Wind Turbine

The duct velocity sounds rather high (perhaps more kinetic energy than necessary, unless required by limited duct space). If you try to recover excess KE, this may affect the air flow so that it does not meet other objectives. Nor will you be able to recover as much energy as you could save by decreasing the duct velocity at the outset.

[I guess, but am not sure, because there aren't many details so far.]

GA! Link was a great "find," I especially enjoyed the low-key presentation.

Off to the web (not Google, of course) to find more like that. Thank you for the impetus.

Regards,
Gene

off spin or leg spin?...Not only the velocity but volume of air is matter.

I'm uncertain about this, at least in all circumstances. Admittedly, the following won't payback much, but it would seem to harvest otherwise wasted energy.

I used to work in coal mines (mostly what they called drift mines--underground but on a hill so you didn't have to dig down to get to the coal seam). There is a requirement for ventilation at the coal face (to dilute any methane found, to move coal dust away from the miners (i.e., workers), etc.) We typically used large (well, 8' diameter) axial fans with a large (300 HP) motor. (At the time I worked there, 35 years ago, we did not use variable speed drives.)

Typically (I never saw an exception) the fans are set up to exhaust air from the mine, thus pulling fresh air in at specific locations, then channeled to the mine face by various means.

The bottom line, where the fan is running and exhausting air, just on the outlet of the fan, a lot of high speed air is mixing with ambient air and dumping energy.

Couldn't a wind turbine in a location like that harvest some of that energy?

And further, I'm not sure it would take any more energy to run the fan even if you did try to use a variable speed drive and run the fan at "exactly" the speed needed to get the minimum air flow required. Still, on the exhaust side of that fan, energy is being wasted, and it seems it could be harnessed.

Anywhere energy is being wasted, there would seem to be some chance of capturing some of that wasted energy, without requiring more energy on the input side.

Why so bitter so early in CR4?

Please have an open mind, thank you.

If reducing the fan speed saved energy (will it?) the OP would have surely done that. So, he needs that speed and that cusec of flow.

If, as some others have also said, he could save some power somewhere else, he would have done it.Why do we assume that we are smarter than the OP? Just because he is asking for help?

Pity.

Quite right, my apologies.

I just finished a discouraging dialogue. My friends, bitter I'm not.

If he needs that flow and the speed then he will not want to slow it down again by means of introducing a engerg producing unit.

You and he will ber turning in circles if he has to speed up the fans to power his energy producing fan.

Do as advised and make the current system more effective and save teh energy there!

Cheers I.S.

If the OP has already reduced the fan speed to the minimum acceptable, then adding a wind turbine to the flow will reduce it below the minimum acceptable limit. One cannot get something for nothing (the Laws of Thermodynamics say so).

So the advocated solution would be unacceptable.

So the OP would be best advised to give up on this folly.

i am assuming that #35 and #42 are indeed meant as responses to my post #13. Which was only imploring PFR to be somewhat more open-minded.

i am an electrical engineer with a lifetime spent only in LV switchgear. Absolutely no knowledge of wind generators or turbines etc. So, i have been responding to what the OP wanted.

the problem for me is, "to design the blades" so that maximun air energy is utilized. I am not getting proper solution for it

Pardon me, friends, i seem to be the only one answering his/her query. The rest of you have (perhaps rightly, and perhaps with good reasons laid out) told him to stop his folly....i believe in not discouraging anyone. i believe that one has to find out the futility of one's idea oneself.....(when was the last time i took such advice from someone else? can't remember).....let him try, and if he fails, chalk it down to valuable experience.

You are indeed failing to recognize the issue. Helping someone to perfect a folly is not being open minded. It is a folly. You may be interested in truly playing in the sand with your new friend, but most of us see all the turds rolling around in it.

Wonderful ! i agree with you.

However, pardon me, i will go and build my windmill and when i fail, it will be my folly, thank you.

Have you never burnt your finger? If not, you are unique, you listened to everything someone told you, and grew up to be the perfect human being, congratulations.

Thank God that there were many geniuses who rose above us turds, so we are able to use our computers to insult each other.

The turd is the idea. Not you. I would like to have coffee with you.

That is what the forum is. A strainer. A sieve. A colander.

You beat me to it. i just opened the website to cancel my comment and apologise to you. Sorry anyway, i am not built that way. Excuse my state of inebriation (it is 10 pm in India). Thank you for your understanding, friend.

You are absolutely right about CR4. Many a time i have revised my opinion thanks to the learned crosstalk.

My son lives in Sterling, VA. If i ever get a chance to visit with him, i will have coffee with you at the nearest Starbucks. At your expense of course, no poor Indian can afford Starbucks

Pardon me, friends, i seem to be the only one answering his/her query.

