Concept design of an installation vessel to install fully assembled next generation offshore wind energy turbines

The shifting of the European energy market towards the wind energy means there will be more wind farms developed in deeper water and farther away from the shore. The existing infrastructure being used for installation is seldom purpose-built for this task, resulting in delays and consequently loss of money for the operators and contractors. Furthermore, the existing process is labor intensive, time consuming and not very safe, the vessels are limited by design to work in moderate sea conditions that for instance exist in the North Sea during the summer season. Seaway Heavy Lifting has been actively involved in solutions for the single lift installation of wind turbine generators (WTG’s). This thesis is to investigate whether there can be a new concept based on improved hull shapes to install WTG’s in a single lift operation more efficiently. The study involves the development of a concept which can provide safe and speedy transportation and installation of fully assembled next generation WTG’s. The selection of the hull shape is based on an extensive but subjective multi criteria analysis using the mission profile and functional requirements of the vessel and available research & operational data. Most important criteria used are: sufficient capacity to carry 8 completely assembled WTG’s of 7MW in vertical position on deck, sufficient speed potential for good North Sea logistics, good motion characteristics for high installation work-ability, sufficient stability to perform the lifting task. From the multi criteria analysis the SWATH (small water plane area twin hull) appears to be the most promising hull shape and is therefore selected for further analysis. Because Seaway Heavy Lifting has more than two decades experience with mono hull heavy lift vessels, a dual draft mono hull vessel dedicated for WTG installation is also analysed for reference. The dimensions of both vessels are determined based on a parametric study in order to comply with the various design requirements. The required deck area and layout together with the strict stability requirements like drop load criteria and intact stability turned out to be important for overall dimensions of both the SWATH and dual draft mono hull. Furthermore a sensitivity analysis is done on these dimensions to check which ones affect the operability of the SWATH. The stability calculations are validated with the help of recognized stability software. Different speed scenarios are evaluated for a given location to check the dependence on vessel speed, resistance and power requirements which could limit the operability. Based on the derived dimensions both vessels are subjected to multi-body frequency domain motion analysis using a recognized hydrodynamics program. Subsequently the workability of both vessels is investigated using very detailed 2D wave spectral data available for an important North Sea wind farm development area. The results of this thesis are the first steps towards establishing the SWATH as a viable option for operating as a WTG installation vessel. The motion behavior of the SWATH is better than the mono hull in certain important operational conditions. There are some significant advantages which the SWATH exhibits over the Monohull and other hull forms which can be utilized for the purpose of WTG installation and helps in avoiding complex installation systems and techniques to get safe and fast operation.

Subject

floating systems
wind turbine

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http://resolver.tudelft.nl/uuid:2024b8f8-56a3-4bd5-a62f-8e1227d7eff4

Embargo date

2017-06-01

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Student theses

Document type

master thesis

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Master_Thesis_Rishab_K.pdf

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