Fieldlines.com || First time cut-in speed reached

Front Page - [Homebrewed Electricity-- (wind) (solar) (hydro) (steam) (controls) (storage) (mechanical)] - Classifieds - Site News
Everything - Newbies - [Remote Living-- (housing) (heat) (light) (water)] - Reviews - Diaries - Our Products

First time cut-in speed reached
By force9BOAT, Section Wind Posted on Sun Apr 16, 2006 at 06:33:31 AM MST
Working the bugs out

Hello,
A couple weeks ago I posted some photos of my new turbine (http://www.fieldlines.com/story/2006/4/6/4465/08215). After two weeks of waiting today we had a nice blow, including a hail storm and associated wind squall. At one point I think the wind may have hit 30mph. It's hard to tell but I think my turbine was up around 150rpm. For two weeks I've been watching the blades slowly turn in 5mph wind. This was the first time I've seen it reach cut-in speed (24V).
I have to admit disappointment. My ammeter was showing only about ½ amp at 24V. That would be all of 12 watts from an 8.2' foot diameter machine (dual rotor 24 magnets, 9 coils, 3-phase star) in a 20mph wind. I think something must not be right.
Back when I first built the stator (http://www.atm-international.com/RenewableEnergy/Wind/axial_flux_alternator_project1.htm) DanB told me I used too many turns (90 turns) in the coils. Dan suggested the blades would not be turning fast enough at cut-in and would be stalled. So what to do now? In the long term I may make a new stator and also increase blade diameter to 9 feet (from 8.2'). I'm wondering if two short-term steps might also help to increase charging current.

Change the stator from Star to Delta. I can do that because the coil connections are outside the mold.
Increase the air gap.
I'm thinking the above two steps would increase RPM and thus blade efficiency and hopefully charging current. Can anyone comment on this?
Also, as can be seen in the posted photos the turbine mast is secured to the side of my house. I was almost forced to take the turbine down after just one night of variable winds. Every time the turbine rotated to a new azimuth a loud metal against metal screeching sound reverberated through my house. Happily I was able to completely eliminate that problem. I happened to have some 1/8 thick Teflon sheets. I cut a circular piece just large enough to fit inside the turbine chassis sleeve. The Teflon pad is on the top of the mast and now when the turbine azimuth wants to change the turbine rotates on the Teflon pad. No more metal against metal scraping. For good measure I added some grease inside the sleeve as well. Now the machine rotates smoothly and soundlessly.
Rob

First time cut-in speed reached | 17 comments (17 topical)

Re: First time cut-in speed reached (3.00 / 0) (#1)
by willib on Sun Apr 16, 2006 at 12:59:46 AM MST

Hi Rob,
your blades are not right , i tried to tell you before .
you have a real nice machine there everything looks ok , except your blades .
they cant possibly produce any amount of power.
i would suggest before doing anything drastic to the machine itself , that you look into blade design..
Take a look at Dan's blades for his 17 footer . or any of his blades for his newer machines .
thats my suggestion.

Carpe Ventum (seize the wind)

Re: First time cut-in speed reached (3.00 / 0) (#3)
by Flux on Sun Apr 16, 2006 at 01:15:25 AM MST

I can't find enough data on the blades to form an opinion. The original 8 bladed thing would have been useless but I assumed that the 3 blade version was based on Dan's blades. I have never used and would never consider using laminated plywood but if it is made to the right shape it should work.

Perhaps in view of the poor performance some details of the blades would help Rob.
Flux

[ Parent ]

Re: First time cut-in speed reached (3.00 / 0) (#11)
by force9BOAT on Sun Apr 16, 2006 at 02:19:54 PM MST

Yes, I think you must be right. I have a summer project ahead of me now to make a new set of better blades. I've got room to increase the diameter a bit too.

Rob

[ Parent ]

Re: First time cut-in speed reached (3.00 / 0) (#2)
by Flux on Sun Apr 16, 2006 at 01:07:47 AM MST

You say you got 38v at 250 rpm on test, I assume this was ac volts between a pair of leads.
It agrees quite well with my calculated figure for cut in of 118 rpm, assuming the stator is about 1/2" thick.

