ◽

Author(s):

Milad Shadman ◽

Gustavo Omar Guarniz Avalos ◽

Segen F. Estefen

Keyword(s):

Wave Energy ◽

Wave Energy Converter ◽

Power Performance ◽

Energy Converter ◽

Drive Power

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Sensitivity of a Wave Energy Converter Dynamics Model to Nonlinear Hydrostatic Models

Volume 9: Ocean Renewable Energy ◽

10.1115/omae2015-41993 ◽

2015 ◽

Cited By ~ 3

Author(s):

Ryan G. Coe ◽

Diana L. Bull

Keyword(s):

Linear Model ◽

Wave Energy ◽

Three Dimensional ◽

Wave Energy Converter ◽

Domain Model ◽

Interpolation Model ◽

Surface Integral ◽

Energy Converter ◽

Motion Constraints ◽

Large Improvement

A three dimensional time-domain model, based on Cummins equation, has been developed for an axisymmetric point absorbing wave energy converter (WEC) with an irregular cross section. This model incorporates a number of nonlinearities to accurately account for the dynamics of the device: hydrostatic restoring, motion constraints, saturation of the power-take-off force, and kinematic nonlinearities. Here, an interpolation model of the hydrostatic restoring reaction is developed and compared with a surface integral based method. The effects of these nonlinear hydrostatic models on device dynamics are explored by comparing predictions against those of a linear model. For the studied WEC, the interpolation model offers a large improvement over a linear model and is roughly two orders-of-magnitude less computationally expensive than the surface integral based method.

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Optimization of Mooring Configuration Parameters of Floating Wave Energy Converters

Volume 5: Ocean Space Utilization; Ocean Renewable Energy ◽

10.1115/omae2011-49955 ◽

2011 ◽

Cited By ~ 5

Author(s):

Pedro C. Vicente ◽

Anto´nio F. O. Falca˜o ◽

Paulo A. P. Justino

Keyword(s):

Wave Energy ◽

Oil And Gas ◽

Wave Energy Converter ◽

Domain Model ◽

Floating Point ◽

Mooring System ◽

Energy Converter ◽

Energy Devices ◽

Wave Energy Converters ◽

Energy Converters

Floating point absorbers devices are a large class of wave energy converters for deployment offshore, typically in water depths between 40 and 100m. As floating oil and gas platforms, the devices are subject to drift forces due to waves, currents and wind, and therefore have to be kept in place by a proper mooring system. Although similarities can be found between the energy converting systems and floating platforms, the mooring design requirements will have some important differences between them, one of them associated to the fact that, in the case of a wave energy converter, the mooring connections may significantly modify its energy absorption properties by interacting with its oscillations. It is therefore important to examine what might be the more suitable mooring design for wave energy devices, according to the converters specifications. When defining a mooring system for a device, several initial parameters have to be established, such as cable material and thickness, distance to the mooring point on the bottom, and which can influence the device performance in terms of motion, power output and survivability. Different parameters, for which acceptable intervals can be established, will represent different power absorptions, displacements from equilibrium position, load demands on the moorings and of course also different costs. The work presented here analyzes what might be, for wave energy converter floating point absorber, the optimal mooring configuration parameters, respecting certain pre-established acceptable intervals and using a time-domain model that takes into account the non-linearities introduced by the mooring system. Numerical results for the mooring forces demands and also motions and absorbed power, are presented for two different mooring configurations for a system consisting of a hemispherical buoy in regular waves and assuming a liner PTO.

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Design and Analysis for a Floating Oscillating Surge Wave Energy Converter

Volume 9B: Ocean Renewable Energy ◽

10.1115/omae2014-24511 ◽

2014 ◽

Cited By ~ 10

Author(s):

Yi-Hsiang Yu ◽

Ye Li ◽

Kathleen Hallett ◽

Chad Hotimsky

Keyword(s):

Energy Conversion ◽

Structure Analysis ◽

Wave Energy ◽

Integrated Design ◽

Design Strategy ◽

Wave Energy Converter ◽

Wave Energy Conversion ◽

Power Performance ◽

Energy Converter ◽

The Cost

This paper presents a recent study on the design and analysis of an oscillating surge wave energy converter (OSWEC). A successful wave energy conversion design requires balance between the design performance and cost. The cost of energy is often used as the metric to judge the design of the wave energy conversion (WEC) system, which is often determined based on the device’s power performance; the cost of manufacturing, deployment, operation, and maintenance; and environmental compliance. The objective of this study is to demonstrate the importance of a cost-driven design strategy and how it can affect a WEC design. A set of three oscillating surge wave energy converter designs was analyzed and used as examples. The power generation performance of the design was modeled using a time-domain numerical simulation tool, and the mass properties of the design were determined based on a simple structure analysis. The results of those power performance simulations, the structure analysis, and a simple economic assessment were then used to determine the cost-efficiency of selected OSWEC designs. Finally, we present a discussion on the environmental barrier, integrated design strategy, and the key areas that need further investigation.

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Uncertainty in Wave Basin Testing of a Fixed Oscillating Water Column Wave Energy Converter

ASCE-ASME J Risk and Uncert in Engrg Sys Part B Mech Engrg ◽

10.1115/1.4051164 ◽

2021 ◽

Author(s):

Frances M. Judge ◽

Eoin Lyden ◽

Michael O'Shea ◽

Brian Flannery ◽

Jimmy Murphy

Keyword(s):

Water Column ◽

Wave Energy ◽

Wave Energy Converter ◽

Width Ratio ◽

Oscillating Water Column ◽

Energy Converter ◽

The Monte Carlo Method ◽

Wave Basin ◽

Measurement Location ◽

The Impact

Abstract This research presents a methodology for carrying out uncertainty analysis on measurements made during wave basin testing of an oscillating water column wave energy converter. Values are determined for Type A and Type B uncertainty for each parameter of interest, and uncertainty is propagated using the Monte Carlo method to obtain an overall Expanded Uncertainty with a 95% confidence level associated with the Capture Width Ratio of the device. An analysis into the impact of reflections on the experimental results reveals the importance of identifying the incident and combined wave field at each measurement location used to determine device performance, in order to avoid misleading results.

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