For offshore wind farms to become an economically feasible alternative energy source, each turbine needs to be big. Like, really big. That's why the latest turbine blade from Siemens is gigantic — just a hair shorter than the wingspan of an Airbus 380.
The B75 turbine blade itself is 75 metres long, while the entire rotor assembly measures 154 metres in diameter. As it spins, the blades cover an area of 18,600 square metres — that's roughly two and a half soccer fields — at a brisk 80 metres per second, or 290km/h at the tips.
Moving that fast over such a large area generates a tremendous amount of force. About 180 tonnes of air press on the blade every second with wind speeds of just 35km/h. To build a blade that can withstand it, Siemens pours each blade as a single unit of glass fibre-reinforced epoxy resin and balsa wood. This process, called IntegralBlade, eliminates seams, joints and other structural weak points while maximising the rotor's performance. The process also reduces weight by as much as 20 per cent, which lightens the system's load bearing requirements — from the nacelle down to the foundation.
The B75 blade is currently being installed on Siemens' 6-MW turbines, which are going up in Denmark's Østerild Test Station. Running at capacity, the entire farm could produce enough energy to power 1.8 million homes by 2017. If the tests are successful, Danish energy giant Dong plans to install 300 of these new turbines along the English coast within the next few years. [PHysOrg - Siemens - Discover Siemens - Green Car Congress]