MARIN and NREL have initiated the SCALEWIND JIP to develop a widely accepted floating wind turbine design assessment methodology that leads to efficient design convergence and reduced operational uncertainties for large scale floating wind.


You are kindly invited to the FER Forum, June 26-30 in Paris, France, where this JIP proposal will be presented and an open meeting will be held for interested parties. For mor information and registration:

The Floating wind market is rapidly developing. Wind turbines with power rations of 15MW to more than 20MW are being proposed. These designs are assessed with numerical tools, model tests and medium scale pilot tests in the ocean. With larger turbines the mass of the floater and mooring system become lighter relative to the installed power. While this leads to a reduced cost per unit of produced energy, these larger wind turbines on small floaters also have a tendency to show flexible response of the integrated system of blades, tower, floater and mooring.

Fatigue and survivability of the whole system has to be analysed and validated step by step in an integrated manner for the flexible system. This is important especially when large series of the same design will be produced. The risk of operational cost later in the design life needs to be balanced against the aim for lower LCOE. This can be done by evolving validated numerical models during design and continued learning through monitoring during the operational life.

The objective is to establish validated procedures, models and datasets for the numerical and experimental modelling of the integrated FOWT response. Main points of attention are structural flexibility and the turbine controller. Parameters of interest are the platform motions and accelerations, ultimate and fatigue loads in the tower, floater and mooring system, and the electrical power output. These procedures in turn allow for safe and efficient designs of large-scale FOWT platforms. An overview of the expected outcome is visualised below.


Contact person photo

Gijs Bouman

Project Manager


WP1: Evaluation of current design practices and standards. Identification of knowledge gaps, challenges and risks in the design process for larger scale industrial FOWT.
As a starting point, the current design practices and standards followed by industry will be evaluated together will all project participants. This will highlight the challenges and gaps that inhibit the safe and efficient development of large scale FOWT platforms. It is expected that these challenges lie in modelling the dynamic response of flexible structures, for which the integrated system –floater, mooring, turbine and controller- must be modelled as a whole.

• Review report of current design practices
• Focus points and topics for WP3, WP4, WP5

WP2: Definition of 22MW reference platform(s), turbine, tower and mooring
Open-source reference designs will be set up, on which all other studies can be performed. This avoids the use of confidential data in the model development and validation. NREL is in the process of defining a 22MW reference wind turbine together with DTU. For this turbine, NREL and/or MARIN will define at least one reference semi-submersible platform and mooring system. A semi-sub is foreseen as this is the dominant floater type in industry. A TLP may be added, either by MARIN or by another project participant. As FOWT designs are expected to converge to the stiff-stiff regime for such large scale turbines, the TLP may be expected to become relevant for future FOWT systems.

• One complete, open-source reference FOWT design, comprising a turbine, controller, floater, mooring and reference site conditions.
• Additional reference designs, depending on need and opportunity in the consortium.

WP3: Numerical model development using reference FOWT design(s)
Existing numerical approaches will be used to study the dynamic, integrated response of the reference designs, and compared in a blind comparison. This comparison will further focus the attention points defined in WP1. All project partners are encouraged to submit results, which can be taken as an in-kind contribution. The results will be compared using the work and results from WP4. After the comparison and verification, updated and improved simulations are performed to validate the developed methodology.

• A library of validated simulation results on the reference design(s) and site conditions.

WP4: Stepwise validation of WP3 results, based on model testing and possibly full-scale data
Coupled wave basin model tests will be performed on the reference design(s), using varying levels of complexity. The need for modelling flexibility will be explored in the JIP (see WP1), and associated methodologies will be explored. Both rigid and flexible towers can be used. Blade flexibility may be included in the numerical turbine model of a software-in-the-loop (SIL) test, which comes with a challenge in numerical speed and stability. Alternatively, blade flexibility may be modelled physically in a performance-scaled rotor, introducing a challenge in modelling the bending mode of the blades. Scaling effects will be further studied by performing aerodynamic model tests and/or simulations. For aerodynamic model tests, a wind tunnel or shallow water basin can be used. Full scale data may be available from current medium-scale demonstrator FOWT systems. Depending on availability, these may be used to further validate the numerical results from WP3.

• Improved model test strategies for ultra large FOWT platforms.
• Model test and possibly full-scale data to be used for the validation of numerical approaches.

WP5: Improved methodology development
The results from WP1, WP3 and WP4 will be continuously combined to determine (a) which parameters must be studied in the integrated response of a flexible FOWT system, (b) which effects must be taken into account in the modelling of these systems, and (c) how these effects must be modelled to achieve reliable results, both numerically and experimentally. It will be investigated how a digital twin could be set up to synchronize models and data from simulations, experiments and operational measurements. Such a digital twin can increase the safety, reliability and performance throughout the FOWT system’s life cycle through virtual testing and commissioning, software-in-the-loop experiments and real-time monitoring. The results will be summarized in a recommended practice to industry.

• A validated approach for numerical and model test studies, recommending how a large-scale FOWT platform can be modelled for a reliable result.
• A (description of) a digital twin that supports continuous verification and validation for a FOWT platform.

SCALEWIND is aimed to start in Q4 2023 for a duration of 2 years. The project aims for a 1.2 MEuro budget with 60 kEuro contribution for each partner. A maximum of 30 kEuro in-kind participation is possible and encouraged. The project will also apply for funding in US, EU and the Netherlands.

We encourage JIP partners to actively participate in this JIP. The aim is to discuss a methodology and apply this method to generic floater design, thereby avoiding specific FOWT design details. NREL and DTU are working on a 22MW reference wind turbine design for which MARIN is defining a generic floater. The focus is on an industry wide design methodology that helps platform designers, end-users and certification bodies to assess large scale floating wind turbines in a pragmatic manner.

Contact us if you are interested to participate or if you want to discuss this proposal.