Special Issue "Advances in Ocean Wave Energy Conversion"

A special issue of Journal of Marine Science and Engineering (ISSN 2077-1312). This special issue belongs to the section "Ocean Engineering".

Deadline for manuscript submissions: 30 June 2019

Special Issue Editor

Guest Editor
Prof. Dr. Ossama O. Abdelkhalik

Department of Aerospace Engineering, Iowa State University, 1200 Howe Hall, 537 Bissell Road, Ames, IA 50011, USA
Website | E-Mail
Phone: (515) 294-3613
Interests: Ocean Wave Energy Conversion; Dynamic and Control; Optimization; Spacecraft Dynamics

Special Issue Information

Dear Colleagues,

Despite its potential, wave energy extraction technology is not yet mature. The US Department of Energy (DoE) reported in 2012 that the world’s installed capacity for wave energy is less than 5 MW, mostly produced on a pre-commercial basis. Yet, there has been a significant growing interest in wave energy in the past few years. Recently, we have seen advances in wave energy converter (WEC) modelling, WEC array modelling, and new control concepts have emerged. There have also been advances in the development of power take off (PTO) units. The aim of this Special Issue is to assemble papers to reflect the state of wave energy covering a range of topics in numerical models, WEC control, physical model testing, development of PTO units, and WEC array modelling. Papers on all aspects of ocean wave energy conversion are invited, especially on the following:

  • Advanced numerical models
  • Nonlinear WEC device modelling
  • Physical model tests (laboratory and field experiences)
  • PTO and control systems
  • WEC array modelling, simulation, and control
  • WEC array optimization
Prof. Dr. Ossama O. Abdelkhalik
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Journal of Marine Science and Engineering is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 550 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Wave energy conversion (WEC) 
  • Power Take Off (PTO) 
  • WEC Control 
  • Wave-to-wire models
  • CFD models
  • Numerical models 
  • WEC arrays 
  • Nonlinear WEC models

Published Papers (10 papers)

