I am not an expert in wind turbines, but I am technically an EE, so I have seen a thing or two. I have mixed feelings about this.
On one hand, the principle of operation superficially looks OK. The weird shape probably gives more flexibility in the design (I say probably because I honestly don't know anything serious about fluid mechanics). The data they provide seems usable.
That being said, the website is fairly scarce in terms of actual details (e.g. the "collected wind is channeled to pick up speed" doesn't seem to be explained anywhere -- how exactly is that done, and how much speed would the wind gain?), and the only paper they published looks rather meagre -- from the works they cite to the dubious editing of the paper (e.g. last sentence before "Conclusions": "The total energy production of INVELOX over 8 days is about 314%" would not have made it past decent peer reviewing).
I don't know enough about mechanics to make a proper assessment of this, but my bullshit detector is bleeping, though shyly.
Edit: BTW, the website also seems to casually glance over what the (up to) 600% improvement improves upon. If I read their article correctly, it's an improvement over using the same turbine, but without the funky tunnel. In that case, I kindda doubt the economical feasibility of this design.
Your BS detector should be bleeping at full force. There is a long, long history of failed attempts to build ducted wind turbines. The fundamental question is whether, for the revenue you'll gain from the energy gains, it's more efficient to put the money into building a duct or extending your turbine blades a bit more. Unfortunately, building all the extra structure to support the duct is expensive.
> "collected wind is channeled to pick up speed" doesn't
> seem to be explained anywhere -- how exactly is that
> done, and how much speed would the wind gain?
I'm not saying that your bullshit detector isn't justified, but that is a fairly self-explanatory claim (well, the "how" part anyway, numbers are lacking).
When you have an input flow, and the cross-sectional area is decreased, the speed has to pick up to compensate.
For example, if you have a fluid flowing through a 2ft-radius tube at 10 cubic feet/second, just divide the volumetric flow rate by the area to get a velocity of 5/(2π) ft/s. If later in the tube, the radius decreases to 1ft, that reduces the cross-sectional area by a factor of 4. But, 10 ft³/s is still being pushed in, so that's what needs to come out. That comes out to 10/π ft/s.
I'm sure there are losses when the fluid is compressible, but wasn't a sentence that tipped off my BS detector.
I have show dead comments on and viewed his history. It's so sad - he comments every few days and oftentimes multiple times per day. He was never given chance to redeem himself to the community. That stinks.
My biggest problem with it is that no one outside of SheerWind has been allowed to test the system.
It kind of sounds like what happens with Andrea Rossis Energy Catalyzer[1], he was able to get milions in fundings over the years but never allowed to test it objectively claiming the reason is that he sold his patents or something. Several years later you can still not buy a cold fusion reactor.
"I don't know enough about mechanics to make a proper assessment of this, but my bullshit detector is bleeping, though shyly."
Mine too…
One of the fundamental problems regular wind turbines need to deal with is the "V cubed" term in the power contained in moving air. For exactly the same reason that you need eight times as much power to make a car go twice as fast – if you build a turbine that can produce it's "nominal power" output in, say, 10m/s (~22mph) of wind, it'll need to be able to somehow deal with the turbine operating at 8 times nominal at 20m/s (45mph, a not unreasonable occasional windspeed in many places) and 27 times nominal power at 30m/s (a high, but certainly not yet "beyond reasonable safety design limits" speed).
My problem is with the numner on their Field Data page - they say they get an average "speed Ratio" of 1.8, and their turbine is rated at "600W at 12.5m/s". Ballpark extrapolation follows. I'll assume that's 12.5m/s at the turbine, or 12.5/1.8 = ~7m/s wind speed. About 15mph. At half that windspeed, there's 8 times less energy available, so 7.5mph of breeze will generate 75W, halve it again and output at 4mph drops down under 10W, and 2mph means low single digit Watts of output.
Now think about what happens to their turbine in a stiff breeze of 30mph? Where does the 4.8kW go? and when the once-in-5-years 60mph storm comes through, somewhere the best part of 40kW needs to be dealt with. Who engineers things with almost two orders of magnitude margins of safety?
Coudldn't you just close the tube? I assume they already use some kind of a one-way valve so the wind on the other side wouldn't suck and lower the preasure in the tube, you could just close this valve if the wind is too high, or even just open it a bit so you could still generate electricity?
Or better still, provide some kind of variable restriction such that the air flow through the turbine is right at it's max operating power.
