Abstract
The characteristics of the wind vertical profile over the coast of Cotonou during wind convective diurnal cycle were explored in this study. Wind data at 10 m above the ground and the radiosonde data in the lower 60 m of the surface boundary layer were used over the period from January 2013 to December 2016. Based on Monin–Obukhov theory, the logarithmic and power laws have allowed characterizing the wind profile. The error estimators of the Root Mean Square Error (RMSE) and the Mean Absolute Error (MAE) were, respectively, evaluated at 0.025; 0.016 (RMSE; MAE) and 0.018; 0.015. At the site of Cotonou, the atmosphere is generally unstable from 09:00 to 18:00 MST and stable for the remainder of the time. The annual mean value of the wind shear coefficient is estimated at 0.20 and that of the ground surface roughness length and friction velocity are, respectively, of 0.007 m, 0.38 m·s−1. A comparative study between the wind extrapolation models and the data was carried out in order to test their reliability on our study site. The result of this is that whatever the time of the year is, only the models proposed (best fitting equation) are always in good agreement with the data unlike the other models evaluated. Finally, from the models suitable for our site, the profile of wind convective diurnal cycle was obtained by extrapolation of the wind data measured at 10 m from the ground. The average wind speed during this cycle is therefore evaluated to 8.07 m·s−1 for August which is the windiest month and to 4.98 m·s−1 for the least windy month (November) at 60 m of the ground. Considering these results, we can so consider that the site of Cotonou coastal could be suitable for the installation of wind turbines.
Highlights
Academic Editor: Enrico Ferrero e characteristics of the wind vertical profile over the coast of Cotonou during wind convective diurnal cycle were explored in this study
E two methods of wind speed extrapolation taking into account both of these parameters and used by [17, 18, 24, 35] are in the first place of the log-linear law which is a similarity model function and secondly the power law. ese two laws have been evaluated in order to choose the best which can suitably reproduce the vertical profile of wind on our study site. ey are presented in Sections 2.2.1.1 and 2.2.1.2
E analysis of Figure 3(a) indicates that the profile is almost mixed up for August and July which are the windiest months in the year. e average wind speeds are, respectively, equal to 7.9 m·s−1 and 7.85 m·s−1 60 m above the ground
Summary
Academic Editor: Enrico Ferrero e characteristics of the wind vertical profile over the coast of Cotonou during wind convective diurnal cycle were explored in this study. E average wind speed during this cycle is evaluated to 8.07 m·s−1 for August which is the windiest month and to 4.98 m·s−1 for the least windy month (November) at 60 m of the ground Considering these results, we can so consider that the site of Cotonou coastal could be suitable for the installation of wind turbines. Ese calculations methods increase the cost of wind projects by often making them economically not viable [5] To cope with this difficulty, there are other simple wind speed extrapolation approaches, based on [6] and applicable only in the surface layer [7,8,9]. Wind data at hub height of a wind turbine is not available except the radiosonde data that are recorded once a day at 10:30 MST by the Agency for Air Navigation Safety in Africa and Madagascar (ASECNA)
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