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Special Issue "Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind"

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "Energy Sources".

Deadline for manuscript submissions: closed (31 October 2018)

Special Issue Editors

Guest Editor
Prof. Dr. Eugen Rusu

Department of Applied Mechanics, University Dunarea de Jos of Galati, Strada Domnească 47, Galați, Romania
Website | E-Mail
Interests: renewable energy extraction in marine environment, evaluation of the wave and wind resources and identification of the hot energy spots; Efficiency assessments performed for various types of wave energy converters and wind turbines in different marine environments; Studies of the possible coastal impact of the future marine energy parks; Modelling and analysis of the environmental data in marine environment, correlated with the assessment of the natural and technological risks that may occur in these zones
Guest Editor
Dr. Vengatesan Venugopal

Institute for Energy Systems, The University of Edinburgh, Edinburgh EH8 9YL, UK
Website | E-Mail
Interests: wave energy; tidal energy; offshore wind energy; resource assessment; wave and tidal energy arrays modelling; environmental impact assessment; numerical and physical model testing of offshore structures including marine energy converters, extreme wave analysis, coastal protection structures

Special Issue Information

Dear Colleagues,

We are inviting submissions to a Special Issue of Energies on the subject area of "Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind”. The conversion of energy from ocean waves, tides and offshore wind into electricity could play an important role in globally meeting growing energy demands, diversify energy supply, reduce the dependency of carbon-based fuel sources, and save the world from climate change. Energy from the above mentioned ocean renewable sources is abundant and the amount of energy that can be generated using the existing technologies varies from site-to-site and from day-to-day, depending on location and weather conditions. The associated technologies for the energy conversion in marine environment are crucial to achieving critical global targets in energy efficiency. While considerable progress has been made in the past decade in harvesting marine energy, still great challenges exist in the design and implementation of cost effective technologies that could survive in the harsh marine environment. Researchers, engineers and scientists worldwide are working to develop cost effective marine energy technologies through their research, and enormous data and information are being released into the public domain. Through this Special Issue we hope to bring out additional wealth of information related to offshore marine energy technologies and environments to the readers of Energies.

Topics of interest for publication include, but are not limited to:

  • Resource modeling of waves, tides and offshore wind;
  • Technologies for the wave energy conversion;
  • Technologies for the tidal energy conversion;
  • Technologies for fixed and floating offshore wind energy conversion;
  • Multi-energy platform concepts;
  • Numerical and physical modelling of marine energy converters;
  • Modelling of arrays of marine energy converters;
  • Foundations, moorings and anchors for marine energy converters;
  • Risk and reliability assessment of marine energy converters;
  • Environmental impact of the marine energy farms;
  • Economic assessments and LCOE projections for the marine energy.
Prof. Dr. Eugen Rusu
Dr. Vengatesan Venugopal
Guest Editors

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. Energies 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 1600 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
  • tidal energy
  • offshore wind energy
  • energy conversion
  • resource assessment
  • multi-platform concepts
  • arrays of energy converters
  • numerical modelling
  • laboratory modeling
  • environmental impact
  • economic assessments
  • Levelised Cost of Energy

Published Papers (17 papers)

