Reduce the Cost of Energy of offshore wind by:
WMC created a FOCUS6 model of the 2B6 turbine including the support structure. This model was made available to ECN for use in their controller design and load calculation analysis activities. Eigenfrequencies of the support structure as predicted by FOCUS6 are found to match those provided by 2BE. The FOCUS6 model of the 2B6 turbine has been used for testing purposes in the further development of the Support Structure Modeler included in FOCUS6.
Automated joint and member strength evaluation is implemented in the FOCUS6 Support Structure Modeler. The joint evaluation concerns both the ultimate and fatigue strength. With this automated strength evaluation in place, it is possible to set up an automated optimization in FOCUS6.
For the automated optimization, the design space has been limited to cross section dimensions. That means that member diameters and wall thicknesses can be parametrized, and that the connectivity of the joints and members is as defined by the user. By choosing values for the parameters, the optimization program selects a particular geometry of the support structure. FOCUS6 then creates a model of the support structure, simulates the required load cases, computes the required joint loads and member loads and evaluates the joint and member strengths with respect to these loads. When the optimization program finishes after a number of iterations, the user can inspect the result. Reports are generated automatically in which the joint and member strengths are given, and the joint strengths can be visualized to see what fatigue damage is incurred by the joints.
A representative jacket support structure, supporting a 5 MW offshore wind turbine, is optimized in an integrated way with the turbine, including the controller, thereby taking into account the dynamics of an operating offshore wind turbine system.
The results show that running such an automated optimization in the integrated wind turbine design tool FOCUS6 is possible, using the automated strength evaluation developed in this project. The present study showed a reduction of the highest joint lifetime fatigue damage in the support structure by 18.8% compared to the baseline configuration, without an increase in jacket support structure mass.
M.J. de Ruiter and T.J.J. van der Zee "Strength evaluation of support structures in FOCUS6", Report WMC-2014-040
T.J.J. van der Zee, M. J. de Ruiter, R.R.H. Brood "Wind turbine support structure optimization using an integral design approach - Optimizing a jacket support structure in FOCUS6", Report WMC-2015-050
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