10 kW Axial Flux Dual Rotor

[Andy Mac]

10 kW Axial Flux Dual Rotor

I was hoping to open a dialogue about creating a larger machine for people who are probably "on the grid", and would like or be able to create a larger machine. Personally I am far from this point but think it has a lot of merit, and I am fascinated to think that one day I will never pay for electricity again (HA!).

I do understand that the complexity, difficulty, problems, electronics, and expenses increase with size. I really think there is far more than enough of a talent/knowledge/interest base here for this post (in my humble opinion).

I don't know what the limitations are to the "Hugh Piggott" homebuilt design. The largest wind generator I found on the discussion board is was a 22' diameter machine posted by "Harrie" (http://www.fieldlines.com/story/2007/5/31/0531/34656), that was originally a 26'er, and was trimmed down to 22'er (a beautiful machine).

I am kind of curious as to the response I will get, I am mostly hoping for constructive criticism, which may not just state the problems, but also solutions, or ideas. I have seen a couple of posts from people who were very interested in trying a 10 kW build, and most of the responses seemed to try to shoot it down. But then again I am sure if there were rock solid plans on a 10 kW, there will always be someone wanting 12. So I will let the responses dictate any further posts.

Thanks for reading my post, as it is my first; I am Andy Mac, a SCSU student in my last 6 months for my 4yr, and a Navy vet. I got sucked in to the wind community through reading the "otherpower" website projects like a Neo magnet to a brake drum!

--Andy Mac--

[wdyasq]

First, as you imply, this is not a simple undertaking. I hesitate to put any information out on larger stuff as it will be similar to giving a kid interested in 'hot cars' a 485HP Cobra and a 12 pack of beer for a birthday present.

It will take approximately a 10m blade-set in a 40kmh wind to reach those power levels. This is definitely in the Variable Pitch range or full stall control method of wind machines. It will also take a large tower structure and electronics 'to be invented' to handle the power. All of these things take engineering expertise , structural, Aeronautical, mechanical and electrical.

Most likely, special laminated stators will need to be constructed. Special rotors will be needed. Probably a truck size hub will be needed if that is the bearing style chosen and it fits into the engineering parameters.

Blades will need engineering. This will be both for aerodynamics and structural qualities. If made of composites, fatigue testing should be performed.

After all of this is imagineered and created. It may need to be insured. That would mean all of the engineering would need to be done under a professional's ticket.

For these guesses, I am using the Wild Arse Guess method. Just the materials for the rotor and stator might cost $3-5k. The blades would cost $2-4k and the tower probably $2-5k. Total cost, not including labor will be a minimum of $7-15k not including electronics or batteries if chosen. A small (relativity) battery bank would allow 'standard' inverters to use the power or sell it to a utility.

That is quite a chunk to 'roll the dice' on as there is no guarantee it would work or, even could be created within the budget I suggest. IF such a venture was undertaken, one would HOPE the builder(s) would build some smaller mills progressing to larger stuff as knowledge was gained.

Ron

[finnsawyer]

I think you have to balance this type of project with what might happen in solar power generation.  I recently saw a TV program about a new development in solar.  The inventor had developed plastic and carbon based compounds that can be applied as inks to a substrate.  A number of layers with different spectral sensitivities are applied by a printing press.  They showed the press in operation.  Remarkable!  Well, the upshot was that the inventor predicted the process could bring the price down to ten cents per watt.  That would be $1,000.00 for 10 KW of power.  That remains to be seen, but it certainly would have a major impact on home based power generation if the cells had adequate life spans.  Wind power could not compete with that kind of cost.

[wooferhound]

The biggest Homebuilt that I know of is 30kw

and it's a total monster

http://www.fieldlines.com/story/2006/7/9/203732/5300

[DanB]

I think the generator on that (the induction motor?) was rated 30KW - but it's still only a 20' diameter machine so not really even close to a 30KW wind turbine unless very windy...

[wdyasq]

Bot on IRC gives:

24954.6 watts possible from 20.0 ft dia prop (314.0 sq ft) in 25 mph wind (density of 1.225000)- 3992.7 watts output assuming generator is 80% efficient and Cp of 0.20

Ron

[DanB]

You mean 24954.6 Watts available in the wind, before betz or any of that.  Yes, the figure of 3992.7 seems very realistic.