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Research

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Open AccessArticle Validation of a Coupled Electrical and Hydrodynamic Simulation Model for a Vertical Axis Marine Current Energy Converter
Energies 2018, 11(11), 3067; https://doi.org/10.3390/en11113067
Received: 28 September 2018 / Revised: 30 October 2018 / Accepted: 30 October 2018 / Published: 7 November 2018
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Abstract
This paper validates a simulation model that couples an electrical model in Simulink with a hydrodynamic vortex-model by comparing with experimental data. The simulated system is a vertical axis current turbine connected to a permanent magnet synchronous generator in a direct drive configuration.
[...] Read more.
This paper validates a simulation model that couples an electrical model in Simulink with a hydrodynamic vortex-model by comparing with experimental data. The simulated system is a vertical axis current turbine connected to a permanent magnet synchronous generator in a direct drive configuration. Experiments of load and no load operation were conducted to calibrate the losses of the turbine, generator and electrical system. The power capture curve of the turbine has been simulated as well as the behaviour of a step response for a change in tip speed ratio. The simulated results agree well with experimental data except at low rotational speed where the accuracy of the calibration of the drag losses is reduced. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessArticle Fuzzy Supervision Based-Pitch Angle Control of a Tidal Stream Generator for a Disturbed Tidal Input
Energies 2018, 11(11), 2989; https://doi.org/10.3390/en11112989
Received: 30 September 2018 / Revised: 23 October 2018 / Accepted: 27 October 2018 / Published: 1 November 2018
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Abstract
Energy originating in tidal and ocean currents appears to be more intense and predictable than other renewables. In this area of research, the Tidal Stream Generator (TSG) power plant is one of the most recent forms of renewable energy to be developed. The
[...] Read more.
Energy originating in tidal and ocean currents appears to be more intense and predictable than other renewables. In this area of research, the Tidal Stream Generator (TSG) power plant is one of the most recent forms of renewable energy to be developed. The main feature of this energy converter is related to the input resource which is the tidal current speed. Since its behaviour is variable and with disturbances, these systems must be able to maintain performance despite the input variations. This article deals with the design and control of a tidal stream converter system. The Fuzzy Gain Scheduling (FGS) technique is used to control the blade pitch angle of the turbine, in order to protect the plant in the case of a strong tidal range. Rotational speed control is investigated by means of the back-to-back power converters. The optimal speed is provided using the Maximum Power Point Tracking (MPPT) strategy to harness maximum power from the tidal speed. To verify the robustness of the developed methods, two scenarios of a disturbed tidal resource with regular and irregular conditions are considered. The performed results prove the output power optimization and adaptive change of the pitch angle control to maintain the plant within the tolerable limits. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessArticle A Study on Electrical Power for Multiple Linear Wave Energy Converter Considering the Interaction Effect
Energies 2018, 11(11), 2964; https://doi.org/10.3390/en11112964
Received: 20 September 2018 / Revised: 24 October 2018 / Accepted: 26 October 2018 / Published: 1 November 2018
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Abstract
A linear electrical generator can be used on wave energy converter for converting the kinetic energy of a floating structure to the electricity. A wave farm consists of multiple wave energy converters which equipped in a sea area. In the present paper, a
[...] Read more.
A linear electrical generator can be used on wave energy converter for converting the kinetic energy of a floating structure to the electricity. A wave farm consists of multiple wave energy converters which equipped in a sea area. In the present paper, a numerical model is proposed considering not only the interference effect in the multiple floating structures, but also the controlling force of each linear electrical generator. In particular, the copper losses in the electrical generator is taken into account, when the electrical power is computed. In a case study, the heaving motions and electrical powers of the multiple wave energy converters are estimated in the straight arrangement and triangle arrangement. In addition, the average electrical power is analyzed in different distances of the floating structures. The aim of this paper is to clear the relationship between the interference effect and electric powers from wave energy converters. This will be useful for deciding the arrangement of multiple wave energy converters. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessArticle Adaptive Sliding Mode Control for a Double Fed Induction Generator Used in an Oscillating Water Column System
Energies 2018, 11(11), 2939; https://doi.org/10.3390/en11112939
