Instructables

How would I choose the most efficient electric motor to use as a generator for a small wind turbine?


I have a school project to build a small wind turbine (approx. 8" propeller diameter) to produce the maximum out DC voltage possible.  We are still deciding between a horizontal & vertical orientation (leaning towards vertical) but we need some help on understanding what we should look for in the motor/gear setup in order to produce the maximum possible voltage at relatively low wind speeds.  What should I look for and where would be a good place to buy/scavenge these parts?

Thanks!

iPodGuy3 years ago
Treadmill motors are used a lot for making wind turbines. I think they're called Chispito turbines or something like that. And who doesn't know somebody with an old treadmill sitting around?
rickharris3 years ago
In general - IF you can turn it fast enough - the larger voltage the motor should run on the bigger the voltage output.

So a 24 volt 250 watt motor will produce more electricity than a 3 volt model motor.

For max output you should look at winding your own motor - there are instructables on the subject.
ddrocketman (author)  rickharris3 years ago
Hmm I'll look into that however due to time restrictions I was looking for a suitable motor to use just incase.

So I assume I would need a motor that would be very easy to spin the shaft, and is rated for the highest voltage. Have any idea what I should search to find a motor like this or a electronic product I can hack apart that's likely to have a good motor for this purpose?

Thanks!
All/most electric motors spin easily if they have no load. As soon as you load them you start having to put effort into them to get energy out.

You can't get something for nothing - 250 watts out (watt a measure of power) required more then 250 watts in (to account for electrical and mechanical losses).

250 watts is about as much as a trained athlete can provide.

Bigger voltage, (in general), come from a motor that uses a bigger voltage to drive it. it's as simple as that. This is not a perfect analogy but for your level of work it will do.
Maximum VOLTAGE or maximum POWER ? Take a little DC motor, gear it up, and put no load on it, and you'll make plenty of volts, but zero power.

DC motors will need to be spun VERY fast to get a decent voltage, so gears or toothed belts would be a good bet

Steve
ddrocketman (author)  steveastrouk3 years ago
Well the final output only has to be DC...we can convert from an AC output to dc to be measured. And ya we are only measured on voltage.

I have some different motors at home and it seems that in general the higher voltage the motor is rated for the harder it is to turn.

I have some very small motors that would be very easy to make the shaft spin very fast...but I assume that these small motors would have a limit to how much voltage they produce?

The output voltage only needs to be able to power an LED, but we are marked on max voltage and not power.
There's no need for a higher voltage motor to be harder to turn.

Making yourselves an alternator, by spinning a magnet inside a motor body might be a better way still to get high voltages.

Steve
ddrocketman (author)  steveastrouk3 years ago
Ahh great idea I'll check that out thanks!