Abstract
The study presents the local values of wind shear coefficient (WSC) estimated using wind speed measurements made at 20, 30 and 40
m above ground level (AGL) during November 01, 1998 and October 12, 2002. The study also includes the local values of air density calculated using temperature and pressure measurement made at 2
m AGL during the same period. The mean wind speed above 4
m/s and the standard deviation values were used to obtain the turbulence intensities (TI) at different heights. These local values of WSC were used to estimate the wind speed at hub-height of the wind turbines used in this study. Energy yield was calculated for a hypothetical wind form of 60
MW installed capacity assumed to be consisting of 100, 60 and 30 wind turbines of 600, 1000 and 2000
kW from DeWind, respectively.
The study recommends a value of WSC of 0.255 for the estimation of wind at different heights AGL and local air density of 1.06
kg/m
3. The WSC values were found to be higher during nighttime and smaller during daytime while no evident seasonal trend could be identified. In case of air density, no diurnal change was evident but a seasonal trend, with higher values in winter and lower in summer months, was evident. The annual energy yield obtained using wind speed at different hub-heights calculated with WSC=0.255 was found to be 10–20% higher than the yield obtained with wind speeds calculated with WSC=0.143 corresponding to hub-heights of 60 and 100
m, respectively. Similarly, higher plant capacity factors (PCFs) were obtained for energy yield estimated using WSC=0.255 compared to that with WSC=0.143. Higher values of TI were obtained during day time and lower during nighttime. Furthermore, lower values were obtained during November to March and higher during rest of the year. Finally, a decreasing pattern was observed in the values of TIs with increasing height.