Furthermore this tower isn't a lossless device, as the wind speed picks up I would guess that it gets "draggier" and less efficient at channeling and accelerating the wind.
But even if that's not the case making a variable restriction that could moderate the tunnel wind speed is a very easy problem to solve. Some kind of a damper and a control system that measures wind speed and adjusts the damper accordingly. You might even be able to use the turbine to do the measuring if you're clever.
This seems precisely like an argument for a smaller turbine-based design INSTEAD of huge and (relatively) heavy blades. Turbines for car turbochargers and airplane engines can regularly (if I remember correctly) operate in the regime of ~100k RPM.
And like other commenters say: I think it would be much easier to restrict flow in the "funnel" part and most things I can imagine for a freestanding wind machine.
> Now think about what happens to their turbine in a stiff breeze of 30mph?
If the wind that goes into the turbine goes faster than a certain threshold, let some/most/all of the wind flow past the turbine. Maybe there is even a way to have the wind itself do that mechanically, similar to a pressure valve.
Right, drag scales with the square, but you're also going into that drag at a higher velocity, so power scales with the cube.
Or to break it out at more length, work is force times distance, right, and power is work over time. If it takes X amount of work to cover a distance at a given speed, it takes 4X to do it in half the time, since, as you point out, the drag (force) scales with the square of velocity. But you also accomplished that work in half the time, so the power required is 8 times the original. Make sense?
There might still be something interesting in this design compared to the conventionnal wind turbines, if you imagine several output tubes and control the closing/opening of those tubes according to windspeed you'll be able to modulate the nominal power you mentionned.
You just need a "wastegate" similar to what is found on an automobile turbocharger. If too much air is moving into the generator turbine, you open some vents to bypass it.
I agree 100%. You can't just say "X% better" without defining the specifics of the environment in which you're operating. If they're claiming X% better in all environments, they're absolutely, 100% full of shit and they either need to stop outright lying, or do more work to validate their mistaken claims.
I'm not an ME or an expert in fluid mechanics, but I'm still curious.
I wonder how the efficiency of this compares to maximum power point tracking coupled with variable pitch turbines (minimizes airspeed required to start, but adapts both mechanical and electrical parameters in order to have peak power transfer at every windspeed)?
I wonder how the boundary layer introduced by the duct impacts efficiency. I understand there is a relationship between air velocity and efficiency, and I assume that it's easier to make high velocity systems more efficient, but in a ducted system such as this you're trading some of your total energy for a bigger pressure differential, and therefore speed. Is the amount of energy you're trading made up for by the gain in efficiency on the low-speed end of the curve? I imagine that on the high-speed (ambient wind, not flow over the turbine) end of the curve there's a drop in efficiency. It would be nice to see this quantified.
Yes, at first I thought that the x6 improvement was over real scale turbine or at least a turbine of comparable bulkiness.
In France more and more people put wind turbines on their roofs, even if the kwh production is far less than promised by manufacturers (gaps between forecast production and real production of +6000 %, yes that's 60 x are common). The authorities are even giving subsidies for the installation of those inefficient turbines. This might prove better for small scale installations.
2. This actually moves air, which robs a portion of kinetic potential even before it get's to generator. There are probably few more caveats with this that I am not seeing.
3. What happens with used wind? It just get shot out of the bottom? At what velocity, website speaks nothing about safe utilization of "accelerated" wind. So if we get 30-40mph wind, what happens at the bottom?
4. What will happen when it rains? This thing will channel water flying sideways just as well as air. So not only turbines need to be waterproof, but now imagine point 3 with heavy rain.
5. Wind turbines safely stop when wind velocity gets too fast. This will be harder with this construction because wind is accelerated. If wind turbine stops and they do not close some kind of shutter - see point 3.
Note: to be fair, part of the issue could be fixed pretty easily by directing exhaust back up. This however still presents problems with water and robs yet more power of winds kinetic potential.
I applied to ycombinator with this idea two years ago, I read an article about how the wind turbines were driving people who live near them crazy with the noise they create. Having a funnel that would capture the wind, then put it through a turbine, plus the ability to channel the wind, seemed like a good idea. However I am not an engineer, never finished college, and am over 35 which may have hurt my application :)
Unfortunately, I think part of the reason your idea was rejected was that it's just a bad idea.
