Instructables

Is it possible to turn a small, novelty windmill into a generator?

The windmill is very small - probably about five feet tall, judging by my own height. It is very simply four posts holding up a rotatable windmill / fan with a tail. Both the fan (the blades) of the windmill and the entire top piece (the fan and the tail) rotate. It is a little rusted, but still works perfectly - as evidenced by the creaking and squeaking we heard on a windy day! It can work up quite a bit of speed. Unfortunately, due to the wind, we also get a lot of power outages. I don't expect that such a small windmill could power an entire house, but if it could power a computer or a freezer/fridge we'd save a LOT of money -- every time the power goes out my mother's computer fries and all the food we just bought goes bad. Is it possible to turn this into any sort of generator? (The windmill is outside and while we DO have windows leading in I don't want to encourage any critters. HOWEVER the windmill IS near a door from our garage that no longer opens, but does have an old, unused dog-door.)

Think small, like running garden lights. Bicycle generators are really alternators, and are good for a few watts of power. You'll need a full-wave rectifier to turn the output into DC, and a series resistor to limit charging current. You may be able to make an alternator or generator using magnets salvaged from old hard drives. Google or instructables should have something.
S1L3N7 SWAT5 years ago
I think (not completely sure) that you can use a car's alternator. You connect it to the fan shaft and as it rotates it generates electricity.
Absolutely NOT, although it can be done but the results are not efficient at all, the alternator itself needs dc current to power it's internal windings so it generates electricity, this would need a car's battery, and worst of all the car's alternator is designed to spin at speeds of 3000 rpm to generate roughly 14.5 volts.
I knew somebody would know. I only thought it might work because I've seen a couple of these small windmill type generators and they have something that looks very similar to an alternator connected to the fan shaft. I think they have something like a strong magnet rotating inside a coil of copper wire that induces a current when it spins.
Prfesser5 years ago
Any windmill can be used to generate power but the size you're describing is unlikely to provide enough power to be worth the trouble and expense. Power is a function of blade diameter and speed. otherpower.com describes a simple wooden windmill that has a 4' diameter prop; that generates only about 60 watts in a 25 mph wind. However, with some determination, scrounging, and a reasonable outlay you could probably make a windmill that would provide the kind of power you're looking for. Much of the hassle and cost will be to tie into the grid so that the power is actually usable. I looked at the possibility some time ago but it turns out that my geographic area is not a good one for wind power...
Inept-Parrot (author)  Prfesser5 years ago
Would this cost a lot of money? I'm fairly low on cash at the moment, and if it can't power even just a fridge or something alone then I don't want to spend the money. How much would said motors/outlays, etc, cost...? And really, I'm not an electric genius. I'm sorta experimenting around, but I don't know the science or terminology or anything like that.
As I implied, I haven't done this. What most people do with a windmill is tie it into the electric grid and sell the electricity they generate back to the power company when the wind blows, then pay for electricity when there's no wind. With a large enough windmill this can bring the cost of electricity down to zero.

You appear to need a more-or-less continuous power output to run a fridge; around 1000 watts all the time. A windmill alone won't do that. You need storage for when the wind doesn't blow. And you'd need a pretty large windmill--rough guess is a couple thousand *IF* you built the stuff yourself rather than buying commercial (take a look at the ten-food dia. blades of a 700 watt windmill at http://www.otherpower.com/turbineplans.shtml).

In short, it doesn't look like a do-able proposition, sorry.
Inept-Parrot (author)  Prfesser5 years ago
Mm. Thanks anyway for all the help.
omnibot5 years ago
Look into stepper motors.
lemonie5 years ago
Hook a motor up to it and run some load tests.
You'd want a fairly large motor, (powerful RC car for example) or anything that would normally use quite a lot of power at low voltage.
You'd probably want to feed this into a UPS by way of charging it.

L