My First Vawt Project

[SparWeb]

Stuff accumulated on my hard drive over the years...

 SAND-78-1737_Perf_17m_Darrieus.pdf (2615.08 kB - downloaded 256 times.)

 SAND-79-1068_Future_Dar_Turbines.pdf (764.76 kB - downloaded 231 times.)

 SAND-76-0131_Savonius_Rotors.pdf (2840.8 kB - downloaded 215 times.)

[tjm2000]

Thank you Sparweb, that is very helpful.
Interesting that Sandias research/designs are nearing 40 years old but still achieved a cp of more than 0.4. That is up there with modern 3 blade Hawts.
Although darrieus turbines are few and far between nowadays, almost all of them are H rotor designs, not the troposkein design.
From what I have read, most of the issues for these turbines was fatigue and failure of the blades. Surely with modern composite technology one could build a reliable, large scale darrieus turbine?

I am going to build a troposkein shaped vawt, probably along the lines of Sandias 5m prototype.
4M diam, 4M tall, 2 blades with a 0.015M chord and a NACA 0015 profile. Estimated power will be 2kw

[topspeed]

Thank you Sparweb, that is very helpful.
Interesting that Sandias research/designs are nearing 40 years old but still achieved a cp of more than 0.4. That is up there with modern 3 blade Hawts.
Although darrieus turbines are few and far between nowadays, almost all of them are H rotor designs, not the troposkein design.
From what I have read, most of the issues for these turbines was fatigue and failure of the blades. Surely with modern composite technology one could build a reliable, large scale darrieus turbine?

I am going to build a troposkein shaped vawt, probably along the lines of Sandias 5m prototype.
4M diam, 4M tall, 2 blades with a 0.015M chord and a NACA 0015 profile. Estimated power will be 2kw

Yes and very unfortunate is that when you apply for funding several "old farts" say this has all been tested in the 70ies.

[tjm2000]

Thank you Sparweb, that is very helpful.
Interesting that Sandias research/designs are nearing 40 years old but still achieved a cp of more than 0.4. That is up there with modern 3 blade Hawts.
Although darrieus turbines are few and far between nowadays, almost all of them are H rotor designs, not the troposkein design.
From what I have read, most of the issues for these turbines was fatigue and failure of the blades. Surely with modern composite technology one could build a reliable, large scale darrieus turbine?

I am going to build a troposkein shaped vawt, probably along the lines of Sandias 5m prototype.
4M diam, 4M tall, 2 blades with a 0.015M chord and a NACA 0015 profile. Estimated power will be 2kw

Yes and very unfortunate is that when you apply for funding several "old farts" say this has all been tested in the 70ies.

They are definitely worth exploring further in my opinion. Mine has been producing some pretty impressive results, The best so far was 13.1 KWH for a 24 hr period. Not bad at all for a small homebuilt machine.

[bigrockcandymountain]

That is awesome tjm2000.  I'm not usually impressed with vawts.  This one is the exception.  13 kwh in 24 hrs is also very good.  For comparison, my horizontal with over twice the swept area rarely does that. 

Now you have set the bar higher so i might have to do some tweaking on mine over the winter.

Where are you at? That looks like a great site for wind.  Beautiful, rugged country too. 

[tjm2000]

That is awesome tjm2000.  I'm not usually impressed with vawts.  This one is the exception.  13 kwh in 24 hrs is also very good.  For comparison, my horizontal with over twice the swept area rarely does that. 

Now you have set the bar higher so i might have to do some tweaking on mine over the winter.

Where are you at? That looks like a great site for wind.  Beautiful, rugged country too.

I live in Central Otago, New Zealand. This location has a great wind resource, often 10-15 ms during the day and 5-10 during the night.
There was plans for a 630 MW wind farm on my doorstep, It got consent, but that was overthrown in the environmental court after many complaints from residents. This is disappointing but I can understand why people don’t want turbines here, as it is a pretty unique landscape.

[SparWeb]

Surely with modern composite technology one could build a reliable, large scale darrieus turbine?

Absolutely.  But design with composites is more demanding than metals - not to lecture about it since you seem to have some experience with that.  The details.  How do you build in that curved shape that meets at top and bottom, without applying too much permanent stress?

The "troposkein" was developed as a simplified shape, which was intended to remove most of the bending moments in the blades.  Basically, the shape of a skipping rope as it is swung around.  Same thing but the rope is swung vertically.  The true shape is called a "catenary" and I have never figured out why that shape wasn't used by the tests in the '70's.  I believe the NRC in Canada studied one of these in New Brunswick around the same time, and they chose to use a 3-segment blade where the upper and lower segments were straight and the middle segment was a circular curve...  adding up to almost close to the ideal catenary shape.  There were some long-term reports of fatigue cracking and that seems to have been the end of it, for the "big science" team.

I knew nothing about this until about 2004 when I was driving from Fort Macleod to Calgary and saw a commercial prototype that looked just like this.  The prototype didn't thrive as a business, but I couldn't shake the idea from my mind.  I started reading and... well you know the rest...  here I am...

