Concentrator Augmented Wind Turbines: A review

Wind technology is one of the fastest growing alternative energy technologies. However, the installation of commercially available conventional wind turbines in some countries is limited by the fact that they are generally designed for wind speeds greater than 5 ms(-1). This limits the choice of physical locations where wind farms can be implemented. The concept of a Concentrator Augmented Wind Turbine (CAWT) has been considered to improve the efficiency of the wind turbines by increasing the wind speed upstream of the turbine. No efforts have been done to commercialise this concept because little is known about the wind flow behaviour in the CAWT, its influence on turbine power output and the optimum concentrator design parameters. This paper focuses on an extensive review of experimental and theoretical work done on CAWTs in order to group information together to help researchers understand research efforts done so far and identify knowledge gaps in the field. It has been revealed that the concentrator works best when the turbine is behind the concentrator at a distance of less than 5 cm from the concentrator and the concentrator inlet to outlet ratio being 6. Based on this review, it has been concluded that CAWTs are a promising way of increasing power output in low wind speed areas but their development is being limited by the availability of scant information on their operation. More experimental and theoretical work still needs to be done to understand various flow features that may be present in the system such as turbulence, eddys, veer and wake effects and their influence on power output. In addition, there is need to optimise the concentrator wall length and the incident angle since they depend on each other while influencing concentrator frictional losses. (C) 2016 Elsevier Ltd. All rights reserved.