The 2015 JKUAT Scientific Conference Water, Energy, Environment and Climate 267 DEVELOPMENT OF A SMALL WIND TURBINE ADOPTING FOLDED-PLATE BLADES -PERFORMANCE OF BLADES WITH ONE AND TWO STRAIGHT FOLDING LINES- C. Saoke 1 , Y. Nishizawa 2 , I. Ushiyama 2 , J. N. Kamau 1 , Y. Nakajo 2 and R. Kinyua 1 1 Jomo Kenyatta University of Agriculture and Technology, Nairobi-Kenya 2 Ashikaga Institute of Technology, Japan Email: nishizawa.yoshifumi@v90.ashitech.ac.jp Abstract The authors have developed a simplified folded-plate blade with high power coefficient for small wind turbine on the design concept of the “Appropriate Technology (AT)”. In this study, the shapes of the blades are the tapered type, the straight type and the inversely tapered type and the diameter of all experimental model is 600[mm], the number of blades is 5, and the thickness of plate is 2[mm]. Each blade has a single folding line. The folding angles for these three types of the blades are 10, 20 and 30[deg] respectively. Blade pitch angles can be changed manually at 0, 5, 10 15, 20 and 25[deg]. In the experiment of all rotors, the wind speed in the wind tunnel is set at 10[m/s] and the torque and the corresponding rotational speed were measured gradually increasing the load. From the results of the experiment, the power coefficient Cp and the tip speed ratio λ were calculated to obtain the power characteristics for different blade types. As a result, the maximum power coefficient for tapered type is Cpmax=0.278 when folded angle is 30[deg] and blade pitch angle is 10[deg]. For the straight type, Cpmax=0.303 when folded angle is 30[deg] and blade pitch angle is 15[deg]. And inversely tapered type is Cpmax=0.337 when folded angle is 30[deg] and blade pitch angle is 15[deg]. The most efficient model was inversely tapered type. Additionally, for the inversely tapered type blades, we examined the performance of them with two straight folding lines whose angles are selected from 5, 10, 15 and 20[deg]. Blade pitch angles are also changed at 0, 5, 10, 15, 20 and 25[deg]. The result shows the maximum power coefficient is 0.372 when two folded lines whose angle are 5[deg], 10[deg] parallel the forward edge with blade pitch angle of 20[deg]. Key words: Curved plate blade, coefficient of power (Cp), tip speed ratio, bending and pitch angle, P.I.V. system 1.0 Introduction The world population is expected to grow some 9 billion around the year 2050 (Yoshifumi et al., 2013). Such a rapid expansion of the population will bring increase in demand for food, water, energy and pollution of the environment. Therefore, a priority issue for 21 st century is to assure enough energy and water in the developing countries needed for increasing agricultural output. Development of wind power equipments will be essential in achieving these power needs. This will require the use of appropriate technology to reduce cost and localize manufacture to developing countries because such technologies are perfectly applicable to the individual conditions of the people of a particular region. The main advantage of appropriate technology is that it emphasizes on; simple design using indigenous materials at low cost while operation and maintenance are practiced by local people (Yoshifumi et al., 2013). Wind energy converters that have been built over the years can be divided into two categories: the lift machines and the drag machines. Some drag based machines such as the savonius rotor may achieve maximum power coefficient of greater that 0.2 and may have tip ratios greater that 1.0, this is primarily due to the lift developed when the rotor surfaces turn out f the wind as the rotor rotates (Wilson et al., 1976). The choice of the airfoil, chord length and the twist along the blade determine the performance of the blade. The approach to the choice of the airfoil, chord length and twist along the blade has changed over the years (Snel, 2002). When planning to generate electricity using wind turbine, combination of wind turbines and generators to use will depend on the wind conditions, topological conditions and the energy needs of the site. Furthermore, the technological level of the region, the available type of windmills or wind turbines, and even the practices and traditions of the local people could affect the design. Since power is directly proportional to the rotor area, large wind turbines have recently become so common. This however has had a consequence on the weight of the turbine and the overall cost which increases proportionately. Technological innovation is crucial in the development of low cost and smile