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General Wind questions


By Derek, Section Wind
Posted on Wed May 03, 2006 at 08:38:06 PM MST
been reading a lot, still more questions

Alright, I've read quite a bit on wind turbines lately.  I'd like to build one here this summer.  Seems like it'd be fun!  But lots of questions still:

First, what sort of RPM's in 20 mph winds do you need for a wind generator to be worthwhile?  It seemed like most turbines were running 60-100 rpm's, but is this with our without a gearbox system to step up the rpms?

I'm a lot more interested in doing a vertical type turbine, just because they seem like they'd take up a lot less space and possibly be easier to build.  But I've read all the info I've seen about them (there's not much).

Also, how can I test the RPM's of a slapped together design that I built?  I've got something, although not sure how fast its going.  I'm guessing it was doing 100-200 rpm's based on a tab that I put on for it to click once ever rotation.  This thing is probably 3 cubic feet in size at the most and doing 100+ rpm's.  So what have I got here?

By the way, I have no magnets or anything on it at all.  Its just a bunch of scrap parts and a crazy idea!  haha
General Wind questions | 20 comments (20 topical)

Re: General Wind questions (3.00 / 0) (#1)
by force9BOAT on Wed May 03, 2006 at 05:39:47 PM MST

Can you post a photo of your machine?


Re: General Wind questions (3.00 / 0) (#2)
by vawtman on Wed May 03, 2006 at 07:04:41 PM MST

Derek
 Vawts are more complicated than hawts.Hawts are pretty much textbooked throughout the process.However they need clean wind to survive where vawts dont.
 Vawts need to take up alot more space maybe double the hawt and without proper design will not even start in low winds.
 Little vawts are easy but theres not much there.
    Just my opinion
 


Re: General Wind questions (3.00 / 0) (#3)
by Derek on Wed May 03, 2006 at 08:39:20 PM MST

I dont have an actual picture right now, but I did do a really quick sketch on MS paint.



Basically, what happened is I took the idea of a vertical turbine and then thought a way to eliminate the drag of the return blades against the wind.  This is done with an angled piece that goes in towards the center of the unit.  Basically, instead of "x" amount of air pushing past it and the blades fight against the wind to keep spinning, you get "2x" amount of air pushing against the blades and no fight against the wind.

Then I took the whole unit, and turned it horizontally, so that I could add a pivot point easily (a lazy susan thing for now)  And then the yaw to stabilize it into the wind.  It seemed to work quite well, hitting 100-200 rpm today in 20 mph winds.  The blades are just out of some thick aluminum flashing, which is mounted into round wood pieces on each side.

So what do you guys think?  What are the pros and cons of this?

[ Parent ]



Re: General Wind questions (3.00 / 0) (#4)
by wdyasq on Wed May 03, 2006 at 09:26:01 PM MST


Adventure is just bad planning." -- Roald Amundsen
[ Parent ]


Re: General Wind questions (3.00 / 0) (#5)
by dinges on Thu May 04, 2006 at 01:46:01 AM MST

Yes, that picture says it all...

Donkeys, desert and ancient technology. Ancient technology, that regularly gets reinvented :)

Peter.

[ Parent ]



Re: General Wind questions (3.00 / 0) (#6)
by dinges on Thu May 04, 2006 at 01:48:48 AM MST

Ehm, to clarify a bit more;

These are all drag-based systems. Nowadays, thanks to modern wing-profiles, we have lift-based machines. You get more energy per square meter out of them.

But your idea should work. And with the same effort and a better design (see this board) you could get much more energy.

You decide.

[ Parent ]



Re: General Wind questions (3.00 / 0) (#7)
by electrondady1 on Thu May 04, 2006 at 07:02:27 AM MST

congratulations derec.  a photo would be great.  if your machine can reach 200 rpm thats very good for a drag type devise. the air funnel must be working.

vawt builders are a bit of a sub spiecies around here but those that like them tend to support each other. if you include "vawt" in your post headings  you will get lots of hits.

i beleave the most advanced builder to be a man named windstuff ed . but there are lots trying to catch up.

when it comes time for you to harvest some power from your mill almost all the information here about generators can be useful . just remember your mill turns at about half the speed as a propeller so the geni's need to be about twice as big or geared up

[ Parent ]



Re: General Wind questions (3.00 / 0) (#8)
by Derek on Thu May 04, 2006 at 07:12:56 AM MST

I know that everyone will just recommend a HAWT, but I want to try something different.  :)

Now just some general wind turbine questions, I was wondering how many RPM's would I need to have an equal unit to some of the big wind turbines?

And what do you think the blades and end caps should be made of on mine?  I currently just used some .14" aluminum flashing, which I bent into curves pieces.  It actually works rather well, holds its shape just fine so far.  Thicker would be better I'm sure, but I definitely like the light weightness of the aluminum.  The round end caps I used wood.  I just used a jigsaw to cut this out, and also cut the curves slots in it for the aluminum.

The center rod, all I did was drill holes into the wood and slide it onto an electric metal fence post rod.  Then just lubed it up a bit, works rather well, but definitely nothing permanent.  So what would I want to use for the bearings on each end do you think?  I also sort of figure this would be easier than your average HAWT since it'll be attached at 2 points instead of just one.

