5 ms·

figuring there isn't much of a weight difference, I do wonder if the thermal difference with one blade being black will have any impact on performance and longe

figuring there isn't much of a weight difference, I do wonder if the thermal difference with one blade being black will have any impact on performance and longevity of the structure as a whole.

navaati 6y ago
Is there really thermal concerns for wind turbine blades ? These things are literally aircooled by the wind, aren't they ?
- pcl 6y ago
  Yes, but they are also exposed to significant stresses. The tips Can move at hundreds of kilometers per hour, and of course the blades are constantly subject to rotational forces as well.
- jzwinck 6y ago
  They are only cooled by the wind when there is wind. Sometimes there is a lot of sun and no wind. One side of the blades will heat up more than the other, and potentially undergo rapid cooling when a rainstorm hits.
EForEndeavour 6y ago
Maybe the black blade gets so hot that it disintegrates birds via steam explosion, leaving no carcass for researchers to find and catalogue, leading them to the erroneous conclusion that black-painted windmills kill fewer birds. EDIT: /s
sgc 6y ago
It's going to affect longevity somehow due to uneven wear. But whether that means 2 hours less service or 2 years I have no idea. In Norway, where it is not generally as hot as some other locations, probably 2 hours.
elliekelly 6y ago
Maybe the whole blade doesn't need to be black? It sounds like they're going to experiment with different colors and patterns but I do wonder whether a black outline painted on the blades or even one black stripe down the center of the blade would be sufficient to put the birds on notice.
Ancapistani 6y ago
Paint the fronts of every blade black, and leave the backs white. The wear should be even (because the weight is balanced), and you'd even get a (granted, likely unmeasurably small) boost in output due to the sun! https://en.wikipedia.org/wiki/Crookes_radiometer https://en.wikipedia.org/wiki/Crookes_radiometer
- saalweachter 6y ago
  ... the problem being that birds can approach the turbine from either side.
  - Ancapistani 6y ago
    This is a bit of a silly thread, but I'm curious if that's the case. Assuming that the issue is that the blades are hard for birds to see, not "impossible", then having them black on the windward side may solve the problem. For a given wind speed `x` and bird flight speed `y`, the relative speed when approaching the blades from the windward side would be `x + y`. The relative speed when approaching from the leeward side would be `x - y`, giving the bird additional time to react. ... on the other hand, at `x + y` the bird's body would pass through the blade plane is less time than at `x - y`, potentially reducing the likelihood of a strike. Now I'm curious if there are data showing where birds have been found dead are wind turbines. Intuitively, I would expect there to be more dead birds on one side than the other.
    - Someone 6y ago
      I would think most birds don’t fly straight into a blade, but get hit from the side (modern turbines are large; tips of blades will easily hit 100mph) That would make relative speed in both cases about equal.

figuring there isn't much of a weight difference, I do wonder if the thermal difference with one blade being black will have any impact on performance and longevity of the structure as a whole.

navaati 6y ago

Is there really thermal concerns for wind turbine blades ? These things are literally aircooled by the wind, aren't they ?

pcl 6y ago
Yes, but they are also exposed to significant stresses. The tips Can move at hundreds of kilometers per hour, and of course the blades are constantly subject to rotational forces as well.
jzwinck 6y ago
They are only cooled by the wind when there is wind. Sometimes there is a lot of sun and no wind. One side of the blades will heat up more than the other, and potentially undergo rapid cooling when a rainstorm hits.

EForEndeavour 6y ago

Maybe the black blade gets so hot that it disintegrates birds via steam explosion, leaving no carcass for researchers to find and catalogue, leading them to the erroneous conclusion that black-painted windmills kill fewer birds. EDIT: /s

sgc 6y ago

It's going to affect longevity somehow due to uneven wear. But whether that means 2 hours less service or 2 years I have no idea. In Norway, where it is not generally as hot as some other locations, probably 2 hours.

elliekelly 6y ago

Maybe the whole blade doesn't need to be black? It sounds like they're going to experiment with different colors and patterns but I do wonder whether a black outline painted on the blades or even one black stripe down the center of the blade would be sufficient to put the birds on notice.

Ancapistani 6y ago

Paint the fronts of every blade black, and leave the backs white. The wear should be even (because the weight is balanced), and you'd even get a (granted, likely unmeasurably small) boost in output due to the sun! https://en.wikipedia.org/wiki/Crookes_radiometer https://en.wikipedia.org/wiki/Crookes_radiometer

saalweachter 6y ago
... the problem being that birds can approach the turbine from either side.
- Ancapistani 6y ago
  This is a bit of a silly thread, but I'm curious if that's the case. Assuming that the issue is that the blades are hard for birds to see, not "impossible", then having them black on the windward side may solve the problem. For a given wind speed `x` and bird flight speed `y`, the relative speed when approaching the blades from the windward side would be `x + y`. The relative speed when approaching from the leeward side would be `x - y`, giving the bird additional time to react. ... on the other hand, at `x + y` the bird's body would pass through the blade plane is less time than at `x - y`, potentially reducing the likelihood of a strike. Now I'm curious if there are data showing where birds have been found dead are wind turbines. Intuitively, I would expect there to be more dead birds on one side than the other.
  - Someone 6y ago
    I would think most birds don’t fly straight into a blade, but get hit from the side (modern turbines are large; tips of blades will easily hit 100mph) That would make relative speed in both cases about equal.