Experimental study of local pitch variations on electric power generated by counter rotating wind turbine with single generator without gearbox

Wind energy is one of the clean renewable energy that can be used as an alternative to reduce fossil fuel consumption. The aim of this research was to design and test the performance of counter-rotating wind turbine (CRWT) model corresponded with wind velocity and planned power output. The CRWT has two rotors with a diameter of 0.70 m comprised of NACA 4412 airfoils, which separated by axial distance of 0.3D and connected directly to each shaft of DC generator without a gearbox mechanism. In this research, local pitch (θ_p) of the rear rotor can be varied as followed (-10°, -5°, 0°, +5° and +10°). The data collection was done in a wind tunnel with a constant wind speed of 4 m/s, and given a load from bulb lamp started from 0 to 4.5 watt every 0.75 watts. The result shows that the local pitch +10° produced the highest rotation and electrical power generated. The highest electrical power generated at a local pitch +10° was at load 0.75 watt in amount of 1.057 watts or 23.55% higher than normal rotor (θ_p = 0°). At the same load, the lowest electrical power generated was at the local pitch -10° which only produced 0.598 watts. (paper)