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The world’s largest wind turbine – until 2011 -- is the Enercon E-126. This turbine has a rotor diameter of 126 meters (413 feet). The E-126 is a more sophisticated version of the E-112, formerly the world’s largest wind turbine and rated at 6 megawatts. This new turbine is officially rated at six megawatts too, but will most likely produce seven-plus megawatts (or 20 million kilowatt hours per year). That’s enough to power about 5,000 households of four in Europe. A quick US calculation would be 938 kwh per home per month, 12 months, that’s 11,256 kwh per year per house. That’s 1776 American homes on one wind turbine. The turbine is installed in Emden, Germany, where manufacturer Enercon will test several types of storage systems in combination with the multi-megawatt wind turbines.
These turbines are equipped with a number of new features: an optimized blade design with a spoiler extending down to the hub, and a pre-cast concrete base. Due to the elevated hub height and the new blade profile, the performance of the E-126 is expected to by far surpass that of the E-112.
WiredForStereo explains the operation of these new turbines: [The E-126]… has no gearbox attaching the turbine blades to the generator, in fact, the generator is housed just at the widest part of the nose cone, it takes up the entire width of the nacelle to generate power more efficiently, and provide longer service life with less wear.
Also like small turbines, these have inverters instead of synchronous generators, that is to say, a separate controller that converts the wild AC generated into something the grid can use. This means the rotor can run at more optimum and varied speeds.
Again like small turbines, this one does not shut right off at a predetermined speed due to gusts or just very high wind speeds. It simply throttles down by turning the blades slightly away from the wind so as to continue to generate power though at a lower production rate. Then the instant the wind is more favorable, it starts back up again. Many smaller wind turbines do something similar except have no blade pitch control, they use a technique called something like “side furling” where the whole machine, excepting the tail, turns “sideways” to catch less wind but continue operating.
Money, why else? Big things are cheaper per unit production. If you have 3 2 MW generators, you have to have three (at least) cranes to put them up, build three foundations, have to maintain three machines, and have three times the parts to fail. If you have one, it is larger and more expensive in itself to move, but not as expensive as having to move three smaller ones.
Sometime in 2011, the Enercon E126 will be overtaken by an even larger machine in Scandanavia. Norway is currently (as of February 2010) working on building the world’s largest wind turbine, a towering 10 MW machine that will blow away the competition. The Norwegian company Sway will build the 533-feet high machine, capable of powering 2,000 homes. Enova, a public agency owned by Norway’s petroleum and oil industry ministry, is helping fund the project, which is expected to cost $67.5 million to build. The power gain comes from reducing the weight and number of moving parts in the turbine--it uses a gearless generator system. Unlike most offshore wind projects where turbines rest on the seafloor, Sway turbines float. This means further offshore development where winds are stronger and more consistent. The floating tower is a pole filled with ballast beneath the water creating low center of gravity. Anchored to the seabed with a single pipe and a suction anchor, it can tilt 5-8°, and turn around with the wind.
Read about giant wind turbines in the book:
Large Wind Turbines
Read about wind energy in the book:
Wind Energy: The Facts