Wind-induced drift of objects at sea: the leeway field method

A method for conducting leeway field experiments to establish the drift properties of small objects (0.1-25 m) is described. The objective is to define a standardized and unambiguous procedure for condensing the drift properties down to a set of coefficients that may be incorporated into existing stochastic trajectory forecast models for drifting objects of concern to search and rescue operations and other activities involving vessels lost at sea such as containers with hazardous material. An operational definition of the slip or wind and wave-induced motion of a drifting object relative to the ambient current is proposed. This definition taken together with a strict adherence to 10 m wind speed allows us to refer unambiguously to the leeway of a drifting object. We recommend that all objects if possible be studied using what we term the direct method, where the object's leeway is studied directly using an attached current meter. We divide drifting objects into four categories, depending on their size. For the smaller objects (less than 0.5 m), an indirect method of measuring the object's motion relative to the ambient current must be used. For larger objects, direct measurement of the motion through the near-surface water masses is strongly recommended. Larger objects are categorized according to the ability to attach current meters and wind monitoring systems to them. The leeway field method proposed here is illustrated with results from field work where three objects were studied in their distress configuration; a 1:3.3 sized model of a 40-ft Shipping container, a World War II mine and a 220 l (55-gallon) oil drum.Comment: 33 pages, 12 figures, 3 table

Best practice report - installation procedures

Deliverable 3.6.2 from the MERiFIC Project A report prepared as part of the MERiFIC Project "Marine Energy in Far Peripheral and Island Communities"This report is a deliverable of MERiFIC Task 3. 6: ‘Installation Procedures’ and has been produced in a cross border collaboration between IFREMER and the University of Exeter. In this report different elements are presented for the planning and organisation of installation operations for the deployment of Marine energy plants. The optimization of installation procedures are discussed and brought in a context to potential costs optimization and the availability of suitable vessels is considered. Installation procedures, which were also investigated, should include pre-installation surveys so as to optimize the design of moorings and secure laying of the power cable, a specific feature of the commissioning of such Marine energy plants. Attention should also be given to the Health and Safety procedures. Finally, the influence of the weather conditions on the success of these installation operations was discussed and studied. Especially, "Access time" and "Waiting time" weather windows were assessed for different sites in both areas of south west Cornwall and the Iroise Sea, pointing out the importance of the seasonal variability of the wave climate for the planning of installation operations.MERiFIC was selected under the European Cross-Border Cooperation Programme INTERREG IV A France (Channel) – England, co-funded by the ERDF

Best practice report – operation and maintenance requirements

Deliverable 3.6.3 from the MERiFIC Project A report prepared as part of the MERiFIC Project "Marine Energy in Far Peripheral and Island Communities"This report is a deliverable of MERiFIC Work Package 3.6: ‘Operation and Maintenance requirements’ and has been produced as a cross border collaboration between IFREMER and the University of Exeter. The report provides an overview of guidelines and recommendations for the management of O&M operations necessary for an optimal exploitation of Marine energy plants, with a focus on the specific areas of South West Cornwall, UK and Iroise sea, Brittany, France. An overview of the onshore infrastructures and ports possibly suitable for management of such O&M operations is also provided. Management of scheduled and unscheduled maintenance operations are discussed in their various aspects including site accessibility. It should be noted that this topic, including weather window assessment for operations is discussed in more details in the additional MERIFIC report D3.6.2: Best Practice for installation proceduresMERiFIC was selected under the European Cross-Border Cooperation Programme INTERREG IV A France (Channel) – England, co-funded by the ERDF

