# Slow Chat

Well Pierre, When I start to consider such structures, I note factors such as

1. How to support blades at a speed of 4 times the wind speed, so in a 30 mph wind, your blades are traveling at 120 MPH.
2. 4 G’s of centrifugal force, even at a 1-mile diameter
3. How big, How heavy? How to support against centrifugal force and the reversing wind force?
4. Blades only effective during portions of the travel
5. Possible shielding of downwind blade by upwind blades
6. suboptimal blade performance even at the most effective portions of the circle, due to no camber
7. Tunnels or bridges to get inside the circle?
Here are pictures of rows of turbines in Tehachapi:
Tehachapi Pass wind farm - Wikipedia
The rows are spaced apart enough to allow fresh wind to dilute the expanding, slow-moving wakes of the previous row.
I agree that a mega-large rotating structure sounds good in some ways, but someone would have to provide sufficient details of something workable. To just pick a few factors “out of the air”, without a complete analysis is how the “Professor Crackpots” of the world like to operate. But you can’t just pick out a few favorable aspects to consider - the whole picture must be examined. I like the “idea” of coming up with this “idea”, but at some point, we would need a complete “idea” to consider, not just an idea for an idea.

Hi Doug, I don’t tell that a giant VAWT carousel will work, but we can examine it.

Centrifugal force F = m v²/r where m is the moving mass, v is the tangential speed, r is the radius. When the radius is 10 times higher, centrifugal force is 10 times lesser. So a large diameter is a significant factor for a lower centrifugal force.

I think Tehachapi Pass wind farm is for predominant wind, allowing low spacing between the turbines in the same row. This is not possible for many other wind farms where all wind directions are more or less considered.

Pierre:
Yeah I was going to say, check my math.
I got 4.5 m/s^2 and too quickly thought 4.5 G’s (sounded a bit high at that size) - wrong - more like half a G, sorry about that. Thanks for the link to the calculator.

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Doug, I am examining your other observations: although they are relevant, I think some problems can be solved. I will try to detail later.

Pierre:
I’d surmise such a thing would “work”, Believe it or not, I spend a good amount of time thinking of such configurations myself. It’s what happens when you suffer from CSIS: (Can’t Stop Inventing Shit). Oh wait, I think my mommy said it should be “Can’t Stop Inventing STUFF”. (Can’t stop inventing FLUFF?) (Marshmallow Fluff?)
As I’ve always maintained, there are a myriad (million?) ways to extract SOME energy from the wind, at SOME cost. The idea is to do it less expensively than competing wind systems or energy sources in general. I mean, dude, riding a bicycle across the country will “work” but how many people want to bother? What about blindfolded with a guide dog? Maybe a tricycle? It could “work”… Competing with the airlines? Probably not.

Doug, the complete quote is:

If a giant VAWT carousel is feasible, the power/km² would increase drastically compared to a farm of HAWT whose unities are largely spaced due to wind change requirement.

Hi Pierre:
OK I was figuring for a carousel one (1) mile across (diameter). So you’ve got 3.14 miles of blades traveling in a circle. How many miles of blades are working at any moment? Maybe half of them? Many blades will be traveling upwind, downwind, etc. Then you have a circular mile of emptiness inside - how many rows of turbines could fit in that same area? How many turbines would fit in the unused corners of one square mile of land not taken up by the circle? Then also consider whatever physical structure it would take to support over 3 miles of blades traveling at 120 mph, and extract the power. It would be interesting to run some hypothetical numbers on power produced, material required, etc., and compare it to a square mile of regular windfarm.

The question is the frontal airspace as swept area. For a VAWT of one mile diameter with blades of 1/8 mile height (see the document I attached above), the swept area is one rectangle of 1 mile x 1/8 mile. But as such a diameter corresponds roughly to the distance of two rows in a HAWT farm in such a way that the second row is not too penalized by the wind shadow of the first row. The same for a VAWT when the diameter is huge. So the rectangle is roughly multiplied by two.

Knowing the coefficient of power of a VAWT is about 0.35-0.4 against 0.45-0.5 for a HAWT whatever the dimensions, you can calculate how many 15 MW HAWT you have to implement in order to achieve the power of a VAWT of one mile x 0.125 mile (and almost 2 times). Then you have to calculate the spacing requirement due to all wind direction possibility. The land use will be far higher.

I think @Massimo has well studied carousels of any dimensions, until GW range. I only propose replacing kites with vertical blades. Carousels could scale in any dimensions, not HAWT because of the tower, and the weight of the generator in altitude.

