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Assessment of Research Needs for Wind Turbine Rotor Materials Technology
wind power plants in California represented a power-generating capacity of 1335 MW, equivalent to a medium-size nuclear or coal-fired power plant. During 1989 the wind power systems of California delivered slightly more than 2 billion kWh of electricity. This amount of electrical energy is equal to the annual residential needs of a city the size of San Francisco or Washington, D.C. In Europe, Denmark has been a pioneer in the use of modern wind turbines for electricity generation. The approximately 2500 wind turbines installed throughout Denmark currently supply about 1 percent of the country's annual electrical needs. We note here that approximately half of the wind turbines installed in California during the 1980s were of Danish manufacture. This is relevant to the longer-term impact of this study as it relates to the future viability of U.S. manufacturers.
The progress of the last decade was not achieved without difficulty and, at times, controversy. Early structural failures, together with under-capitalization of some wind power plant operators, led to the perception, from some quarters, that the California installations were ''tax farms.'' However, as the systems improved in performance and began to produce large amounts of energy, these accusations were replaced by a growing appreciation of the environmental benefits and advantages offered by this renewable power generation technology. The advantages and benefits include the following:
Environmentally Benign: Wind power systems are environmentally benign. There are no gaseous emissions, no particulates, and no radioactive by-products.
Rapid Modular Addition of Capacity: Wind power systems can be installed quickly, thus reducing financing costs and providing flexibility in meeting demand growth.
Wide Range of Capacities: Wind power systems can range in size from very small systems to power plants of utility scale (i.e., from a few kilowatts to hundreds of megawatts in power-generating capacity).
Ease of Integration: Wind power systems are readily integrated into existing utility generation-transmission-distribution systems, using standard utility components and practices. The wind turbine is the only new component.
Couse of Land: While land intensive, wind-driven power plants coexist with other uses of the land on which they are situated. The wind turbine and towers, service roads, and electrical equipment typically occupy only 10 percent of the land on which the wind power plant is installed. Previous uses, typically agricultural, can continue with little useful area removed.
Use of Indigenous Resources: Wind-driven power plants use indigenous resources for their fuel. Since the fuel is without cost, the user country achieves a degree of energy independence and preserves hard currency assets. This is important not only for developed countries with adequate wind resources but perhaps more so for developing countries.
Economically Competitive: The cost of energy (CoE) from wind power plants is competitive now with some conventional energy generation sources. Large-scale systems now being installed deliver energy at costs in the range 7 to 9c/kWh. Under comparable wind resource conditions, third-generation wind turbines (under design now) are expected to deliver energy at costs in the range of 4 to 6c/kWh.
These advantages are applicable not only to this country but globally as well. While not a complete solution to environmental concerns, wind power systems do represent an attractive part of the total generation mix.
As with most technologies, the advantages of wind power systems must be weighed against the disadvantages and limitations. The disadvantages include their visual impact, noise, potential interference with the reception of television signals, and potential hazard to birds. Visual impact is inescapable, particularly at close distances.
The principal sources of noise in wind turbines have been the blades and gearboxes. Early machines were relatively noisy compared with more recent designs. Advances in blade airfoil shape and manufacture have significantly reduced the noise from wind turbine blades. Similarly, attention to the sources of noise in wind turbine gearboxes has resulted in significant reductions. However, with both sources a certain amount of noise is