Thank you Pierre for a video of the sailboat actually sailing. Still seems a bit strange to me that the other video does not show it in use. My impression is it has no camber, which limits effectiveness. Yes I’ve seen videos of the flying whoopee-cushion before. Don’t see anyone actually using them at our hang gliding club. I do believe it is a clever idea, and clever implementations with the telescoping mast. It is the kind of idea I’ve been enthusiastic about since I was a kid. But during that time I’ve also realized not all such seemingly-no-brainer solutions turn out to be practical. Take hydrogen as energy storage for example. It “sounds” so great as long as you are unaware of the problems that make hydrogen the world’s worst form of energy storage.
At a quick glance, hydrogen sounds like the answer to all problems. But then you learn it can only produce a quarter of the power in an internal combustion engine, that a fuel cell is only 50% efficient as opposed to batteries being 90% efficient, that compressing or liquefying H2 takes almost half of the energy it contains due to the extremely low density which includes energy density, that a hydrogen car would have to use most of its volume just for the fuel tanks, which would be expensive and heavy, that electrolysis is only 50 - 60% efficient, etc., etc., etc.
Still, I like the idea of inflated wings, but realize it is a very old idea. They had inflatable airplanes like 50 years ago - I think it was Goodyear again if memory serves, maybe another tire company. Built for the military, it never caught on.
Sometimes all this “What about this, what about that?” type of brainstorming reminds me of people sitting around trying to figure out how to turn gambling in Las Vegas into a legitimate investment strategy over a few beers.
I like the general concept of inflated aerofoils, but see problems in scaling up to the required size & controlling the angle of attack on large units as well as the life expectancy for such flexible materials?
Was wondering about this too…a “circular schooner”??..also about advantages of generating at a very slowly revolving central hub vs a number of water turbines at the circumference. Cable rather than rigid mooring would, I presume, allow exploitation of much deeper waters than current offshore windfarms…
Liked your idea…not sure if it goes in an AWES forum, but then again, most of the other concepts don’t seem to be flying very well! Was toying with something like that myself for a while…originally an oversized Darrieus turbine cut in half…a bit unrealistic on reflection - so something more like a “circular schooner”. Not sure about the flywheel aspect or how crucial that is…my hunch is that if one is looking towards a seriously sustainable future one will need to have enough pumped storage and hydrolysis plant (and grid interconnection) to mop the power surges. Also wonder if optimising angle of attack is as important as minimising complexity and having a system that can deform passively to survive extreme weather. Was thinking of something a bit more compact…and virtually all inflatable (tensairity) - I would imagine that would scale more easily towards the fraction of GW level. Perhaps the vulnerable fabric covers (esp leading edges) could be removed for repair/replacement without dismantling the air bladders. Also wondered about generating via water turbines at the circumference rather than via a very slowly revolving central hub.
To get a good TSR ( region of 3 for the giant VAWT ) for the very large MW scale ( significant fraction of GW), the apparent wind speed varies between 22 & 44 m/s at the design wind speed of 11 m/s. The aerofoils are very large and the forces on these aerofoils can be very large. The base on which each individual aerofoil is mounted, must be able to prevent it from heeling over, unless it is loaded above a designed level of force. If the AOA is controlled, extreme forces can be avoided and as rotation of an aerofoil is a requirement for safety reasons it makes sense to use that capability to optimise the lift force available from an aerofoil. I have added posts to the “maxwindpower” site showing the option of a fixed aerofoil that is designed to heel. This also has the potential of variable geometry. An alternative method of the aerodynamic balance for AOA control is also added.
I like the idea of a flying VAWT but I do not think that the aerofoils would remain vertical even if the top of the aerofoils were filled with hydrogen.
I totally agree that all renewable sources need some back up such as pumped hydro. ( This could be coastal with the sea being the lower reservoir.) Hydrogen may well play an increasing role for heating and transport and is also a good energy store for renewable energy.
The original patent application refers to a floating dam surrounding the unit and supporting generators driven by the flow that is created. From Couette flow analysis it is apparent that such turbines would need to be quite close to the main system, and would not extract energy as efficiently as a large diameter hub, but they could be an optional extra.