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Research

Open AccessFeature PaperArticle
A Hamiltonian Surface-Shaping Approach for Control System Analysis and the Design of Nonlinear Wave Energy Converters
J. Mar. Sci. Eng. 2019, 7(2), 48; https://doi.org/10.3390/jmse7020048
Received: 23 January 2019 / Revised: 7 February 2019 / Accepted: 8 February 2019 / Published: 15 February 2019
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Abstract
The dynamic model of Wave Energy Converters (WECs) may have nonlinearities due to several reasons such as a nonuniform buoy shape and/or nonlinear power takeoff units. This paper presents the Hamiltonian Surface-Shaping (HSS) approach as a tool for the analysis and design of [...] Read more.
The dynamic model of Wave Energy Converters (WECs) may have nonlinearities due to several reasons such as a nonuniform buoy shape and/or nonlinear power takeoff units. This paper presents the Hamiltonian Surface-Shaping (HSS) approach as a tool for the analysis and design of nonlinear control of WECs. The Hamiltonian represents the stored energy in the system and can be constructed as a function of the WEC’s system states, its position, and velocity. The Hamiltonian surface is defined by the energy storage, while the system trajectories are constrained to this surface and determined by the power flows of the applied non-conservative forces. The HSS approach presented in this paper can be used as a tool for the design of nonlinear control systems that are guaranteed to be stable. The optimality of the obtained solutions is not addressed in this paper. The case studies presented here cover regular and irregular waves and demonstrate that a nonlinear control system can result in a multiple fold increase in the harvested energy. Full article
(This article belongs to the Special Issue Advances in Ocean Wave Energy Conversion)
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Open AccessArticle
Experimental Study of a Hybrid Wave Energy Converter Integrated in a Harbor Breakwater
J. Mar. Sci. Eng. 2019, 7(2), 33; https://doi.org/10.3390/jmse7020033
Received: 31 December 2018 / Revised: 19 January 2019 / Accepted: 23 January 2019 / Published: 3 February 2019
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Abstract
Sea ports are infrastructures with substantial energy demands and often responsible for air pollution and other environmental problems, which may be minimized by using renewable energy, namely electricity harvested from ocean waves. In this regard, a wide variety of concepts to harvest wave [...] Read more.
Sea ports are infrastructures with substantial energy demands and often responsible for air pollution and other environmental problems, which may be minimized by using renewable energy, namely electricity harvested from ocean waves. In this regard, a wide variety of concepts to harvest wave energy are available and some shoreline technologies are already in an advanced development phase. The [email protected] project aims to assess the suitability and viability of existing wave energy conversion technologies to be integrated in harbor breakwaters, in order to take advantage of their high exposure to ocean waves. This paper describes the experimental study carried out to assess the performance of a hybrid wave energy converter (WEC) integrated in the rubble-mound structure that was proposed for the extension of the North breakwater of the Port of Leixões, Portugal. The hybrid concept combines the overtopping and the oscillating water column principles and was tested on a geometric scale of 1/50. This paper is focused on the assessment of the effects of the hybrid WEC integration on the case-study breakwater, both in terms of its stability and functionality. The 2D physical model included the reproduction of the seabed bathymetry in front of the breakwater and the generation of a wide range of irregular sea states, including extreme wave conditions. The experimental results shown that the integration of the hybrid WEC in the breakwater does not worsens the stability of its toe berm blocks and reduces the magnitude of the overtopping events. The conclusions obtained are therefore favorable to the integration of this type of devices on harbor breakwaters. Full article
(This article belongs to the Special Issue Advances in Ocean Wave Energy Conversion)
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Open AccessArticle
KNSwing—On the Mooring Loads of a Ship-Like Wave Energy Converter
J. Mar. Sci. Eng. 2019, 7(2), 29; https://doi.org/10.3390/jmse7020029
Received: 10 January 2019 / Revised: 23 January 2019 / Accepted: 26 January 2019 / Published: 1 February 2019
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Abstract
The critical function of keeping a floating Wave Energy Converter in position is done by a mooring system. Several WECs have been lost due to failed moorings, indicating that extreme loads, reliability and durability are very important aspects. An understanding of the interaction [...] Read more.
The critical function of keeping a floating Wave Energy Converter in position is done by a mooring system. Several WECs have been lost due to failed moorings, indicating that extreme loads, reliability and durability are very important aspects. An understanding of the interaction between the WEC’s motion in large waves and the maximum mooring loads can be gained by investigating the system at model scale supported by numerical models. This paper describes the testing of a novel attenuator WEC design called KNSwing. It is shaped like a ship facing the waves with its bow, which results in low mooring loads and small motions in most wave conditions when the structure is longer than the waves. The concept is tested using an experimental model at scale 1:80 in regular and irregular waves, moored using rubber bands to simulate synthetic moorings. The experimental results are compared to numerical simulations done using the OrcaFlex software. The experimental results show that the WEC and the mooring system survives well, even under extreme and breaking waves. The numerical model coefficient concerning the nonlinear drag term for the surge motion is validated using decay tests. The numerical results compare well to the experiments and, thereby, the numerical model can be further used to optimize the mooring system. Full article
