Oh geez come on Pierre, I think I’ve had some shit at least as high as an extension ladder.
Although, even a stepladder is high enough to kill yourself if you’re not careful.
Just think of my first prototype funded by The California Energy Commission:
Seven (7) rotors on a 70-foot driveshaft on a 50- or 60-foot tower, all on top of a ridge at 5000 feet in the Tehachapi mountains.
It was so high we had to correct the data for the 15% thinner air!
I think it might be one of the highest alternative design wind energy experiments we know of.
I know, I know, it’s cheating to use a mountain.
Oh well, at least it achieved a significant elevation above sea level, up into a true windfarm resource!
Meanwhile, please don’t let my feeble attempt at humor disuade you from pursuing the Omnidea idea.
Please forgive me for not remembering all the details, but what struck me about the Omnidea project was similar to my impression from kite-reeling in general:
They come up with some very impressive numbers that beg the question: If the numbers are so great, why is there nothing in daily operation?
I mean, when you talk about how much power the Omnidea apparatus supposedly produced, I’m thinking: “This thing needs to be run on a daily basis powering a few homes”, but instead, if you go to their website, it looks like they transitioned to promoting it as a mere platform for telecommunications equipment, not producing any power at all, maybe seven years ago(?), but it would appear only USING power. Why is that? Seems like there are always these nagging yet obvious questions with so many of these “futuristic” ideas. It seems like a good step to piggyback on a known project with usable data, but what happened to the Omnidea project itself? Why no follow-up activity if it made so much power? Seems like they went the way of Altaeros, just pivot to what was originally a side-use case (elevating a wifi repeater) and letting that become the new “raison d’etra” for the apparatus, combined with not actually even doing it, just placing the whole concept on a shelf.
There are no impressive numbers in Omnidea’s communication. There are results from experiments I tried to quote. What I think, as noted on the preprint, is that the transmission by the two ends limits scalability, hence the motorized belts.
Hi Pierre:
OK then, please remind o\us how many Watts they supposedly generated, for how long, and what was the size exactly again?
I thought I remembered something like 80 kW - am I misremembering?
If I Google Omnidea, I come up with their website, and if I click on “technologies” I find:
Omnidea | omnidea.net
The spinning sausage is last on their list.
It dpes not even mention reeling for power, but instead cites power going up the tether.
It talks of a stable aerial platform, mostly by the Magnus effect, but does not address how the magnus effect will work when there is no wind.
I don’t think it works in still air, so how is it even a stable platform.
I would also note, magnus effect airplane wings have never found a use, implying maybe a long traction kite could also be useful for generating power.
Anyway, it is all very interesting.
So once again, if you don;t mind, what were the power claims made for sausage-reeling by Omnidea?
Tested power was about an average of 1 kW at about 5 m/s wind speed. This is in the preprint.
No wind, no Magnus effect. It is well known and quite obvious.
Take a look at the basics, as well as the preprint references.
Oh - well that’s a lot for 5 m/s, because there is very little power to be had at 5 m/s. That is a very slow wind speed. About the minimum for the beginning of the meaningful part of a power curve - just the bottom end. How is that even meaningful, except to suggest there is much more power available in higher winds?
Well yes, it does SEEM “obvious”, unless they have some trick up their sleeve. I mean, they ARE sending power UP to the sausage just to spin it, as a start. Who is to say they don’t have a way to keep it aloft? The resulting Omnidea telecom platform is supposed to be for reliable station-keeping. I guess that is only when the wind is blowing. But sometimes there is just no wind, so in that case the platform would fail to function, requiring a substitute or backup - sounds like wind energy in general - needs a backup. No winder we don’t see an Omnidea telecom platform in operation.
OK are you sure there is not some higher power data from Omnidea? I thought I remembered way more than 1 kW. maybe I’m getting it mixed up with some other project…
Informations on a reference of the preprint which took the real wind speed of 5.4 m/s as a basis:
Screenshots from Analysis of Experimental Data of a Hybrid System Exploiting the Magnus Effect for Energy from High Altitude Wind (also a reference in the preprint):
See also (not in the references of the preprint):
Wow, thanks for all that great info, Pierre!
I wonder why they used such a low windspeed?
Is it possible that about 5 m/s was all the assembly was capable of withstanding?
Or maybe their reeling apparatus was not powerful enough for higher output?
To me, it looks like a stretch to think it is viable, as shown.
The amount of power used is so close to what is generated.
Maybe that would change with higher windspeeds!
Their aspect ratio (lenth / width) seems pretty good.
The preprint mentions the source (video) and the times when the info occur.
If this is the case, then the motorized belts around the balloon already make sense.
Power increases by the cube of wind speed, assuming a constant spin ratio. That said there are unknowns in larger scales or higher wind speeds for rotating flexible inflatable balloons. I made some deductions in the preprint but only experiments could confirm them.
There is no viable utility-scale AWES today and by far.
