Vertical Wind Tunnels using green technology

[boneh3ad]

I'd be interested in the area required of the collector in order to produce enough air movement to levitate a person. It is estimated that a solar updraft tower require a similar capital investment in terms of dollars per watt to a nuclear plant, so it seems like a rather expensive option.

 

[Baluncore]

I'd be interested in the area required of the collector in order to produce enough air movement to levitate a person.

The updraft tower only needs to be big enough to generate sufficient air velocity for some of the time. At noon in the tropics it will need a larger area skirt. In temperate latitudes it will need a larger chimney.

Have you ever heard the call “surf's up”? Taking advantage of natural phenomena is one way we stay in contact with nature. Surfing, skiing, sailing, or paddling small boats down rapid rivers are all ways of being part of the Earth. Sky diving and base jumping are more intense and certainly not for everyone. We value more what we must gather or harvest than what comes out of a tap or a wall socket.

It is estimated that a solar updraft tower require a similar capital investment in terms of dollars per watt to a nuclear plant, so it seems like a rather expensive option.

That assumes a big stand-alone plant capable of competing with wholesale power prices. For a much smaller unit, it only needs to compete with the retail pricing. Building an updraft tower may be combined with other construction. The possibilities are endless from fun parks to the ridiculous. Imagine free-falling up to the penthouse of your office building.

There can be no new patent protection for anything after it is discussed on this forum, the ideas are available as prior art to anyone with a search engine. There can be no million dollar win, nor any legal costs writing or defending patents. Just competition in the marketplace for an environmentally efficient ride.

 

[boneh3ad]

The updraft tower only needs to be big enough to generate sufficient air velocity for some of the time.

I suppose I don't agree with this right here. The amount of air movement generated is going to vary throughout the day, and it is likely that a substantial part of the business for such a facility would come in the evening after people leave work as something to do with friends. This happens to correspond to the time in which there is little or no sunlight. It seems to me that this is one of the flaws of using a solar updraft tower to provide the flow directly for this application along with the large footprint that would be required relative to a more conventional facility.

Also, how would you turn it off when you needed to let people walk into the chamber? And how would you cope with days where it is overcast and the supplied air is not nearly as fast?

I am not trying to claim these problems are intractable, by the way. I simply don't immediately see their solutions. The "conventional" solution is to store some of that energy (if anyone ever developed the required battery technology) and use it later when the sun is not out, but this wouldn't work if the tower is the wind tunnel. You might then argue that you could just use the power generated from the tower to power a more conventional configuration, but then it would be more efficient to just use photovoltaics anyway, I believe.

That assumes a big stand-alone plant capable of competing with wholesale power prices. For a much smaller unit, it only needs to compete with the retail pricing.

That's fair, though I think you are underestimating the size of structure that would be required to move air fast enough to simulate a sky dive. Further, any constriction in the tower in order to try to increase the speed will impose a pressure gradient on the flow, which would increase further the surface area required of the collector. It would be an interesting problem to work out how this compares to simply increasing the collector area instead of adding a restriction.

 

[PD Chant]

I must say, I like this forum.
May I comment further: I am aware of the firm in Deutschland offering turn key operations and their pricing structure. I am aware of the breed facility in Bahrain.
I also have no illusions - or should that be delusions! - concerning costs. I am familiar with King of Prussia in Pennsylvania. My bet is they are purely after money and have no great advances in technology to move they're project along.
No one, I assume, is aware if my financial situation. But from some of the posts I see many do not understand that when there is a will there is a way.
I am in London.
I'm not interested first and foremost in the money, that comes as a byproduct of good work.
I am the son of a brilliant engineer but myself I trained in general science, medicine and law.
I am a dreamer and a doer. And yes, I want to change the world for the better. Indoor skydiving leaves the participants well pleased with the experience. But to have that experience in a system that requires immense power conventionally just doesn't do it for me. To flip the coin on its head, so to speak, and create such a facility in an unconventional way such that the power required is uniquely unconventional, well that does do it for me.
I'm not worried about the money. At this point I'm partially funded, and if I can nail it down correctly I will not have much difficulty in paying the necessary money to get it up and operational.
I must thank each and every one of those who participated in the discussion. You have all improved my day and I am grateful.

