Patent:
The Bendix patent does not mention a belt drive which is included in the drawing. The belt drive transfers the weight of the generator and gear reducer from the top to the base. In addition, different size drive and driven pulleys eliminates the need for a gear reducer. This weight redistribution might be a key factor in increasing the height of the system.
It doesnt make sense for me to discuss this because this seems like a really obvious thing and why arent Siemens, Vestas and GE already doing something like this? My guess is they have their reasons
I would like to know the expert opinion of @dougselsam on this wind turbine and its two main features (tower concept, belt drive transmission), expecting something rather not quite positive and/or new.
I like the idea. I’d like to know more about it so I’ll brainstorm some ideas on why I like it and why I think it is also relevant to an AWE developer.
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The promise of AWE is that it (a) uses less materials and (b) can reach higher altitudes than regular wind. This idea has the same promise. Only there’s less risk of it crashing to the ground and it uses more existing technology so it is relatively de-risked. It looks like a mid-point between the two to me.
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It uses some of the same technology as AWE: a long rope or belt drive (possibly exposed to the elements), belt inspection, a rotating base, and probably more. And it also bases those ideas on existing technology or analogies that we can study or use in our own thinking, e.g:
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The tower is another concept for a ground station.
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“My guess is they have their reasons” What reasons do they have? What strong points does a regular wind turbine have over this, some of those it will likely then also have over AWE, excluding that it is a more mature product? You want to compete with regular wind and with this idea, so know what you’re competing against.
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It looks like a nice competitor in the niche energy markets that AWE is also targeting. You can write a business plan for a possibly smaller version of it for those markets and compare it to your own to better understand its weaknesses and strengths and your own.
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Re (4): but what potential advantages this has over regular wind and AWE I think is more interesting. How high can it go economically and what kind of blade or AWES can it support?
From the patent:
That would be a plus. You don’t want to be the first to do something, you’re much more likely to fail.
Your approach to seeking outlets from AWE towards current wind energy seems positive to me. I have a similar approach which I have outlined in several posts of which Slow Chat - #51 by PierreB, Slow Chat - #53 by PierreB, Slow Chat - #55 by PierreB : using @Massimo KiteGen carousel, replacing kites with vertical blades in order to achieve scalability in any dimensions towards a better power / space use ratio, towards a wind plant being able to begin to compete with a gas plant, avoiding the still difficult control of the kites, knowing also that in offshore conditions the wind gradient is low, like the expected benefit of high altitude winds. I discussed some similar projects (more power, less material, less space use) next to the forum.
See above, and also rotating reel transmission although it seems it failed for an AWE use.
Concerning the Bendix invention, the path is already well paved. Even if some aspects could be positive, this will not fundamentally change the situation: “eight megawatts (MW)” is a value already commonly achieved by HAWTs.
Could he not get anyone interested in testing it?
Scandalous how govt R&D demands instant profit and corporate R&D is outsourced to pay zero…
Surely it wouldn’t be too hard to trial somewhere between 1 - 10kW to get performance data… It’s only taken me 10 years to find sponsorship for a 10kW trial project… By the time I’m 100…
Thanks Pierre:
There is a lot to like about this idea, although I do not see a proper triangle-based strut arrangement going up each side of the tower in the drawings. That shows a lack of simple engineering knowledge. Maybe I missed something…
I also agree that the groundgen/belt drive feature does share commonality with AWE design goals.
However…
There has always been a small but steady drumbeat from maverick thinkers wanting to place the generator at the tower base, rather than at the top. Typical ways to do this include:
- substituting a hydraulic pump at the top, driving a hydraulic motor at the base, which spins a generator, and;
- a vertical driveshaft to bring power down to spin a generator at ground level.
In the first case I always ask whether the weight of a hydraulic pump is less than the weight of a generator, and is the extra cost and inefficiency (losses) of going from shaft rotation, to hydraulic pressure, back to shaft rotation, worth whatever actual advantages are gained by placing the generator at ground level. (?)
This is the first time I’ve heard the reason for a groundgen being fire prevention, saying it is easier to fight a fire at ground level, so keep the generator down where we can put the fire out more easily. Hmmmm…
Usually, the stated reason for placing the generator at ground level is to relieve the tower of having to support so much weight.
But then again, if your tower has to withstand the wind-thrust forces of a 1/8th-mile-across rotor, wouldn’t it already be strong enough to carry the generator’s weight?
Might the tensile force on a drive belt approach the weight of a generator anyway?
And what other problems might emerge from adding a 1/8th mile-long belt drive? For example, losing the ability to load the rotor if the belt fails?
I can see how a rotating tower with the windward side being vertical could reduce the possibility of tower-strikes. But a rotating tower makes aiming the turbine more complicated - now you have a larger footprint and more complicated tower-base infrastructure. And what if the wind reverses faster than the tower can rotate, if, for example, a cyclonic wind event such as a tornado or dust-devil strikes? The “rear” legs and ground anchoring might have to function in tension, so how do you neatly accomplish holding down the two slanted tower legs to ground level if the wind reverses?
Let’s also remember that “groundgen” is also a commonly-stated rationalization for vertical-axis turbines, which have never panned out in real life.
Also: Many windfarms still have old Vestas turbines on three-sided lattice towers, but the industry has transitioned to tubular towers. One reason is aesthetics - less visual clutter. Also, technicians can climb tubular towers “indoors” rather than being exposed to the elements. Not sure whether there are structural advantages too.
Would going back to 3-sided lattice towers be advisable for larger turbines? Seems possible, but I don’t know the answer.