Received: 23 September 2018 / Revised: 20 October 2018 / Accepted: 25 October 2018 / Published: 27 October 2018
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Abstract
Wave power conversion systems are nonlinear dynamical systems that must endure strong uncertainties. Efficiency is a key issue for these systems, and the application of robust control algorithms can improve it considerably. Wave power generation plants are typically built using variable speed generators,
[...] Read more.
Wave power conversion systems are nonlinear dynamical systems that must endure strong uncertainties. Efficiency is a key issue for these systems, and the application of robust control algorithms can improve it considerably. Wave power generation plants are typically built using variable speed generators, such as the doubly fed induction generator (DFIG). These generators, compared with fixed speed generators, are very versatile since the turbine speed may be adjusted to improve the efficiency of the whole system. Nevertheless, a suitable speed controller is required for these systems, which must be able to avoid the stalling phenomenon and track the optimal reference for the turbine. This paper proposes a sliding mode control scheme aimed at oscillating water column (OWC) generation plants using Wells turbines and DFIGs. The contributions of the paper are (1) an adaptive sliding mode control scheme that does not require calculating the bounds of the system uncertainties, (2) a Lyapunov analysis of stability for the control algorithm against system uncertainties and disturbances, and (3) a validation of the proposed control scheme through several simulation examples with the Matlab/Simulink suite. The performance results, obtained by means of simulations, for a wave power generation plant (1) evidence that this control scheme improves the power generation of the system and (2) prove that this control scheme is robust in the presence of disturbances. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessFeature PaperArticle Coupling Methodology for Studying the Far Field Effects of Wave Energy Converter Arrays over a Varying Bathymetry
Energies 2018, 11(11), 2899; https://doi.org/10.3390/en11112899
Received: 1 October 2018 / Revised: 16 October 2018 / Accepted: 18 October 2018 / Published: 25 October 2018
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Abstract
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
[...] Read more.
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. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessArticle A Study about Performance and Robustness of Model Predictive Controllers in a WEC System
Energies 2018, 11(10), 2857; https://doi.org/10.3390/en11102857
Received: 27 September 2018 / Revised: 18 October 2018 / Accepted: 19 October 2018 / Published: 22 October 2018
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Abstract
This work is located in a growing sector within the field of renewable energies, wave energy converters (WECs). Specifically, it focuses on one of the point absorber waves (PAWs) of the hybrid platform W2POWER. With the aim of maximizing the mechanical power extracted
[...] Read more.
This work is located in a growing sector within the field of renewable energies, wave energy converters (WECs). Specifically, it focuses on one of the point absorber waves (PAWs) of the hybrid platform W2POWER. With the aim of maximizing the mechanical power extracted from the waves by these WECs and reducing their mechanical fatigue, the design of five different model predictive controllers (MPCs) with hard and soft constraints has been carried out. As a contribution of this paper, two of the MPCs have been designed with the addition of an embedded integrator. In order to analyze and compare the MPCs with conventional PI type control, an exhaustive study about performance and robustness is realized through the computer simulations carried out, in which uncertainties in the WEC dynamics and JONSWAP spectrum are considered. The results obtained show how the MPCs with embedded integrator improve power production of the WEC system studied in this work. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessArticle Assessing the Macro-Economic Benefit of Installing a Farm of Oscillating Water Columns in Scotland and Portugal
Energies 2018, 11(10), 2824; https://doi.org/10.3390/en11102824
Received: 14 August 2018 / Revised: 27 September 2018 / Accepted: 16 October 2018 / Published: 19 October 2018
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Abstract
The nascent wave energy sector has the potential to contribute significantly to global renewables targets, yet at present there are no proven commercially viable technologies. Macro-economic assessment is seldom used to assess wave energy projects, yet can provide insightful information on the wider
[...] Read more.
