Alternator for Low Wind Speed Wind Turbine.

  • Thread starter MechaMZ
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Hi

I've a wind turbine which have to run under a very low wind speed, from 2-3m/s.

Currently, I'm using Envirotek V20, the result is around 1.5V-2.5V, and current is 0.3mA or nearly zero.

My aim is to achieve 50W.

Any suggestion for the alternator which I should use?
p/s: without aided by any gear arrangement.

thanks alot.
 

russ_watters

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Are you sure you have 50W of available wind energy at 2-3m/s? The alternator's size, unless it is absurdly large, doesn't affect the output power much.
 

LURCH

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Along with what Russ said; if the windspeed is that slow, I don't think any change of alternator is going to give you the Watage you're trying for. The only thing I can think o ffor increasing output is increasing input. Since you can't incrase the wind's speed, I suppose this will mean increasing the size of your airfoil blades. Catching more wind at the same speed will increase the energy that is being input into your system.
 
128
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Along with what Russ said; if the windspeed is that slow, I don't think any change of alternator is going to give you the Watage you're trying for. The only thing I can think o ffor increasing output is increasing input. Since you can't incrase the wind's speed, I suppose this will mean increasing the size of your airfoil blades. Catching more wind at the same speed will increase the energy that is being input into your system.
think this is a good idea..

I will try out with an experiment..

thanks alot..
 

russ_watters

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What is the size of the turbine? We can help calculate the available energy and likely capture.
 
128
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What is the size of the turbine? We can help calculate the available energy and likely capture.
I'm using this currently..
www.envirotekpower.co.uk/V20info.html

but I'm going to redesign the turbine blade..
currently, I have few designs. they are most likely same as these examples
www.peswiki.com/index.php/Image:Statoeolien_95x95.jpg
www.peswiki.com/index.php/Image:Helix_Wind_95x95.jpg
www.hi-energy.com.tw/selection-6-english.htm[/URL]
[url]www.oregonwind.com/[/url]

just not sure which can really function good in low wind speed, 2m/s-3m/s
I think I have to run a few test on them..

by the way, you are so kind, really thanks :)
and I'm very appreciate..

p/s: sry for the urls..
 
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Besides change the size of wind blades, Do you think it's possible to generate 50W with a gear system?

my v20 now is able to achieve 165rpm @ 4.3m/s, and the current produce is almost 0! (even the wind speed reach 8m/s)

do you think just because the alternator is a lousy one?

many thanks:)
 

russ_watters

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More gearing will only hurt you - it doesn't amplify energy and you lose energy from friction.

According to the site, that turbine only generates 3W (.25A @12V) at 4.5m/s using a turbine with a cross sectional area of .18 m^2. I don't have time to run through the energy calculation for the wind right now, but my gut tells me that if theirs can only generate 3W, you have no hope of generating 50W with a turbine that small.
 
128
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More gearing will only hurt you - it doesn't amplify energy and you lose energy from friction.

According to the site, that turbine only generates 3W (.25A @12V) at 4.5m/s using a turbine with a cross sectional area of .18 m^2. I don't have time to run through the energy calculation for the wind right now, but my gut tells me that if theirs can only generate 3W, you have no hope of generating 50W with a turbine that small.
how about with only 2 gears, as to increase the rpm of alternator.

wind turbine with a bigger gear, and small gear for alternator. So my alternator able to turn more round as wind turbine gear turns one round.

or I can let alternators connected in series since my project can involves more than 1 wind turbine and alternator.

thanks alot
 

russ_watters

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Well, you could certainly run 20 of them in parallel, or hook 20 up to a common alternator.

But again, just changing the gear ratio does not change the energy you can generate. You'll increase the rpm, but decrease the torque.
 

russ_watters

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The wind energy available to one of those turbines, by the way, at 4.5 m/s is 8 watts. That's based on a kinetic energy calculation: 1/2 mv^2 = .5*(4.5*.18*1.29)*4.5^2 = 8. A total system efficiency of just under 40% is pretty good, so I wouldn't expect you to be able to beat their performance.

1.29 kg/m^3 is the density of air.
 
128
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this fact is really disappoint me :(

but how about increase the wind turbine size and with the help of gear ratio?

thanks again
 
128
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I found this design is able to generate around 200 watts @ 10mph, 4.4704 m/s.

unfortunately it is horizontal wind turbine.

and it's able to generate 200W @ 4.4704 m/s, because it is horizontal?
 
128
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Dear Russ,

I've found this, which is able to generate 150 Watts in a 10 mph wind!!

Wow!!
 

russ_watters

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Dear Russ,

I've found this, which is able to generate 150 Watts in a 10 mph wind!!

Wow!!
That person think's he's found a revolutionary new way to capture wind, but he hasn't. His own tests should tell him that:
We averaged 20 mph winds, which spun the wind turbine at 120 to 130 rpm, which translates to speed of circumference of the 4 ft dia. sail-disk of 17 - 18 mph, which is 85-90% of the wind speed, spinning the bicycle wheel on high gear at 52/14 = 3.7 x 130 = 481 rpm x 27” = 47 mph. There was not enough torque to turn the powerful bicycle motor (with it’s 1.25” roller and much magnetic and frictional resistance at that speed ~ when we geared down it could almost balance the friction of the motor, but we didn’t generate much power. [emphasis added]
 

russ_watters

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but how about increase the wind turbine size and with the help of gear ratio?
Yes, the physical size of the turbine is the key factor in determining how much power it can generate.
 

russ_watters

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and it's able to generate 200W @ 4.4704 m/s, because it is horizontal?
No, it generates more power because it is bigger.
 
