Vertical Wind Tunnels using green technology

[PD Chant]

I wish to create a state-of-the-art vertical wind tunnel for indoor skydiving. By state-of-the-art I mean using green technology to create the power necessary to push air, and I would like to reclaim as much energy I can from the movement of air, drive shafts, and anything else I have not thought of but you may have knowledge of. Most tunnels require about 1000 hp to move enough air in a 3 metre wide tunnel. I want a 6 metre wide tunnel and that would require much more energy, and if I can exhibit how this can be done using minimal energy production through innovation and ingenuity then it would be a good example for others, and will of course reduce operating costs. Thank you.

 

[berkeman]

I wish to create a state-of-the-art vertical wind tunnel for indoor skydiving. By state-of-the-art I mean using green technology to create the power necessary to push air, and I would like to reclaim as much energy I can from the movement of air, drive shafts, and anything else I have not thought of but you may have knowledge of. Most tunnels require about 1000 hp to move enough air in a 3 metre wide tunnel. I want a 6 metre wide tunnel and that would require much more energy, and if I can exhibit how this can be done using minimal energy production through innovation and ingenuity then it would be a good example for others, and will of course reduce operating costs. Thank you.

Welcome to the PF.

Please tell us your thoughts on how you will accomplish this. Please include calculations for where you will be able to conserve energy.

 

[PD Chant]

Thank you for taking the time to inquire about my post. I could detail my thoughts, certainly, but at this point I am not clear as to my direction but for the true starting point of such a project: energy, and how to make best use of the newest technology of which I don't think I am fully up to date on. I plan to read the suggested threads below before so as to potentially update my knowledge on the subject.
I do know the conventional wisdom would state there's no free lunch concerning created energy and thereafter attempting to increase it. I'm thinking outside the box and though my lunch will not be free it will be substantially discounted.
More information as I learn from the contributions made to this site. Have a nice day!

 

[Baluncore]

Consider a solar updraft tower as part of the solution. https://en.wikipedia.org/wiki/Solar_updraft_tower

Build your free-fall chamber near the base of the tower where you can gently pinch the section to increase the air velocity. It will only operate when the sun is out, but it might be used to generate an energy credit when not being used for free-fall.

A wider skirt or taller chimney will gather more solar power. Area and height limitations will dictate the percentage of the required power may be generated by the tower. Even if additional power is required for a fan, the use of any updraft tower should improve the environmental bottom line.

 

[russ_watters]

No offense, but an idea like that would be worth millions of dollars; Don't you think people who do know the physics/engineering have been working on such things, given that there would be a lot of money in it? And you want us to invent it for you here? Do you really think that is realistic?

 

[boneh3ad]

I honesty don't think it would be worth millions. Vertical wind tunnels for this purpose are a very niche market. In trying to transfer the hypothetical concepts to a more conventional configuration, the high additional cost of such a system would price most users that could benefit out of the market (i.e. universities) and wouldn't be worth the additional cost to most of the rest (i.e. government) who can afford the power draw of a more conventional design.

Still, even if it was a lucrative idea, I totally agree it would be silly to expect a bunch of us to basically invent it for someone else for them to benefit.

 

[Baluncore]

Still, even if it was a lucrative idea, I totally agree it would be silly to expect a bunch of us to basically invent it for someone else for them to benefit.

I'm happy to throw in ideas because the OP will have to do all the work of selecting and integrating the collection of suggestions received. The idea is only 2% of the invention. Making the prototype is another 2%. I hope our suggestions make possible a successful business that employs many and earns it's investors a good financial return.

I am often presented with challenging problems. I solve them using ideas I get from all over the place, including from OP's questions and member's replies here on PF. This is a two way exchange of ideas. It is a community.

 

[boneh3ad]

I'm happy to throw in ideas because the OP will have to do all the work of selecting and integrating the collection of suggestions received. The idea is only 2% of the invention. Making the prototype is another 2%. I hope our suggestions make possible a successful business that employs many and earns it's investors a good financial return.

