Category Archives: Testing Infrastructure

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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Power converter and control system developed in the Ocean Sentinel instrumentation buoy for testing wave energy converters


Lettenmaier, T., Amon, E., and von Jouanne, A. – 2013 IEEE Energy Conversion Congress and Exposition (ECCE), September 2013

Abstract

The Ocean Sentinel instrumentation buoy was developed for the non-grid-connected testing of wave energy converters (WECs). This surface buoy provides power analysis and data acquisition, environmental monitoring, as well as an active converter interface to control WEC-generated power dissipation in an onboard electrical load. The first deployment of the Ocean Sentinel was in the summer of 2012 for the testing of a half-scale WEC over a six-week period. This paper presents the Ocean Sentinel instrumentation buoy power converter and control system designed to enable the ocean testing of a wide range of WEC technologies with various power outputs and generator configurations.

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Wave prediction and its implementation on control systems of Wave Energy Converters


Peter Kracht, Boris Fischer, Sebastian Perez-Becker, and Jean-Baptiste Richard – MARINET Technical Report, 2013

Abstract

Many advanced control schemes have been proposed for wave energy converters (WEC), which offer the chance of significantly increasing the energy yield. Assessing the available literature so far most of these control schemes have only been investigated by simulations. These simulations are often based on assumptions such as that linear wave theory is applicable, that perfect models for the WEC/PTOs etc. are available or that an ideal prediction of the wave excitation force some distance in the future is available. Continue reading

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Dynamics of a Floating Platform Mounting a Hydrokinetic Turbine


Tobias Dewhurst, M. Robinson Swift, Martin Wosnik, Kenneth Baldwin, Judson DeCew, and Matthew Rowell – Marine Technology Society Journal, August 2013

Abstract

A two-dimensional mathematical model was developed to predict the dynamic response of a moored, floating platform mounting a tidal turbine in current and waves. The model calculates heave, pitch, and surge response to collinear waves and current. Waves may be single frequency or a random sea with a specified spectrum. The mooring consists of a fixed anchor, heavy chain (forming a catenary), a lightweight elastic line, and a mooring ball tethered to the platform. The equations of motion and mooring equations are solved using a marching solution approach implemented using MATLAB. The model was applied to a 10.7-m twin-hulled platform used to deploy a 0.86-m shrouded, in-line horizontal axis turbine. Added mass and damping coefficients were obtained empirically using a 1/9 scale physical model in tank experiments. Full-scale tests were used to specify drag coefficients for the turbine and platform. The computer model was then used to calculate full-scale mooring loads, turbine forces, and platform motion in preparation for a full-scale test of the tidal turbine in Muskeget Channel, Massachusetts, which runs north-south between Martha’s Vineyard and Nantucket Island. During the field experiments, wave, current, and platform motion were recorded. The field measurements were used to compute response amplitude operators (RAOs), essentially normalized amplitudes or frequency responses for heave, pitch, and surge. The measured RAOs were compared with those calculated using the model. The very good agreement indicates that the model can serve as a useful design tool for larger test and commercial platforms.

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Testing the WET-NZ Wave Energy Converter Using the Ocean Sentinel Instrumentation Buoy


Terry Lettenmaier, Annette von Jouanne, Ean Amon, Sean Moran, Alister Gardiner – Marine Technology Society Journal, August 2013

Abstract

This paper describes ocean testing of the half-scale Wave Energy Technology-New Zealand (WET-NZ) prototype wave energy converter (WEC) using the Ocean Sentinel instrumentation buoy during a 6-week deployment period in August-October 2012. These tests were conducted by the Northwest National Marine Renewable Energy Center (NNMREC) at its Pacific Ocean test site off the coast of Newport, Oregon. The WET-NZ is the product of a research consortium between Callaghan Innovation, a New Zealand Crown Entity, and Power Projects Limited (PPL), a Wellington, New Zealand private company. The Oregon deployment was project managed by Northwest Energy Innovations (NWEI), a Portland, OR firm. NNMREC is a Department of Energy sponsored partnership between Oregon State University (OSU), the University of Washington (UW), and the National Renewable Energy Laboratory (NREL). The Ocean Sentinel instrumentation buoy is a 6-m surface buoy, developed in 2012, that provides a stand-alone electrical load, WEC generator control, and data collection for WECs being tested. The Ocean Sentinel was deployed and operated for the first time during the 2012 WET-NZ tests. During these tests, the operation of the WET-NZ was demonstrated and its performance was characterized, while also proving successful deployment and operation of the Ocean Sentinel.

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Experimental Evaluation of a Mixer-Ejector Marine Hydrokinetic Turbine at Two Open-Water Tidal Energy Test Sites in NH and MA


Matthew Rowell, Martin Wosnik, Jason Barnes, and Jeffrey P. King – Marine Technology Society Journal, August 2013

Abstract

For marine hydrokinetic energy to become viable, it is essential to develop energy conversion devices that are able to extract energy with high efficiency from a wide range of flow conditions and to field test them in an environment similar to the one they are designed to eventually operate in. FloDesign Inc. developed and built a mixer-ejector hydrokinetic turbine (MEHT) that encloses the turbine in a specially designed shroud that promotes wake mixing to enable increased mass flow through the turbine rotor. A scaled version of this turbine was evaluated experimentally, deployed below a purpose-built floating test platform at two open-water tidal energy test sites in New Hampshire and Massachusetts and also in a large cross-section tow tank. State-of-the-art instrumentation was used to measure the tidal energy resource and turbine wake flow velocities, turbine power extraction, test platform loadings, and platform motion induced by sea state. The MEHT was able to generate power from tidal currents over a wide range of conditions, with low-velocity start-up. The mean velocity deficit in the wake downstream of the turbine was found to recover more quickly with increasing levels of free stream turbulence, which has implications for turbine spacing in arrays.

