AWEA Blog - Hurricane Sandy's impact on wind turbines minimal

It appears that Hurricane Sandy has had some, but minimal, impact on the
wind turbines in its path, according to early reports this week from
several operators of East Coast wind farms and manufacturers and owners
of smaller turbines, most of which started generating electricity again
after the storm passed.

Initial reports were received by e-mail from a number of wind farm
operators accounting for 68 percent of the total 3,700 MW of wind
generating capacity in the states located in the path of Sandy.

Some companies have yet to inspect all their turbines. The operator of
five turbines near the waterfront in Atlantic City, N.J., reports that
it will be unable to assess damage for several days. Another company
reported yesterday that a project it operates in West Virginia has yet
to restart because the neighboring town is without power, and the site
is located on a mountain ridge top and the roads are impassable due to
snow and downed trees.

Wind turbines are designed to take high winds of 120 to 135 mph, and
some manufacturers make turbines that can withstand even higher winds
for deployment in hurricane-prone areas. However, wind turbine typically
shut down at wind speeds of about 55 mph and rotate to face the wind
with their blades feathered, to minimize any risk of damage.

Reports regarding smaller turbines, though very sparse at this time,
indicate that the machines operated as designed, shutting down when
winds surpassed their cut-off speeds and restarting later.

General background on wind turbines and hurricanes

Major hurricanes are a risk to all property owners in their way,
including all types of power plants. Wind turbines are designed
specifically to harness the wind, but they are also designed to
withstand it. Modern wind turbines utilize several techniques to reduce
the likelihood of harm. Active techniques, such as feathering the
turbine's blades, enable the turbine or turbine operator to protect or
stop a turbine and halt electric generation in extreme weather
conditions. Other techniques wind turbines utilize can include, but are
not limited to:

Turbine brakes -- Most turbines are installed with turbine brakes that
automatically engage if winds reach a certain speed -- usually around 55
miles per hour. At the rated speed, the turbine brakes are applied and
the rotor stops spinning.

Blade feathering -- Wind turbine blades can be tilted (feathered)
remotely by an operator or automatically, so that instead of harnessing
strong winds, wind is allowed to slip through the blades.

Active yaw systems -- Large turbines have active yaw systems that
require a small motor that moves the nacelle (or gearbox, where the
generator is housed) to point directly into the wind. By pointing
directly into the wind, turbine aerodynamics allow wind to flow past the
blades easily.

Heavy monopole towers -- Monopole towers can reach up to 100 meters in
height and are meant to hold nacelles and blades that can weigh several
tons. Thicker monopoles constructed with more steel and internal
structures can support more weight and withstand stronger environmental
forces like wind or waves for offshore structures.

Strong foundations -- For onshore wind turbines, most large-scale
turbines have a foundation pad constructed from concrete. These
foundation pads are usually buried several feet deep to help anchor the
turbine to the ground. Offshore turbines in Europe utilize heavy
concrete gravity-based structures that are placed on the seabed or
monopiles that are driven many feet into the seabed to keep turbines
steady in high winds and waves.

For more information on this article or if you would like to know more
about what www.windfair.net can offer, please do not hesitate to contact
Trevor Sievert at ts@windfair.net

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