You're right! This article discusses the issues, other than specific blade profile selection, but the one mentioned (4424) is OK. The characteristics of NACA sections are pretty easy to find, and the standard book on the topic is Abbott and Doenhoff, Theory of Wing Sections. It provides data on hundreds of sections.

The pat answer is not always the correct answer. In this case, the OP has not provided details of his installation, so we may be giving pat answers to a more complicated situation in which a pat answer does not fit. His fans could be single speed, and their locations (vs equipment location) could be such that there is excess airflow that is doing no useful work (as a by-product of it doing some useful work in another location). Extracting energy from such airflow may be more practical than the moving of equipment, ductwork, and baffles.

Some of the conclusions to which people have jumped could be incorrect, it seems. Fan consumed hp is related to the mass of air moved, so choking a fan reduces the hp and electrical consumption. The OP pretty clearly has excess airflow; otherwise this idea would not have occurred to him. Given that, then there would seem to be cases in which using a windmill as a baffle would be more efficient than using piece of sheet metal.

Certainly there are many worse things to do than making a windmill, the experience of which can be a net gain in itself... aside from any energy gains or losses.

Your inputs, and your tendency toward kindness and encouragement, are valuable.

PFR, you asked; 'Will it never end?'

An interesting question, for which (even aside from it being asked in the negative) a valid simple answer may be illusive.

If we were to consult Einstein, he might repeat something he once said,

''Only two things are infinite, the universe and human stupidity, and I am not certain about the former''

Which is a far better response than my first choice:

'Rhetorical questions; who needs them?' Ftmre Bbb

Alas, it will never end--it is a perpetual notion machine!

In spinning department usually exhaust fans or return air fans ( Axial Flow fans) are used as a part of humidification system. They extract huge amount of heat form the ring frames gear end. There are many other methods to use these energy effectively . Velocity appears on higher side i.e. app 3543 CU ft per min. Viability of this project need to be studied carefully theoretically before implementing it.

the idea behind wind turbine is to make the system energy efficient or can say, the air which ius being wasted should be utilized. These return air fans are part and parcel of the spinning industry. They are utilised for the collection of fluff (floating tiny particles of cotton), extraction of heat etc. We have to maintain this much pressure keeping in view the applications, then also some part of this air is recycled to maintain RH and humidity of the deptt and rest is useless.We cant deduct 3 KW from the system.

If any one has the better idea as mrswamy siad, "There are many other methods to use these energy effectively ". is warmly welcomed to share.

Further, i ll try to keep you guys updating with our praticals.

on monday, we will perform a little experinmet I.A.

Blade design is still a problem???

Comments are really valuable.

@kvsridhar! interesting link

Glad you liked it. No help from it on blade design ?

i guess you have studied airfoil design in depth, and this perhaps is too elementary.

Anyway, there are many experts in CR4 community who are well versed in this, i hope someone will see your post and help.

Good luck

Having worked in the Textile industry for 22 years I think I understand what you are trying to achieve. The exhaust air that is truly being exhausted out of the building could be utilized with out having a negative effect. Many are trying to see it in a restriction to flow but once you have gotten beyond the machine itself you are dealing with the positive and negative psi in the room. If you are dealing strictly with out side air I do not see why it wouldn't work. On the other hand when you return air into the room you may have an impact on conditions and such. Just an Opinion good luck.

I'm sorry, but that is not really true. You might be surprised at how far upstream the effects of the turbine will extend, even if allegedly in "free air." The energy to drive it comes from somewhere, namely the main fan. Thus it will degrade the airflow in one fashion or another. If the system is really on the dot already, this will not be acceptable. If there really is surplus energy, yes, it could be tapped, but more energy would be saved by slowing down the main fan.

An efficient airfoil would degrade the main airflow less than an inefficient airfoil would, however.

Google perpetual motion machine. In short you mention "waste energy". I suspect there actually isn't any.

Just a minute, please.

I understood OP as saying that the air movement was a necessary part of his process, and that he hoped to recover some of it at the "waste" end.

Perhaps I was wrong in reading that into the post; but if I'm right...

Where do we draw the line - as design professionals, as engineers, that separates what is to be inherently wasted from what can be ingeniously recovered? Are we so callous as to believe that our failure to recognize an opportunity for our culture is justified by our need to preach the "company line" - the company being IDTOTF,inc (I Didn't Think Of That First, with an "inc" on the end).

I could be wrong, have been before and as long as I breathe probably will be again but I MUST IMPLORE ALL "PROFESSIONALS" WHO POST HERE to remember that we have an OBLIGATION to keep our "advice" professional and our judgements to ourselves.

OP - please provide a flow diagram of your CURRENT air system. Otherwise, we are all either passing judgement or judging in passing - neither of which are productive nor reflect positively on our calling.

Thank you.

