Presentation Description: Wind turbine hub heights and blade diameters have been steadily increasing over the last four decades. An analysis of data in the U.S. Wind Turbine Database (USWTB) show an approximate linear increase in average turbine hub height and blade diameter of 2 and 3.2 m/yr, respectively. Average maximum tip height has also been increasing in a near linear fashion at 3.6 m/yr, while the increase in average rotor swept area is quantified using a second-order polynomial. The average hub height and blade diameter in 1983 was 23 and 15 m, respectively, while the average hub height and blade diameter in 2022 is 94 and 133 m, respectively. The highest hub height reported in the USWTB through 2022 is 137 m. Even more dramatic, average rotor swept area was 184 m2 in 1983 and 13,967 m2 in 2022.
60-m meteorological towers are the primary platform of choice for acquiring on-site wind data.. This is due to a variety of factors including cost, ease of installation and no requirement for Federal Aviation Administration (FAA) permits. Taller towers (80 to 100 m) and ground-based remote sensors (sodar and lidar) are being more utilized for on-site observations. However, most project sites overwhelmingly utilize 60-m towers. As a result, extrapolation distances continue to increase between mast height and hub height, and uncertainty in hub height wind speed also increases.
This presentation provides an example for the potential for overestimation of hub height wind speed by examining data from a project comprised of 15 towers (7 x 60 m, 5 x 80 m, 2 x 100 m, 1 x 120 m) and a lidar deployed at two sites. Data from the taller (≥ 80 m) towers and lidar show a consistent decrease in the wind shear exponent with height which is not readily apparent in the examination of data from the 60-m towers alone.
Learning Objectives:
This study emphasizes the need to deploy taller (≥ 80 m) meteorological towers and continue to proportionally increase the deployment of ground-based remote sensors for on-site measurements to reduce uncertainty in hub height wind speed estimates as turbine hub heights and blade diameters continue to increase in size. This is critically important in meteorologically and topographically complex sites where the power law breaks down with height.
