Numerical study on the Effect of Blade Geometry on the performance of a Helical and Troposkien Type Vertical Axis Wind Turbines

Abstract

With the growing demand for unconventional energy, wind energy has attracted relatively large interest in research and development. The application of vertical axis wind turbines (VAWT) in the offshore and urban environment is growing steadily. The capabilities of these turbines to work on rooftops, ventilator ducts, allies between buildings etc., make them one of the prime choices for an alternate source of energy where wind directions are unsteady. The interest in such turbines keep growing due to the following advantages. Low installation and maintenance costs , Omni directionality , Low noise and shadow flickers , Low manufacturing cost and simple control system , Scalability , Reliability and robustness , High space efficiency (land area coverage is less compared to horizontal axis wind turbine) .However, less attention has been given in the last few decades to VAWT development compared to Horizontal Axis Wind Turbines (HAWT). The aerodynamics of VAWT is complex and has less efficiency compared to HAWT for now. The flow over a VAWT is very complex. The primary objective of the study is to understand the effect of blade design on the performance of the turbine. There are lot of studies available for straight bladed turbines with reference to various operational and/or design parameters. The objective of this work is to understand the effect of the same for two major non straight bladed designs, Helical blade and troposkien blade. Helical blades are formed by sweeping the airfoil along the circumference of a cylinder. The helix angle depends on the height of the turbine. A troposkien turbine is an airfoil swept along a curve generated by a rope which is allowed to rotate by holding two ends of the rope. These designs are typically known for their advantages. A helical bladed turbine has capacity to generate moment in almost a continuous manner depending upon the helix angle. On the other hand, a troposkien bladed turbine can function with minimum bending stress. The presented work is a detailed numerical..