A note on the flywheel aspect:
By feathering aerofoils wind turbines protect themselves from over speed.
The alternative which only applies when massive flywheels are possible is to reduce the amount of feathering to maintain the generator at full capacity but allow the system to speed up, within limits, storing excess energy kinetically. GWHs can be stored which can be used to supplement the energy from lighter winds to even out the generators capacity. This could boost the annual production by as much as 25%, resulting in a energy cost reduction and lifetime CO2 emission per KWH reduction of 20%. This brings the CO2 emissions rate below any other system down to 11.4% of that of SOLAR.
Hi Guy M: Every time I hear about hydrogen as “a good source of energy storage” I wonder how anyone could presume that is true.
Generator to turn wind energy into electricity: 90% efficient
Electrolysis: 50% efficient
Compression or Liquefaction: requires 50% of the energy content in the hydrogen (50% efficient)
Burning in an internal combustion engine: 30% efficient
“Burning” in a fuel cell: 50% efficient
Generator to turn mechanical power back to electricity: 90% efficient
Can you please outline for me a scenario where hydrogen could be even a reasonable means of energy storage? And can you please provide the arithmetic describing the total compounded efficiency including all the steps required to complete the full cycle from energy => hydrogen (including storage) => energy?
(Remember, batteries are what, maybe 90% efficient from energy-in to energy-out?)
Good energy source from the perspective of the capability of being clean for processes that require heat such steel manufacture or long distance travel not in absolute terms. Solar is considered good yet it was not long ago that panels only returned 15% and they still decrease by about 0.5% for every degree that they are above 25C. I agree battery technology is more efficient but it is not problem free.
I remember a research project where they took a 10 kW wind turbine (just like the one that powers this place), and used it for a hydrogen energy storage project. It went something like this: They lost about half the energy in the electrolysis stage. Then they lost maybe another 50% compressing the hydrogen, bringing the losses up to a cumulative 75% of the energy thrown away, so 25% left. Then they had to turn what was left back into electricity, and so however they did that, I don’t remember if it was a fuel cell or a piston engine burning the hydrogen, but that took them down to like 10% of the original energy. But I seem to recall a total figure of something like 5% total storage efficiency. If they included the inefficiency of the turbine itself, they were keeping something like 2 or 3 percent of the original power that was in the wind. In other words, it proved basically useless. If someone showed you a battery that returned even 10% of the energy put in, you’d still be more concerned with the 90% of the energy lost. I could see hydrogen maybe for heating, if you had a way to store it without having to compress it much, like a cave, but you’d still be losing most of the energy, so overall I just don’t see how so much excitement is “generated” by hydrogen. Elon Musk spares no words in dismissing hydrogen as energy storage for cars at least. What I’ve noticed is certain “scientific-sounding” technologies enjoy an automatic “nerd appeal” where people who remember their 3rd-grade science lessons bask in that “superior knowledge” that electricity CAN split water, never exploring the subject beyond that 3rd grade basic level, never bothering to consider any further details. They are just fans of science, so anything that sounds “scientific” is an automatic slam-dunk winner in their minds. The same phenomenon occurs with photosynthesis at something like 1% efficiency, the “greenhouse effect”, vertical-axis turbines that “can accept wind from any direction” but somehow never quite pan out. All are examples of “single-factor analysis” where only a single factor is considered, to the exclusion of all further considerations, whereas the true situation involves a myriad of interrelated factors. 
I would not debate the efficiency of hydrogen systems as it not am area that I have studied, but there seems to be a lot of funds going into it for aircraft and steel has been produced using it. The only comment I have regarding it is that, I favour any system that has a lower overall lifetime CO2 footprint regardless of its overall efficiency.
With regard to VAWTs: There are a myriad of factors and as a result there are VAWTs & VAWTs.
Moving away from traditional design to enable extremely large diameters results in:
Slow changes in the direction of the apparent wind to each aerofoil, enabling adjustment of pitch by aerodynamic balance. This also allows feathering and safeguards the system from extreme winds.
