I am designing a turbine that is meant to operate at wind speeds around 35 km/h (21 mph) as possible peaks (barring odd days of higher speeds) to roughly produce anywhere from 200-350 W.

Rough dimensions:

Diameter: 20 cm Height: 15 cm

The above measurements can obviously be adjusted.


5-7 kg (ideally total weight including that of the turbine)

All parts barring ball bearings, axle, etc. are going to be 3D printed.

I need a rough idea as to what sized neodymium magnets I should be looking at. I know I could just test it with different sizes. However, the sizes I am looking at are not exactly cheap. Hence I wish to be as accurate as possible the first time.

I know this is dependant on a lot of factors but I would really love if someone were able to help. I have done a fair amount of research so far. This is the only part I am struggling to conclude before actually building it.

I am going to be using both sides of the magnets with an axial flux version.

Additionally, would circle / rectangular magnets be more ideal?

Magnet sizes in mind:


20x10 mm
20x20 mm
30x10 mm
30x20 mm


50x10x10 mm
50x20x10 mm
50x20x20 mm
60x10x5 mm

I am able to buy a lot of smaller magnets as well. Would placing a lot of smaller magnets (with the correct polarity meticulously placed obviously) be another option? Would this make any difference to the electromagnetic field?

Ideally I am aiming for 150 W with minimal wind 10 mph whilst being around $100-$150 at the most to produce.

Size of the copper coils, etc will be built around the size of the magnet.

  • 2
    \$\begingroup\$ Designing a turbine and designing a generator are two separate things, while I really don't see any good reason for the latter with the abundance of off-the-shelf professionally designed and built ones. \$\endgroup\$
    – Eugene Sh.
    Aug 5 at 19:10
  • 1
    \$\begingroup\$ I don't understand the economical argument of you spending maybe 40 hours researching, designing, printing, building, testing, rebuilding and retesting and generally messing around. OK, maybe 40 hours = $375 in equivalent earnings plus costs of $100 equals nearly $500 so maybe have a rethink about your confidence level on the amount of time you have currently spent and the time you still need to spend. \$\endgroup\$
    – Andy aka
    Aug 5 at 19:44
  • 3
    \$\begingroup\$ The power in the wind flowing through your 20x15cm wind turbine is about 20W at 35km/h. A well-designed system with purpose-made parts might get 40% of that. Your DIY system will get far less. \$\endgroup\$
    – vir
    Aug 5 at 19:46
  • 3
    \$\begingroup\$ Wind turbine calculator <-- your blades need to be about 50 cm long to just about get the power assuming you have the very best blade design possible. \$\endgroup\$
    – Andy aka
    Aug 5 at 20:13
  • 2
    \$\begingroup\$ You might get 500 watts/meter^2 at 20 MPH. So your 20 cm diameter (0.03 m^2) turbine at best might produce about 14 watts. calculatoratoz.com/en/wind-power-calculator/Calc-8272 \$\endgroup\$
    – PStechPaul
    Aug 5 at 20:15


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