Author Topic: Wind generator design options? (Read 11297 times)

KilroyOdin · « **Reply #33 on:** January 15, 2010, 12:40:01 AM »

Greetings, check out the German design at the link below, it has some good ideas.

http://www.vawts.net/forum.spark?aBID=125317&p=1

If you use multiple strands of wire when you make your coils it will help increase your output at low RPMs. Best of luck with your project and hope to see some pics.

If you check my images you get some other ideas. Have a good one and best regards.

Perry1 · « **Reply #34 on:** January 15, 2010, 02:47:54 AM »

The amount of power you are talking about making over time will be equal to unplugging your cell phone charger when not in use. I guess that's why people are trying to help by sharing their deep experience in this field.

You haven't mentioned any numbers, how much power are you thinking you will be able to make with this?

Perry

Kwazai · « **Reply #35 on:** January 15, 2010, 05:09:00 AM »

There are several reasonably good VAWT designs, besides a barrel type savonius. You have Lenz, darrieus, and a few special ones that look like a ying/yang type design.

At 10' you'll probably be building out of plastic( buckets/wings?) with a car hub/axle.

The efficiency nubers are lower for VAWT than for HAWT, usually and a lot of the 'hype' on the net about ducted types is because they violate betz assumption in calculating the efficiency (swept area of duct versus swept area of mill...). savonius seems to be about 17% efficiency (best), with the HAWT types getting into the 20-30% range (these are rough numbers...).There is a little .gif that has been posted that shows them along with the power calcs.

you might want to read this-

http://www.greenenergywindturbine.com/download/vawt/760131.pdf

VAWT are typically drag type turbines (typically).

What were you thinking for materials to build it from. (My preference has always been the crippling assumption--"it must be built from crap"...)

The black one I built is an old bicycle wheel, bamboo and trash bags held together with bailing wire and ducttape- usually lasts 6-7 months before rebuilding-next one is going to be bigger...hadn't tried anything other than a bicycle genny on it. Winds around my yard are seldom above 1.5m/s. Once in a blue moon I'll get 18mph winds(weatherman).

My brother has a 5ft pinwheel type hawt built from corrugated plastic board.

I can send you a pdf on them also. (mswayze at truswood dot com).I filter my spam- so use a "pinwheel" subject line.

L8r

Mike

electrondady1 · « **Reply #36 on:** January 15, 2010, 08:05:56 AM »

fluxable ,

stay flexable!

my first generator was much as you describe.

if you want to understand how a permanent magnet generator works this is the place.

you have even been given advise by hugh piggot who for the most part invented this activety in the '70s

all the negative things that have been said about verticals are true.

but,

they ARE beautiful, and that makes up for it.

i invite you to join the site oden has linked to.

electrondady1 · « **Reply #37 on:** January 15, 2010, 08:09:10 AM »

fluxable ,

stay flexable!

my first generator was much as you describe.

if you want to understand how a permanent magnet generator works this is the place.

you have even been given advise by hugh piggot who for the most part invented this activety in the '70s

all the negative things that have been said about verticals are true.

but,

they ARE beautiful, and that makes up for it.

i invite you to join the site oden has linked to.

i am a member there as well .

ChrisOlson · « **Reply #38 on:** January 15, 2010, 08:57:01 AM »

If you use a lighter gauge of wire, you will be able to put in place much more than 60 turns.

I quoted this because this is where your idea falls apart. I do not want to sound negative but you must understand that using more turns of smaller wire increases the resistance of the generator and DECREASES its efficiency - the exact opposite of what you're looking to do.

The most efficient alternator will use the fewest turns possible of the largest wire possible. You only add turns to create the proper voltage at the desired speed it runs at. So, in other words, if you wind one stator with many turns of small wire it won't work as well as the big stator because its resistance will be too high. You need to figure the resistance in your generator windings and this will become clear.

I will give an example here of a 12 pole with 9 coils and a desired cut-in of 35 rpm, an open voltage of 15, and a coil turn length of 9:

Using AWG 14 wire your resistance will be .77 ohm per phase wired star

Using AWG 18 wire your resistance will be 1.95 ohm per phase wired star - over DOUBLE what it is using the larger wire.

You're not apparently understanding that you still need the same number of turns of wire no matter what the wire size is. You do realize that you can wind more turns of smaller wire to get higher voltage at lower rpm, but you're not figuring the decrease in efficiency from doing this - it ends up being fruitless because the resistance of the windings gets so high you get no watts out of it anyway.

