Enercon 2.5 MW Wind Turbine

This is from the Enercon wind turbines website in Germany.
It describes the E-70 model of their wind turbine production.

Technical Data

Rated power: 2,300 kW
Rotor diameter: 71 m
Hub height:
57 m / 64 m / 74 m / 85 m / 98 m / 113 m
Wind zone (DiBt): WZ III
Wind class (IEC): IEC/NVN IA und IEC/NVN IIA
Turbine concept: Gearless, variable speed, single blade adjustment

Rotor

Type: Upwind rotor with active pitch control
Rotational direction: Clockwise
No. of blades: 3
Swept area: 3,959 m²
Blade material: GRP (epoxy resin); integrated lightning protection
Rotational speed: variable, 6 - 21.5 rpm
Pitch control: ENERCON single blade pitch system, one independent pitch system per rotor blade with allocated emergency supply

Drive train with generator

Main bearing: Double-row tapered / cylindrical roller bearings
Generator: ENERCON direct-drive annular generator
Grid feeding: ENERCON inverter
Brake systems: 3 independent pitch control systems with emergency power supply, rotor brake, rotor lock
Yaw control: Active via adjustment gears, load-dependent damping
Cut-out wind speed: 28 - 34 m/s (with ENERCON storm control)

Critique

Note also that at 21 rpm, that's three blades passing every point in the swept area in just less than three seconds, and the blade tips are moving at over 105 m/sec, over 200 mph. I doubt that the cut out wind speed is low enough, it implies that the turbine is allowed to spin (no doubt feathered) in gale force winds. Presumably they have great faith in their storm control. The  Beaufort scale rates wind speeds of 28-34 m/s as violent storm, Force 11, just less than a hurricane. The website proclaims "tried and tested technology" but have they really tried and tested these in half a hurricane?

Attribution:

This picture is from Wikipedia commons as Size_comparison_child_in_wind_turbine_rotor_hub_without_blades_(enercon_e-70).jpg,
taken in January 2012 on the island of El Hierro by Erik Streb.

I wondered what a wind turbine was doing on an island designated as a  Biosphere Reserve but the Energy section of a Wiki article reveals that in this case, it just possibly might make sense. Five of these turbines are paired with a hydroelectric pumped storage project, so indeed the hybrid can use all the wind (short of Force 10, I suppose) that the turbines receive.
On the other hand, this is a somewhat volcanic island. Would they not be better off with geothermal?


Hey, how did they get that child up there?

This is a size comparison of a 5-year-old child with one of the generator ports that hold the blades of the Enercon E-70 turbine. The axis of the nacelle in this picture would be vertical.
For a bigger image, click here

 

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