Height extrapolation of wind data

Technical Report · Mon Nov 01 04:00:00 EST 1982

OSTI ID:6019129

Mikhail, A S

Hourly average data for a period of 1 year from three tall meteorological towers - the Erie tower in Colorado, the Goodnoe Hills tower in Washington and the WKY-TV tower in Oklahoma - were used to analyze the wind shear exponent variabiilty with various parameters such as thermal stability, anemometer level wind speed, projection height and surface roughness. Different proposed models for prediction of height variability of short-term average wind speeds were discussed. Other models that predict the height dependence of Weilbull distribution parameters were tested. The observed power law exponent for all three towers showed strong dependence on the anemometer level wind speed and stability (nighttime and daytime). It also exhibited a high degree of dependence on extrapolation height with respect to anemometer height. These dependences became less severe as the anemometer level wind speeds were increased due to the turbulent mixing of the atmospheric boundary layer. The three models used for Weibull distribution parameter extrapolation were he velocity-dependent power law model (Justus), the velocity, surface roughness, and height-dependent model (Mikhail) and the velocity and surface roughness-dependent model (NASA). The models projected the scale parameter C fairly accurately for the Goodnoe Hills and WKY-TV towers and were less accurate for the Erie tower. However, all models overestimated the C value. The maximum error for the Mikhail model was less than 2% for Goodnoe Hills, 6% for WKY-TV and 28% for Erie. The error associated with the prediction of the shape factor (K) was similar for the NASA, Mikhail and Justus models. It ranged from 20 to 25%. The effect of the misestimation of hub-height distribution parameters (C and K) on average power output is briefly discussed.

• Research Organization: Solar Energy Research Inst., Golden, CO (USA)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 6019129
• Report Number(s): PNL-4367; ON: DE83012974
• Country of Publication: United States
• Language: English

Related Subjects

17 WIND ENERGY
170604* -- Wind Energy Engineering-- Site Characteristics
ANEMOMETERS
COLORADO
EXTRAPOLATION
FEDERAL REGION VI
FEDERAL REGION VIII
FEDERAL REGION X
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
NORTH AMERICA
NUMERICAL SOLUTION
OKLAHOMA
ROUGHNESS
SENSITIVITY ANALYSIS
STABILITY
SURFACE PROPERTIES
USA
WASHINGTON
WIND