The thing is, you -- non-collegiate, over 35 -- are nonetheless capable of doing enough research yourself to determine if an idea is very good. One thing to consider is the cross-sectional area of the funnel -- the size of the mouth. Another is a relation mentioned here: the power available (dF/dT) in wind is proportional to v^3. You can look up "power available in wind" here:
You'll be able to test your idea by considering a few scenarios, like "how does the force on the funnel (~area v^2) relate to the power generated (~area v^3) and is this practical?" and "Where would wind farms most likely be located, based on power availability (remote high-wind areas)?".
I say this not [primarily] as a criticism, but to hopefully recommend to people that they can use simple math to test their ideas using pubically available information. It helps you form ideas with a closer relationship to reality. Doing research can be good for you, and elementary physics shouldn't be daunting, especially if you're taking things as far as applying for angel funding. Having a broader knowledge base doesn't hurt for coming up with ideas, either.
Hi, please don't be fatalist over those things, that's just being unconstructive. You were probably rejected because you had no engineer to validate your idea.
That was the challenge, I couldn't think of a way to make everyone in the whole world want the product but it seemed like an interesting problem because giant blades spinning just can't be the future of wind energy. The blades take out too many birds and make too much noise. There is a wind energy project maybe 40 miles from me, the installation of the towers and movement of the dirt has caused dust storms for the local residents. A funnel system could be longer and have more support of a wider area, requiring less digging. Big corporations would only switch if they can build it for less and make more money through additional production from each unit so it is unlikely there is big money in developing it, it would have to be a Bill Gates type save the world project and give the designs away for free.
> However I am not an engineer, never finished college, and am over 35 which may have hurt my application :)
I think it was more that the idea is far afield of what YC typically invests in (computer software/hardward) and what YC understands. They understand and accept their circle of competence and don't want to put money toward something they might be unable to assess accurately.
As others have mentioned, the air increases in speed because of the Bernoulli principle: the decreased cross-section increases the dynamic pressure. However, most of the power will be lost in friction, during the "channeling" part -- and the increase in speed will not make up for that loss.
The friction is relatively high because the flow is turbulent, not laminar. The friction factor can be calculated with the Colebrook equation, implicitly; if they did the calculation they would realize that the distance between the intake and the turbine is a mistake (especially the height difference, which doesn't make sense for atmospheric flow).
It would be better to use natural land features that create the kind of flow you need, such as mountains. Look at the figures here for inspiration:
The same principle have been posted many times. The only important thing, is the surface area of the collector, that where the energy comme from.
In this case, think about the cost of all this structure vs the same area swept by a blade. The cost of the simple blade is always lower than the same area of 'concentrating funnel'.
Right now they are building turbine with blade of 90m of diameter, imagine building a concentrating structure of the same size.
This is an absolutely awful idea, as it was every other time someone's had it.
Consider the following:
a) The maximum amount of energy you can get from some wind is a function of the velocity and density of the air and the projected area of your generator. You can't go above 59.3% of the original kinetic energy content. Conventional three axis turbines get pretty damn close to this limit (80% or so).
b) That being the case, getting cheaper or better power is a matter of getting a large projected area for a low cost while still keeping pretty good efficiency.
c) If you cover a large projected area with a small amount of material, and can point your projection to face the wind... you will do quite well. This is what conventional turbines do.
d) If you cover a large projected area with an even smaller amount of material you may do VERY well. This is what Makani power acheived before they were absorbed into GoogleX.
e) If you cover a small projected area using an astronomical amount of material, which doesn't turn but is rather built for every direction, you can expect to do really really badly... no matter how many bullshit mystery air acceleration tubes you include.
It's bullshit.
*edit: I know nothing about the people who are proposing it. They may be doing so in good faith and not realize it's a terrible idea. But it's still a terrible idea.
> The unit is about 50% shorter than traditional wind towers
This is the same thing people say about VAWTs... but they don't build HAWTs really tall just for fun, the wind speed is faster and more consistent up there. So all they are really saying is "the one we built isn't very big"
I think the biggest benefit to this design is that it looks like it could be dirt cheap to make and maintain since it appears to have very few moving parts exposed to the elements.
Why is the funnel intake octagonal? Making it circular would be more aesthetically pleasing, or is there a technical reason why having 8 'separate' entrances is required?
Secondly, paint the funnel intake and top section green, and the 'trunk' brown, stick these on top of a hill, and from a distance it could pass for a tree. Much more visually pleasing than a traditional wind turbine.
