Author Topic: Prototype Oil Drum wind turbine  (Read 6817 times)

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gsw999

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Prototype Oil Drum wind turbine
« on: November 30, 2016, 03:04:17 PM »
Hey guys I used to post on here a long time ago hope you are all well, I have the wind buzz back and I have been trying ( and are still in the process ) to build a VAWT type wind turbine using an axial flux style generator and a chain based gearing system , the wind has calmed down here a lot but will be back up soon for the winter months.

This is a video of the turbine assembly a couple of weeks ago with no chain / drive gear attached had a bit faster wind and the old girl was swinging round hard but was super super stable!!!

https://www.youtube.com/watch?v=IzDJ1EXDHDE

Also in the above video it's worth noticing I have the blades / Drums slightly wider , whereby the central shaft (17mm mild steel ) can be seen , at the moment I am running it with the drums in a tighter configuration whereby the drums "overlap" and cover the central shaft , the stator housing etc will all be adjustable.

as for the gearing system this is an important experiment I want to share , this next video is from today which has a mock up of how the system will operate , it is running a very high ratio ( 26 drive to 9 driven ) and I was suprised to see it turning very slightly in about a 4-5mph wind.

https://www.youtube.com/watch?v=ka0PSHAbHaw

I have a lot of ideas about flywheels and weights to try and increase the torque within the system.

Nearly everything here is scrap I got from jobs in the past , I hope it's ok to share the videos , I appreciate peoples comments etc, shame I had to paint the oil drum but they stood out a bit with the texaco logo on them , I might paint it back on a different colour than red, also if you want to see my regular updates subscribe to my channel.

I am waiting on my magnets which will be here soon and then I will build / balance the rotors build a stator then try and produce some power , the alternator assembly will be build to go into a HAWT turbine if this project is a failure , I hope it won't be and may look to setting up another drum along side and I am also designing wind deflectors.

Everything is an experiment!!

peace


Gavin

SparWeb

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Re: Prototype Oil Drum wind turbine
« Reply #1 on: December 01, 2016, 08:25:02 PM »
Welcome back.
Nice to see you're still having fun  :)
Let us know how it goes when some serious wind hits it.

I think you should paint some psychedelic colours on it and really catch people's eyes when it spins!
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, regulated by Xantrex C40, DIY 8ft diameter wind turbine, regulated by Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024

gsw999

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Re: Prototype Oil Drum wind turbine
« Reply #2 on: December 02, 2016, 08:40:42 AM »
bright orange and pink it it then :) Im waiting on my magnets and wire there should be some good wind next week , been 4-6mph for the last few days :(

hiker

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Re: Prototype Oil Drum wind turbine
« Reply #3 on: December 02, 2016, 10:08:13 AM »
Cool...what size of mag rotors?  Wire size? Turns? Take a few test coils no dout..looks like fun.😜
WILD in ALASKA

gsw999

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Re: Prototype Oil Drum wind turbine
« Reply #4 on: December 02, 2016, 03:36:45 PM »
The rotors are the hugh Piggott style 12 mags , 50*25*10mm,the coils are 14 awg 70 turns ( or will be when I have made them ) , I have 1kg of wire here and 4 more kg on order hoping that will be enough , I made a wind turbine years ago but the wind here killed it ,  it is the same stator they use for the 10 foot wind turbine on the , the drive gear is 26 tooth and the receiver gear is 9 tooth , I was surprised when it started turning , I know it will need more oomph to turn under load but it really does catch the wind very well, I don't expect it do start moving til 10mph but things will start moving rapidly after that , wind turbines are so addictive though , like crystal meth for geeks:)

I think it will max out at 70-90 turns a minute , which will equate to 200-230 rpm at the generator all hopefully very stable I spent a lot of time making sure the bearings were perfectly centralised its a proper tough setup.

george65

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Re: Prototype Oil Drum wind turbine
« Reply #5 on: December 02, 2016, 04:15:00 PM »

I like this style, Nice and simple and practical.
I was wondering, If you took another rotor just like you have and stacked it on top at 90o so you had effectively 4 blades, would this make the unit more powerful or are there some other forces at work with these things that would make that not practical?

