Development of aLow Cost H - Darrieus Rotor Blade for A Small Vertical Axis Wind Turbine

Abstract

Due to the context of high-energy expenditure in rural areas, Small Wind Turbines are an appropriate solution capable of inducing much needed development opportunity in Kenya’s rural areas. However, utilization of wind energy faces challenges due to the high cost of the imported wind turbines, poor manufacture and/or inefficient locally made wind turbines and lack of appropriate skills base in manufacture. Development of efficient low-cost wind turbines coupled with a strong strategy stands to be a major determinant to promote commercialization on these technologies. This study fabricated three vertical axis rotor blades that aimed to generate power under relatively low wind speed velocities. Using an open source Qblade wind turbine design software a model was developed. The model optimizedchosen design parameters to come up with a prototype of the rotor blade. A final prototype design sizing was a rotor diameter of 2m and length of 1.6 m with a chord length of 0.2 m. and A NACA 0021 airfoil. The selection of the airfoil was influenced by its thickness (21% of chord) and its self-starting behaviour. Based on the final prototype design a full-scale turbine wasconstructed for experimental validation. The material used was Glass fibre reinforced plastics (GFRP). Blade production process involved making of the master blade used to form the mould that wasused to make the blade copies. The blade copies were taken through a sequence stages of lamination, drying, trimming, and smoothing. The power coefficient of the turbine was tested using a wind fan by subjecting it to wind speeds ranging from 4 m/s to 15 m/s. The maximum power coefficient was 0.1 and occurred at TSR of 4. Abattery was used to provide the load in the experiment and controlled by an inverter. A direct drive Axial Flux Permanent Magnet (AFPM) generator developed for small scale vertical axis wind turbine (VAWT) was coupled to the turbine rotors to determine the electricity generation capacity. 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. 280 was the rated RPM for the Generator. The turbine torque was 1.5Nm at an RPM of 175.The turbine has high torque but low rotational speed and a high gear ratio generator may achieve higher poweroutput. Alternatively, multipole electrical generators can be used for direct coupling with the wind rotor. The cost of production of the Rotor blade with all components was about Ksh. 120,000. This cost included buying of the shaft, hubs and bearing (Ksh. 25,000) and the blades amounted to about Ksh. 21,000. In comparison aHAWT turbine of same sizing costsbetween KSH100,000-200,000. As Mostlocal suppliers do not supply VAWT, a comparison with the international price of VAWT of same sizing was about Ksh 180,000. The cost benefit analysis of the system considering an annual energy yield 245 Kwh and the system cost of Ksh 130,000 had electricity generation costs of USD 0.2 per KWh.