[wingineer]

Wind turbine design engineer here:

There are several significant barriers to adoption that VAWTs face.

1. The wind resource is more powerful and more consistent higher off the ground. The hub heights of industry standard horizontal-axis wind turbines are reaching 135+ meters for the new generation of large offshore machines. These vertical axis machines are much lower to the ground.

2. Contrary to the claims of the authors in the Renewable Energy Paper (they say "The potential applications for VAWTs are endless, because the turbines are cheaper and easier to manufacture and maintain. "), vertical axis turbines have consistently had fatigue issues. There is an interesting history of the test-campaigns of vertical-axis machines at Sandia National Laboratories [1] that discusses this. In the 70s and 80s vertical machines were much more common than they are today.

3. It is a huge risk for an industry that is shipping proven technology to switch to a new paradigm that will require much more research and testing to work at scale. It's certainly possible and I find the possibility fascinating as a curious engineer. I would love to have a secure position developing VAWT tech or working on airborne wind machines (check out ground-based generator concepts to get an idea of where I think that will progress, not ill-conceived onboard generator kites like Makani).

The problem of wake blockage in large wind farms (and from adjacent farms to each other) is definitely significant though. The current "top" strategy is wake steering, where turbines at the front use their yaw drive to capture less power and allow for more power to reach the turbines in the rows following. [1]. The bleeding edge of this may be vertical wake steering, which can entrain high-energy wind from above the farm into the plant to capture more power [3].

[1] https://energy.sandia.gov/wp-content/gallery/uploads/SAND201... [2] https://www.nrel.gov/docs/fy17osti/68396.pdf [3] https://ieeexplore.ieee.org/document/7963037

[olau]

Regarding the risk - I don't think this characterization is doing the issue justice. It's really about decades of building up a manufacturing capacity with suppliers, etc. to get to a position where wind turbines are now competitive because of this manufacturing capacity.

For an alternative to develop, it is not enough that it is slightly better. And both turbines driven by kites and vertical turbines are known tech, with known problems. They are likely not slightly better. Early wind pioneers knew about vertical turbines. They have some nice properties. But also some not so nice ones.

And this paper does not study vertical vs. horizontal as far as I can tell from a cursory look. It studies what happens with vertical turbines in a small farm.

[wingineer]

Fair. I once was told by a senior NREL engineer that industrialization of a different concept than HAWTs would take over $1B in investment. Which is a lot in a low-margin, capital -intensive business like wind energy. And that number is probably on the low end.

Kites have the potential of much lower material costs to produce energy. If you have a pumping cycle kite, the "support structure" is the tether, compared to the tower and foundation required for a HAWT. The problems are indeed well known: 1. Tether material difficulties. 2. Need for self-launching 3. Airspace sharing problems at heights of kites 4. Controller design. This last one is what intrigues me personally.

The paper looks at vertical turbine arrangements, but the linked article about the paper starts with "The research suggests that the now-familiar sight of traditional propeller wind turbines may be eventually replaced by the sight of wind farms containing more compact and efficient vertical turbines." I had to respond to this rather wishful statement.

[algo_trader]

Do you have info/links on the current status of kite-wind-turbines ?

Obviously, they are unlikely to be ever competitive with current HAWT which is really sailing (pun!) along nicely.

But as a niche-player e.g. oil rigs, mobile power sources, etc, maybe not all is lost. What is their projects LCOE ?

EDIT: projected/promised $49/mwh

https://www.greentechmedia.com/articles/read/will-airborne-w...

[ncmncm]

I am interested in what has been done to study no-moving-parts wind power extraction.

Alvin Marks (who beat out Edwin Land for the polarized-sunglasses patent) filed a patent on this back in the '80s.

The idea is simple: you ionize air moving through your system, and the wind carries the ions away, accumulating a grid voltage vs. ground. The restoring current can do work. If your screen is on a kite, it can be very high up, to catch very high wind speed. It is very cheap to construct, with no mechanical parts at all; restoring current runs up (strictly speaking, down) the kitestring. Or, a screen could be stretched between upper parts of pairs of existing skyscrapers, or towers of a bridge, almost invisibly.

The trick is how to ionize air cheaply. Certain materials give up electrons to moving air spontaneously; you could have streamers of such materials, modified to be slightly conductive. Otherwise, you need some sort of charge pump to favor losing surface charge. Maybe a mist of water carries away the ions.

Measures of efficiency can be confusing. Ultimately, the measure that matters is W/$. If the installation is cheap enough to build and operate, percentage of available wind power extracted may be almost irrelevant. Stretched between existing structures, you might not want to extract much of the available energy anyway, because of the load it would place on the structure. But the next screen downwind could extract as much power, again.

[sterlind]

what materials give up their electrons to moving air spontaneously? are there tricks you can do with the (perhaps nano-) patterning of this material, like arrays of little needles? have any labs attempted this? it looks fun.

[ncmncm]

I'm sorry, I am not a materials scientist. You might find a list of stuff not to use when building an antenna tower.

[jacquesm]

The big problem is resonances. A VAWT has various modes of resonance that are very hard to engineer against due to some of their basic properties. The largest of these, the one at Cap Chat in Quebec ended up being scrapped after an embarrassingly short period of operation.

There are some VAWTs in the rockies that lived for more than a decade but they made really little power compared to the amount of money that went into them.

But they look nice and are deceptively simple on paper (one less parameter to deal with due to the fact that you don't need to steer them, and the generator stays at ground level). So likely people will keep trying but it almost certainly isn't going to move the needle in the longer term.