I am often presented with challenging problems. I solve them using ideas I get from all over the place, including from OP's questions and member's replies here on PF. This is a two way exchange of ideas. It is a community.

I get it, and usually I'd agree. I happily throw out idea when it's an idea that is already well-thought-out and they are generally looking for help with a piece of it. This, though, feels like someone fishing for the answer to the entire project. Maybe I'm wrong, but that's just how it read to me.

 

[PD Chant]

Ah, how interesting. The two gentlemen agree that knowledge should not be freely disseminated... a side note, would there ever be a situation where you would think knowledge should not have a pricetag?
Now, on the topic before us, please, this is not quite rocket science. Vertical wind tunnels (VWT) are straightforward. Calculations indicate 925 bhp would generate enough air velocity for a 3 metre diameter flying chamber. One can, roughly speaking, take four V8 enginesrive sha that can develop 250 bhp, add a fan or propellor blade to each, run them at the correct and constant rpms necessary to combine their airflow through a vertical tunnel to achieve the desired velocity. Attach a generator to each drive shaft and reclaim some juice. Have your engines run biodiesels. Now that's about it for the conventional thinkers. No big deal. I have a few other ideas for green energy feeding machinery to move blades that push air. And the gentleman's comment about varying the diameter of the tube I understand and appreciate.
The intellectual challenge is straightforward. Air is flowing in a closed loop system. The movement of air requires a push by power. The very fact that circulating air through the chamber is at a high velocity means at any point in the circulation chamber one may remove energy from the wind. But the 'no free lunch' principle means that what was removed is replaced by the powered machinery - call it an engine. But can one outthink conventional wisdom and have a system in which the use of the engine that results in moving air is arranged and augmented so lunch, if not free, is severely discounted -- and without using fossil fuels.
One may decide on optimal engines and optimal blades to create the desired velocity. But a solution that harnesses the wind's power without the need to recreate that original wind velocity through the use of the engine is something that you cannot come up with whether you get money or not - it would violate a principle of physics. But there must be a way through technology and efficiency, through the manipulation of the tunnel diameter as suggested) and the use of outside green energy sources to augment the principle energy production that the end result would be an example of what can be done -- when there's a will there's a

 

[Baluncore]

Attach a generator to each drive shaft and reclaim some juice.

No. That would be very inefficient. It smells of an attempt at perpetual motion.

 

[PD Chant]

How did you arrive at that conclusion of inefficiency?With a stationary conventional internal combustion engine, the driveshaft would spin to revolve the blades for air velocity, a belt attached -- in a similar fashion as one's automobile's fan belt -- and that belt turning a generator... It would seem a waste NOT to do that, sir.

 

[russ_watters]

Ah, how interesting. The two gentlemen agree that knowledge should not be freely disseminated...

That bears no relationship to what we said. It isn't just knowledge you are asking for, it is an invention. Inventions have value. You want to make money off of something we invent for you! Will you send us a check for a fair piece of our contribution? We'll happily provide knowledge for free, though:

Calculations indicate 925 bhp would generate enough air velocity for a 3 metre diameter flying chamber. One can, roughly speaking, take four V8 enginesrive sha that can develop 250 bhp, add a fan or propellor blade to each, run them at the correct and constant rpms necessary to combine their airflow through a vertical tunnel to achieve the desired velocity. Attach a generator to each drive shaft and reclaim some juice.

That would violate conservation of energy if it provided a benefit. Every HP of generator added would necessitate adding a HP to the engines to maintain the energy balance.

 

[Baluncore]

It would seem a waste NOT to do that, sir.

Then you do not understand efficiency. Each time energy is converted there is loss.
The motors are run to turn the blades. Why take some of that energy away from where it is needed ?

 

[russ_watters]

I honesty don't think it would be worth millions.

The OP is trying to save 200 hp. At 1200 hours per year and 12cents per kWh, that's $215,000/year per installation.

[Late edit]
Beyond that, depending on the specifics, it could have implications in other industries, such as mine; HVAC. Saving fan poser is a significant fraction of what I do for a living. That also means that a lot of people have put a lot of thought into this already, so easy answers will be tough to come by.

