Research on fitting method of wind shear exponent in wind farm

Abstract

Wind shear exponent plays a significant part in the assessment of wind resources and load calculation in wind turbine design. Accurate evaluation of wind shear distribution lays a solid foundation for series of works on the early stage of wind farm development. However, it is challenging to precisely fit the wind shear exponent, especially its distribution, since it is variable with time, location, roughness, height, atmospheric stability, etc. In this paper, a new method for modeling wind shear exponent is proposed considering separate wind speed range. Moreover, for the sake of practical application, the calculation method for wind shear is presented by projection from measurement height to hub height. First, the variation laws of wind shear exponent with different time scale, height and spatial scale are revealed based on measured data from a wind farm installing two met masts. And then, the appropriate mathematical model is established to fit the temporal-spatial distribution discipline in a wind farm. To take a wind farm as example, the proposed model is validated by cross verification of two met masts. The results show that the wind shear exponent at one met mast can be projected by the links with wind shear distribution at other masts. The proposed method provides more accurate way for data interpolation of met mast data, wind resource assessment and wind turbine load calculation.