Blade Number and Overlap Ratio Efficiency Comparison in Savonius Wind Turbine Prototypes

Abstract

A set of compact Savonius wind turbine prototypes with two and three circular blades, with and without 0.2-overlap ratio, were designed and 3D printed, together with their electrical system, with the purpose to test their performance in terms of rotational speed and generated electrical power. All the results consistently showed that, in general, three-blade turbines with overlap ratio had better performance in contrast to similar turbines without overlap, or in comparison with two-blade turbines with or without overlap. For all turbines with the same number of blades, the overlap ratio showed about 22% better rotational speed performance than their similar without overlap ratio, thus evidencing that a 0.2-overlap ratio makes a difference. Three-blade turbines performed better than two-blade ones when both had or no overlap ratio. Similar conclusions were found consistent in terms of voltage and current outputs (generated electric power). And for the cases with similar performance output, two-blade turbines with an overlap ratio were preferable to three blades without overlap in terms of material saving, manufacturing time, and energy consumption.