The Leeway of Shipping Containers at Different Immersion Levels

The leeway of 20-foot containers in typical distress conditions is established through field experiments in a Norwegian fjord and in open-ocean conditions off the coast of France with wind speed ranging from calm to 14 m/s. The experimental setup is described in detail and certain recommendations given for experiments on objects of this size. The results are compared with the leeway of a scaled-down container before the full set of measured leeway characteristics are compared with a semi-analytical model of immersed containers. Our results are broadly consistent with the semi-analytical model, but the model is found to be sensitive to choice of drag coefficient and makes no estimate of the cross-wind leeway of containers. We extend the results from the semi-analytical immersion model by extrapolating the observed leeway divergence and estimates of the experimental uncertainty to various realistic immersion levels. The sensitivity of these leeway estimates at different immersion levels are tested using a stochastic trajectory model. Search areas are found to be sensitive to the exact immersion levels, the choice of drag coefficient and somewhat less sensitive to the inclusion of leeway divergence. We further compare the search areas thus found with a range of trajectories estimated using the semi-analytical model with only perturbations to the immersion level. We find that the search areas calculated without estimates of crosswind leeway and its uncertainty will grossly underestimate the rate of expansion of the search areas. We recommend that stochastic trajectory models of container drift should account for these uncertainties by generating search areas for different immersion levels and with the uncertainties in crosswind and downwind leeway reported from our field experiments.Comment: 25 pages, 11 figures and 5 tables; Ocean Dynamics, Special Issue on Advances in Search and Rescue at Sea (2012

Intercomparison of Three Open-Source Numerical Flumes for the Surface Dynamics of Steep Focused Wave Groups

NewWave-type focused wave groups are commonly used to simulate the design wave for a given sea state. These extreme wave events are challenging to reproduce numerically by the various Numerical Wave Tanks (NWTs), due to the high steepness of the wave group and the occurring wave-wave interactions. For such complex problems, the validation of NWTs against experimental results is vital for confirming the applicability of the models. Intercomparisons among different solvers are also important for selecting the most appropriate model in terms of balancing between accuracy and computational cost. The present study compares three open-source NWTs in OpenFOAM, SWASH and HOS-NWT, with experimental results for limiting breaking focused wave groups. The comparison is performed by analysing the propagation of steep wave groups and their extracted harmonics after employing an accurate focusing methodology. The scope is to investigate the capabilities of the solvers for simulating extreme NewWave-type groups, which can be used as the “design wave” for ocean and coastal engineering applications. The results demonstrate the very good performance of the numerical models and provide valuable insights to the design of the NWTs, while highlighting potential limitations in the reproduction of specific harmonics of the wave group.</jats:p

Co-located wind and wave energy farms: Uniformly distributed arrays

publisher: Elsevier articletitle: Co-located wind and wave energy farms: Uniformly distributed arrays journaltitle: Energy articlelink: http://dx.doi.org/10.1016/j.energy.2016.07.069 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved

Workshop on identification of future emerging technologies in the ocean energy sector

As part of the Commission's internal Low Carbon Energy Observatory (LCEO) project, the Joint Research Centre (JRC) is developing an inventory of Future Emerging Technologies (FET) relevant to energy supply. A key part of the LCEO initiative is the consultation of external experts, addressing both those with in-depth experience in specific fields and those with a broad perspective on relevant science and engineering aspects. In this context, on March 27, 2018 the JRC organised a Workshop on Identification of Future Emerging Technologies for Ocean Enery, on it premises in Ispra. The workshop was organized on the idea of a colloquium between international experts to discuss about future emerging technologies considering different aspects such as their technology readiness level (TRL) , the potential advantages and challenges affecting their development, and evaluating the possible speed of development . A number of different technological solutions were discussed, identified directly by the invited experts on the condition that they respected the following criteria: • To be a technology for energy supply/conversion in the field of ocean energy. • To be a radically new technology/concept, not achievable by incremental research on mainstream technologies (this should match the concept of the Future Emerging Technology in the Horizon 2020 work program http://ec.europa.eu/programmes/horizon2020/en/h2020-section/future-and-emerging-technologies). • To be in an early stage of development: their Technology Readiness Level should not be more than 3. Questionnaires were sent to experts for the identification of ocean energy FETs. The templates can be found in Appendix B. The structure of the workshop was builtupon the inputs received from the experts and on in-house analysis undertaken by the JRC. The aim of this document is to gather, organize and highlight all the knowledge and information, provided by the external and internal experts, which were discussed during the workshop.JRC.C.7-Knowledge for the Energy Unio