Unblocking critical design challenges of pre-commercial floating wind turbines

CENER presented this January at the EERA DeepWind conference the challenges of engineering software applied to floating wind and our innovative solutions to face them. EERA DeepWind is an annual international conference that gathers the best R&I initiatives in offshore wind.

In the last years, we have witnessed a rapid development of floating wind energy solutions, with many innovative concepts approaching the market. A few prototypes have demonstrated their viability by reaching TRL 7 (Technology Readiness Level), many others haven’t got yet that far, despite of presenting a great potential for LCOE reduction.

As the TRL of floating wind turbines increases, it becomes necessary to have better software to support the design phase, reducing risks and increasing reliability. Engineering design software that will help reduce the LCOE of floating wind, as it did in the first decade of the XXI century for onshore wind.

After working with more than 30 floats in recent years, CENER provided DeepWind with a transversal vision of the most critical technical problems of simulation tools, partially solved or pending resolution.

• Higher fidelity hydrodynamic models to perform analyses coupled with the wind turbine model for the design of the turbine-platform floating unit, as well as in particular cases of some designs, such as “weathervanning”.
• Structural pressure distribution and fatigue under the effect of waves and ocean currents are also critical design factors and areas for improvement. In the case of structural fatigue, frequency domain analysis commonly used in software for offshore infrastructure is not suitable due to the non linearities of the wind phenomena, being necessary to perform the calculations by means of simulations in the time domain.
• It has been shown that onshore wind aerodynamic models are inaccurate under certain wind turbine operating conditions. Situations that have been rare in onshore wind, but will be much more frequent in floating offshore wind. Aerodynamic codes must accurately simulate these cases: wind turbines misaligned with the wind and the interaction of the rotor with its own wake. Both cases are critical for platforms with large movements, high flexibility rotors and large wind turbines, above 10MW.
• The “brain” of the wind turbine must consider new dynamics at sea. Wind turbine controller strategies for floating conditions should minimize negative damping or “Yaw” rotation of the wind turbine, without losing production and reducing loads.
• Finally, advanced simulation tools during the design stage must also contribute in the operation stage. The maintenance strategy should incorporate digital twin information to reduce the number of interventions at sea and increase the productivity of corrective maintenance.

As increasing the reliability and reducing LCOE should be the main objectives of the floating wind community, solving previously mention technological challenges is the goal of the wind R&D community for the upcoming years. DeepWind served CENER to present the challenges and also highlight the developments with which plan to address these challenges. In some cases highlighted below, CENER can already provide an image to present the results.

Multi wind turbine simulation with wake-wake interaction and wake-structure interaction.

Wind turbine model (OpenFAST) coupled with hydrodynamic model (OpenFOAM).

Turbine control for self-aligning floating platform (minimize weathervanning)