Author Topic: Perfect Windmill Design?  (Read 5598 times)

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Yianie123.

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Perfect Windmill Design?
« on: July 16, 2014, 12:34:53 AM »
Is there a perfect wind turbine design that is supreme?  My understanding is that  Permanent Magnet Alternators seem durable, corrosion resistant, great bearing life, but low power capabilities.  Axial  Flux, is just the opposite.  Looking for the perfect wind turbine design for high power and no maintenance that can stand up to ocean breezes.   Any information will be appreciated.  Thank you

Flux

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Re: Perfect Windmill Design?
« Reply #1 on: July 16, 2014, 03:56:30 AM »
To avoid confusion a permanent magnet alternator is any alternator that uses permanent magnets for the field, that includes the axial machines.

I suspect the things you are comparing are radial flux, iron cored alternators.

Are you by any chance looking at small machines suitable for use on boats?. Some of the commercial wind farm machines are permanent magnet radial field, iron cored machines and have outputs in the MW range, not particularly low by your definition.

I think we are talking about direct battery charging machines without electronics in your comparison and it is true that iron cored machines do flatten off to constant current in high winds.

Everything is a compromise, nothing is perfect for any job but wind machines are more of a compromise than most.

For survival in marine environments there are advantages to having everything enclosed and away from the salt spray so I would agree that the radial machine has a big advantage here.

For the rest it is a compromise between cut in wind speed, size ,weight and maximum output. It is always the case that going for good low wind performance really knocks the performance in high winds.

In marine environments the wind speeds tend to be higher and rated power can be at a higher wind speed than on most land sites. You have to choose whether you want any output in winds below 10mph or whether you want higher maximum output power on very windy days. you also have to look at survival during storms. If by marine you mean on a boat then it is not easy to use furling schemes designed for land based machines.

Once you start looking at winds above 30mph, survival is more important than power out unless you are looking at something that only produces power in storms.

You can build small machines with a spectacular output in gales if you optimise the design for that but it will produce nothing most of the time.I can't help thinking from your previous comments that you are looking for incredibly outputs from tiny machines. In reality it is the snake oil brigade that make these claims and no realistic turbine designed for normal wind sites will even get close to these figures.

For marine environments I would look for an enclosed design, that doesn't rule out axial but it won't be in the usual open form.

If you want the best of all worlds then you need to go down the mppt route and the current limiting problem of radial iron cored machines then don't become a limitation and you can extend output up to wind speeds where prop speed becomes the deciding factor. Iron cored machines will never deliver the best low wind performance but if it is for a boat at sea this may be no big factor, if it spends a long time in harbour then it could well be a factor.

There is no perfect solution, just work out the best compromises for your needs.

Flux

joestue

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Re: Perfect Windmill Design?
« Reply #2 on: July 16, 2014, 04:33:54 AM »
i suggest a compromise is a 30 pole or higher, 36 slot motor conversion and use capacitors in series with the ac turbine to provide the power curve matching. the 30 pole or higher motor conversion should enable you to use cheap motor run capacitors rather than jerry rigged electrolytics which is a dubious setup in my mind.

the problem with the above, is you need 1/8th inch thick magnets that will cost you 20$ a cubic inch instead of the 7$ they should. you might be able to use one magnet for every two poles and use .25 inch thick magnets which will reduce that cost a bit.

the downside is you can short out the turbine and it will free spin with little resistance, because you have on the order of 1 pound of copper per cubic inch of magnet.

axial flux air core machines have about the same volume of copper as they do neodymium magnet, which is why they are so different than everything else.
My wife says I'm not just a different colored rubik's cube, i am a rubik's knot in a cage.

Yianie123.

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Re: Perfect Windmill Design?
« Reply #3 on: July 16, 2014, 07:56:30 AM »
I am not familiar with this 36 pole motor conversion.  Can you please direct me to information on this type?

joestue

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Re: Perfect Windmill Design?
« Reply #4 on: July 16, 2014, 04:18:09 PM »
My wife says I'm not just a different colored rubik's cube, i am a rubik's knot in a cage.

Yianie123.

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Re: Perfect Windmill Design?
« Reply #5 on: July 16, 2014, 09:55:50 PM »
Is building this type wind generator possible without specialized tools?

