Savonius, a type of vertical axis wind turbine (VAWT), is applicable for harvesting wind energy in Indonesia, having an average wind speed of 4 -5 m/s. Owning the advantages as suitable for placing in the urban areas as well as reducing the huge electricity load, the Savonius received considerable attention from researchers in making the performance improvement. Therefore, the current research provides an investigation on the effect of adding extra layers on concave blades on the performance of

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... the Savonius wind turbine model. As the novelty, the modification of conventional Savonius turbine has been developed by adding single and multiple layer blades on the tip blade with an overlap ratio (OR) of 10 and 15%. It was tested under wind speeds of 6.46, 6.99, and 7.27 m/s, which generated by the fans blower with a 2x2 configuration. The results show that the addition of multiple layers increased the Savonius power coefficient by 22.4% and 11.2% at OR of 10 and 15%, respectively. The highest power coefficient (Cp) is found at 0.12, which obtained by the Savonius turbine with multiple layers of 90⁰ and OR of 10% configuration. It is concluded that adding the multiple layer blades enhanced the performance of Savonius wind turbines.