Ocean Wave Energy Conversion

A special issue of Journal of Marine Science and Engineering (ISSN 2077-1312).

Deadline for manuscript submissions: closed (30 June 2016) | Viewed by 37391

Special Issue Editor

Environmental Hydraulics Institute of Cantabria “IHCantabria”, Univ. Cantabria, C/Isabel Torres n15, 39011 Santander, Cantabria, Spain
Interests: offshore wind energy; offshore engineering; marine renewable energies; seakeeping analysis; mooring system design; floating offshore wind platform design
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Special Issue Information

Dear Colleagues,

Wave energy is one of the most promising untapped ocean energy resources. During the last 10 years, interest in this source of energy has increased exponentially, and very interesting advances have been made from different points of view. An important scientific and technical effort has been done in resource assessment techniques, basic hydrodynamics, PTO development, control system, array design and optimization, mooring systems, materials and mechanical engineering (fatigue, corrosion, etc.), Environmental Impact Assessment, operation and maintenance, wave energy integration in multi-use platforms, etc. Advanced numerical models have been used as a basis for these developments. Extensive physical model tests have been also carried out by different developers, yielding in an important know-how increase. However, what differentiates the current status of the sector from past initiatives is the number of sea trials already carried out, on-going, and planned (i.e., EMEC experience and Plocan, and, more recently, sea trials, among others). This means that strong financial investments have also been made in a very promising sector.

This Special Issue will provide a compilation of the state of wave energy from a wide perspective: resource analysis, numerical models, physical model testing, PTO engineering, and their integration into new wave energy developments. Papers that deal with wave energy in the following areas are invited:

  • Resource assessment
  • New and advanced numerical models
  • Physical model tests (laboratory and field experiences)
  • PTO and control systems
  • Mooring systems
  • Array modeling and simulation
  • Operation and maintenance
  • Integration of wave energy systems in multi-use platforms

The Special Issue aims to compile the current state of the art and future developments of wave energy engineering.

Dr. Raúl Guanche García
Guest Editor

Manuscript Submission Information

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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 2600 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 resource
  • Power Take Off (PTO)
  • Mooring and anchoring system
  • Wave-to-wire models
  • CFD models
  • Numerical models
  • Physical model testing
  • Capture width

Published Papers (6 papers)

