During the last few days, I have been working on the final dimensions for this VAWT.
It is difficult to decide on a certain size because I want to use parts that are readily available. I do not want to do any welding or machining to keep it simple and easy to assemble. The final design and dimensions were mostly dictated by what parts I could easily find. Overall, I am happy with the shape and with the dimensions.
Here is an image of what the final design should look like.
The image only shows two blades, but it will have three. The image also shows the center shaft to be 48 inches long, but I am hoping that the final product can be constructed using a 36-inch shaft, because that size is more common. I am using the 48-inch shaft because I want a larger area in the center so I can try different sizes for the central Savonius blades. Ultimately, I want the Savonius to be as small as possible so it doesn't interfere with the H-Darrieus blades.
A turbine of this size could produce about 400 watts with 22 MPH winds (10 m/s). That estimate is assuming that it has a well-designed set of blades. That is going to be the major challenge, building a good blade profile with simple tools and materials.
Originally, I had wanted to build a taller turbine to get more power. But a taller turbine would have to be supported at the top. That would have required a frame around the turbine and complicate things. I want to keep it simple.
Because this turbine is smaller, I can build an alternator using 12 magnets instead of the 16 that I had in mind. The alternator will have 2 rotors with 6 magnets each and a stator of 9 coils. It will be a 3-phase alternator with 3 coils per phase. By using 9 coils I can make them thinner so the air gap is smaller.
This alternator could easily put out about 550 watts.
Today I placed a couple of orders for the rest of parts that I need. I will take a break from this to work on other projects until the parts arrive.
Ed