This is too slow and it seems likely that delta will bring it up to a better figure.

Alternatively a fair size increase in air gap should bring the speed up.

If delta works, you may find Jerry rig is even better as far as efficiency goes.

I have no real doubt that your problem is the wind or the lack of it. There is no chance of output with wind from or towards the trees. I have no idea what things are like when it blows up or down the road. It is all too easy to have a lot of violent squalls in such places without having any serious energy at all. If you got 1/2 A with it stalled, you may get 3 times that when you raise the cut in speed.

Unless you have better wind prospects in other directions, you will never get very much and increasing the air gap may be as good an option as connecting to delta but you have both options to try.
Flux

Re: First time cut-in speed reached (3.00 / 0) (#8)
by force9BOAT on Sun Apr 16, 2006 at 10:17:51 AM MST

Flux,

What is "Jerry rig"?

I was in a hurry to get the turbine working so lamited up the blades. I didn't really understand blade design at that time. I think I will have a summer project to make a new set of blades.

The strong wind blows directly into the trees from the turbine. My wife has wanted to cut them down for years and I wouldn't let her. Maybe I'll change my mind.

This has been a learning experience for when we move. We have a vacation cottage on the beach that gets a lot of strong wind with no obstructions in the way. We hope to retire there in a few years. That's where I want to really use the turbine.

Thanks again,

Rob

[ Parent ]

Re: First time cut-in speed reached (3.00 / 0) (#9)
by Flux on Sun Apr 16, 2006 at 10:53:56 AM MST

Jerry rig is where you connect the ends of each phase to a single phase bridge rectifier and connect the dc terminals in parallel. It has the same voltage ratio as delta but is less affected by harmonics circulating in the winding.

Look at Jerry's diary,he has been proposing the idea for years and we seem to named the idea after him.

I am suspicious of your blades, you seem to have built a bit of twist into them when you laminated but it can't be very much. Have you made any attempt at an aerofoil on the back surface.

When you showed it in the park you said it turned at about 120 rpm for about a minute and then took off. This seems to indicate that you have very little in the way of pitch and that is not what you want in a poor wind area.
Flux

[ Parent ]

Re: First time cut-in speed reached (3.00 / 0) (#4)
by tecker on Sun Apr 16, 2006 at 02:46:16 AM MST

When you have torque / stator problems . You can get caught up in a frustrating ring .It's a good idea to take everything back to the bench and jig the alternator up , get some scope shots to see if the phases match well and what the output is under load etc. You have some flexablity there with the connections exposed . You don't talk about the load there I assume it's the batteries you spoke of in an earlier post .

Re: First time cut-in speed reached (3.00 / 0) (#5)
by commanda on Sun Apr 16, 2006 at 02:48:15 AM MST

It is my considered opinion that you need far more chord width at the root. Plug your data into either warlocks or alton-moores blade calculators. For an ideal (mathematically) blade ,the root chord should be about 5 or 6 times the tip chord width. In the real world, this is rarely achievable.

In your location, a chainsaw taken to those trees behind the house would probably advance your cause, but may not be politically correct.

Amanda

Re: First time cut-in speed reached (3.00 / 0) (#6)
by zubbly on Sun Apr 16, 2006 at 05:32:45 AM MST

hello Force9Boat!

from what i can see, i think your biggest problem is all the trees.
let me tell you about my genny. its a 1.5hp conversion with a 8 foot 3 blade prop, mounted on a 30 foot tv tower with about 6 feet of mast pipe sticking out. i have 2 large trees and the house to contend with. the only time it runs good is when the wind is from the south west. it gets a clear stream of wind then and is pretty steady.

when the wind is from any other direction, it is constantly yawing all over the place trying to align itself with the wind. the trees and house just plainly cause the wind to be erratic, and it rarely gets going fast enough to even hit charging volts.

