Just how big is massive? The latest wind turbine blades being built for offshore use are gigantic — roughly the total wingspan of an Airbus A380. They are the longest wind turbine blades being built, and here's how they do it.
One new B75 blade from Siemens is approximately 246 feet long with a full rotor assembly stretching roughly 500 feet across.
It boggles the mind — even more so when you learn the blades are cast as one piece. The massive size is to ensure maximum efficiency as an alternative energy source. When spinning, the blades could be turning at approximately 179 mph at the tips; this generates incredible force as air travels over the huge blades.
Siemens estimates that 198 tons of air presses on the blades every second at wind speeds as low as 21 mph; this is how the energy is extracted. So for the B75 to withstand the potential for such great pressure, they eliminate all seams, joints and any other points that could weaken the structural integrity.
This means engineers pour each blade as a single unit into the trough you see above. They're made of glass fiber reinforced epoxy resin and balsa wood. Siemens calls this process IntegralBlade.
It's truly hard to imagine something so big being one large piece, but making the blade in one single, lightweight unit not only improves the structural integrity, it also maximizes the performance of the rotor. The weight is reduced by almost 20 percent, which will lighten the unit's load bearing requirements from the nacelle to the foundation.
The B75 is so big it needs a special truck to carry the first blades from the factory to the test site at Denmark's Østerild Test Station. The truck had to travel the 357-mile journey at roughly 37 mph. In actuality, the distance from the factory to the installation site was only 205 miles, but the enormous truck and blade had to plan a route that could handle its bulk.
The B75 blade has been installed on Siemens' 6-MW turbines. Siemens reports they have a six-megawatt capacity; running at this capacity, an entire farm could produce enough energy to power 1.8 million homes by 2017. If all goes well some 300 of these huge turbines could pop up along the English coast in the future.
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