INCREASE OF WIND TURBINE EFFICIENCY AND DECREASE OF MANUFACTURING COSTS

摘要

This article explains design and development procedure of a 3kW horizontal axis wind turbine withthree blades and rotational diameter of 5.6 meters. Several approaches have been tried in order toincrease turbine efficiency and reduce its production costs. To attain these aims, in blade designing, itwas intended to reduce the blade weight. There are two reasons that weight reduction causes increaseof efficiency: The first is reduction of friction force at bearings and the second is reduction of momentof inertia of the blades.In order to reduce the blade stresses, guying cables are used at two parts: Tip of the blades wereconnected to tip of a bar in front of the rotor. It causes the blade conditions to change from a cantileverbeam to a propped cantilever beam with two supports and stresses reduce to 1/18 of its common form.At second part, tips of the blades were connected to each other to form a triangle that eliminates thebending moments at the blade roots due to their weights. Therefore in blade design a thinner metallicframe was used, so it caused not only weight reduction but also possibility of forming the blade rootwith more efficient thinner airfoils and exerting large setting angles at root that causes both increase ofefficiency as well as rapid starting. That means reduction of cut-in wind speed.The results of the field evaluation tests showed that the turbine started spining at 1.2 m/s wind speedand reached its nominal power (3 kW) at 8 m/s wind speed with a power coefficient equal to 0.445.