The nascent wave energy sector has the potential to contribute significantly to global renewables targets, yet at present there are no proven commercially viable technologies. Macro-economic assessment is seldom used to assess wave energy projects, yet can provide insightful information on the wider economic benefits and can be used in conjunction with techno-economic analysis to inform policy makers, investors and funding bodies. Herein, we present a coupled techno–macro-economic model, which is used to assess the macro-economic benefit of installing a 5.25 MW farm of oscillating water column wave energy devices at two locations: Orkney in Scotland and Leixoes in Portugal. Through an input-output analysis, the wide-reaching macro-economic benefit of the prospective projects is highlighted; evidenced by the finding that all 29 industry sectors considered are either directly or indirectly stimulated by the project for both locations. Peak annual employment is expected to be 420 and 190 jobs in Portugal and Scotland respectively during the combined installation and manufacturing stage, with an associated peak annual GVA of over €16.6 m and €12.8 m. The discrepancies between the two locations is concluded to largely be a result of the site-specific attributes of the farm locations: specifically, increased water depth and distance to shore for the Portuguese site, resulting in higher costs associated with mooring and electrical cables and vessels. The insights gained through the presented results demonstrate the merit of macro-economic analysis for understanding the wider economic benefit of wave energy projects, while providing an understanding over key physical factors which will dominate estimated effects. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessArticle Energy Production Benefits by Wind and Wave Energies for the Autonomous System of Crete
Energies 2018, 11(10), 2741; https://doi.org/10.3390/en11102741
Received: 14 September 2018 / Revised: 4 October 2018 / Accepted: 9 October 2018 / Published: 12 October 2018
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Abstract
At autonomous electricity grids Renewable Energy (RE) contributes significantly to energy production. Offshore resources benefit from higher energy density, smaller visual impacts, and higher availability levels. Offshore locations at the West of Crete obtain wind availability ≈80%, combining this with the installation potential
[...] Read more.
At autonomous electricity grids Renewable Energy (RE) contributes significantly to energy production. Offshore resources benefit from higher energy density, smaller visual impacts, and higher availability levels. Offshore locations at the West of Crete obtain wind availability ≈80%, combining this with the installation potential for large scale modern wind turbines (rated power) then expected annual benefits are immense. Temporal variability of production is a limiting factor for wider adaptation of large offshore farms. To this end multi-generation with wave energy can alleviate issues of non-generation for wind. Spatio-temporal correlation of wind and wave energy production exhibit that wind and wave hybrid stations can contribute significant amounts of clean energy, while at the same time reducing spatial constrains and public acceptance issues. Offshore technologies can be combined as co-located or not, altering contribution profiles of wave energy to non-operating wind turbine production. In this study a co-located option contributes up to 626 h per annum, while a non co-located solution is found to complement over 4000 h of a non-operative wind turbine. Findings indicate the opportunities associated not only in terms of capital expenditure reduction, but also in the ever important issue of renewable variability and grid stability. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessArticle Optimal Design of Rated Wind Speed and Rotor Radius to Minimizing the Cost of Energy for Offshore Wind Turbines
Energies 2018, 11(10), 2728; https://doi.org/10.3390/en11102728
Received: 18 September 2018 / Revised: 29 September 2018 / Accepted: 1 October 2018 / Published: 11 October 2018
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Abstract
As onshore wind energy has depleted, the utilization of offshore wind energy has gradually played an important role in globally meeting growing green energy demands. However, the cost of energy (COE) for offshore wind energy is very high compared to the onshore one.
[...] Read more.
As onshore wind energy has depleted, the utilization of offshore wind energy has gradually played an important role in globally meeting growing green energy demands. However, the cost of energy (COE) for offshore wind energy is very high compared to the onshore one. To minimize the COE, implementing optimal design of offshore turbines is an effective way, but the relevant studies are lacking. This study proposes a method to minimize the COE of offshore wind turbines, in which two design parameters, including the rated wind speed and rotor radius are optimally designed. Through this study, the relation among the COE and the two design parameters is explored. To this end, based on the power-coefficient power curve model, the annual energy production (AEP) model is designed as a function of the rated wind speed and the Weibull distribution parameters. On the other hand, the detailed cost model of offshore turbines developed by the National Renewable Energy Laboratory is formulated as a function of the rated wind speed and the rotor radius. Then, the COE is formulated as the ratio of the total cost and the AEP. Following that, an iterative method is proposed to search the minimal COE which corresponds to the optimal rated wind speed and rotor radius. Finally, the proposed method has been applied to the wind classes of USA, and some useful findings have been obtained. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessArticle A Shape Optimization Method of a Specified Point Absorber Wave Energy Converter for the South China Sea
Energies 2018, 11(10), 2645; https://doi.org/10.3390/en11102645