I do agree with some aspects of this idea, but then again, it does have a few typical “professor crackpot” aspects to it.
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I particularily like the good point you are making here: maybe the tower is strong enough to hold the gravitational forces when the aerodynamic forces are so huge anyways. Why use a belt when conductive wires are so amazing. Seems we fall back to this discussion about how to transfer power and in which form it should take. I believe strongly that electrical energy as soon as possible and then use wiring is the correct answer for 99% of designs. And people are not really paying anymore to lift water out of their well.
Anyways, another reason that high towers like this may become difficult to build is that such long towers require very high stiffness to avoid oscillations to occur. This is an advantage of AWE, as the tower (tether) is basically massless
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Blockquote
A tensile force at the center of the column tends to strengthen the Structure. A single weight at the top of the structure tends to destabilize it.
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Off-topic, but let’s say you had these blades ready, or even longer ones: https://sumrwind.com/
Having the option of using a rotating tower would make your job easier I think. You could make your tower teardrop shaped, reducing drag by an order of magnitude over a cylinder and perhaps acting as a vane. You could make it much longer than it is wide, perhaps supported by guy wires on the narrow side, making it very strong in the direction you want with much less material usage and tower drag. That would also for example allow you to increase the solidity of your rotor, reducing the tip speed and extending the life of your blades, and making them easier to produce due to the reduced requirements on them.
I like the belt drive idea for its applicability to AWE but transmitting rotation over a few hundred meters with high efficiency is a solved problem I think. As are oscillations: tuned mass damper
Windy Skies: interesting for you to note “off-topic”, however I think maybe you might want to look at your own postings, which, if memory serves, are often themselves completely off-topic - just stuff you find “interesting” - things that could barely be said applicable in any way to wind energy at all, let alone AWE per se. Putting one’s head in the sand with regard to what has been learned in real wind energy has not proven to be very productive when developing new wind energy solutions.
Anyway, those of us who have been in wind energy for decades have been hearing about two-bladed downwind rotors forever. There have been lots of them over the years, and very few, if any, still turning today. One more case of “The song remains the same”.
I remember one company called “The Wind Turbine Company” This was when I was kind of new, and would go to wind energy “conferences”, mistakenly thinking they were particularly significant. At one, there was a guy from “The Wind Turbine Company”, tall, good-looking, wearing a nice business suit. My impression at the time was that “The Wind Turbine Company” was a pretty confident name. I assumed they had their act together and seemed to be positioning themselves to take over the industry.
Like SO MANY wannabe wind turbine designers, they would promote their vision for a 2-bladed downwind design that would supposedly allow larger-than-current-at-that-time size turbines.
Because of the name, their claims, and the guy I saw who seemed so polished as a “businessman”, I wondered if “this time it was for real” or just more wannabe, flash-in-the-pan fluff that would not work as advertised.
You have to realize, real wind turbine designers have always been aware of two-bladed downwind designs. Using fewer blades costs less, and the resulting faster rotation allows a smaller generator and/or less gearing (but with more noise).
But the tower-shadow issue is always a factor. Not too long after my experience being in the hallowed presence of “The Wind Turbine Company”, I heard news of their too-large prototype self-destructing near Lancaster, California. I think it was the first time they had tried to run it. Turned out it was near the home and shop facility of a friend of mine who manufactured and sold small wind turbines. He told me the exploding turbine was in view of his house, and had made a huge “bang” when it blew up. I don’t remember if it lost a blade, had a tower-strike or what, but I think my friend said one of the blades ended up stuck into the ground.
“Segmented blades” is another perennial “talking point”, endlessly postulated, never realized. Yes, of course, blades would be easier to ship in sections. So far it has all been a lot of talk, and like so many wannabe wind energy “innovations” it’s often kids and ladies who manage to qualify for government grants to show all the real designers how things “should be done”, but so far, none of the projects has ever panned out. Most such “projects” never even get completed. I mean, seriously, just take a look at the personnel on the sumwind video - do they really look like they know what they are doing?
The project in the link mentions a “12-story tower”. Sounds impressive til you realize that is only 120 feet tall, like the tower in my backyard with a 10 kW turbine on it. I will say though, that it IS better to experiment at a smaller scale, where the inevitable failures do not kill the whole company, as happened with “The Wind Turbine Company”.
Aerodynamically-shaped towers have been mentioned over the years, especially when it comes to downwind rotors. Also fairings that rotate, rather than rotating the whole tower. The one proven way to use two-bladed downwind rotors is one of my inventions: The SuperTwin™ concept:
I found even placing a rotor at one full rotor-radius from the tower entails tower-shadow issues, which can cause turbine oscillation, and eventually had to modify my designs to accommodate that factor. The solution also resulted in better overspeed protection. It’s sometimes only after you have several versions of a system running in many locations that you can even properly identify problems, let alone solve them. 
Still, the natural stability and more manageable speeds of a 3-bladed rotor predominate in the industry.
As for your comment: “That would also for example allow you to increase the solidity of your rotor, reducing the tip speed and extending the life of your blades, and making them easier to produce due to the reduced requirements on them.”
I hate to break the news, but optimal rotor solidity was worked out decades ago. Increasing rotor solidity is not where the industry is headed, but rather the low solidity is what makes wind energy economical and efficient. Slower, high-solidity rotors are less efficient at extracting energy from the wind. I won’t go into exactly why, since I like to keep a few of the secrets to myself, but there is a reason turbines are the way they are in wind energy, and it’s usually (I must emphasize, usually) not because of some simple variation that nobody thought of.
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