Help with unconventional turbine

[Rick Van]

Need some advice with a turbine project. I was wondering if the following is feasible, and if so how would I best carry out this idea with some materials I have.

I want to make a VAWT style turbine and turn it horizontal (kind of like a water wheel)…there’s a unique reason for this. It will have bearings on both ends of the axle, and the axle will be mounted on a stand. The turbine won’t be affected by the elements.

I was hoping to have on each end of the turbine a rotor that crosses a stator. So essentially, each end of the turbine will be a single rotor PMA.

The questions I have regarding this idea are….

1) Are single rotor alternators any good? Most plans I see have dual rotors with a stator sandwiched between them. What’s the downfall (if any) for single rotor over dual?
2) With a possible max rotor/stator diameter of say 20” what would be a good configuration/plan for the stator and rotor layout……keeping in mind I only have 18awg magnet wire (lots of it I need to use up), and would really like the system to be 12vdc?
3) I have been thinking of 4 phases, 2 on each stator, would that be any use?

Thanks.

[Dave Turpin]

Well, there are a few fundamental problems to the design you are thinking of.

One, if you take a VAWT and lay it sideways, it will only work if the wind happens to be blowing directly (or close to directly) perpendicular to the axis of the turbine. If the turbine axis is vertical, it can absorb energy from any direction the wind is coming from (because wind tends to travel in a plane parallel to the surface of the Earth)

Two, I assume that this turbine, based on the design, is going to be very close to the ground. You are not going to get enough wind energy to be usable. This is, actually, the main flaw of a VAWT in general: They are heavy and as such most installations are very close to the ground where there is almost no energy to be had.

Now, to your questions:

1) I assume you are referring to a RADIAL alternator design? If so the point of having TWO sets of permanent magnets is to double the magnetic flux and thus the voltage produced. Having one rotor will still work but with less voltage per loop of wire on the stator.

2) Don't design the PMA to make 12v, especially since you are stuck with small gage wire. Go for high voltage, low current. You should do 1 phase, or 3. Even numbers of "phases" are actually just non-unique copies of the other phases, and your rectifiers won't work.

The important design constraint will be to use enough loops so that you get a high voltage and a low current. Too few wraps and the current will get high enough to fry the windings. Then, design the output based on the input of your battery charge controller or inverter. Most wind inverters can handle 500v or more, but not high current.

Regardless, with this design of turbine you aren't going to get enough power for it to matter anyway, so my suggestions are really only if you change your design to either a true VAWT set on a tower or a HAWT in standard configuration.

[Rick Van]

as mentioned the turbine will be in a unique situation. So some of the conventional thinking on this matter of setup doesn't apply.

Also I hear ya on the wire size....so maybe 70 turns of 2 in hand 18awg? Think that's around a 24v system winding.

3 phase. sounds good. I may change the setup to give it a sammiched rotor. Would three phases of 3 on one side, and three of 3 on the other connected to make 6 coils per phase (18 coils total) with single rotors on each side equal a 3 phase dual rotor sammiched setup?

Thanks,
Rick.

[Dave Turpin]

The design will have to be based on the output. Firstly, what are the dimensions of the rotor, and is it Savonius or Darrius?

[Dave Turpin]

I don't know if you made any progress on your design, but I have been researching simple radial alternators and have come across these "smart drives" used in a lot of similar applications:

PowerSpout - History of the Smart Drive - YouTube

Basically it is the motor used in pretty much every direct-drive washing machine ever. Seems like it should be easy to modify one or two of these to produce whatever voltage and current you are looking to get.

[Rob Beckers]

Dave, thank you for that video. I had not seen that one before. It's a very good overview of the Fisher & Paykel motors/alternators. As pointed out there, one needs to be careful to get one that's the right combo of voltage and RPM. From what I've heard they should be good for around 400W - 500W maximum output power (if matched properly with the right wind turbine rotor). Best of all, you can find 'm for next to nothing from broken washing machines.

-RoB-

[Jeff Birkle]

I have been thinking of the same thing for a long time.
It can be done, and you can always make it pivot with a tail just like a horizontal Turbine.
The Dual Axial Alternator need only be on one end, or make up something that doesn't exist yet like a partial Dual Rotor.
Are you still working on it?
Jeff