Indonesian Journal of Electrical Engineering and Computer Science Vol. 29, No. 2, February 2023, pp. 618~625 ISSN: 2502-4752, DOI: 10.11591/ijeecs.v29.i2.pp618-625  618 Journal homepage: http://ijeecs.iaescore.com An electric power generation improvement for small Savonius wind turbines under low-speed wind Kwanjai Nachaiyaphum, Chonlatee Photong Department of Electrical Engineering, Faculty of Engineering, Mahasarakham University, Kham Riang, Thailand Article Info ABSTRACT Article history: Received Aug 8, 2022 Revised Oct 7, 2022 Accepted Oct 25, 2022 Savonius wind turbines have advantages of self-rotating at low speed wind, high starting torque, and less noise generation. However, they have low electric power generation capacity. This paper presents electric power generation improvement for small Savonius wind turbines when operating at low-speed wind of 1-6 m/s by using optimal Bach-type blades, twist blades and a wind tunnel. The turbine prototypes with the optimum diameter and height of 32 cm were developed with 3 different blade types: conventional semicircular blades, Bach-type blades and twisted 15° blades and a wind tunnel. The experimental results showed that the Savonius wind turbine with Bach-type generated highest electric voltage, which was 19.3% and 7.6% higher compared to conventional blades and twisted 15° blades. The additional wind tunnel could improve electric power generation efficiency by approximately 21.4% compared to the turbines without the tunnels. Keywords: Bach-type blades Power generation improvement Savonius wind turbine Twist blades Wind tunnel This is an open access article under the CC BY-SA license. Corresponding Author: Chonlatee Photong Electrical and Computer Engineering, Faculty of Engineering, Mahasarakham University Kham Riang, Katarawichai, Maha Sarakham, 44150, Thailand Email: chonlatee.p@msu.ac.th 1. INTRODUCTION Most winds that exist near-surface of the earth are inherently in the range of very low-low speed wind of 3-5 m/s, as shown in Figure 1 [1]. Therefore, designing high power conversion wind turbines that effectively convert wind energy to electricity at low wind speed would be a great challenge for researchers. There are several types of wind turbines currently available; some are shown in Figure 2 [2], [3]. It is seen that the wind turbines with high tip speed ratio (λ) would achieve higher power coefficient (Cp) but with a much larger in size. In fact, there is only the Savonius wind turbine type that could operate with the tip speed less than 1.5 well while having small size, by mean of self-rotating, high starting torque [4]-[7] and less noise [8] capacity; but unfortunately with the lowest Cp [9]. Many research publications have been proposed regarding efficiency improvement for the Savonius Wind turbines, which could be summarized in terms of the wind speed range and the investigation part(s) of the turbines as shown in Table 1 [10]-[25]. It could be seen that much research have been done on the blades since 1991 and some implementation on the additional guiding plates or tunnels and others. Bach-type blades and twist blades seem to provide significant efficiency improvement while adding the end plates or guiding plate/tunnel could also improve. However, all the proposed techniques were the results only at medium speed wind (5-11 m/s). In this research, the efficiency when they operate at low-speed wind range of 1-6 m/s is investigated, examined, and evaluated.