Sheerwind
sheerwind.com
sheerwind.com
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.
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?
It doesn't smell right to me.
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.
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.
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?
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.
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.
The history is long and discouraging. Paul Gipe has some good photos of recent attempts: http://www.wind-works.org/cms/index.php?id=541
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.
> "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?
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.
To be fair, this is basic physics though, I'll go cry myself to sleep.
1. In order to drive generator there needs to be a lot of wind. According to Do The Math only small portion of US has favorable conditions for wind: http://physics.ucsd.edu/do-the-math/2011/12/wind-fights-sola...
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.
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:
http://en.wikipedia.org/wiki/Wind_power
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.
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.
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:
http://journals.ametsoc.org/doi/pdf/10.1175/1520-0469%281973...
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.
I see this as a cost optimization, not a way to get more energy from the same source.
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.
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.
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.
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).
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 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.
That would also 'concentrate' the wind.
Presumably, they mean, "some wind returns to the environment"? Currently, I'm reading that as, "massively inefficient".
And it doesn't really "return to the environment" anyway, does it? It's channelled, focused and ?most? of the power is removed.
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.
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?
You could use passive dampers - just a flap basically.
For a good overview of novelty wind energy approaches (taken with a grain of salt) - http://barnardonwind.com/2013/06/03/good-and-bad-bets-new-wi...
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.
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.
[1] http://onlinelibrary.wiley.com/doi/10.1002/we.274/abstract
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.
- 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.
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.
[1] http://www.kickstarter.com/projects/1484284472/windcatcher-i...
I can see something like that as a complementary power generator - it is very cheap if produced correctly.
P = 1/2 x ρ x A x v3 where ρ = air density, A = swept area and v = velocity of the wind
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".
You are right about the second part, those 'tunnels' do catch all the wind of their area.
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.
That thing was huge.
Again I protest the design decision of light gray text on a gray/white background. Higher contrast! :) (sorry to be a broken record).
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?
[1] http://en.wikipedia.org/wiki/Perpetual_motion
[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.]
you need energy to do that, so perhaps by the time 15mph wind gets all the way up to the tower influx, it's less than 2mph
http://en.wikipedia.org/wiki/Bernoulli's_principle (Search for [18] in the Wikipedia article. Note that if z and p decrease from the air being lower and in a smaller pipe, then v increases.)
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.
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.
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.
There are severe economic issues with paying for a giant funnel using the wind it generates.
No one has discussed if you basically turn the funnels into cell tower antennas then you piggy back onto the existing cell phone ecosystem.
Or piggy back onto land mobile radio trunking system ecosystem, or legacy broadcast media ecosystem.
You're building a giant horn antenna. Why not make it conductive and collect some "free" cash?
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.
1) Your 15mph wind would slow down the 45mph wind going in.
2) Retarding the exhaust in any way will reduce the power output of your turbine.
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.
So if you take the cross-sectional area into account, the speedup does not violate conservation of energy.
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.
If so then the wind will just escape into the easy air rather than push a turbine.
If in a pipe then spacing makes not difference.
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.
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.