• The blade and cross cable system eliminates or reduces all problems associated with previous Vertical Axis Wind turbines including reduced vibrations, torque ripple and premature blade failure. The power output is improved, especially in low winds, by using an advanced blade profile and by building a rotor with a larger swept area. This is practical because the blade and cable system is light in weight and therefore relatively inexpensive. The ½ cost analysis includes this larger swept area.
• The tower at the bottom of the rotor is short but the equator of the rotor, on megawatt machines, is as high or higher than the hubs of conventional turbines, therefore, taking advantage of higher wind speeds that occur at higher elevations.
• All of the mechanical and electrical components are at ground level. This makes it easier to erect and also reduces maintenance costs and also makes it a more practical vertical axis wind turbine for residential areas.
• A yaw system is not required because this turbine accepts wind from all directions.
• The blades do not need to be pitched, which eliminates the need for the large diameter slewing bearings, retainers and hydraulic components. The blade speed and power output is controlled by aerodynamic stall.
• According to Dr. John Dabiri at Stanford University, counter rotating Vertical Axis Wind Turbines can be spaced closer together than conventional Horizontal Axis Wind Turbines https://arxiv.org/pdf/1010.3656.pdf. This is advantageous because most high wind speed sites are already occupied by widely spaced conventional wind turbines.
• The blades on the prototypes are made from aluminum, which are extruded at relatively low costs. However, since the blades experience only small deflections, they could be made from a wide range of materials or a combination of materials. Conventional wind turbine blades have large deflections, therefore, their material selection is limited.
• The blade profile is constant from one end to the other. Manufacturing this blade is much easier than manufacturing the conventional wind turbine blade, which has a profile that changes in width and curvature along its entire length.
• The blades can be made in sections and assembled like tent poles. This is possible because the blades are always in compression, unlike all other wind turbine blades that change from tension to compression through each cycle. The blade sections are easy to transport and assemble.
I think you’ve heard of Dr. Dabiri before, and also VAWT . That said if we keep talking about AWES, then why not VAWT? One of the points of the last posts is the higher density assumption for a VAWT farm: maybe some deductions could be drawn for AWE …
Hi Pierre: All I can say is:
Blah blah blah blah blah - yup heard it all before as we know. People in wind energy know better when they see “research” such as Dabiri’s. Endless attempts to “rescue” bad wind turbine designs. It is academic beard-stroking versus practical experience. One demands results, the other merely seeks additional funding. Always an excuse. Why are vertical-axis turbines never placed on a tall tower? Why does a Dabiri talk of placing smaller vertical-axis turbines between regular turbines at a windfarm, without comparing his concept to placing small horizontal-axis turbines between existing large turbines at a windfarm? To me it is one more case of “grasping at straws” to try and “rescue” long-disproven or at least ill-advised configurations. A shell-game to dupe people who refuse to think it through. It gets worse - there are still crackpots promoting (200% solidity!) Savonius turbines out there.
I sat with the founders of Kleiner Perkins trying to explain why their “Flowdesign” (later called “Ogin”) turbines with a funnel would not work out. They maintained “This time it’s different” because their particular “Professor Crackpot” told them their new version of the old bad design would suddenly be better than the state-of-the-art, due to some minor contours added to the inside of their funnel.
I tried to point out that the reason large-scale wind energy was even viable was the low solidity of the rotor, which required far less material engineered to withstand a 100 mph+ wind, and how could they realistically plan to build giant 100% solidity funnels around utility-scale wind turbines(?!?!?!), and what would they make them from(?!?!?!?!) and how much material might it take(?!?!?!?!) and how much might these giant funnels weigh(?!?!?!?), how much might they cost(?!?!?!?!?), how could they possibly support such monstrosities while maintaining the ability to aim(?!?!?!?!?). They have no answer except Professor Crackpot said some added swirly contours inside the funnels would be so great that nothing else (normal facts) would matter.
