Author Topic: Why not lots of cheap mills?  (Read 10223 times)

Offline mangyhyena

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Why not lots of cheap mills?
« on: July 07, 2011, 06:00:40 PM »
I noticed it can be fairly cheap to build a vertical windmill.  Saw one that was made with 2 halves of a 50 gallon barrel.  The problem with them seems to be small amount of power production, especially if used at ground level.  The major cost of a mill seems to be the generator/alternator unit, not the blades.  Also, putting a windmill high up on a tower looks like a major part of the cost.

So, I'm wondering if several of these cheap mills could be linked, at ground level, to just one generator/alternator.  Would several of these cheap mills working together equal one better built, more expensive windmill?  Why or why not, please?

Not challenging anything with this post.  Just trying to understand why I don't see multiple mills linked and working with one generator.  Thanks.

Offline TexDaddy

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Re: Why not lots of cheap mills?
« Reply #1 on: July 07, 2011, 06:14:56 PM »
I imagine it would be the cost and complexity of setting up the mechanics to have several windmills turn the armature of the generator.

On the electricity producing windmills I have seen, the blades are mounted directly on the armature of the generator. You would have to introduce drive rods and a crankshaft to hook several together to run the same generator. This in itself would reduce the power available to turn the generator. In addition, the head of the windmill would still have to be able turn into the wind, while keeping the upper crank and the drive shaft connected. Of course, that part can be done similar to the windmills used to pump water into cattle tanks.

Offline tipafo

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Re: Why not lots of cheap mills?
« Reply #2 on: July 07, 2011, 10:00:06 PM »
It shouldn't be that complicated.

http://en.wikipedia.org/wiki/Savonius_wind_turbine

One rotor turns one small alternator/generator, and the current is "ganged" together with an array of other small turbines.  The combined current flows through a charge controller/inverter and then to the main AC panel.  Similar to how individual solar panels are ganged up and the currents combined.

Something like this, but free-standing, made of metal, turning an automobile alternator/generator, should produce a useable current in a decent wind.

http://www.youtube.com/user/embeddedprogrammer#p/u/18/KnE_aVFxJQE

Of course, as with solar panels, it would require many such turbines to create a reliable source of electricity.  (Or mechanical power, as these "windmills" can also pump water, etc.)

I've not tried it, yet, though I've wanted to for years.

Offline TexDaddy

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Re: Why not lots of cheap mills?
« Reply #3 on: July 07, 2011, 11:53:56 PM »
That is a cool design, but each 'stack' would require its own generator. It doesn't address how to turn only one generator with multiple windmills. It does make it where wind direction is not a consideration. It would be interesting to find out how many could be stacked, but pretty soon you would have a tower/costly support structure, another thing the OP wants to avoid.

...The major cost of a mill seems to be the generator/alternator unit, not the blades.  Also, putting a windmill high up on a tower looks like a major part of the cost...

So, I'm wondering if several of these cheap mills could be linked, at ground level, to just one generator/alternator...

In the big commercial operations, the generators in each tower are "ganged" together and the currents combined for transmission.

Offline Perfesser

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Re: Why not lots of cheap mills?
« Reply #4 on: July 08, 2011, 12:24:46 AM »
I saw a guy who had many 3 bladed heads on a single shaft, maybe spaced 4 ft apart. Even in a light wind they did pretty well.
Found something like it if you want to investigate further.
http://www.speakerfactory.net/wind_old.htm
Scroll way down to the early models with 14" blades. He's also in an ideal location with 30 mph winds. Temper that with your probably closer to 5 - 10 mph.

I think this has a lot of advantages over a turbine with long blades. The gyroscopic forces escalate quickly when you increase blade length requiring a strong mount and tower, special blades. This design would have much less of those stresses yet still have good performance in low winds. If the blades are kept under 3 or 4 feet or so you could use the ones cut from 5" PVC pipe.
DIY- smaller scale, say 3 heads on a 10 ft. shaft, belt pulley in the center and run a generator off a belt.

Yet another project I wish I had time to pursue.

