What a difference a quarter century makes

NETHERLANDS: Enercon's E-126 7.5MW turbines are the repowering choice of developer RWE Innogy for its part of the Noordoostpolder wind project in the Netherlands.

Just 12 of these models will replace the 50 WindMaster 300kW models comissioned in 1991, boosting project capacity from 15MW to 90MW.

The juxtaposition of old and new gives a good perspective on the lengths, or heights, that the industry has achieved in 26 years. RWE Innogy is one of three partners installing 86 modern turbines, creating a new Noordoostpolder wind farm on the banks of the Ijsselmeer lake, Netherlands. The newly repowered area will be home to 48 Siemens 3MW offshore turbines, and 38 Enercon 7.5MW E-126 turbines - the largest commercially operated onshore turbines.

RWE will remove its 50 WindMaster 300kW turbines once installation of its 12 Enercon E-126 models is complete. The WindMasters' hub height of 30 metres, and rotor diameter of 25 metres, is dwarfed by Enercon's 135-metre hub height and 127-metre rotor.

The foundations, which were completed in April, had to be specially designed for installation on the man-made dyke. Only 0.5 metres is below ground level, so to secure the base, 60 concrete piles were driven into the dike below it. Each foundation is 26.5 metres in diameter and is made up of 180 tones of steel and 1,200 cubic metres of concrete.

The 156-tonne Enercon nacelle was placed on top of the concrete tower, using a lattice-boom crane. Then came the 220-tonne generator and the hub with central rotor section, which weighs 350 tonnes - about the weight of 250 medium-sized cars, said RWE construction manager Rick van Mensvoort.

The rotor, with a diameter of 127 metres, has a swept area of 12,500 square metres - the equivalent of over 1.5 football pitches.

The Noordoostpolder site also includes the Westermeerwind nearshore project, which is using Siemens 3MW turbines.

(pic: Klaas Eissens)

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