The low cost and simplicity of these things would make stacking them real appealing to me if there wasn't some reason it would interfere with the operation.
It would also seem with your setup, if one were so inclined it would be easy to build another turbine section and have that driving the same alternator in the middle of the 2 rotors.
Might give a lower kick in speed or more output at the same wind speed and maximise the investment in the alternator which would seem to be the expensive and difficult part. 

Look forward to seeing how this goes.

gsw999

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Re: Prototype Oil Drum wind turbine
« Reply #6 on: December 02, 2016, 05:44:04 PM »
I have scribbled down some designs for how I would use two drums, the wind has been stagnant here lately when it gets going it smashes it round here, there are lots of poss ways even have thought of putting two up on a tower but I would probably go for like a capital letter H on its side . if you stack two on top of each other how are you going to stabilise the top bearing , this is very stable because the four bearings are all in a perfect line and as long as you spirit level and adjust the frame it will always be very keen to turn.

electrondady1

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Re: Prototype Oil Drum wind turbine
« Reply #7 on: December 03, 2016, 05:46:30 AM »
if you increase the dia. you will increase the torque but reduce the rpm .
better to add more buckets vertically.
that will keep the rpm up but double your torque.
 
you should build a test coil to see how may turns required at the rpm your machine will turn.
copying Hugh Piggot design is cool but his coils are designed to work at the rpm range of a horizontal propeller style mill.


gsw999

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Re: Prototype Oil Drum wind turbine
« Reply #8 on: December 03, 2016, 03:50:12 PM »
Yeah I have just done a test one, I have some smaller wire that I recycled from washing machines but it's not straight etc , would be interesting to see the results with 2 strands of thinner wire.if you add more buckets vertically then you have to make sure the top bearing is secured in some kind of frame.

george65

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Re: Prototype Oil Drum wind turbine
« Reply #9 on: December 03, 2016, 10:16:20 PM »

Not sure what you see the problem being with a vertically double stacked  turbine.
Put a piece of support going across the middle between the 2 rotors and put a bearing top and bottom of each so each rotor has a bearing top and bottom on a common shaft.
Just as much stability as a single rotor.

MattM

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Re: Prototype Oil Drum wind turbine
« Reply #10 on: December 03, 2016, 11:37:39 PM »
Only a single axial rotor wouldn't have torsion issues like the vertical stack

george65

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Re: Prototype Oil Drum wind turbine
« Reply #11 on: December 04, 2016, 06:10:48 AM »
But it would have the exact same distance between the exact same number and spacing of bearings.

Any sort of decent frame structure with a decent shaft  diameter would be fine. The load on each shaft would be the same as a single stack but if you are talking about the actual twisting torque applied to the shaft, I reckon a 1" tube would kill it.

If my mates performance car can do 500Hp and more ft lb of torque through a 2.5" tail shaft 2m long, a 1" shaft supported at less than 1.5M spacing would handle the few ft lb a double turbine would generate with no problem. 

gsw999

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Re: Prototype Oil Drum wind turbine
« Reply #12 on: December 06, 2016, 10:55:24 PM »
Thanks for your input I appreciate it, bigger frames cost money which I dont have at the moment , I just spent my last funds on magnets and wire but would certainly entertain more drums at some stage and I am jotting stuff down , cheers.

Mary B

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Re: Prototype Oil Drum wind turbine
« Reply #13 on: December 07, 2016, 07:19:15 PM »
Stacked 90 degrees off adds better startup too in low winds...

electrondady1

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Re: Prototype Oil Drum wind turbine
« Reply #14 on: December 07, 2016, 09:01:23 PM »
consider this,
 plastic barrels have a great deal less mass that steel drums.
 

gsw999

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Re: Prototype Oil Drum wind turbine
« Reply #15 on: December 08, 2016, 04:19:01 AM »
that is the exact reason I have gone for metal , Less mass is not better, more mass = more torque = more power ,I am looking for torque above speed, not sure what you mean Mary B you mean more than one drum? thanks

electrondady1

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Re: Prototype Oil Drum wind turbine
« Reply #16 on: December 08, 2016, 05:57:50 AM »
by that reasoning you could you could dip your vanes in concrete or bolt on some lead ingots.
lite and strong is what you want .


george65

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Re: Prototype Oil Drum wind turbine
« Reply #17 on: December 08, 2016, 07:39:40 AM »

Torque would be a product of the strength of the wind and the area of the blades.
Inertia and to a degree, drag will be a product of weight.