 

[Steelwolf]

For a power plant I would go with an alcohol powered turbo prop or turbo fan and have that ducted to the bottom of tower and then the use of venturis would give additional air volumes of up to 600 to 700% of the ducted air from the turbofan/prop. While it is not a way to recapture the energy, it IS a way to make the energy put into it actually do more work. Of course it is not going to be cheap, but the power output and mantainance is MUCH lower and many fewer moving parts than an Internal Combustion Engine.

You can recapture Some of the energy by tapping the flow After the freefallers have played in the airstream, but to what degree you would be able to reconvert, I am not at all certain. Certainly using a tall tube for the, supposedly, 'green sun-lift' effect would be a tourist attraction, but the basic setup, done with turbine, can be moved and re-set up in various places. Permissions, licensing and insurance may be a pain, but this is a doable thing.

 

[russ_watters]

Near me in King of Prussia is a facility under construction that you can see from the highway that I assumed at first was a Lockheed Martin wind tunnel. Turns out it is an iFly indoor skydiving venue on an adjoining property (which probably explains why I wasn't arrested for taking pictures of it). It's an impressive facility that I would bet cost $5+ million. The duct appears to be two rectangles back to back, vertically, on one central shaft, with the fans on top. I'll post some pics when I get home.

Some photos of the installation:

Those are a couple of months old. It is enclosed now.

Website:
https://www.iflyworld.com/what-is-indoor-skydiving/

This says the one in Seattle is 14 feet (4.3m) in diameter and has a total of 1600 fan horsepower (continuous).
http://en-us.fluke.com/community/fl...nt-testing-keeps-indoor-skydivers-flying.html

 

[PD Chant]

Thank you for the links, I hadn't seen the second one. King of Prussia: ugly as sin right now.
Back to power solutions: I'm in London but I did not mention my sites. The Solar Updraft Tower is more appropriate for my location that is in better weather than here. And this location has more space for such a facility than Lonfon.
I agree with turbine engines for Lonfon.
I've been thinking that if you have a completely closed air flow loop, then once the flow is up to speed, the only energy lost would be due to friction and heating which would occur. I'm not good at the calculations required. Essentially, It would be like a flywheel, taking a while to get up to speed but needing far less power to keep it going.
.

 

[Steelwolf]

You would need to make sure that it stayed up to proper Oxygen levels and low/no pesky stuff like the CO or CO2, but that is a minor detail of sensors and appropriate air-replacement ducting that should be able to work without reducing the speed of the major air mass, in fact, at certain points along the recycle-route, centripetal course can be used to separate out some of the heavier gasses by exhaust ducting in just the right places. But yes, once you have the entire air mass moving, you can treat and build it mostly as a torus so as to limit the number of curves needed and the sharpness of it so the vampiric effects of friction with the walls can be minimilized, especially with the right materials. I am sure that there would have to be the various safety concerns met, but after the rest of the engineering that is a simple exercise

 

[Steelwolf]

OH, here is something I had not thought of. The Turbine Engine uses a reduction gear so you can run the air for the Shaft separate from the air-fuel flow for the running turbine, so that the 'Flyers' don't get Any of the jet exhaust. What I had been thinking before they would have had a nuisance level, but highly diluted. But, done this way, I am wondering what kind of Magneto-hydro dynamic ionic exchanger you could set up with the exhaust flow and derive electricity from that, separate from the flow and not impeding the flow like it would to run new fans or compressors, this just uses the inherent fact that jet exhaust is a 'low plasma' and that it is fairly highly charged, one can harvest electricity straight from it. It is a little bit hard on the anodes and cathodes used, but I am thinking that graphite/ceramic metals plates in a ring about the jet stream in paired sets should be able to pull a fair amount of energy from the setup while ye have your fun unimpeded at the same time!