I suspect the walls in between the "separate entrances" force the wind moving semi-perpendicular to those walls into the entrance as well. Removing them would lose wind.
Without the compartments/channels/separate entrances, wind blowing in from one direction would mostly just go around the central pillar, rather than down into the funnel.
> Much more visually pleasing than a traditional wind turbine.
But also much larger. It's an inescapable fact that wind energy is proportional to the area captured. So these would have to be as tall and wide as turbine blades.
Except it would be a massive structure, not just a small thin blade on a pole.
And don't think they could get away with flimsy walls either - the pressure of the wind on this thing is the same as the pressure on a regular turbine.
I suspect this last point will sink this project except perhaps in zones with very light wind that can benefit from it's ability to generate with low wind speed (and low pressure, so a weaker structure).
I doubt that the aesthetics are the prime design consideration. This is to generate electricity, not to stick in a gallery. Power generation isn't generally pretty, but it keeps people alive in the winter.
> I doubt that the aesthetics are the prime design consideration. This is to generate electricity, not to stick in a gallery. Power generation isn't generally pretty, but it keeps people alive in the winter.
They are a design consideration though. You can't just stick things where you want: there are political and community issues to consider. Many rural communities might object to functional-but-ugly wind turbines littered about "their countryside".
The physical rationale is fundamentally flawed. It assumes that all wind that is "caught" will enter on the big opening and all of it will leave on the small opening. But that is wrong, the smaller of the narrow region the less wind enters the entire construction.
The fundamental flaw of the rationale is that it confounds the concept of an engine to that of wind entering the tube. If you suck cold air into a compartment via a valve and provide heat inside it the air expands rapidly and must leave because it does not fit inside anymore. But note how we spend a lot of energy to expand the air and turn that internal energy into mechanical energy. There is absolutely no way that you could get air freely inside of a tube and have it "speed" up without actually pushing back on the air that is coming in.
Imagine that you close the narrow part completely. What happens? Will the construction blow up, of course not? Will the the pressure inside rise to a high value? Of course not. It will simply fill up with air and will experience as much pressure as the wall of the building is subjected to. Can you make the closure experience more pressure than any other part of the building? No that is not how pressure works, it is uniform inside the building.
Now imagine that you make a teeny tiny hole in the closed area. Will that lead to air leaking at insane speeds? No it will be barely noticeable, almost no air would be coming out. There is no reason whatsoever that the air would voluntarily go into a building than on it is own choose to leave on the tiny hole instead of leaving the same way where it got in (basically it is not getting in at all because the pressure inside is the same as outside)
Does it work, of course to some extent, take the area of the building that catches wind, multiply it with the speed of the wind and density of the air and you get the the mass and volume of air that is moving. Air is actually pretty light, you would be surprised how big the area needs to be.
It's being done, actually. Company called Ogin (was FloDesign Wind Turbine) is developing a 100 kW shrouded wind turbine that is similar to that idea. But it only works on small machines, can you imagine a 100 meter rotor with a shroud around it?
This design optimises for low-wind speeds by exploiting the Bernoulli Principle but the problem with doing that is that there is very little energy available in the wind at low speeds to begin with.
It's more practical to aim at higher wind speed sites (e.g. off-shore, or simply by being much taller) simply because there is vastly more energy.
I'm not specialist in fluid dynamics or wind, but isn't some energy going to be robbed by the intakes on the sides not receiving the brunt of the wind? I would imagine that the passive sides would rob the tunnel of pressure.
However, if this problem exists and does reduce efficiency, I reckon it's an easy fix that just requires adding dampers for each of the channels and opening them for the ones receiving wind and closing them when not receiving wind.
Out of curiosity, what's the fluid dynamics equivalent of a parabola for energy rays? i.e what shapes are known to concentrate and accelerate fluids best? I know a venturi nozzle is one such shape for acceleration of already collected fluids. What's the best collector shape?
They would have to use dampers. Otherwise the wind will enter one side, flow down the tube, then right back up the other side since there is less resistance that way compared to pushing a turbine.
You could use passive dampers - just a flap basically.
There has been a lot of hype on low wind speed energy production for years and Sheerwind is just one of the "contestants" of challenging the laws of physics - i.e. there is only so much energy per m3 air / wind power density provided with low wind speeds and you can't harvest more than 100% - also see Betz's law.
