Monthly Archives: August 2012

Submerged Transmission in Wave Energy Converters: Full Scale In-Situ Experimental Measurements


E Strömstedt – Uppsala University Doctoral Thesis, August 2012

Abstract
Different wave power technologies are in development around the world in different stages of prototype testing. So far only a few devices have been deployed offshore at full scale for extended periods of time. Little data is published about how these different devices perform.This thesis presents results from experiments with the full-scale offshore wave energy converters at the Lysekil research site on the Swedish west coast. The theories, experiments, measurements, performance evaluations and developments of the submerged transmission in the direct driven permanent magnet linear generator are in focus. The reciprocating submerged transmission fulfills the purpose of transmitting the absorbed mechanical wave energy through the capsule wall into the generator, while preventing the seawater from entering the capsule and reducing the life time of the converter. Continue reading

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The dynamics of an energetic tidal channel, the Pentland Firth, Scotland


MC Easton, DK Woolf, PA Bowyer – Continental Shelf Research, August 2012

Abstract

Shelf tidal stream velocities are accelerated by nearshore geographic features, such as headlands and islands. In the search for sustainable forms of electrical energy generation, such locations may become attractive for tidal stream power developments. For some prospective tidal stream energy sites, however, little is known about the intricacies of the local tidal dynamics: knowledge which is crucial to the understanding of the resource and the potential environmental consequences of its extraction.

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Experimental wave termination in a 2D wave tunnel using a cycloidal wave energy converter


SG Siegel, C Fagley, S Nowlin – Applied Ocean Research, October 2012

Abstract

A lift based cycloidal wave energy converter (CycWEC) is investigated in a 1:300 scale two-dimensional wave flume experiment. This type of wave energy converter consists of a shaft with one or more hydrofoils attached eccentrically at a radius. The main shaft is aligned parallel to the wave crests and submerged at a fixed depth. The operation of the CycWEC both as a wave generator as well as a wave-to-shaft energy converter interacting with straight crested waves is demonstrated. The geometry of the converter is shown to be suitable for wave termination of straight crested harmonic and irregular waves. The impact of design parameters such as device size, submergence depth, and number of hydrofoils on the performance of the converter is shown. For optimal parameter choices, experimental results demonstrate energy extraction efficiencies of more than 95% of the incoming wave energy. This is achieved using feedback control to synchronize the rotation of the CycWEC to the incoming wave, and adjusting the blade pitch angle in proportion to the wave height. Due to the ability of the CycWEC to generate a single sided wave with few harmonic waves, little energy is lost to waves radiating in the up-wave and down-wave directions.

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THOR’s Power Method for Hydrokinetic Devices


J.T. Hunt and J. Rumker – Technical Report submitted to DOE EERE Wind & Water Power Program, August, 2012

Abstract
Ocean current energy represents a vast untapped source of renewable energy that exists on the outer continental shelf areas of the 5 major continents. Ocean currents are unidirectional in nature and are perpetuated by thermal and salintiy sea gradients, as well as coriolis forces imparted from the earth’s rotation. This report details THORs Power Method, a breakthrough power control method that can provide dramatic increases to the capacity factor over and above existing marine hydrokinetic (MHK) devices employed in the extraction of energy from ocean currents. THORs Power Method represents a constant speed, variable depth operational method that continually locates the ocean current turbine at a depth at which the rated power of the generator is routinely achieved. Variable depth operation is achieved by using various vertical force effectors, including ballast tanks for variable weight, a hydrodynamic wing for variable lift or down force and drag flaps for variable vehicle drag forces.

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Silicone foul release coatings show promise to manage invasive mussels at water facilities


(Bureau of Reclamation) Reclamation has found that silicone foul release coatings may be an important tool for mitigating invasive quagga and zebra mussels’ impacts to water and hydropower infrastructure. Allen D. Skaja, Ph.D., PCS, of Reclamation’s Technical Service Center tested more than 50 coatings and metal alloys over three years at Parker Dam on the Colorado River.