[Andy Mac]

Perhaps I am thinking 3 steps ahead with 10 kW. With 8 kW models being used and tested, I am sure 8.5 - 9 kW designs will follow (human nature?). Not sure of the limitations of the design before it starts becoming unreasonable. As for people that are "not" grid-tied, machines of this size seem to be of little use, so I am thinking this is generated mainly toward the grid-tied community. With power, and fuel prices unstable and increasing, many more people will be seriously looking at RE. 1 machine will always give you more bang for the buck over 2 (unless it breaks down). Space, materials, and time seem to be limiting factors.

As for the advances in solar, WOW, that is great, now I have something to paint the tower with! Seriously, I try to keep my finger on the pulse of new and upcoming technologies, and look foreword to everything I can find, thanks for the post! Is this along the lines of what Boeing Spectra Lab is working on?

I really look foreword to reading about larger sized genny's so that is kind of why I posted in the first place. There seems to be resistance towards this, and confuses me a little. I did notice a cliché among people who are new to this, we all want bigger and better, higher efficiency, etc.... and anyone in the know, knows what's involved. I am not at a point where I am going to try changing things up, I am at a point where I am going to do exactly what has been done before, and figure out why things are the way they are. My thoughts were one day I will be there, and this is where my interest is.

On a side note about batteries, there seems to be a lot of people out there that don't want to deal with the added cost, maintenance, disposal of batteries. I also still kind of think of battery integrated systems as a backup (don't mind the dark ages every so often). From what I have been reading they seem to be a necessity.

--Andy Mac--

[HomegrownPower]

Andy Mac

I'm experimenting with the idea of a bigger better pma lol . Of course I'm not considering trying to use blades to turn it . I'm a newbe to all of this and have tried to just about re invent the pma lol .

It will have the traditional 12 magnet  9 coil 3 phase wiring but will have two stators  of Number 13 wire . Their will be what I call an exciter plate between the two stators that have twelve 2 inch by 5/8 inch x 5/8 inch magnets .  No steel plate on the ectiter . The exciter will turn with both outside magnet plates that are constructed with 12 each neo's 2 inch x 1 inch x 0.5 inch thick . Mags in the exciter are just regular mags but do a nice job of extending the lenght of the flux field between the outer mag plates .

Both magnet plates and the exciter / attractor what ever you call it will mount on a 1 inch stainless shaft with end bearings . I'm about 1/3 done and everything absolutly everything to complete it has been purchased and I'm waiting for it to get here .

Worse comes to worse it will not work and I'll have to take it apart and remove my ( exciter ) lol and one stater . But I tried and it may just work . My plans for wiring the stators will be to have my starts and finishes wrap around the outter dia of the resen stater . feed them back to the center through straws placed in the casting and run each phase to a bus bar . Then reduce the 6 ends into 3 ends at 3 copper terminals to feed back out to where both stators can wire together .

I have a way to mount all this onto my drill press . It's the 50 year old style and heavy duty but only has a chuck size of 1/2 inch . I'll have to come up with a way to couple them together but standing the whole outfit on end I can use the drill to turn it for testing .

It has 8 different belt settings so I can start with maybe 30 rpm's all the way up to about 4000 rpm's . I'm hoping to get what I'm after with about 300 to 600 rpms. I chucked my first magnet plate into the drill and turned it true with it . It was a bit tricky to get a steady tool post set up but worked great for turning the outter edge true .

Will post pics soon with info on how it goes . If it works it will work . If not I'll take it apart and make it work and have extra parts lol

Lonnie

[Andy Mac]

That is awesome, I would love to hear how that turns out! I actually comented on something like this a few days ago, check it out.

http://www.fieldlines.com/comments/2003/9/16/85430/5911/11#11

I was wondering how much of an attractive force the 3 magnet plates would have on one another. Would this thing cog like crazy? Very interested to see how your PMA turns out.....

--Andy Mac--

[HomegrownPower]

Andy

I'm new to all of this but fail to see how an extra mag plate and stater could cause cogging but really don't know unless the actual electrical producing itself can cause it  .

I know on a little bitty PMA I have here about 2.5 inch in dia that I deffently feel what I'd guess to be cogging . However I really think it's just the neo's from hard drives attracting to the stater frame I used on this toy scale thing . I suppect a lot of cogging is really an attraction to sometghing the builder uses in their construction of the PMA . No experience to back that just a feeling I have .

So in all honesty I have no idea what it will do but will most certainly let you know how it goes . Who ever wrote that has the same idea as I do concerning how it should be done . With a steel plate in the middle would cause all sorts of problems ( I'd think )

But we will never know if we just think it up and never try it. Must follow through to learn what can be done . I think most never try this because with wind you can only do so much and to efficient may not even turn in a 15 mile an hour wind leaving you with nothing no charging where less efficient will trun good in even slower winds .

