the Otherpower.com Discussion Board || NEW! And revolutionary VAWT .

Front Page - [Homebrewed Electricity-- (wind) (solar) (hydro) (steam) (controls) (storage) (mechanical)] - Classifieds - Site News
Everything - Newbies - [Remote Living-- (housing) (heat) (light) (water)] - Rants & Opinion - Diaries - Our Products

NEW! And revolutionary VAWT .
By wdyasq, Section Rants & Opinion Posted on Mon Jul 30th, 2007 at 12:27:09 PM MST
Fantastic power

I came across this:
http://pacwind.net/
According to their claims, it makes 10kW at 28mph wind. For comparison, a 4m diameter HVAT is about 5% larger and about 25% of that output using realistic numbers.
I am glad to see Betz law finally getting shredded. There is a new day dawning in America and it is being lead by the VAWT.
I believe Pac-Wind will do for small wind-turbines what GM did for the diesel in America.
Ron

NEW! And revolutionary VAWT . | 56 comments (56 topical, 0 editorial)

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#1)
by bob golding (photoman290 at yahoo dot com) on Mon Jul 30th, 2007 at 06:43:36 AM MST
(User Info)

hey ron, someone steal your horse? did you sell it to woof? i think we should be told.

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#2)
by wdyasq on Mon Jul 30th, 2007 at 07:13:58 AM MST
(User Info)

bob,

I just don't know.

It seems scoop has my signature picture hidden. I had traded the Horse for a combine a few daze ago. Now, scoop has absconded with my combine!

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

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#4)
by TomW on Mon Jul 30th, 2007 at 07:44:11 AM MST
(User Info)

Ron;

Scoop only adds the .sig line to comments not stories, if thats what you mean by hidden.

"Education consists mainly of what we have unlearned."--Mark Twain
[ Parent ]

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#3)
by Nando (nando37-at-tx-dot-rr-dot-com Correct theanti-spam) on Mon Jul 30th, 2007 at 07:18:57 AM MST
(User Info)

ONE MUST REMEMBER that no wind mill will be able to HARVEST more energy than the wind can have at any time.
BETZ still is the KING of the Wind for many more centuries.

Nando

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#5)
by wooferhound (tim((NoSpamAt))wooferhound.com) on Mon Jul 30th, 2007 at 09:11:00 AM MST
(User Info) http://wooferhound.com

You can beat the Betz limit if you buy some of that stuff on eBay

W o o f -={(

[ Parent ]

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#56)
by finnsawyer on Wed Aug 8th, 2007 at 09:28:05 AM MST
(User Info)

"ONE MUST REMEMBER that no wind mill will be able to HARVEST more energy than the wind can have at any time."

This is obviously true, but the the Betz Limit only deals with the kinetic energy, not the total energy. The kinetic energy can increase without changing the total energy due to the presence of a "Venturi" structure. This in turn results in a greater power flow due to that "velocity cubed" term. It is odd that something that should be fundamentally obvious can generate such resistance. In fact it should be obvious that in an ideal step down down tube type Venturi where the area is cut in half that the speed must double to keep the mass flow constant. This results in four times the power flow due to that velocity cubed term (1/2x8).
GeoM
[ Parent ]

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#6)
by Tritium on Mon Jul 30th, 2007 at 10:53:49 AM MST
(User Info)

An OU wind turbine?

Thurmond

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#7)
by whiskey (itswhiskey at_ g_mail do t com) on Mon Jul 30th, 2007 at 12:10:06 PM MST
(User Info)

Where is Dougie Salesman when you need him?

"I have solved the energy crisis".

I digress, and agreed with Ron, what ever next :)

Whiskey

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#8)
by dinges on Mon Jul 30th, 2007 at 12:19:08 PM MST
(User Info)

I am happy too that we finally got rid of that pessimist Betz. He has done too much damage to the wind industry, suppressing creative new ideas that could have solved our energy problems long ago.

We don't need any Betz and the likes of him.

What we need is more people who can think outside of the box. Like Pons and Fleischmann

But I do think you need to do a little more research and reading: I have never heard of a 'HVAT'. Or is it -because- of all that research that you know what a HVAT is and I don't ?

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#9)
by vawtman (vawtman(at)charter(dot)net) on Mon Jul 30th, 2007 at 03:11:03 PM MST
(User Info)

Ron
Betz isnt being shredded by the delta 2 turbine your thinking of but its right at it though.

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#10)
by dinges on Mon Jul 30th, 2007 at 04:03:11 PM MST
(User Info)

Power available from the wind:

P = .5 * rho * A * v^3 * Cp * Ng

P = 10.000 W (their "rated value")
rho = 1.225 kg/m^3 (assuming standard atmosphere)
A = 12 m^2 (FULL frontal area...)
v = 12.4 m/s (28 mph, their "rated value")
Cp= coefficient of performance (should be < Betz=0.59)
Ng = generator efficiency; set to Ng=1 here

With these figures, solving for Cp, I get Cp=0.71)

Which means they get 71% of the energy of the wind from what's actually available.

So they beat Betz.

Now, this Cp was calculated using a frontal area of 12 m^2, assuming that the entire frontal (projected) area of the turbine generates power. Which it doesn't. I think half of the area is more closer to it, but I know too little of VAWTs to make a better guess. Smaller area means their (implicitly) claimed Cp gets even higher.

This was assuming that Ng, generator efficiency, was 1 (100%). I usually calculate my gennies for Ng = 0.70-0.75

If one would take these corrections in account, they would achieve overunity.

They either deserve a Nobel prize for physics or prosecution for fraud/misleading advertising.

I don't think they'll get either though.