If you're looking to get much lower cut-in than even a three-phase star generator will give you, you'd be much better off to use a cap multiplier on the low end.

--

Chris

fluxable · « **Reply #39 on:** January 15, 2010, 10:28:03 AM »

Thanks for the replies everyone and for the invite to the other site! I'm getting plenty of good feedback, thank you!

VWAT's are not the most efficient generators, I know, but because they run quiet and work better with turbulent air, particularly if your getting side gusts, they are the best choice for use in an urban or semi- urban site, such as mine.

I am pretty impressed, none the less, with the performance curves of the We Power Falcon series of VWAT's. For the 3.4 kW model, they claim an output of approximately between 50-200 watts of power O/P for wind speeds of between 2-5 m/s. I know this is an approximation, but I would like to eventually do some testing to verify this. They list they're maximum output at 13 m/s. I think that could be extended through the use of a low speed alternator and rotor as well. You could then design a higher power generator to handle the higher rotational speed, which is one of the advantages of the VWAT over the HWAT. This would have the benefit of giving you a much greater range of usable voltage. And to give you even greater control over the output voltage, you could still make use of the switching between the delta and star configurations.

If you look at the Falcon 12 kW version, they list a power O/P of about 1000 watts at a low wind speed of 5 m/s. Mind you that is a very large massive unit.

Has anyone else looked at extending the range of usable power?

fluxable · « **Reply #40 on:** January 15, 2010, 10:53:14 AM »

To make up for that loss in resistance as you mention, could you not reduce the width of the coils, due to the smaller wire diameter, and thus increase the number of them in the stator. I realize that there is greater resistance with a smaller wire diameter. On the plus side, you can pack in a higher density of copper using smaller diameter wire. Somehow, I think you should be able to compensate for that reduced resistance through higher copper density?

fluxable · « **Reply #41 on:** January 15, 2010, 10:55:43 AM »

One method would be to wrap several strands of smaller gauge wire together (in parallel).

fluxable · « **Reply #42 on:** January 15, 2010, 11:12:26 AM »

I was just thinking, this technique could be used to avoid making a second rotor and stator. Essentially, you could build two generators by using 2 or more windings per coil in the stator, giving you connection options to optimize your usable voltage O/P.

ChrisOlson · « **Reply #43 on:** January 15, 2010, 12:44:09 PM »

Now I'm really not following your thoughts. It'a apparent you've never built a generator so perhaps you'll have to build what you're talking about and let us know if it works.

I think you'll find, just like Hugh said too, that you've reached the point of no return. There's no power in low speeds and the power available increases with the cube of the wind speed. So going to great lengths and expense to extract about a 1/4 watt out of wind that barely turns the turbine rotor is an exercise in futility.

--

Chris

fluxable · « **Reply #44 on:** January 15, 2010, 01:23:53 PM »

You're right Chris, I've never built a generator. But, what I'm trying to accomplish, is get some usable power output with wind speeds in the 2-4 m/s range. I think this is feasible with a large diameter turbine. The other limitation is the upper limit of wind velocity, ie above 15 m/s or so. Many generators will max out beyond this. I am looking at extending this usable power range, and still producing a voltage that is usable, even if to trickle charge battery banks. If you look at the power curves of the larger size PacWind Falcons, as I posted earlier, there is some usable power in that wind speed range. But I'm not sure how accurate those graphs are? The graph also stops at about 13 or 15 m/s as well. Not sure where they max out at for their upper limit? I am just proposing that this usable range can be extended on both ends.

ghurd · « **Reply #45 on:** January 15, 2010, 03:49:26 PM »

they run quiet and work better with turbulent air,

they are the best choice for use in an urban or semi- urban site,

etc.

look at = the sales brochure of companies selling crap here =

"Has anyone else looked at extending the range of usable power?"

Is that a real question?

Like nobody ever thought of that before?

There is no usable power at wind below 6MPH, especially is a micro system.

That is what they are trying to tell you.

ChrisOlson · « **Reply #46 on:** January 15, 2010, 04:08:14 PM »

Looking at your situation, it's my opinion that you'd be much better off with a small, fast turning 75-100 watt HAWT to get what you want out of the low wind speed. A properly designed little HAWT will start spinning with the slightest breeze and can be designed to easily reach cut-in and charge batteries with a few watts in low wind speeds that you're talking about.

The thing to remember is that rpm's is a good thing when you're driving generators because it allows reduction of the amount of wire you need in the generator (and hence, resistance) to make useful power. Frankly, the VAWT is just not the design to use for that.

