It is anticipated that the market for offshore turbines will significantly outstrip the current manufacturing capacity. This work examines a new and innovative fabrication process for offshore wind turbine foundations which has the potential to allow the necessary production capacity to be met.
Several foundation concepts are being considered for the next generation of offshore turbines, including monopiles, tripods and braced jacket structures. All are manufactured from tubular steel sections. Typically, these are fabricated by rolling thick plate and welding longitudinally to produce cans and then joining the sections together with circumferential welds. Rolling thick plate (>100mm) requires heavy rolls and hence high capital investment, limiting the number of facilities capable of carrying out the process. It is also a time consuming operation and the length of each can is restricted by the width of the rolls and plates, commonly to 3-4 metres. The novel multi-faceted design proposed in this work is fabricated from strips of flat plate welded together longitudinally, hence eliminating the rolling step. This allows sub-assemblies of greater than 10m in length to be manufactured, reducing the number of circumferential welds necessary in the foundation. This approach is enabled through the use of rapid, thick-section welding for the longitudinal seams.
This work has considered the geotechnical and structural aspects of the proposed design concept. The entire production route has been examined in terms of performance, logistics and economics, in order to determine the viability of the multi-faceted approach.