The blade height, not sure if longer strips of aluminum would make it go faster or not, but surely wider ones would.  My thinking with this VAWT style wind turbine is this.  In order for a HAWT's center point to spin say 50 rpm, the outside of the blades might have to spin 100 rpm or something.  (dont know the math on this)  But on a VAWT, since the blades are shorter, they wouldn't have to actually spin as fast in order to achieve that center point spinning 50 rpm.  

Now I want to test my design at some high wind speeds, in which case I'd probably mount in on a small tower type of deal in the back of my truck or something.  Hopefully it doesnt self destruct and kill my truck.  :)  I have a 2005 Toyota Tundra.

But this will be my third free energy project.  The first was I made a really nice solar oven that could sell commercially for $99.  Gets 370-400 degrees here, no problem.  The second I made was a passive solar heater that would put out 110-160 degrees at 50 cfm.  Only 15" by 15" too!

But now wind power has caught my attention for those days that are windy but not sunny.  We have a commercial building downtown that is about 5,500 square feet.  Most of it is our martial arts school, but I have an 800 square foot room in the back that I'm using for these projects.  I want to put a wind generator on the roof of this building.  Now huge towers and noise wouldnt be good, so thats why I'm leaning toward a VAWT.

[ Parent ]



Re: General Wind questions (3.00 / 0) (#9)
by electrondady1 on Thu May 04, 2006 at 08:27:27 AM MST

what you must do first is make use of the google search engine to the right of the page.  i see it as the the door to a university on wind power . every question anser sesion for the last 3 years is there .read as much as you can. there are some brilliant people in this forum.

 lenghening the vanes will not make it go any faster , it will increase the torque, widening the mill will make it turn slower. but increase the torque.

 on a drag type wind mill the edge of the vane will travel basicly the same speed as the wind flow.

the center of any windmill has the same revolutions per minuet as the tip.but the linear velosity increases the wider you make it.

in order to produce the sort of power a big danb mill makes you will need to make a huge vawt mill.

 as far a a bearing goes , the choise is infinite . a trailer hub is the most common choise. thier strong and cheap, easy to find !

 hey, time to work on mine. good luck
shawn

[ Parent ]



Re: General Wind questions (3.00 / 0) (#10)
by vawtman on Thu May 04, 2006 at 03:59:20 PM MST

Derek I think I see a couple cons here.
  1. It would need line up with the wind(hawts would be better in that case)
  2. In the turbulant area you descibing it would really struggle I think.
  3. Lots of sheet metal to get reasonable power.
  4. You would still have drag on the return.
  My opinions and im trying to picture it has a larger unit.Vibration might be less.
 I wonder if the unit itself might try to spin in cicles.I guese we dont know till we try.Good Luck.

[ Parent ]


Re: General Wind questions - VAWT's (3.00 / 0) (#11)
by Derek on Thu May 04, 2006 at 07:11:22 PM MST

Vawtman, your name implies you might know what you are talking about!  )  It does in fact line up with the wind since it has a yaw on the back end.  The base of it is mounted on a lazy susan thing right now, which works quite well.

The aluminum that I have in it right now is probably about 50 cents worth honestly, so not much cost there at all.  Now you guys will laugh when you see the pics.  But I didnt spend anything but time on it, just to see if the concept actually works, which it seems to.  Its a cardboard box, with an electric fence post as the center rod, two wooden end caps, and aluminum fixed into it.  It has a tad bit of wobble on the center post, but thats because its just plain wood to metal, plus the fact I didnt have a bit handy that was big enough to actually allow the wood to spin freely around the metal rod.  So it was a custom crappy job....  But again, just a concept idea with scrap parts to see if works.

Obviously it will still have drag on the return, BUT, its drag is not against the oncoming wind though, which is my claim to fame on this project I think.  And if I sound dumb, thats because I know squat about wind power, only starting out!

In the background, you can see some of my solar ovens that I've constructed too, which hit 370-400 degrees no problem.  But the wind thing has caught my attention for those cloudy days to give me something to do!

But basically, the idea is that wind from the bottom intake will push one blade back, and as it passes the area that the wind reaches it, the next one comes into play then.  Here are the pics:


"80%" src="http://www.otherpower.com/images/scimages/4891/wind_angle.JPG">





And by the way, this site it awesome!  And everyone is extremely helpful and polite, thanks guys!  I've been on some sites with nobody but rude people.

[ Parent ]



Re: General Wind questions - VAWT's (3.00 / 0) (#12)
by Derek on Thu May 04, 2006 at 07:12:34 PM MST

Wow, I messed something up there, try again:

Vawtman, your name implies you might know what you are talking about!  )  It does in fact line up with the wind since it has a yaw on the back end.  The base of it is mounted on a lazy susan thing right now, which works quite well.
The aluminum that I have in it right now is probably about 50 cents worth honestly, so not much cost there at all.  Now you guys will laugh when you see the pics.  But I didnt spend anything but time on it, just to see if the concept actually works, which it seems to.  Its a cardboard box, with an electric fence post as the center rod, two wooden end caps, and aluminum fixed into it.  It has a tad bit of wobble on the center post, but thats because its just plain wood to metal, plus the fact I didnt have a bit handy that was big enough to actually allow the wood to spin freely around the metal rod.  So it was a custom crappy job....  But again, just a concept idea with scrap parts to see if works.

