The German research center Fraunhofer IWES has completed tests on two large-scale suction buckets at a 1:5 scale, which confirmed the potential of this foundation concept for reliable and cost-effective deployment in offshore wind farms.
Conducted at the Test Center for Support Structures (TTH) in Hanover, the study aimed to investigate the behavior of the bucket foundations during the suction-assisted installation and its axial behavior when subjected to extreme wave loads.
As jacket substructures for offshore turbines have to stand harsh weather conditions, the focus was on tensile load tests replicating the effect of extreme waves on the structure, which allowed the researchers to confirm that the pull-out capacity of suction buckets increases temporarily during extreme weather conditions.
According to Fraunhofer IWES, the resulting effective temporary increase in tensile capacity during storms means the possibility of material savings for manufacturers for the entire construction without compromising stability.
“We were able to observe that the tensile capacity of the foundation increases temporarily by a percentage in the two-digit range during a typical storm,” said IWES Project Manager Tulio Quiroz . “The increase can be even higher in the case of extreme storm events.”
Besides increases in cost-efficiency, Fraunhofer IWES said that suction buckets enable installation of the substructure and the foundations in one step, low noise installation and the possibility of complete one-step removal of the substructure and foundation elements after the end of the operational life.
The IWES scientists used a bucket with a diameter of 1.4 meters designed for a jacket support structure, while buckets usually have a diameter of six to nine meters. TTH’s foundation test pit is 14 meters long, nine meters wide, ten meters deep and was filled for the tests with sandy sediment, typical of the North Sea.
In order to drive forward research in this field, Fraunhofer IWES plans to assemble a research cluster comprising industry partners, research institutions and approval authorities.