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UA engineering professor uses aerospace materials to build endless pipeline


(University of Arizona College of Engineering) Carbon fiber fabric and lightweight honeycomb materials, plus a mobile manufacturing platform, make infinite pipeline technology cheaper and greener while boosting local economies
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Numerical Wave Modeling and Wave Energy Estimation


G Galanis, G Zodiatis, D Hayes, A Nikolaidis, G Georgiou, S Stylianou, G Kallos, C Kalogeri, PC Chu and A Charalambous – Advances in Meteorology, 2013

Abstract
In a rapidly evolving operational and research framework concerning the global energy resources, new frontiers have been set for the scientific community working on environmental and renewable energy issues. In particular, new numerical techniques supporting the accurate estimation of renewable energy sources are highly emphasized. In this framework, wave energy – the energy that can be captured from sea waves – provides an alternative option with critical advantages. In the present paper, recent advances and some preliminary results obtained in two European projects will be discussed: Marina Platform and E-wave projects are focusing on the estimation of the wave energy potential in North Atlantic coastline of Europe and in Eastern Mediterranean Sea, respectively. Special emphasis is given to the utilization of numerical atmospheric and wave modeling systems able to accurately monitor the atmospheric and sea conditions in the area of interest. On the other hand, advanced statistical techniques are utilized for the local adaptation of the results and the estimation of the spatial and temporal distribution of the wave energy potential.

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Morphological Response Of High-Energy Macrotidal Beaches


TG Poate – Doctoral Dissertation, University of Plymouth, 2012

Abstract
Spatial data collected over 3 years is presented to assess the extent of morphological variability under seasonal and storm waves at four high-energy macrotidal beaches. A novel approach is adopted to identify and classify the beach response which is used to assess the relative stability of the system to changes in the dominant forcing conditions. Field measurements and modelling simulations using XBeach provide further support for a storm dominated system exhibiting relative stability. Morphologically the beaches range from dissipative to intermediate and are characterised by low tide bar/rip morphology which plays a key role in the nearshore dynamics and beach safety. Located in the north coast of Cornwall the sites are exposed to high-energy waves that dominate the stability and behaviour of beaches in this region. The growing need for marine renewable energy in the UK has led to the deployment of a Wave Hub on the seabed off the north coast of Cornwall, designed to provide grid connection for wave energy devices (WECs). As a unique development much has been done to address concerns over potential impacts cause by arrays of WECs during its construction and operational lifetime; these predicted impacts include changes in the quality of waves for surfing and effects on the beach dynamics which determines beach safety through the presence of bar/rip features. Continue reading

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The extractable power from a split tidal channel: An equivalent circuit analysis


PF Cummins –Renewable Energy, August 2012

Abstract

Considerable interest exists in the possibility of exploiting strong tidal currents as a source of renewable energy. Methods to understand and evaluate this resource have been developed for simple flow configurations, such as a tidal channel linking the open ocean to an inner basin. More complicated flow geometries involving branching channels have been considered recently. A simple prototype for this class of problem consists a tidal channel that is split by an island into two sub-channels. In-stream energy conversion devices are deployed in one of the sub-channels, while the second is left free for navigation or other purposes. The free sub-channel allows flow to be diverted away from the impeded sub-channel, which may lead to a reduction in the available power.

In the present paper, an electric circuit analogue is used to develop a linear theory for the power potential of a split tidal channel. Although limited to linear friction, this approach allows for inclusion of the effects of flow acceleration and finite basin size that have not been considered previously. Based on the equivalent circuit, analytical expressions are derived for the maximum extractable power and for the modification of the flow in each section of the channel at maximum power. Extension of the theory to multiple branching channels is discussed. Results for a few simple cases are considered.

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Coated High Strength Fibers (Patent)


R Bosman, G Aben, H Schneiders – US Patent 20,120,198,808, August 2012

Abstract
The invention relates to a high strength fibers comprising a coating of cross-linked silicone polymer, and ropes made thereof. The fibers are preferably high performance polyethylene (HPPE) fibers. The coating comprising a cross-linked silicone polymer is made from a coating composition comprising a cross-linkable silicone polymer. The rope shows markedly improved service life performance in bending applications such as cyclic bend-over-sheave applications. The invention also relates to the use of a cross-linked silicone polymer in a rope for an improvement of bend fatigue resistance.

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