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Research

4671 KiB  
Article
Line Force and Damping at Full and Partial Stator Overlap in a Linear Generator for Wave Power
by Liselotte Ulvgård, Linnea Sjökvist, Malin Göteman and Mats Leijon
J. Mar. Sci. Eng. 2016, 4(4), 81; https://doi.org/10.3390/jmse4040081 - 28 Nov 2016
Cited by 17 | Viewed by 4986
Abstract
A full scale linear generator for wave power has been experimentally evaluated by measuring the line force and translator position throughout the full translator stroke. The measured line force, in relation to translator speed, generator damping and stator overlap, has been studied by [...] Read more.
A full scale linear generator for wave power has been experimentally evaluated by measuring the line force and translator position throughout the full translator stroke. The measured line force, in relation to translator speed, generator damping and stator overlap, has been studied by comparing the line force and the damping coefficient, γ , for multiple load cases along the translator stroke length. The study also compares the generator’s behavior during upward and downward motion, studies oscillations and determines the no load losses at two different speeds. The generator damping factor, γ , was determined for five different load cases during both upward and downward motion. The γ value was found to be constant for full stator overlap and to decrease linearly with a decreasing overlap, as the translator moved towards the endstops. The decline varied with the external load case, as previously suggested but not shown. In addition, during partial stator overlap, a higher γ value was noted as the translator was leaving the stator, compared to when it was entering the stator. Finally, new insights were gained regarding how translator weight and generator damping will affect the translator downward motion during offshore operation. This is important for power production and for avoiding damaging forces acting on the wave energy converter during operation. Full article
(This article belongs to the Special Issue Ocean Wave Energy Conversion)
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1792 KiB  
Article
Wave Energy Converter Annual Energy Production Uncertainty Using Simulations
by Clayton E. Hiles, Scott J. Beatty and Adrian De Andres
J. Mar. Sci. Eng. 2016, 4(3), 53; https://doi.org/10.3390/jmse4030053 - 02 Sep 2016
Cited by 21 | Viewed by 5491
Abstract
Critical to evaluating the economic viability of a wave energy project is: (1) a robust estimate of the electricity production throughout the project lifetime and (2) an understanding of the uncertainty associated with said estimate. Standardization efforts have established mean annual energy production [...] Read more.
Critical to evaluating the economic viability of a wave energy project is: (1) a robust estimate of the electricity production throughout the project lifetime and (2) an understanding of the uncertainty associated with said estimate. Standardization efforts have established mean annual energy production (MAEP) as the metric for quantification of wave energy converter (WEC) electricity production and the performance matrix approach as the appropriate method for calculation. General acceptance of a method for calculating the MAEP uncertainty has not yet been achieved. Several authors have proposed methods based on the standard engineering approach to error propagation, however, a lack of available WEC deployment data has restricted testing of these methods. In this work the magnitude and sensitivity of MAEP uncertainty is investigated. The analysis is driven by data from simulated deployments of 2 WECs of different operating principle at 4 different locations. A Monte Carlo simulation approach is proposed for calculating the variability of MAEP estimates and is used to explore the sensitivity of the calculation. The uncertainty of MAEP ranged from 2%–20% of the mean value. Of the contributing uncertainties studied, the variability in the wave climate was found responsible for most of the uncertainty in MAEP. Uncertainty in MAEP differs considerably between WEC types and between deployment locations and is sensitive to the length of the input data-sets. This implies that if a certain maximum level of uncertainty in MAEP is targeted, the minimum required lengths of the input data-sets will be different for every WEC-location combination. Full article
(This article belongs to the Special Issue Ocean Wave Energy Conversion)
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1736 KiB  
Article
On the Analysis of a Wave Energy Farm with Focus on Maintenance Operations
by Giovanni Rinaldi, Philipp R. Thies, Richard Walker and Lars Johanning
J. Mar. Sci. Eng. 2016, 4(3), 51; https://doi.org/10.3390/jmse4030051 - 23 Aug 2016
Cited by 21 | Viewed by 6363
Abstract
Wave energy has a promising technical potential that could contribute to the future energy mix. However, costs related to the deployment of wave energy converters (WECs) are still high compared to other technologies. In order to reduce these costs, two principle options are [...] Read more.
Wave energy has a promising technical potential that could contribute to the future energy mix. However, costs related to the deployment of wave energy converters (WECs) are still high compared to other technologies. In order to reduce these costs, two principle options are available, a reduction in cost and an increase in productivity. This paper presents a reliability-based computational tool to identify typical decision problems and to shed light on the complexity of optimising a wave power farm. The proposed tool is used to investigate productivity and availability of a wave energy farm during 10 years of operational life. A number of optimization possibilities to improve productivity, namely vessel choice, maintenance regime, failure rate and component redundancy, are then explored in order to assess their effectiveness. The paper quantifies the yield increase and provides a practical approach to evaluate the effectiveness of strategic and operational decision options. Results, in terms of the variations in productivity and availability of the farm, are analysed and discussed. Conclusions highlight the importance of reliability-centred simulations that consider the specific decision parameters throughout the operational life to find suitable solutions that increase the productivity and reduce the running cost for offshore farms. Full article
(This article belongs to the Special Issue Ocean Wave Energy Conversion)
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4404 KiB  
Article
A Floating Ocean Energy Conversion Device and Numerical Study on Buoy Shape and Performance
