Author Archives: bpolagye

Reliability-Based Structural Optimization of Wave Energy Converters


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Simon Ambühl, Morten Kramer and John Dalsgaard Sørensen – Energies, December 2014

Abstract

More and more wave energy converter (WEC) concepts are reaching prototype level. Once the prototype level is reached, the next step in order to further decrease the levelized cost of energy (LCOE) is optimizing the overall system with a focus on structural and maintenance (inspection) costs, as well as on the harvested power from the waves.  Continue reading

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An Intelligent Fuzzy Logic Controller for Maximum Power Capture of Point Absorbers


Mohammed Jama, Addy Wahyudie, Ali Assi, and Hassan Noura – Energies, June 2014

Abstract

This article presents an intelligent fuzzy logic controller (FLC) for controlling single-body heaving wave energy converter (WEC) or what is widely known as “Point Absorber”. The controller aims at maximizing the energy captured from the sea waves. The power take-off (PTO) limitations are addressed implicitly in the fuzzy inference system (FIS) framework. Continue reading

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Evaluation of the Wave Energy Conversion Efficiency in Various Coastal Environments


Eugen Rusu – Energies, June 2014

Abstract

The main objective of the present work was to assess and compare the wave power resources in various offshore and nearshore areas. From this perspective, three different groups of coastal environments were considered: the western Iberian nearshore, islands and an enclosed environment with sea waves, respectively. Some of the most representative existent wave converters were evaluated in the analysis and a second objective was to compare their performances at the considered locations, and in this way to determine which is better suited for potential commercial exploitation. Continue reading

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Sea Trials of a Wave Energy Converter in Strangford Lough, Northern Ireland


Vladimir Krivtsov, Ian Bryden, Brian Linfoot, and Robin Wallace – Journal of Shipping and Ocean Engineering, 2013

Abstract

This paper describes a campaign of WEC (wave energy converter) testing and presents a selection of the results related to the measured motions and mooring tensions. A 1:20 physical model has been successfully deployed using a three point mooring installed at sea (Strangford Lough, NI) in 10 m depth. Continue reading

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Filed under Experiments, Modeling, Testing Infrastructure

Multistable chain for ocean wave vibration energy harvesting


R. L. Harne, M. E. Schoemaker, and K. W. Wang – Proc. SPIE Active and Passive Smart Structures and Integrated Systems, March 2014

Abstract

The heaving of ocean waves is a largely untapped, renewable kinetic energy resource. Conversion of this energy into electrical power could integrate with solar technologies to provide for round-the-clock, portable, and mobile energy supplies usable in a wide variety of marine environments. However, the direct drive conversion methodology of grid integrated wave energy converters does not efficiently scale down to smaller, portable architectures. This research develops an alternative power conversion approach to harness the extraordinarily large heaving displacements and long oscillation periods as an excitation source for an extendible vibration energy harvesting chain. Building upon related research findings and engineering insights, the proposed system joins together a series of dynamic cells through bistable interfaces. Continue reading

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Filed under Experiments, Modeling, System Development

In-tank tests of a dielectric elastomer generator for wave energy harvesting


R. Vertechy, M. Fontana, G. P. Rosati Papini, and D. Forehand – Proc. SPIE Electroactive Polymer Actuators and Devices (EAPAD), March 2014

Abstract

Wave energy harvesting is one of the most promising applications for Dielectric Elastomer Generators. A simple and interesting concept of a Wave Energy Converter based on Dielectric Elastomers is the Polymeric Oscillating Water Column (Poly-OWC). In this paper, preliminary experimental results on the assessment of a small-scale Poly-OWC prototype are presented. The scale of the considered prototype is 1:50. Tests are conducted in a wave-flume by considering sea state conditions with different wave amplitudes and frequencies. The obtained experimental results confirm the viability of the Poly-OWC device.

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Filed under Component Development, Materials and coatings

The role of tidal asymmetry in characterizing the tidal energy resource of Orkney


Simon P. Neill, M. Reza Hashemi, and Matt J. Lewis – Renewable Energy, August 2014

Abstract

When selecting sites for marine renewable energy projects, there are a wide range of economical and practical constraints to be considered, from the magnitude of the resource through to proximity of grid connections. One factor that is not routinely considered in tidal energy site selection, yet which has an important role in quantifying the resource, is tidal asymmetry, i.e. variations between the flood and ebb phases of the tidal cycle. Here, we present theory and develop a high-resolution three-dimensional ROMS tidal model of Orkney to examine net power output for a range of sites along an energetic channel with varying degrees of tidal asymmetry. Since power output is related to velocity cubed, even small asymmetries in velocity lead to substantial asymmetries in power output. We also use the 3D model to assess how tidal asymmetry changes with height above the bed, i.e. representing different device hub heights, how asymmetry affects turbulence properties, and how asymmetry is influenced by wind-driven currents. Finally, although there is minimal potential for tidal phasing over our study site, we demonstrate that regions of opposing flood- versus ebb-dominant asymmetry occurring over short spatial scales can be aggregated to provide balanced power generation over the tidal cycle.

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Filed under Modeling, Resource Characterization

Flow–structure–seabed interactions in coastal and marine environments


B. Mutlu Sumer – Journal of Hydraulic Research,  March 2013

Abstract

Flow–structure–seabed interaction in coastal and marine environments is a rapidly growing area of research and applications. In this vision paper, this area is discussed with a view of identifying its state of the art and current research challenges. The discussion draws attention to key issues related to structures such as marine pipelines, offshore windfarms, and multiuse offshore platforms. Tsunamis, which received considerable attention after two recent extreme events (2004 Indonesia tsunami and 2011 Japan tsunami) are also included in the discussion. Marine hydro-geomechanics is highlighted, among other areas, as an emerging branch of Marine Civil Engineering. Predictions of the field development for the forthcoming years are also briefly outlined.

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Filed under other Cross cutting, Review

A review on flow energy harvesters based on flapping foils


Qing Xiao and Qiang Zhu – Journal of Fluids and Structures, April 2014

Abstract

This article presents an overview of the state of the art investigations on the recently developed oscillating foil energy converters. A summary of available knowledge and up-to-date progress in the application of such bio-inspired systems for renewable energy devices is provided. Starting from concepts and achieved results in three distinguishable categories, various parametric studies are reviewed, along with an in-depth discussion on the potential device performance enhancement via flow control mechanisms. Finally, potential future research directions are discussed.

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Grid Connected Three-Level Converters


Remya Krishna – Uppsala University, Doctoral Dissertation, March 2014

Abstract

This thesis presents an electrical system analysis of a wave energy converter (WEC) for the objective of grid connection. To transfer the enormous amount of power from waves to the load centers, efficient power electronic systems are essential. This thesis includes the modeling of a buoy–translator dynamics and the modeling of a linear permanent magnet generator along with simulation and experimental validation. Continue reading

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