 
« Last Edit: July 08, 2011, 12:33:22 AM by Perfesser »

Offline mangyhyena

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Re: Why not lots of cheap mills?
« Reply #5 on: July 08, 2011, 05:19:55 PM »
In my head, which is a confusing & sometimes scary place to be, I saw the shaft coming off the generator at ground level with pulleys down it. At each pulley, a cheap mill was connected with a belt.  Even if each dirt cheap mill contributed only a little, I was thinking the cumulative power of all them working at once might make a usable amount of power.  The mills would be those vertical ones that catch wind from any direction without having to pivot.

Belts and step-downs might be too inefficient, though.

On a brighter note, I just came across some info on how to reduce the load from magnetic repulsion when running an alternator/generator.  The magnet that sweeps by the coil is round and is on a pole so it can spin like a record as it passes the coil.  That ability to spin as the coil's magnetic field repels against rotation is supposed to reduce the drag of the load without reducing the amount of electricity produced in the coil.  I'll have to play with this a bit, but it looks promising.  A windmill with reduced drag from alternator would make more energy, I think.
Just food for thought.


Offline tipafo

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Re: Why not lots of cheap mills?
« Reply #6 on: July 09, 2011, 08:30:04 AM »
That is a cool design, but each 'stack' would require its own generator.

Yes.  One turbine is an independent part of a larger array.  If one turbine goes down, the others still function.  Additional single turbines can be added as resources become available.  A turbine can be built from commonly available parts without too much specialized mechanical training.

Quote
It doesn't address how to turn only one generator with multiple windmills.

Well, I wasn't trying to address that concern, since it seems fairly Rube Goldberg-y, to me.  :o Overly complicated, that is.

Quote
It would be interesting to find out how many could be stacked, but pretty soon you would have a tower/costly support structure, another thing the OP wants to avoid.

Two or three rotors high (about 15 feet or so) seems to be a manageable size.

As a caveat, I'm currently on an acre of open-spaced land, and plan to build on my 40 acres of open prairie at some point, so space limitations aren't a concern for me.
« Last Edit: July 09, 2011, 08:35:48 AM by tipafo »

Offline Perfesser

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Re: Why not lots of cheap mills?
« Reply #7 on: July 09, 2011, 09:29:52 AM »
Vertical axis aren't very efficient and they don't spin fast. Each blade going downwind has to push the other blade going upwind. Sure you have the cupped half catching the wind but you still have to push the rounded part against the wind.
You have to gear it up quite a bit to get enough speed at the motor head to make any real power.
The faster your magnet passes the coil the more power you'll make. You have to get a car alternator to something like 1200 rpm to make power. A rewound alternator for wind turbine use or a permanent magnet motor will be a better choice.
This guy seems to know his stuff - http://www.tlgwindpower.com/

Thats why I like the multi blade horizontal.
The smaller the blade diameter on a horizontal axis the faster the blades will spin. Once you get the optimal blade length to get a good shaft speed for the average wind speed in your area you could simply put many blade heads to work.
I found that belt drives were the best option for a turbine.  The conversion losses were smallest and there is also the cushion effect of a belt vs a chain or direct drive.

Offline mangyhyena

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Re: Why not lots of cheap mills?
« Reply #8 on: July 24, 2011, 09:17:30 AM »
I was just wondering, so I posted.  I figured there must be a good reason this isn't a popular solution.

Offline Doug

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Re: Why not lots of cheap mills?
« Reply #9 on: July 24, 2011, 11:08:25 AM »
I have two SkyStream. If I were attempting to go off grid with my current consumption I'd need 8-10 of these things. They don't produce as much as some claim. That said....

...I've wondered about different ways to hook up a generator system since I think it'd be better to have the generator at ground level for maintenance.

If I were attempting to link multiple turbines to one generator I look to do it through some hydraulic system. Just to use an example: you could link traditional wind mills for pumping water to a water circulating system back to a gear box. You'll need a gear box since the generator needs to spin at a high enough rpm.