Received: 9 September 2018 / Revised: 30 September 2018 / Accepted: 30 September 2018 / Published: 3 October 2018
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Abstract
In this paper, a shape optimization method of a truncated conical point absorber wave energy converter is proposed. This method converts the wave energy absorption efficiency into the matching problem between the wave spectrum of the South China Sea and the buoy’s absorption
[...] Read more.
In this paper, a shape optimization method of a truncated conical point absorber wave energy converter is proposed. This method converts the wave energy absorption efficiency into the matching problem between the wave spectrum of the South China Sea and the buoy’s absorption power spectrum. An objective function which combines these two spectra is established to reflect the energy absorbing efficiency. By applying Taguchi design, the frequency domain hydrodynamic analysis and the response surface method (RSM), the radius, cone angle and draft of the buoy are optimized. Since the significant influence of power take-off system (PTO) on energy absorption, the optimal PTO damping under random wave conditions is also studied. The optimal shape is acquired by maximizing the energy absorbing efficiency. Four types of performance and the influence of each geometrical parameter are also obtained. In addition, the cause of the trend of performance as well as the effects of adjusting the input parameters are analyzed. This study can provide guidance for the shape optimization of multi-parameter buoys. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessArticle Evaluation of Some State-Of-The-Art Wind Technologies in the Nearshore of the Black Sea
Energies 2018, 11(9), 2452; https://doi.org/10.3390/en11092452
Received: 25 August 2018 / Revised: 11 September 2018 / Accepted: 12 September 2018 / Published: 15 September 2018
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Abstract
The main objective of this work was to evaluate the nearshore wind resources in the Black Sea area by using a high resolution wind database (ERA-Interim). A subsequent objective was to estimate what type of wind turbines and wind farm configurations would be
[...] Read more.
The main objective of this work was to evaluate the nearshore wind resources in the Black Sea area by using a high resolution wind database (ERA-Interim). A subsequent objective was to estimate what type of wind turbines and wind farm configurations would be more suitable for this coastal environment. A more comprehensive picture of these resources was provided by including some satellite measurements, which were also used to assess the wind conditions in the vicinity of some already operating European wind projects. Based on the results of the present work, it seems that the Crimea Peninsula has the best wind resources. However, considering the current geopolitical situation, it seems that the sites on the western part of this basin (Romania and Bulgaria) would represent more viable locations for developing offshore wind projects. Since there are currently no operational wind projects in this marine area, some possible configurations for the future wind farms are proposed. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessArticle On the Accuracy of Three-Dimensional Actuator Disc Approach in Modelling a Large-Scale Tidal Turbine in a Simple Channel
Energies 2018, 11(8), 2151; https://doi.org/10.3390/en11082151
Received: 17 July 2018 / Revised: 10 August 2018 / Accepted: 10 August 2018 / Published: 17 August 2018
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Abstract
To date, only a few studies have examined the execution of the actuator disc approximation for a full-size turbine. Small-scale models have fewer constraints than large-scale models because the range of time-scale and length-scale is narrower. Hence, this article presents the methodology in
[...] Read more.
To date, only a few studies have examined the execution of the actuator disc approximation for a full-size turbine. Small-scale models have fewer constraints than large-scale models because the range of time-scale and length-scale is narrower. Hence, this article presents the methodology in implementing the actuator disc approach via the Reynolds-Averaged Navier-Stokes (RANS) momentum source term for a 20-m diameter turbine in an idealised channel. A structured grid, which varied from 0.5 m to 4 m across rotor diameter and width was used at the turbine location to allow for better representation of the disc. The model was tuned to match known coefficient of thrust and operational profiles for a set of validation cases based on published experimental data. Predictions of velocity deficit and turbulent intensity became almost independent of the grid density beyond 11 diameters downstream of the disc. However, in several instances the finer meshes showed larger errors than coarser meshes when compared to the measurements data. This observation was attributed to the way nodes were distributed across the disc swept area. The results demonstrate that the accuracy of the actuator disc was highly influenced by the vertical resolutions, as well as the grid density of the disc enclosure. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessArticle A Novel Method for Estimating Wave Energy Converter Performance in Variable Bathymetry Regions and Applications
