Posters

Abstract

A detailed understanding of the site atmospheric and oceanographic conditions is key to the design of offshore wind turbine foundations, a large contributor to the CAPEX of offshore wind farm development. With increasing pressures on achieving lower cost of energy against the backdrop of increasing supply and material costs, a drive for efficient designs which reduce conservatism whilst maintaining safety is underway. Having a clear and accurate understanding of the conditions at an OWF site will allow any unnecessary conservatism to be reduced. In this spirit, the authors would like to share useful and practical advice that will contribute to the progression of the industry as a whole, regarding the characterisation of Turbulence Intensity (TI) as an input to OWF design. TI is a required input for both turbine and offshore foundation design as part of Integrated Loads Analyses (ILAs). Although TI is largely a driver of fatigue loads, it is also necessary to quantify extreme TI levels for Ultimate Limit State (ULS) simulations. Industry standards require a Normal Turbulence Model (NTM) and Extreme Turbulence Model (ETM) to be defined for a site. The standards recommend to derive the ETM by appropriate extrapolation methods such as, for instance, the Inverse First Order Reliability Method (IFORM) or by empirical equations provided in the standards, which aim to derive approximations for these models. Whilst the NTM is generally well understood, in the authors' experience, a consensus on the derivation of an appropriate ETM for an OWF site is less well established. The authors present a comparison of different methods of deriving ETMs at selected offshore measurement sites, providing further understanding on the ETMs' statistical and empirical methods in the context of design and certification.