A comparison of approaches for modelling walk-to-work gangway access

Abstract

The accessibility of offshore wind farms is a key parameter when considering the cost of the operations and maintenance (O&M) of wind farm assets. Indeed, the weather limits for accessing wind turbines is a critical input in many tools which seek to simulate and optimize O&M activities. To refine this input, numerical modelling has been performed previously to perform workability analyses for service operation vessels with motion compensated walk to work gangways. However, previous modelling effort has employed an implicit representation of a gangway, which does not consider the relative motion of gangway subcomponents. In this study, two different gangway representations are employed for a numerical simulation of a transfer procedure between a service operation vessel and an offshore turbine. Comparison of the limiting wave heights given by analysis of the implicit and explicit representation of the gangway shows a difference when considering waves incident toward the vessel from the foundation location, with much lower wave heights allowed by the complex representation. Applying this difference in operational wave heights to a case study location leads to a difference in overall site availability of over 9%. The implications of these findings on future accessibility analysis and foundation design are discussed.