Safe from the potential damage from extreme weather makes such large units possible.
Pitch control increases the power output of the turbine and has been demonstrated to do so.
Large diameters enable large chords, which increases the Reynolds number. This increases the Coefficient of Lift & decreases the Coefficient of Drag for a particular wind speed, resulting in greater torque per aerofoil surface area.
In a normal wind farm turbines are set around 8 their diameter apart, Applying a diameter to height ratio of 8+ for the large VAWT enables separate computation of the output from an aerofoil in multiple windward and leeward airflows. ( say 10 degree segments )
Consideration of chord sizes and number of aerofoils and pitch can ensure that the Betz limit is not breached within these airflows , but optimise power output at the design wind speed and Tip Speed Ratio.
Because the Betz limit applies to a single plane the power output per projected area of a giant VAWT can be much greater than that of a HAWT.
It is not possible to support aerofoils on radial arms at such large diameters, but it is possible to support them on a giant rotating flywheel. This then enables energy storage kinetically to capture some of the excess energy from stronger winds to supplement the power of lighter winds, which is feature that no other wind turbine has.
It’s an interesting design. Worth some study.
However I suspect your proof won’t be easy to present.
Extraordinary claims require extraordinary evidence.
It’s going to take a lot more than just transferring an 8x from HAWT
Seems right now H2 only makes economic sense when combining energy+natural gas to make the H2 gas, then sell it to subsidized «green» industry dealing with H2 use.
Qblade is simulation software ( freely available) that is very useful ( & recommended to me by Sandia National Laboratories ) Pity it does not allow for pitching of the aerofoils, but at least it enables a simulation for minimum power output and provides the aerodynamic coefficients that can be input into spread sheets to match apparent wind velocities and angles of attack… but not easy !
Yes this explains the hydrogen hype. It sounds “scientific” so why pay attention to any pesky details. A good story attracts money. Investors often take someone else’s word that it is “a good idea”. What you end up with is what happened to the old Soviet Union - projects pursued because the “sounded good” even if they made no economic sense. “Single-factor analysis” is the problem. It’s like “My girlfriend will really like this flower I will pick for her” except you will fall off a cliff to reach it.
Yes there are vertical-axis turbines and there are vertical-axis turbines: the two types are “former” and “proposed”. What you seldom if ever see is “a vertical-axis turbine”… And even more rare is “a WORKING vertical-axis turbine”. People always dream, and I’m one of them, but you could also dream about running across a lake of quicksand, until you got partway through it. For some reason, people like to dream big, while never building a proof of concept smaller model first. Yes things work differently at different scales, but usually “We have to make it HUGE” is just an excuse for endless fantasy while never building something.
So if we are to believe one of the flagship gurus of wind energy can strike gold twice…
Henrik Stiesdal and his company https://www.stiesdal.com have developed a new H2 generation process to compliment offshore wind.
And it seems to be making them money at least
Asia’s richest man to build gigafactory to mass-produce Stiesdal’s new low-cost hydrogen electrolyser | H2-CCS Network
Using aerodynamic balance to control AOA on a VAWT : A model has been made that demonstrates the general concept. It is also apparent that as the scale is increased the rate of change of apparent wind decreases making it easier to achieve continuous pitch control with aerodynamic balance.
VAWTs of existing design can not be scaled up greatly due to them requiring radial arms on which to support the aerofoils. Removing that requirement changes things dramatically. The concept of floating the structure needs to be applied to large scale because the shear rate in the liquid needs to be minimised. To bring the shear rate down to the region of 0.5 /s needs water depth of 2 x (Tip speed ) under the structure and a similar clearance on the OD. So with a tip speed of 33 m/s, depths and clearance of 66 m is desired, making models a little impractical.
They’ve been saying wind turbines can’t get much larger since the early days of windfarms in the 1980’s, similar to petroleum where we’ve been at “peak oil” and “about to run out” since the first oil well in Pennsylvania.
