Floating Wind Power Performance Testing Explained
To build confidence in the emerging floating wind industry, the performance of the floating wind turbines is crucial.
DNV and its partner, German Wind Engineering Consultancy sowento, provide state-of-the-art power performance measurements. DNV’s Mike Lüdde and sowento’s Steffen Raach explain more about performance testing for Floating Offshore Wind.
How does power performance vary between floating and fixed bottom wind turbines?
Floating wind turbines are unique when it comes to their motion envelope. As opposed to bottom-fixed turbines, the tower base is not attached to a fixed support structure like a monopile, but to a floating platform. The platform moves in multiple degrees of freedom, which leads to static displacements and dynamic motions of the entire wind turbine. These have an impact on the overall power performance of the floating wind turbine.
The impact of the wave-induced pitch-motion, which is the slow back-and-forth movement of the platform, and possible misalignments of the yaw angle, which is the direction the turbine faces, must be considered in a measurement campaign. With a wide range of floating concepts on the market it is crucial for OEMs, investors, developers, and owners to verify the performance of their turbines on a floating substructure.
How does DNV address this problem and what role does sowento play in it?
In offshore power performance measurements DNV typically uses nacelle-mounted lidars, which are aligned with the rotor and can measure the relative wind direction before the wind reaches the turbine. This can accurately determine the undisturbed wind speed at hub height in front of the turbine. As static offsets and motions dynamically affect the measurement location as well as the wind speeds recorded by the nacelle lidar device, a correction of the measured wind speed is required. By analysing the behaviour of the floater under expected met-ocean conditions, a suitable correction method must be established before the start of the measurement campaign to minimize uncertainties of the final results. Using modern measurement technology, the motions of the floater will be quantified, and the assumption of the correction will be verified.
What are the unique benefits of the cooperation between DNV and sowento?
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Testing (left) and Steffen Raach, CEO sowento
“sowento has been one of the early movers for real-time motion compensation of floating lidars and lidars installed on floating wind turbines” adds Steffen Raach, CEO of sowento. “We are happy to combine sowento’s proven solutions in floating wind and lidar applications with the high-quality measurement campaigns of DNV.”