Obviously it will still have drag on the return, BUT, its drag is not against the oncoming wind though, which is my claim to fame on this project I think.  And if I sound dumb, thats because I know squat about wind power, only starting out!

In the background, you can see some of my solar ovens that I've constructed too, which hit 370-400 degrees no problem.  But the wind thing has caught my attention for those cloudy days to give me something to do!

But basically, the idea is that wind from the bottom intake will push one blade back, and as it passes the area that the wind reaches it, the next one comes into play then.

And here is the pic that didnt load:





[ Parent ]



Re: General Wind questions - VAWT's (3.00 / 0) (#17)
by vawtman on Fri May 05, 2006 at 04:43:42 PM MST

Derek im sorry if my handle comes across has me being a knowitall.It was my daughters idea when I was setting up.Ive flown alot of contraptions and settled on a lift based multibladed turbine.
 Take it out and fly it.I can tell you I never flew your concept.Give her a whirl and

 you will learn from it.
 Isnt that old turbine that Ron posted earlier cool.I saw that before cant remember the sight though.
 

[ Parent ]



Re: General Wind questions (3.00 / 0) (#15)
by finnsawyer on Fri May 05, 2006 at 10:00:32 AM MST

The blades moving along the bottom half will still have to push dead air, meaning they will waste power.  If you turn the unit upside down, you can then place holes along the top frame just back of the sharp angle.  This will cause a difference of air pressure between the still high pressure air inside and the moving low pressure air outside causing air to flow out and reducing the pressure the vanes have to work against.  If instead of the sharp angle at the top you put in a nice circular shape you can speed up the air just back of it more and hence lower the pressure there even more.  Or you could also keep the sharp point and instead put something like a tear drop shape some distance above the sharp point.  I'd try a radius two to four times the gap.  This will also speed up the air and lower the pressure over the holes.  Basically it would put more area of the air stream to work for you.
GeoM
[ Parent ]


Re: General Wind questions (3.00 / 0) (#13)
by jaysicle on Thu May 04, 2006 at 08:33:04 PM MST

Derek,

I am building a Savonius, and you probably know this, but usual Savonius is 360° wind direction. This is cut in your design, but maybe reduced drag will offset.

Toilets and wheels are also ancient technologies, but we don't laugh at them.

Free is Free.
Carry on!  

-J-



Re: General Wind questions (3.00 / 0) (#14)
by electrondady1 on Fri May 05, 2006 at 05:44:46 AM MST

we all have to start some were. i think it's a clever use of materials. as an experiment it's a sucess. if you can get the next one to live outside your on your way!

[ Parent ]


Re: General Wind questions (3.00 / 0) (#16)
by Derek on Fri May 05, 2006 at 12:13:10 PM MST

finsawyer, I love the idea about the holes cut for reducing air pressure!  I never thought about that actually, but yes, that would probably help a bit too.

The actual turbine itself doesnt catch wind at 360 degrees, but it pivots just like a windmill anyways, so its always pointed into the wind.  So I think it will still have that advantage.  Plus, do you think if you have say 4 square feet of area of wind being forced through a 2 square foot area via a funnel type system like this that it will increase the actual pressure and speed of the turbine?

I also want to find an anometer (how do you spell that?) to measure wind speeds then too.  And then also, I'd like to have something to accurately measure RPM's then too.  That way I can tell what sort of wind speeds generate various RPM's with some slightly modifed designs.

The point about the overall length of the blades adding more rpm's and then width adding torque really caught my attention too.  By adding more width to a blade, it will add torque, but it will probably slow down the RPM's too wont it?  I guess you have to find a happy medium of the two probably.  But how much torque does it require for turning a generator?

[ Parent ]



Re: General Wind questions (3.00 / 0) (#18)
by commanda on Fri May 05, 2006 at 06:07:18 PM MST

I love the idea about the holes cut for reducing air pressure!

What if you had another box which collected air & fed it past these holes; thinking venturi effect here. Create a semi-vacuum to suck the returning blades.

Hope that makes sense.

Amanda

[ Parent ]



Re: General Wind questions (3.00 / 0) (#19)
by Derek on Sun May 07, 2006 at 12:53:50 PM MST

I was also thinking that really you could eliminate the slip ring obstacle too.  I could still make it all vertical with the yaw on the back of a taller, rather than wider, unit.  It would be shaped sort of like those new tall skinny ion air purifier deals.

And how can I measure the RPM's and torque of this thing as I'm changing variables in trying to perfect it?

[ Parent ]



Re: General Wind questions (3.00 / 0) (#20)
by commanda on Sun May 07, 2006 at 03:20:03 PM MST

And how can I measure the RPM's and torque of this thing as I'm changing variables in trying to perfect it?

Search the board for tacho & prony brake.

Amanda


[ Parent ]



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