The heavier the blades the more resistance they will have to turning in light winds. Also greater bearing loading which may cause more drag through greater friction.   Where a light blade might start spinning in a 5 Mph wind, a heavy one might not turn till say 10 Mph. For a given blade area, it would definitely make for a higher kick in speed over a lighter blade.

In a 15 Mph wind, the torque applied to the generator will be the same for light and heavy blades given their area is the same.
That said, the resistance of the alternator may over ride that but a heavy blade sure as hell won't help anything.

What the heavy blade would do is once spinning, would be more stable in gusts, keeping a more uniform RPM. Might help carry through the highs and lows if that's the sort of wind experienced in the area where the turbine is placed.
Over all though, I believe the losses would be greater than with a lighter blade.

It's like the amount of force to make a car roll along a flat road Vs the amount of force needed to push a railway loco. Going to need a lot more force on one than the other but if you give them both the same then the energy will also be the same.

In a more practical example, If heavy was better, They wouldn't make the giant commercial turbine blades out of lightweight materials like carbon fibre and the like and undertake all the problems of transporting the things.  They would make them out of concrete and cast them right on site.

To get more torque, you increase the blade area, IE, double stack, double pair etc. The wind is a fixed parameter in you can't change how hard it blows, it's out of your control and will be what it is for any turbine. What you can change is the blade area and that will also change the amount of torque you get and the amount of power you can therefore generate. 

On the face of it, plastic drums may be better from a longevity and maintenance POV. Won't rust and you don't have to paint them to stop it.
I have had some of those blue plastic drums sitting in the open for over 10 years and they haven't even faded yet.  I have also got metal drums sitting next to them.  Not a whole lot left. Top and bottom has rusted out even though they once contained oil and had a good coating on the outside as well and the sides are pretty ventilated as well.

having a double drum would get better returns on your investment particularly the alternator side. If you are short of funds to do that now, perhaps you could look at constructing the turbine section so you can add to it later when funds allow? The turbine side would be the chap part, the alternator is where the bucks are and the more you can get out of those bucks invested, the better.

gsw999

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Re: Prototype Oil Drum wind turbine
« Reply #18 on: December 09, 2016, 06:27:37 AM »
Hi thanks guys for your comments , this is where I'm at

https://www.youtube.com/watch?v=Cc0ZPWmJjyw&t=76s

the Chinese magnets I bought turned up at 24mm instead of 25mm , you really do get what you pay for , I wanted to go for 16 magnets *2 and 12 coils but now I have 28 magnets with a 24mm width which is a pain because I have a laser cut template , so anyways I don't know when I will be able to do it , if I just go 24 magnets I will get it dont this weekend so I may just do that as a test.

It sure picks up in the wind though was 12-15 mph approx , it basically is like this all winter once it gets started.

Cheers

Mary B

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Re: Prototype Oil Drum wind turbine
« Reply #19 on: December 09, 2016, 04:01:22 PM »
Stacked vertically, add another set on top but 90 degrees out of line of the bottom set.

that is the exact reason I have gone for metal , Less mass is not better, more mass = more torque = more power ,I am looking for torque above speed, not sure what you mean Mary B you mean more than one drum? thanks

Adriaan Kragten

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Re: Prototype Oil Drum wind turbine
« Reply #20 on: December 10, 2016, 01:01:58 AM »
What I have seen on the video is not a Savonius rotor as for a Savonius rotor both blades are overlapping each other. Information about measurements performed on a Savonius rotor is given in my free public report KD 599. For a Savanius rotor both lift and drag contribute to the driving torque and the maximum Cp therefore is about 0.2. What you have made is a pure drag machine. A pure drag machine has a much lower maximum Cp than a Savonius rotor. Information about drag machines is given in my free public report KD 416 (see www.kdwindturbines.nl at the menu KD-reports). My advice is, don't make Savonius rotors or drag machines as the generated power will be very low and the used amount of material will be very high.