Similarly, people have attempted to “rescue” the vertical-axis concept from the early days, usually adding blade pitching which requires response to the wind direction (aim), and quite often citing the need to build bigger than ever seen before as a requirement. Maybe someday it will turn out to be true, but it’s also possible that it is just a design direction that attracts people with imagination and big thinking but without comprehensive analysis that would reveal problematic aspects. The history of wind energy wannabe breakthroughs commonly brings out “All-ya-gotta-do-is” type thinking, where a seemingly-simple concept is promoted without sufficient details to have a working model, and without sufficient analysis to say whether it would use too much material, be unreliable, break, make less power than imagined, etc. Citing the need to start out building a huge prototype for the idea to work is common - sometimes maybe true, sometimes maybe not.
You are right and that causes a massive dilemma undermining confidence, so I analysed why existing VAWTs fail or are unlikely to be able to be scaled up, then look at alternatives. Posts have been added to the site to reflect alternates / development of the concept.
Wind has a lifetime CO2 emissions rate of 14.2% of that of solar. It is estimated that the concept could reduce that by 20% down to 11.4 % . If there is a way of producing power at a lower emissions rate then we should be concentrating on that and if not it needs testing.
It’s not that complicated. I like to start with a Planters Peanut can, about as tall as it is wide, to illustrate swept area vs intercepted area. The plastic lid of the peanut can represents a regular horizontal-axis turbine rotor, aimed into the wind. Note the swept area (area the blades “sweep”) = the intercepted area of the turbine. Now take the rest of the cylindrical peanut can as representing a vertical-axis machine. Note that the swept area = 3.14 x the intercepted area. Wow that is a huge difference. So a vertical-axis turbine requires sweeping pi x its intercepted area. Right away you could say it will cost 3.14 x as much for the same power. But it gets worse: The tip speed ratio is 4 instead of 6, so at a slower RPM you need either 1.5 times more gearing, or a generator twice as large, to make the same power. But it still gets worse: The Vertical-axis machine is somewhat less efficient, so even with all that extra material, you STILL make less power per unit intercepted area. But it still gets worse: The vertical blades experience reversing aerodynamic forces twice per rotation, so they must be made far stronger than regular blades that have a more steady mechanical loading. But it gets worse again: The centrifugal force on regular blades tends to hold them in position, and not bend the blades, whereas centrifugal forces tend to bend vertical-axis blades so the blades must either be bent into a troposkein curve, or be built MUCH stronger to hold their shape against centrifugal force. Around here we have hundreds of wind powered homes and ranches, all using horizontal-axis turbines. We did have one (1) vertical-axis turbine powering a home about a mile South of our ranch, very sturdily built, at a much lower height (typical), and it broke within a year, and was dismantled (also typical). No matter how strong you try to build a vertical-axis machine, it will break. Try to find a single vertical-axis turbine running anywhere in the world with a happy owner. I don’t know of one. The story has been consistent for as long as I am aware. 
You are correct in pointing out that a VAWT is different to a HAWT. The VAWT aerofoils move more pro rata to the airflow cross section but they also pass through the air flow twice. This is a little like having 2 tubines but the downstream airflow has a lower velocity than the upstream airflow. Note this only really applies to VAWTs with a large diameter to height ratio. On a HAWT the aerofoils are subject to gravity bending them in alternate directions as they rotate. In a VAWT the load changes due to aerodynamic load. Traditional VAWTs do not have stays onto the aerofoils. This is an important feature in the concept. Centrifugal force is an issue for traditional VAWTs. It is not an issue for very large diameter VAWTs because even at a reasonable TSR the rotational speed will be low. ( much lower than a HAWT.) Referring to power: Power = force x Speed. The force on the aerofoil varies along the length of a HAWT blade and the speed is proportional to the radius at that point. Ignoring end effects the force along a VAWT blade can be considered constant and the speed is constant, but the force varies with rotational position due to changing angles of the apparent wind to the tangential velocity. Note limitations of both HAWTs & traditional VAWTs are mentioned on the “maxwindpower” site.