Lead Session Chair:
Stephan Barth, Managing Director, ForWind - Center for Wind Energy Research, Germany
Daniel Alarcón (1) F P Climent Molins (1) Xavier Gironella (1) Alexis Campos (1) Pau Trubat (1)
(1) Universitat Politècnica de Catalunya, Barcelona, Spain
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Presenter's biographyBiographies are supplied directly by presenters at OFFSHORE 2015 and are published here unedited
Mr Campos have been involved in offshore structures for wind turbines since 2011, has been participated in the development of 4 patents regarding new concepts of cost-effective floating concrete offshore structures. Prior to this he was working as civil engineer consultant. Currently he is a PhD candidate at Universitat Politècnica de Catalunya, where he is working on the structural assessment of floating concrete structures for supporting offshore wind turbines.
Experiments on a scale model of amonolithic concrete spar for floating wind turbines
Currently, huge efforts have been invested on how to reduce the costs of the new floating offshore wind turbines substructures. Preliminary studies of a concept consisting of a monolithic concrete SPAR platform were presented in 2014. The studies were performed in the framework of the AFOSP KIC-InnoEnergy project (Alternative Floating Platform Designs for Offshore Wind Towers using Low Cost Materials) showing significant CAPEX and OPEX reductions. The experimental phase of the project was developed during 2014.
The experiments comprised a set of hydrodynamic tests performed in the CIEM wave flume facility at the Universitat Politècnica de Catalunya (UPC), with a 1:100 scale model assuming Froude similitude. The complete experimental campaign included free decay tests, a set of 22 regular wave trains of different periods to determine the RAO’s and another set of 21 regular and irregular wave trains in conjunction with a mechanical wind device, simulating the mean thrust force exerted by the wind turbine.
Main body of abstract
The paper will focus on the scale model design, its monitoring and some of the results. Regarding the model design, it was intended to maintain all the external geometry properly scaled to be suitable for future specific experimental tests. Then, a material whose density is close to the concrete one should be selected in order to allow the adjustment of both the weight and the centre of gravity and the pitch/roll inertia. In order to correct the effect of the weight of the instruments used for monitoring or/and manufacturing imperfections between the theoretical and the manufactured mechanical properties of the scale model, a set of adjustable weights inside de scale model was designed assuring such properties, particularly the pitch/roll inertia. The exact position of the weights was finely tuned to exact fit the model properties,
The scaled model of the catenaries was also carefully studied because the constraints in with of the flume facility. An optimized truncated system of catenaries was successfully used.
A mechanical wind device was also specifically designed to ensure a quasi-static force at the top of the model, simulating the effect of the mean rotor thrust force. The pros and cons of using this kind of simple mechanical wind device will be appraised.
A detailed description of the methodology for the experimental campaign will be presented, including the adjustment and checking of the final properties of the manufactured scale model, the mechanical wind device system design and configuration as well as the instrumentation used during the tests. Finally, a summary of the experimental results will be presented.
The paper will offer a comprehensive explanation of the methodology used for the testing program, including the main issues with the facilities, instrumentation, scaling of the prototype, etc. It will also present the data analysis to obtain some of the significant hydrodynamic parameters.