Simple, the airfoil can’t contain much Helium…
Guys, let me boil it down for you:
Standard “Propeller”:
We in wind energy experience an endless parade of supposed improvements on the already-minimalist “Standard propeller-style” wind turbine, which is literally the result of thousands of years of refinement. The same basic “propeller” form serves many uses, both for moving air and water, and for propelling aircraft and watercraft Obviously, the “standard propeller” form has turned out to be very useful, and has in fact become “the way” to accomplish energy transfer from a moving fluid.
Magnus Rotor:
The magnus rotor is a curiosity that has been around for over 100 years, in which time there has been no compelling use-case found for it. Magnus rotors have been tried as sails for boats, wings for airplanes, and maybe even blades for propellers and wind turbines(?). In all cases, it has been found to be suboptimal, compared to just using airfoils. There is no product or machine using magnus rotors in existence today, despite much curiosity and attempts to develop it. Just as you see zero happy owners of vertical-axis turbines, there are zero magnus devices in production. (Contrast with the abundance of ripoff vertical-axis disappointments available on Ebay) You can’t even find a ripoff nonworkable plastic wind energy device device using the magnus effect for sale anywhere!
So, without going into all the details, but simply on the basis of whether the rotating cylinder, as an aerodynamic component, has been found advantageous, (not) it would seem unlikely that a wind energy device using magnus rotors would turn out to be advantageous. This type of analysis uses simple reality, information available to anyone and everyone, rather than publishing painstaking and elaborate theoretical analyses going on for many of pages. Which is more valid? Well, every once in a while, common sense turns out to be the best approach to knowledge.
Now Pierre does raise a valid point, that a cylinder can contain more helium than a typical airfoil with a thinner profile, and that magnus rotors can develop significant lift. So I would not say that it is proven that magnus rotor reeling systems could not take over wind energy, but on the common-sense observation of the usefulness of magnus rotors thusfar, it would seem unlikely.
Having said that, however, it would be an overstatement to say there is no case to be made for what Pierre is proposing, or magnus-reeling for wind energy capture, like Omnidea for example, in general. As some people say, “you can’t prove a negative”, so my mind remains open, but also I should say that for people like me who have seen so many bad ideas over the years, it falls into the highly-questionable category, and I’m not inclined to try to absorb all the details of every (probably) bad idea in wind energy that comes along.
I would also like to point out that magnus cylinders as a fuel saving measure on ships seems viable enough option that several demo ships are using these right now. Whether this is going mainstream or not depends on the results.
I would also like to point out that circumstances also dictate which technology is viable, and that is changing fast these days. Windmills themselves needed subsidies in the days were coal electricity was in unlimited supplies, and the same with electric vehicles and gasoline.
The case of the magnus cylinder though is not as clear because you are comparing with windmill which are not currently being phased out. In the AWE community though, magnus cylinders are only slightly more farfetched than the other options.
For the record I am not a big proponent of magnus based AWE because:
- Seems a bit clumsy and hard to build, a little bit like something from the movie «wild wild west»
- I dont see the price going low enough
- I dont like helium based solutions in general, because helium is not a renewable resource, not is is readily available in the quantities commercial scale magnus wind power would require (I dont think)
- I am not sure about how the magnus effect would scale with size
- I am not sure about changing wind direction
Maybe some of these could come together in a more final design, rather than the current status quo which seems to be: «Q What about this? A Then we do that». But not always easy to combine all «that»s
The AWE picture is no longer blank. Systems have been built that have failed miserably, despite the fact that almost all researchers were unanimously in favor of them. I’m not saying that these AWES are necessarily doomed to failure (although I think they are), but that at the very least, we can try to examine deeper what we would have called Plan Bs at the start of the massive AWES investigations.
Omnidea obtained correct experimental results. However I think that holding the balloon only with the two ends limits the ability to scale a lot. It is the reason why several belts surrounding the balloon is a better way to mitigate the strength on the balloon, allowing to avoid the requirement of a heavy frame when it scales up, using only flexible and light material.
And if the balloon has a large volume, a small amount of buoyancy per m³ (of the order of 10 grams/m³) could be enough to ensure lift-off when no wind at ground level (and sun).
Helium or hydrogen would then not necessarily be required. We would use solar thermal on the black ripstop envelope. This would make it possible to stay in the air for most of the time, with the sun and the heat reserve provided by the volume providing buoyancy, as well as the aerodynamic lift provided by the Magnus effect, even with little wind. The motors turning the belts would be lighter than the axial motors at both ends, and would also lower the center of gravity of the whole, which would be a plus for stability. That said the control of buoyancy by thermal solar could be a blocking factor for viability. Tests will say. If helium is used, the balloon should be light enough to limit helium volume.
It would be difficult to crash a Magnus balloon, and in the event of a problem you open the valves at the ends, the balloon empties and descends quietly, controlled by the multitude of tethers along the ground station. I’ve managed to do this with my solar balloons (deflation by returning), so why not with a Magnus cylinder, which by the way isn’t very difficult to make, starting with not expensive but fragile HDPE film for first experiments during less than a day.
Finally, if the reeling application is not chosen, the use as a carrier could be envisaged.
The scalability of any inflatable devices (see giant airships and blimps) can be a major advantage.
