Suction buckets face wave load testing

GERMANY: Researchers from Fraunhofer IWES are examining the behaviour of suction buckets in extreme wave loads at a German university's test centre.

Submersion of the bucket took an hour during testing, Fraunhofer IWES stated (pic: Pascal Hancz)
Submersion of the bucket took an hour during testing, Fraunhofer IWES stated (pic: Pascal Hancz)

Fraunhofer's Institute for Wind Energy Systems (IWES) have installed a suction foundation, which features a 1.4 metre wide bucket at its base. In real-life applications, the same components can reach diameters of between 6 and 15 meters.

Once the bucket has been in position for a few days at Leibniz Universität Hannover's Test Centre for Support Structures in northern Germany, tensile load tests simulating the effects of extreme waves will begin.

Fraunhofer IWES hopes to learn more about suction bucket foundations from their demonstration project, and plan to share conclusions with "industry partners in the scope of research projects", the institute stated.

"It is extremely important to monitor the negative pressure closely to avoid damaging the seabed and ensure the bucket remains level," said IWES project manager Tulio Quiroz.

"For this reason, separate chambers are employed in the bucket during offshore installations, with the aim of regulating the pressure."

Model testing is carried out in a foundation test pit, which provides wave and weather conditions and a sandy model seabed representative of those typically found in the North Sea.

Suction bucket installation is fast and avoids the pile-driving noise often associated with offshore wind farm foundations, meaning it could be used at sites subject to noise restrictions, Fraunhofer IWES stated.

It is also reversible and can be carried out without using heavy equipment, the researchers added.

Installation is carried out by pumping water out of sealed containers (‘buckets’) to build up negative pressure, which draws the structure into the seabed.

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