Developing a new approach to floating offshore wind mooring design and analysis

San Sebastián, Spain: An innovative new method for estimating second order motions could change the way the floating offshore wind industry approaches mooring design. This is the key finding of a new paper co-authored by CoreMarine hydrodynamics expert Carlos Lopez-Pavon.

 The paper was published in Renewable Energy journal together with experts from the University of Sao Paolo and Univseristy of Madrid.  

Titled 'Slow-drift of a floating wind turbine: An assessment of frequency-domain methods based on model tests', the paper examines the correlation between model testing of these second order motions and numerical analysis methods.

Floating offshore wind case study analysis model

Floating offshore wind case study analysis model

Slow drift forces can cause significant loading to the mooring systems of a floating wind turbine. However, these forces are difficult to accurately estimate in numerical analysis software. This lack of accurate modelling results in a tendency among engineers to over-design mooring systems to reduce the risk of failure, resulting in unnecessary extra cost. 

Current modeling and analysis methods require significant computational power and time. In the paper, Lopez-Pavon and the team applied several different numerical analysis methods to hydrodynamic models to calculate slow drift forces. They found the appropriate application of these methods can estimate forces more efficiently and without significant loss of accuracy than current methods allow. 

This expertise allows CoreMarine to continue working at the cutting edge of mooring system design and analysis, offering our clients more efficient, robust engineering. 

Floating offshore wind case study model test

Floating offshore wind case study model test

CoreMarine has a growing focus on floating offshore wind turbines as the industry pushes further from land. Deep coastal waters around significant sections of the US, Japan and parts of Europe require floating solutions in order for offshore wind to be feasible. Successful full-scale prototypes have recently been tested in these markets. Exciting times!

CoreMarine & Under - The Worlds Largest Underwater Restaurant

Oslo, Norway: Europe's first underwater restaurant. A challenging installation on Norway's southern coastline. A monolithic structure made from environmentally-sensitive materials, merging into its rocky surrounds, forming the foundation for a marine life research center. As hydrodynamic and installation engineers dedicated to furthering the blue economy, the opportunity to work with renowned architecture firm Snøhetta and their latest project, Under, is the chance of a lifetime.

This project epitomises the aim of CoreMarine to transfer technology and knowledge from the oil and gas sector into emerging ocean industries.
— Ben Fitzgerald, CoreMarine AS

CoreMarine has partnered with FFS and Einar Øgrey to form SubMar Group, which as a Joint Venture will execute environmental analysis, transport and installation for this unique project. The restaurant will be situated at Båly, a small town near Norway's southern-most point. Project owners Gaute and Stig Ubostad own and operate the Lindesnes Hav Hotel adjacent to the restaurant. Work is expected to be completed and the restaurant opened in early 2019.

The project poses numerous technical challenges all constrained by a very tight budget for the size of the project.

"In oil and gas projects we're used to seeing bigger budgets for T&I [transport and installation] projects like this," explains Ben Fitzgerald, Project Manager for Marine Operations. "We have to keep operations as efficient as possible while not risking the integrity of the structure".

Fitzgerald, who used to work in the oil and gas industry, also said that while many other ocean installation projects choose function over form, it is the form and design of this structure that takes precedence over any functional issues. He explains: "the restaurant doesn't even float horizontally, hence why we have to use a HLV [Heavy Lift Vessel] to maneuver it into position. If this was an O&G project, we would just change the design".

Positioning the restaurant with the Heavy Lift Vessel 

Positioning the restaurant with the Heavy Lift Vessel 

The restaurant will be constructed entirely on a barge and then towed into position. Installation operations will then follow with barge submersion, floating off the restaurant and placing the structure into position with the help of a Heavy Lift Vessel.

    Technical details of the restaurant include:

    • Installation Depth: 5.5m
    • Weight: 1640 tonnes
    • Wall thickness: 500mm reinforced concrete
    • Panoramic Window: 11m long, 42cm thick
    • Capacity: approx. 100 guests

    In addition to the installation work, SubMar has performed wave propagation and wave loading analysis for the structure. This analysis covers both structural considerations for the restaurant structure, while also providing an important tool for the marine research project that will co-exist with the restaurant.  

    Unstructured mesh around restaurant window used for CFD analysis. 

    Unstructured mesh around restaurant window used for CFD analysis. 

    Developed by leading Nibio marine biologist Trond Rafoss, the structure will facilitate research on fish behavior and the surrounding marine ecosystem. The analysis performed by SubMar will allow the flow profiles and current speeds at various depths to be studied and the seabed conditions optimsed to ensure marine life thrives in close proximity to the restaurant's statement viewing window. Discrete lighting will ensure guests are able to see out into the depths. Over time, mussels will take over the outer walls, forming an artificial reef which filters the water and attracts more marine life.

    This restaurant may only be the start. There are plans for further developments of underwater spaces and joint marine research projects internationally.

    "We see a future where underwater spaces that co-exist harmoniously with the surrounding ocean environment are common place and accessible for all to enjoy," says Fitzgerald.

    Under has already captured the attention of global media outlets including CNN, Time and Business Insider. Local Norwegian media including NRK, Aftenposten and DagensNæringsliv have also covered the project. 


    Analysis consultancy contract with DeepOcean Norway

    Installation vessel-  Edda Freya   Picture: Courtesy of DeepOcean

    Installation vessel- Edda Freya

    Picture: Courtesy of DeepOcean

    Oslo, Norway: CoreMarine has delivered a feasibility study report to DeepOcean Norway, covering the retrieval and deployment of large 280 tonne subsea modules using their state-of-the-art vessel Edda Freya.