As far as the magnetic force man this is incredable . If you ever held two of the neo 42 in your hand of this size you get a new respect for their force field . They are plum dangerious .

The magnets in the exciter/attractor plate were just regular week mags . However in line with the other two neo's they provide an excelent boost to the flux field . Plenty enough to spand the gap of the second stator . I know they also charged up lol .  Thats what I'd call it I left them on the finished mag plate against the neo's . The next day I was playing around with the flux field trying to measure strenght at different distances . Point being after being slapped against the neo for a day or so I'm guessing the strenght was doubled .

I could be completly wrong I admit that but conclude from it all that the neo's are strong enough to keep the weeker mags in the middle charged to just about the same strenght .

Will follow up with pics if my wire for the stators ever gets here . Lonnie

[DanB]

Hi Andy -

'Perhaps I am thinking 3 steps ahead with 10 kW. With 8 kW models being used and tested, I am sure 8.5 - 9 kW designs will follow (human nature?).'

Yes - things do seem to move forward in that direction here.  I don't care so much to talk about 'kW ratings'  - swept area means a lot more.  I moved forward pretty slowly over the years... first building 3' diameter machines, then 4', 5', 6', 7', 9', lots of 10', 14', 15',16', 17' and then 20' and to be honest - although it's been fairly good so far with a couple hitches - the 20' machine I have still scares me a little.  To jump right in and build a large machine seems risky to me - especially if it's an all new design.

 'Not sure of the limitations of the design before it starts becoming unreasonable.'

I'm not either.  A couple things I do believe... alternator weight (magnets, copper and steel) is related to about the cube of the blade diameter.  Blade weight is similar...  

' As for people that are "not" grid-tied, machines of this size seem to be of little use, so I am thinking this is generated mainly toward the grid-tied community.'

Yes, my batteries - unless they are very low, cannot take what my 20' turbine has to offer on windy days.  Going any larger would be pointless.  Around here - for me - although I love free electric heat - I'm starting to think that electric heat is not worth the price of beating up my wind turbine.  I have lots of free firewood available!

'I really look foreword to reading about larger sized genny's so that is kind of why I posted in the first place. There seems to be resistance towards this, and confuses me a little.'

I think there is resistance here to new folks talking about building large wind turbines.  For one - most folks don't realize the scope of the project.  Secondly - it is an expensive and time consuming project and it seems unlikely to succeed if you're just jumping in with a new design...  with large turbines, and large towers - there are also some serious safety hazards if you overlook something.

 'I did notice a cliché among people who are new to this, we all want bigger and better, higher efficiency, etc.... and anyone in the know, knows what's involved.'

Yes - lots of people who are new to this don't realize whats involved and they don't  have a grip on the compromises we sometimes have to make between cost - efficiency - reliability etc...

And lots and lots and lots of people who are new to this want a VAWT to put on their roof ;-) that will erase their electric bill.

 'I am not at a point where I am going to try changing things up, I am at a point where I am going to do exactly what has been done before, and figure out why things are the way they are. My thoughts were one day I will be there, and this is where my interest is.'

Thats a realistic approach I think!  And even if you copy what somebody has done here remember that its probably only a 1 off machine and it's likely to have issues in the future.

'On a side note about batteries, there seems to be a lot of people out there that don't want to deal with the added cost, maintenance, disposal of batteries. I also still kind of think of battery integrated systems as a backup (don't mind the dark ages every so often). From what I have been reading they seem to be a necessity. '

If you can figure out how to grid tie without batteries (windy boy inverter or something) then youll gain lots of efficiency in higher winds.

[HomegrownPower]

Andy


I finally got my wire yesterday and made up 9 coils for one of the stators last night  . I'm just going to turn the coils around so the ends and outs protrude to the center as opposed to protruding outword and then feeding them back to the center like I first thought .

I will say that in most cases I'd agree with DanB 100% . I think he fairly well sums it up why most people should just stick with following a small well proven design . Especially if you were sinking all your bucks into what may or may not be the only electric you have .

In my situation I fail to see much if any risk . My lights will stay on wether this thing works or not . My wife may complain about the money but she will still get her cat food and the money to go to the store . And it may not work I understand that and I guess thats the risk . And it most likley wouldn't work without doing all the numbers and keeping it within those limits if you were depending on the wind .

I know I've mentioned wind , water and about everything else but my end desire is to end up with something that has  no dependancy on the wind . I really have no use for blades or a tower just a nice concrete pad and a belt drive from something .