 

[CWatters]

Just for info... I saw a TV program recently about a cruise ship that had a skydiving tunnel on board.

 

[Windadct]

OK - I tried to skim through this thread as best I could:

1) Have you been in an iFly ? - The air speed is managed dynamically, so while the design spec may be ~1000HP - they throttle the airflow ( Manually) - So throttling 1000HP is not a trivial task and IMO the only real way is with electric motor driven fans.

2) Internal Combustion engine? - The OP stated green technology - there is nothing green about an ICE.

The Greenest way ? -- Average Load scaled energy source ( Solar, high efficient micro gas turbine) - and then local energy storage. Keep in mind the users are in the chamber for 3 to 10 minutes - maybe more. But the unit is not running at full power 100% of the time. I would hazard to say you need about 50% of peak power as an energy source - so similar to a hybrid car.

You say you want to make one bigger (6M diameter) - again - in an iFLY the navy trains 4 people at a time in the 3M tube. ( I could not find the Navy team in a video - but here are 4 people - VIDEO - sorry for the ad ).

I did this in Orlando and the Navy team was ahead of us - it was intimidating to watch as you signed 5 paged of wavers stating you do not have a shoulder injury - kind of expensive - but well worth it for a one time thing ( you will want at least 4-5 flights to get the hang of it).

 

[OrangeDog]

As someone who designed a small wind tunnel, I can tell you there is absolutely nothing new and exciting in wind tunnel design that would help you in your quest to utilize "green energy". The wind tunnel is 110-120 year old technology that was extensively researched before CFD was developed enough to replace experimental work.

Hell, if you give me a few hundred dollars Ill give you my design and all my reference.

 

[boneh3ad]

...before CFD was developed enough to replace experimental work.

When is that going to happen?

 

[OrangeDog]

When is that going to happen?

CFD has replaced experimental work in almost all cases except for the prototyping phase of the design process.

 

[boneh3ad]

CFD has replaced experimental work in almost all cases except for the prototyping phase of the design process.

As a guy who runs a wind tunnel for a living, I tend to disagree that CFD has replaced wind tunnels, particularly on the research end of things.

 

[OrangeDog]

As a guy who runs a wind tunnel for a living, I tend to disagree that CFD has replaced wind tunnels, particularly on the research end of things.

That makes sense because you are in research. As someone who is in industry, it costs an obscene amount of money to run a tunnel vs run CFD. We have an entire group dedicated to CFD at my company (I am in their sister group, the hand calculation + design integration guys), we do experimental work only after we have numerically went through our best design solutions. Experimental stuff is great when you are pushing the boundaries on the problems you are solving (eg, things that have never been done before), and as someone who has a background in experimental aerodynamics I think it is much more fun than CFD, but being honest with myself CFD is pretty good for most conventional problems.

 

[boneh3ad]

Yes, there is a lot of design that has been shifted to CFD rather than wind tunnels, but companies like Boeing, Lockheed, and Northrop still maintain a fairly large number of wind tunnels for a reason. We still do a really lousy job of predicting drag or heat transfer on a given shape, for example, so experiments are still important in the realm of T&E, not just research. That's the same reason the Air Force maintains so many facilities, e.g. AEDC.

 

[OrangeDog]

Are they hiring :)

 

[boneh3ad]

I know that AFRL is working on a new facility at AEDC for super- and hypersonic wind tunnels that is in expansion mode, but I don't know if they are currently hiring or if that is farther down the road. It also requires moving essentially to rural Tennessee, which is not a positive aspect of that facility. Lot's of cool plans, though.

 

[OrangeDog]

It always seems like the coolest things are in the dumpiest area of the country. I just got an offer for a PhD, but I am hesitant to take it because it is in crappy northern New York. I went to undergrad near the area..no thank you...dark and cold most of the year.