    CoreMarine worked alongside DeepOcean's Haugesund engineering team to design and develop a module handling arrangement. The team was tasked with pushing the boundaries on module handling in rough sea states. Working in more challenging sea states in turn demands a greater level of control over lifting operations, limiting uncontrolled contact between the module and vessel. 

    Our scope included assessing the vessel motions and motion models, the implementation of model test hydrodynamics into analysis, and performing module lifting and handling analysis in air and through the water column. CoreMarine's specialization in marine and installation analysis enabled DeepOcean's engineers to develop a system that provides a feasible, robust and repeatable operation.  

    The report was the final study delivered under a services contract between CoreMarine and DeepOcean. 

    Core Marine contributed with excellent competency and analysis capacity in this study. They represented a perfect match and supplement to our own engineering team.
    — Deep Ocean Engineering Manager

    CoreMarine delivers towing and stability solutions for tanker module transport

    San Sebastián, Spain: The first two modules of two Suezmax tankers, currently being built by Navantia, have arrived at the Puerto Real shipyard in southern Spain. Construction of the tankers has been split between Navantia's facilities in Fene, Galicia, and Puerto Real, Cadiz. 

    CoreMarine and its partner Iberian offshore are participating in this project in conjunction with freight forwarder Anton Martin, which is handling the transport logistics.

    CoreMarine performed the towing study and barge stability assessment, while Iberian Offshore delivered the seafastening design. 

    These were delivered on time and in line with Anton Martin's high quality standards, within the project's short time frame.


    The first module being prepared for loadout. Image credit: LBG Marine Surveys

    The first module being prepared for loadout. Image credit: LBG Marine Surveys

    The first hull module on its way to the transport barge. Image credit: LBG Marine Surveys

    The first hull module on its way to the transport barge. Image credit: LBG Marine Surveys

    The transport barge laden with the first modules en route to Puerto Real. Image credit: LBG Marine Surveys

    The transport barge laden with the first modules en route to Puerto Real. Image credit: LBG Marine Surveys

    Welcome onboard Sean


    Introducing the newest member of the CoreMarine family: Sean Van Steel.

    Sean is an Australian marine engineer who moved to Norway for a six-month posting… six years ago. The appeal of working at the cutting edge of marine design and analysis from the topside to the seabed quickly had him hooked on Norwegian industry. And the skiing possibilities had him hooked on Norwegian life!

    Sean’s experience ranges from floater design for semis and spars with Aker Engineering & Technology and Kværner Engineering, to subsea and rigid reel installation and analysis with EMAS AMC. His primary focus is design and installation of subsea structures and rigid reeled pipe. Sean most recently lead the EMAS AMC rigid analysis team in delivering the company’s first pipeline installation for AkerBP.

    With his significant offshore experience, Sean is a valuable addition to our team. He shares CoreMarine’s vision of knowledge transfer to the blue economy and we look forward to having him on board.

    CoreMarine and Blueye Robotics sign LOI for research cooperation

    Farsund, Norway: CoreMarine AS is pleased to announce its new partnership with pioneering underwater drone developers Blueye Robotics AS.

    Trondheim-based Blueye produces innovative underwater drones for the consumer and light industrial markets. The Letter of Intent (LOI) signed between the two companies enshrines our commitment to research and industrial cooperation.

    CoreMarine is delighted to ­partner with such an innovative underwater company as Blueye. Not only have they developed some cutting-edge, valuable and very cool technology, but they share our vision for knowledge transfer across ocean industries and using our marine environments sustainably.
    — Oyvind Johnsen, Technology Director, CoreMarine AS.

    CoreMarine and Blueye will collaborate on projects to optimize the drones’ underwater operational capabilities. CoreMarine brings experience from operations based industries including the offshore wind, subsea and seaweed production sectors.

    In turn, the drones will play an integral role in field testing CoreMarine’s subsea projects. With Blueye we’ll take a literal deep dive into our Undervann restaurant installation, seaweed production sites and HavLab ocean test facility.

    CoreMarine Testing Blueye in HavLab, Farsund

    CoreMarine Testing Blueye in HavLab, Farsund

    Welcome onboard Team Spain

    Bienvenido! In March we welcomed team España to CoreMarine. Carlos and José Maria bring with them vast experience in marine design and structural analysis. Based in San Sebastián, our Spanish office will focus their efforts on analysis and design work for the emerging offshore wind industry in Portugal and Spain.

    Carlos Lopez Pavon holds a PhD in floating offshore wind turbines and advanced hydrodynamics. He specialises in marine design and naval architecture with emphasis on CFD analysis.  Carlos has previously worked within Acciona as lead engineer in their offshore wind department. He also brings extensive experience with model testing in both ocean basins and towing tanks. Carlos spends his spare time in his workshop exploring the possibilities of CNC machines and composite materials.

    José M. Gómez is CoreMarine’s structural design and analysis specialist. He has from an early age been intrigued by the ocean and the engineering involved to work with it. After working in various ship design and fabrication roles in Spain and the UK, he joined Global Maritime’s marine design and offshore transport department in London, where he specialized in offshore wind, marine structures, ship modifications and operations. He returned to Spain for a role as a structural engineer within Iberdola’s offshore wind department. Subsequently created his own company specialising in marine and offshore structures, working closely with CoreMarine since its earliest stage.


    Got a question for CoreMarine Spain? Contact us here.

    Offshore Food Production Conference - Tasmania

    CoreMarine was lucky enough to get invited to a conference to discuss a potential research project in collaboration with the Australian Maritime College and the Institute for Marine and Antarctic Studies.

    The project will focus on the sustainable production of food in the ocean environment while calling on competence and technology from the oil and gas industry to develop a suitable platform.

    More info here.