## 5 Results from BEM Computations  
In order to investigate the influence of MTs on the power of the NREL 5 MW reference wind turbine, BEM computations have been carried out following the steps explained in the previous section. The BEM based computations has now been derived and the power has been computed versus the wind speed. Figure 13 illustrates the power curves along the wind speed for the clean case with no passive device implemented into the blade in comparison with the cases with MTs (see Table 2). The power curves of the wind turbine with MTs follow the trends of the curve of the clean wind turbine. However, at the wind speeds before the rated power is achieved, the power output increases slightly in the cases with the MT implemented, as shown in the enlargement view embedded in Figure 13.  
Additionally, the average wind turbine power output has been calculated for the clean wind turbine and for the cases with MTs at the wind speed realizations described in Section 3. Equation (4) shows how this average power is calculated:  
\[P_{average} = \frac{\sum_{j=1}^{j=Nbins}P(v_{j})\cdot N\left(v_{j}\right)}{\sum_{j =1}^{j=Nbins}N\left(v_{j}\right)} \tag{4}\]  
* \(v_{j}\): is the wind speed according to the realizations shown in Figure 11.
* _Nbins_: number of bins per data. * \(P(v_{j})\): power at the wind speed \(v_{j}\). * \(N(v_{j})\): number of data at the wind speed \(v_{j}\). where the \(P(v_{j})\) has been determined from the data obtained in Figure 13.  
Table 4 shows the results of the power output calculations according to Equation (4). Firstly, the average power has been calculated for the clean wind turbine for the three wind speed realizations illustrated in Figure 11, without any flow control device mounted on the blade. Afterwards, the average wind turbine power was calculated for all cases of MTs distribution described in Table 2 and compared with the clean turbines power values. The symbols denoted by \(\Delta\) represent the increment of average power in comparison with the clean turbine. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & **CLEAN** & **st8** & **\(\Delta\)1** & **st9** & **\(\Delta\)2** & **st8 st9** & **\(\Delta\)3** \\  & & **(W)** & **(W)** & **(\%)** & **(W)** & **(\%)** & **(W)** & **(\%)** \\ \hline \multirow{4}{*}{**NTM7.5**} & Seed 1 & 639,653 & 682,736 & 6.735 & 682,247 & 6.659 & 682,731 & 6.734 \\  & Seed 2 & 498,572 & 543,347 & 8.981 & 542,959 & 8.903 & 543,339 & 8.979 \\  & Seed 3 & 485,570 & 532,180 & 9.599 & 531,780 & 9.517 & 532,154 & 9.594 \\ \hline \multirow{4}{*}{**NTM7.5**} & Seed 1 & 2,043,199 & 2,130,449 & 4.270 & 2,128,954 & 4.197 & 2,130,449 & 4.270 \\  & Seed 2 & 1,712,749 & 1,786,646 & 4.315 & 1,785,376 & 4.240 & 1,786,641 & 4.314 \\  & Seed 3 & 1,665,902 & 1,739,621 & 4.425 & 1,738,406 & 4.352 & 1,739,603 & 4.424 \\ \hline \multirow{4}{*}{**NTM10**} & Seed 1 & 4,053,501 & 4,174,148 & 2.976 & 4,172,666 & 2.940 & 4,174,110 & 2.975 \\  & Seed 2 & 3,565,184 & 3,682,177 & 3.282 & 3,680,524 & 3.235 & 3,682,172 & 3.281 \\ \cline{1-1}  & Seed 3 & 3,417,900 & 3,524,200 & 3.110 & 3,522,500 & 3.060 & 3,523,800 & 3.098 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Average wind turbine power output for the clean wind turbine in comparison with the microtab wind turbine cases. Calculations have been made at three different wind speed realizations, NTM5, NTM7.5 and NTM10. \(\Delta\) means the average power variation with respect to the clean case. Figure 13: Comparison of the power curves of the clean turbine with the cases with the MT implemented. At the wind speed realization of NTM5, the greatest increase in the average power was achieved by the case st8, with a value of \(5.3218\times 10^{5}\) W, which supposes an increase of 9.599% in comparison with the value obtained by the clean wind turbine. Moreover, the other cases with MTs mounted on st9 and st8 st9 present a similar increase.