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The offshore wind sector is moving into deep waters and using floating platforms to harness the higher wind speeds in exposed locations. There are various floating platform types currently in development, but semi-submersibles are considered the most prominent early movers. Such floaters need to be towed to and from wind farm locations for installation, special cases of repair and decommissioning. As with any other offshore activity, metocean limits exist for towing operations which can impact the development of a wind farm. It is important to calculate the motion and loads of the platform before commencing the towing operations and to check whether they exceed the defined limits to enable safe execution. In this paper, two approaches using two different numerical tools to predict the motion of a fully assembled floating wind platform under tow are presented and compared. A potential flow-based method derived from a low forward speed approach and a hybrid approach combining potential flow and Morison equation methods are investigated, and the numerical predictions are compared and validated against experimental results. Both methods demonstrate accurate predictions, depending on the wave condition and towing speed, albeit differing in execution time and the simplicity of the simulation setup. The first method was found to provide good predictions of the motion in low-speed (0.514–1.543 m/s) towing conditions. The second method provides better results for all the towing speeds and wave heights. As the wave height and towing speed increase, deviations from experiments were observed, signifying non-linear phenomena that are difficult to analyse using the mentioned potential-flow-based methods. [ABSTRACT FROM AUTHOR]

Marine renewable energy (MRE) development will be crucial to achieve worldwide energy decarbonization. In Europe, 1 GW and 40 GW of ocean energy are set to be developed by 2030 and 2050, respectively. Support is essential if wave and tidal stream arrays are to become more economically viable than they currently are. Four recently developed open-access software tools are used in this study to investigate the critical and expensive elements of potential demonstration and commercial scale tidal projects. The tools have been designed and built to assist users with array configurations, foundation and mooring (F&M) design, operation and maintenance (O&M) strategies, and techno-economic analysis. Demonstration of their use is performed in this study to model scenarios for 2 MW, 10 MW, 40 MW, and 100 MW tidal energy projects employing typical 500 kW fixed and 2 MW floating turbines at the West Anglesey Tidal Demonstration Zone in the Irish Sea. The following metrics are examined: the power output and wake losses of staggered and line configurations; the design and costs of simple gravity-based foundations, gravity-based anchors and the four-chain catenary mooring system of a single turbine; the mean O&M costs and farm availability over the project life; and the breakdown of levelized cost of energy (LCoE) for all eight scenarios to ultimately reveal minimum values of 173 EUR/MWh and 147 EUR/MWh for fixed and floating tidal energy technologies, respectively. The thorough analysis facilitated within these four tools to forecast realistic situations in a specific location can help users design a tidal energy project for an area with considerable potential for commercial scale projects, and thus assist the ocean energy community in promoting and nurturing the sector in the years and decades ahead. [ABSTRACT FROM AUTHOR]

Offshore anthropogenic activities such as the installation of Offshore Renewable Energy (ORE) developments and sediment extraction for marine aggregates have been shown to disrupt current flow, wave propagation, and sediment transport pathways, leading to potential environmental instability. Due to the complexity of the interconnected sediment transport pathways in the south-western Irish Sea combined with an increase in planned anthropogenic activities, the assessment of this risk is imperative for the development of a robust marine spatial plan. Subsequently, this study uses two-dimensional morphological modelling to build upon previous studies to assess the dependency of Arklow Bank's local sediment transport regime on external sediment sources. Additionally, scenario modelling is used to identify vulnerable areas of this offshore linear sand bank to wind and wave-forcing and to examine the nature of this impact. A sediment budget is estimated for Arklow Bank, whereby seven source and nine sink pathways are identified. New evidence to support the exchange of sediment between offshore sand banks and offshore independent sand wave fields is also provided. The areas of the bank most vulnerable to changes in external sediment sources and the addition of wind- and wave-induced flow are analogous. These high vulnerability zones (HVZs) align with regions of residual cross-flow under pure current conditions. The restriction of sediment sources off the southern extent of Arklow Bank impacts erosion and accretion patterns in the mid- and northern sections of the bank after just one lunar month of simulation. Where tidal current is the primary driver of sand bank morphodynamics, wind- and wave-induced flow is shown to temporarily alter sediment distribution patterns. Wind and wave-induced flow can both accelerate and decelerate the east-west fluctuation of the upper slopes of the bank, yet the nature of this impact is inconsistent due to the misalignment of the directionality of these two forces. The methods and new knowledge derived from this study are directly applicable to tidally-dominated environments outside the Irish Sea. [ABSTRACT FROM AUTHOR]

Accurate and up-to-date Geographic Information System (GIS) and Techno Economic (TE) tools are pertinent to helping to develop the renewable energy sector. This paper reviews the state of the art in existing GIS and TE tools for renewable energy and proposes a methodology to develop a coupled GIS-TE software tool that is geared specifically to Marine Renewable Energy (MRE) applications and bespoke to Irish and Western UK waters. Methods for approaching GIS and TE analysis within existing tools for renewable energy are presented and compared. Many existing tools of this nature have some interesting functionalities, but most are unsuitable for MRE; are limited by a lack of information on both the technology and the site; and focus solely either on GIS or TE aspects of analysis. Additionally, almost all of those with a TE focus are not open access. The proposed tool aims to incorporate increased resolution and site relevance of resource data; the most up-to-date geospatial data for site selection; and will provide site specific TE indicators and recommendations for contemporary MRE devices. The result will be the development of an open-access GIS-TE software tool for MRE. [ABSTRACT FROM AUTHOR]

Ireland and the UK possess vast ocean energy resources within their respective maritime areas. However, not all offshore areas are suitable for deployment of ocean energy devices. This article describes the development of a multitude of geospatial data relating to ocean energy site suitability, as well as a Web-GIS tool for hosting and performing analysis on this data. A validation of wave, water depth and seabed character data used in the study revealed good correlation between modelled and in situ data. The data is mapped, and the spatial patterns are discussed with relevance to ORE sector implications. A site selection model, which included much of this data, was developed for this study and the Web-GIS tool. A survey conducted with ocean energy technology developers revealed their desired site criteria. The responses were applied in a case study using the site selection model to uncover potential and optimum areas for deployment of both wave and tidal energy devices. The results reveal extensive areas of the Atlantic Ocean and Celtic Sea appropriate for wave energy deployment and less extensive areas for tidal energy deployment, in the Irish Sea and Inner Seas off the West Coast of Scotland. [ABSTRACT FROM AUTHOR]