I came up against the same thing that you're battling with my VAWT project and that's why I shelved it for awhile. VAWT's, despite the claims, are not as efficient as HAWT's. They're not as practical as HAWT's. And they're bigger and require a stronger tower than HAWT's.

So my suggestion is, if you've never actually built a wind turbine before, start with a HAWT to get your feet wet and go from there. Most of the work in building a HAWT will be on the generator. The rest of it is pretty simple stuff and you can even make a set of cheap PVC blades (under 2' or so) to get started, then work your way up from there.

The bottom line is that a little HAWT can spin hellacious rpm's in moderate wind which makes building the generator simple. You'll learn a lot from starting with a simpler project and you'll get more useful power of a little HAWT. If you're set on building a VAWT you're going to have to eventually reach the realization that it takes a pretty big contraption to make any useful power at all and it takes just about gale force winds to make them really perform.

--

Chris

dbcollen · « **Reply #47 on:** January 15, 2010, 04:34:03 PM »

I have for sale a coffee can sized VAWT that produces 1,000,000 Watts in a 1 MPH wind, and since it is so efficient it can even be used indoors powered by the wind from your ceiling fan. Would you like to buy one?

Just because someone claims it on the internet does not make it true. Every design has to conform to the LAWS OF PHYSICS!!!!

Dustin

fluxable · « **Reply #48 on:** January 15, 2010, 05:14:28 PM »

Chris, your last statement summarizes what I'm actually looking at doing. I do realize that to generate any useful power with an HAWT, I'll need a big contraption! This I've known for some time. So building a small unit, other than for learning purposes, or yard art, is a big waste of time for the purpose of generating usable power. My plans are to build a small scale VAWT for the purpose of learning, and then scale it up with a larger unit. And I'm planning to look into extracting as much power as possible, whatever the wind speed.

fluxable · « **Reply #49 on:** January 15, 2010, 05:39:23 PM »

So are you saying that a VAWT is a better choice than a HAWT in a residential area? Not from the research I've done. I know. A residential area is not the best place for any wind turbine. But the semi - residential area I currently live in is my only option for wind generation at the moment. When the wind blows, I do get a lot going through my property. And I'm interested in harnessing some of that energy.

Quote: ""Has anyone else looked at extending the range of usable power?"

Is that a real question?

Like nobody ever thought of that before?"

I think every wind turbine manufacturer has looked into extending the wind operating range. In fact they list the turbine cut in and cut out speeds, and will advertise the fact if their turbine has better performance for either a lower cut in speed, or higher cut out speed. And I'm talking about legitimate companies, not the bogus ones.

Quote: "There is no usable power at wind below 6MPH, especially is a micro system.

That is what they are trying to tell you."

I think you could rephrase that with there is LITTLE usable power below 6 MPH. With a small turbine it is not worthwhile as both you and I previously alluded to, but with a bigger turbine, there is SOME usable power below 6 MPH. Actually I was thinking in the range of 2-4 m/s where some extra could be picked up. There is also room on the upper end to extract power, particularly with a VAWT, IMO.

fluxable · « **Reply #50 on:** January 15, 2010, 05:43:14 PM »

You sound like a good salesman hahaha!

Perry1 · « **Reply #51 on:** January 15, 2010, 10:16:23 PM »

T

h

i

s

i

s

r

e

a

l

l

y

t

h

i

n

.

Kwazai · « **Reply #52 on:** January 17, 2010, 10:36:01 AM »

You would want to build two generators(not necessarily coaxial), one with low magnetic drag, and one for max output and switch them in and out based on the rpm of the mill?. Most of the drag type turbines are speed limited (never run faster than the wind), whereas lift types run faster than the wind (tsr). not sure how you would switch the gennies in and out-possibly a centrifugal clutch? or two?

You need to do a site survey to see what kinds of winds you've got- my evening breeze around here spins the 5' black mill at .6m/s, but won't turn a bicycle generator till well above 3m/s (bicycle gennies are notoriously high drag).

You mentioned a 3m size, I'm assuming thats height -how large a diameter? It would need to be very light(low moment of inertia)and well balanced to take any advantage of low winds.

L8r

Mike

fluxable · « **Reply #53 on:** January 17, 2010, 12:32:14 PM »

I was actually thinking 3 m in width Mike, but that is very large I know, and would be quite a challenge to build both light and strong, and keep it balanced as you mention. If you could build something that size and keep it light, it would have far more torque than a narrower version, and potential to generate something in lighter winds. I think lift type turbines are the way to go, as they run more efficiently than the drag type.