Not only that, I notice two different diameters for their 'delta-II':

In this file it says dia = 158"(4 m) (http://pacwind.net/download-pdf/Delta_II7-23-07.pdf)

In here, it says dia = 96" (http://pacwind.net/):

"Physical Specifications:
Cage Height 120 inches
Cage Diameter 96 inches"

(I originally calculated using the 96" value and arrived at a Cp=1.15 instead of .71, wondering where my error was as I verified the calculations. Seems they give two entirely different diameters for the same product in different places).

Whatever way, even calculated 'in their advantage', they beat Betz. Depending on some other (realistic) assumptions, they even achieve overunity.

But I'm not even sure which data is the right one for their product. 96" diameter ? 158 " ?

Caveat emptor.

[ Parent ]

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#11)
by vawtman (vawtman(at)charter(dot)net) on Mon Jul 30th, 2007 at 04:23:11 PM MST
(User Info)

Peter heres a little calculator that i play with.
http://users.xplornet.com/~rmanzer/windmill/hrotor_calculator.html

I believe Reg used Paul Gipes figures for it.

It doesnt facter in solidity or anything but you can see the max possible for different turbines.

[ Parent ]

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#12)
by dinges on Mon Jul 30th, 2007 at 04:56:05 PM MST
(User Info)

If I've made an error in my calculations or assumptions, I'd like to hear it.

Apples and oranges.

Your calculator uses average windspeed as input, along with Rayleigh distribution to guesstimate annual average power output. It's a very different calculation from what I've been doing, which is basically determining maximum output power available from the wind.

I wouldn't use it for what you use it for: estimating max. possible for different turbines. I don't like the Rayleigh distribution thrown into this, for that sort of calculation. I'd use the equation I've used for that.

Whenever using someone else's data, equations, calculators, etc. it's important to know what the underlying assumptions are and what the goal is of the calculation.

If you want to know average power output, or total power output, over a year, your calculator (having as input avg. windspeed with Rayleigh weighting) seems ok. For calculating max. power output of a turbine, or trying to calculate efficiency of a generator, I'd use my method.

You just gave a wonderful illustration of why I dislike all those online calculators and graphs. They usually don't show their goal, how-to-use, assumptions, underlying equations, etc. (yours shows its equations though, which is already a major step forward from many calculators).

But all this is just fiddling in the margin as long as we don't know whether the turbine is 96" or 158" in diameter...

[ Parent ]

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#13)
by vawtman (vawtman(at)charter(dot)net) on Mon Jul 30th, 2007 at 06:23:34 PM MST
(User Info)

I was just trying to show what would be the actual limit for the swept area.

In reality who cares.
High solidity in winds less than that would do better.A betz beater vawt probably wouldnt start at winds less than that 28 mph unless helped.

Just thoughts
Mark

[ Parent ]

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#14)
by dinges on Mon Jul 30th, 2007 at 06:43:51 PM MST
(User Info)

"I was just trying to show what would be the actual limit for the swept area."

I know. And you are wrong :)

The actual limit for the swept area is shown in my calculation. 'your' calculator throws in a fudge factor, the Rayleigh distribution, that is totally irrelevant for determining maximum instantenuous power of a wind turbine.

As to who cares. Hm. Suppose we weren't talking about windgennies but about cars. Does your car have a maximum speed of 220 km/hr as advertised, or 130 km/hr in reality? Would I care? Not if it were your car, I would if it were mine.

Someone once sold me a 20 W PV panel that in reality was a 10 W panel (with MPPT; without MPPT it's just 7 W). I care.

"A betz beater vawt probably wouldnt start at winds less than that 28 mph unless helped."

Easy now... Please read again what you wrote.

Betz beaters don't exist; you seem to assume they do.
Betz, IF it could be beaten, could just as well be beaten at low windspeeds as at high ones. But it can't.

[ Parent ]

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#23)
by finnsawyer on Tue Jul 31st, 2007 at 08:43:20 AM MST
(User Info)

We've been around on this Betz limit thing before. We all know that the air flow speeds up when the air flows around an object, and the faster moving air is capable of producing more power per unit of frontal area. It is quite possible that structural items necessary to the construction of the VAWT might produce a sufficient speed up in the air to beat Betz relative to the undisturbed incident air flow. For instance, placing a substantial cylindrical core in the mill might speed up the flow across the foils to such an extent that the Betz Limit is actually exceeded when the power output is compared with the theoretical power input from the undisturbed flow across the VAWT's area assuming 100% solidity. You may have noticed that these people do manufacture a 500 watt unit that has a large cylindrical core.

You may not like this way of looking at it, but this mirrors reality. The builders of any type of mill are going to compare the power output of the mill with the power available in the undisturbed air flow. I believe there have been other claims that VAWTs can exceed the Betz Limit. The idea that speeding up the flow can some how gain one more power than the incident air has may be a tough one to swallow, but there are mathematical solutions for fluid flow around a sphere and cylinder that bear this out. You can check that out for yourself.
GeoM
[ Parent ]

one word: system boundaries (3.00 / 0) (#26)
by dinges on Tue Jul 31st, 2007 at 10:44:45 AM MST
(User Info)

GeoM,

Of all people (I understand you have a technical higher education) I thought at least you would be familiar with a concept known as 'system boundaries'. An important one in this respect; what is a system, where does it start and where does it end.

I have seen remarks by you on this board before where you claim that hills, large buildings, etc. speeds up the air that a windmill sees. Which it can.

However, to claim that this 'beats Betz' is nonsense; for a proper analysis you would have to take the larger, artificial frontal area of the windmill (which is in effect being largened by the hills/buildings/extra ring on the windmill) into account. Or the higher airspeed that the windmill sees at its frontal area.

By creatively setting your system boundaries you can indeed achieve 'overunity'. Within your (badly defined) system. But last time I checked there was still this thing called entropy.

I don't like Betz's limit, and I don't like the limit of the speed of light either. But what I like or don't like is entirely irrelevant.

