Worldwide, there are 10 to 12 manufacturers of large, utility-scale systems, marketing 200kW to 3.0 MW systems of various configurations, including three-bladed machines with full-span pitch control and two-bladed, stall control machines with teetering hubs. News on these developments is available from the major industry magazine, The Windpower Monthly.
The more advanced configurations (from an aerodynamic standpoint at least) have been developed under the U.S. Department of Energy Advanced Turbine Program.
European manufacturers like Tacke, Micon, Vestas, and Enercon (at left) have commercialized turbines with more conventional rotors, but featuring such important innovations as low speed generators and complete variable speed systems incorporating advanced power electronics. Recently, GE Energy (which purchased the wind division of defunct Enron) has adopted the European design philosophy in the U.S., with its merger of the technical expertise of Zond and Tacke.
One of the latest innovations being investigated in the U.S. and Europe is the addition of a hinge at the nacelle-tower attachment, allowing the turbine to "nod" up and down in response to turbulence and wind shear (the difference in wind speed at the top and bottom of the rotor disk). This configuration has been tested at Riso and promises substantial reductions in rotor and drive-train loads and in control system costs. A model intended for commercial development operated in California for several years and has been investigated by the National Wind Technology Center. However, such innovations may not be necessary for wind to meet its cost goals for several years.
The result of recent mergers is that, in 2001, there is a virtual internationalization of the wind turbine industry and research community. As recent as 1995, pundits like Paul Gipe could claim that the Europeans' use of smaller machines with conventional aircraft airfoils meant that low tech had beaten high tech in the wind business. In 2001, with European wind turbine power ratings pushing 2 megawatts, Denmark's Riso Laboratories touting its new wind turbine airfoil designs (modeled closely after pioneering activities in the U.S.), and the U.S. company Enron marketing machines from both the U.S. and Europe, there is really very little difference between European and U.S. technology. The last remaining major area of controversy is the issue of two versus three blades for large wind turbines. Theoretically, a two-bladed machine should be less expensive and more efficient than a three-bladed one. But considerable refinements are still needed to offset the greater stability and lower per-blade loads of three-bladed designs. And the optical illusion of speed fluctuations and out-of-plane rotation associated with two-bladed machines makes them less attractive to some onlookers. Time will tell if one design will win out or if both will be able to exist in specific applications.
In the near future, wind energy will be the most cost effective source of electrical power. In fact, a good case can be made for saying that it already has achieved this status. The actual life cycle cost of fossil fuels (from mining and extraction to transport to use technology to environmental impact to political costs and impacts, etc.) is not really known, but it is certainly far more than the current wholesale rates. The eventual depletion of these energy sources will entail rapid escalations in price which -- averaged over the brief period of their use -- will result in postponed actual costs that would be unacceptable by present standards. And this doesn't even consider the environmental and political costs of fossil fuels use that are silently and not-so-silently mounting every day.
The major technology developments enabling wind power commercialization have already been made. There will be infinite refinements and improvements, of course. One can guess (based on experience with other technologies) that the eventual push to full commercialization and deployment of the technology will happen in a manner that no one can imagine today. There will be a "weather change" in the marketplace, or a "killer application" somewhere that will put several key companies or financial organizations in a position to profit. They will take advantage of public interest, the political and economic climate, and emotional or marketing factors to position wind energy technology (developed in a long lineage from the Chinese and the Persians to the present wind energy researchers and developers) for its next round of development. http://mobile123-mobile.blogspot.com/
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