Wind Shear Characteristics at Central Plains Tall Towers
The object of this study is to analyze wind shear characteristics at tall tower sites in the Central Plains of the United States. The hub heights of modern turbines used for wind farm projects are now 70 meters (m) to 100 m above ground and some advanced turbines under development for deployment during the second half of this decade are rated at 2-5 megawatts of energy generation with rotor diameters near 100 m and hub heights of 100-120 m. These advanced turbines will take advantage of the higher wind speeds aloft to generate more wind energy. Specific knowledge of important wind shear characteristics near and at turbine hub height is needed to optimize turbine design and wind farm layout. Unfortunately, wind speed shear measurements at heights of 80-120 m were virtually nonexistent a few years ago and are still quite uncommon today. The Central Plains is a prime wind energy development region and knowledge about the wind shear characteristics will reduce uncertainty about the resource and enhance wind farm design. Previous analyses of tall tower data (Schwartz and Elliott, 2005) concentrated on data from specific states. The wind energy community has recognized the need to fill the gap of direct wind speed measurements at levels 70 m and higher above the ground. Programs instituted during the last 5 years at the state level and supported by the U.S. Department of Energy's (DOE) State Energy Program initiative have placed anemometers and vanes at several levels on existing tall (70 m+) communication towers. The Central Plains has a fairly high concentration of tall tower sites. The distribution of tall tower sites varies among the states in the Central Plains, because the tall tower program is new and the available state and federal funding to establish tall towers is variable. Our wind resource assessment group at DOE's National Renewable Energy Laboratory (NREL) has obtained much of these necessary measurement data from both individual state sources and regional organizations. Most of the data are available to the public, though data from one tower in Colorado are proprietary. We have begun to analyze important wind climate parameters, including wind shear from the tall towers. A total of 13 tall towers were used for this study. Eleven of the towers had the highest anemometer level between 100 m and 113 m. Two towers had the highest measurement level between 70 m and 85 m above ground. The distribution of the towers among the states is: two sites in Texas and Oklahoma; six sites in Kansas; and one site each in Colorado, South Dakota, and North Dakota. Figure 1 shows the locations and names of the thirteen towers. The wind resource at these sites can be classified as ranging from good-to-excellent. Eight tall tower sites have Class 3 resource, four sites have Class 4 resource, and one has Class 5 resource at 50 m.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC36-99-GO10337
- OSTI ID:
- 943373
- Resource Relation:
- Conference: (Proceedings of) Windpower 2006 Conference and Exhibition (CD-ROM, Technical Track), 4-7 June 2006, Pittsburgh, Pennsylvania; Related Information: For preprint version see NREL/CP-500-40019
- Country of Publication:
- United States
- Language:
- English
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