But anyway, I'll pose another challenge to you: not only to build your radical new generator design, but also to build a Betz-beating windmill. Be a sport and take up the challenge.

Regards,

Peter.

[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#29)
by finnsawyer on Wed Aug 1st, 2007 at 08:42:26 AM MST
(User Info)

You correctly invoked the effect of hills on the wind flow. You seem incapable or unwilling to go beyond what you already know or think you know. There is an interesting phenomenon that shows up around here, which you may never see where you live. We get upwards of three feet of snow on the ground in the woods. There will appear around the trees a saucer shaped depression that extends out about one radius from the tree. Now, this is not due to the sun, which never shines on the north side of the tree in the winter. It must be due to speed up of the air as it goes around the tree. This speed up, which is twice the incident air speed, means there is available eight times the energy next to the tree trunk to scoop out the snow. Of course, the effect decreases both away from the tree and with depth in the snow, so it is limited in scope. Nor does nature seem to feel that this violates any thermodynamic laws. The important thing is that the wind is doing more work as a result of the speed up than it would do with no speed up of the air. After all, the air flow doesn't remove all the snow everywhere. If the air does more work in that case, then the effect can be put to use by proper design. Nature does what it does and you would do well to pay attention.

One note here. The depression scales up with the diameter of the tree, which is consistent with the theory for fluid flow around a cylinder.
GeoM
[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#30)
by dinges on Wed Aug 1st, 2007 at 11:03:20 AM MST
(User Info)

I have little doubt that the effect that you observe (snow depression around trees) is real. I have strong doubts about your interpretation of it, that it means you can extract more energy out of it, of beating Betz.

Let's see; an imaginary cylinder of air, containing a certain amount of energy, all of a sudden can do more work as it passes a tree?

Where does the extra energy come from ?

I have learnt, in my thermodynamics, aerodynamics and aircraft instrumentation classes, that the amount of energy in a given amount of air stays the same, no matter whether one compresses it, speeds it up or slows it down (with e.g. a venturi), etc. The Total Energy (potential energy and kinetic energy, or, in this case, static pressuse p (p = m*g*h) and 'stuw' pressure (sorry, only know the correct Dutch word for it) q=1/2* rho*v^2) in a given amount of air stay constant, unless one adds energy (by means of a fan, for example) or removes energy (by means of a windturbine, for example).

(The TE=constant rule assumes that there's no friction/viscosity with air; there is in real life, so the friction heats up the air as it loses kinetic energy. But hey, guess what, as it loses kinetic energy, it gains heat energy. Could it be that the TE , when it also includes thermal energy, stays the same after all, even including friction effects ? OMG. I guess the thermodynamic laws may be true after all ?!)

Air flowing through venturis or around objects does NOT majically gain extra energy (we need energy to do work). Even worse, due to friction it LOSES energy!

But we're getting far removed from the original topic: the Cp of that VAWT. If I have made an error in my calculations or assumptions I would have liked to know. I'm assuming that, since no one corrected them, they were correct.

I suggest you contact PacWind with your observed phenomenon. They may be interested in incorporating the effect in their future Delta-III product.

This is my last comment on the topic.

Kudos to Ron, he did it again...

[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#31)
by finnsawyer on Thu Aug 2nd, 2007 at 08:40:57 AM MST
(User Info)

"I have learnt, in my thermodynamics, aerodynamics and aircraft instrumentation classes, that the amount of energy in a given amount of air stays the same, no matter whether one compresses it, speeds it up or slows it down (with e.g. a venturi), etc"

That is a strange statement since everyone knows that if you speed up a mass it has more kinetic energy. You have contradicted your own statement about the effect of hills in the air flow. Similarly, if you compress a gas its internal energy increases. Of course, we are not talking about Carnot Cycles here. In fact, the accepted model for the air's behavior is the same as that for water, at least for air speeds less than 200 mph.

There appeared on this site at one time a posting about a power generating facility on a German river which utilized the constricting of part of the river's flow rather than a dam. The claim was that that was at least as effective as damming the river, due to the large increase in kinetic energy that resulted, that velocity cubed term. So, presumably, one could do similar things relative to the air flow. My claim is that a (simple) analysis of the two cases that I presented reinforce that conclusion. And I have presented in general terms the procedure to follow. What I don't understand is why someone like yourself, who claims to know all the fundamentals, chooses to ignore a simple challenge. Is it because it wasn't presented by a Professor in a class room?

GeoM
[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#32)
by whatsnext on Thu Aug 2nd, 2007 at 10:36:17 AM MST
(User Info)

GeoM, What I don't don't understand is why you don't build a simple test mill incorporating your ideas and show us all how well it work. If the air or water speeds up due to some restriction then the energy required to cause that increase in velocity has to come from somewhere. So it isn't some sort of "free energy" that you can harvest. Once you put something in it's way to harvest anything you will be creating another restriction that will have an effect on on the air before it has a chance to reach your harvesting device.

[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#37)
by finnsawyer on Fri Aug 3rd, 2007 at 09:06:02 AM MST
(User Info)

My building it wouldn't prove anything, since I don't have access to a wind tunnel to make the accurate tests that are needed. All you have to do is read this thread and others like it to see that anyone making any claims that look too good isn't believed anyway. That doesn't mean we can't discuss the theory. There are people frequenting this site like the fellow I'm been having this discussion with that certainly have the ability to do the analysis to test the validity of my conclusion. What is mysterious is that everyone seems to think I'm trying to pull some kind of fast one. I could present the analysis, but chose not to, as I'd like to see what others might come up with independently. I could be mistaken, but all the evidence I,ve seen seems to bear out the conclusions: One could get a power boost of 22% with a sphere or 78% with a cylinder.
GeoM
[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#33)
by dinges on Thu Aug 2nd, 2007 at 11:33:12 AM MST
(User Info)

You read selectively, don't you?

