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Atan R.,National University of Ireland | Atan R.,Marine Renewable Energy Ireland search Center | Atan R.,Marine Institute of Ireland | Goggins J.,National University of Ireland | And 9 more authors.
Ocean Engineering | Year: 2016

This research presents an assessment of wave characteristics at the 1/4 scale wave energy test site in Galway Bay based on (1) data from a waverider buoy from 2009 to 2013 and (2) data from a high frequency radar system (CODAR) from 2011 to 2013. The main objective of this research is to provide an assessment of annual and seasonal wave characteristics and resource variability at a wave energy site. Such assessments are extremely important for wave energy test sites so as to inform the design, optimisation and maintenance of wave energy converters. An approach for classifying operational, high and extreme wave events is presented. The approach is based on percentage of occurrences of particular wave events and can be applied to any site and any wave parameter. In the present research it is separately applied to wave height and wave power. An additional objective is the validation of CODAR wave data for use in assessment of wave height characteristics; this was achieved by comparing CODAR data with waverider data. The research shows that the authors characterisation methodology is easy to apply and unambiguous to interpret. Due to the significant variation in wave parameters at the site from season to season and year to year, operational, high and extreme conditions are presented for the 5-year measurement period, individual years and individual seasons. The research also shows that wave heights determined from CODAR show good agreement with those from a waverider buoy and may be relied upon for accurate site characterisation. © 2016 Elsevier Ltd. All rights reserved. Source

Atan R.,National University of Ireland | Goggins J.,National University of Ireland | Hartnett M.,National University of Ireland | Nash S.,National University of Ireland | Agostinho P.,Qualitas Remos
Renewable Energies Offshore - 1st International Conference on Renewable Energies Offshore, RENEW 2014 | Year: 2015

The Galway bay 1/4-scale wave energy test site on the West coast of Ireland is selected as a study area for the assessment of extreme wave events presented in this paper. A preliminary data analysis includes two datasets: (1) high frequency radar measurements from the Galway Bay CODAR system, and (2) the Galway Bay wave buoy. A comparison between CODAR and wave buoy data for the period from October to December 2103 shows a good level of agreement between the datasets with a root mean square error of 0.34 for significant wave height (Hs), thus validating the accuracy of CODAR data for use in extreme wave assessments. The main objective of the paper is an assessment of extreme wave conditions based on 3 months of CODAR data. Monthly mean values for Hs are presented as monthly wave occurrences and quintiles plot analyses. © 2015 Taylor & Francis Group, London. Source

Abascal A.J.,University of Cantabria | Castanedo S.,University of Cantabria | Fernandez V.,Qualitas Remos | Medina R.,University of Cantabria
Ocean Dynamics | Year: 2012

In this work, the benefits of high-frequency (HF) radar ocean observation technology for backtracking drifting objects are analysed. The HF radar performance is evaluated by comparison of trajectories between drifter buoys versus numerical simulations using a Lagrangian trajectory model. High-resolution currents measured by a coastal HF radar network combined with atmospheric fields provided by numerical models are used to backtrack the trajectory of two dataset of surface-drifting buoys: group I (with drogue) and group II (without drogue). A methodology based on optimization methods is applied to estimate the uncertainty in the trajectory simulations and to optimize the search area of the backtracked positions. The results show that, to backtrack the trajectory of the buoys in group II, both currents and wind fields were required. However, wind fields could be practically discarded when simulating the trajectories of group I. In this case, the optimal backtracked trajectories were obtained using only HF radar currents as forcing. Based on the radar availability data, two periods ranging between 8 and 10 h were selected to backtrack the buoy trajectories. The root mean squared error (RMSE) was found to be 1.01 km for group I and 0.82 km for group II. Taking into account these values, a search area was calculated using circles of RMSE radii, obtaining 3.2 and 2.11 km 2 for groups I and II, respectively. These results show the positive contribution of HF radar currents for backtracking drifting objects and demonstrate that these data combined with atmospheric models are of value to perform backtracking analysis of drifting objects. © Springer-Verlag 2012. Source

Whelan C.W.,Codar Ocean Sensors, Ltd. | Barrick D.E.,Codar Ocean Sensors, Ltd. | Lilleboe P.M.,Codar Ocean Sensors, Ltd. | Kjelaas A.,CodarNor A S | And 3 more authors.
OCEANS'10 IEEE Sydney, OCEANSSYD 2010 | Year: 2010

The Norwegian company CodarNor A/S, with funding from the Norwegian Clean Seas Association for Operating Companies (NOFO) and from Innovation Norway through an industrial research and development contract, is developing a self-contained rapid deployment HF radar which can be deployed by helicopter or other means to remote and rugged locations along the Norwegian coast and operate autonomously, communicating surface current data in real time back to operators, the Norwegian Coastal Administration and drift modelers. Large-scale 2-D current maps collected from these rapid-deployable systems will be used to improve spill response efforts by blending data with drift model currents for improved drift predictions and cleanup vessel management. © 2010 IEEE. Source

Barrick D.,Codar Ocean Sensors, Ltd. | Fernandez V.,Qualitas Remos | Ferrer M.I.,Qualitas Remos | Whelan C.,Codar Ocean Sensors, Ltd. | And 2 more authors.
Ocean Dynamics | Year: 2012

In order to address the need for surface trajectory forecasts following deployment of coastal HF radar systems during emergency-response situations (e.g., search and rescue, oil spill), a short-term predictive system (STPS) based on only a few hours data background is presented. First, open-modal analysis (OMA) coefficients are fitted to 1-D surface currents from all available radar stations at each time interval. OMA has the effect of applying a spatial low-pass filter to the data, fills gaps, and can extend coverage to areas where radial vectors are available from a single radar only. Then, a set of temporal modes is fitted to the time series of OMA coefficients, typically over a short 12-h trailing period. These modes include tidal and inertial harmonics, as well as constant and linear trends. This temporal model is the STPS basis for producing up to a 12-h current vector forecast from which a trajectory forecast can be derived. We show results of this method applied to data gathered during the September 2010 rapid-response demonstration in northern Norway. Forecasted coefficients, currents, and trajectories are compared with the same measured quantities, and statistics of skill are assessed employing 16 24-h data sets. Forecasted and measured kinetic variances of the OMA coefficients typically agreed to within 10-15%. In one case where errors were larger, strong wind changes are suspected and examined as the cause. Sudden wind variability is not included properly within the STPS attack we presently employ and will be a subject for future improvement. © 2011 Springer Science+Business Media, LLC. Source

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