2 Mar 2013
When it comes to wind turbines, size matters. Besides air density and wind speed, the most important factor affecting energy yield is the rotor's swept area, where wind flows over the rotor blades. That's why Siemens has built the B75, a record-breaking 75 metre blade. When three of them are combined with a new 6MW turbine, these fibreglass giants will--when the wind blows at the right speed--generate around 65% more energy than Siemens' previous best models.Weight is crucial--lighter blades allow for less bulk elsewhere in the structure, reducing infrastructure costs. So Siemens' engineers devised a new manufacturing process called IntegralBlade, in which glass-fibre-reinforced epoxy and balsa wood are poured into a single mould, eliminating the need for adhesives or overlapping materials. Cast in one piece, with no weight-adding seams or joints, each blade weighs 25 tonnes--up to 20% lighter than conventional fibreglass blades.
Last summer three B75 blades were transported 320km from Esbjerg, Denmark, to Siemens' offshore test site at Osterild, where their rotations will, when the four-metre-wide hub is included, cover a swept area of 18,600 m²--that's the equivalent of two-and-a-half football pitches, or the wingspan of two Airbus A380s. Scaling up green energy? We're big fans.
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