by Ruiyin Song, Meiqin Zhang, Xiaohua Qian, Xiancheng Wang, Yong Ming Dai and Junhua Chen
J. Mar. Sci. Eng. 2016, 4(2), 35; https://doi.org/10.3390/jmse4020035 - 10 May 2016
Cited by 12 | Viewed by 6751
Abstract
Wave and current energy can be harnessed in the East China Sea and South China Sea; however, both areas are subject to high frequencies of typhoon events. To improve the safety of the ocean energy conversion device, a Floating Ocean Energy Conversion Device [...] Read more.
Wave and current energy can be harnessed in the East China Sea and South China Sea; however, both areas are subject to high frequencies of typhoon events. To improve the safety of the ocean energy conversion device, a Floating Ocean Energy Conversion Device (FOECD) with a single mooring system is proposed, which can be towed to avoid severe ocean conditions or for regular maintenance. In this paper, the structure of the FOECD is introduced, and it includes a catamaran platform, an oscillating buoy part, a current turbine blade, hydraulic energy storage and an electrical generation part. The numerical study models the large catamaran platform as a single, large buoy, while the four floating buoys were modeled simply as small buoys. Theoretical models on wave energy power capture and efficiency were established. To improve the suitability of the buoy for use in the FOECD and its power harvesting capability, a numerical simulation of the four buoy geometries was undertaken. The shape profiles examined in this paper are cylindrical, turbinate (V-shaped and U-shaped cone with cylinder), and combined cylinder-hemisphere buoys. Simulation results reveal that the suitability of a turbinate buoy is the best of the four types. Further simulation models were carried out by adjusting the tip radius of the turbinate buoy. Three performance criteria including suitability, power harvesting capability and energy capture efficiency were analyzed. It reveals that the turbinate buoy has almost the same power harvesting capabilities and energy capture efficiency, while its suitability is far better than that of a cylindrical buoy. Full article
(This article belongs to the Special Issue Ocean Wave Energy Conversion)
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6377 KiB  
Article
On Peak Mooring Loads and the Influence of Environmental Conditions for Marine Energy Converters
by Violette Harnois, Philipp R. Thies and Lars Johanning
J. Mar. Sci. Eng. 2016, 4(2), 29; https://doi.org/10.3390/jmse4020029 - 08 Apr 2016
Cited by 14 | Viewed by 5979
Abstract
Mooring systems are among the most critical sub-systems for floating marine energy converters (MEC). In particular, the occurrence of peak mooring loads on MEC mooring systems must be carefully evaluated in order to ensure a robust and efficient mooring design. This understanding can [...] Read more.
Mooring systems are among the most critical sub-systems for floating marine energy converters (MEC). In particular, the occurrence of peak mooring loads on MEC mooring systems must be carefully evaluated in order to ensure a robust and efficient mooring design. This understanding can be gained through long-term field test measurement campaigns, providing mooring and environmental data for a wide range of conditions. This paper draws on mooring tensions and environmental conditions that have been recorded (1) for several months during the demonstration of an MEC device and (2) over a period of 18 months at a mooring test facility. Both systems were installed in a shallow water depth (45 m and 30 m, respectively) using compliant multi-leg catenary mooring systems. A methodology has been developed to detect peak mooring loads and to relate them to the associated sea states for further investigation. Results indicate that peak mooring loads did not occur for the sea states on the external contour line of the measured sea states, but for the sea states inside the scatter diagram. This result is attributed to the short-term variability associated with the maximum mooring load for the given sea state parameters. During the identified sea states, MEC devices may not be in survival mode, and thus, the power take-off (PTO) and ancillary systems may be prone to damage. In addition, repeated high peak loads will significantly contribute to mooring line fatigue. Consequently, considering sea states inside the scatter diagram during the MEC mooring design potentially yields a more cost-effective mooring system. As such, the presented methodology contributes to the continuous development of specific MEC mooring systems. Full article
(This article belongs to the Special Issue Ocean Wave Energy Conversion)
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2099 KiB  
Article
Dynamically Scaled Model Experiment of a Mooring Cable
by Lars Bergdahl, Johannes Palm, Claes Eskilsson and Jan Lindahl
J. Mar. Sci. Eng. 2016, 4(1), 5; https://doi.org/10.3390/jmse4010005 - 25 Jan 2016
Cited by 32 | Viewed by 7052
Abstract
The dynamic response of mooring cables for marine structures is scale-dependent, and perfect dynamic similitude between full-scale prototypes and small-scale physical model tests is difficult to achieve. The best possible scaling is here sought by means of a specific set of dimensionless parameters, [...] Read more.
The dynamic response of mooring cables for marine structures is scale-dependent, and perfect dynamic similitude between full-scale prototypes and small-scale physical model tests is difficult to achieve. The best possible scaling is here sought by means of a specific set of dimensionless parameters, and the model accuracy is also evaluated by two alternative sets of dimensionless parameters. A special feature of the presented experiment is that a chain was scaled to have correct propagation celerity for longitudinal elastic waves, thus providing perfect geometrical and dynamic scaling in vacuum, which is unique. The scaling error due to incorrect Reynolds number seemed to be of minor importance. The 33 m experimental chain could then be considered a scaled 76 mm stud chain with the length 1240 m, i.e., at the length scale of 1:37.6. Due to the correct elastic scale, the physical model was able to reproduce the effect of snatch loads giving rise to tensional shock waves propagating along the cable. The results from the experiment were used to validate the newly developed cable-dynamics code, MooDy, which utilises a discontinuous Galerkin FEM formulation. The validation of MooDy proved to be successful for the presented experiments. The experimental data is made available here for validation of other numerical codes by publishing digitised time series of two of the experiments. Full article
(This article belongs to the Special Issue Ocean Wave Energy Conversion)
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