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Tiny Wind Power - Next Step

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oldchris

New Member
I've built a model wind turbine (1' radius) that is actually generating some (not much!) electricity. AFAICT, it makes 6-10VDC (depending on wind speed) and about 10mA (doesn't seem to depend on wind speed). Generator (alternator, I guess) is a stepper feeding into a couple of bridge rectifiers and caps. Right now, all it does is light a LED.

I'd like to have it charge a nicad battery and run a LED from that at night (like a solar garden light).

Is it making enough power to be worth adding a battery and some sort of charge controller? Or should I just be content with a "proof of concept".

TIA,
Chris
 

Mr RB

Well-Known Member
Nice to see someone working with micro wind (nano wind?).

What is your rotor design? You need a rotor with good efficiencies at very low speeds, that generally means lots of blades. So the majority of the frontal area of the rotor is blade area. Imagine a single circle of metal sheet cut with 8 slits, then bent into 8 fat "blades".

Also, power generated is at the square of rotor diameter, and the CUBE of wind speed.
1 foot diameter is very small, going to 2 foot diameter will give you 4 times the output power.

You might want to change to schottky diodes for better efficiency and also consider lifting it higher to get stronger and faster wind.

I'm interested in the exact details of your setup, any pictures? Specs on the stepper motor you used?
 

john1

Active Member
Hi Roman,
Nice to see you.
Only just realised who RB is.
John :)
 

tcmtech

Banned
Most Helpful Member
Get us some pictures when you can!

I have a whole bucket of small permanent low speed magnet motors and steppers. I have often thought about doing one as a just for fun project.
I was thinking of hand carving a three or four blade rotor though. More speed and higher efficiency.
At the one foot diameter size a fair wind (15+ mph) should still give you 5 - 10 watts peak I would think.

My brother just finished his 3 axis CNC carving machine so I may have to learn how to program it and have it cut out my blades for me!
 

Sceadwian

Banned
I'm curious about the mini-wind generators. I've seen some one TV that look like 3 or 4 vertical airplane wings rather than a standard fan blade type design, would building something like that on the hobbyist level be practical? I hear they take better advantage of slower wind speeds.

They look kind of like this, only the one show I saw them mentioned briefly on they were MUCH smaller.
http://img.alibaba.com/photo/12172680/Alvesta_Vertical_Axis_Wind_Turbine.jpg

I think their primary advantage is they don't have to be aimed at all, they'll pick up speed with wind from any direction.
 
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oldchris

New Member
Pictures attached. Sorry, they're not in the natural setting. The silver tube in the close up is a AA battery for scale.

Stepper is a "Fuji Electrochemical Co. SMB40-9608-A" from the surplus pile.

"How are you measuring the current? " - busted! You caught me on one of my weakest points. Amps have always confused my since intro to electricity in college n years ago. I just set the meter to milliamps and inserted it between generator output (post AC/DC conversion) and load (LED+resistor). Suspect I'm actually measuring what the LED is asking for, rather than what the generator is capable of delivering. Any advice appreciated.

Blades are cut from 2" PVC pipe.

Chris
 

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oldchris

New Member
I'm curious about the mini-wind generators. I've seen some one TV that look like 3 or 4 vertical airplane wings rather than a standard fan blade type design, would building something like that on the hobbyist level be practical? I hear they take better advantage of slower wind speeds.
VAWTs (vertical axis wind turbines) are low speed devices generally. Supposed to be hard to start, but produce good torque. I have a few Savonius style "art" turbines in the backyard. They seem to start ok, but they don't have any load on them.
 

tcmtech

Banned
Most Helpful Member
AM I seeing this wrong? But are those just regular fan blades?
If so, turning them about 45 degrees (clockwise as viewed from the picture) would change them into "generator" blades and get the rotor going clockwise and with a noticeable speed and efficiency improvement.

Just a, "Been there done that, and makes a big improvement" suggestion.

Does require a little hub mounting point adaptation though.
 

Sceadwian

Banned
Out of curiosity what made you chose a stepper instead of a DC motor as the generator?
 

oldchris

New Member
AM I seeing this wrong? But are those just regular fan blades?
If so, turning them about 45 degrees (clockwise as viewed from the picture) would change them into "generator" blades and get the rotor going clockwise and with a noticeable speed and efficiency improvement.
Not sure what a regular fan blade is. Rotation is CCW when facing the unit (CW from the gen's POV).

Blade design seems popular with the online wind power folks - sections of tube/pipe cut on an angle. Originals were thinner, turned faster, but didn't produce enough torque to overcome stepper cogging. I'm not 100% happy with them, but they seem to work for now.

Chris
 

oldchris

New Member
Out of curiosity what made you chose a stepper instead of a DC motor as the generator?
no great insight. started with regular DC motor, but couldn't get much output, even by chucking the shaft in a cordless drill. this stepper was the first one that a turbine could turn in less than hurricane winds.

eventually, I may try a 5 blade rotor to get more torque to overcome stepper cogging.

