2.2.2. Savonius Turbine

Because of the above-discussed wind behavior, our ROSEO-BIWT's Savonius axis is positioned horizontally along the superior edge of the building. There have been several recent studies on the performance of the Savonius turbine. Mohamed et al. [42] improved the performance using plates to eliminate the negative torque in the returning blade. They carried out tests for a two-bladed and a three-bladed wind turbine, and, in both cases, they improved the power coefficient ( *Cp*) of the wind turbine by up to 27%, with 15% being the typical value.

Apart from these intrinsic improvements, some engineers have developed the mentioned PAGV systems to accelerate air streams. Shikha et al. [43] increased the wind speed by 3.7 times in an experiment using a specific well-studied nozzle. Additionally, Altan et al. [44] studied the influence of the inclination angle of the plates as well as their length. In these experiments, they found that, when the longitude of the PAGV increased, the power also increased. Thus, the important consideration in their study was the relationship between the diameter of the rotor and the length of the PAGV. They even obtained a *Cp* of 38.5%. Other types of PAGVs, referred to as omnidirectional, reached a *Cp* of 48%, implying an increase of 240% relative to a Savonius rotor without a PAGV system.

In terms of longitude and diameter, the Savonius rotor studied in [45] performed best with an aspect ratio of 6:1. Similarly, Park et al. [19] tested different kinds of Savonius rotors, and they discovered that the best design was a six-bladed rotor. Therefore, for our purpose, a similar rotor with these proportions was chosen for the initial test period.
