5 ms·

VAWTs suffer from 2 serious drawbacks: 1) they're crap at starting up - i.e. going from stationary to moving - and usually need some supplementary help to do so

VAWTs suffer from 2 serious drawbacks: 1) they're crap at starting up - i.e. going from stationary to moving - and usually need some supplementary help to do so, and 2) they're noisy - as in noisy as hell! I wouldn't want one within 500m of my house. I recall seeing report of a similar result many years ago (at least 10, perhaps much more) where VAWTs deployed in complementary pairs were shown to be more efficient, so this looks like a repeat /rediscovery of the same result.

blakesterz 5y ago
That's interesting. Hydro is crap at startup too (they need black start units, at least the big ones do) [What I wrote here about black start was pretty much wrong, not sure what I was thinking] so maybe that's not too big of a problem, but that sound thing seems bad, even if the units are out on the water. Those things are loud, I had no idea! "The noise emission from the wind turbine was measured, at wind speed 8 m/s, 10 m above ground, to 96.2 dBA" https://www.mdpi.com/1996-1073/9/1/19/htm https://www.mdpi.com/1996-1073/9/1/19/htm [Edited to add: What I wrote about hydro black start units was really wrong, I wasn't thinking when I wrote that, it needs far more detailed explanation like the comment below.]
- probablypower 5y ago
  > * Hydro is crap at startup too (they need black start units, at least the big ones do) * This is a misunderstanding. All generators require an excitation current to start up. Most generators get this excitation from the grid. For large, important generators they also have black start, so that they can provide excitation on-site. This means they don't need to bootstrap themselves from a grid. Hydro tends to have black start not because 'they need it' but because it is critically important from a grid security perspective. During a blackout, you want your high inertia, flexible machines online first - these are hydros for systems that have them. If you don't have blackstart on these machines, you need them on some other machine online first to energize the grid. You wouldn't put blackstart units on wind turbines, simply because they are worthless if there isn't already an energised grid to support into (they aren't grid forming). So you can always assume grid-based excitation current for wind generators. I think OP was talking about the cut-in speed (at what wind speed can the turbine start producing power). For HAWTs this is at wind speeds of around 5 m/s. For VAWTs, I don't know, but I assume it is a little higher based on the OP's comment, and that they may even need some mechanical assistance to get them spinning in the first place.
  - blakesterz 5y ago
    Nuts, you're totally right. I really know better, not sure how I got that so wrong.
- JohnJamesRambo 5y ago
  Are you sure about that, because I was just reading the Black Start Wikipedia yesterday and it listed Hydro as one of the best at requiring little start up power. Hydro is often the Black Start source for other power plants.
  - blakesterz 5y ago
    I am sure I was wrong :-)
- antiterra 5y ago
  The paper you linked suggests that horizontal turbines are even louder: “The noise emission at 6 m/s 10 m above ground was measured to 94.1 dBA, this while while operating at optimum tip speed. Available noise surveys performed on similar sized operating at optimum tip speed. Available noise surveys performed on similar sized HAWTs [27–30] HAWTs [27–30] has established noise emissions of 95.1–100.2 dBA and 97.3–102.4 dBA for 6 m/s and has established noise emissions of 95.1–100.2 dBA and 97.3–102.4 dBA for 6 m/s and 8 m/s respectively”
Valgrim 5y ago
What's the source of the noise? The turbine itself? the air flow around the blades?
- FriedrichN 5y ago
  And would it still be an issue if they're in the sea?
  - giantg2 5y ago
    I would guess that would increase the infrastructure/cost for transmission if you have to put them further out to sea.
    - FriedrichN 5y ago
      Where I live the turbines are already quite far out, I don't think I'd be able to hear them if they were of the vertical kind.
      - giantg2 5y ago
        95db over water could be heard from a couple miles away, especially if the atmospheric conditions are right. I don't know how far out the current ones are since we don't have any around here. This brings up another interesting point. If there are concerns around ship engines and submarine sonar or ELF for marine life, I wonder if any testing has been done concerning that with the turbines.
    - JulianMorrison 5y ago
      In the UK wind farms are usually put in the sea.
  - jelder 5y ago
    Noise pollution is pretty harmful to sea life, especially cetaceans. https://oceanservice.noaa.gov/facts/ocean-noise.html https://oceanservice.noaa.gov/facts/ocean-noise.html
rswskg 5y ago
All large wind turbines are loud. Like, unbearably loud.
- harg 5y ago
  I don't believe this is true. There's an installation of 9 1MW turbines (perhaps quite small in comparison to the largest ones around today) near where I live that I frequently cycle past (within ~50m). Even in strong winds they are barely audible.
  - baud147258 5y ago
    how audible wind turbine also depends on which direction the wind is blowing
deleted 5y ago
[deleted]
jillesvangurp 5y ago
I think there may have been turbines with those two problems but that does not mean that all turbines are like that. Merely that there were some issues to sort out back in the day when you read about someone allegedly having these issues. Basically, noise would indicate either some problem with loose parts, a lot of friction, turbulence or something else that is clearly being inefficient. Obviously to compete with state of the art horizontal turbines, you'd use highly durable materials with awesomely low friction and generally be shooting for very high levels of efficiency. Some other things I've seen suggests that small vertical turbines are suitable for deployment in urban environments where they work with low/variable wind speeds at completely acceptable noise levels. You could put these on your roof even. I left a link elsewhere in this thread if you are interested. Basically the article is about a group of scientists that ran the numbers and came up with different conclusions than you. 15% more efficient is quite a lot.

