Keynote: NGM 2008: Implementation of a new foundations concept for Offshore Wind farms

ABSTRACT: The foundation principles for the recent major offshore wind farm projects in Europe have been dominated by two types of foundation solutions, the gravitational foundation and the monopile. A fully operational 3.0 MW offshore wind turbine was installed on a prototype of the bucket foundation at the test field in Frederikshavn in December 2002. A five-year research and development project has proven the bucket foundation to be feasible in suitable soil conditions in water depth from near shore to approximately 40 meters. The bucket foundation design reduces the steel weight by half compared with a traditional monopile solution and the installation of the bucket foundation is much easier and does not require heavy installation equipment. In this paper the full-scale field installation of the prototype is described. A design procedure has been developed in cooperation with the certifying party in order to maintain an approval procedure in future projects. In order to develop these design procedure relevant studies involving techniques as diverse as laboratory model testing, field trials at reduced scale, and a full-scale field installation, has been performed. The nature of these tests is outlined. The main problems witch has been studied, in order to reduce the uncertainties in the new design of the bucket foundation, is the in service performance. The in service performance is evaluated and compared with the design criteria’s for the prototype