"That is a strange statement since everyone knows that if you speed up a mass it has more kinetic energy."

Notice how I said: "with e.g. a venturi". Notice how I was also in another part talking about the TOTAL ENERGY staying THE SAME if you don't put extra work or extract WORK from the air.

Which was an example to show how its possible to increase the speed of air WITHOUT adding extra energy. A Venturi manages to speed up air and decrease the pressure whilst TE stays the same.

"Similarly, if you compress a gas its internal energy increases. "

If you COMPRESS energy you put WORK into the gas, hence you INCREASE its energy

"What I don't understand is why someone like yourself, who claims to know all the fundamentals, chooses to ignore a simple challenge. Is it because it wasn't presented by a Professor in a class room?"

Are -you- now asking -me- to prove -your- erroneous ideas ? Just like a while ago you challenged -someone else- to build -your- generator design to prove -you- are wrong ? Isn't that the world reversed?

Is that the scientific method they taught you at MIT ?

I was taught to disprove my own theories and ideas.

As good old Edison said, 'Genius is 1% inspiration and 99% perspiration'.

You want me to do the perspiration for you?

[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#38)
by finnsawyer on Fri Aug 3rd, 2007 at 09:27:15 AM MST
(User Info)

I don't know why you emphasize a 'Venturi' since it does not aply to this case, as I point out in another comment on this thread. You might check the other comments.

Actually, I'm inviting you to disprove my 'erroneous' ideas. But we need to start from a common point, which would be the known solutions for fluid flow around a sphere and a (long) cylinder. If you chose not to accept them and their ramifications that's your choice. But they are out there.

I think you're a bit off base with some of your criticism. If everyone was expected to disprove their own ideas nothing would ever happen. It is only through the cross fertilization of ideas that different perspectives quickly become apparent. That's why people publish. Is your attitude of shooting down new ideas without testing them indicative of how you do things in Europe now? No wonder Europe is stagnating.

GeoM
[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#39)
by Countryboy on Fri Aug 3rd, 2007 at 10:41:24 AM MST
(User Info)

Actually, I'm inviting you to disprove my 'erroneous' ideas.

George,
You can't prove a negative. Only an idiot attempts to do that.

It is YOUR responsibility to prove your assertions. No progress will EVER be made if everyone is wasting their time disproving erroneous things. Progress is made when people put their time and energy into proving good ideas.

[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#41)
by dinges on Fri Aug 3rd, 2007 at 06:51:26 PM MST
(User Info)

Countryboy,

One can not prove one is right, one can only prove someone is wrong. Which is why hypothesis should be made in such a way that they can be falsified. The fact that a theory is accepted doesn't mean that it's correct, it means just that we haven't been able to disprove it yet. If not, it's pseudoscience.

The scientific method indeed relies a lot on peers disproving theories of others.

I will not be taking up GeoM on his offer though; in post #36 he stated that 'thermodynamics do not apply'. If he believes that is correct then I could never convince him. He has just discarded the most fundamental principles of physics (the laws of thermodynamics are the foundation of physics). Without these laws it's no longer physics but theology.

As RonB said, they apparently not only retracted Betz but also retracted the Laws of Thermodynamics. A new day is dawning indeed.

That's the first thing.

Secondly, I think I can spend my time in better ways. One thing I've learnt over the past decade is that one should learn not to argue with just about everyone on the internet. I reserve that argueing for only a few special people.

As to the Venturi effect; GeoM seems to think it doesn't apply to his tree/building example.

I say it does. A venturi is representative of an obstruction of the airflow, just like a tree. Air passing that tree will speed up and as a consequence (because total energy MUST stay the same) its pressure gets less (yes, less). This means too, btw, that rho gets less, i.e. the air becomes less dense and can do less work because of that. It can do more work because of the higher speed. The two will perfectly compensate eachother as the energy can not magically appear or disappear (ignoring friction; but even with friction it wouldn't change TE: TE = potential energy + kinetic energy + thermal energy = constant)

Notice that as the air speeds up, the 'mass' of air that passes through the windturbine per unit of time doesn't change. And neither does its total energy. If its kinetic energy increases, it will come out of its potential energy. And notice that Betz doesn't say you can extract 59% of kinetic energy but 59% of the -energy- of the wind.

As I said, a tree and a venturi have a thing in common: they're both an obstruction to an (imaginary) cylinder of air. GeoM fails to look at a venturi as anything else than 'a tube'. And that's how it's usually drawn in the textbooks. Truth is, there are lots of venturis in the real world, with or without a physical tube. Bernouilli still applies, with or without any physical tube. Whether it's a tree in the field or an Althaus venturi mounted on a Ka-8b.

So, counterintuitive as it may seem at first sight, pressure gets REDUCED as the wind speeds up.

Hope this explains it a bit Countryboy. If not, pop in in IRC sometime again; missing the odd discussion with ya. ;)

Regards,

[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#42)
by vawtman (vawtman(at)charter(dot)net) on Fri Aug 3rd, 2007 at 07:47:53 PM MST
(User Info)

Why dont you guys just build a turbine and take what you can get?Then worry later on if your not happy.

[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#43)
by TomW on Fri Aug 3rd, 2007 at 07:58:04 PM MST
(User Info)

vawtman;

Peter does build [at least one alternator anyway] which should say something.

Just to put a proper light on things. Doer, Not Doer. You draw your own conclusions.

The proof:

http://www.anotherpower.com/gallery/album46

Cheers.

TomW

"Education consists mainly of what we have unlearned."--Mark Twain
[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#44)
by dinges on Fri Aug 3rd, 2007 at 11:47:13 PM MST
(User Info)

For completeness sake: Betz says you can extract maximum 59% of kinetic energy, not of (total) energy. My previous remark was incorrect.

