Performance and design optimization of a vertical-axis straight-bladed darrieus wind turbine

Abstract

A theoretical investigation of aerodynamic performance and design is carried out for vertical-axis straight-bladed Darrieus wind turbines. Aerodynamic performance is performed with blades of cambered;cross-section while design is conducted with blades of symmetric cross-section. For the aerodynamic analysis multiple streamtube theory and cascade theory are applied. In order to choose the lift and drag coef.ficients for the cambered blade profile, concept of thi@airfoil theory has been applied. A cascade principle ( Similar to that used in turbomachines) with blades of cambered cross-section is applied for the performance prediction of a vertical-axis straight~bladed Darrieus wind turbine. By using the blades of cambered cross-section, the lift force increases in the upwind side and decreases in the downwind side in comparison to those for a turbine with symmetric blade cross-section. As a result higher power is produced in upwind side and lower power is produced in downwind side for a turbine with cambered blade cross-section in comparison to those for turbine with symmetric blade cross-s.ection •.However the net power production is positive thereby making the higher efficiency. The calculated results of. cambered blade cross-section are compared with those of symmetric blade cross-section. A design of a straight-bladed Darrieus. wind turbine with blades of symmetric cross-section is performed. The design is done at variable turbine speed condition. In order to mini mize the blade stress and with a view to use the low cost material for blade manufacture the blade support.type is considered to be overhanged type. It is observed from the design analysis that this design with overhanged support reduces the blade stress remarkably.