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ENERCON E-40 Operating Instructions
Page 79 of 96
ENERCON rotor blades have internal compartments divided by spars. These spars allow to direct a flow of air along the edges of the rotor blade. The heating of the rotor blades is performed by a heater fan installed near the blade flange.The air heated by the heater fan is conveyed through a short pipe towards the leading edge of the rotor blade, from there it will flow to the blade tip and then back towards the blade flange along the trailing edge. Then the air is heated up again and conveyed back into the rotor blade (recirculating air system). In each rotor blade one heater fan is installed. Figure 25 shows how the rotor blade heating is installed.
8.2.2 Operation
The rotor blade heating is activated when outside temperatures equal to or less than 2°C are measured and when at the same time there are indications of a formation of ice on the rotor blades, a fact that can only be established indirectly.
Ice formation on the rotor blades will impair the aerodynamic characteristics of the rotor blades. If the turbine fails to start repeatedly in spite of the wind speed being clearly above the start-up wind speed, this indicates that ice may have formed on the blades. Moreover, ice on the rotor blades often causes an unbalance of the rotor which in turn leads to tower oscillations.
Of course, the rotor blade heating can also be operated manually.
If the control system of an ENERCON wind energy converter equipped with a rotor blade heating detects formation of ice on the rotor blades, the turbine will stop automatically and activate the heating in order to defrost the blades. After defrosting, the turbine will re-start automatically.
The rotor blade heating is dimensioned so as to be able to thaw the ice on the blades with a comparatively low heating capacity. The heating is not able to prevent the formation of ice from the start, because this would require a permanent operation of the heating.
8.2.3 Advantages of the use of a rotor blade heating
Since the control system detects a formation of ice at an early stage, the rotor blade heating can prevent that the turbine runs with iced rotor blades for a prolonged period of time or that it has to be shut down. The energy yield, which is produced is increased. The risk of pieces of ice being thrown off the blades is considerably reduced, especially since defrosting takes place while the turbine is at a standstill.
For reasons of liability, however, ENERCON cannot guarantee that the use of the rotor blade heating will altogether eliminate the risk of larger pieces of ice slipping down from the turbine.
The control of the rotor blade heating is still being refined. Experience gained with the heating up to now seem to indicate that the rotor blade heating can considerably reduce periods of standstill and loss of yield due to the formation of ice on the rotor blades.
Optional Equipment
ENERCON E-40 Operating Instructions rotation direction tip
Page 80 of 96 spar trailing edge leading edge piping heating device fan flow of air blade flange
Figure 25: Sketch of rotor blade heating air tube blade adapter
Optional Equipment
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