This is an optimization, they're not trying to extract more energy than the wind contains. They're taking 500sqft of wind and channeling it down to 100sqft where their 100sqft wind turbine is. 2mph*500sqft/100sqft = 10mph ignoring all the viscous losses and backpressure, both of which there will certainly be some of. So perhaps instead of 10mph you get 8mph.
What they've done is made a 100sqft wind turbine which would have a high cut-in speed effectively a 500sqft wind turbine with a lower cut-in speed. No magic, just a bit of clever engineering provided that the tower is cheaper than the 500sqft wind turbine.
According to my old aeronautics professor, 2-blade turbines are the most efficient when pointed directly into the wind. They've tested 3-blade, 5-blade, and vertical turbines and couldn't get the same amount of output. These experimental turbines look great on paper but rarely scale up.
The reason why 3-blade is the most common design is 2-blade turbines induce a lot of harmonics at high speed. 3-blade cancels it out but are slightly noisier from the blades slicing through the spoiled air.
Actually it is the opposite [1]. Efficiency is theoretically increased with more blades. The three-bladed turbine is the most popular because of the cost benefit of building blades vs efficiency gain of extra blades - although the case of harmonics for even number of blades does hold true.
If I read various parts of their website correctly it sounds like they aren't in the turbine business(yet), but building this funnel thing around many existing turbines.
Interesting, but I'd like to hear from someone other than the company that's making them. I'm kinda suspicious when I only hear the upsides to something like this.
The mechanical power carried by wind is normally a cube function of its speed, which suggests that the surface area to generate substantial output from slow winds have to be enormous.
This doesn't seem to be the case here. Until there's an independent confirmation (and there seems to be none so far), I'd file it next to cold fusion folder.
Ok, the air would flow into the channel facing the wind, but wouldn't it also be sucked out by the side channels as the wind passes by? A movement of air creates a pressure drop proportional to the speed of wind so there would be a sucking force on both sides of the tower (Venturi effect) - did they address that?
Yes, but they aren't mentioning that, and I suppose this is quite an important ommission. And btw, valves would create additional drag and reduce efficiency of the device.
- What are the details of the system inside?
Sorry, we do not comment on the details of the inside of our INVELOX system because they are part of our trade secret.
So it is not unreasonable to assume that they have something in there. And they could be needing the valve anyway to close the tube if the wind is too strong to protect the turbine.
There's a paper published by sheerwind, detailing the principles of operation - http://sheerwind.com/wp-content/uploads/sheerwind/2012/10/Al....
There's no mention of any valves, too. But there's a more interesting claim they make: "(...) INVELOX captures the wind kinetic energy
and uses the pressure differentials to increase the kinetic energy
available to a turbine". I wonder how they manage to increase the kinetic energy of air flow without any external energy source.
The more I read about it the more I get the feeling that their goal is to get as much funding as possible without letting anyone test it, kind of like Andrea Rossi and his cold fusion reactor.
This looks much more difficult to clean, think of all the bugs, birds and sediment that will stick to the INSIDE of that funnel structure. Cleaning the blades of an ordinary wind generator seems much simpler.
On the other hand, if this is as tall as they will get, it seems a lot safer to work on than the current behemoths.
If the wind gets slowed by turning the turbine, shouldn't the output side funnel of the turbine be larger than the input side funnel to be able to hold more air? (So the additional wind coming in from behind doesn't have to waste its own kinetic energy pushing the front air out of the system)
Would turbulences be prevented if 3 radial blades (3 so the 45:15=3fold amount of air can pass without problem) divided the wind from the turbine into 3 funnels as large as the input funnel?
This is a nice concept. In populated areas there is quite a bit of pushback from the population to install wind turbines due to the distracting movement of the blades and their shadows. This idea solves that nicely by hiding the turbine. Maybe the marked for this is densely populated Europe?
I feel like this is worse though, as a tower like that looks million times worse than a wind turbine. I would hate if structures like that started appearing across the landscape.
We already have square structures in the landscape: office buildings. These could be put on top of regular buildings keeping the shape of the buildings, just making them a bit higher.
The swept area of regular wind turbines seems enormous compared to sheerwind's turbine's. Even the combined area of those 8 entrances look much much smaller. How in the world is this going to compete with those giants? What am I missing?
Nothing important, I think you are on the money - the comparisons on their website are utter bogus - the swept area of the turbine they compare against are not the same.
