Comment by mrb | Hacker News Reader

Comment by mrb | Hacker News Reader

You can see technical drawings of their device in their patent (US 11391262): https://patentimages.storage.googleapis.com/26/02/b1/f9004c8... The article calls it "motionless" and "bladeless", but this is patently (hah!) false. There are actually spinning blades... See figures 16c, 16d, 19 in the patent: the blades are in the turbine underneath the central body element.

At first sight, given the quantity of material used in the device for the foils and central body, relative to the small turbine size, it's hard to intuitively picture how or why it can be more efficient than a regular wind turbine built using the same amount of material which could, therefore, have much larger blades.

Edit: in fact the inventor of the device, Carsten Hein Westergaard, previously published results from a prototype https://iopscience.iop.org/article/10.1088/1742-6596/2265/4/... in which he claims the prototype achieved an efficiency of 42% of Betz limit, which is inferior to standard utility-scale turbines (Wikipedia claims 75-85% but I haven't checked sources: https://en.wikipedia.org/wiki/Betz%27s_law#Betz's_law_and_co... ) so that seems to confirm my intuition.

> efficiency of 42% of Betz limit, which is inferior to standard utility-scale turbines

That isn't surprising at all; wind generation scales very very well with larger size. If it actually achieved 42% at that size, it would still be a major innovation.

But that's also a strong claim that requires very strong evidence. The reasons for inefficiency at smaller scales are fundamental: higher drag to lift. Essentially what they're doing is using the existing building as part of the device to direct wind. This is not a new idea, and in favorable conditions you can get some impressive numbers. But in real life..

https://www.renewableenergyworld.com/storage/small-wind-turb...

> inferior to standard utility-scale turbines

But isn't this supposed to be a rooftop wind turbine? I'm curious how it compares to other small turbines that I could conceivably put on my own property.

There's a difference between thermodynamic efficiency and cost efficiency. Extracting 40% of the energy in the wind for $500 is very often going to be better than extracting 70% for $5000.

Yes but then location comes into play - offshore power needs to be delivered!

Just to ask. Do you think the housing of the turbine would somehow "channel" the wind it collects into the blades? And therefore increase the performance or yield against the size of the blades? Maybe in this way, the comparison is legitimate, that a smaller turbine blade (as in this case) can collect more wind?

I'm honestly not sure if that holds up properly, like from a true physics point of view. But it kind of makes sense from intuition. It would seem you'd get quite a fast moving turbine blade with this configuration.

That's entirely the point of Aeromine's invention: the foil and body channel the wind (by decreasing air pressure between the foils) and this increases the speed of wind at the turbine. But per my edit, it doesn't seem sufficient to beat the efficiency of traditional wind turbines. I suppose that's why the company tries to focus on other advantage (less noisy, better aesthetics).

If I remember correctly they claim something like 40% of a conventional turbine, so it doesn't beat a conventional turbine in a classic setting however it may work well enough in a residential/light commercial setting.

It really seems like a reverse Dyson bladeless fan.

Dyson Jet https://www.youtube.com/watch?v=jbXJa8osys0

'Bladeless' airplane turbine https://www.youtube.com/watch?v=bPZI6XoHi10

> 40% of a conventional turbine

If I'm not mistaken, a conventional turbine can turn to face the wind but these can't. That could significantly impact actual performance.

I could see another advantage for residential use -- you should be able to make the failure mode for this style safer, because you are already wrapping the turbine in metal. It should also be easy to close the channel and stop wind from getting to the blades which is also not possible with traditional designs.

But yeah, I'm leaning with the other comments in this thread that these guys sound too shifty in the way they're promoting this, and it makes me suspicious of the utility of the product.

> not sure if that holds up properly, like from a true physics point of view

Thrust efficiency from ducting is real [1].

[1] https://en.wikipedia.org/wiki/Ducted_fan#Duct

What they're really after is using the structure to direct the wind and create stronger flows by the lip of the roof. This is not a new idea, but perhaps they have hit on a shroud design that works more effectively.

I have little doubt that it can produce impressive figures in very specific conditions - many designs do - but I doubt they see vastly improved real-world performance.

I think they mean that the blades are not visible from ground level. A big problem with wind turbines in residential areas is the motion is really distracting and shadows on windows can be annoying as heck. Although looking at the patent, this thing would be stopped up with dead squirrels on my house in ten minutes unless they added some grating to the inlet.

The blades are spinning so fast cleanup becomes a simple matter of wiping off the red mist.

Sounds like the inverse of those "bladeless" dyson fans where the blades are hidden inside the body/base. Might still be a net safety improvement?

But it is not about power per kg of materials but power per $ spent. You may be able to fabricate the wing elements out of cheaper and heavier materials using simpler methods.

This is like the Dyson fan in reverse. Look ma, no blades - well there are, just not behind/facing the wind.

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