INTERNATIONAL JOURNAL of RENEWABLE ENERGY RESEARCH R. Hariyanto et al., Vol.6, No.4, 2016 Experimental Study On Improvement The Performance Of Savonius Windmill With Ventilated Blade Rudi Hariyanto*, Sudjito Soeparman**, Denny W**, Mega N S** *Department of Mechanical Engineering, Merdeka University, Malang – Indonesia. Jl. Terusan Raya Dieng 62-64, Malang, Indonesia 65146 **Department of Mechanical Engineering, Brawijaya University, Malang – Indonesia, Jl. MT Haryono 167, Malang, Indonesia 65145 (ui_masrudi@yahoo.com, sudjitospn@yahoo.com, denny_malang2000@yahoo.com, megasasongko@yahoo.com) ‡ Corresponding Author; Rudi Hariyanto, Jl. Bunga Merak 51 RT 08 RW 02 Kec. Lowokwaru Malang Indonesia 65141, Tel: +62-85755612303, ui_masrudi@yahoo.com Received: 27.06.2016 Accepted:24.08.2016 Abstract- This study aims to determine how much influence the use of fixed ventilation on the blade towards improvements in performance Savonius windmill. Ventilation is made in the form of a reflection on the letter C. The ventilation opens into the concave side of the blade. There are one model of the conventional Savonius windmill and six models of the ventilated Savonius windmill that tested in the wind tunnels. Experimental variables are variations for the clearence width of the ventilation, variations for the wind speed and variations for the rotor rotation. The ventilated Savonius windmill have the average power coefficient (Cp) higher than the conventional Savonius windmill. Especially for the clearance width of ventilation is 0.05 of the diameter of the blade, the ventilated Savonius gives the Cp improvement of 132%. Keywords : Savonius windmill , ventilation, the clearance width of ventilation, the useful power, coefficient of performance 1. Introduction Savonius windmill is a vertical axis windmill developed by Sigurd Savonius in 1925 [1]. Savonius windmill has good starting torque even at low wind speeds. The weakness of Savonius is a low efficiency. Efficiency or Cp (power coefficient) of the conventional Savonius windmill is about 15% [2]. Many researchers have tried to improve the efficiency of Savonius windmill. Altan [3] has been testing the use of directional curtain to prevent the negative torque on the blade Savonius. The results showed that Savonius rotor performance can be improved by setting the curtains. The best position of the curtains could increase Cp of Savonius rotor approximately 38.5%. Mohamed et al [4] also were done the research ideas such as Altan. But Mohamed investigated the use of the obstacle plate in front of the convex side of the Savonius blade. The obstacle plate assembled with a different tilt angle. Thus, the obstacle plate is able to reduce the negative moment on the convex side of the blade. The obstacle plate also is able to direct the wind toward the concave side of the Savonius rotor blade. The use of obstacle plate is able to increase the performance of Savonius windmills up to 27%. On the development of further research, Mohamed et al [5] done a study of computational numerical simulations to optimize the geometry of the Savonius turbine with deflector blade. Performance of Savonius windmill increased of at least 30% for 0.3<TSR<1.4. However, Saha and Rajkumar [6] have investigated the use of the twisted blade on Savonius windmill. The results showed the maximum Cp of the twisted blade of 13,99%, and Cp of the semicircular blade showed improvement by 11,04%. But in its application, the new modification of the blade such as the twisted blade is likely to make the shape of the Savonius blade more complicated and difficult to produce it. Likewise, the use of the wind curtains that permanently outside the Savonius rotor is very difficult to apply in the field because the wind coming from any direction, unlike the testing in a wind tunnel. Some researchers were also making efforts to improve efficiency but remain concentrated on the standard shape of the conventional Savonius rotor. Use of overlap between 10% - 30% of the blade diameter was able to increase the efficiency of conventional Savonius rotor by 5% to 20% [7]- [9]. The use of end plates are also able to improve the performance of Savonius rotor [10]-[12]. Research on the effect of aspect ratio on Savonius rotor shows that the best