Abstract:
Optimizing a blade for a small wind turbine to achieve a quick starting time at the loss of minimal power output is one of the most challenging aspects of design. This study considers a micro-wind turbine for experimental analysis to validate an optimized blade design based on blade element momentum theory and its performance analysis conducted numerically. The focus of the experiment was to improve the starting time considering different weight factors. 30 % power coefficient and 70 % starting time were considered during design. A scaled-down rotor of three blades optimized for both quick starting time and optimum power was manufactured by 3D printing. Polylactic Acid (PLA) was selected as a printing material to keep inertia equivalent to blades of the procured generator. The blades were mounted on a hub of a commercially available Wuxi 200 W wind turbine to carry out the experimental analysis in a controlled environment. Both wind speed and electric resistive loads were varied to achieve the desired tip speed ratio. It was observed that the rotational speed of the micro-wind turbine is affected by the resistive torque induced by the electric loads connected to the circuitry of the permanent electric generator. After the experiments, it was inferred that the optimized blade is well justified to operate in low wind conditions. The power outputs claimed by both blade element momentum theory and computational fluid dynamic analysis of the blade lag 40 % and 17 %, respectively. However, the experimental investigation shows superior starting time performance as it leads both the BEMT model and 6DOF analysis by 2.8 s and 3.25 s, respectively. The observed power coefficient at the tip speed ratio of 5.71 is 0.28 and that of the staring time is just 1 s. Cut in speed for the optimized blade was 3 m s-1 which is far better as claimed in blade element momentum theory i.e., 5 m s-1, and its performance analysis was conducted numerically. Therefore, this optimized blade design for micro-wind turbines is desirable for urban environments with wild wind resources.