I'll have to learn what rpm it runs best at ( assuming it works )and what HP it will take to do this  . I'll have to learn many things that seem like an enjoyable challange to me with risks I do not mind taking . I worry more about getting shocked than loosing a few bucks if it fails . I have a healthy respect for electricity and I like being safe with it and seriously doubt me getting shocked .

I hope my drill press works for testing . If so I'll be able to slowly up the rpm's untill I get my desired effect or chicken out one lol . It's a heavy duty old timy thing but it has some tork to it . I think it will work fine for spinning the magplates .

Back to the twin stator design . My theory was not to up the output of a single stator PMA  . From other post and reading from other topics I believe one stator would produce more electricity than I'm wanting or could use at this time ( at a given RPM ) . My desired effect for doing this would be to produce a good out put  with less heat and maybe even slower RPM 's  . I may not get the desired effect I'd like to get but that was my thinking for trying that .

To be honest I know of no way to know what I need without just building one and seeing for myself whats involved and wether it will do the desired job or not . I'll never know ( MY LIMITS ) either if I never test them so I guess thats the difference . I guess the challange of testing ( my limits ) are worth the given risks that come along with it .

Andy I'll let you know how it all goes . I will say if I was trying to build towers, props and (needed ) the electric produced to run something in my house I'd deffently listen to DanB advise . In that situation I agree with him 100% . A less efficient small mill from a proven design will make you much more electricity than a super PMA that for one reason or another will not produce . You could have the best , strongest most efficient PMA in the world and it would be useless if it took more wind to get it up to charge than the amount of wind that you have available  .

Lonnie

[HomegrownPower]

Andy

I think I posted your last reply to Dan hope you seen it . I just now noticed you can reply back to the person that wrote the comment .

Been working on the stators check them out and see what you think . I hope the 1/16 aluminum plate ( heat sink ) doesn't cause any problems . I was wondering if I shouldn't insulate it with a thin layer of cloth/resen .

 Using it mainly to get a good flat surface . I think to poor a 1/2 resen / cloth will sterdy it up when I remove it from the plywood . I hope it acts as a heat sink to vent off heat .

Looks like I'll have to solder the starts and finishes together . I wanted to use a bus bar but looking closer into that I could use three buss bars but they would have to have insulated terminals so all 3 phases could attatch to one buss bar .

I'm not going to that trouble I'll just solder them . I do think I'll keep my wiring in the middle and out of the way and just solder them and then run out from the center at what I call the foot of the stater .

It should all come together nice if I ever get everything . I have one magnet plate made but wanting to cast the second mag plates off the first one  ( center shaft and bolts ) in place in the first plate so I can get it lined up correct . I'll have to build plate puller within them ( just a stainless nut with threads so I can tighten bolts to slowly back off the mag plates to seperate  them .

My shaft, bearings and spacers should be here anyday and I can actually get started constructing this thing . If anyone knows of a problem using the aluminum plate PLEASE let me know now . It will be a few days before I poor it with resen and it would be great to know before I use it .

Lonnie
 

[wdyasq]

Homegrown,

I have yet to figure out why you are posting to this thread. I'm not following exactly what you are doing but you seem to be mating some copper coils to an Aluminum 'stator plate'. If this is correct, it is very bad practice.

The magnet plates MUST be ferrous material. I can't figure out exactly what you are attempting BUT, I think you need to do a LOT of research before wasting any money.

If you want good answers from your efforts it will be best if you start a diary defining your design and asking what needs to be done before you build yourself into a corner.

Some research into how magnets and ferrous and non-ferrous metals interacted with magnets should be understood before designing and building a generator or alternator. If not, it will be best to follow a KNOWN design EXACTLY.

These things aren't rocket science. The electrical parts do follow quite complex mathematical models that are beyond the abilities of most doctorates of math to calculate, even with modern computer aided calculus systems. The towers support many pounds/stones/kilograms of dynamic energy created by the lift of the blades.

This stuff can reach out and kill the best of folks. They are not toys.

Well, good luck and be safe,

Ron

[DanB]

Nice effort there but that aluminum plate (if it's part of your stator) is a big big problem.  You cannot do that - eddy currents will kill you.  (you'll see - put it together and try to turn the alternator!)

And like Ron said - you're magnet rotors must be of steel and the steel should be thick enough to do it's job (complete the magnetic circuit without being saturated)

[dinges]

He's soon going to find out about eddy currents the hard way.

He could find out the simple way by simply taking a magnet, rubbing it over the (supposedly non-magnetic...) aluminium plate and feel how much effort it takes.

(Ron: I used to have this physics teacher who, whenever he handed out a test, he wished us 'good luck'. Then, in a much quiter voice, mumbled 'you are going to need it'.)