Anyway, back on topic: OP, give me your money and ill give you my data.

 

[Windadct]

BTW - found this "green" vertical lift..

 

[PD Chant]

Nice video, thanks! Don't mess with Mother Nature...
Sir Orangedog, what excites one may indeed bore another. I would note, however, that nothing in any field had been stagnant for a century, and I'm sure you are well aware of this.
And just what would my money get me? Certainly not century-old tech for VWTs.
I personally am intrigued and excited by this project. As you are all well aware, such an endeavour would "normally" eat energy and therefore money. When I have succeeded in my projects - I'm doing two VWTs in different countries, I will have advanced the techniques used currently come hell or high water.
Most businesses are quite willing to NOT push the envelope, so to speak, if they can see a decent profit using a tried and true methodology. I have no interest in this, that is what bores me!
I have only an interest in what excites me, and however well researched VWTs are over the years, I will innovate the process and set a new standard which we can discuss once completed.
The ongoing discussion in this forum I find quite stimulating and I therefore wish to convey my thanks and gratitude to everyone who has taken the time to participate. With friendly greetings from London to one and all...,
PD Chant

 

[boneh3ad]

One thing that concerns me is that I feel like you are greatly overestimating the market for vertical wind tunnels. I feel like the development cost here is going to be quite large, and then when all is said and done, you will likely have a hard time getting anyone to buy it to offset that cost.

 

[boneh3ad]

EDIT: This was responding to a post that was later deleted. I've edited it to reflect that.

My entire point is that using the solar updraft approach - which is where much of this discussion has focused - has several challenges. The first of these is due to the variable power reaching the surface from solar radiation throughout the course of the day. You will need to find way to mitigate this effect (which are, incidentally, the same issues facing many renewable energy technologies). That is not a cheap thing to do, and generally people cite improved battery technology as the solution to this dilemma. That isn't really available yet on a large scale, and what is available is extraordinarily expensive. If you want to avoid using fans, I suppose those batteries will need to power something like heaters under the collectors to make up for the lower heat from the sun at various times during the day. If you have several consecutive cloudy days (as is certainly common in London), then I suppose you could just run those heaters off of power from the normal electric grid. That wouldn't be terribly efficient.

The second issue is the massive structure that would be required. Solar updraft towers are generally huge, and to create a high velocity, you will need a very large collector. That translates to a very large cost both in construction and in land acquisition, and you certainly aren't going to fit it in a major city when the collector likely takes up multiple city blocks. This means your potential market has now shrunk to include only businesses who are willing to be located in suburbs or further out. This also doesn't account for building codes, as many cities and towns likely don't want a giant tower with a huge collector surrounding it to be nearby. It is an eyesore.

Finally, you haven't really stated why you think current technology is insufficient. Believe it or not, the photo posted above of the tunnel under construction in King of Prussia looks very efficient to me. Wind tunnels very frequently include 90-degree turns like that (look up closed-circuit wind tunnels), and that can be accomplished very efficiently using turning vanes. The fans are always placed downstream of the test section (or in this case the place where people will be) because the flow you get by "sucking" air through the test section is much more smooth than what you get by blowing it through. If you placed the fans below and blew air up, you would end up with a large amount of vorticity and turbulence and you would throw the "skydivers" all over the place in the tunnel.

So, why do you think the current state of the art needs to be replaced? You may have some altruistic motivation to try and make something new and more efficient, but businesses don't think that way. They are going to see a phenomenal up-front cost with effectively zero difference from the customers' perspective (i.e. they can't charge more than a conventional tunnel), and they will just pass and build a conventional tunnel instead. Why do you think this will not be the case? Do you have any other ideas that overcome the above challenges?

 

[russ_watters]

Locked pending moderation.

 

[berkeman]

Thread will remain closed for now. @PD Chant you can PM me to make a case for re-opening the thread. Keep in mind that the PF is a mainstream scientific website, and we do not allow challenges to good engineering work. Engineering is about optimizations.