In this work, it is evaluated the accessibility of a floating platform, by means of a catamaran vessel equipped with a fender. The two bodies are modelled as a constrained multi-body system in the frequency domain. Transfer functions are calculated for the motions and forces of the system. Access is possible when no slip conditions occur at the fender, and when the relative rotations between the two bodies are within certain tolerance limits. Four response variables are defined to impose such conditions. In a short-term sea state the extreme maximum crest height of these variables is computed, assuming that response crest heights follow a Rayleigh distribution. Each of the extreme values is compared to a specific threshold, to determine whether access is possible or not. Accessibility is calculated for a sample platform located off the coast of Scotland using hindcast data for the period 1980-2013. Average accessibility resulted to be 23.7%. A strong seasonality is ascertained, together with a large variation of accessibility, due to the variability of wave climate. ; The authors would like to acknowledge the projects "OceaNET", which received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 607656, and "Plataformas multiuso para aplicaciones offshore" of the University of Cantabria (code: 56.JS05.64061).
ABSTRACT: Operations and installation on offshore wind and especially floating are complex and difficult actions due to site accessibility and equipment availability. In this regard, digitalization is disrupting the wind section thanks to the development of advanced sensors, automated equipment, computational power, among other. All these allow to optimize and simplify different parts of the offshore wind power plant development (i.e. design, planning, installation, O&M, etc.). This fact is of special interest on maintenance, since the early detection of failures or malfunctions lead to reduced costly corrective maintenance. This paper presents a literature review of current state-of-the-art on the application of digitalization activities which can be applied for floating wind, including typical component failures, monitoring techniques and advanced digital tools as Digital Twin concept and Building Information Models (BIM). Finally, the review paper provides an analysis of existing gaps, needs and challenges of the sector to provide guides on research and innovation to foster offshore wind sector. ; The research leading to these results has received funding from the European Union's H2020 Programme under Grant Agreement n◦ 815083 – Corewind
ABSTRACT: Bottom-fixed offshore wind turbines are generally built on continental-shelf sections that are morphodynamically active due to their shallow depths and severe wave and current conditions. Such sites are commonly protected against scour to prevent the loss of structural stability. Scour protection can be designed using static or dynamic solutions. Designing dynamic protection requires experimental validation, especially for singular or unconventional structures. This article presents an experimental method for the laboratory analysis of scour protection for jacket foundations placed at morphodynamically active sites. The test campaign was conducted within the project East Anglia ONE (UK) as part of the asset owner studies and aimed to evaluate operation and maintenance (O&M) aspects, independent of the contractor?s original design assessments. The physical experiments explored morphodynamic changes on the sea bottom and their importance to scour protection, as well as the importance of the history of the wave loads to the deformation of the rock scour protection. This was explored by repeating different cumulative tests, including a succession of randomly ordered sea states (Return Period (RP) 1-10-20-50 years). The experimental results show that the deformation of the rock sour protection was the greatest when the most energetic sea states occurred at the beginning of the experimental test campaign. The maximum deformation was at 5D50 when the first test was also the most energetic, while it was at 3D50 when not included as the first test, yielding a 40% reduction in the scour protection deformation. ; This research was part of the Scour Protection Jacket Project (SPJ) and was carried out with Iberdrola and GITECO. The authors acknowledge financial support from the Regional Government of Cantabria through the R&D program PROYECTOS DE I+D+i EN COOPERACIÓN EN ENERGÍAS RENOVABLES MARINAS-2016 (the RM-16-XX-029). Raúl Guanche also acknowledges financial support from the Ramon y Cajal Program (RYC-2017-23260) of the Spanish Ministry of Science, Innovation and Universities.
ABSTRACT: This paper provides a summary of the work done within the OC6 Phase II project, which was focused on the implementation and verification of an advanced soil?structure interaction model for offshore wind system design and analysis. The soil-structure interaction model comes from the REDWIN project and uses an elastoplastic, macroelement model with kinematic hardening, which captures the stiffness and damping characteristics of offshore wind foundations more accurately than more traditional and simplified soil?structure interaction modeling approaches. Participants in the OC6 project integrated this macroelement capability to coupled aero-hydro-servo-elastic offshore wind turbine modeling tools and verified the implementation by comparing simulation results across the modeling tools for an example monopile design. The simulation results were also compared to more traditional soil-structure interaction modeling approaches like apparent fixity, coupled springs, and distributed springs models. The macroelement approach resulted in smaller overall loading in the system due to both shifts in the system frequencies and increased energy dissipation. No validation work was performed, but the macroelement approach has shown increased accuracy within the REDWIN project, resulting in decreased uncertainty in the design. For the monopile design investigated here, that implies a less conservative and thus more cost-effective offshore wind design. ; The authors would like to thank the Norwegian Geotechnical Institute for their work in the REDWIN project to develop the capability being incorporated in OC6 Phase II and to provide the data to model the foundation as well as for their ongoing support. We would also like to thank the Norwegian University of Science and Technology for their support in developing the model for this project. This work was authored in part by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the US Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding is provided by the US Department of Energy Office of Energy Efficiency and Renewable Energy Wind Energy Technologies Office. The views expressed in the article do not necessarily represent the views of the DOE or the US Government. The US Government retains, and the publisher, by accepting the article for publication, acknowledges that the US Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work or allow others to do so, for US Government purposes.
ABSTRACT: The present paper describes the experiences gained from the design methodology and operation of a 3D physical modelexperiment aimed to investigate the dynamic behaviour of a spar buoy floating offshore wind turbine. The physical model consists in a Froude-scaled NREL 5MW reference wind turbine (RWT) supported on the OC3-Hywind floating platform. Experimental tests have been performed at Danish Hydraulic Institute (DHI) offshore wave basin within the European Union-Hydralab+ Initiative, in April 2019. The floating wind turbine model has been subjected to a combination of regular and irregular wave attacks and different wind loads. Measurements of displacements, rotations, accelerations, forces response of the floating model and at the mooring lines have been carried out. First, free decay tests have been analysed to obtain the natural frequency and the modal damping ratios of each degree of freedom governing the offshore. Then, the results concerning regular waves, with orthogonal incidence to the structure, are presented. The results show that most of longitudinal dynamic response occurs at the wave frequency and most of lateral dynamic response occurs at rigid-body frequencies. ; This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 654110, HYDRALAB+.
