Variability of Onshore Wind Energy Potential in the 60 m above the Ground under Convective Atmosphere in Southern Benin

The variability of onshore wind energy potential has been investigated over Cotonou coast (Benin) under an unstable atmosphere. Data on the speed and the wind direction at 10 m above the ground recorded every 10 min, have been used over the period from June 2011 to April 2014. The power law based on atmospheric stability was used to determine the vertical wind profile. The Weibull function was used to characterize the frequency distribution of the wind speed and to calculate the wind energy potential. The results indicate that the annual average of the wind speed for a typical day time varies from 3.8 ± 0.40 m.s-1 (10 m) to 7.25 ± 0.58 m.s-1 (60 m) during the convective diurnal cycle. The mean parameters k and c of Weibull were evaluated respectively from 1.65 (December) to 2.21 (August) and from 4.3 (December) to 9.1 m.s-1 (August). The most frequent wind speeds at the study site are between 2.5 ± 0.56 m.s-1 in December to 7 ± 0.24 m.s-1 in August from 10 to 60 m. The average wind speeds giving the maximum energy vary from 6.91 ± 0.56 m.s-1 in December at 10 m to 12.20 ± 0.24 m.s-1 in August at 60 m. Finally, the wind energy potential has been evaluated. As a result, the largest quantity of energy are generally collected between 13:00 UTC and 18:00 UTC. During the months of March, July and August, the daily energy peaks are observed between 14:00 UTC and 18:00 UTC with the values of the order of 650 to 770 W.m-2 at 60 m. The average annual energy potential has been estimated at 130.43 W.m-2 (10 m) and 332.67 W.m-2 (60 m). In view of these results, the site of Cotonou could be suitable for the installation of small and large wind turbines in order to supply the southern Benin with power energy