Design of a New Foundation for Offshore Wind Turbines

The gravitation platform and the monopile have in the previous major offshore wind turbine projects been dominating. A four-year research and development project has proven the bucket foundation to be feasible in suitable soil condition in water depth from near shore to app. 40 meters. A prototype was installed at the test field in Frederikshavn in late 2003, with a 3 MW wind turbine in normal operation. The R&D work is continued the complete the bucket concept and having the design standards for the construction and installation methodologies recognised. The design saves about half of the steel weight as compared to a traditional pile foundation, it is much easier to install and it can easily be removed when the wind turbine is taken down. However, the new design is suffering from uncertainties in the accumulated fatigue in the both the steel structure and the surrounding earth material. Therefore an on-line monitoring system has been utilized on the 80 m high operating test 3 MW wind turbine. It is explained how the system is being used to obtain mode shapes and modal parameters during different operating conditions, and how the response measurements are being used to improve the estimation of fatigue.The gravitation platform and the monopile have in the previous major offshore wind turbine projects been dominating. A four-year research and development project has proven the bucket foundation to be feasible in suitable soil condition in water depth from near shore to app. 40 meters. A prototype was installed at the test field in Frederikshavn in late 2003, with a 3 MW wind turbine in normal operation. The R&D work is continued the complete the bucket concept and having the design standards for the construction and installation methodologies recognised. The design saves about half of the steel weight as compared to a traditional pile foundation, it is much easier to install and it can easily be removed when the wind turbine is taken down. However, the new design is suffering from uncertainties in the accumulated fatigue in the both the steel structure and the surrounding earth material. Therefore an on-line monitoring system has been utilized on the 80 m high operating test 3 MW wind turbine. It is explained how the system is being used to obtain mode shapes and modal parameters during different operating conditions, and how the response measurements are being used to improve the estimation of fatigue