Vawtman, I agree with you (gasp; what's next ?! ;) .This is all idle chatter if it doesn't result in better windgenerators. Seriously. I disagree with quite a few things you do/build, I think there are better/simpler ways to achieve the goal, but in your defense, you build and don't just armchair philosophize about it till you see blue in the face. At the end of the day theory is just theory. The proof is in the flow of the electrons.

I've been following your large wheel/wooden stator radial flux with interest though I would do just about everything differently from you :) But that's ok, it's your project. You do yours your way, I'll do mine my way.

Ah well. At least we both would like to stay in Oztules' container/luxury apartment. I haven't received an invitation yet though [hint, hint, Oztules].

Just so you don't get the wrong idea about this entire discussion.

Regards,

[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#45)
by oztules (oztules__at__bigpond.com) on Sat Aug 4th, 2007 at 01:41:44 AM MST
(User Info) http://www.anotherpower.com/gallery/Oztules-toys

You don't need an invite Peter.

Anyone who is prepared to spend their time to selflessly do a complete thesis on decogging steel stator machines in the interest of the many..... is instantly recognised as family.

Bring your own toothbrush though. (if Ron turns up a gas mask may be in order as well) :)

...........oztules
Flinders Island Australia
[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#48)
by finnsawyer on Sun Aug 5th, 2007 at 09:57:25 AM MST
(User Info)

For a minute there I thought you had deflated the argument with the "new" interpretation of Betz. In that case, what I maintain wouldn't be an issue for you, since the increase in energy flow per unit time comes from the energy available from the drop in pressure or the potential energy (see my latest response to Countryboy). That's the crux of the issue, as Bernoulli's equation is really a conservation of energy equation. In order to get the air to flow around the tree (or sphere or any obstruction) nature takes energy from the potential energy (pressure) and transfers it to the kinetic energy. This gives a 78% increase in the kinetic energy in the region around the tree, which is potentially available for harvesting. It is similar to the effect of a hill, where a VAWT will harvest more power than on the plain. The difference is that it can be made part of the structure and controllable.

You are the one who introduced thermodynamics with your statement about entropy. If, as you suggest, the density changes, then one would need to consider thermodynamic changes. I have seen no evidence of such a need and the model I am using does not require a change in the thermodynamic quantities. I was trying to convey that that was my position.

"Notice that as the air speeds up, the 'mass' of air that passes through the windturbine per unit of time doesn't change. And neither does its total energy."

I think you are going to want to retract this statement. It's pretty well accepted that for a turbine in free air, if the wind velocity doubles, then the power flow or energy per unit time through the turbine will increase by a factor of eight. Why don't you take a hard look at the step down 'tube' Venturi, as I suggested.
GeoM
[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#49)
by dinges on Sun Aug 5th, 2007 at 10:30:33 AM MST
(User Info)

"Notice that as the air speeds up, the 'mass' of air that passes through the windturbine per unit of time doesn't change. And neither does its total energy."

I see how that statement could cause misunderstanding/misinterpretation. Replace 'windturbine' by 'venturi choke'. I'll say a few more things (which you can easily verify for yourself: the massflow (per unit of time) doesn't change. The volume flow (per unit of time) doesn't change. The rho (density) doesn't change.

You still haven't made clear, btw, why you think a windturbine is different from a venturi (apart from the obvious fact that a windturbine extracts energy where a venturi doesn't). Both present obstructions to airflow. Bernouilli applies.

FYI, I have worked the problem out. God knows why I bothered anyway.

Betz is NOT beaten. You can not extract more than 59% of the kinetic energy of the wind.
more kinetic energy is available for more power as the wind speeds up (hint: what happens to the temperature of the air as it passes through a venturi?)
it's all a matter of drawing your system boundaries properly, as I stated before. If you do this 'creatively' as you do here (post #23), you can INDEED 'beat' Betz...

"It is quite possible that structural items necessary to the construction of the VAWT might produce a sufficient speed up in the air to beat Betz relative to the undisturbed incident air flow."

We measure surface area at the windturbine, but we measure windvelocity a few km off, before the hills/buildings have messed with the undisturbed incident air flow.

Last time I saw such creative playing around with figures was when I had to balance the budget for my department.

4) it has been a major waste of my time and effort. And 5 pieces of paper.

You may ask why I don't submit the proof here. I have my reasons. I suggest you do your own homework. You will not be getting another free ride on my back. I have seen so far not a single calculation or direct reference from you to anything. But many vague remarks without proof or references: 'wind doubling', '78%', '22%'. As far as your model goes, I have no idea what you are talking about. I have not seen any model. The only model I have is the one I drew up a few days ago myself.

So, I repeat what I said in my very first (and second) reply in this thread and which you didn't seem to agree with: Betz can not be beaten. Which was what this entire thread, as originally posted by Ron, was all about.

And this, for me, closes the case.

[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#53)
by finnsawyer on Mon Aug 6th, 2007 at 09:28:07 AM MST
(User Info)

Why do you even frequent this site (not to mention the IRC) if your time is so valuable? These issues need not be settled in a day.

As I understand it the Betz limit applies only to the part of the air stream having the same area as the hypothetical turbine when it reaches the turbine. A Venturi can change both the rate of mass flow and the kinetic energy locally. This in turn can have a great impact on the power flow locally through the turbine.

