Optimisation of the Design of Support Structures for Offshore Wind Energy Converters Using Advanced Offshore Engineering Technology

摘要

Exploitation of wind energy offshore puts new demands on the design of the support structure in comparison with land based installations. The extensive experience with the design of off-shore structures for the petroleum industry indicates that these structures are often governed by strength design against extreme environmental loading. In past and existing practice design environmental conditions are determined on the basis of independent estimates of extreme wave, extreme current and extreme wind, each having a return period of e.g. 50 years, while these are all assumed to act at the same time and in the same direction. This deterministic procedure tends to result in (often highly) conservative estimates of design environmental loading. Recent advances in offshore engineering have led to reliability based methods that take correlations in the occurrence of environmental conditions into account. This enables a probabilistic approach and the establishing of much more realistic values for the design load-ing. An essential requirement for this is the availability of a large database containing information on the simultaneous occurrence of wind, waves and current at the intended location. In the present work this methodology has been extended to allow application to a lattice type fixed support structure of an Offshore Wind Energy Converter (OWEC) at an exposed North Sea site.