Abstract
Savonius rotors are large and heavy because they use drag force for propulsion. This leads to a larger investment in comparison to horizontal axis wind turbine (HAWT) rotors using lift forces. A simple construction of the Savonius rotor is preferred to reduce the production effort. Therefore, it is proposed here to use single-segment rotors of high elongation. Nevertheless, this rotor type must be compared with a multi-segment rotor to prove that the simplification does not deteriorate the effectiveness. The number of segments affects the aerodynamic performance of the rotor, however, the results shown in the literature are inconsistent. The paper presents a new observation that the relation between the effectiveness of single- and multi-segment rotors depends on the wind velocity. A single-segment rotor becomes significantly more effective than a four-segment rotor at low wind speeds. At high wind speeds, the effectiveness of both rotors becomes similar.
Highlights
In the large turbine market, the design concept has converged over several decades to a horizontal axis wind turbine (HAWT) equipped with a three-bladed rotor
In the case of vertical axis wind turbines (VAWT) driven by drag force (Figure 2), the blades on one side of the rotor axis are moving against the wind, reducing the generated power
The most important conclusion, new for the knowledge of Savonius rotors, is that the difference in power production between single- and four-segment rotors depends on the wind velocity; The difference between these rotors increases with reduced wind velocities; A single-segment rotor is more effective than a four-segment one; 4
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. In the case of vertical axis wind turbines (VAWT) driven by drag force (Figure 2), the blades on one side of the rotor axis are moving against the wind, reducing the generated power. Due to this feature, the energy production by VAWT is expected to be smaller than by HAWT. In the drag force-driven turbines, high aerodynamic forces are induced by strong winds due to the large area covered by blades. It is shown that the single segment rotor is more effective at low wind velocities, which is an important practical conclusion of the presented results
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