5 ms·

(Not OP, and) Not sure about aquatic life, but if those turbines are anything like the ones on land, then the rotors are definitely NOT spinning slowly! And the

by pbh101 9y ago

(Not OP, and) Not sure about aquatic life, but if those turbines are anything like the ones on land, then the rotors are definitely NOT spinning slowly! And they look even bigger, which would imply a faster speed at the rotor tip for the same rotational velocity. And as a result there have been issues with them killing lots of birds, esp 1) IIRC large predatory birds which are looking down at the ground for prey and can't change course as easily as a small bird, and 2) being in migration paths. But I think both of those problems are pretty well understood by now and I'm guessing this project takes both into account.

djrogers 9y ago
> if those turbines are anything like the ones on land, then the rotors are definitely NOT spinning slowly! You apparently haven’t seen modern (ie installed in the last 5 years, this stuff moves quickly) wind turbines. They are huge and slow turning, also much quieter than the smaller, shorter, faster spinning ones.
- usrusr 9y ago
  The rotors turn slow in terms of rpm but fast in terms of wingtip speed, due to the very large radius. But many things kill birds, I do not believe that wind turbines could ever make much of a difference.
  - abirkill 9y ago
    As an example, the Vestas V164-8MW seems to be one of the largest off-shore wind turbines, and has a rotor diameter of 164m and a rotational speed of between 4.8 and 12.1rpm. [1] Unless I'm miscalculating, that means that the tip of one of the rotors will travel 515 metres per revolution, which at 4.8-12.1rpm is a tip speed of between 2,472 metres per minute and 6,231 metres per minute. To put that in more common units, that's between 148km/h and 373km/h. [1] https://stateofgreen.com/en/profiles/vestas/solutions/v164-8-0-mw-offshore https://stateofgreen.com/en/profiles/vestas/solutions/v164-8...
    - jerven 9y ago
      Yes all correct. Those top 'tip' speeds where reached with smaller turbines as well. Max tip speed is a design limitation on blades (induced vibrations due to turbulence). What it means is that small turbines had much higher RPM, and the average speed along the blade was much higher in smaller turbines. Second benefit of larger turbines is much more of the swept area is outside of the normal flight heights of birds. Either too low for migration patterns or too high for most hunting and scooting flight heights (relative to nearest surface). So one 8MW turbine is likely to kill a lot less than 8 * 1 MW and much, much less than 80 * 100kw, even if it has a much larger swept area. Now as these are offshore turbines, and Hywind, being for quite deep water. Likely to be far offshore, there are not that many birds around too get hit in the first place. The nice thing about the slower RPMs compared to smaller tubines (especially pre 2000's) is that slower RPM's make it easier to spot the turbine for birds. High RPM's give optical effects that make it hard to predict where something is going (e.g. wheel looks like rotating backwards etc...) so bigger is easier too avoid for birds.
  - pbh101 9y ago
    If wind farms are going to contribute significantly, then there will be a lot of them. In terms of replacing fossil fuels they will likely still be a net benefit, but unless the Audubon Society has been captured by Big Oil etc (which I doubt, but possible) then bird safety still sounds like an open question. [1] http://www.audubon.org/news/will-wind-turbines-ever-be-safe-birds http://www.audubon.org/news/will-wind-turbines-ever-be-safe-...
    - anotherbrownguy 9y ago
      I would be very happy with all birds being extinct if that is what would take to come up with a solid replacement for fossil fuels. The problem with wind power is it will not replace anything. Wind cannot provide reliable power so it has to be backed by something else that is reliable. Also, wind provides variable power so infrastructure has to be setup such that it can handle such variation. After accounting for initial setup costs and maintenance of wind turbines (it is worse than Solar in this regard because of the wear and tear in mechanical parts) and power infrastructure (which has to be designed to handle such variation without any impact on consumers), it will take a very long time to break even, if at all. And don't forget that we will still need something reliable like nuclear or fossil fuels to back it up... which we already have enough of to last for thousands of years. So, basically, all we get with wind is more work for no gain at all (not to mention the unnecessary environmental harm). I am sure Statoil is not ignorant of this. They are just using a small portion of their 100 billion dollar yearly revenue in this to please the eco-terrorists.
  - WalterBright 9y ago
    Cats seem to be the main threat to birds.
    - petre 9y ago
      It also helps if you have a glass wall building or a wind farm around, which means free lunch for all the stray cats.
  - petre 9y ago
    Yes they do, because birds are confused by the light signals at night or during foggy days and go towards them. Big glass windows/walls also kill birds. I work in an office with glass curtain walls and a lot of birds end up flying into them. To make matters worse, we also have stray cats around the building, so birds that fall to the ground and are not dead upon hitting the window end up being lunch.
- pbh101 9y ago
  The ones I'm referring to are in large installations in the last 10 years in the US Midwest. Each rotor blade is transported individually on the back of a flatbed semi-truck. As pointed out elsewhere in the thread: indeed the RPM can be low, but the rotor tip velocity is high.
- mikeyouse 9y ago
  Large turbines like the Vestas V164 8.0MW have nominal rotor speeds of ~10RPM. This sounds pretty slow, but with a blade length of 80M, this corresponds to a tip speed of nearly 200mph. Low RPM doesn't mean low tip speeds.

