Performance enhancements on vertical axis wind turbines using flow augmentation systems: A review

There are many advantages of vertical axis wind turbines (VAWTs) compared with horizontal axis wind turbines (HAWTs). Research has shown that VAWTs are more suitable for turbulent wind flow and urban applications. However, the efficiency and low self-start ability of VAWTs are always the main drawbacks especially for the lift-type VAWTs. Unlike HAWTs, the rotor blades for VAWTs do not always provide positive torque during operation. Many innovative designs have been implemented to improve the performance of VAWTs, and this includes different configurations and blade profiles. This paper extensively reviews various flow augmentation systems and attempts to provide information to researchers on current augmentation techniques and other relevant research. The flow augmentation system is able to increase the coefficient of power, C_P, hence improving the output power of different types of VAWTs. Some augmentation systems are able to increase the maximum power output by up to 910%. The methods and designs used to increase upwind velocity and to reduce negative torque created on the wind turbine have been discussed in detail.