Don't be silly yourself. What happens if you add or remove a blade, or change their shape or pitch? The swept area stays the same, but the energy captured changes. The "swept area" is a useful abstraction that gives us the total energy that you can extract from - with your formula - but it's the blades being there with their length that extract that energy.
These wind towers on the other hand capture and manipulate the whole air flow from the area of their intake, not just the part directly interacting with the blades of a traditional turbine. That's why it is physically possible to extract much more power than with a traditional turbine with an equivalent "swept area".
That's right, the above formula is just the power of the wind, the amount of energy you are able to harvest from it does depend on the characteristics on the blade. The swept area is still a key factor. (see Betz limit for another interesting fact)
You are right about the second part, those 'tunnels' do catch all the wind of their area.
Ok, I think you got my point. To sustain it: "Theoretically, an infinite number of blades of zero width is the most efficient, operating at a high value of the tip speed ratio. But other considerations lead to a compromise of only a few blades.[22]" http://en.wikipedia.org/wiki/Wind_turbine_design#Blade_count
If I look at http://sheerwind.com/technology/field-data it seems to me the 600% improvement is highly deceptive: that huge funnel tower gives up to 600% (average 300%) more output than the same tiny turbine inside it when it's just placed on top of a pole.
If you want to use this technology to boost the output of a modern 100m diameter turbine by 300%, you'd need to build a funnel tower that's over 1km high. I kinda doubt that's cheapter than building three of those turbines.
Also, the longer tube you build the less effective the system becomes because the pressure at the top has to move the entire column of [viscous, turbulent] air down the pipe. I haven't done any math on this but I'd imagine it would not take that much height to hit a point at which point piping losses become overwhelmingly large in proportion to the energy you're producing. The turbine and the inlet need to be close together.
Yes it does, if the wind is too slow for a normal turbine the normal one outputs 0 kw/h and this one more then 0 and therfore if you let it do its job it will naturally produce much more power then the one which doesn't produce anything.
Okay so it starts with normal wind at as little as 2mph (influx) and then with series of venturi tubes and processes the wind is sped up to 45 miles per hour. Then the blast is shoved through a turbine generating electricity and an exit wind at 15 miles per hour (efflux). All right.
So why not take this efflux wind at 15mph back to the top again, or even half way with some loss of course, and achieve a perpetual motion machine [1]?
Is something missing in the introduction video about this concept?
[Okay got it: The blade area/size of a fan to turn at winds as low as 2mph is quite high (and expensive) as compared to rotor blade size that would work with winds at speed 45 miles per hour. This one looks like a play on lever action of wind on fan blade area/angle w.r.t achievable influx velocity. Not too bad it's a kind of optimization, but for the introduction video that wasn't clear enough.]
The reason to make it go faster is that you can't spin a turbine to generate electricity if the wind is 2mph, unless the turbine is really, really big.
Yep, driving wind faster is the key to lowering the size of the turbine's rotor blades.
It's an interesting optimization, but the broad design of the tophat might face challenges from adverse weather. During hurricanes or say something like 100mph wind, the upper flower has to recede to save itself. This is not the case with standard wind turbines that just rotate only faster. I am sure they must have thought through all these situations, simply considering only 600% improvement over standard installation doesn't seem like a good way to compare.
> This is not the case with standard wind turbines that just rotate only faster.
Standard turbines are not left to rotate in high winds -- if they would be, they would destroy themselves. There's a link to a video of this happening in this here: http://www.youtube.com/watch?v=_e9uRSVun30
Instead, they are feathered and locked in place. That is, the angle of attack of the blades is reduced to zero so that wind hitting them won't make them turn, and then there is a huge brake in the system that keeps them in place.
Yes, I am aware of the extreme torsional scenarios -- did mechanical/flu-mech course in engineering -- thanks for the video. In case of Sheerwind's funnelling technology a normal windy day could also become a challenge though.
Luckily, as the cross sectional area shrinks, the price of valves shrinks. As for pressure inside the horn theoretically bursting it, well, I think you'll be OK but if you insist, protection gear would be little more than hinges along one edge of a panel and a spring on the other, not much different than a very large turbocharger wastegate (very large as in stationary multimegawatt class diesel size)
The speedup comes at the cost of the decreasing the cross-sectional area of the flow. The input is 2mph x [big cross section], the output is 15 mph x [small cross section].
So if you take the cross-sectional area into account, the speedup does not violate conservation of energy.