Chris
 

Sceadwian

Banned
oldchris, use gearing on a DC motor. Directly trying to power the main drive shaft from the propeller is usually a bad idea, they typically have some kind of planetary gearing.
 

tcmtech

Banned
Most Helpful Member
Doesn't the generator and blades being off set to one side of the center pivot point and having the tail mounted to the other side cause sever side to side oscillation when in the wind?
I built a bigger one as a teenager that was like that and it was horribly unstable.
Having the pivot point, blade center, tail in line with each other cured my problems.
 

Mr RB

Well-Known Member
Nice setup complete with auto feathering!

I've gotta agree with Tcmtech you seem to have the blades backwards, as it spins counter-clockwise the leading edge of the blade is a flat surface acting like a big air brake.

That flat surface should be on the rear of the blade and the back of the blade in rotation, where it is in the low pressure region.

Your stepper is not a good choice, the 24v is ok but its a 48 step motor, you will get better power and at lower windpeed with a 200 step motor. And those "pressed can" type steppers have much weaker magnets than the more modern NEMA23 size.


And to John1, Hi! :)
Now you got me trying to remember you... John1 isnt much to go from especially with my crap memory. :(
 

bryan1

Well-Known Member
G'day Oldchris,
looking at those pic's you put up I've a few tips for you

1. I'd go with a 2 blade setup for a stepper and checkout this link the Otherpower.com Discussion Board || Here are the plans to make PVC Pipe Props

and make sure you have plenty of clearance between the blades and the tower as pvc will bend back a fair ways when spinning fast.

2. that stepper is a tad on the small side to get really anything out of it, when I made mine for fun I used a 5 volt 1 amp bipolar stepper and its now on it's second set of zubwoofer blades after the first set ended up in the next paddock after a storm. I did have 14" tower clearance and the 2' blades still the tower.

3. As steppers will output AC you need a simple rectifier and this link
TheBackShed.com - MiniMill Part1

is a good example of how to turn a stepper into a decent nicad battery charger.



All in all stepper motor wind gennies not only are garden art but they do and can provide power for night lights. My stepper genny is hooked up to a 12 volt 7ah gellcell battery and about 25 leds provide a night path between my house and shed at night. I setup a switch at both ends so eitherway I can have the lights on when walking back and fro at night. I also made a simple dumpload controller with is a length of nichrome wire stuck in an ants nest close to the genny. when the dumpload is on the ants go nuts and if I'm around out comes the deisel and a match and it'd top fun watching flaming ants run around.

Cheers Bryan....... sitting back suckin in a few boags on a saturday arvo
 

Joey Briffa

New Member
wind turbine

Dear friend,

Since I'm new to this electronic site, I am not sure how to respond to enthusiasts on these pages, but Ive tried anyway hoping this is how.
All I wish to tell you right now, is to watch my videos on you tube,
just type My Wind Generator By day and there you'll see a couple of wind turbines I have successfully built.
I also used a stepper, but I managed to light up 6 LED's of 10,000 mcd each.
You may contact me if you want.

Regards

Joey
 
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Willbe

New Member
it makes 6-10VDC (depending on wind speed) and about 10mA (doesn't seem to depend on wind speed).

Is it making enough power to be worth adding a battery and some sort of charge controller?
If you can find a battery whose C/20 or C/10 rate is 10 mA, then yes.
 

oldchris

New Member
Nice setup complete with auto feathering!

I've gotta agree with Tcmtech you seem to have the blades backwards, as it spins counter-clockwise the leading edge of the blade is a flat surface acting like a big air brake. ...

Your stepper is not a good choice, the 24v is ok but its a 48 step motor, you will get better power and at lower windpeed with a 200 step motor. And those "pressed can" type steppers have much weaker magnets than the more modern NEMA23 size.(
The auto-furling mechanism was tough to get through my head, but now that I've got an example in my hand it makes more sense.

I'm having trouble visualizing the "backwardness" of the blades. Think I'll do some experiments tomorrow with the original blades & hub (similar profile, but a bit thinner. went quite fast, but not much torque at all).

Not overly happy with the stepper myself, but it was the first one I came across where the turbine could overcome the cogging at low windspeed. Next time I'm in the city I'll go back to the surplus electronics store and see what they've got.

Chris
 

oldchris

New Member
Cheers Bryan....... sitting back suckin in a few boags on a saturday arvo
Where did I put that Aussie/Canuck dictionary??

I've made miniature two blade props using that design trying (unsuccessfully) to improve yaw control in an Air Hogs Havoc Heli. Ah well, the cat still likes the heli.

Have the AC to DC part sorted, but thanks for the link to the charger circuit. Like the dump load application too. The SPCA will probably show up to defend the bugs, though.

Chris
 
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