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9.0 Wind Turbine Operation
NOTICE: Use of the material contained in this document is subject to the warning on page Iv and the disclaimer
on page v of this document.
DOC012R02 AOC 15/50 User Manual Nov 2001
82
Wet snow may affect tip brake operation, possibly causing premature deployment or, in severe
cases, damage due to the additional weight on the tip brake plate. Severe icing may also inhibit
the tip brake from deploying correctly.
Ice build-up on the anemometers can prevent a wind turbine from starting up. If it is already
running, the anemometers may ice up before the blades, indicating conditions in which the wind
turbine should be shut down.
Normally, the ice will melt in a reasonable amount of time. In certain cases, it can be removed
by gently tapping it off the anemometers, the tip brakes and the blades. To do this the machine
must be switched OFF. If there is only a thin layer of ice on the blades, jogging the machine
very briefly may remove it. The anemometers, blades and tip brakes must be free of ice before
switching the turbine ON/OFF/TEST switch to ON. Prior to starting up a wind turbine, which
has ice adhering to the blades, make sure that personnel are protected from any ice that might fly
off them.
9.4.4 Temperature and Elevation
Although calculable, elevation and temperature extremes do not adversely affect a wind
turbine’s operation. The design temperature range is -40°C to +64°C (-40°F to +147°F) with no
altitude constraints.
The power generated by a wind turbine is a function of wind speed and air density. Higher wind
speeds produce more power. Variations in temperature and relative humidity, at any given
altitude, have a more subtle effect. As temperature increases, air density decreases, reducing
energy output. Conversely, at lower temperatures, energy output will increase, proportionally to
the increase in air density. The formula below allows energy output to be corrected, taking
altitude and temperature into consideration.
Where P
s
is power output at sea level at 15°C (59°F) and C
t
and C
a
are correction factors for
temperature and altitude. They are defined as follows:
Where T is temperature in °F and A is altitude in feet.
C
*
C
*
P
= Output Corrected
at
s
966
1000A/
a
= .
C
460
+
T
5
=
C
t
19