Last week OWI-Lab and research partner VUB (Vrije Universiteit Brussel) have been awarded by EWEA for having the best scientific poster in Denmark during its annual four day conference.
The poster handles about the first offshore tests and measurements performed by OWI-Lab at Belwind (the 2nd offshore wind farm in Belgium – 55 km out of shore). OWI-Lab provided state-of-the-art measurement equipment in order to measure structural vibrations on the tower and foundation of the turbine. Main goal of this 2-day measurement campaign was to identify the damping ratio of the structure, which is an important parameter for the design of new foundations.
In order to perform these kind of structural measurements, OWI-Lab invested in a brand new measurement system specifically allowing to measure in the low frequency domain. Research partner VUB
(department acoustics & vibrations) joined the team in conducting the offshore measurements, and later performed the post-processing of the data. Next to the frequently used techniques to estimate damping ratio’s in the time-domain (by performing an over speed stop and using the exponential decay method), also state-of-the- art frequency based techniques were used. Nowadays these frequency based post-processing tools like OMA (Operational Modal Analysis) are a standard in industries like aerospace and automotive to get insight in the dynamic behavior of machines. In the sector of wind energy these techniques are getting their introduction.
Titled “Damping Estimation of an Offshore Wind Turbine on a Monopile Foundation” the poster gives an overview of the first measurements and data analysis. Since October 2011, the OWI-Lab measurement system is still continuously monitoring structural parameters on the wind turbine tower. Later this year this large dataset will be analyzed to give better insights in the dynamic behavior of the offshore wind turbine over a long term. Next to that, new OMA-techniques for structural health monitoring of offshore wind turbines will be validated at VUB.
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Offshore WIND staff, April 24, 2012; Image: owi-lab