Environmental Engineering Reference
In-Depth Information
fore, spars may not be suitable for sites less than 200 m, which could be way off
limit for future wind power plants over the next 10 years. Spars also face other
challenges similar to TLPs [16].
5.1.4 Hybrid tethered system
It is conceivable that the ultimate tethered concept may be a hybrid between
the high-tension-high-buoyancy TLP and the spars in which lateral stiffness is
provided by both ballast at the foundation keel and tension in widely separated
tendons as seen in Fig. 12. The hybrid system will have the following features:
•
Blasts at the keel ends, which is well assisted by the high-tension tendons, to
provide lateral stability. The high tendon tension comes from the high buoyancy
in the hull design.
A hull with a liquid column oscillation damper, which consists of channels
•
utilizing the differential inertia of water across different hull compartments to
reduce lateral wave load. Liquid column dampers could either be actively
tuneable or passively set at fi xed frequency. Preference might be given to the
passive system so as to reduce the reliance on the control system for the over-
all stability.
It is still likely that the turbine's tolerance for lateral sea level angular rotation
will have to be widened even after all the efforts. The appropriate implications to
the control system design and the drive-train component design need to be
addressed accordingly in turbine design.
Recently there have been efforts from several offshore engineering groups and
wind turbine OEMs to put prototypes fl oating foundations with wind turbines on
Tower
Water level
High-Buoyancy
Hull
Liquid Channels
(Inside Hull)
Columns
Columns
Mooring
lines
High
Tension
Tendons
Figure 12: Hybrid tethered system.
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