## 6 Applications
### Small Scale VAWTs  
Small scale VAWTs, referred to rated power below 50 kW, may be considered suitable for installations in coastal regions. The present analysis have been inspired by the work of [PERSON] et al. [55], with the aim of computing the Annual Energy Output (AEO) of two turbines installed in an harbour area under real atmospheric wind conditions. H-shaped and Troposkein architectures with comparable swept area were upscaled maintaining the same aspect ratio (height to radius) of the VAWTs tested at GVPM. For these analyses, wind shear modeling was introduced by assuming a proper wind shear coefficient \(\alpha_{w}\) (see Equation (18)). The wind shear coefficient was selected according to the study of [PERSON] et al. [56]; they conducted a measurement campaign based on 1h-sampled wind data recordings over 6 years, in three coastal locations in Italy (Brindisi, Portscuso and Termini Imerese). Measurements were made at 10 m and 50 m sensor heights above ground level in order to reconstruct the velocity profile and, from this, to derive an averaged wind shear coefficient. The present 3D BEM analysis was performed with a wind shear coefficient equal to 0.271 representative of the 6-year average recorded in Portscuso (Sardinia, Italy). Small scale VAWTs characteristic parameters are reported concisely in Table 6. \begin{table}
\begin{tabular}{l c c c} \hline \hline \multicolumn{1}{c}{**H-Shaped**} & \multicolumn{2}{c}{**Tropsokein**} \\ \hline Blades & 3 & Blades & 3 \\ Blade height & 7.94 m & Blade height & 8.20 m \\ Rotor diameter & 2.8 m & Rotor diameter & 4.10 m \\ Solidity & 0.25 & Solidity & 0.38 \\ Chord & 0.466 m & Chord & 0.466 m \\ Rot. speed & 73.6 rpm & Rot. speed & 73.6 rpm \\ Swept area & 44.45 m\({}^{2}\) & Swept area & 44.34 m\({}^{2}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Small scale ‘Savona’ VAWT geometric parameters. Figure 11: Sensitivity analysis to airfoil shapes: NACA0021 and DU06W200 for the case of micro H-shaped 200 W and Troposkein 800 W rotors. For the present analysis, the same systematic approach used for the micro-scale VAWTs was adopted, considering rated power ranging between 10 and 20 kW ('Small rotors' in Table 6). H-shaped and Tropsokein rotors were upscaled from their original dimensions in Tables 1 and 2 preserving unaltered solidity and \(H/D\) ratio of the original laboratory models. Moreover, rotational speeds and chord lengths were set identical for both upscaled turbine layouts. Figure 12 shows a sensitivity analysis to VAWT hub height and airfoil shape with wind shear in the case of H-shaped and Tropsokein VAWT types. The analysis was made in terms of relative efficiency reduction, defined in Equation (20), which quantifies the difference in \(C_{P}\) with respect to the case with the same airfoil shape and without wind shear. \[\Delta C_{P}=\frac{|C_{P(\alpha_{w},z_{EQ})}-C_{P(\alpha_{w}=0)}|}{C_{P(\alpha _{w}=0)}} \tag{20}\]  
Overall, wind shear effect appears limited when an imposed parabolic wind speed profile is considered, resulting in a reduction of the power coefficient, less than 1% for both H-shaped and Tropsokein architectures. Whereas, when \(z_{EQ}\) ranges from 10 to 20 m, keeping the same wind shear coefficient, the effect on the turbine \(C_{P}\) is more visible: 2.3% power coefficient reduction at optimal TSR is observed for DU06W200, whereas a lower reduction equal to 1.2% for NACA0021. However this trend is not respected at off-peak efficiency points where NACA0021 shows higher performance reduction larger than 2%. The impact of wind shear on VAWTs is lower for the Tropsokein configuration (0.8% \(C_{P}\) loss at optimal TSR, \(\lambda=3.5\)) as the extraction of power is focused on the equatorial section; H-shaped VAWT therefore turns out to be more influenced by the hub location within an atmospheric boundary layer even though the overall effect is mitigated by the tip losses. Figure 13 highlights the enhanced efficiency of DU06W200 for either H-shaped and Tropsokein VAWTs, achieving a higher optimal tip speed ratio over NACA0021.