1 TWISTED BAMBOO BLADED ROTOR FOR SAVONIUS WIND TURBINES U. K. Saha, P. Mahanta, A. S. Grinspan, P. Suresh Kumar and P. Goswami  Department of Mechanical Engineering, Indian Institute of Technology, Guwahati-781 039, India.  Department of Mechanical Engineering, National Institute of Technology, Rourkela-769 008, India. ABSTRACT Due to low rotational speed and low power production, Savonius rotors are lagging in terms of technology from horizontal axis wind turbines. It is, however, believed that with some design modification of the blades, the Savonius types of machines may be quite useful for small-scale power requirement. Preliminary investigation in this direction led the development of a new blade shape with a twist for the Savonius rotor (Grinspan et al., 2001). The twisted blade fabricated from sheet metals has shown its potential as compared to the other conventional blades. In this investigation, twisted blades fabricated from bamboo strips have been tested to find its operational feasibility. Experiments with bamboo bladed rotor show a slightly lower rotational speed as compared to the earlier tested twisted metallic blades. However, the low cost and the ease of fabrication could make this type of design useful for small-scale power generation in rural areas. INTRODUCTION Savonius rotor is a unique fluid machine that has been studied by numerous investigators since 1920s. It can develop a relatively high torque at low rotational speeds and is cheap to build, but it harnesses only a small fraction of the wind energy incident upon it. It is simple to assemble but requires a lot of material in its construction (Reupke and Probert, 1991). Applications of Savonius rotor, in general, includes pumping water, driving an electrical generator, providing ventilation, and agitating water to keep stock ponds ice-free during the winter (Modi and Fernando, 1989; Ogawa et al. 1989; Sadrul Islam, 1993; Spera, 1994; Mennet, 2004). It is also commonly used as a meter to measure the speed of ocean currents. Various types of blades like semicircular, batch type (Ushiyama et al. 1982; Modi and Roth, 1982), lebost type (Mojola, 1985) etc. have been used in vertical axis wind turbine to extract energy from the air, however, no attempt has so far been made in the vertical axis wind turbine systems to reduce the negative torque, and to increase the starting characteristics, and efficiency with the changes in the air direction (Grinspan et al. 2003; Saha and Rajkumar 2004). The use of deflecting plates (Ushiyama et al. 1982, Huda et al. 1992) and shielding to increase the efficiency has not only made the system structurally complex, but also made it dependent on the air direction. Numerous investigations have been undertaken in the past to study the performance characteristics of two and three bucket rotor. These included wind tunnel experiments, field