blakesterz 5y ago

That's interesting. Hydro is crap at startup too (they need black start units, at least the big ones do) [What I wrote here about black start was pretty much wrong, not sure what I was thinking] so maybe that's not too big of a problem, but that sound thing seems bad, even if the units are out on the water. Those things are loud, I had no idea! "The noise emission from the wind turbine was measured, at wind speed 8 m/s, 10 m above ground, to 96.2 dBA" https://www.mdpi.com/1996-1073/9/1/19/htm https://www.mdpi.com/1996-1073/9/1/19/htm [Edited to add: What I wrote about hydro black start units was really wrong, I wasn't thinking when I wrote that, it needs far more detailed explanation like the comment below.]

probablypower 5y ago
> * Hydro is crap at startup too (they need black start units, at least the big ones do) * This is a misunderstanding. All generators require an excitation current to start up. Most generators get this excitation from the grid. For large, important generators they also have black start, so that they can provide excitation on-site. This means they don't need to bootstrap themselves from a grid. Hydro tends to have black start not because 'they need it' but because it is critically important from a grid security perspective. During a blackout, you want your high inertia, flexible machines online first - these are hydros for systems that have them. If you don't have blackstart on these machines, you need them on some other machine online first to energize the grid. You wouldn't put blackstart units on wind turbines, simply because they are worthless if there isn't already an energised grid to support into (they aren't grid forming). So you can always assume grid-based excitation current for wind generators. I think OP was talking about the cut-in speed (at what wind speed can the turbine start producing power). For HAWTs this is at wind speeds of around 5 m/s. For VAWTs, I don't know, but I assume it is a little higher based on the OP's comment, and that they may even need some mechanical assistance to get them spinning in the first place.
- blakesterz 5y ago
  Nuts, you're totally right. I really know better, not sure how I got that so wrong.
JohnJamesRambo 5y ago
Are you sure about that, because I was just reading the Black Start Wikipedia yesterday and it listed Hydro as one of the best at requiring little start up power. Hydro is often the Black Start source for other power plants.
- blakesterz 5y ago
  I am sure I was wrong :-)
antiterra 5y ago
The paper you linked suggests that horizontal turbines are even louder: “The noise emission at 6 m/s 10 m above ground was measured to 94.1 dBA, this while while operating at optimum tip speed. Available noise surveys performed on similar sized operating at optimum tip speed. Available noise surveys performed on similar sized HAWTs [27–30] HAWTs [27–30] has established noise emissions of 95.1–100.2 dBA and 97.3–102.4 dBA for 6 m/s and has established noise emissions of 95.1–100.2 dBA and 97.3–102.4 dBA for 6 m/s and 8 m/s respectively”

Valgrim 5y ago

What's the source of the noise? The turbine itself? the air flow around the blades?

FriedrichN 5y ago
And would it still be an issue if they're in the sea?
- giantg2 5y ago
  I would guess that would increase the infrastructure/cost for transmission if you have to put them further out to sea.
  - FriedrichN 5y ago
    Where I live the turbines are already quite far out, I don't think I'd be able to hear them if they were of the vertical kind.
    - giantg2 5y ago
      95db over water could be heard from a couple miles away, especially if the atmospheric conditions are right. I don't know how far out the current ones are since we don't have any around here. This brings up another interesting point. If there are concerns around ship engines and submarine sonar or ELF for marine life, I wonder if any testing has been done concerning that with the turbines.
  - JulianMorrison 5y ago
    In the UK wind farms are usually put in the sea.
- jelder 5y ago
  Noise pollution is pretty harmful to sea life, especially cetaceans. https://oceanservice.noaa.gov/facts/ocean-noise.html https://oceanservice.noaa.gov/facts/ocean-noise.html

rswskg 5y ago

All large wind turbines are loud. Like, unbearably loud.

harg 5y ago
I don't believe this is true. There's an installation of 9 1MW turbines (perhaps quite small in comparison to the largest ones around today) near where I live that I frequently cycle past (within ~50m). Even in strong winds they are barely audible.
- baud147258 5y ago
  how audible wind turbine also depends on which direction the wind is blowing

deleted 5y ago

[deleted]

jillesvangurp 5y ago

I think there may have been turbines with those two problems but that does not mean that all turbines are like that. Merely that there were some issues to sort out back in the day when you read about someone allegedly having these issues. Basically, noise would indicate either some problem with loose parts, a lot of friction, turbulence or something else that is clearly being inefficient. Obviously to compete with state of the art horizontal turbines, you'd use highly durable materials with awesomely low friction and generally be shooting for very high levels of efficiency. Some other things I've seen suggests that small vertical turbines are suitable for deployment in urban environments where they work with low/variable wind speeds at completely acceptable noise levels. You could put these on your roof even. I left a link elsewhere in this thread if you are interested. Basically the article is about a group of scientists that ran the numbers and came up with different conclusions than you. 15% more efficient is quite a lot.