Derivation of Surface Roughness and Capacity Factor from Wind Shear Characteristics

In this paper, a novel method to derive surface roughness for the location of a wind-turbine facility is explained. Employing measured and projected low altitude (~10-30m) meteorological data, wind shear coefficients are estimated for weather stations in Bangladesh with potential for harnessing wind energy. Diversely located geographical positions are covered from three national sectors on the basis of surveys conducted by the United Nations. Time-series (annual and monthly) variation of wind shear is exploited to produce a forecasting tool for wind profile at commercial turbine heights. Best estimates of average shear factors (in the range of 0.1 to 0.3) are obtained from probability distribution curves and by matching their profiles with forecasted wind curves, roughness length is determined for specific weather points. The findings (varying from 0.05 to 0.5) are used to derive range of obtainable capacity factors (18 to 37%) for medium-scale installed turbines. The proposed method is expected to provide accurate projections of logarithmic wind power law and achievable turbine efficiency in potential wind centers of Bangladesh.

Keywords:

Wind Shear; Profile Coefficient; Surface Roughness; Capacity Factor,

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