 

[PD Chant]

I believe the forum is a platform for the exchange of ideas and knowledge. I do not ask anyone to make calculations, or make any inventions. I merely ask for the dissemination of wisdom and perhaps all parties learn something of interest.
As for efficiency, I agree in a system solely designed for moving air generating electricity off a drive shaft will entail energy. But perhaps I was not clear as there would be the entire facility containing the tunnel that would require power.
Please make no calculations that may or may not prove that energy would be better used off a commercial grid!
The ideas and rapport, sir, and/or sirs, is greatly appreciated, thank you kindly.

 

[Nidum]

First generation vertical wind tunnels just used aircraft propellers . More recent ones have shown some advances in fan technology but not really very much . Use of gas turbine ducted fan technology could possibly give significant improvements in running efficiency but it would come at very high cost .

 

[PD Chant]

Actually, regarding saving HP, which you've equated into money, my actual intent is to NOT use fossil fuels and showcase alternative solutions. My rough calculations show with conventional internal combustion engines, the size of the tunnel I envision may require up to 2000 HP to move the air at the velocity I desire. If I had diesel engines, and used bio-diesel, it would cost a bit more than the current price at the local station.
Of course any business must concern themselves with the bottom line, but this project is about alternatives, the future, and how best to go about thinking 'outside the box' to achieve such a goal.

 

[Nidum]

More like 4000 HP .

It doesn't matter how the air moving system is driven - you still need a high power air moving system and nothing will change that fact .

All that input power has to come from somewhere .

 

[PD Chant]

I'll have to look into gas turbine fan technology. I have been considering aircraft engines. I recall KLM flew using alcohol for fuel, but my research is incomplete in this area. RollsRoyce has some interesting engines developed but I haven't all the details to accurately describe herein what they've managed to do.

 

[russ_watters]

Then you do not understand efficiency. Each time energy is converted there is loss.
The motors are run to turn the blades. Why take some of that energy away from where it is needed ?

It is more than just an efficiency issue, it is the useful energy itself that is the problem. I'm not sure the OP got that from my previous post, so I'll try again, with an example:

If you are spinning a fan that requires 1000hp, you use a 1000hp motor or engine. Then you decide you want to "recover" 500hp of that, so you attach a 500hp generator to the system. But oops, now you need an input of 1500hp instead of 1000 and you therefore haven't gained anything.

 

[PD Chant]

The way I understood the hypothetical scenario was an internal combustion engine with a pulley and belt hookup on the drive shaft to turn a generator would produce electrical energy that could feed the infrastructure of the facility, such as lighting, and although that would could be measured in HP, the decider would be once converted to kWh and see if it may be ginancially worthwhile

 

[boneh3ad]

Yes but do you have any reason to believe that this would provide an advantage? When you hook up a generator to your shaft, if the shaft is losing 500 hp to the generator, then the generator is still only able to use maybe 300 hp of that. There's an efficiency issue in that transfer just like there is when you pour more chemical energy in the form of diesel fuel into the first engine and get less hp out of it than what you pour in. So, the more links you add in this chain, the greater the number of places where you are losing energy due to the second law of thermodynamics.

I honestly can't see how hooking a generator up to the shaft to power lights and computers and such would be more efficient than just running them off of normal building power or just slapping some solar panels on the roof and using those to power the lights.

Most wind tunnels are currently run with electric motors that run off of the building's existing power architecture anyway. In essence, then, you are trying to build a system here that can provide power to your wind tunnel in a manner that is more efficient (or at least less carbon-intensive) than just using the electricity produced at a power plant somewhere. As of right now, you aren't likely to realize savings in money or carbon by using an on-site diesel generator rather than mains electricity. If your goal is to simply find a greener replacement for running the whole facility off of mains electricity, you are probably better off just installing solar/wind in your building to provide as much power as is feasible, or exploring something like a solid-oxide fuel cell such as the Bloom Energy Servers that Google uses to power some of its data centers. Those are only cost effective in some parts of the country, though.