Hello Pierre:
I think you mean one mile x 0.125 miles. 1/8th of a mile = .125 miles.
I’d say let’s acknowledge the edges of the circle will probably not contribute much, if any, power, which may be one reason for the lower overall Cp of vertical-axis machines. The other reason might be the non-cambered blades which have to be designed to accept wind from both sides of the airfoils.
Regarding the “armchair-genius” link you provided:
Note the requirement for the “floating” blades to travel over 100 MPH in the water. That would sap a lot (all?) of the power, if it is even possible.
Anyway, have you calculated how many regular turbines it would take to achieve the same output as the mile-across-circle vertical-axis turbine?

Hi Doug, yes: I just corrected.

Yes, this is well known, so the whole calculation takes into account of the lower efficiency of VAWT.

On the description there is air cushion between the reservoir of water under the blade and the water of the sea. But there is no detail about how air cushion would work. I agree that this point is questionable but it concerns only an use of the carousel as flywheel, not the carousel by itself. Moreover the generator is settled in the center: so as the angular speed is very low, big gear would be required.

The solidity could be about .1 or .2. If it is .2, the whole blades would cover one mile X 0.125 mile/5. So it is sure that for an equal power this VAWT carousel would use far more material than HAWT. But in the same time it would use far less land/sea area, and likely less anchors.
Below is how a blade could be:

Yes whereas the solidity of HAWTs can be 0.02.
But I was not asking about rotor solidity. I was asking how many regular wind turbines it would take to equal the output of such a hypothetical, mile-wide, 1/8 mile tall, vertical-axis wind carousel turbine? I think you mentioned Haliad X from GE? How many of them to equal the 1 x .125 mile carousel?
By the way, I like that OceanBird ship design. Telescoping sails - seems like a nice idea!. If those sails were a wind turbine rotor, it would be a high-solidity, low efficiency water-pumper.

Yes, but only at the tip blade, and about 0.1 for the whole blade (there is more width and material close to the root). A VAWT can also achieve 0.1.

Very approximate calculation:
Swept area of 1 x .125 VAWT carousel: about 320,000 m²; power = about 80 MW (perhaps far more by taking account of the leeward row which is far enough from the upwind row, so the power of about 6.6 Haliad); Cp = 0.4; sea use = a square of 2.56 km², so density is 31 MW / km².
Swept area of Haliad: 38,000 m²; power = 12 MW; Cp = 0.5; density: less than one unity / km² due to the spacing requirement in all directions (due to wind changes in all directions) of more than 5 widths (rotor diameter 220 m), so about 10 MW / km².

Blades would be more narrow that the sails on the photo, and should be connected with cables in order to reinforce them.

OK I’m thinking it would be cheaper to install 7 or even 10 Haliads than to build such a 1-mile ring of blades standing 600 feet tall, traveling at over 100 MPH… What do you think?

Sure, but the question can be: you have only n km² for the complete installation.

And each time we double the diameter and the height of the blades (keeping the diameter/height ratio of about 8, allowing the leeward row to be more efficient, perhaps like the second row of a correctly spaced HAWT farm) the power is multiplied per 4…

Below is an article (see 1 about “extremely wide VAWT (a low rotor-aspect-ratio)”) from Peter Allen Sharp you well know:

Pierre: Wind Harverst International never got any traction with their vertical-axis designs. Peter Sharp, who also suffersfRom CSIS (can’t stop inventing shit) has a lot of interesting ideas, but like most armchair inventors, presents a partial picture, mostly mentioning hypothetical advantages. Unfortunately he does not build realistically well-developed prototypes, but, like Santos from the previous forum, more concentrates on simple, miniature, paper-and-string “talking-point-demo” projects that are easy to build, but only show a bare essence of a possibility for future more comprehensive development by someone more serious about, for example incorporating an actual generator, sufficient construction to withstand a real wind resource, overspeed control, etc. What you’re doing is just reciting the long list of “talking point-insistence” by vertical-axis advocates, who are never short of “why won’t anyone listen to me?” type “reasoning” but who can never come up with even a single house powered by their “highly-advanced”, “why won’t you listen to me” insistence on listing all the various brainstorming ideas they can come up with to “prove” the world is just not “getting it” with regard to why vertical-axis “are really” the answer. The same dynamic can be found in other fields, from architecture to engineering to economics, where there will always be someone insisting that the most disproven notions “are really” the “only” answer. At some point, the cartoon character of “Profethor Crackpot”, “thpraying thaliva ath he thpeakth”, cometh to mind - he ith not rethtricted to wind energy - he ith everywhere!. Look up “Mass MegaWatts” run by a friend of mine. Well-intentioned, and like Wind Harvest, good to know someone tried, but it just never went anywhere. :)))

Hi Doug: I try to see if some scheme can work. For example concerning Dabiri’s VAWT farm I already indicated (on the old forum) that even if the principle works, the multitude of small VAWT would be far more expensive than a regular farm of HAWT. Perhaps also you remember how I debunked the principle of active lift for VAWT as I pointed the incoherence of the sketches and the explains, beside the principle itself. Numerous schemes comprising VAWT inventions can be debunked on the paper. Hoping to gain a few percentages in order to approach HAWT efficiency is not a good idea.