You can say the same for hydrogen as energy storage or as a fuel. Compared to batteries that give back 90% of the energy put in, hydrogen loses so much during electrolysis, compression or liquification, and recovery, that there is literally almost no energy returned at the end, but that doesn’t stop people from saying it is the answer. Elon Musk begs to differ. Seems like an emotional derangement syndrome where facts just don’t matter, while the lemmings run toward the cliff. A big part of it is if investors don’t bother to understand what they are investing in, there is unlimited funding available from people who know accounting but not science or engineering. Same shizzle, different day - the song remains the same!
Table 1. Comparison of VAWT and HAWT power density. The power density is calculated as
the turbine rated power divided by the area of the circular footprint swept by the turbine rotor
blades when rotated in yaw by 360 degrees.
Turbine Type Rated Power (MW) Rotor Diameter (m) Power Density (W/m2)
VAWT 0.0012 1.2 1061
HAWT 2.5 100 318
HAWT 3.0 112 304
This is from the reference cited:
“Whereas modern wind farms consisting of HAWTs produce 2 to 3 watts of power per square meter of land area, these field tests indicate that power densities an order of magnitude greater can potentially be achieved by arranging VAWTs in layouts that enable them to extract energy from adjacent wakes and from above the wind farm.”
Pierre, in wind energy, there has never been a shortage of clueless people who spew never-ending nonsense promoting “alternative” designs for wind turbines. There is only so much power going through a given area or volume, and extracting any of it slows the wind, clogging the entire volume or area with dead air, causing the wind to go around rather than through that volume or area, making further extraction more difficult. I’d say if this guy were accurate, you’d definitely see windfarms using his concept by now, since any developer would obviously jump at the chance to get 10 times the output from the same land area.
Not sure about “table 1” but I’ve never heard of anyone calculating power density in this manner that “appears” to favor vertical-axis turbines. Whacky stuff.
Wind energy is a brutal sport that quickly determines winners and losers by destroying the losers, either physically, or financially.
As I’ve pointed out many times, wind energy is a magnet for crackpots, (and AWE is a neodymium super-magnet) since the wind is invisible, so people can imagine it doing whatever they wish, except their “wish” is seldom accurate or pertinent.
I really regretted posting on this topic the first time after I looked up when I was done and found I had wasted something like 45 minutes trying to explain, once again, the folly of Dabiri or anyone else promoting inaccurate information based on half-truths. He actually makes little-to-no sense whatsoever, and I doubt if you can find any person in the actual wind energy industry who takes him the least bit seriously. Who is installing his BS today, anyone? Why not, because he’s so smart and they are so dumb? I’m sorry but after the Altaeros charade, MIT is losing credibility with me. Good talkers can make almost anything sound reasonable to people who don’t know any better, but the acid test is whether someone can separate fact from fantasy and real useful levels of economic output from fictional contrivances that only sound good “on-paper” to inexperienced newbies who don’t know any better and are not adept at applying simple logic to outrageous statements and exaggerated claims.
A difficult secondary use (farming) could result from a high density of small VAWT.
In the other hand perhaps VAWT could be interesting if some structural features are studied to reach scaling more than any HAWT while the implementation is facilitated, above all offshore.
Hi Pierre:
I would think farming under conventional windfarms would be fairly straightforward. I think farmers in the midwest already enjoy turbines in their fields as an additional “crop”. If anything, having a bunch of Dabiri vertical-axis turbines littering the ground below the regular turbines would prevent farming, rather than facilitating farming. As a wind inventor, of course I share your urge to leave no stone unturned, including vertical-axis designs of various sorts. Ideas for better designs need to be tried out, not just talked about in vague terms. Things can look really good on paper, but have major problems when actually built and run. That is why we do not see any vertical-axis machines in windfarms today.
The blades are made in pieces, and are joint using Crystic Crestomer 1152 PA, which is a carbon and glass fibers adhesive. The design, which is not applicable for HAWT, lowers the costs in manufacturing and transportation compared to a one-piece blade.
