Innovative hull design for servicing offshore wind turbines

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Shanley, Matthew
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University College Cork
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Accessing turbines for maintenance is a key operational issue for an offshore wind farm. Currently there is a 1.5m significant wave height (Hs) limit for the standard “step over” method of transferring personnel to an offshore wind turbine, though this varies with, vessel type, wave period and direction, as well as wind, and current conditions. The thesis aims to quantify limiting conditions for access, and increase the Hs at which offshore wind turbines can be accessed. This thesis investigated the motion of novel ship hull designs, and quantified parameters that influence the transfer of personnel from a wind farm service vessel (WFSV) to a wind turbine. To complete the work for this thesis numerical, and physical techniques were utilised to model WFSV designs at zero forward speed in open water, and when docked with an offshore wind farm monopile. When designs were being investigated particular attention was paid to novel hull geometry, and the addition of heaveplates to catamaran hulls. A directional study on WFSV interaction with a monopile was carried out, and polar plots of performance were calculated. The limits of motion that a safe transfer can take place from the literature were compared with those of a basic standard catamaran design, and were then used to assess novel designs. Critical issues at the monopile are, heave, surge, pitch, fender friction and bollard pull, for quartering and beam seas sway and roll are important. Heaveplates provide benefits, however increasing heave damping changes the principal fail condition from vertical slips to horizontal disconnects. Some of these failure cases could be predicted by vessel motion, which may be useful for a warning system. A vessel that can carry out transfers up to a 3.5m Hs was developed.
Offshore wind farm service vessel , WFSV , CTV , O&M , MII , P-Plot , Offshore , Wind farm service vessel , Crew transfer vessel , Operations and maintenance , Offshore wind energy , Motion induced interruption , Levelised cost of energy , Motion compensating gangway , Offshore renewable energy installation , Service operations vessel , Performance plot
Shanley, M. 2018. Innovative hull design for servicing offshore wind turbines. PhD Thesis, University College Cork.
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