Research On Effects Of Atmospheric Stability On Wind Resource Characteristics

Atmospheric stability is a key factor affecting wind flow characteristics. Conventional wind energy assessment considers this stability as neutral, neglecting the thermal effects on atmospheric movement. In such way, errors and risks are inevitably brought in wind resource assessing and economic efficiency of project investment. Therefore, this thesis studies the changing rules of wind resource parameters taking atmospheric stability into account, and presents wind speed extrapolating. Main contributions includes:1. Research on atmospheric stability classification methodsThree different atmospheric stability classification methods, including temperature differential method, wind speed-temperature differential method and Monin-Obukhov method, are compared and analyzed. Results show that Monin-Obukhov method has the best performance. This section lays a solid foundation for the following research on influence of atmospheric stability on wind resources.2. Research on wind resource characteristics under different atmospheric stabilitiesTaking 5 years’measured data in Colorado, USA as case study; the level of atmospheric stability is firstly classified using Monin-Obukhov method; six parameters in wind resource assessing (wind profile, wind shear exponent, wind speed distribution, wind roses, wind energy roses and wind power density) are calculated under different atmospheric stabilities; influential rules of above assessing parameters under varying atmospheric stability are analyzed respectively; in this way, a systemic relationship between atmospheric stability and wind resource characteristic parameters is obtained.3. Establishing a wind speed extrapolation model considering atmospheric stabilityBased on the above studies, a hub height wind speed extrapolation model is proposed considering atmospheric stability. This model could differentiate the wind shears under various atmospheric stabilities during wind speed extrapolating, rather than using an average wind shear for the whole wind farm. In such way, much accurate extrapolating hub wind speed in wind resource assessing is employed, and errors in wind resource assessment might decline. Results validate the simplicity, accuracy and practicality of the proposed method.