11 Being drag machines, Savonius rotors have lower power coefficient. However, some
experimental rotors have shown power coefficient up to 35 percent. These rotors have high solidity and thus high starting torque. They work at low tip speed ratios, with the maximum
of about one. They have simple construction and it even can be made from oil barrels cut in two halves lengthwise. Hence they are preferred for high torque-low speed applications like
water pumping.
Figure 2.5 Principle of Savonius RotorSathyajith 2006
2.2.3.3. Advantages of Savonius Wind Turbine
Savonius wind turbine has some advantages as follow: 1.
Due to the relative simplicity of the turbine assembly, this type of turbine can be constructed simply without complex fabrication and cost effectively.
2. Similarly because of the relative simplicity of the design. Savonius wind turbines are
reliable and less prone to damage. This is also due to the relative solidity of the design. 3.
Being a drag type, the Savonius turbine has a high starting torque and hence can self- starting even in low wind speeds.
4. Like all VAWT, Savonius turbines are able to receive wind from any directions. And
being drag type, they are less affected by air turbulence.
2.2.3.4. Method to Improve Savonius Wind Turbine Performance
There are argumentations to improve Savonius wind turbine performance that explained in some past literatures.
1. Deflector Plate
As one way to improve Savonius wind turbine efficiency, deflector plate is plates that placed in front of the Savonius rotor in order to prevent negative torque and directing
wind onto concave blade Altan, Atılgan et al. 2008; Mohamed and Thévenin 2010.
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12 Figure 2.6 Deflector Plate
Altan, Atılgan et al. 2008
2. Double Steps Savonius Wind Turbine
Applying a double-step Savonius wind turbine, where two or three wind turbine designed to row in pairs horizontally that are set at 90° for the double steep one and 120° for three
steps one. The double steps Savonius wind turbine found better in self-starting comparing to the standard Savonius wind turbine single wind turbineHayashi, Li et al. ; Mohamed 2011.
Figure 2.7 Double-step Savonius Wind Turbine
3. Twisted Blade Savonius Wind Turbine
Twisted-blade Savonius wind turbine was investigated to improve its efficiency. Based on performance analysis has been done on the starting characteristic, static torque and rotation
speed. The result shows that the twisted-blade Savonius wind turbine has potential values due to its smooth running, high efficiency and the self-starting ability is better than conventional
or standard Savonius wind turbineMohamed 2011; Damak, Driss et al. 2013. perpustakaan.uns.ac.id
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13 Figure 2.8 Twisted Savonius Wind Turbine
4. Modified Savonius Wind Turbine Parameter
Various Savonius rotor parameters were studied to understand the effect of various parameters toward efficiency of Savonius wind turbine performance. Manipulation of
parameters were done determine efficiency and to know the best condition of Savonius rotor performance such as the effect of end plates, aspect ratio, number buckets, the influence of
bucket spacing and overlap, the influence of Reynold ‟s number and turbulence intensity, the
influence of stator Akwa, Vielmo et al. 2012; Mahmoud, El-Haroun et al. 2012. perpustakaan.uns.ac.id
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14 Figure 2.9 Modification of Savonius Wind Turbine ParameterAkwa, Vielmo et al. 2012
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15
5. Guide Vane