by pbh101 9y ago

djrogers 9y ago

> if those turbines are anything like the ones on land, then the rotors are definitely NOT spinning slowly! You apparently haven’t seen modern (ie installed in the last 5 years, this stuff moves quickly) wind turbines. They are huge and slow turning, also much quieter than the smaller, shorter, faster spinning ones.

usrusr 9y ago
The rotors turn slow in terms of rpm but fast in terms of wingtip speed, due to the very large radius. But many things kill birds, I do not believe that wind turbines could ever make much of a difference.
- abirkill 9y ago
  As an example, the Vestas V164-8MW seems to be one of the largest off-shore wind turbines, and has a rotor diameter of 164m and a rotational speed of between 4.8 and 12.1rpm. [1] Unless I'm miscalculating, that means that the tip of one of the rotors will travel 515 metres per revolution, which at 4.8-12.1rpm is a tip speed of between 2,472 metres per minute and 6,231 metres per minute. To put that in more common units, that's between 148km/h and 373km/h. [1] https://stateofgreen.com/en/profiles/vestas/solutions/v164-8-0-mw-offshore https://stateofgreen.com/en/profiles/vestas/solutions/v164-8...
  - jerven 9y ago
    Yes all correct. Those top 'tip' speeds where reached with smaller turbines as well. Max tip speed is a design limitation on blades (induced vibrations due to turbulence). What it means is that small turbines had much higher RPM, and the average speed along the blade was much higher in smaller turbines. Second benefit of larger turbines is much more of the swept area is outside of the normal flight heights of birds. Either too low for migration patterns or too high for most hunting and scooting flight heights (relative to nearest surface). So one 8MW turbine is likely to kill a lot less than 8 * 1 MW and much, much less than 80 * 100kw, even if it has a much larger swept area. Now as these are offshore turbines, and Hywind, being for quite deep water. Likely to be far offshore, there are not that many birds around too get hit in the first place. The nice thing about the slower RPMs compared to smaller tubines (especially pre 2000's) is that slower RPM's make it easier to spot the turbine for birds. High RPM's give optical effects that make it hard to predict where something is going (e.g. wheel looks like rotating backwards etc...) so bigger is easier too avoid for birds.
- pbh101 9y ago
  If wind farms are going to contribute significantly, then there will be a lot of them. In terms of replacing fossil fuels they will likely still be a net benefit, but unless the Audubon Society has been captured by Big Oil etc (which I doubt, but possible) then bird safety still sounds like an open question. [1] http://www.audubon.org/news/will-wind-turbines-ever-be-safe-birds http://www.audubon.org/news/will-wind-turbines-ever-be-safe-...
  - anotherbrownguy 9y ago
    I would be very happy with all birds being extinct if that is what would take to come up with a solid replacement for fossil fuels. The problem with wind power is it will not replace anything. Wind cannot provide reliable power so it has to be backed by something else that is reliable. Also, wind provides variable power so infrastructure has to be setup such that it can handle such variation. After accounting for initial setup costs and maintenance of wind turbines (it is worse than Solar in this regard because of the wear and tear in mechanical parts) and power infrastructure (which has to be designed to handle such variation without any impact on consumers), it will take a very long time to break even, if at all. And don't forget that we will still need something reliable like nuclear or fossil fuels to back it up... which we already have enough of to last for thousands of years. So, basically, all we get with wind is more work for no gain at all (not to mention the unnecessary environmental harm). I am sure Statoil is not ignorant of this. They are just using a small portion of their 100 billion dollar yearly revenue in this to please the eco-terrorists.
- WalterBright 9y ago
  Cats seem to be the main threat to birds.
  - petre 9y ago
    It also helps if you have a glass wall building or a wind farm around, which means free lunch for all the stray cats.
- petre 9y ago
  Yes they do, because birds are confused by the light signals at night or during foggy days and go towards them. Big glass windows/walls also kill birds. I work in an office with glass curtain walls and a lot of birds end up flying into them. To make matters worse, we also have stray cats around the building, so birds that fall to the ground and are not dead upon hitting the window end up being lunch.
pbh101 9y ago
The ones I'm referring to are in large installations in the last 10 years in the US Midwest. Each rotor blade is transported individually on the back of a flatbed semi-truck. As pointed out elsewhere in the thread: indeed the RPM can be low, but the rotor tip velocity is high.
mikeyouse 9y ago
Large turbines like the Vestas V164 8.0MW have nominal rotor speeds of ~10RPM. This sounds pretty slow, but with a blade length of 80M, this corresponds to a tip speed of nearly 200mph. Low RPM doesn't mean low tip speeds.