Design of support structures for offshore wind turbines - Wind Power Generation and Wind Turbine Design - page 564

Figure 7: Bunny ears, the pre-fi tting of two blades, purpose-converted installation
vessels, pre-fi tting of J-tube to the transition piece and the installation
of the transition piece.
Figure 8: Heli-hoist platforms are installed on turbines to lower mechanics for
maintenance.
The design was well documented and integrated. The contractors were also invited
to give their own alternative design. The amount of information for this part however
was much less: the support structure was to end at 9 m above the mean sea level and
the only interaction from the turbine was a static load and moment at this 9 m level.
This did not improve integrated design but it can be argued that no contractor at that
time would have any time for more detailed integrated turbine-foundation interaction
analysis as all engineering went into “getting the things there”.
For maintenance all nacelles are equipped with a heli-hoist platform onto which
mechanics can be lowered even when boat access is not possible due to high waves
(see Fig. 8).
The Horns Rev project proved that many practical issues addressed in the paper
studies were applicable in real offshore wind. The amount of overall integration,
or even the need for it is not crystal clear: many individual optimisations could be
done without affecting the entire system.
2.3 Theory behind practice
The installation of the two turbines offshore of Blyth in the UK was part of a large
EU-funded project to study Offshore Wind Turbines at Exposed Sites (OWTES).