At what angle should the blades of a wind turbine be positioned?
The materials required for this science fair project are:
- A DC motor (or an old bicycle dynamo)
- 1 zinc sheet (thickness 0.5mm, size 750mm x 600mm)
- 1 pair of scissors
- 7 cubic wooden blocks 50mm x 50mm x 50mm
- 1 electric hand drill and drill bits
- 1 set of needle files
- A protractor
- Screws and a screw driver
- a digital voltmeter
- An industrial fan
1. The independent variable of this experiment is the angle at which the blades are mounted. . The dependent variable is the amount of voltage generated by the wind turbines. This is measured by using the digital voltmeter. The constants or control variables are the wind speed, the weight of the wooden block and the size of the blades.
2. Using a hacksaw, slots at 0, 15, 30, 45, 60, 75 and 90 degrees are cut out of the 7 cubic wooden blocks to fit in the fan blades as shown in figure 1a below.
3. An electric hand drill is used to perforate the center of the wooden block. The shape of the hole is modified using the needle files in order to fit the shaft of the DC motor or dynamo.
4. The blades to be mounted on the wooden block are cut according to the dimensions as proposed in figure 1c. A total of 28 blades are cut out. There will be 4 blades mounted on each wooden block. The blades will be fixed to the wooden blocks using screws.
5. Caution – Ensure that the blades are fixed firmly to the blocks by the screws. Test them by trying to pull them out. It is dangerous if the blades come loose whilst the turbine is spinning.
6. The first wooden block to be tested is fixed to the shaft of the DC motor or dynamo. The wooden block will be fixed to the shaft using a nut. The assembled turbine with the blades will be placed 1 meter in front of an industrial fan. When the fan is turned on, the blades will start to rotate and a voltage will be produced between the terminal of the DC motor or dynamo. The measured voltage is recorded in the table given below.
7. Step 6 is repeated using the remaining 6 wooden blocks and the measured voltage is recorded in the table provided below.
Ensure the blades are properly fixed to the wooden block so that they do not come loose when rotating. Drilling and sawing should be performed by an adult. Safety goggles/gloves should be worn.