Energies 2018, 11(8), 2092; https://doi.org/10.3390/en11082092
Received: 24 July 2018 / Revised: 3 August 2018 / Accepted: 10 August 2018 / Published: 11 August 2018
Cited by 2 | PDF Full-text (10116 KB) | HTML Full-text | XML Full-text
Abstract
A numerical model is presented for the estimation of Wave Energy Converter (WEC) performance in variable bathymetry regions, taking into account the interaction of the floating units with the bottom topography. The proposed method is based on a coupled-mode model for the propagation
[...] Read more.
A numerical model is presented for the estimation of Wave Energy Converter (WEC) performance in variable bathymetry regions, taking into account the interaction of the floating units with the bottom topography. The proposed method is based on a coupled-mode model for the propagation of the water waves over the general bottom topography, in combination with a Boundary Element Method for the treatment of the diffraction/radiation problems and the evaluation of the flow details on the local scale of the energy absorbers. An important feature of the present method is that it is free of mild bottom slope assumptions and restrictions and it is able to resolve the 3D wave field all over the water column, in variable bathymetry regions including the interactions of floating bodies of general shape. Numerical results are presented concerning the wave field and the power output of a single device in inhomogeneous environment, focusing on the effect of the shape of the floater. Extensions of the method to treat the WEC arrays in variable bathymetry regions are also presented and discussed. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessArticle Wave Power as Solution for Off-Grid Water Desalination Systems: Resource Characterization for Kilifi-Kenya
Energies 2018, 11(4), 1004; https://doi.org/10.3390/en11041004
Received: 16 February 2018 / Revised: 26 March 2018 / Accepted: 26 March 2018 / Published: 20 April 2018
Cited by 1 | PDF Full-text (7617 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Freshwater scarcity is one of humanity’s reoccurring problems that hamper socio-economic development in many regions across the globe. In coastal areas, seawater can be desalinated through reverse osmosis (RO) and transformed into freshwater for human use. Desalination requires large amounts of energy, mostly
[...] Read more.
Freshwater scarcity is one of humanity’s reoccurring problems that hamper socio-economic development in many regions across the globe. In coastal areas, seawater can be desalinated through reverse osmosis (RO) and transformed into freshwater for human use. Desalination requires large amounts of energy, mostly in the form of a reliable electricity supply, which in many cases is supplied by diesel generators. The objective of this work is to analyze the wave power resource availability in Kilifi-Kenya and evaluate the possible use of wave power converter (WEC) to power desalination plants. A particular focus is given use of WECs developed by Uppsala University (UU-WEC). The results here presented were achieved using reanalysis—wave data revealed that the local wave climate has an approximate annual mean of 7 kW/m and mode of 5 kW/m. Significant wave height and wave mean period are within 0.8–2 m and 7–8 s respectively, with a predominant wave mean direction from southeast. The seasonal cycle appeared to be the most relevant for energy conversion, having the highest difference of 6 kW/m, in which April is the lowest (3.8 kW/m) and August is the peak (10.5 kW/m). In such mild wave climates, the UU–WEC and similar devices can be suitable for ocean energy harvesting for water desalination systems. Technically, with a capacity factor of 30% and energy consumption of 3 kWh/m3, a coastal community of about five thousand inhabitants can be provided of freshwater by only ten WECs with installed capacity of 20 kW. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessArticle Numerical Modeling of the Wave Energy Propagation in the Iberian Nearshore
Energies 2018, 11(4), 980; https://doi.org/10.3390/en11040980
Received: 30 March 2018 / Revised: 13 April 2018 / Accepted: 13 April 2018 / Published: 18 April 2018
Cited by 2 | PDF Full-text (53301 KB) | HTML Full-text | XML Full-text
Abstract
In the present work the wave energy propagation patterns in the western side of the Iberian nearshore were evaluated. This assessment takes into account the results provided by a wave modelling system based on spectral phase averaged wave models, which considers subsequent computational
[...] Read more.
In the present work the wave energy propagation patterns in the western side of the Iberian nearshore were evaluated. This assessment takes into account the results provided by a wave modelling system based on spectral phase averaged wave models, which considers subsequent computational domains with increasing resolution towards the coast. The system was previously validated against both in situ measurements and remotely sensed data. Moreover, several data assimilation techniques were implemented as well. In this way, the reliability of the wave predictions was significantly increased. Although extended wave hindcasts have already been carried out close to the Iberian coast of the Atlantic Ocean, including wave energy assessments, they might not be completely accurate because of recent changes in the dynamics of the ocean and coastal wave climate. Thus, the present work considers wave