You say you did the problem, but you do not present any results, other than a general statement. What did you get for the power passing the cylinder along the 90 degree line or plane? See my other comment of this date for an explanation. It would be nice if we were comparing the same quantity. The whole thing boils down to power. As you correctly imply nature operates to keep the total mass flow constant. This requires a speed up in the flow around the object, which in turn increases the power flow past the object compared to the undisturbed air. It is the net increase in this power flow that is of interest. What did you get for the maximum value of that power flow as compared to the undisturbed air? Remember, the power goes as the cube of the velocity!
GeoM
[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#55)
by finnsawyer on Tue Aug 7th, 2007 at 08:27:14 AM MST
(User Info)

"You still haven't made clear, btw, why you think a windturbine is different from a venturi (apart from the obvious fact that a windturbine extracts energy where a venturi doesn't). Both present obstructions to airflow. Bernouilli applies."

What is your authority for the statement that Bernoulli applies for the case of a wind turbine removing power from the wind? That would imply that the internal energy of the air was remaining constant as the velocity of the air was reduced due to the loss of kinetic energy. Bernoulli's Equation would then require that the pressure must rise to balance the equation, which puts us in the uncomfortable position of having the potential energy rising at the same time as the total energy was decreasing. It doesn't seem reasonable. It seems more likely that the internal energy of the air must also change, which means Bernoulli's Equation would not apply.
GeoM
[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#50)
by dinges on Sun Aug 5th, 2007 at 10:57:38 AM MST
(User Info)

What I forgot:

You say correctly that as windspeed doubles, kinetic energy goes up 8 times. However, in that case WE PUT EXTRA ENERGY IN THE WIND! Mother nature lets the wind blow harder so more kinetic energy in it.

In the case of a venturi, or your hills or buildings, they do NOT put extra energy in the wind; there is an exchange of potential energy to kinetic energy as the wind speeds up. Laws of thermodynamics state that total energy MUST stay the same.

In the case of a venturi (or your buildings), as airspeed doubles, mass flow does NOT increase. Volume flow does NOT increase. And, rho/density does not change.

When the wind blows harder these things (mass flow/volume flow/rho) may change. But it's an entirely different situation: mother nature puts more energy in the wind in the first place. Your buildings or hills can not do that. So, apples and oranges: in both cases (venturi vs. mother nature) airspeed goes up, but in one case total energy of the air stays the same, while in the last case (mother nature) total energy goes up.

Now if you'll excuse me. I have some work to do on a motorconversion.

[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#51)
by vawtman (vawtman(at)charter(dot)net) on Sun Aug 5th, 2007 at 02:00:47 PM MST
(User Info)

Peter and Fin

It would seem to me standing inside a fat bladed darrius contraption that the blades speed the wind up without mother nature or funnels.
Try it sometime.

Have fun

[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#54)
by finnsawyer on Mon Aug 6th, 2007 at 09:46:48 AM MST
(User Info)

I'm not surprised. When the air passes over the air foil it is sped up. That's what makes the thing work. Wind tunnel tests show the difference in air speed along the top and bottom of the foil can persist after the two streams leave the foil. This can result in the effect you detected. The wake of the most windward blade could affect one of the other blades and, who knows, improve performance. But this would open up another can of worms, and I can't get any kind of agreement on the existing can. You're on your own on that. Maybe you could try a smoke generator to see how the air is flowing.
GeoM
[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#52)
by finnsawyer on Mon Aug 6th, 2007 at 08:54:19 AM MST
(User Info)

I see that I miswrote when I said energy. I should have said power. To clarify, when the wind speeds up by a factor of two, the power or energy per unit time per unit frontal area increases by a factor of eight. This sort of thing occurs any time the air is sped up including when it goes around an object. In the case of the cylinder at the 90 degree line as measured relative to the line of highest pressure (zero degrees) there will be a velocity distribution. If one integrates along this line from the radius of the cylinder, a, to some value of radius, r, one will find the power flowing past the cylinder to that radius at that 90 degree angle. If one allows r to vary, the result will be a curve that starts from zero (where the velocity is greatest) and increases. If one then divides that result by the power flow in the undisturbed air taking it from 0 to r, one then gets a curve that reaches a maximum of 1.78 and then goes to one at large values of r. I don't see why you are having such a problem with this idea considering that you are quite willing to concede that nature obviously transfers energy from the potential energy or pressure to the kinetic energy, which then determines the power flow. The question then becomes whether it is possible to tap into this increased power flow. I believe it is, based on the observation concerning the scouring of the snow around a tree. And if we can channel this higher power air to an air foil keeping the 78% boost then we have effectively beaten the Betz Limit as applied to the incident air flow. This type of effect would occur for any Venturi structure (using your definition) being part of the turbine, particularly for VAWTs, since they inherently require structures other than just blade assemblies. One would think that there would be considerable interest in exploring these possibilities.

As far as the density is concerned, I suppose one could study the difference between water flow and air flow around a cylinder in some sort of a fluid tunnel, but it is generally considered that for low wind speeds we can neglect the change in density.
GeoM
[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#47)
by finnsawyer on Sun Aug 5th, 2007 at 09:07:26 AM MST
(User Info)

You can prove the results to be wrong. That is, a 22% percent maximum increase in the power available from the flow around the sphere or 78% around the cylinder. It should take you less than half an hour to set up the problem and do the integration once you have the solution for the flow around a long cylinder.

You are big on the Venturi. You state there is no change in power flow in a Venturi. So, prove it. We have a fluid of density rho flowing in a pipe of area A at velocity V. The pipe gradually reduces to a cross sectional area Of A1. What is the ratio of power flow in the smaller region to that in the larger region? Perhaps, you only need look this up.
GeoM
[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#35)
by Countryboy on Thu Aug 2nd, 2007 at 10:17:19 PM MST
(User Info)

There is an interesting phenomenon that shows up around here, which you may never see where you live. We get upwards of three feet of snow on the ground in the woods. There will appear around the trees a saucer shaped depression that extends out about one radius from the tree. Now, this is not due to the sun, which never shines on the north side of the tree in the winter. It must be due to speed up of the air as it goes around the tree. This speed up, which is twice the incident air speed, means there is available eight times the energy next to the tree trunk to scoop out the snow.

