Notes

A. Design issues Proper design of wind turbines is one of the most important challenges. The design of wind turbines must be proper with respect to the blade loading (for lighter blades) and aerodynamically stability. Wind turbines are subjected to loads such as inertial, gravitational and aerodynamic. Many researchers have developed mathematical models for the calculation of material and structural stresses for improved design of the horizontal axis and vertical axis wind turbines. Ernesto et al. [7] developed a multi-objective optimization method for the design of HAWT which was based on the coupling of an aerodynamic model (blade element theory) and an evolutionary algorithm. Bierbooms [8] employed a method based on probability to determine the extreme-response of wind turbines which are controlled by varying the pitch angle. This resulted into better description of extreme conditions in turbines and it also enabled wind turbine manufacturers to design more reliable and optimized wind turbines. Petkovic and Shamshirband [9] analyzed several parameters that influence the wind energy generation using adaptive neuro-fuzzy inference system (ANFIS). It was concluded that blade pitch angle is one of the most influential parameter. ‘Aerofoil’ shape is an important design parameter to understand the aerodynamics of the blade. New ‘aerofoils’ have been developed to enhance the capacity of wind turbines for energy capture. Padgetl [10] developed a multiplicative damage model for calculating the strength of fibrous composite materials. It was used to determine the failure strength of these materials. Fuglsang et al. [11] gave design of RISO-131 aerofoil family along with its verification. Slender blades were designed to increase the lift coefficient of airfoils and also to reduce both fatigue and extreme loading. Modern blades have been evolved to its present shape through research and has achieved higher lift-to-drag ratio. There have also been several studies on design modifications such as diffuser augmented wind turbines (DAFT) [12-13]. Research has also been carried out on Building Augmented Wind turbines (BAWT) in which the building shape is optimized to increase the wind energy [14].