Offline mangyhyena

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Re: Why not lots of cheap mills?
« Reply #10 on: July 25, 2011, 07:35:01 AM »
Doug, that sounds like an interesting idea.

If you were going to pump water, would pumping it to an elevated holding tank be a better or worse use for the mill's energy, do you think?
Set up a hydro-electric unit between elevated tank & lower catch tank?  Mills pump water from lower tank to elevated tank?

Probably a ton of wasted energy in that setup.  It would, however, make the wind energy from one day usable at a later time, when no wind is blowing.  Guess the elevated holding tank would act as a battery to hold potential energy, which could be converted to electricity on demand.

Along that same line, weights could be raised using the mills.  Weights dropped at a later point to generate electricity?

That would probably complicate the system & be inefficient.  Not sure what, if any, advantages would be gained.


Offline Doug

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Re: Why not lots of cheap mills?
« Reply #11 on: July 25, 2011, 09:47:38 AM »
I've thought about that but the cost, the volume, and the height requirements doesn't make it practical to me. A good size wind mill has the capacity to lift a column of water 600'. That's a lot of usable pressure.

Looking at a new aeromotor (http://www.aermotorwindmill.com/Products/CompleteMills/Index.asp) a 16' diameter windmill runs about the same cost as an installed skysteam. So to make it worth it you want to buy used windmills and do the construction yourself.

Offline Rorschach

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Re: Why not lots of cheap mills?
« Reply #12 on: July 25, 2011, 08:07:01 PM »
Placing multiple turbines too close would create an efficiency problem
(http://www.popsci.com/technology/article/2010-01/wind-turbines-leave-clouds-and-energy-inefficiency-their-wake).  Keeping things connected at a distance is expensive as mentioned by others in this forum.

Offline Greysen

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Re: Why not lots of cheap mills?
« Reply #13 on: November 12, 2011, 12:16:25 PM »
The pumped water storage idea has actually been around a long time, and is probably one of the best ways to be able to "regulate" consistant power out of a wind system.   The problem of course is that it's used on a massive scale to store all that potential energy for power conversion.   You'd need to have a very large elevation change in your property as well as a lot of land to really make it work.

http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity

I think the multiple turbines idea is good if well spread out, particularly from a redundancy standpoint.  I can't think of a way to make it work off of one generator though short of the above solution.   The efficiency loss and cost of some Rube Goldberg type contraption would probably make it cheaper just to put up a couple mills :/

Offline mangyhyena

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Re: Why not lots of cheap mills?
« Reply #14 on: August 05, 2012, 01:06:04 PM »
In my head, which is a confusing & sometimes scary place to be, I saw the shaft coming off the generator at ground level with pulleys down it. At each pulley, a cheap mill was connected with a belt.  Even if each dirt cheap mill contributed only a little, I was thinking the cumulative power of all them working at once might make a usable amount of power.  The mills would be those vertical ones that catch wind from any direction without having to pivot.

Belts and step-downs might be too inefficient, though.

http://www.speakerfactory.net/wind_old.htm


So, maybe I wasn't so off-base with my thinking after all.  That link shows a windmill with multiple blades added for a gain in power production, all from one axel.  This is the basic principal I was trying to bring up for discussion, though this setup is less complicated than what I had in mind.

If one has the room/land, perhaps this setup could be used for a ground-level or low elevation windmill that can produce a usable amount of power.

Offline LdMorgan

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Re: Why not lots of cheap mills?
« Reply #15 on: October 28, 2012, 07:26:55 AM »
Ganged systems do work, if they are approached right.

A solar panel is just a gang of solar cells.

If it is more practical to have ten small windmills, use ten.

Don't think they all have to be synchronized or connected together.

If they output electricity, the electrons can be sent where they need to go. Ditto for water.

A 15 MegaWatt wind turbine will can be more "efficient" than a hundred 0.15 MegaWatt mills from many viewpoints--and less from many others.

What is the most practical solution for your back yard?

Go for what works well enough, and don't waste your time chasing the mirage of greatest efficiency.

A lot of people are still plowing with oxen because that works well enough, for them.