NREL Paves the Way for Floating Offshore Wind Semisubmersible Model Validation

October 18, 2017

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A semisubmersible offshore wind turbine in a research tank.
Models of the OC5-DeepCwind system were validated by comparing simulated data with physical test data from semisubmersible offshore wind turbines.
Photo courtesy of Deepwater Floating Offshore Wind, NREL 19576
National Renewable Energy Laboratory (NREL) researchers have been leading an international effort to validate offshore wind models by comparing physical test data from offshore wind energy systems against the simulated data produced by modeling tools. Analyzing offshore wind system modeling tools enables the development of more innovative and cost-effective designs. This project, called the Offshore Code Comparison Collaboration, Continued, with Correlation (OC5), ran under the International Energy Agency Wind Research Task 30 and involved more than 30 countries and research institutions.

To test numerical models of the OC5-DeepCwind system, researchers used measurement data from a 1/50th-scale test campaign performed at the Marine Research Institute Netherlands offshore wave basin. Model validation assessments compared the ultimate and fatigue loads that were predicted by the modeling tools against the measured data for eight different wave-only and combined wind-and-wave test cases. The measured data included aerodynamics and hydrodynamics loading for fixed-bottom systems and mooring loads for floating systems at both model-scale tank testing and  fullscale open-ocean testing.

With the involvement of so many industry partners, we are able to directly affect the  knowledge and capabilities used throughout the industry.

Amy Robertson
NREL Project Lead

The project involved participants from across the offshore wind industry field, including offshore wind designers, consultants, certifiers, developers, and research institutions. Results indicated that industry design tools adequately estimate the tower and mooring loads in the structure, but with a consistent underestimation for this system, which will require further investigation.

“Validated modeling tools can be used to develop optimized designs to reduce costs,” said NREL project lead Amy Robertson. “With the involvement of so many industry partners, we are able to directly affect the knowledge and capabilities used throughout the industry.”

Validation campaigns help to assess the accuracy of the offshore wind system modeling tools, provide a better understanding of the uncertainties in those tools, and identify areas for improvement—and are essential for reaching commercial maturity for offshore wind technologies. Validated modeling tools can then be used to develop optimized designs to meet the U.S. Department of Energy's goal of reducing the cost of offshore wind.

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