SparWeb

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Re: Perfect Windmill Design?
« Reply #6 on: July 17, 2014, 01:30:48 AM »
Quote from: Yianie123
Is there a perfect wind turbine design that is supreme? 

Yes.
Mine.

:)


Seriously...

What you're asking is a lot like:
"Which is better: BMW or Mercedes?" 
"Which sport is better, football or baseball?"
"Coke or Pepsi"
and so on...

Each is good, but nothing's perfect.  Something was compromised to improve something else.  What you think is best depends on what you want and need and prefer.  Don't let other people tell you what you want.
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
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Yianie123.

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Re: Perfect Windmill Design?
« Reply #7 on: July 17, 2014, 06:44:16 AM »
Please tell me about yours and how well would it hold up to corrosion near salt water.   Thank you.

SparWeb

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Re: Perfect Windmill Design?
« Reply #8 on: July 20, 2014, 05:57:04 PM »
Hi Yianie,

I don't blame you for misunderstanding, but I was kidding.  Maybe everyone thinks their own project is perfect, maybe most are humble enough to admit that any machine they build is a work in progress, and never will be perfect. 

When faced with reality, I know that my machines and I are far far from perfect.



No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
www.sparweb.ca

Yianie123.

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Re: Perfect Windmill Design?
« Reply #9 on: July 21, 2014, 10:01:14 PM »
Thank you for responding and the honesty.  What kind of generator did you have?

SparWeb

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Re: Perfect Windmill Design?
« Reply #10 on: July 22, 2014, 01:32:42 AM »
Here's my story:
www.sparweb.ca

The disaster above happened in 2009 or so.  Since then I have rebuilt my turbine (twice).
My current system sports a generator converted from an induction motor, fixed-pitch carved cedar blades, a tower 50 feet tall, and 3-phase AC rectified at the base of the tower into 24/28 Volts DC.  While I have found this system to be robust and faultless in the storms that pass through here, I wouldn't recommend my approach for an environment of extreme humidity or salt spray, as you have asked about.  There are just too many places for water to accumulate in my generator; it wouldn't last near the ocean.  I live on the prairies of Canada, where it is pretty dry most of the year, and cold for the rest of it.
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
www.sparweb.ca

Yianie123.

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Re: Perfect Windmill Design?
« Reply #11 on: July 22, 2014, 09:30:37 PM »
I like the permenent magnet alternators for the bearing life.  Is there anything that has the durability, but has low RPM POWER.

SparWeb

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Re: Perfect Windmill Design?
« Reply #12 on: July 22, 2014, 10:25:58 PM »
"permenent magnet alternators" is a pretty broad range of devices.
I have my own preferred type, based on the Zubbly conversions on induction motors.
The Otherpower pancake alternator is a scaled-up version of Hugh Piggott's alternators.
If you were to look up "fisher-paykel" motor conversion then you would discover another way to convert motors to use as wind turbines.
In between, there must be a thousand other ways to arrange the wires and the magnets.  Just look at the Ventera thread on the forum this week for yet another example.
Each has its plus and minus points.
The dominance of commercial wind turbine designs using the outer magnet drum turning around a stator core fixed to the hub shaft may prove that it's the the closest to "perfect" of all of these.

Do you want the most perfect?  It may also be the most expensive!  Careful what you wish for.
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
www.sparweb.ca

joestue

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Re: Perfect Windmill Design?
« Reply #13 on: July 23, 2014, 02:36:58 AM »
outrunner motors and generators serve a niche because the shape of the magnetic poles forms a halback array in a sense because the magnetic vectors are concentrated inward at the cost of their volume, to form a higher concentration of magnetic flux at the surface.

torque density of a motor is basically proportional to average air gap magnetic flux density squared.

so yes in theory the highest density generator would involve a halback array of N52 grade neodymium magnets but in practice out runners with C8 magnets are good enough.
My wife says I'm not just a different colored rubik's cube, i am a rubik's knot in a cage.

Yianie123.

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Re: Perfect Windmill Design?
« Reply #14 on: July 26, 2014, 12:48:48 AM »
That being said are the motors that can be converted easily to generators without the use of a machine shop and still get at least 1kw at low RPM?