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Numerical Modeling to Aid in the Structural Health Monitoring of Wave Energy Converters


William Finnegan and Jamie Goggins – Key Engineering Materials, July 2013

Abstract

A vital aspect of ensuring the cost effectiveness of wave energy converters (WECs) is being able to monitor their performance remotely through structural health monitoring, as these devices are deployed in very harsh environments in terms of both accessibility and potential damage to the devices. The WECs are monitored through the use of measuring equipment, which is strategically placed on the device. This measured data is then compared to the output from a numerical model of the WEC under the same ocean wave conditions. Any deviations would suggest that there are problems or issues with the WEC. The development of accurate and effective numerical models is necessary to minimise the number of times the visual, or physical, inspection of a deployed WEC is required. In this paper, a numerical wave tank model is, first, validated by comparing the waves generated to those generated experimentally using the wave flume located at the National University of Ireland, Galway. This model is then extended so it is suitable for generating real ocean waves. A wave record observed at the Atlantic marine energy test site has been replicated in the model to a high level of accuracy. A rectangular floating prism is then introduced into the model in order to explore wave-structure interaction. The dynamic response of the structure is compared to a simple analytical solution and found to be in good agreement.

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A wave energy resource assessment case study: Review, analysis and lessons learnt


Helen C.M. Smith, David Haverson, and George H. Smith – Renewable Energy, December 2013

Abstract

A case study of the development of an overall resource assessment for the Wave Hub site in the southwest UK is presented. Wave Hub is one of the earliest large-scale wave farms planned. Several resource assessment studies have been performed for the site, but the published results are high-level and predicted power availability varies significantly. This paper provides a detailed overview and re-analysis of the multiple datasets used in the original studies, which consisted of a combination of physical measurement and numerical modelling. The quality of the datasets is assessed, and reasons for the discrepancies between predicted resource levels investigated. Results from a SWAN model for the region illustrate significant levels of spatial variability in the resource due to the complexity of the local bathymetry, and examination of long-term global model datasets shows notable inter-annual variability. It is thus concluded that a resource assessment methodology utilising datasets from multiple locations and of short duration significantly reduces the accuracy of the predicted levels of resource. From these results, key learnings for future developments are discussed.

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Experimental investigation in a Wells turbine under bi-directional flow


M. Paderi and P. Puddu – Renewable Energy, September, 2013

Abstract

In this work an experimental study of flow through a Wells turbine with NACA0015 profiles submitted to an unsteady and bi-directional flow is presented.

The experimental set-up of the Department of Mechanical, Chemical and Materials Engineering of the University of Cagliari (DIMCM), can simulate the real operation of a wave energy conversion device based on the principle of an oscillating water column (OWC) equipped with a Wells turbine. The set-up consists of a piston, controlled by a hydraulic system, that moves inside a cylindrical chamber open at the top where the Wells turbine is placed. The piston movement generates the airflow driving the turbine.

Experimental investigations were carried out in proximity of the rotor blade using three-dimensional aerodynamic probes to perform a careful characterization of the flow field upstream and downstream of the turbine. The dynamic characteristic of the turbine in terms of dimensionless flow parameters was also determined. The real entity of the hysteresis phenomenon was highlighted for the phases of acceleration and deceleration of the unsteady flow through the turbine. Moreover, the existence of an appropriate correlation between the conventional dimensionless coefficients and a measurable and reliable physical variable was investigated.

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A Novel Ocean Sentinel Instrumentation Buoy for Wave Energy Testing


A. von Jouanne, T. Lettenmaier, E. Amon, T. Brekken, R. Phillips – Marine Technology Society Journal, February 2013

Abstract

This paper presents a novel Ocean Sentinel instrumentation buoy that the Northwest National Marine Renewable Energy Center (NNMREC) has developed with AXYS Technologies for the testing of wave energy converters (WECs). NNMREC is a Department of Energy-sponsored partnership among Oregon State University (OSU), the University of Washington (UW), and the National Renewable Energy Laboratory (NREL). The Ocean Sentinel instrumentation buoy is a surface buoy based on the 6-m NOMAD (Navy Oceanographic Meteorological Automatic Device) design. The Ocean Sentinel provides power analysis, data acquisition, and environmental monitoring, as well as an active converter interface to control power dissipation to an onboard electrical load. The WEC being tested and the instrumentation buoy are moored with approximately 125 meters separation; connected by a power and communication umbilical cable. The Ocean Sentinel was completed in 2012 and was deployed for the testing of a WEC at the NNMREC open-ocean test site, north of Newport, OR, during August and September of 2012.

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