Session: 09-01-03 Installation, Marine Operations and Maintenance - 3

Paper Number: 80926

80926 - A Comparison of Approaches for Modelling Walk-to-Work Gangway Access 

With increasing number of installed offshore wind turbines, accurate operations and maintenance (O&M) planning also becomes increasingly important. Offshore O&M activities have to minimise yield losses, whilst being as cost-effective as possible. One key part of any current O&M strategy is technician access to the wind farm assets. A clear understanding on the limits of that access can assist with planning and cost modelling at early stages of a wind farm project, as well as optimise ongoing activities.

It is anticipated that on larger farms the majority of turbine access will be via motion compensated walk-to-work (W2W) gangways. To date there have been efforts to mathematically model gangway movements in different sea states, and thus arrive at a workability analysis for a gangway between a vessel and a turbine foundation, for both fixed-bottom and floating typologies. However, the representation of the gangway in these models is implicit, and focusses on the relative movement of the gangway tip and pedestal in global space. Here, a comparison is made between an implicit representation and an explicit representation with a higher fidelity to current commercial gangways. A model of a commercial vessel connected via W2W gangway to a fixed foundation is created for both implicit and explicit representations, and the maximum workable significant wave height is derived for each. 

The results show that the implicit representation does not fully capture the motions between subcomponents of the gangway, and leads to an overestimation of the workable sea state, when compared to the explicit representation. In certain prevailing wave directions, using an implicit representation can in fact overestimate the workable wave height by as much as 160%. This finding will inform any further modelling of W2W gangways for workability analysis and O&M planning. 

Presenting Author: Ben Moverley Smith Xodus Group

Authors:

Ben Moverley Smith Xodus Group
Ben Middleditch Xodus Group
Philipp Thies University of Exeter College of Engineering, Mathematics and Physical Sciences Renewable Energy Group