Author Topic: VAWT land (Read 16312 times)

GeeMac · « **on:** August 30, 2008, 07:38:08 PM »

I've been thinking about making a VAWT and it occurred to me that if a fella bought a couple of six or eight inch sheet metal furnace pipes he could easily fabricate the blades. Has anyone done this? Is there a reason I shouldn't use a pipe to make the blades?

spinningmagnets · « **Reply #1 on:** August 30, 2008, 01:58:30 PM »

It sounds like you want a "Savonius" VAWT? If yes, no reason the sheet-metal tubes wouldn't work as well as anything else thats been tried.

Before you spend money or time building one, I urge you to research "Benesh profile" and "Lenz 2".

Each has its own peculiarities, and all can be cheap and fun to make. Though they all seem to make very few Watts inspite of extensive experimentation.

"Exaggeration is a million times worse than understatement" -Steven Wright

TheCasualTraveler · « **Reply #2 on:** August 30, 2008, 03:08:16 PM »

GeeMac,

I did a Vawt for my first project and used the metal duct like you mention. Here's a link to a short video.

http://s241.photobucket.com/albums/ff74/compoast/?action=view&current=savonius4.flv

I never completed it with alternator because my design lacked integrity. It was basically two half rounds made from duct pipe and capped at each end by plywood rounds. Overall 60" tall by 24" wide. It spun real nice in very light wind but in higher winds it vibrated badly.

I may try a VAWT again one day and if I do I will forgo the more efficient designs like Ed's Lenz II because I'm just not that good at building. Instead I will go with a basic Savonius design (two half rounds) and what it lacks in technology I will make up for in simple, light weight, sturdy construction and with emphasis on balance and bearings. Instead of metal half rounds I may try those cardboard tubes used as forms for pouring concrete as a mold to form fiberglass half rounds. Probably go with 60 or 72 inches tall by 30 inches wide. Just an idea I may never get to and if I do it wont be much power anyway. I did this because I live in town and thought I couldn't get away with a HAWT. But my HAWT has been flying for almost a year now with up to 6 foot blades and no one has complained. In fact, people love it.

tecker · « **Reply #3 on:** August 30, 2008, 05:02:39 PM »

You can't beat Barrels IMHO I 've spent the better part of the day tacking this one to gether Got a 15 gal I like it's on top of the shop and doubles as a power vent . This one is going on the well house .55 gal 120degree 11 inch expansion. No center shaft 5/16 rod to true the center.I'll add another tier as soon as I get the genset working on this tier.

wooferhound · « **Reply #4 on:** August 30, 2008, 05:27:47 PM »

I never saw a savinous with 3 blades like that

makes me wonder . . .

tecker · « **Reply #5 on:** August 30, 2008, 05:44:24 PM »

I worked this out on a small scale and with two tiers it starts well and gyros about 110rpm The 15 has motor coils in the genset this one will also .

Todd a · « **Reply #6 on:** August 30, 2008, 08:59:01 PM »

I like this one...

http://www.youtube.com/watch?v=cSlXF4Dbs5A&feature=related

Made from 16 half pipes.

I am planning on a lift type VAWT, but there are some main issues with this style... They require a lot of wind to start up on their own. Most large ones actually have a start-up motor to get it spinning. This is kind of like what I am looking for...

http://www.youtube.com/watch?v=gipF0J9oyNk&feature=related

Others add drag style blades to make a hybrid VAWT, like this...

http://www.youtube.com/watch?v=9PNngA4wP9o&feature=related

Picture the style of the middle video with a half pipe installed on the truss about mid way between the blades and the hub. That is what I likely am going to have. The halfpipes will help the start-up speeds, but when the wind picks up the other blades will take over and speed up. Yes the half-pipes will slow down a tiny bit, but the start-up speeds and low wind characteristics will pay off in the long run.

There other than the start-up speeds the other big issue is the pulsing from the blades. Adding more blades will help, but the best way to fix this is by slanting the blades...

http://www.youtube.com/watch?v=6SyW0eBDVnA&feature=related

There are versions that rotate the blades, but these require a tail fin. They are slower, but with very high torque...

http://www.youtube.com/watch?v=uoPXennEnz4

luckeydog · « **Reply #7 on:** August 30, 2008, 11:52:56 PM »

you can use 55 gal. barrels like this monster 50 ft. tall and 6ft wide

tecker · « **Reply #8 on:** August 31, 2008, 06:11:56 AM »

The 55 gal barrel is heavy enough to weld together and hold together . I can move these around and not loose the balamce and when up to 150 rpm they have torque that loads up nicely .

tecker · « **Reply #9 on:** August 31, 2008, 06:15:18 AM »

The only part of a Vawt that needs to set up is the max torque small or large get the voltage up to charge and hold the current down with a pwm.

Norm · « **Reply #10 on:** August 31, 2008, 07:43:58 AM »

I've tried 3 blades on a small scale (plastic

cups) 2 tiered, 2 blades per tier, offset 90

degrees from the other tier seems to work better

for me.

tecker · « **Reply #11 on:** August 31, 2008, 08:48:49 AM »

The jurys's still out on 90 second tier offset it depends on how the air enters the inner vortex if the second tier is blocked say with a plate between its effective but if the air goes from one tier to the other then the pressure exchange between the two interfears .

vawtman · « **Reply #12 on:** August 31, 2008, 10:48:17 AM »

The one your planning on will not need high winds for startup.The skinny bladed eggbeaters do though.