nowcasts that correspond to the most recent and relevant wave energy propagation patterns in the targeted coastal environment. In order to perform this analysis, four different computational levels were considered. The first level corresponds to the sub oceanic domain and it is linked directly to the oceanic wave model, which is implemented over the entire North Atlantic Ocean. The second is related to the coarser computational domains of the coastal areas, while the third relates to the high-resolution domains. These three levels are defined as spherical coordinates (longitude, latitude). Finally, the last computational level includes some coastal areas which have the highest spatial resolution, defined considering the Cartesian coordinates. Moreover, for each level several computational domains have been considered. This work illustrates the most recent and significant wave transformation and energy propagation patterns corresponding to 18 computational domains with various resolutions in the western Iberian coastal environment. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessArticle A Novel Hybrid Wind-Wave Energy Converter for Jacket-Frame Substructures
Energies 2018, 11(3), 637; https://doi.org/10.3390/en11030637
Received: 27 February 2018 / Revised: 9 March 2018 / Accepted: 11 March 2018 / Published: 13 March 2018
Cited by 3 | PDF Full-text (5493 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The growth of the offshore wind industry in the last couple of decades has made this technology a key player in the maritime sector. The sustainable development of the offshore wind sector is crucial for this to consolidate within a global scenario of
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The growth of the offshore wind industry in the last couple of decades has made this technology a key player in the maritime sector. The sustainable development of the offshore wind sector is crucial for this to consolidate within a global scenario of climate change and increasing threats to the marine environment. In this context, multipurpose platforms have been proposed as a sustainable approach to harnessing different marine resources and combining their use under the same platform. Hybrid wind-wave systems are a type of multipurpose platform where a single platform combines the exploitation of offshore wind and wave energy. In particular, this paper deals with a novel hybrid wind-wave system that integrates an oscillating water column wave energy converter with an offshore wind turbine on a jacket-frame substructure. The main objective of this paper is to characterise the hydrodynamic response of the WEC sub-system of this hybrid energy converter. A 1:50 scale model was tested under regular and irregular waves to characterise the hydrodynamic response of the WEC sub-system. The results from this analysis lead to the proof of concept of this novel hybrid system; but additionally, to characterising its behaviour and interaction with the wave field, which is a requirement for fully understanding the benefits of hybrid systems. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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Open AccessReview Electrical Power Supply of Remote Maritime Areas: A Review of Hybrid Systems Based on Marine Renewable Energies
Energies 2018, 11(7), 1904; https://doi.org/10.3390/en11071904
Received: 14 May 2018 / Revised: 16 June 2018 / Accepted: 16 July 2018 / Published: 20 July 2018
Cited by 1 | PDF Full-text (1084 KB) | HTML Full-text | XML Full-text
Abstract
Ocean energy holds out great potential for supplying remote maritime areas with their energy requirements, where the grid size is often small and unconnected to a continental grid. Thanks to their high maturity and competitive price, solar and wind energies are currently the
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Ocean energy holds out great potential for supplying remote maritime areas with their energy requirements, where the grid size is often small and unconnected to a continental grid. Thanks to their high maturity and competitive price, solar and wind energies are currently the most used to provide electrical energy. However, their intermittency and variability limit the power supply reliability. To solve this drawback, storage systems and Diesel generators are often used. Otherwise, among all marine renewable energies, tidal and wave energies are reaching an interesting technical level of maturity. The better predictability of these sources makes them more reliable than other alternatives. Thus, combining different renewable energy sources would reduce the intermittency and variability of the total production and so diminish the storage and genset requirements. To foster marine energy integration and new multisource system development, an up-to-date review of projects already carried out in this field is proposed. This article first presents the main characteristics of the different sources which can provide electrical energy in remote maritime areas: solar, wind, tidal, and wave energies. Then, a review of multi-source systems based on marine energies is presented, concerning not only industrial projects but also concepts and research work. Finally, the main advantages and limits are discussed. Full article
(This article belongs to the Special Issue Offshore Renewable Energy: Ocean Waves, Tides and Offshore Wind)
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