(This article belongs to the Special Issue Advances in Ocean Wave Energy Conversion)
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Open AccessArticle
Energetic Potential Assessment of Wind-Driven Waves on the South-Southeastern Brazilian Shelf
J. Mar. Sci. Eng. 2019, 7(2), 25; https://doi.org/10.3390/jmse7020025
Received: 30 November 2018 / Revised: 14 January 2019 / Accepted: 21 January 2019 / Published: 23 January 2019
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Abstract
Global electric energy demand is constantly growing, consequently leading towards the usage of renewable energy sources reducing pollution and increasing sustainability. The ocean is a poorly explored renewable energy source; thus, to evaluate the Brazilian wave energy budget, this study investigated the mean [...] Read more.
Global electric energy demand is constantly growing, consequently leading towards the usage of renewable energy sources reducing pollution and increasing sustainability. The ocean is a poorly explored renewable energy source; thus, to evaluate the Brazilian wave energy budget, this study investigated the mean behaviour of the wave power rate on the south-southeastern Brazilian Shelf as well as analysed the temporal variability of the wave power rate at the most energetic locations near the coast. Three locations were examined, namely Laguna, Ilhabela and Farol Island, based on the criteria of high means and small standard deviations. The mean wave power rate was approximately 9.08 kW / m on Laguna, 10.01 kW / m on Ilhabela and 15.93 kW / m on Farol Island. The standard deviation identified in the three locations reached values of 6.47 kW / m on Laguna, 7.59 kW / m on Ilhabela and 13.51 kW / m on Farol Island. Temporal variability analysis was conducted through wavelet analysis. The results show a dominant yearly cycle with a background presence of synoptic cycles, with little deviation between the locations. The El Niño southern oscillation plays a minor role on the energy spectrum of Laguna and does not have a significant influence on Ilhabela and Farol Island. Full article
(This article belongs to the Special Issue Advances in Ocean Wave Energy Conversion)
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Open AccessArticle
Modelling Approaches of a Closed-Circuit OWC Wave Energy Converter
J. Mar. Sci. Eng. 2019, 7(2), 23; https://doi.org/10.3390/jmse7020023
Received: 18 December 2018 / Revised: 11 January 2019 / Accepted: 16 January 2019 / Published: 22 January 2019
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Abstract
The Tupperwave device is a wave energy converter based on the Oscillating Water Column (OWC) concept. Unlike conventional OWC devices, which are opened to the atmosphere, the Tupperwave device works in closed-circuit and uses non-return valves and accumulator chambers to create a smooth [...] Read more.
The Tupperwave device is a wave energy converter based on the Oscillating Water Column (OWC) concept. Unlike conventional OWC devices, which are opened to the atmosphere, the Tupperwave device works in closed-circuit and uses non-return valves and accumulator chambers to create a smooth unidirectional flow across a unidirectional turbine. The EU-funded OceanEraNet project called Tupperwave was undertaken by a consortium of academic and industrial partners, aimed at designing and modelling the Tupperwave device. The device was numerically modelled using two different methods. It was also physically modelled at the laboratory scale. The various modelling methods are discussed and compared. An analysis of the dependence of the device efficiency on the valves and turbine aerodynamic damping is carried out, using both physical and numerical approaches. Full article
(This article belongs to the Special Issue Advances in Ocean Wave Energy Conversion)
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Open AccessArticle
Numerical Modeling and Dynamic Analysis of a Wave-Powered Reverse-Osmosis System
J. Mar. Sci. Eng. 2018, 6(4), 132; https://doi.org/10.3390/jmse6040132
Received: 6 September 2018 / Revised: 24 October 2018 / Accepted: 26 October 2018 / Published: 8 November 2018
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Abstract
A wave energy converter (WEC) system has the potential to convert the wave energy resource directly into the high-pressure flow that is needed by the desalination system to pump saltwater to the reverse-osmosis membrane and provide the required pressure level to generate freshwater. [...] Read more.