the other day we had a good wind from the south west, and was getting 42 amp peaks into a 24 volt batt bank, and was averaging about 25 amp. i have seen it hit just over 70 amp in a wind storm.

basically, your genny is only going to perform as good as the quality of the wind. you look like you have a great genny there and unfortunately i think your only options are going to be to move it to a new location or just plainly get it up above the tree height.

good luck!
zubbly

Re: First time cut-in speed reached (3.00 / 0) (#7)
by picmacmillan on Sun Apr 16, 2006 at 06:15:13 AM MST

hi forceboat....i am siding with all the rest that you have 2 things wrong(and all the rest is right)...i have almsot the identical turbine...i had built my first set of blades following hugh piggots book, but they did like yours are doingand couldnt catch the wind..they worked, but rather poorly for my area which didnt have good wind...i made another set(wider), from 2x8's ..i had the tips wider,and of course the root was wider also...i used a 4 1/2" angle grinder to carve out the root...these second set of blades(danb's design), worked real well, and i kind of stick to that train of thought now(wider)..i also had some trees causing me grief and didnt realise it off the hop, but since i put the genny up higher, out of the turbulent air, i have had great success......i believe you have a real good design there, just have to weed out the couple problems you are having, and you will be off to the races :) pictured below is the turbine with the skinny blades..

picture below is blades with danb's design ..lots of difference :)

good luck..nice job on your turbine...pickster
http://www.frecklefarmloghomes.com

Re: First time cut-in speed reached (3.00 / 0) (#12)
by force9BOAT on Sun Apr 16, 2006 at 04:54:12 PM MST

Pickster,

Thank you for sending the photos. I am inspired to make new blades as a summer project. First I'm going to do some more blade research so that I get it right next time. I'm also going to change the stator from star to delta to get the cut-in RPM up.

Rob

[ Parent ]

Re: First time cut-in speed reached (3.00 / 0) (#10)
by Sue Karber on Sun Apr 16, 2006 at 11:19:21 AM MST

I read your construction article and picked up on the magna sand that you used for stator construction. In my opinion, anything attracted to a magnet (since you harvested the sand with a magnet) is detramental to power production when used in the stator. Nice project wish you success. Harold & Sue

Re: First time cut-in speed reached (3.00 / 0) (#13)
by willib on Sun Apr 16, 2006 at 07:32:23 PM MST

"anything attracted to a magnet , is detramental to power production when used in the stator"

Not true exactly.
as anything having to do with magnetism the shape of what you put in the stator is critical to its usefullness.
as an example , look at induction motor conversions. lots of laminated steel, that is shaped to direct the flux through the coils.

i've done some testing on this a couple of days ago ,and when the rotors were presented with a strip of copper , parallel to the magnet faces the drag was what you would expect , but when the same strip was rotated 90 degrees( perpendicular to the magnet faces ) the drag was considerably less to non existant , when in direct maximum flux . except near the perimeter of the rotor , which was strange ??..the strip of copper is 1.5" x .4 x .025"

Carpe Ventum (seize the wind)
[ Parent ]

Re: First time cut-in speed reached (3.00 / 0) (#14)
by seanchan00 on Sun Apr 16, 2006 at 09:25:55 PM MST

Hi Rob,

SeanChan here from Malaysia. I am a raw beginner who have been frustrated and disappointed by my wind genny since I erected it on a 53 feet tower in November 2005. My alternator is 12 inch dual rotor 12 magnets 9 coils as yours using 2"x1"x1/2" neos bought from Otherpower. My coils are however 35 turns of dual strand 1.5mm magnetic wires for my 12 volt charging. My blades are Hugh's design at 8 feet 6 inches diameter made using 2 by 6 inch lumber. I only have some trees about 120 feet away and yet it causes much turbulence. Most of the time when the trees are waving in the wind the speed of the blades are not producing power, just hitting short of 12 volts DC. Too often I feel good wind at ground level and the tree tops leaves are moving but the wind gen will only be turning one direction then another and the blades won't start. Only when the tree branches start to wave will the blade start. I have been power hungry since it has been up.