Ungrounded Lightning Rod

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Re: Prototype Oil Drum wind turbine
« Reply #21 on: December 11, 2016, 12:16:54 AM »
I looked at this about six years ago and came to the conclusion that a Savonius using the Benesh blade profile (from patent 5494407) might have about the same power output as, and a substantially higher power-to-dollar ratio than, a horizontal axis machine of the same diameter, as well as being simpler to build. Since that time the patent has expired.  B-)

The Betz limit on coefficient of performance is about .593.  Though in principle a really good set of HAWT blades at a TSR of 8 or so could get close to that, actual designs typically top out at about .5.  A two-hemicylinder Savonius tops out at .244.  But a Benesh savonius comes in at .37.

Now .37 is still quite a bit below .5.  But the ratio of the two is very close to 4/pi.  A horizontal axis machine of radius r (diameter 2r) sweeps a circle of area pi r squared.  A savonius sweeps a rectangle of 2 r times h.  If the height h is the same as the diameter, the swept area is 4 r squared.

So the power collected by a Benesh / "Sandia" savonius presenting a square cross-section to the wind is (4 * .37) / (pi * .5) = .9422 times that of a good horizontal axis machine of the same diameter.  Make it 6% taller than it is wide and it's a wash.

Then consider that the Benesh-profile savonius only needs ONE set of bearings (not three: prop axis, yaw axis, autofurling tail axis), doesn't have to track the wind, doesn't have to be furled to protect it in high winds (the TSR is only 1.2 and you can build it very strong, so just let it spin and limit the output current so you don't fry the alternator), doesn't need to feed power through a brush or flexible wire from a generator that is always pivoting as the mill tracks the wind.  You WILL have a little more drag to guy against.  But it looks to me like an easier project - and one that could be made sturdy and long lived.

The main problems will be getting it up in the air, where the wind speed is higher, and doing generation from the low RPM of the shaft.  B-)

Even with a classic two-hemicylinder savonius, after you take into account the rectangle-versus-circle swept area conversion, you only have to make up a factor of about 1.5 to match a HAWT's power.  So make it the same diameter and about 1.55 times as high...


Adriaan Kragten

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Re: Prototype Oil Drum wind turbine
« Reply #22 on: December 11, 2016, 01:19:13 AM »
I don't believe in high Cp values for Savonius rotors whatever blade shape they may have. I have studied about ten reports with measurements of Savonius rotors available on the Internet. A summary of my findings about these measurements is given in my free report KD 599. If a high maximum Cp was measured, it always appears that the scale model was rather large with respect to the dimensions of the wind tunnel. This creates tunnel blockage and a Savonius rotor is very sensible to tunnel blockage because it has not only a large thrust but also a large force perpendicular to the wind direction. Tunnel blockage results in a non realistic increase of the Cp value. None of the measurements which I have found were performed in an open wind tunnel like it should be done for a Savanius rotor! In real wind the wake expands around the rotor and full expansion of the wake is only possible for an open wind tunnel.

But even if you find that for optimal conditions, a rather low maximum Cp of about 0.24 is acceptable, then a Savonius rotor has many other disadvantages like the large amount of material which is needed, the very strong fluctuation of the torque and the thrust for a Savonius rotor with two blades, the low rotational speed which requires an accelerating gearing to the generator and the fact that it is almost impossible to limit the rotational speed and thrust at very high wind speeds. These are the reasons that the use of Savonius rotors is limited to only very small sizes. A Savonius rotor with a diameter and height of 5 m would have a weight of several tons and the investement in material would be very much higher than for a wel designed horizontal axis wind turbine which generates the same power at the same wind speed.
« Last Edit: December 11, 2016, 01:25:39 AM by Adriaan Kragten »

electrondady1

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Re: Prototype Oil Drum wind turbine
« Reply #23 on: December 11, 2016, 05:37:23 AM »
there is a completely different set of design criteria with vertical axis machines that comes into play.
and that is "what does it look like"
propellers all look the same and so do hawts.
 vertical mills can look like anything you want .

