Welcome to MHKTechPapers


Welcome to MHK Tech Papers Blog.  The purpose of this blog is to aggregate and organize technical papers as they relate the the development of Marine and Hydrokinetic (MHK) technologies. This blog is a community effort, begun by Mike Spray, and focuses on technology development, economics and resource assessment. Those with interests in social science, environmental impacts, and policy dimensions of MHK technologies may find alternative compendiums helpful, such as the TETHYS database. This blog acts as a virtual journal for MHK, a necessary function, since MHK papers are scattered across a broad set of archival journals. In addition to archival literature, this blog contains relevant technical reports and theses/dissertations. All are tagged as such to distinguish between types of literature.

This blog is maintained by MHK researchers on a rotating, volunteer basis. To recommend a paper for inclusion, gain access, volunteer to take a turn maintaining things, or obtain further information, please contact the current maintainer (Brian Polagye: bpolagye@gmail.com)

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Wave power absorption: Experiments in open sea and simulation


M. Eriksson, R. Waters, O.Svensson, J. Isberg, and M. Leijon- Journal of Applied Physics, 2007

Abstract

A full scale prototype of a wave power plant based on a direct drive linear generator driven by a point absorber has been installed at the west coast of Sweden. In this paper, experimentally collected data of energy absorption for different electrical loads are used to verify a model of the wave power plant including the interactions of wave, buoy, generator, and external load circuit. The wave-buoy interaction is modeled with linear potential wavetheory. The generator is modeled as a nonlinear mechanical damping function that is dependent on piston velocity and electric load. The results show good agreement between experiments and simulations. Potential wavetheory is well suited for the modeling of a point absorber in normal operation and for the design of future converters. Moreover, the simulations are fast, which opens up for simulations of wave farms.

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Filed under Experiments, Field Measurements, Modeling

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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Filed under Grid

Investigation of Wave-Structure Interaction Using State of the Art CFD Techniques


Jan Westphalen, Deborah M. Greaves, Alison Raby, Zheng Zheng Hu, Derek M. Causon, Clive G. Mingham, Pourya Omidvar, Peter K. Stansby, and Benedict D. Rogers – Open Journal of Fluid Dynamics, March 2014

Abstract

The suitability of computational fluid dynamics (CFD) for marine renewable energy research and development and in particular for simulating extreme wave interaction with a wave energy converter (WEC) is considered. Fully nonlinear time domain CFD is often considered to be an expensive and computationally intensive option for marine hydrodynamics and frequency-based methods are traditionally preferred by the industry. However, CFD models capture more of the physics of wave-structure interaction, and whereas traditional frequency domain approaches are restricted to linear motions, fully nonlinear CFD can simulate wave breaking and overtopping. Continue reading

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Filed under Modeling

Experimental Study of Darrieus-Savonius Water Turbine with Deflector: Effect of Deflector on the Performance


Kaprawi Sahim, Kadafi Ihtisan, Dyos Santoso, and Riman Sipahutar – International Journal of Rotating Machinery, February 2014

Abstract

The reverse force on the returning blade of a water turbine can be reduced by setting a deflector on the returning blade side of a rotor. The deflector configuration can also concentrate the flow which passes through the rotor so that the torque and the power of turbine can be considerably increased. The placing of Savonius in Darrieus rotor is carried out by setting the Savonius bucket in Darrieus rotor at the same axis. The combination of these rotors is also called a Darrieus-Savonius turbine. This rotor can improve torque of turbine. Experiments are conducted in an irrigation canal to find the performance characteristics of presence of deflector and Savonius rotor in Darrieus-Savonius turbine. Results conclude that the single deflector plate placed on returning blade side increases the torque and power coefficient. The presence of Savonius rotor increases the torque at a lower speed, but the power coefficient decreases. The torque and power coefficient characteristics depend on the aspect ratio of Savonius rotor.

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Filed under Component Development, Experiments