To cut the my story short, basically I am in a poor wind area and some trees quite far away added turbulence to make matters worse. While waiting to finish my new 11 feet diameter blades to be made with 170 cm by 4.5cm lumber using Alton's blade calculator to TSR 7.5, I decided to extend the present 8.5 feet using 3 pieces of 18" lumber measuring 2" by 4". I bolted the root of my blades to these 3 pieces and effectively extended to 10.5 feet diameter. This was done only yesterday and there was no wind. I was very surprised to see the blades turing slowly and looking up I then saw the tree leaves gently moving. So now my blades will start to turn even in the slightest wind and I am very confident I shall finally be getting meaningful power. I have also closed the air gap yesterday.

From my limited experience, we both have alternators more suited to 9 to 10 feet diameter blades in good wind area. In poor wind conditions we probably need a little longer say 11 or 12 feet. You can see my wind mill at this link.
http://www.fieldlines.com/story/2006/2/26/21156/5171
I am sure you will get better results with a set of better blades and at least 9 to 10 feet diameter. Then if need be make a new stator later.

SeanChan.

Re: First time cut-in speed reached (3.00 / 0) (#15)
by willib on Mon Apr 17, 2006 at 10:01:40 AM MST

Sean have you got any pics of the new blades?

Carpe Ventum (seize the wind)
[ Parent ]

Re: First time cut-in speed reached (3.00 / 0) (#16)
by force9BOAT on Mon Apr 17, 2006 at 03:22:19 PM MST

SeanChan,

Thank you for your reply. It's really neat to have communication with someone as far away as Malaysia. I saw your photos back when you first published them. I was really impressed with your tilt-up design tower. There appeared to be so much bend in the poll I was surprised it didn't buckle and break. After seeing your photos I strongly considered trying a tilt-up like yours with a counter weight but I decided I don't have enough room for it. I don't have any place to attach the guy wires.

I was also impressed by the beauty of your location. It looks so lush green and tropical. Looks like the Garden of Eden. Here where I live its cold.

Your comments about the turbine blades are very interesting and helpful. I'm glad you are seeing light-wind rotation. I would like to know how it does after the longer blades have been up a couple weeks. Your comments to me give me another reason to make new blades from scratch and make them longer. I've got room to make 9 foot diameter machine. Currently my machine is about 8.2 feet. I'm hoping the extra inches will help. Also, I think I will be cutting at least one tree down. The tree directly behind my turbine also blocks my telescope's view of much of the sky.

Looking forward to hearing more about your machine.

Rob

[ Parent ]

Re: First time cut-in speed reached (3.00 / 0) (#17)
by seanchan00 on Mon Apr 17, 2006 at 05:56:49 PM MST

Hi Rob & Willib,

I will post pictures as soon as the new blades are up. Will show the current extension also. As usual there is hardly any wind when I was in my farm last enening. Winds are usually blowing during midday when I have to be in my clinic. I will cut down more than ONE tree Rob if I am in your situation. Towards this year end say October when the moonsoon changes back to North-East I will chop half off the three remaining trees which still occasionally blocks partially, "top it off leaving half a tree". I wish to enjoy the durian fruits for this year, it's flowering now and the fruits is expected to drop in August.

Sean.

[ Parent ]

First time cut-in speed reached | 17 comments (17 topical)

Menu

� create account
� How to use the board
� FAQs
� search the board
� Google search the board

Login

Make a new account

Username:

Password:

Total Views

��168 Scoop users have viewed this posting.

You must be a registered user to post here. It's easy and free, and the link is on the upper right side of your page.
All trademarks and copyrights on this page are owned by their respective companies. Postings are owned by the poster, but may be deleted or moved at the ADMIN's sole discretion. The Rest � 2009 Forcefield.
You can Email the board ADMIN here. PLEASE include the username you signed up with!