Does a steeper blade angle make a windmill produce more electricity? Most people guess 45 degrees is ideal. The real answer may be different.
You build a small windmill from construction toys and attach it to an electric generator. You cut blades in four sizes from venetian blind slats. A fan blows air at the windmill from one meter away. You set the blades at angles from 0 to 90 degrees and read the current output on an ammeter.
The highest current came at 75 degrees for every blade size that spun. At 90 degrees the blades sat flat against the wind and produced nothing. The 300 cm² blades beat the larger 400 cm² set. The bigger blades were too wide for the windmill frame.
Hypothesis
The hypothesis is that the closer the blade is to 45 degrees, and the bigger the blade, the more electricity the windmill will produce.
Wind is a renewable energy source because moving air is constantly replaced by weather patterns. A windmill converts that moving air into electricity through blades connected to a generator. Blade angle turns out to matter more than most people expect: at 75 degrees, every blade size that spun produced the highest current output.
This project captures wind energy by blowing air from a fan at a small windmill connected to an electric generator. You set the blades at angles from 0 to 90 degrees and read the current output on an ammeter.
Blade angle controls how much wind a blade catches. Tilt the blade too flat and it slides through the air without pushing. Tilt it too far and it blocks the wind like a wall. In one test, blades set at 75 degrees produced the highest current. At 90 degrees the blades sat flat against the wind and made no power at all.
Method & Materials
You will build a windmill, attach blades of different sizes and angles, measure the current output, and take notes.
You will need electrical wires, a rubber band, a fan, a tape measure, a windmill, an ampmeter, a protractor, an electrical generator, and 8 blades of 5cm x 1cm, 10cm x 1cm, 15cm x 1cm, and 20cm x 1cm.
Tinker Crate — science & engineering build kits for ages 9–12 — real tools, real experiments, delivered monthly. (Affiliate link)
The results showed that the closer the angle of the blade to 75 degrees, the more electricity was produced for all blade sizes except 100 cm2. At 90 degrees, there was no current generated at any of the blade lengths. The hypothesis was rejected because the greatest amount of electricity was produced at the 75 degree blade angle.
Why do this project?
This science project is interesting because it shows how the angle and size of the blades affects the efficiency of a windmill.
Also Consider
Variations to consider include testing different blade widths and testing different wind sources.
Full project details
Additional information and source material for this project are available below.