Peter

[HomegrownPower]

Dan B and others

Thanks for that info I feel good that I asked before I actually fiberglassed it together . Your right I thought to use it with the stator as a heat sink lol . I'm not going to use it after being advised not to I'll take your advise and try avoiding these eddy currents .

 I seen no mention about making my wiring work out to the center of the stator verses the outside of the stator so I'm assuming this is acceptable providing all my coils are oriented correctly ?

A diary huh !! I see now start a diary and list my ideas / what I'd like to accomplish and hopfully get answers that prevent me from making screw ups like the heat sink on a stator before I do them lol.  Thats basically what I was attempting to do by posting here . I'm just so new to this and this place I wasn't aware the diary was the right place to post it . It  seems like many are reluctant to offer help if your ideas go out of the norm somewhat . That leaves me lonely lol as all my ideas are out of the norm for this site . Most designs here are for ( wind power ) and I'm needing someway to eventually run my PMA with natural gas .

My design basically follows the book with a few xceptions . With my bright idea of adding a heat sink to the stator being the most radical change . Most of anything else I've changed about the construction are basically ( un do able ) changes . What I mean is sure I might try using two stators with the insurance that if it fails for some reason I can simply remove one stator and have the same thing the book calls for . So hopfully most of any screw ups I could possably make are reversable screw ups .  

 About the magnet plate I'm  confussed .

I did my magnet plate just like the book said to using a steel plate with all neo's stuck to one side . Then used paper to make a mold around it and filled with resen like the car rotor guys do . I don't remember the book mentioning anything about saturating the plate though . If it mentioned that I missed it lol and have no idea how to tell if my plates are saturated .

 I used a 1/4 inch steel plate that has a dia of 11 and 1/4 inch . I just stuck the magnets in place ( to the plate )  and fiberglassed them in place . Yes I have them oriented north , south , north ,south and so on all the way around it .

Thanks again for the advise to $#|+ can the stator/ heat sink idea lol . I certainly understand the knowledge within this place could be valuable to me if I can tap into it . Thats the reason for posting asking the questions . I'm going to look at this diary thing and see if I can figure out how to get my questions / concerns posted in the proper place .

Thanks
Lonnie

 

[scottsAI]

Hello Andy,

Please see my study of a 10kw.

http://www.otherpower.com/images/scimages/3276/10kw_system_design9.pdf

The designed started out as PMA.

As I learned... it changed.

I wanted to have this reviewed before posting, nobody I contacted was willing to take the time to study and give useful feedback.

Consider it a work in progress and limited to my understanding.

I used wireless communications in the design, not required, something I work with so to me is easy considering the benefits.

Have fun,

Scott.

[Camburn]

I am a farmer in ND, NE corner of the state just a few miles from a major utility windfarm.  Most days I cuss the wind, can't spray or cold etc.

But anyways,  I want to build a 10KW machine to dry corn and wheat.  I have looked at commercial units but the cost is over 30K so not feasable.  I have the advantage of having a pretty decent shop, and a light knowledge of electricity.  The Navy was nice enough to provide me with that.

I had envisioned a 30' swept area to provide the energy to the generator.  Space is not a problem, and I am lucky that I think I can purchase a 100' tower from a neighbor who has a 25 year old generator on top of it and he wants to sell it.

From the thread it appears that people are scared of something of this size.  I am not scared but hungry for information.  I don't know if I should go with a permanent magnet gen or an induction.

Also, to comment on the fellow who is building a 10KW, as an idea......

Go to a truck junkyard.  Buy a rear axle, you can cut the tube and have a wheel bearing assmbly that will run in gear lube on preloaded timkin bearings.  A 3/4 ton pickup axle would be strong enough, and with the loads of a 20-30 sweep area it should provide adequaate structure to take the load of a sudden gust of wind.

Also, being it is a free floating axle, the axle can be cut, and the outer axle bolts could be used as the mounting area for the turbine blades.  Quit light but very strong.  I don't think that 1" shaft will cut it in the long run unless you are using stress proof, and even then a bit light.  Just an old farmer thinking of metal fatique.

LM fiberglass in Grand Forks makes the turbine blades for the big boys, but they would also make blades for us small guys with enough lead time.

Anyways, sorry for rambling, but I am looking for ideas and help.

Thank you so much to anyone who responds.

[scottsAI]

Camburn,

Found this a year after you posted! Only little longer than yours.

Send me an email if your still looking. Requires passing IQ tests.

I see this is the only post you have made??

Loose interest?

Have fun,

Scott.