A wave energy converter (WEC) system has the potential to convert the wave energy resource directly into the high-pressure flow that is needed by the desalination system to pump saltwater to the reverse-osmosis membrane and provide the required pressure level to generate freshwater. In this study, a wave-to-water numerical model was developed to investigate the potential use of a wave-powered desalination system (WPDS) for water production. The model was developed by coupling a time-domain radiation-and-diffraction method-based numerical tool (WEC-Sim) for predicting the hydrodynamic performance of WECs with a solution-diffusion model that was used to simulate the reverse-osmosis (RO) process. The objective of this research is to evaluate the WPDS dynamics and the overall efficiency of the system. To evaluate the feasibility of the WPDS, the wave-to-water numerical model was applied to simulate a desalination system that used an oscillating surge WEC device to pump seawater through the system. The hydrodynamics WEC-Sim simulation results for the oscillating surge WEC device were validated against existing experimental data. The RO simulation was verified by comparing the results to those from the Dow Chemical Company’s reverse osmosis system analysis (ROSA) model, which has been widely used to design and simulate RO systems. The wave-to-water model was then used to analyze the WPDS under a range of wave conditions and for a two-WECs-coupled RO system to evaluate the influence of pressure and flow rate fluctuation on the WPDS performance. The results show that the instantaneous energy fluctuation from waves has a significant influence on the responding hydraulic pressure and flow rate, as well as the recovery ratio and, ultimately, the water-production quality. Nevertheless, it is possible to reduce the hydraulic fluctuation for different sea states while maintaining a certain level of freshwater production, and a WEC array that produces water can be a viable, near-term solution to the nation’s water supply. A discussion on the dynamic impact of hydraulic fluctuation on the WPDS performance and potential options to reduce the fluctuation and their trade-offs is also presented. Full article
(This article belongs to the Special Issue Advances in Ocean Wave Energy Conversion)
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Open AccessArticle
Analysis of Different Methods for Wave Generation and Absorption in a CFD-Based Numerical Wave Tank
J. Mar. Sci. Eng. 2018, 6(2), 73; https://doi.org/10.3390/jmse6020073
Received: 30 April 2018 / Revised: 6 June 2018 / Accepted: 10 June 2018 / Published: 14 June 2018
Cited by 5 | PDF Full-text (4083 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the performance of different wave generation and absorption methods in computational fluid dynamics (CFD)-based numerical wave tanks (NWTs) is analyzed. The open-source CFD code REEF3D is used, which solves the Reynolds-averaged Navier–Stokes (RANS) equations to simulate two-phase flow problems. The [...] Read more.
In this paper, the performance of different wave generation and absorption methods in computational fluid dynamics (CFD)-based numerical wave tanks (NWTs) is analyzed. The open-source CFD code REEF3D is used, which solves the Reynolds-averaged Navier–Stokes (RANS) equations to simulate two-phase flow problems. The water surface is computed with the level set method (LSM), and turbulence is modeled with the k-ω model. The NWT includes different methods to generate and absorb waves: the relaxation method, the Dirichlet-type method and active wave absorption. A sensitivity analysis has been conducted in order to quantify and compare the differences in terms of absorption quality between these methods. A reflection analysis based on an arbitrary number of wave gauges has been adopted to conduct the study. Tests include reflection analysis of linear, second- and fifth-order Stokes waves, solitary waves, cnoidal waves and irregular waves generated in an NWT. Wave breaking over a sloping bed and wave forces on a vertical cylinder are calculated, and the influence of the reflections on the wave breaking location and the wave forces on the cylinder is investigated. In addition, a comparison with another open-source CFD code, OpenFOAM, has been carried out based on published results. Some differences in the calculated quantities depending on the wave generation and absorption method have been observed. The active wave absorption method is seen to be more efficient for long waves, whereas the relaxation method performs better for shorter waves. The relaxation method-based numerical beach generally results in lower reflected waves in the wave tank for most of the cases simulated in this study. The comparably better performance of the relaxation method comes at the cost of larger computational requirements due to the relaxation zones that have to be included in the domain. The reflections in the NWT in REEF3D are generally lower than the published results for reflections using the active wave absorption method in the NWT based on OpenFOAM. Full article
(This article belongs to the Special Issue Advances in Ocean Wave Energy Conversion)
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Open AccessArticle
Deployment and Maintenance of Wave Energy Converters at the Lysekil Research Site: A Comparative Study on the Use of Divers and Remotely-Operated Vehicles
J. Mar. Sci. Eng. 2018, 6(2), 39; https://doi.org/10.3390/jmse6020039
Received: 15 February 2018 / Revised: 20 March 2018 / Accepted: 26 March 2018 / Published: 12 April 2018
Cited by 1 | PDF Full-text (4460 KB) | HTML Full-text | XML Full-text
Abstract
Ocean renewable technologies have been rapidly developing over the past years. However, current high installation, operation, maintenance, and decommissioning costs are hindering these offshore technologies to reach a commercialization stage. In this paper we focus on the use of divers and remotely-operated vehicles [...] Read more.