[hinkley]

If memory serves, the resonance problem with 3 blade turbines is when the blade passes in front of the pylon. But with the VAWT the blades instead pass into the shadow of every other blade, which is twice per revolution?

Does a VAWT behave better or worse in this regard with an even number of blades? Seems like with an even number multiple blades would occlude each other at the exact same time.

[jacquesm]

It is the tower occlusion that sets off the problematic resonance, which ends up eating the base bearings.

[bigiain]

There are a couple of (small, obviously academic/experimental) vertical axis wind turbines near me which both have helical blades. I wonder what the tradeoffs for that design are?

Here's a picture (not mine) one of them: https://www.flickr.com/photos/nicephotog/25044930672/

[hasmanean]

For very tall VAWTs in a grid, could you dampen the resonances by tying the tops of the masts together with guy wires?

[jacquesm]

That will make it worse, not better. You want to decouple as much as you can so you don't end up creating a giant resonant structure.

[jacquesm]

They're sexy toys, not turbines.

See also: Windtree and other scams.

[patall]

That reminds me of that recent finding that wind turbines would be a few percent more efficient if they turned anti clock-wise (at least on the northern hemisphere), but practically turbines in use today turn clock-wise. Sure, it should not be to much engineering to change that but still you need to adopt the entire manifacturing process to it.

[dividedbyzero]

Would you have a source for this? Really curious what might cause that.

[Spare_account]

I can't vouch for the sources, but here is some reading material:

https://wes.copernicus.org/articles/5/1623/2020/wes-5-1623-2...

[PDF] https://wes.copernicus.org/preprints/wes-2019-105/wes-2019-1...

https://www.economist.com/science-and-technology/2020/05/14/...

[Wohlf]

Interesting, so it's not the rotation direction of any individual turbine that matters but how the wake of turbines affect others around it.

[breischl]

Tangentially, I ran into the bladeless vortex concept recently (https://vortexbladeless.com/), do you have a take on that?

It seems like all your concerns/critiques from above would apply equally, but then I don't have any real expertise in the area.

[wingineer]

I think the bladeless vortex concept makes no sense. Here's why:

1. The surface area of the machine is small. Think of this as the area that can capture power from the wind. Due to the cylindrical shape this is way smaller than the rotor area of a HAWT or even a VAWT.

2. Vortex induced vibration [1] is a real phenomenon that can extract energy from a flow. However, to extract this energy, the natural frequency of the structure must synchronize with the vortex shedding frequency of the flow around the structure. This is called "lock-in". Since the wind is a highly variable resource, it will not consistently be in this "lock-in" range in real-world conditions. To give perspective on the norm for HAWTs, pitch control for the blades is used along with generator torque control to achieve power production from 3 m/s all the way to the maximum (cut-out) wind speed of ~25 m/s.

[1]https://en.wikipedia.org/wiki/Vortex-induced_vibration

[fho]

I guess you can "tune" the tower by adjusting a weight in the tower ... but I agree on the area issue.

[philistine]

Their website does scrolljacking that doesn't work on my browser. An idea is all appearances and no competence if they do that.

[pwnna]

Not a wind turbine design engineer, but have done some fluid dynamics work. Thus, I'm not super familiar with what "wake blockage" is. A tentative look suggests that it might be similar to this work that I encountered[1], which suggests that by carefully positioning the wind turbines, one can extract more energy basically via the Bernoulli effect. Not sure if this is something of interest (or relevant) to you or not, but when I talked to some of the people working on that subject, it was implied to me that the manufacturers of wind turbine weren't interested in this, as it may decrease the number of wind turbines they can sell...

[1]: https://onlinelibrary.wiley.com/doi/epdf/10.1002/we.1806

[wingineer]

Interesting paper. When I refer to "wake blockage", think of the turbines in the middle of a huge grid of machines. The energy in incoming wind on any side of the farm is mostly extracted by the outer turbines. The inner turbines typically produce ~15-20% less energy due to this effect. Also, the wind hitting them is more turbulent/"dirty" as it recovers back to free-stream velocity behind the front row of machines, which can cause abnormal fatigue patterns.

That's definitely of interest to me, although I think that manufacturers are interested in it. Many manufacturers are very conservative with installed/environmental conditions of their production machines and want to minimize risks, instead of potentially alienating a developer by suggesting a scheme that could fatigue turbines or have other unintended consequences. If anything, the paper suggests to me that if adopted, manufacturers could sell even more turbines!

[pwnna]

It's very possible that I misinterpreted the situation as effectively I got to this information through an overheard in discussions with other fluid dynamicists in school. I thought the information presented is kind of interesting, so I was surprised that no one continued to pursue this avenue of research. I'm glad that you find this interesting, perhaps this knowledge could be put to good use. Although, there may be there are other factors that I'm not aware of impacting the real world performance of this, as my specialty is not in wind turbines (not yet anyway).

[olau]

FWIW, I know that Vestas has a department with a super computer dedicated to helping their customers choose optimal positions. And I also know of some recently commissioned large wind farms where the company behind explicitly mentioned wake optimizations. All the big turbine manufacturers are in an optimization race.

[pwnna]

That's interesting to know. I didn't know that turbine manufactures are that state of the art. I mostly thought they are just building some sort of standard turbines and deploying it to different places like building houses. Evidently I'm mistaken. Perhaps I should investigate this area a bit further...

[dzhiurgis]

Can you use huge regular turbine to vertically steer wake in to array of smaller vertical turbines?

[petre]

What about Gorlov helical turbine designs?