Below there is also an analysis of the potential of scaling for VAWT offshore:
I think that perhaps the rotary part of a giant VAWT could be a carousel, allowing to benefit from both higher speed for the generator, and a more resistant and stable rotary basis, as shown on the sketch below:
Hello Pierre: What you describe has long been one of my favorite pet configurations - agreed.
Wish I could build and run one of every idea that comes to my mind!
Still, let’s remember all of the inherent detractive aspects of VAWTs.
No matter how much we may imagine rescuing the concept, there are basic reasons why we seldom see one running. Higher cost, more material, lower efficiency, slower rotation, strong bending forces on the blades, reversing twice with every rotation, etc., etc., etc.
You know the drill. Still, those of us with “enquiring minds” can’t quite let go of possibilities! It is though, always funny to see the next PhD run through the gauntlet of promoting one more weak attempt to save the verticals, not comprehending any of these basic facts to start with.
So, why not HAWT arranged on a geodesic dome, reputed to be one of the most solid structures in relation to its weight? The dome rotates according to wind direction:
The objective is to overcome the distances imposed by separate units due to changes in wind direction, while also harnessing high altitude winds for HAWT settled in the top. A wind farm still takes up too much space.
Hi Pierre: The main forces on a blade stay fairly constant for a propeller-type rotor, hollow or not, compared to cross-axis reversing forces on a VAWT, which, added to the slower rotation requiring more blade surface, is why their blades can often require so much more material to accomplish the same energy extraction, depending on the exact design. Would-be designers can keep their head buried in the sand, or figure out why there are essentially near-zero working vertical-axis machines out there, compared to the vast multitude of regular machines.
Many such structures could be worth a try. There have been several multi-turbine support structures built and run in the past. Seems like conflicting resonant frequencies are the problem they end up having. Many windfarms are in predominantly unidirectional wind resources. The turbines are still spaced for best economic return. I think they place as many turbines as they can while still getting good performance. Overcrowding of turbines negatively affects performance by creating large volumes of stagnant air.
On the picture above, all wind turbines face the wind. There is no turbines downwind. So they can fill the space. There is an orientation system rotating the full rack.
On the dome, the wind turbines share the frontal airspace in a similar way. So according to a preliminary approach, there is no wind shadow on the wind turbines behind, a little like for SuperTurbine ™ where all rotors harness “fresh” wind. I think a dome could be easier to use than the rack above, above all concerning wind changes.
The problem with a geodesic support is that the turbines must be mounted on a cantilever arm to avoid hitting the dome. This problem gets worse towards the top of the dome where the cantilever is longer and wind forces are greater.
Perhaps by modifying the mesh, allowing the insertion of wind turbines. Indeed, if we install cantilever arms, we lose the possible structural advantage of the dome. Another problem is the wind shadow caused by the structure. That’s why I might come back to the VAWT dome (see above).
Pierre: true enough, there is a variation, but that is nothing compared to a vertical-axis turbine which undergoes a complete reversal of forces 2x per rotation, with the main forces being perpendicular to the blade, no less. OMG! “Hello, may I thpeak with Profethor Crackpot pleathe? Thir, we have an emergenthy!”
Doug: it is not for nothing that De la Cierva invented flapping hinges in order to solve the dissymmetry of lift, preventing the blades from breaking.
Concerning VAWT I think there is some possibility for giant installations (about 1000 meters diameter and more) lengthening the rotation time, such like the device on the sketch below:
The too low density in a farm of HAWT is a crucial problem. If giant VAWT are implementable the density issue can be solved, at least for offshore wind turbines: a single VAWT becomes like a farm of HAWT whose units are scattered over too large areas.
. That said if we keep talking about AWES, then why not VAWT? One of the points of the last posts is the higher density assumption for a VAWT farm: maybe some deductions could be drawn for AWE …
