How to Build a Wind Turbine for Your Science Fair?
Wind turbines are classified into two types depending on its axis of rotation. The turbines that have a horizontal axis of rotation is called Horizontal Axis Wind Turbine (HAWT). Here the axis of rotation is parallel to the ground. In a Vertical Axis Wind Turbine (VAWT), the rotor rotates against a vertical rotor shaft. Depending on the type of rotor blades, VAWT is further classified into Darrieus model, Giromill, Helical Blade VAWT, Cyclo turbine and Savonius. Darrieus and Savonius are the two basic models. Other models are modifications of Darrieus model.
One main difference of Darrieus and Savonius models are that the former uses the lift force for its function and the working principle is similar to a HAWT which also uses the lift force to generate power. The Savonius model makes use of the drag force and this makes its rotation very slow. It will have two blades. One side of the blade will catch the wind more than the other and this rotates the rotor. Because of this a Savonius turbine cannot rotate faster than the wind. Since it is slow-rotating its efficiency is very low and is used for low power functions like operating pumps etc. this cannot be used in areas with slower wind speed.
HAWT is the most commonly used wind turbine to generate electricity in a large scale whereas VAWT are used to power individual homes. HAWT has blades with aerodynamic design that produces lift force which turns the rotor. This rotates the generator shaft and drives the generator producing electricity. HAWT is installed with the rotor in the direction of the wind.
The main parts of a wind turbine are the rotor, gearbox and generator. How to build a wind turbine for your science fair? Building a simple model HAWT is explained below.
The blades could be made from bamboo or PVC pipes. You will need a PVC pipe 24 inches long having a diameter of 8”. Cut his into 4 equal parts along the length. Take 2 of these pieces and mark a point at 30 mm distance from the side at one end and similarly at the diagonally opposite end. Draw a line connecting these points and cut along the line. You will get 4 triangular pieces which are right angled. Out of this 3 pieces are used as blade.
Next 2 holes have to be drilled on all the blades 3/8 inches from the straight side, one at ½” and the other at 1 ¼” from the wider side.
You will need a 260 VDC continuous duty motor of 5 Amps. Mark 3 equidistant holes on the hub 2 3/8 inches from the centre of the shaft. Holes have to be drilled with 7/32 inch drill bit and tapped with ¼”x20 tap.
The blades have to be bolted on to the hub through the holes using ¼” bolts. Through the empty hole on the blade mark on the hub so that it can be aligned easily.
This has to be assembled over a base tower made of PVC pipe. The wires of the motor has to be taken down through the pipe and connected to a bulb or LED.
Your HAWT is ready.