128
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dear russ, could you recommend some alternators that are suitable for low wind speed?
because I'm trying to find those can generate well current & voltage under low wind speed.

because this is the first priority then turbine design and gear system.
 

Redbelly98

Staff Emeritus
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The wind energy available to one of those turbines, by the way, at 4.5 m/s is 8 watts. That's based on a kinetic energy calculation: 1/2 mv^2 = .5*(4.5*.18*1.29)*4.5^2 = 8. A total system efficiency of just under 40% is pretty good, so I wouldn't expect you to be able to beat their performance.

1.29 kg/m^3 is the density of air.
Russ, is that 8 watt figure per square meter, or for the area of Mecha's particular turbine, or some other area?

I agree that increasing power must come from using larger turbine blades.
 

russ_watters

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Russ, is that 8 watt figure per square meter, or for the area of Mecha's particular turbine, or some other area?
Just that particular turbine - the .18 in the equation is the cross sectional area of the turbine in square meters.
 

russ_watters

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dear russ, could you recommend some alternators that are suitable for low wind speed?
Sorry, that I really can't help you with except to say that I'd try to match the input and output power to each other to minimize loss. So that would mean basing the selection on the maximum expected load/wind, not the low end.
because this is the first priority then turbine design and gear system.
The difficulty here is that all of these parameters are interdependent. "Low wind speed" is not a property of an alternator, it is a property of a turbine. So my design process would go like this:

1. Determine performance requirements (peak watts, minimum watts, min/max associated wind speed).
2. Select an alternator that covers the entire range of power required.
3. Select/design a turbine system that is capable of providing the required performance (remembering to include inefficiency factors).
4. Select/design a gearing system to transfer the power between the turbine and alternator.
 
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My research on this subject led to an inescapable conclusion: The only way to get the kind of efficiency desired is to build the alternator yourself.

There is basically no possibility of buying an 'off-the-shelf' alternator that doesn't make tradeoffs you're not interested in.

An alternator's efficiency can be improved in several ways, but none of them are very likely to have been found worthwhile for commercial uses. Using the strongest magnets possible is a big one (rare earth magnets), designing the rotor and stator to be as close together as your methods permit is another, using three-phase power (more efficient generation) is a biggie... and biggest of all; if you design an alternator with a specific turning speed, friction load, and output in mind, you can get much further along than any 'savings' in time or effort that would accrue from buying your alternator 'as-is'.

I can see how you might think alternator design and building is a daunting task, but I assure you, it's worth it... and probably not as difficult as you might first think.

Let me put it this way: If you try everything else suggested and still see only minor improvements/ negligible output, then how reasonable would it sound to suddenly achieve what you wanted at the cost of 'merely' building an alternator? Put in a thousand man-hours with nothing to show for it and I'll wager that even a "herculean" 100-hour-effort will seem like nothing, if that's the price for success.

There are useful data on this subject available; let me know if you're interested.
 
128
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My research on this subject led to an inescapable conclusion: The only way to get the kind of efficiency desired is to build the alternator yourself.

There is basically no possibility of buying an 'off-the-shelf' alternator that doesn't make tradeoffs you're not interested in.

An alternator's efficiency can be improved in several ways, but none of them are very likely to have been found worthwhile for commercial uses. Using the strongest magnets possible is a big one (rare earth magnets), designing the rotor and stator to be as close together as your methods permit is another, using three-phase power (more efficient generation) is a biggie... and biggest of all; if you design an alternator with a specific turning speed, friction load, and output in mind, you can get much further along than any 'savings' in time or effort that would accrue from buying your alternator 'as-is'.

I can see how you might think alternator design and building is a daunting task, but I assure you, it's worth it... and probably not as difficult as you might first think.

Let me put it this way: If you try everything else suggested and still see only minor improvements/ negligible output, then how reasonable would it sound to suddenly achieve what you wanted at the cost of 'merely' building an alternator? Put in a thousand man-hours with nothing to show for it and I'll wager that even a "herculean" 100-hour-effort will seem like nothing, if that's the price for success.

There are useful data on this subject available; let me know if you're interested.

Ya, I'm interested. Could you tell me about it?
 
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Sure!

A few sites:

[disallowed by forum; think I have one more post to go]

That last link is to actual instructions on the subject, and all these resources offer possible sources for rare-earth magnets to use.

There is valuable exposition explaining the advantages of building your own alternators; but they also discuss the best to use if you simply must buy.

The how-to instructions also feature a very clear explanation of how to wind an alternator for three-phase power--- I think that what can be learned here is applicable even in parts; say, if you'd like to rewind a purchased alternator, or replace its magnets, to increase efficiency without having to make the entire thing.

The 'otherpower' guy has been at it for some years now--- I think it is his site that I first saw a few years ago which turned me on to this whole idea. All the resources listed are very much focused on real results and real output; there's very little 'armchair engineering' going on here. I know it can be very disappointing to do a lot of work for little-to-no results; these people will give you a solid foundation and real-world results to base your designs and work upon.

Hope it's helpful.

(I will have to try again, the forum wouldn't allow the URL's to show)
 
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