Since 2011 OWI-Lab has been conducting acceleration measurements on an offshore wind turbine with a monopile substructure at the Belwind wind farm. The main goal of this R&D measurement campaign was to validate the design with in-situ measurements on the operational wind turbine. In particular the resonance frequencies were of interest to the operator as these can shed light on the soil conditions at the site.
Initial results confirmed that the actual resonance frequency was well above the as-designed values.Other researchers noted similar observations at different wind farms, concluding that in the design process the soil-stiffness was underestimated.
However, after these initial results OWI-Lab continued their monitoring activity at the Belwind wind farm and kept an eye on the resonance frequencies of the offshore wind turbines. As such changes in the soil conditions, e.g. scour, could be detected.
Result show that over the course of 5 years the second resonance frequency has been gradually increasing over time. As such the current turbine has a resonance frequency that is 3% higher than observed in 2011.
This temporal evolution indicates that soil conditions at offshore wind vary over time and motivate the continuous monitoring of the resonance frequencies over time.
This long-term R&D effort at the Belwind offshore wind farm was rewarded with the award for best R&D poster in the category turbine technology at the Wind Europe Offshore wind energy conference in London. The rewarded R&D poster made by Wout Weijtjens can be download here.
Aside from this research OWI-Lab also presented other interesting R&D posters on damping, virtual sensing and condition monitoring. Researcher Nymfa Noppe also gave a talk at the conference about her work on SCADA based load assessment
You may find all OWI-Lab posters and presentations here.
The other awarded posters during the poster ceremony can be found here.