## 4 Conclusions  
Two types of blades were compared for the application in the vertical axis carousel wind rotor. These were blades with the single and dual coherent cross-sections. Real-scale physical models of both blades type were made and experimentally tested in the aerodynamic wind tunnel. To validate the results, at the same time, two-dimensional discrete models of blades cross-sections were prepared. The CFD numerical analysis was then performed considering the same cases and boundary conditions that were accepted in experiments.  
The obtained results of aerodynamic forces and aerodynamic torques were first compared by considering a single blade. Based on the obtained results, it was concluded, that the dual coherent blade provided more advantageous, higher aerodynamic drag \(P_{x}\) when moving downwind, and also more advantageous, lower lift force \(P_{y}\) when moving upwind. The aerodynamic torque \(M_{xy}\) was also concluded to have a minor effect on the total torque, which was generated by the aerodynamic forces acting on the corresponding rotor radii.  
However, the design of a vertical axis carousel wind rotor assumes that there are at least three identical blades in the system. Therefore, in the last step of the comparison, the total starting torque \(M_{\rm{III}}(\alpha_{s})\) was calculated for the example of the vertical axis carousel wind rotors with three SC and DC blades in the system.  
It was concluded, that for the above configurations, the rotor with three SC blades can generate slightly higher maximum starting torque than the rotor with three DC blades, but at the same time, a greater variation of starting torque as a function of wind angle is observed for SC blades. The rotor with three DC blades involved mainly the drag force in contrast to the rotor with three SC blades, which also involved the lift force to a greater extent. Despite the rotor with DC blades obtained greater values of the drag forces on the blades, the rotor with SC blades obtained a greater starting torque.  
Figure 21: The propelling torque for the wind direction \(W\) depending on the blade position \(\alpha\)(\(\alpha\)s) for: (**a**) the SC blade; (**b**) the DC blade.  
The obtained results can be useful in designing vertical axis carrousel wind rotors with self-adjusting system. The findings presented in the article may be particularly useful in related research aimed at optimizing the shape of vertical axis wind turbine blades. Further research on designing and comparing blade geometries dedicated to a vertical axis carousel wind rotor will address the optimization of cross-sectional dimensions to achieve higher and more uniform total torque as a function of the number of rotor blades.  
Conceptualization, M.A. and F.L.; methodology, M.A. and F.L.; software, F.L.; validation, M.A. and F.L.; formal analysis, M.A.; investigation, M.A.; data curation, M.A. and F.L.; writing--original draft preparation, M.A. and F.L.; writing--review and editing, M.A. and F.L.; visualization, M.A. and F.L.; supervision, M.A.; All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
Data Availability Statement: Data is contained within the article.  
The authors declare no conflict of interest.