Where do you get the idea the speed up of the air is TWICE the incident air speed? The change in airspeed and pressure is miniscule - however, that change in airspeed is just enough to keep snowflakes suspended in air as the air goes by the tree.

The tree acts as a venturi. The snow is deposited in the low pressure areas outside the tree.

What you fail to see is that the total energy of the airmass is actually slightly higher than the energy that airflow has. That is because of something known as friction and resistance.

Get rid of all those trees that are providing resistance, and you'll find that your windspeed will actually be faster than it is when it has to blow past trees.

I'd recommend you study how a sluice works to understand the phenomenom you describe. Think of the water flowing over the sluice as the wind, flakes of gold as your snowflakes being moved by the flowing mass, and think of the riffles as the trees.

[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#36)
by finnsawyer on Fri Aug 3rd, 2007 at 08:46:17 AM MST
(User Info)

"Where do you get the idea the speed up of the air is TWICE the incident air speed?"

Any time I walk between two buildings when the wind is blowing I get the effect in my face. This doubling of the air's velocity is not due to me. It has been well known for a long time. In the 70's I saw a proposal for making use of the effect by placing a wind mill on a track around a circular oil derrick. That's not really relevant here. What is relevant is that the mathematical solution for fluid flow around a cylinder exists. It is either correct or wrong. If it is correct than the statements I make follow from an analysis of the situation, something anyone with a rudimentary knowledge of calculus can do. If it is wrong, prove it.

"The tree acts as a venturi. The snow is deposited in the low pressure areas outside the tree."

For the tree the low pressure area is near the tree.

You people want to compare this with a Venturi, which comes about as a result of lowering the air pressure on the output end. You need to look at a Venturi where the air blows into it. You could measure the pressure in the Venturi and some distance before the Venturi to determine the relative velocities and from that determine the power flow in the Venturi relative to the total frontal area of the structure. In any case the process satisfies Bernoulli's Equation, which, by the way requires the internal energy of the fluid to remain constant, so thermodynamic considerations do not apply. The comments about the tree's resistance just obscure the issue.
GeoM
[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#40)
by Countryboy on Fri Aug 3rd, 2007 at 10:49:27 AM MST
(User Info)

Any time I walk between two buildings when the wind is blowing I get the effect in my face. This doubling of the air's velocity is not due to me.

Once again, where do you get the idea the windspeed has doubled? The speed may have increased, but that does not mean it has doubled.

For the tree the low pressure area is near the tree.

The area right around the tree is the high pressure area. Air pressure is increased because of the resistance of the tree. Go punch a wall - your hand won't hurt in the low pressure areas. Use that as a guide to determine where the low and high pressure areas are.

In any case the process satisfies Bernoulli's Equation, which, by the way requires the internal energy of the fluid to remain constant, so thermodynamic considerations do not apply.

You have already alluded to Bernoulli's Equation as not applying, simply because you discount the idea the total internal energy of the fluid remains constant. You have already stated the internal energy changes as the fluid flows around objects.

[ Parent ]

Re: one word: system boundaries (3.00 / 0) (#46)
by finnsawyer on Sun Aug 5th, 2007 at 08:55:41 AM MST
(User Info)

Look, I believe I have two said two things about the situation. One is that Bernoulli's equation applies. No external work is being done until snow is removed around the tree. Secondly, there is a mathematical solution to the problem that predicts the doubling of the speed. I assume you accept the proven fact that the air speeds up and the pressure drops around the convex side of an air foil, but when faced with a different situation that obeys the same physical laws you then say it can't be. If you split the cylinder in half along a plane parallel to the direction of air flow you get two air foils. The convex side of each resulting foil is the side where the air speeds up and the pressure drops. Have you ever wondered why the leading edge of an airplane wing is rounded rather than brought to a knife edge. The obvious answer is that that gives the greatest boost to the speed of the air across the top of the wing and consequently the greatest lift while giving the best lift to drag ratio.

As far as the internal energy is concerned, if you Google "Bernoulli's Equation" you will quickly find a paper that derives the Equation from the stipulation that the internal energy remain constant. When the air goes around any obstruction, including the tree, the speed up of the air is effected through a drop in pressure. If you study Bernoulli's equation carefully, you will find it is actually an energy equation that says the total energy is constant. But part of the energy is contained in the pressure of the fluid. If that pressure is reduced, then the fluid must be moving faster to keep the energy in balance, which means more energy per unit time or more power will be moving across a unit of area. How that energy flow is distributed depends on the problem. Again, the solution for a cylinder states that the power flow is enhanced in a region around the cylinder. This is possible and violates no Laws because the pressure is lower in that region, again, due to the physics of fluid flow.
GeoM
[ Parent ]

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#15)
by CmeBREW (smke833f@hotmail.com) on Mon Jul 30th, 2007 at 06:48:27 PM MST
(User Info)

Yes, I also am impressed--they are doing some good things. How they work, I have NO idea.
Here is more info:

http://pacwind.remnet.com/index.html

Good pictures too.

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#16)
by CmeBREW (smke833f@hotmail.com) on Mon Jul 30th, 2007 at 08:29:54 PM MST
(User Info)

I also liked the Jay Leno installation video of that windmill, below. The blades must be 18" wide or more. Looks like the old 'giant arrow' shape thats been tried countless times since the beginning of windmills. They must have fine tuned it aerodynamically. Think I'm going to try the old giant arrow myself. Couldn't do any worse than my last endeavor.

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#17)
by wdyasq on Mon Jul 30th, 2007 at 08:47:59 PM MST
(User Info)

If you didn't catch the sarcasm please, try again. It is my opinion false advertising is detrimental to the entire industry. As Peter said:

"If one would take these corrections in account, they would achieve overunity.