[tjm2000]

Just thought I would give a quick update. No major issues yet, although there is a couple of minor ones.
The charge controller is not very efficient and not very reliable. This will be replaced with a homemade Arduino powered charge controller when I get the time.
Vibration, noise and safety are big concerns. This turbine was originally intended to be located in a remote location, however due to various reasons, it will stay in its current location next to my house for the time being. It gets quite noisy anywhere over 120 rpms. Most of this is likely due to the struts, which is just rectangle aluminium bar. It is also pretty dangerous to be around when it is windy. The blades are barely out of arms reach and if one detached at high speed with somebody nearby the outcome could be very bad. I should have made the tower much taller.
The paint on the blades has taken a beating. It is stripped back to primer on the leading edge.

In terms of electricity production, I am reasonably happy, 695 kwh in 6 months or 3.8kwh per day. I think my charge controller is a bit ambitious with that number, as I am not getting that much out from the batteries.

[SparWeb]

Thank you - these updates are very welcome - especially when the machine is still going!
That's an excellent result, especially for a first-timer. 

Paint - there are several types of clear self-adhesive tape you can put over the paint to protect the leading edges from erosion.

CC - do you mind sharing more details?  How are your batteries holding up?

Noise - are you interested in trying the aluminum extrusions with an oval or teardrop shape?

Tower- everyone makes that mistake.  I had to make my tower taller too (in my case, an arms-race with the trees).

[topspeed]

Just thought I would give a quick update. No major issues yet, although there is a couple of minor ones.
The charge controller is not very efficient and not very reliable. This will be replaced with a homemade Arduino powered charge controller when I get the time.
Vibration, noise and safety are big concerns. This turbine was originally intended to be located in a remote location, however due to various reasons, it will stay in its current location next to my house for the time being. It gets quite noisy anywhere over 120 rpms. Most of this is likely due to the struts, which is just rectangle aluminium bar. It is also pretty dangerous to be around when it is windy. The blades are barely out of arms reach and if one detached at high speed with somebody nearby the outcome could be very bad. I should have made the tower much taller.
The paint on the blades has taken a beating. It is stripped back to primer on the leading edge.

In terms of electricity production, I am reasonably happy, 695 kwh in 6 months or 3.8kwh per day. I think my charge controller is a bit ambitious with that number, as I am not getting that much out from the batteries.

Is it still running ?

[tjm2000]

It is still running! I took it down for a few weeks over winter as 2 blades had developed cracks (and filled with water?) I just added some fiberglass tape over top and its been fine since. I also replaced the bearings as the were getting noisy. The bearings I pulled out were junk, minimal lubrication and made of cheese. I'm impressed they lasted this long. Replaced with some skf bearings and all is well!
I also replaced the charge controller with a simply raspberry pi setup.
It has been powering a crypto mining server for the past 6 months, which has been quite profitable.
Overall I'm still very impressed by it. I'd love to build another but other projects are taking up my time and money these days.

[SparWeb]

I'd love to build another but other projects are taking up my time and money these days.

Ain't that the truth.  Thank you for dropping in with an update - don't be a stranger 

[Crockel]

It has been powering a crypto mining server for the past 6 months, which has been quite profitable.

That sounds interesting. I'd been thinking of going with a crypto mine set up for a windy location that's too far from any grid locations.

[Astro]

I'd love to build another but other projects are taking up my time and money these days.

Ain't that the truth.  Thank you for dropping in with an update - don't be a stranger 

 I have the exact opposite problem. This wind project is eating up the money for other projects. LOL. I am hoping to have it done and the whole system done by fall, that way next winter I can start collecting parts for other projects.

[Astro]

So i just took the time a read through this thread. Much of what was built is pretty much how I had mine planned out, except I am building my own dual axial pma.  So for me it is great news that this project worked out pretty good. It also gives me something to go off of when shooting for numbers. Thanks guys for bringing this thread back up as I had not seen it in my digging and reading.

[JW]

https://www.fieldlines.com/index.php/topic,146204.msg999075.html#msg999075

[JW]

https://www.fieldlines.com/index.php?topic=143565.0

[Astro]

 Some questions. I read where the diameter of the whole thing is what is what it is, because the thought is while a reduced diameter will spin faster, it will have less torque. Can someone explain that to me in laymans terms? Isn't the wing only going to catch x amount of wind due to it;s size and not the diameter or spacing of them?
 Also this thread brings up something else. While it produces nicely in higher winds, he said it does not like to start up under 6 m/s, which is a little over 13 mph. How would one go about lowering that number a little? Different air foil? Because that was the exact reason I wanted to try a modified Lenz 2 design. To have something that caught a little more air then a symmetrical air foil. I could see the start up becoming a problem with even a slightest variation between building materials and design and to be honest, I am not going to do the math and do not have a wind tunnel to play with to find the exact blade profile to lower the start up wind speed.

[MattM]

Skinny diameter may be higher RPM but you lose leverage and therefore RPMs are relatively higher.  Too much of anything can be a bad thing, so need arises for braking.  Wider diameter lowers RPM but increases material costs while increasing weight and leverage.  Weight increases resistance from friction.  PMGs do like high RPMs, so whan you get to work is probably a function of location and needs.  If you gear up to increase RPMs then it is more resistance, but more likely to be functional across more wind velocities.  Everything comes down to a compromise.