Mine starts at the same windspeed has a hawt would.It's sorta like the one pictured.Second video down.

Mark

windstuffnow · « **Reply #13 on:** August 31, 2008, 11:19:52 AM »

The ones I've tested I found the torque is that of 1 tier for the entire machine. What it does is offset the torque pulse from 180 degrees to 90 degrees. You have lower torque but a more continuous torque.

I built a 4 tier unit with the blades offset by only 22.5 degrees, very similar to the "twisted" or "helix" savonius. This actually seemed to remove the torque pulse but still only carried the torque of one tier or slightly above.

Overall I never achieved much more than 20% efficiency with any of the units I built. They provide a very good torque at low rpm and would be well suited for pumping water, running an air compressor and such but for electric they present a number of challenges. It can be done...

.

tecker · « **Reply #14 on:** August 31, 2008, 01:38:35 PM »

The problem i've seen is that the air swirls inside and doesn't exit as the rpm increases Low rpm the air passes thru .

windstuffnow · « **Reply #15 on:** August 31, 2008, 04:42:05 PM »

For maximum extraction, on a drag machine, the turbine needs to be loaded to a TSR of 0.33 or 1/3 of the wind speed. The closer it gets to a TSR of 1 the less power it can extract.

For instance, if the blade, or drum, is moving away from the wind as fast as the wind is commng in then there can't be any power extraction.

On another note, the efficiency of the savonius type blade is very close to the Betz limit when loaded if you consider the actual wind it's extracting from. As an example, the wind is moving at 10mph the turbine is loaded to a TSR of .33 or moving away from the wind at 3.3 mph your actually extracting energy from a 6.7 mph wind. Unfortunately, after you subtract the up wind blade drag and other machine inefficiencies the power is considerably lower. Since your only extracting energy from one side of the turbine it makes it look like it's not very efficient overall when in reality the blade or drum is actually extracting energy more efficiently than alot of "good" turbines that are out there.

Put that 1/2 drum on a linear alternator and run it in a straight line for a mile or two it would have better efficiencies than almost all the turbines being built. You may need to run the return drums in a tunnel below the main run to reduce the losses.

Unfortunately they just don't do so well in a circle...

;O)

.

tecker · « **Reply #16 on:** August 31, 2008, 05:26:11 PM »

Yep the half drum will start backward untill it hits the entry point the drag there has very little lift to reguage .

tecker · « **Reply #17 on:** August 31, 2008, 06:19:10 PM »

I 've watched the air on the upwind side of the two halves the air gets split as the work cycle starts . In misty weather you see the air gush to the outside and there's not as much air that goes through the turbine as the model shows . I've seen some videos of darius Halve drum combos that look powerful

vawtman · « **Reply #18 on:** August 31, 2008, 06:45:38 PM »

Darrius half drum combo's ?

tecker · « **Reply #19 on:** August 31, 2008, 10:48:10 PM »

This one

http://www.youtube.com/watch?v=Lbiqrpjy-f4

GeeMac · « **Reply #20 on:** September 01, 2008, 07:26:55 AM »

I like that idea because the barrel ends lend support to the blades. It should last a long time. I am thinking about a vawt because I am in an urban area and the city council, the evil bstrds, will look upon a large mill with an eye to taxing or licensing its use for their gain. Anyway, I have an entire Canadian northern winter to tinker with the idea. Did I say winter? I did! I'm going to wash my mouth out with soap. By the way, does anyone know how a taser takes a nine volt battery and turns it into fifty thousand volts? We might be able to use that method to charge a battery bank.

tecker · « **Reply #21 on:** September 01, 2008, 10:13:44 AM »

I think your idea of using Stove pipe over a frame is a good one 8 inch stove pipe is about 25 inches so you could make a frame for 16 inch and with the overlap not cut out . Three of those and some5/16 rod per tier and your up and runnin in 4 to 5 hours . I don't use a center shaft . It's hard to true up couple of 1/2 bolts and these work well

http://www.vxb.com/page/bearings/PROD/Mounted-Bearings/Kit7494

colej · « **Reply #22 on:** September 02, 2008, 09:03:04 PM »

Could you block the wind from acting against the back barrel and somewhat direct it into the scoop with a vain driven cowling type rig?

the Vain would keep the cowling in front of the oncoming half reducing the backforce

Whats the drawbacks to this?

In theory it sounds like it would work.

tecker · « **Reply #23 on:** September 03, 2008, 07:09:45 AM »

Rediirecting the around the upwind is a good idea . I've been trying to do this with the rotor but still have a bit going around the other direction but there is lift there now starting at 40 rpm .

colej · « **Reply #24 on:** September 03, 2008, 05:04:29 PM »

here is an idea I had last night after reading your post. My theory is that the "cowling" would not only block the wind from the Leeward edge, but also focus some wind into the Windward edge boosting the efficiency (at least in theory). As wind direction changes so would the cowling to always block the leeward edge from oncoming force.

I'm sure there will be some turbulance within (design idea for another day) but just maybe the benefit of blocking the drag side would still be beneficial.

Comments please.

<img

windygen · « **Reply #25 on:** September 09, 2008, 11:47:43 AM »

Some info that may or may not be interesting to the VAWT folks:

News:

Author Topic: VAWT land (Read 16312 times)