I was thinking of building essentially 2 generators on the same axis, using separate rotors and stators. The smaller one ideally would have a larger rotor diameter, and could incorporate more windings, in order to generate a usable voltage at a lower speed. The large one would be built with heavier wire in the coils on a slightly smaller rotor and stator diameter to take advantage of higher winds. The two could be switched electrically using a speed sensing circuit and relays.

Yes, I should be analyzing winds here at my site. Average wind speeds at a nearby airport are 3-4 m/s overall throughout the year, not very substantial I know. Winds here are often light (2-5 m/s) or even non existent, but then we get windy spells that can be over 15 or 20 m/s. We rarely get gusts in excess of 100 km/hr. With such light winds, I'm wondering if it's even worthwhile.

ghurd · « **Reply #54 on:** January 17, 2010, 12:58:23 PM »

Might be better off looking at Star-Delta type switching,

And probably better off with Star-Jerry switching (easier too, BTW).

G-

fluxable · « **Reply #55 on:** January 17, 2010, 01:47:09 PM »

I will consider these options when designing, thanks!

wooferhound · « **Reply #56 on:** January 18, 2010, 01:30:07 PM »

If you did any research at all on here you would have found out that, if you took all the magnets, wire and steel that it would take to make 2 turbines, and used them to make 1 turbine, you would end up with a machine that makes 4 times the power.

I think everybody comes up with this dual stator before they learn better.

fluxable · « **Reply #57 on:** January 18, 2010, 03:58:03 PM »

Yes, I agree with what you're saying wooferhound. What I'm planning is not necessarily making the most efficient use of the magnet, steel and copper, but in efficiently capturing the power of the wind at various wind speeds for a given turbine size.

I think this link better explains that:

http://www.thebackshed.com/windmill/articles/StaggeredStators.asp

And thanks for all the links you posted, I checked out everyone!

wooferhound · « **Reply #58 on:** January 18, 2010, 07:19:52 PM »

Cool

If your dead-set on building a dual stator machine, then there will be lots of ideas and advice in there.

Kwazai · « **Reply #59 on:** January 19, 2010, 05:53:48 AM »

with it that wide you will probably want to look at the darrieus type turbines with a small savonius in it to get it started. not sure what a minimum wind needed would be, but it would be a lightweight vawt mill. I've been thinking about putting one together from styrofoam model airplane wings . I've seen a few that look rickety but seem to turn alright, I'd be thinking to triangulate the supports with guy wires for the wings to get it to a little stiffer configuration. The lenz types would be worth investigating too (though they look to be a little heavier though). With a 3m width, you're probably looking at a car front hub (volvo? or pinto?) to support it and could bolt steel angle 'wing' supports to it. My brother suspended one of the hvac blower wheel types from a tree- seems to spin pretty well-its about 2ft diameter, 3 ft tall (venetian blinds on a pair of wooden discs).

My blackwindmill -gennie thoughts have ranged from a moveable stator (in and out) to reduce the drag, to electrically excited alternator with small mag gennie for the field coils (so the drag could go up with the increased rpm- reach cut in speed sooner?). Hadn't built one yet (electrical gobbledegook hasn't been my thing), since my site is less than marginal for wind and I really hadn't seen a 'good' way to fit the necessary parts to the bicycle wheel.

The black windmill I've got has a bent front bicycle fork to offset the mill itself from the rotation axis and it tracks the wind fairly well without a tail. I mounted it about 12ft above the ground so neighborhood kids wouldn't get hit by it if they were near it (occasionally they do cross the yard)- something else to consider with one on the ground (vawt). My next one will be big enough to just miss the fence and should be about 10ft corner to corner.

Mike

GWatPE · « **Reply #60 on:** January 24, 2010, 02:15:53 PM »

Wind the stator for the high wind speed, rpm, for the system voltage, power as per instructions available from this site. Use a 3phase capacitor voltage multiplier[doubler in simplest form], [or other DC-DC boost arrangement designed for windmill loading] to get the power at the lower windspeeds. We are not talking many watts, so big components are not necessary.

No rpm sensing or relays would be needed. get the benefit of star/delta switching without the relays.

simulators are available to allow cap sizing to be determined.

Gordon.

News:

Author Topic: Wind generator design options? (Read 11297 times)

KilroyOdin