Hi again Pierre: Of course “everyone” knows about the variations on blades. Even the very large regular horizontal-axis machines face a pulsation of blade loading (wind speed) due to the wind gradient and their huge size. Low wind speeds at the lower heights at the bottom of the circle, high wind speeds at the top of the travel path. Even the wind direction can vary with height.
Now when you say “the too-low density in a farm of HAWT is a crucial problem”, well maybe you should get a job with a wind energy developer moving the turbines closer together, or adding smaller turbines in between. See if they will listen. Why choose long-disproven vertical-axis turbines though? Because Dabiri says so?
Let’s realize the reason for towers is to place turbines higher in the wind gradient. If we add smaller turbines below, it is equivalent in some ways to raising “ground level” to a higher height. Which is like lowering the tower height of the regular large turbines. Adding turbines below would slow the wind down there. The result might be to mix slower air into the wind the larger turbines receive, possibly negating any advantage to adding the smaller turbines. A large part of the wind energy industry involves “repowering” windfarms, which means plucking out the old, smaller turbines and replaciing them with modern larger turbines. I’ve never heard of a repowering effort that left the old, smaller turbines in place. Why might that be? I’ve wondered myself what harm it does to leave the old turbines in place. Probably a lot of it has to do with visual clutter, how many turbines they have a permit for, how difficult it would be to get approval for adding a higher number of turbines, etc. Then again they might have figured out that smaller turbines below would not add to total energy capture. Do current engineers and scientists have no idea what they are doing, and they should be tuned into our chat groups to get a clue from us smart people? Should they be hanging on Dabiri’s every misguided notion? Well, maybe. Or maybe windfarm developers do know their art fairly well, and it is Dabiri and our chat groups don’t really understand the subject matter very well. 
Doug, as soon as we speak about VAWT, you evoke the works of Dabiri by a sort of Pavlovian reflex. My previous messages are not about the arrangement of Dr. Dabiri but, among several things, about a large diameter carousel VAWT. For example if a 1000 meters diameter and 150 meters high VAWT is implementable, it would harness a frontal airspace of 150,000 m² (even perhaps almost two times as the leeward row is far enough from the first row) , by using less than 1 km² sea use. Spacing requirement means that in 1 km² only one or two 15,000 m² HAWT can be implemented.
According to the current state of the art wind energy cannot compete with fossil fuels or nuclear energy, because of their too low density, in addition to their intermittence. So we should examine some other possibilities. Yes, “the too low density in a farm of HAWT is a crucial problem.”
On the other hand if alpha and omega are in the relative success of wind farms as they exist, then we should stop all those innovations that have little or no market reality such as AWE and multi-rotor structures.
Well Pierre, you echo some Dabiri assumptions that I believe are questionable. The specific text I replied to was “The too low density in a farm of HAWT is a crucial problem.” Funny, I’ve never heard that before from any knowledgeable wind energy person, but Dabiri seems to agree. Like I mentioned, I am not aware of anyone in the wind energy industry taking Dabiri seriously.
This is reminiscent of some know-it-all with a PhD on the radio a few years ago who derisively claimed that most of the energy was obviously slipping through HAWT rotors due to the blade spacing. He obviously did not know the first thing about wind energy, yet believed he knew far better than actual turbine designers, with his naive, beginner-esque, first impression, 100% wrong “observation”, on the level of something a first-grader might say, before the basics of wind energy were explained to him.
Here’s another one for you. I’ve often mentioned this particular university project that forced air through a Savonius turbine in a wind tunnel, and published the favorable results.
https://www.researchgate.net/publication/228818185_Development_of_Optimum_Design_Configuration_and_Performance_for_Vertical_Axis_Wind_Turbine
Did he really improve the Savonius concept? Hard to say, but he could have doubled the unimpressive performance of a Savonius, and it would not matter - they would still be the worst performing type of turbine known.
While I point out the dismal track record of vertical-axis machines for the purpose of informing people who really are not well-educated in wind energy, that doesn’t mean I’m not also attracted to the same types of designs you point out, including giant vertical-axis machines. I’ve thought of most of them for years. Remember “Laddermill”? Just one more idea I originally thought of. With regard to offshore, you may remember I was recently granted two (2) patents that cover most designs for floating offshore wind installations. The popular “spar-buoy” floating wind turbine foundation is just one of the many floating designs being promoted, covered by my patents. The reason these patents were granted was because it was determined that I was indeed the original inventor of the single-turbine-on-a-buoy concept. So I’m pretty happy to see my original idea now changing the world, but I have further ideas, including many of the vertical-axis configurations we commonly read about, some of which you have mentioned.
Many people are protesting against the various impacts of wind turbines. The low density due to the need for spacing between units contributes to their scattering over very large areas. And it is difficult to conceive of a HAWT unit of the size of a small thermal power plant. On the other hand, configurations of giant VAWT carousels could perhaps allow it.
Well Pierre, When I start to consider such structures, I note factors such as
- 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.
- 4 G’s of centrifugal force, even at a 1-mile diameter
- How big, How heavy? How to support against centrifugal force and the reversing wind force?
- Blades only effective during portions of the travel
- Possible shielding of downwind blade by upwind blades
- suboptimal blade performance even at the most effective portions of the circle, due to no camber
- 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.
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:
https://www.oceanbirdwallenius.com/the-vessel/
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.
See also some comparisons on:
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?