Nowadays there are few methodologies related with the design of mooring systems for floating offshore wind platforms. The ones used until the moment are inherited from the oil and gas industry. Because of that, mooring loads may be incorrectly estimated. This study presents a validated methodology in order to estimate the loads of the moorings of offshore floating platforms along the life cycle of the structure.
The methodology is based on an extensive laboratory test data base carried out in a wave basin of the University of Cantabria. The proposed methodology has been applied to a floating semisubmersible platform (similar to the one in Agucadoira by Principle Power).
The methodology is composed by a few steps. The first step consist on the selection of the most representative sea states of a long term met-ocean data base through a selection technique named MDA (Maximum dissimilitude algorithm). Afterwards, mooring system loads and platform motion are numerically simulated. SESAM (DNV) numerical model has been used in this particular application. SESAM numerical model was previously calibrated based on the laboratory tests. Finally, based on a multidimensional interpolation technique named Radial Basis Function life cycle mooring system loads were reconstructed.
A sensitivity analysis of the methodology were carried out. Based on it, it can be concluded that selecting 1000 sea states with the MaxDiss technique, life cycle mooring loads can be accurately predicted.