 

[Mech_Engineer]

I wish to create a state-of-the-art vertical wind tunnel for indoor skydiving. By state-of-the-art I mean using green technology to create the power necessary to push air, and I would like to reclaim as much energy I can from the movement of air...

The way you "reclaim" this energy will be to have a closed-loop recirculating wind tunnel system, this would be a seriously big construction project considering you want to build one with a 6m diameter (this would officially be the biggest in the world, the largest right now is 5.2m). You should take a look at existing companies that make these kind of facilities, take for example http://aerodium.technology/en/models/models/recirculation/ which markets a http://aerodium.technology/en/models/models/recirculation/. They say their recirculating tunnels start at 1.5 million euro, probably for the 3m model; I have to think the 5m unit is at least 3-4 times as much...

It would take a team of engineers with specialized knowledge in aerodynamics to design a wind tunnel like you're proposing (not to mention quite a pile of money).

 

[Mech_Engineer]

Take a look at the below source also, they estimate the construction of a 12-16 ft (3.6 - 4.8 m) recirculating wind tunnel facility will run between $7 million - $10 million USD. If you're wanting to build the biggest in the world, figure even more than that.

http://www.indoorskydivingsource.com/articles/build-an-indoor-skydiving-facility/

Costs, Construction & Ownership
For a portable machine, expect to invest at least $500,000 USD for the tunnel equipment itself. You might be able to find used portable machines for less, but be very careful when purchasing used. On top of these base costs you will need to factor shipping, construction, land and operation costs into your business plan.

Recirculating tunnels are much more complicated and most companies offer a range of services all the way from equipment only to turn-key operations. To open a project to the public, most modern recirculating tunnel projects (12 - 16 ft diameter, permanent installations) require an investment of $7-10 million dollars. The cost of the machine is included in this number. For reference on the lowest end you can find some manufacturers offering recirculating tunnel components only starting at $1,700,000 USD.

 

[russ_watters]

The way I understood the hypothetical scenario was an internal combustion engine with a pulley and belt hookup on the drive shaft to turn a generator would produce electrical energy that could feed the infrastructure of the facility, such as lighting, and although that would could be measured in HP, the decider would be once converted to kWh and see if it may be ginancially worthwhile

1 hp is 0.746kW (at 100% efficiency).

 

[russ_watters]

Yes but do you have any reason to believe that this would provide an advantage? When you hook up a generator to your shaft, if the shaft is losing 500 hp to the generator, then the generator is still only able to use maybe 300 hp of that. There's an efficiency issue in that transfer just like there is when you pour more chemical energy in the form of diesel fuel into the first engine and get less hp out of it than what you pour in. So, the more links you add in this chain, the greater the number of places where you are losing energy due to the second law of thermodynamics.

I honestly can't see how hooking a generator up to the shaft to power lights and computers and such would be more efficient than just running them off of normal building power or just slapping some solar panels on the roof and using those to power the lights.

Most wind tunnels are currently run with electric motors that run off of the building's existing power architecture anyway. In essence, then, you are trying to build a system here that can provide power to your wind tunnel in a manner that is more efficient (or at least less carbon-intensive) than just using the electricity produced at a power plant somewhere. As of right now, you aren't likely to realize savings in money or carbon by using an on-site diesel generator rather than mains electricity. If your goal is to simply find a greener replacement for running the whole facility off of mains electricity, you are probably better off just installing solar/wind in your building to provide as much power as is feasible, or exploring something like a solid-oxide fuel cell such as the Bloom Energy Servers that Google uses to power some of its data centers. Those are only cost effective in some parts of the country, though.

I was going to like this post until you said "Bloom Energy".

 

[boneh3ad]

I was going to like this post until you said "Bloom Energy".

Ha, I have no skin in that game. Just throwing out an example of a way to potentially avoid mains electricity. Out of curiosity, what's your beef? Perhaps that deserves its own thread or a PM.

