Seasonal Variation in the Weibull Parameters from In Situ wind Measurements and Model: A Case Study in the Bay of Bengal

Abstract

Seasonal variation of wind speed (U10) and its distribution are essential for the design of wind energy converters (WEC). In this study, year-round wind speed observations from a deepwater moored buoy at a location in the Bay of Bengal are used to assess the potential for wind power generation and are used to validate the ERA5 model. Model-U10 distribution is confined to low wind speeds with high occurrence in the medium range while observations spread to higher range. Model under-predicted monthly averaged peak winds (9.5–10 m/s) by 1.5 m/s during Southwest monsoon (June and July). Model power is always underpredicted. The peak power density during both SW (July, 667 W/m²) and NE monsoons (November, 405 W/m²) is under-predicted by 36%. The model performed well during the calm period (March) and the minimum deviation during pre (April) and post (September) monsoon are 12% and 16% respectively. The maximum deviations observed during NE (October) and SW (June) monsoon are 60% and 42% respectively. This study reveals that observations are essential to validate the model. The power density is fitted and expressed as a second order polynomial of U10. The U10 variations are expressed in terms of Weibull shape and scale parameters, which are calculated by graphical Least Squares Fit method. The monthly variation of Weibull scale parameter closely matches with average wind speed. Based on the shape parameter value, the nature of the wind and its stability during different seasons are classified for buoy-U10 and model-U10 and the deviations in the model are detailed.