Ocean renewable technologies have been rapidly developing over the past years. However, current high installation, operation, maintenance, and decommissioning costs are hindering these offshore technologies to reach a commercialization stage. In this paper we focus on the use of divers and remotely-operated vehicles during the installation and monitoring phase of wave energy converters. Methods and results are based on the wave energy converter system developed by Uppsala University, and our experience in offshore deployments obtained during the past eleven years. The complexity of underwater operations, carried out by either divers or remotely-operated vehicles, is emphasized. Three methods for the deployment of wave energy converters are economically and technically analyzed and compared: one using divers alone, a fully-automated approach using remotely-operated vehicles, and an intermediate approach, involving both divers and underwater vehicles. The monitoring of wave energy converters by robots is also studied, both in terms of costs and technical challenges. The results show that choosing an autonomous deployment method is more advantageous than a diver-assisted method in terms of operational time, but that numerous factors prevent the wide application of robotized operations. Technical solutions are presented to enable the use of remotely-operated vehicles instead of divers in ocean renewable technology operations. Economically, it is more efficient to use divers than autonomous vehicles for the deployment of six or fewer wave energy converters. From seven devices, remotely-operated vehicles become advantageous. Full article
(This article belongs to the Special Issue Advances in Ocean Wave Energy Conversion)
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Open AccessArticle
Control of Wave Energy Converters with Discrete Displacement Hydraulic Power Take-Off Units
J. Mar. Sci. Eng. 2018, 6(2), 31; https://doi.org/10.3390/jmse6020031
Received: 7 February 2018 / Revised: 2 March 2018 / Accepted: 26 March 2018 / Published: 2 April 2018
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Abstract
The control of ocean Wave Energy Converters (WECs) impacts the harvested energy. Several control methods have been developed over the past few decades to maximize the harvested energy. Many of these methods were developed based on an unconstrained dynamic model assuming an ideal [...] Read more.
The control of ocean Wave Energy Converters (WECs) impacts the harvested energy. Several control methods have been developed over the past few decades to maximize the harvested energy. Many of these methods were developed based on an unconstrained dynamic model assuming an ideal power take-off (PTO) unit. This study presents numerical tests and comparisons of a few recently developed control methods. The testing is conducted using a numerical simulator that simulates a hydraulic PTO. The PTO imposes constraints on the maximum attainable control force and maximum stroke. In addition, the PTO has its own dynamics, which may impact the performance of some control strategies. Full article
(This article belongs to the Special Issue Advances in Ocean Wave Energy Conversion)
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Open AccessArticle
Small-Scale Renewable Energy Converters for Battery Charging
J. Mar. Sci. Eng. 2018, 6(1), 26; https://doi.org/10.3390/jmse6010026
Received: 14 January 2018 / Revised: 9 February 2018 / Accepted: 5 March 2018 / Published: 13 March 2018
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Abstract
This paper presents two wave energy concepts for small-scale electricity generation. In the presented case, these concepts are installed on the buoy of a heaving, point-absorbing wave energy converter (WEC) for large scale electricity production. In the studied WEC, developed by Uppsala University, [...] Read more.
This paper presents two wave energy concepts for small-scale electricity generation. In the presented case, these concepts are installed on the buoy of a heaving, point-absorbing wave energy converter (WEC) for large scale electricity production. In the studied WEC, developed by Uppsala University, small-scale electricity generation in the buoy is needed to power a tidal compensating system designed to increase the performance of the WEC in areas with high tides. The two considered and modeled concepts are an oscillating water column (OWC) and a heaving point absorber. The results indicate that the OWC is too small for the task and does not produce enough energy. On the other hand, the results show that a hybrid system composed of a small heaving point absorber combined with a solar energy system would be able to provide a requested minimum power of around 37.7 W on average year around. The WEC and solar panel complement each other, as the WEC produces enough energy by itself during wintertime (but not in the summer), while the solar panel produces enough energy in the summer (but not in the winter). Full article
(This article belongs to the Special Issue Advances in Ocean Wave Energy Conversion)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

1. KNSwing – On the Bending Moment and Mooring Loads of a Ship like Wave Energy Converters

Kim Nielsen; Harry Bingham; Jonas Bjerg Thomsen

Abstract: This paper presents a study on the Midship bending moment and the mooring loads of a wave energy converter shaped like a ship moored to face the incoming waves with its bow.
The concept is called KNSwing, a design which builds on the results from previous wave energy concepts such as the Japanese Kaimai and Moody’s I-Beam Attenuator from the UK which were both investigated in the early 1970s.
Specifically, the paper presents small scale 1:80 experimental results focused on measuring the Midship bending Moment and mooring loads obtained during a third round of experiments carried out at Queens University Belfast in the UK. The mooring load results will be compared to numerical models developed at AAU. The midship bending moment will be compared to calculations provided by DTU. [...]

J. Mar. Sci. Eng. EISSN 2077-1312 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
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