On the other hand, the idea of ​​the carousel deserves (in my opinion) to be dug, because it affects a weak point of HAWT: the lack of scalability (what are 15 or 20 MW beside GW scale of gas or nuclear power plants?) combined with the low density per km².

And what do you think of the evolution of AWE?

Hi Pierre!
I must admit I do not remember what the term “actve lift” referred to in the context you mention.
I also agree with you that giant vertical-axis machines seem like a compelling possibility, but also play devil’s advocate when I see nobody looking at the downsides. Still, the concept does seem worthy of consideration and perhaps a few teams giving it an actual try rather than just talk-talk-talking about it.
AWE? I need to get back to more active status. So many unexplored possibilities!
Right now it seems to me most of the big-name, big-money players have eliminated themselves in a Darwinian sense, (they quietly go away) and the last (dying?) gasp in the current popular consciousness is kite-reeling, which always sounds so good, but is still not powering anyone’s home, as far as I know.
I guess everyone is now supposed to wait as these reeling systems go into “production” and get shipped to a small number of volunteer-guinea-pig “customers”. The numbers cited always sound tantalizing, but then we wake up and it was “just a dream”? Time will tell I guess, but we’ve been saying that for a decade now. We must remember, there are a million ways to get some energy from the wind at some cost, but is any given idea an actual reliable system capable of becoming an economic winner?

In the old forum: Digest (27143 to 27192) and Digest (27092 to 27142): a long discussion about “Active Lift Turbine VAWT” and “The gear which does not rotate”, ALT = Active Lift Turbine. It is not easy to found the whole discussion but there are some complete messages on these pages. The link for all old messages is Old Forum Archive Airborne Wind Energy AirborneWindEnergy AWES.

Beside it I think some concepts turn around VAWT carousel such like KiteGen carousel, but with kites. Also I mentioned and linked a study but it is mainly focused about how benefit from a flywheel effect, not the giant VAWT carousel by itself.

A possible secondary advantage would be the possibility of blades having the same (reversible as you point) profile on its whole height, allowing an easier building and the possibility to segment them in order to facilitate transport. But also some disadvantages can occur. Making deeper analysis and above all small then bigger prototypes would help to understand better if this can be a solution.

Regarding AWE in its current form I fear that time has already given its verdict. Now maybe some principles from AWE could help regular (ground-based) wind energy to progress.

OK Pierre I looked it up - yeah, yeah, active lift. I guess it means adjusting the blades of a vertical-axis wind turbine in real time as they transit a circular path - an old idea, and the typical attempt to do this involves adding a tail to the vertical-axis turbine so it can “know” the wind direction. Of course it could be accomplished by other means.

This is the first typical knee-jerk adjustment to try and “rescue” the vertical-axis concept. It’s like extolling the virtues of a two-wheel vehicle, but then adding more wheels to “stabilize” it. Like making a protein milkshake to lose weight, then adding lots of ice-cream at the last minute to make it taste good.

Interesting concept, but note how we are first drawn into exploring the vertical-axis space with individual aspects such as “doesn’t need to aim - responds to wind from any direction”.

But as the problems are pointed out, they change their tune: “Oh, well if you really want it to work well, we have to make it change its configuration in real time due to the wind direction.”

So you start out saying even though it spins slower, needs way more material, breaks down all the time, never emerges as a winner, but, its advantage is being simple and able to respond to wind from any direction without the need to aim, then the first thing they do is negate that single advantage - now it still has most of the bad features, but it gives up its single stated “good” feature - now it needs to “aim”.

Professor Crackpot tripping over his own feet? Maybe he left his brain at home that day.

Anyway, yes it does seem like continually aiming the blades for optimal power extraction at any point would be advantageous. Even the big horizontal-axis turbines adjust the pitch of the blades continuously.
But what I see is that addressing the weak points of vertical-axis turbines involves throwing away whatever stated redeeming (good) qualities originally used to convince anyone to try them in the first place.

Step 1) Use this design because of the simplicity.
Step 2) Throw away the simplicity so it “works better”.
Oh well, it is an interesting topic.