[Astro]

Skinny diameter may be higher RPM but you lose leverage and therefore RPMs are relatively higher.  Too much of anything can be a bad thing, so need arises for braking.  Wider diameter lowers RPM but increases material costs while increasing weight and leverage.  Weight increases resistance from friction.  PMGs do like high RPMs, so whan you get to work is probably a function of location and needs.  If you gear up to increase RPMs then it is more resistance, but more likely to be functional across more wind velocities.  Everything comes down to a compromise.

 Ah yes leverage. I did not even think of that earlier when I asked that question. Which that would play into stall numbers as well and he said he was kicking out about 1,000 watts so it is going to have some drag on it when pushing 1kw. Well that was a simple answer. Thanks.

[SparWeb]

Another way to look at it:
For any tip speed ratio, the blade is traveling through the air at some velocity.  If the TSR is 1, then the velocity of the blade is equal to the wind speed, whatever the wind speed.
For a wind speed of, say 20 mph, then the blade is traveling around the center at 20 mph. 
If the radius of the VAWT is 3 feet, then it goes around once in 3 seconds.  20 RPM.
If the radius is 6 feet, then it takes 6 seconds to go around.  10 RPM.

The bigger VAWT has a bigger swept area, collects 2x more power.  So even going slower, it can develop more torque.

[Astro]

Another way to look at it:
For any tip speed ratio, the blade is traveling through the air at some velocity.  If the TSR is 1, then the velocity of the blade is equal to the wind speed, whatever the wind speed.
For a wind speed of, say 20 mph, then the blade is traveling around the center at 20 mph. 
If the radius of the VAWT is 3 feet, then it goes around once in 3 seconds.  20 RPM.
If the radius is 6 feet, then it takes 6 seconds to go around.  10 RPM.

The bigger VAWT has a bigger swept area, collects 2x more power.  So even going slower, it can develop more torque.

 That is also a simple way to put it and expands on the subject a bit. O mean I kind of feel dumb after just reading the word torque, because I was like duh, that makes sense. But as to how it plays out in tsr, you explained that very well also. Thanks.

[topspeed]

Thank you Sparweb, that is very helpful.
Interesting that Sandias research/designs are nearing 40 years old but still achieved a cp of more than 0.4. That is up there with modern 3 blade Hawts.
Although darrieus turbines are few and far between nowadays, almost all of them are H rotor designs, not the troposkein design.
From what I have read, most of the issues for these turbines was fatigue and failure of the blades. Surely with modern composite technology one could build a reliable, large scale darrieus turbine?

I am going to build a troposkein shaped vawt, probably along the lines of Sandias 5m prototype.
4M diam, 4M tall, 2 blades with a 0.015M chord and a NACA 0015 profile. Estimated power will be 2kw

Yes and very unfortunate is that when you apply for funding several "old farts" say this has all been tested in the 70ies.

They are definitely worth exploring further in my opinion. Mine has been producing some pretty impressive results, The best so far was 13.1 KWH for a 24 hr period. Not bad at all for a small homebuilt machine.

Not bad at all..is it still running ?

What is your opinion of  a 1 blade VAWT ?

[tjm2000]

It is still running!
I dont live on site anymore (its at my parents house) but I give it a good going over every 3 months or so.
I take the blades off for a few weeks every winter to do repairs. They still get water inside and then I think that water freezes and cracks the blade. All blades have numerous repaired cracks on them now. I replaced the L brackets that hold the blades on as some of them were turning white at the angle, likely the aluminum fatiguing.
Its on its 3rd set of bearings and its 6th coat of paint.
Otherwise no other issues. Output still seems to be the same and it easily powers an office containing 2x lights, a computer and a mini split for heating/cooling.
I still dream about building another but I dont have a suitable location or a need for it right now, and its tough to go past solar considering how cheap it is getting.

[SparWeb]

Thanks for the update!
It's rewarding to know that it will last, after all that work.

Have you put drains into the blades to let the water out?

[topspeed]

It is still running!
I dont live on site anymore (its at my parents house) but I give it a good going over every 3 months or so.
I take the blades off for a few weeks every winter to do repairs. They still get water inside and then I think that water freezes and cracks the blade. All blades have numerous repaired cracks on them now. I replaced the L brackets that hold the blades on as some of them were turning white at the angle, likely the aluminum fatiguing.
Its on its 3rd set of bearings and its 6th coat of paint.
Otherwise no other issues. Output still seems to be the same and it easily powers an office containing 2x lights, a computer and a mini split for heating/cooling.
I still dream about building another but I dont have a suitable location or a need for it right now, and its tough to go past solar considering how cheap it is getting.

Outstanding achievement. I also got my wings flooded when I forgot to duct tape the seems. I dried it up and did more testing.

All other wood parts also got swollen....and after drying out all bolts were loose. I had to retighten them.

[JW]

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4/26/2024

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