Of course, all this is partly theoretical and requires quite a few steps to perhaps be validated, with a reasonable chance of success of 1/50.
I would expect to see a Life-cycle assessment - Wikipedia of the idea. Now it looks like you will be using enormous amounts of plastics that need to made from fossil fuels and replaced quite frequently for very modest electricity generation. You’ll also occupy a large land area, compared to the alternative, and lower the albedo of a large surface, if you’re going to go for solar heating of the balloon, which would contribute to global warming and have an impact on the local environment.
I do also wonder about the hoop stress of such a large cylinder pressurized to withstand the wind, and the weight of the material needed to be able to handle that. The pressure needed to be able to handle wind loading was discussed previously on this forum if I recall correctly.
The concept also would of course be competing with the HAWTs of decades into the future, which should be able to produce as much or more with just a few units.
I was thinking about this idea.
Are you supplying heating from the ground to keep this airborne through the night and on rainy days? Maybe do some calculations stating the weight of the device plus wetted water from rain, temperature difference required to stay airborne and how fast temperature leaves the cylinder in zero or low wind conditions. Or - is landing the device still on the table?
I think you should say if this is a Helium device or not. If you say yes, it wont fall down and you wont probably find enough Helium for this scale. If you say no, you should look into the numbers to keep it flying. If you say you could land it automatically (as opposed to assisted with cranes for example) then you dont need to focus on 24/7 airborne but then rather explain in more detail how you intend to land.
I think getting this concrete in design choices is necessary if you want to get the right feedback and be taken more seriously. Remember we hant to help first and foremost, between our rage fits.
The weight of any airborne equipment must be calculated. Maybe also find the minimum dimensions where the chosen solution could work. If the minimum dimension is very large, this could make it more worthwhile to look at the material strength of the cloth etc. This way you could maybe easily find some unsolvable flaws now, saving you from putting work into a dead end.
There is an interesting material aerogels that could help with insulation to extend the high temperature time at a cost of quite low mass. Maybe.
Also, what is the maximum external temperatur you could use, with the required temperature difference? Would this work on a sunny day in Spain (50 deg celcius) without special (heat resistant) materials for the cloth?
Hmm, another warning sign - talk of using hot air for buoyancy, are we back to the 1800’s before airfoils again? well, maybe…
I wonder about having the drive belts go all the way to the ground and double as tethers in some way, to avoid placing motors in the air (extra weight).
Combination of buoyancy and aerodynamic lift by Magnus balloon. Buoyancy allows to stay in the air when no wind, and (with thermal solar) allows takeoff by no wind at ground level.
Possible by using the Magnus balloon as lifter, not possible by using it in reeling mode.
Well actually still possible, eg place the ground station on a cart. But there are several options just using moving pulleys…
Having most of the hardware on ground sounds very nice to me
For a balloon the only real option should be hydrogen, if that somehow, somehow, somehow, is not possible, then humid air:
If you keep the humidity low enough and the outside temperature is high enough, or if the balloon is very well-insulated, there should be no condensation on the inside of the envelope. In practice there will probably be condensation. With a non rotating balloon you could collect the runoff and again heat that up, with a rotating balloon that becomes a little more difficult. Perhaps you could vary the radius of the cylinder to create channels for runoff, which you can then wick up or scoop up.
You also shouldn’t go for a solar balloon, as that would have a high emissivity. You instead want as low an emissivity as possible, to limit heat-loss through radiation. You should probably assume that any environment where insolation is so high as to help significantly, you should probably just use solar panels. So ideally an aluminium coated insulated balloon, but in practice probably just an aluminium foil coated balloon (perhaps with baffles along the inside of the envelope to limit air circulation somewhat close to it) which should also help with resistance against uv-radiation.
If you wanted better insulation properties, you could for example fill the balloon with smaller balloons or have one or more concentric balloons inside the main balloon, with only the outside balloon needing higher strength and resistance against uv radiation.
Or, have only the inside balloon(s) filled with higher humidity air, and the outside balloon filled with dry air to improve its insulation properties. If the inside balloon(s) also are non-rotating, you could optimize their construction further to limit convection.
You’d supply the heat from outside using a heating element. You would need to do that using a heating element to be able to create steam to raise the humidity, among other benefits over instead transporting heated water through thin hoses.
Also before talking about adding however many belts, you could try to calculate the pressure needed to support a single belt, and then what effect having this single anchor point would have on the balloon, given the bending load the wind and buoyancy would put on the balloon. Then you could think about perhaps using two belts and the ideal placement of them, from the end of the beam, again given the bending stiffness of the beam.
I think laws should be passed requiring all aviation to use humid air for lift.
I think you make some good points here. Though we discusse hydrogen lift earlier, the problem is in safety and also leaks. Leaks is bad for energy production because presumably the production of hydrogen is pretty energy intensive. Also, is it prectical in the long term? When you get air in the cylinder over time, you would need to flush the cylinder with fresh hydrogen to get rid of it. That means the hydrogen must be recycled? In that case this could hardly be viable?
So I guess hot air is the better option. Solar panels and aerogel insulation maybe as a starting point design. But this sounds awfully hard to get everything working together