Development of a Low Cost Rotor Blade for a H - Darrieus Wind Turbine

Abstract

A three bladed vertical axis wind turbine with a target performance of 500W was designed and fabricated. The material used was Glass fiber reinforced plastics (GFRP). The study focused on Blade design where a numerical optimization process of the design was done to come up with parameters for the rotor blades. The chosen sizing was a rotor diameter of 2m and length of 1.6 m with a chord length of 0.2 m. A NACA 0021 air foil was chosen because of its thickness (21% of chord) and its selfstarting behavior. Blade production process involved making of the master blade to form the mould. The mould was used to make the blade copies that was later laminated, dried, trimmed, and smoothed. The power coefficient was tested using a wind fan with wind speeds ranging from 4 m/s to 15 m/s. A direct drive Axial Flux Permanent Magnet (AFPM) generator with a rated RPM of 280 developed for small scale vertical axis wind turbine (VAWT) was coupled to the turbine rotors to determine the electricity generation capacity. A battery was used to provide the load in the experiment and the synchronized frequency controlled by an inverter. A speed of 14 m/s gave the highest power of 190 W at 280 rpm, 12 m/s gave the highest power as 156 W at 230 rpm, 10 m/s gave the highest power as 120W at 180 rpm while 8 m/s gave the highest power as 96 W at 140 rpm. The turbine torque was 1.56Nm at an RPM of 175. It was noted the turbine has high torque but low rotational speed and with a high gear ratio generator may achieve higher power output. The cost of production of the Rotor blade with all its components was approximately Kshs. 50,000. This cost included buying of the shaft, hubs and bearing totaling to Kshs. 25,000 and the blade production cost Kshs. 21,000. When compared to a HAWT turbine of same sizing cost in the local market the price ranges from KSH 100000 to KSH 200000. Most of the local suppliers do not supply VAWT; the international price of VAWT of same sizing is about US$ 1,000. In conclusion the blade produced in this study is cheaper when compared to locally produced HAWT and VAWT prices in international market.