Regards,

Gene

Do you shout loudly when you vote for MLAs and MPs??....

WTF,O?

Perhaps the loudest shout is "NO - I REFUSE TO ALLOW MORE UNPROFESSIONALISM TO TRASH WHAT IS MY FORUM, TOO!"

Notice, I posted this under my own avatar, not as a "Guest." Sadly, I expect you will continue to hide behind your guest status and I suspect you will therefore STILL not contribute to the advancement of knowledge-sharing by doing so.

BTW, what's an MLA and an MP? Answer me, if you have the courage, and I, too, might learn.

Sorry, OP, but this has little DIRECTLY to do with your post so I'll give myself 5-OT's and pray for your continued interest in receiving professional and responsible input to your post.

As I see it, your system will be about as efficient as that of a dog chasing his tail. It wil cost you more than you will produce. Trust me, I also tried to build a perpetual motion machine.

Ahh, i read JRaef's post more carefully now. Teaches me to be more careful in future.

Without an airflow diagram, how could ANYONE, INCLUDING ME, provide OP with a recommendation?

Is it open loop, closed loop, where are the barometric reliefs (if any), where do the "fines" go, HOW, sir, can you or I or anyone help this OP by NOT DEMANDING that we must be allowed to participate fully before judging so completely?

Your OT is noted and discarded; to the OP: some here are trying to help; please help us help you. Thank you.

It might help if you responded cogently to the engineering and thermodynamic considerations that have been raised so far. JRaef might be mistaken, and I more likely to be so. But you haven't said a word about how or why. The presence or absence of a "recovery fan" won't alter anything about any fines, so that is irrelevant to the energy aspects of all this.

Further, I didn't "judge completely"; I mentioned the possibility that there really could be excess airflow and power in this system that might be hard to change, and thus allow a "recovery fan" without screwing things up.

I agree that the OP's information could be better.

If you are mounting the turbine in any duct, then the restriction will increase the fan load by X and the energy out of the turbine will be .5X at very best. The turbine would cause a net loss.

If the fans exhaust to outside the building and you position the turbine well away from the outlet, so that there is no change in the pressure and velocity measured at the fan, then perhaps you could extract energy from a flow that otherwise is only being used to move outside air.

Perhaps you could supply a drawing showing how you will install this turbine.

All good comments so far, and as the subject of this post illustrates, persistent education is necessary. If the exhaust flow impacts the mill blades in any way, and that force is harnessed, you have created an equation with an = in the air stream between the exhaust outlet and the mill airfoil. This would of course include energy in all forms, and there may be heat that could be extracted. That would not involve a wind mill, and the OP did not mention harvesting heat.

This is yet another case in which the OP does not provide a diagram or sufficient details, but perhaps he will.

Here is an interesting possibility to consider: You can restrict the inlet hose to a vacuum cleaner, and the motor will speed up as a result. The motor will draw less amperage and wattage. This seems odd at first, if you haven't thought about it -- but everyone has heard the motor speed up when a sock gets sucked up.

If the restriction is partial, the same applies. Less air is moved by the vacuum cleaner, and less energy is used as a result. If the thing causing the restriction is a windmill (miniaturized in this case), then the windmill has a positive output, and the motor draw simultaneously goes down.

This could be fun to sell (via a YouTube video) as clear proof of "energy from the vacuum", "zero point energy," etc. A small windmill could be constructed that would light a lamp, for example: Light output in addition to reduced electrical draw by the vacuum cleaner. Could be a good demo for a high school physics class.

Are you serious? That was not rhetorical.

The first three paragraphs are serious.

The last sentence of the last paragraph is serious: You plug the vacuum cleaner into a wattmeter. You place a dc permanent magnet fan in a funnel-shaped duct connected to the vacuum cleaner inlet. A flashlight bulb connected to the fan motor (which works equally well as a generator) lights up. The reading on the wattmeter shows that the vacuum cleaner is doing less work. But the bulb illuminates.

It appears that the vacuum cleaner is doing additional work to turn the generator to light the light. But the wattmeter tells you that it is doing less work.

It may be tempting to think that because the vacuum cleaner is "sucking harder" it is therefore doing more work. That's not true, but a correct understanding can seem counterintuitive. I took the You-Tube "sales pitch" idea as satirical, although maybe it could scam some gullible investors.

I took the You-Tube "sales pitch" idea as satirical,

Correct.

Derivate the air resistance and motor output to zero. Hit

Check Design of Nikola Tesla wind Turbine

I already did. It ain't that great. Lots of people have a Tesla fetish. He was a genius in some respects, and a nutcase in others. Some of his high-voltage stuff was flashy, which continue to wow naifs. Industry probably owes more to Charles Steinmetz than to Nikola Tesla; both made important contributions.