 

gsw999

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Re: Prototype Oil Drum wind turbine
« Reply #24 on: December 13, 2016, 10:30:54 AM »
the drum shape captures the wind very well , I believe it is basically the perfect  shape for this kind of system , I am soldering the stator tonight , wish me luck.

gsw999

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Re: Prototype Oil Drum wind turbine
« Reply #25 on: December 14, 2016, 02:51:17 PM »
https://www.facebook.com/delaledge/posts/1344688945565022?pnref=story

Here are some pics of the stator and the rotor disks

Ungrounded Lightning Rod

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Re: Prototype Oil Drum wind turbine
« Reply #26 on: January 03, 2017, 03:20:38 PM »
... If a high maximum Cp was measured, it always appears that the scale model was rather large with respect to the dimensions of the wind tunnel. This creates tunnel blockage and a Savonius rotor is very sensible to tunnel blockage because it has not only a large thrust but also a large force perpendicular to the wind direction. Tunnel blockage results in a non realistic increase of the Cp value. ...

Thanks.  That's good to know - and to check out before committing on what (and how big) to build.

Quote
... a Savonius rotor has many other disadvantages like the large amount of material which is needed, the very strong fluctuation of the torque and the thrust for a Savonius rotor with two blades,...

Yes, weight is a big issue.  On the other hand, it serves as a flywheel, smoothing the torque variations with position, so it's not all bad.

Stacking three of them, offset by 60 degrees, is reasonably standard practice and should smooth out torque variations.  (All but the (3*N)th harmonics cancel.)

Quote
... the low rotational speed which requires an accelerating gearing to the generator and the fact that it is almost impossible to limit the rotational speed and thrust at very high wind speeds.

Why bother to limit the speed?  Let it spin.  Edge (tip) speed is only slightly higher than the wind, not near the speed of sound, so if it's built strongly (or lightly) enough it should be fine.

A well designed and balanced magnet rotor, with good bearings, in a permanent-magnet-alternator motor conversion should be able to handle the additional speed with no problem.  Shaft torque limit IS current limit and can be managed electronically.  For "gearing" at these low speeds (comparable to a building ventilator fan) I think a cluster of V-belts (with a giant pulley, again ala a building ventilator on the mill side) are entirely adequate.  They may be less efficient than a gearbox (90-98%, typically around 95%) but they're entirely adequte - and cheap.

Alternatively, we could go back to the early days of low-speed multi-pole, giant-rotor electrical machines.  An axial flux alternator the diameter of the rotor would have a pole-speed the same as, and get as much out of the magnets and copper as, one 1/6th or so the diameter (at the poles) of a horizontal-axis machine running at a TSR of 6.  (More, because the coils would have more surface area - crosswise to the wind - and get better cooling, so they could run a somewhat higher current with a given amount of copper.)  Fasten the magnets down solidly and you can let it spin to its heart's content.

As for wind loading, it can't be more than that of a wall of the same cross section, right?  A structure that would support the wall (or an elevated rotating advertising sign of the same swept area) would support the rotor.

Quote
.... A Savonius rotor with a diameter and height of 5 m would have a weight of several tons and the investement in material would be very much higher than for a well designed horizontal axis wind turbine which generates the same power at the same wind speed.

Five meters was a lot bigger than I was planning.

I was thinking of using 3/4" plywood as a starting point.  That's 2.13 ppsf.  Figure four 5-meter disks for a three-phase (ignoring a possible need for multiple layers for strength in a five meter mill...).   Treat the airfoils as two 5x6 meter areas of plywood (assuming PVC pipe for the turns and half-round dowels or airfoil-trailing-edge style wedges for the edges, as appropriate.

Airfoils:  60 square meters = 1376 lb.
Rotor disks:  27 square meters = 615 lb.

Yeah, that's 1991 lb, about a ton of wood, not including any thickening of the disks for such a large mill.

On the other hand, a ten-foot diameter rotor, 12 foot high (i.e. four-by-eight plywood sheets, without cutting, for the bulk of the airfoils / vertical strength members), designed the same way, would only be about 222 lb.  It also wouldn't need as much strength in the rotor disks, so a single layer of plywood might be sufficient.
« Last Edit: January 03, 2017, 03:30:44 PM by Ungrounded Lightning Rod »