There's less energy in the wind after it leaves the turbine (by necessity, energy is transferred into the turbine to make it turn). If you were to expand the air moving at 15mph to the same size as the inlet its' velocity would decrease in the same way that funneling it down increases that velocity. Plus losses from viscosity and turbulence.
Technically speaking, you could add a second stage turbine to it but you'd be getting a lot less energy out of it and it's probably not worth it. Something similar is done in the natural gas turbine world with combined cycle turbines, where a natural gas turbine is operated at very high temperatures and pressures, producing a lot of energy, and the exhaust (for comparison: the air/gases coming out of it) is still hotter and higher-pressure than atmospheric air. This exhaust is fed to a steam turbine which manages to capture some more energy out of it on its' way back into the atmosphere, where it leaves lower-temperature and lower-pressure than it did from the gas turbine.
Also, for any real-life physical system involving airflow, even if you had perfect turbines that cost zero dollars, everything creates viscous drag with the air that lowers velocity/energy/etc.
The Venturi effect makes speed inversely proportional to pressure - I'm assuming there isn't enough pressure [as the turbine generator harvests most of it] to take the wind back up into the intakes.
Also I don't know how much gravitational forces are at play with relation to winds - but bear in mind wind is nothing more than the movement of gasses and as such can be treated as a fluid, so I'm assuming gravity aids the Venturi effect, but must be fought against if you want the wind to go back to the intake.
You could do this without having to "move" the exhaust back up to the top I think.
Just stack them in a line at different elevations so that one's exhaust turns into the fuel for the next one. If speed of the exhaust increases after a cycle you'd be creating stronger "breezes" as you go down each step.
It wouldn't be 'perpetual' but pods of 3-4 like this might be able to increase the yield substantially.
Then again I don't know much about this and I'm just trying to comprehend it all.
This is doable, and it's done in the natural gas turbine world (look up combined cycle turbine, essentially you hook up a lower-power steam turbine to the exhaust of a natural gas turbine).
The main problem is that turbines are expensive and lossy, and when the main turbine is already going off of a relatively small amount of wind energy, the amount of energy you could produce from its' output is probably very small.
if you output one into another, the resistance would back up into the first one and reduce its output, or else the pressure would push the air backward out one of the other tubes of the 2nd device and not spin the rotor.
Well the "pod" could be set up with multiple levels so that every subsequent level receives a mixed flux of natural wind and the ejecta of the previous level, no?
There's also the factor that pushing the turbine blades takes energy. Otherwise, you could just take any turbine based generator system, and put hundreds of turbines in a row!
This is not the reason why it won't work. The 15mph flow will be much thinner than the original input flow, so feeding it back into the top will not have the same effect.
I'm no expert, but the area subject to the wind seems quite different, the total amount of area moving is the same, it just goes through a smaller hole.
It seems to lack any kind of physical explanation of why it should be more efficient than traditional turbines? All it says is that it uses a smaller turbine - are those more efficient? I would have expected larger turbines to be more efficient (just on the grounds of larger fans in PCs making less noise...)?
It seems irrelevant if the turbine is sitting on the ground or not. "Accelerating" the wind also seems kind of irrelevant - they can't create energy that way. However, if they manage to drive a turbine with little wind that way that would otherwise not have worked, perhaps it is a win.
Maybe it is a good technology, just saying that I don't see any reason in the text of why it should be. At least they could have written "small turbines are x% more efficient than large turbines" or sth like that.
They don't say anything about that, I assume you could close a valve or something, that way it would be easier to controll the flow of wind then with a normal turbine.
On one hand, the principle of operation superficially looks OK. The weird shape probably gives more flexibility in the design (I say probably because I honestly don't know anything serious about fluid mechanics). The data they provide seems usable.
That being said, the website is fairly scarce in terms of actual details (e.g. the "collected wind is channeled to pick up speed" doesn't seem to be explained anywhere -- how exactly is that done, and how much speed would the wind gain?), and the only paper they published looks rather meagre -- from the works they cite to the dubious editing of the paper (e.g. last sentence before "Conclusions": "The total energy production of INVELOX over 8 days is about 314%" would not have made it past decent peer reviewing).
I don't know enough about mechanics to make a proper assessment of this, but my bullshit detector is bleeping, though shyly.
Edit: BTW, the website also seems to casually glance over what the (up to) 600% improvement improves upon. If I read their article correctly, it's an improvement over using the same turbine, but without the funky tunnel. In that case, I kindda doubt the economical feasibility of this design.