Performance evaluation of curved blades vertical axis wind turbine

Abstract

Wind is a natural resource and it can be used as an alternative energy. Many sites in Thailand have satisfactory potential of wind energy such as the average wind energy of Chiang Mai was 128.95 W/m2 and many locations in Northern part of Thailand aresuitable tosetup the electrical generation system from wind. The present work studied theeffect of the operating conditions (tip speed ratio) to the starting rotation, rev up rotation, power and torque coefficients of Curved Blades Vertical Axis Wind Turbine (CB-VAWT). CBVAWT was tested in the laboratory scale in wind tunnel with setting velocities of 1.5, 2.0, 3.0, 4.0 and 5.0 m/s. Four identical blades of semi-cylindrical hollowed drum shape were the main essential parts of CB-VAWT. Of which each blade was attached to a horizontal radius arm at 90° apart, to a single vertical axis shaft. Studies were consistedof starting behavior, starting sequence behavior, constant rotational behavior and torquecoefficients. Blades of turbine were hollowed cylinder of closed ends, with 15 cm length and 30 cm height. The swept diameter of turbine was set at 300 mm2. The analysis of the experimental results showed that when the rotational speeds of CB-VAWT become is zero (shaft locked) with increasing caused maximum tangential force at the torque-pulley. Cut in wind speed increase corresponding to the increasing of tangential force ratio. The rev up rotation period depends on wind speed and tangential force ratio. The moretimeof rotor was required in order to accelerate from starting up to reach the rated rotational speed, in accordance with increasing of tangential force ratio and/or decreasing of wind speed. The optimal tip speed ratio to create the higher power coefficient, for the designed experimental configuration, was within the range of tip speed ratio of 1.5 - 2.5. The power coefficient of CB-VAWT reaches value of about 5 - 7.5%. However at a constant wind speed, torque coefficient diminished with an increasing of the tip speed ratio. ©EuroJournals Publishing, Inc. 2011.