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diameter. Depending on the site's wind characteristics, tower height is selected to optimize
energy capture with respect to cost. Generally, utility-scale turbines are placed on a tower
60 m to 80 m tall, but 100-m towers are now being used more frequently. Bridge clearances
limit the base diameters of land-based wind turbines.
There are ongoing efforts to develop advanced tower conigurations that are less costly
and more easily transported and installed. The cost impact of extremely large cranes and the
transport premiums for large tower sections and blades are driving the exploration of novel
tower design approaches. Several concepts are under development or being proposed that
would eliminate the need for cranes for very high, heavy lifts [LaNier 2005, Global Energy
Concepts 2001 and 2002]. One concept is the telescoping or self-erecting tower. Other
self-erecting designs include lifting dollies or tower-climbing cranes that use tower-mounted
tracks to lift the nacelle and rotor to the top of the tower.
Operations, Reliability, and Availability
The costs of operations and maintenance (O&M) of wind power plants have also dropped
signiicantly since the 1980s because of improved component designs and increased quality
of manufacture. Wiser and Bollinger [2007] present data showing that current O&M ex-
penses are a signiicant portion of total system cost of energy. O&M costs are reported to
be as high as 3 to 5 cents/kWh for wind power plants constructed with 1980s technology,
whereas the latest generation of turbines has reported O&M costs below 1 cent/kWh. Avail-
ability, deined as the percentage of time during which the equipment is ready to operate on
an annual basis, is now more than 95 percent and is often reported to exceed 98 percent.
Future Advances in Wind Energy Technology
The U.S. Department of Energy (DOE) in conjunction with the American Wind Energy
Association (AWEA), the National Renewable Energy Laboratory (NREL), and the consult-
ing irm of Black & Veatch undertook a study to explore the possibility of producing 20
percent of the nation's electricity by 2030 using wind energy. Their comprehensive report,
titled “20 percent Wind Energy by 2030: Increasing Wind Energy's Contribution to the U.S.
Electricity Supply” [U.S. Department of Energy 2008], describes in detail the many impor-
tant developments needed in the future to achieve this 20 percent goal, including advances
in the following areas:
-
wind turbine technology development
-
manufacturing, materials and resources
-
transmission lines and integration into the U.S. electric system
-
siting and resolution of environmental issues
-
markets for wind-generated power.
The Wind Energy Deployment System model developed at NREL [Short
et al.
2003] was
used to estimate many of the important outcomes associated with producing 20 percent of the
nation's electricity from wind power by 2030. This model of expanding generation capacity
uses data from a wide range of electricity generation technologies, including pulverized coal
plants, combined-cycle natural gas plants, combustion turbine natural gas plants, nuclear
plants, and wind power stations. Estimates of technology development costs, performance
projections, and transmission operation and expansion costs are outputs of this model.
In Europe, the 2008 report
The European Wind Energy Technology Platform for Wind
Energy
envisions that in 2030, wind energy will be a major modern energy source, reliable
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