Floating Offshore Wind Array Design

NREL will develop a modeling tool set for optimizing large-scale floating offshore wind farm array designs and create reference designs for several U.S. sites.

Large-scale floating offshore wind farms will be key contributors to meeting federal deployment and decarbonization targets. However, large arrays of floating offshore wind turbines pose an unprecedented engineering challenge. To minimize the cost of energy and optimize a wind power plant, many interrelated parts of the design need to be considered simultaneously: the individual floating offshore wind turbines, the turbine array layout, the mooring lines and anchors, and the subsea power cables. These design aspects—along with their performance, cost, logistical, and reliability implications—need to be considered at the array scale. The impacts of the wind power plant on the environment and other ocean users are also key factors. Addressing all these considerations holistically calls for new design tools and methods.

The Floating Wind Array Design project is a 3-year, $3 million effort by NREL to develop an integrated design tool set to systematically design all parts of a floating offshore wind farm array for given site conditions. The tool set will:

• Build on existing NREL engineering tools that are open source and widely used
• Fill key gaps in analysis capabilities for floating offshore wind turbine arrays
• Integrate these tools in a holistic framework that addresses the unique challenges of floating offshore wind turbine array design.

The project will also apply the tool set to develop several reference floating offshore wind turbine array designs for U.S. conditions. These designs can then be used as baselines for follow-on research and development activities to advance floating offshore wind energy technology at the array scale.

In addition to the development of reference designs for floating wind sites in the United States, the project will contribute to the International Energy Agency Wind Technology Collaboration Programme (IEA Wind) Task 49, the Integrated Design of Floating Wind Arrays research collaboration. NREL co-leads IEA Wind Task 49 and will provide technical contributions in the areas of United States-based site characteristics and application of the Floating Offshore Wind Array Design tool set to optimize a globally relevant set of reference designs.

As floating offshore wind turbine arrays are planned for U.S. waters, the Floating Wind Array Design project’s tool set, reference designs, and international engagement will serve to inform design decisions and help ensure cost-efficient and responsible offshore wind energy deployment.

The project, funded by the U.S. Department of Energy Wind Energy Technologies Office through the Bipartisan Infrastructure Law, involves collaboration with IEA Wind and includes academic partners.

Objectives

In this project, NREL researchers will:

• Add realistic seabed, anchor, and dynamic power cable models to NREL design tools
• Integrate new and existing models into a streamlined, multidisciplinary analysis capability for floating offshore wind turbine arrays, including modeling failures at the array scale
• Create a holistic floating offshore wind turbine array optimization framework for coupled design of array layout, mooring systems, and power cabling under realistic site-specific conditions
• Develop reference floating offshore wind array designs for different geographic regions in the United States. These reference designs will be part of the United States contribution to IEA Wind Task 49.

Tasks

The Floating Offshore Wind Array Design project has three parallel tasks.

Task 1: Developing and Validating Seabed, Anchor, and Cable Models

Current open-source modeling tools for floating offshore wind turbine arrays do not account for seabed characteristics, anchor strength, and dynamic power cables. This task will fill these gaps. NREL will create a model that represents seabed soil characteristics and the strength of different anchor technologies as a function of those characteristics. NREL will also introduce capabilities for evaluation of seabed characteristics and dynamic power cables to MoorPy, a computationally efficient mooring system design tool developed by NREL. These additions will allow users to model a broader set of design drivers for floating offshore wind farm arrays.

Working with university partners, NREL will also run wave basin experiments to create an open data set for validating the modeling capabilities.

Task 2: Creating an Integrated Floating Wind Array Analysis Capability

Design and optimization of floating offshore wind turbine arrays require modeling of all design-driving considerations, including power production, dynamic response to metocean conditions, and cost, reliability, and siting factors. FAST.Farm is a capable midfidelity engineering modeling tool for floating offshore wind farms, but an orders-of-magnitude-faster tool is needed to efficiently explore array designs. This task builds on existing capabilities to create a tool that integrates with cost, logistics, and other models—such as for estimating impacts on the environment or other ocean users—to enable rapid evaluation of floating offshore wind turbine array designs. 

Task 3: Developing and Applying Floating Offshore Wind Turbine Array Design Methods

In floating offshore wind turbine array design, turbine motions and mooring and cabling requirements create spacing constraints and a strong dependence on local seabed conditions. These complexities call for an approach to optimize over the multiple scales and inherent discontinuities of the floating offshore wind turbine array design problem. Task 3 will develop an optimization framework, which will be incrementally applied to create a set of reference floating offshore wind farm array designs to serve as baselines for follow-on floating offshore wind farm array research. These efforts will contribute to IEA Wind Task 49.

Outputs

The Floating Offshore Wind Array Design project will run August 2022–September 2025 and produce:

• An open repository of experimental results to validate dynamic models for mooring systems, dynamic power cables, and arrays of floating platforms
• An open-source software tool for multidisciplinary floating offshore wind turbine array modeling with examples and documentation
• An open-source software tool set for floating offshore wind turbine array design optimization with examples and documentation
• An open repository of reference floating offshore wind turbine array designs for U.S. site conditions.

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