7 Foot Axial Flux Wind Turbine
When I first began this project I had a decent grasp of electricity and electronics, which was helpful. I knew hardly anything about wind turbine design, but picked it up quickly with the use of several books and websites.
The books and works that have been most influential in the building of this wind turbine include:
–Windpower Workshop by Hugh Piggot
–Windpower by Paul Gipe
–Arc Welding Instructions for the Beginner by The James F. Lincoln Arc Welding Foundation
-Otherpower.com as well as many helpful individuals on the Otherpower forums
If you want to know more about electricity or electronics, the book Teaching Yourself Electricity and Electronics by Stan Gibilisco is a great learning book and valuable resource to have around.
Here is a video of the final project.
(The whole thing about the modern day Don Quixote… yeah, I don’t think it’s right either.)
Step 1: Deciding on Size
Since this is my first wind project, I decided to work on something that is a bit easier to construct than a high-output “dual rotor” design. I also didn’t have a lot of metal fabrication shops available to me, so I was looking for something that required little fabrication.
A Volvo brake rotor has become popular among homebrew windpower enthusiasts because of its wide availability and its relative ease of modification. Volvos have a reputation for being long lasting and their rotors are not much different. A trip to the junkyard landed me with a $20 Volvo 340 strut (rotor, spring, and everything).
A single rotor design only has one set of magnets that spin in front of a stator coil. This makes construction easier and less dangerous, since you don’t have to use “jacking screws” to bring together two magnetic disks. This is dangerous because if you slip, you could very well break your hand or finger. With a single rotor design, there is much less chance of this.
One thing that many people don’t realize about wind turbines is that the blades of a particular turbine are matched to its generator. This is all based on what is called “Tip Speed Ratio” or TSR. By matching the correct blade diameter to your generator, you ensure that the turbine will start generating at a certain wind speed. By having the right size blades and generator, the correct RPM and torque will be produced to generate the maximum amount of power safely (that is without overheating or over-speeding the turbine). Matching the blades to the generator is a very important aspect of designing your windmill, and many other aspects of the machine are based on the blade diameter.
For this particular design the blade diameter should be around 7 feet.