# Can LiDARs Replace Meteorological Masts in Wind Energy?
## 4 Wind Resource, Power and Load Comparison  
In this section, measured data from the sonic anemometer and that from the profiling LiDAR are used to evaluate the wind resource and wind power potential of the site. The velocity and power distribution obtained from the LiDAR measurement are compared against those obtained from the sonic anemometer measurement. The NREL-5 MW wind turbine is used as a reference to estimate and compare the power production potential of the site. Finally the section compares fatigue load for the NREL-5 MW wind turbine estimated using aeroelastic simulations with the wind speed and turbulence intensity distribution of the sonic anemometer and the LiDAR measurements. The aeroelastic simulations were performed using OpenFAST. Figure 16 summarizes the 10-min average wind speed distribution measured by the sonic anemometer and the profiling LiDAR at 57 m height. Figure 16a shows the distribution of the frequency of occurrence of \(\overline{V}\) in each bin with a bin interval of 1 m/s. One can appreciate that both the LiDAR and the sonic anemometer show a similar trend. However, for lower wind speeds (\(\overline{V}<5\;\;\mathrm{m/s}\)), the frequency of occurrence for the LiDAR measurement is lower than that for the sonic anemometer measurement. In particular, for \(\overline{V}=2\;\;\mathrm{m/s}\), the frequency of occurrence for the LiDAR measurement is lower than that for the sonic anemometer measurement. In particular, for \(\overline{V}=2\;\;\mathrm{m/s}\), the frequency of occurrence for the LiDAR measurement is lower than that for the sonic anemometer measurement. In particular, for \(\overline{V}=2\;\;\mathrm{m/s}\), the frequency of occurrence for the LiDAR measurement is lower than that for the sonic anemometer measurement. Figure 15: Comparison of measurements at 57 m height. (**a**) 10-min average horizontal wind speed for wind direction between 60\({}^{\circ}\) and 180\({}^{\circ}\) (non-complex terrain); (**b**) 10-min average horizontal wind speed for wind direction between 270\({}^{\circ}\) and 330\({}^{\circ}\) (moderately complex terrain); (**c**) Standard deviation for wind direction between 60\({}^{\circ}\) and 180\({}^{\circ}\); (**d**) Standard deviation for wind direction between 270\({}^{\circ}\) and 330\({}^{\circ}\). sonic anemometer is 18% compared to about 16% for the LiDAR. This is possibly because LiDAR measurements are prone to lower carrier-to-noise ratio (CNR) values and larger error when the wind speed is low. Measurements with such low CNR values are filtered out from the current analysis, hence the lower frequency of occurrence for the LiDAR measurement. For higher wind speeds, i.e., \(\overline{V}\geq 5\) m/s, the frequency of occurrence for the LiDAR measurement is slightly higher (higher by less than 1%) than that of the sonic anemometer measurement. These tendencies are also reflected in the Weibull probability density function (PDF) in Figure 16b. The Weibull PDF (\(p(\overline{V})\)) is given by:  
\[p(\overline{V})=\left(\frac{k}{c}\right)\left(\frac{\overline{V}}{c}\right)^{ k-1}\ \ \exp\ \left[-\left(\frac{\overline{V}}{c}\right)^{k}\right], \tag{8}\]  
where \(k\) and \(c\) are the shape and the scale factors respectively. The Weibull PDFs in the figure are obtained by fitting the above function to the measured data for these two parameters. For the distribution obtained from the sonic anemometer data, \(k=1.5\) and \(c=4.87\), while for the distribution obtained from the LiDAR data, \(k=1.53\) and \(c=5.40\). These differences in the Weibull parameters between the sonic anemometer and the profiling LiDAR are not very significant. The annual average wind speed obtained from the sonic anemometer measurement is 4.41 m/s, while that obtained from the LiDAR measurement is 4.79 m/s. Therefore, for the current site, the LiDAR overestimated the wind speed by 0.38 m/s, i.e., by about 8%. Note that the annual wind speed of 4.4 m/s is too low for the site to be considered for wind energy development.