They either deserve a Nobel prize for physics or prosecution for fraud/misleading advertising."

When, not if, folks buy these and tell others of their 'good fortune', of being fleeced, honest folks will have a problem. It will become impossible for companies who do produce 'honest' products will not be able to sell them.

If just 10% of the producers of products make bad products, that product type will become unable to finance, insure or sell the used machines. This means your used mill will be thought of as junk. Ordinances will be passed to, "Protect the public" and it will be illegal to erect such a device in (name location here).

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

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#19)
by electrondady1 on Tue Jul 31st, 2007 at 06:52:08 AM MST
(User Info)

the "betz limit"
"As formulated by German Physicist Albert Betz in 1919, 59% of the available energy in the wind can extracted. No wind turbine has come close to the Betz limit, most are in the 25- 30% efficiency range."

i think it's important to realize we are all at the begining of a new era .
one in which the production of energy by individuals will be common place
it's unfortunate that at this stage there is so much missinformation.
not much we can do about it except point it out when we see it.
cudos to ron
hollywood seems like they want to climb on board. maybe they can feel less guilt about there consumpion.
its ok ,it might speed up the transition.
one way or another the transition will take place.
as a species we have no choice

[ Parent ]

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#20)
by CmeBREW (smke833f@hotmail.com) on Tue Jul 31st, 2007 at 07:39:12 AM MST
(User Info)

Sorry, I did miss the Sarcasm. I'm not too bright. I know their figures are obviously way too high, but at least they gave the power charts unlike most. Anyone who gets one can call them a liar. Almost everyone exaggerates the numbers for marketing reasons. I hate that fact also. People need to be more educated with facts instead of bull. Those are mainly torque machines, so I also don't think they come close to BEtz. But even if they get half the power they profess, It would still be a pretty usable machine.

[ Parent ]

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#18)
by thefinis (thefinis@hotmail.com) on Tue Jul 31st, 2007 at 06:20:19 AM MST
(User Info)

It is a shame that so many of the wind turbine builders make such outrageous claims. It is this marketing area/claims that I think causes some of the real/workable turbine builders to decide to fudge on their figures too just because real figures don't look near as good up against the advertised claims from many of the sellers.

If it sounds too good to be true it usually is.

Finis
Texas born and bred

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#21)
by Tritium on Tue Jul 31st, 2007 at 07:43:14 AM MST
(User Info)

from this link description of their alternator:

http://remnet.com/WindEnergy/page5.html

They indicate 9 coils per phase, 3 groups of coils (three phase),delta connected.
36 positive negative pairs of magnets on 2 rotors. (is this 18 or 36 magnets per rotor)?

How do you obtain a three phase arrangement from these numbers of coils and magnets?

They also claim 12V charging at 2meters per second wind speed.

I just don't believe their claims are real world numbers.

Thurmond

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#22)
by finnsawyer on Tue Jul 31st, 2007 at 08:16:31 AM MST
(User Info)

27 coils 36 magnets satisfies the 3:4 ratio. It seems they have 36 magnets on each rotor with a north pole magnet on one rotor facing a south pole magnet on the other rotor.
GeoM
[ Parent ]

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#24)
by Tritium on Tue Jul 31st, 2007 at 09:08:17 AM MST
(User Info)

Well it would help if I could add or multiply this morning. 3 times 9 is 27 not 18 as I had it in my mind for some reason. Easy to see with the correct numbers. LOL.

Thurmond

[ Parent ]

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#25)
by DanB (danb@*no spam*otherpower.com) on Tue Jul 31st, 2007 at 09:09:18 AM MST
(User Info) http://www.otherpower.com/

Yes- it seems way over the top. The machine sweeps about 80 square feet - it seems similar in my mind to claiming that a 10' diameter HAWT is a 10KW machine @28 mph. All of their power graphs seem quite optimistic/impossible to me.

It doesn't speak well for the credibility of a company that otherwise seems to be doing somewhat neat stuff. Be nice if they could come out with a solid product and have it stand on it's own without such unrealistic hype. Stuff like that bugs me...

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#27)
by Tritium on Tue Jul 31st, 2007 at 10:48:49 AM MST
(User Info)

I just e-mailed PacWind and ask them If they would like to enter this discussion here.

Thurmond

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#28)
by vawtman (vawtman(at)charter(dot)net) on Tue Jul 31st, 2007 at 05:30:12 PM MST
(User Info)

Boy that would be cool if they would.Very few understand the potential of these unless built.

Thanks Thurmond

Mark

[ Parent ]

Re: NEW! And revolutionary VAWT . (3.00 / 0) (#34)
by electrondady1 on Thu Aug 2nd, 2007 at 11:50:41 AM MST
(User Info)

i do enjoy the intellectual fencing matches that occur here occasionally.
it's important though to remember scoring points is not why we are here.
far be it from me to defend fin's theories.
but i have also observed the phenomenon he mentioned in regards to wind, snow and tree trunks.
i have become a keen observer of snow drift patterns since i became infatuated with wind mills
i think there are lots of lessons and possible benefits from it.

[ Parent ]

NEW! And revolutionary VAWT . | 56 comments (56 topical, 0 editorial)

Menu

� create account
� How to use the board
� FAQs
� search the board
� Google search the board
� Old Otherpower Board

Login

Make a new account

Username:

Password:

Total Views

��206 Scoop users have viewed this posting.

Related Links

� http://pacwind.net/
� Also by wdyasq

You must be a registered user to post here. It's easy and free, and the link is on the upper right side of your page.
All trademarks and copyrights on this page are owned by their respective companies. Postings are owned by the poster, but may be deleted or moved at the ADMIN's sole discretion. The Rest � 2003 Forcefield.
You can Email the board ADMIN here. PLEASE include the username you signed up with!