 

[russ_watters]

The way you "reclaim" this energy will be to have a closed-loop recirculating wind tunnel system, this would be a seriously big construction project considering you want to build one with a 6m diameter (this would officially be the biggest in the world, the largest right now is 5.2m). You should take a look at existing companies that make these kind of facilities, take for example http://aerodium.technology/en/models/models/recirculation/ which markets a http://aerodium.technology/en/models/models/recirculation/. They say their recirculating tunnels start at 1.5 million euro, probably for the 3m model; I have to think the 5m unit is at least 3-4 times as much...

It would take a team of engineers with specialized knowledge in aerodynamics to design a wind tunnel like you're proposing (not to mention quite a pile of money).

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.

 

[russ_watters]

Ha, I have no skin in that game. Just throwing out an example of a way to potentially avoid mains electricity. Out of curiosity, what's your beef? Perhaps that deserves its own thread or a PM.

It's just a methane fuel cell, which is fine, but they hyped the crap out of it to the point where people thought it was a perpetual motion machine. They took advantage of gullible 60 Minutes reporters because their investors were getting annoyed that the company was doing poorly:

https://www.physicsforums.com/index.php?threads/380515/

 

[boneh3ad]

It's just a methane fuel cell, which is fine, but they hyped the crap out of it to the point where people thought it was a perpetual motion machine. They took advantage of gullible 60 Minutes reporters because their investors were getting annoyed that the company was doing poorly:

https://www.physicsforums.com/index.php?threads/380515/

Ah yes. Thus the reason I suggested it as an option; and one that is only sometimes economically beneficial, at that. It is apparently quite a bit cheaper than using mains power in California. It probably is more expensive in a place like Texas. Ultimately, my point was that the solution to the problem in this thread ought to be about how to reduce the reliance on mains electricity rather than concocting ways to daisy chain regeneration devices together.

 

[CWatters]

The way I understood the hypothetical scenario was an internal combustion engine with a pulley and belt hookup on the drive shaft to turn a generator would produce electrical energy that could feed the infrastructure of the facility, such as lighting, and although that would could be measured in HP, the decider would be once converted to kWh and see if it may be ginancially worthwhile

So in short you propose to use an internal combustion engine to drive a generator to make electricity. Its quite hard to do that at a lower cost than the grid unless you qualify for a subsidy of some sort. Subsidies are available in some countries for generators that use biofuels and/or provide standby generating capacity.

For example some wind farms in the UK are now adding multiple diesel generator sets on site. These are supposedly to provide backup power when the wind doesn't blow but actually they expect to run them up to 25% of the time. eg At times when the wholesale price of electricity makes it economic to run them rather than only when the wind isn't blowing.

You might be able to do a deal whereby the grid pays you to shut down your sky diving activity in order to use all of the engines power to generate electricity. Hospitals have done similar deals allowing the grid to call on the capacity of their backup generators.

 

[PD Chant]

Sir Balancore,
Solar Updraft Tower. Now you've got me really thinking. People with ideas usually get screwed by the movers and shakers who use such ideas. If I implement such a facility using a modified Solar Updraft Tower you will not get screwed for your input, you'll get paid!
I've a full plate so it will take a bit of time to sort out. But you have my word I shall contact you one way or another.
I maintain my self-respect, honour and integrity; they are most important for any man.
Thank you very much!

 

[Mech_Engineer]

Are you suggesting using the solar updraft tower to generate electricity, or that people "skydive" in the updraft directly?

 

[PD Chant]

Sir Watters,
I do not wish to do anything conventional, but however power is generated I am aware of the potential of feeding the grid. And yes, the government will be interested and may pay. I do thank you for reminding me of that possibility.
Cheers!

 

[Baluncore]

Are you suggesting using the solar updraft tower to generate electricity, or that people "skydive" in the updraft directly?

Both.

Build your free-fall chamber near the base of the tower where you can gently pinch the section to increase the air velocity. It will only operate when the sun is out, but it might be used to generate an energy credit when not being used for free-fall.

 

[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.