Environmental Engineering Reference
In-Depth Information
to using the tower as a hoisting device to platforms which climbed
along the tower to put the nacelle and blades on top of it.
Considerable improvements were achieved by applying fibre
reinforced plastics in the blade structures and by new electrical
conversion systems, incorporating power electronics. During the
biannual executive committee meetings of the IEA Wind Energy
Programme country representatives reported about progress of
the realisation of the largest turbines ever built at that time.
The largest among the giants of that time was the German
GROWIAN turbine with a rotor diameter of 100.4 m and an installed
generator capacity of 3 MW. It felt like a race for the first-man-
on-the-moon.
Finite element methods (FEM), although not as refined as
today's, were used to more critically design the sensitive com-
ponents of the wind turbines, notably the hub structures. The design
base for comprehensive design methods was far from complete.
In aerodynamics proper modelling of stall, three-dimensional
efects, aero-elastic phenomena, etc. were missing or were
inaccurate. The same applied to wind field descriptions in the rotor
plane, the efects of turbulence on performance and loading and
wake modelling and wake interaction.
At ECN, one of the experimental turbines, the relatively small
but versatile two bladed 25mHAT made its first rotation on the first
of March 1981. The wind turbine, which later became the turbine
with the longest operational lifetime among the experimental
machines in the world (1981-1995), had a variable rotation DC
generator with static inverter, by which the load characteristics
of various electrical conversion systems could be simulated.
The versatility of the facility appeared from the experiments which
were carried out for various national and European research
programs:
• Verification of various control strategies
• Boundary layer measurements
• Determination of the radar cross-section
• Determination of acoustic noise emission as a function of
blade section by means of an acoustic telescope
• Duration test of the operation of tip brakes of Stork blades
• Testing of the FLEXTEETER concept (Figs. 2.2 and 2.3)
• Field testing of blades with 150 pressure holes and sensors as
part of an IEA Annex.
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