4 ms·

Yes, I'm curious about this, and a FAQ on the technical limitations which lead to the situation that GP mentions. I'd have thought that you could have a mechani

Yes, I'm curious about this, and a FAQ on the technical limitations which lead to the situation that GP mentions. I'd have thought that you could have a mechanical / electrical brake on the blades to keep velocities reasonable, or gears as uyou mention, or maybe it's other mechanical stresses.

Gibbon1 8y ago
I think there is optimization pressure between the size of the generator and the median amount of power produced. Wind speed probably has some sort of log distribution. AKA wind speed hours/year 0-10 4000 10-15 2700 15-20 1100 25-30 600 35-40 300 40-50 50 50-55 15 At some point the cost analysis says the extra power generated isn't worth the cost of the oversize generator needed to extract it so just feather the turbine.
bigiain 8y ago
The thing that's not obvious to most people is that the power contained in moving air is proportional to the cube of the airspeed. If you're local "average wind speed" is 5m/s (~12mph, a "Gentle Breeze" and #3 on the Beaufort scale), and you size your wind turbine to generate useful power (say, 1000W, for example) at that speed, you have two consequences due to that speed-cubed term. 1) When there's only light wind - say half your design average speed, you're only gonna get 1/8th of your 1000W target, so only 125W which isn't very useful if you've got a 1000W requirement. 2) The _bigger_ problem is when the wind blows faster than average. If you get twice average speeds, your turbine is going to generate 8kW which you'll need to safely deal with. But twice isn't your problem - in the real world it's not uncommon for 3 or 4 times average windspeed (what we'd normally just call "a windy day" and 7 or 8 on the Beaufort scale), at which stage you're going to need to safely dump 64kW of power - if your turbine hasn't been braked/parks appropriately (or torn itself to pieces.) If you're still spinning in hurricane conditions, you've got another doubling of windspeed, and another eightfold increase in power, so now your "1000W generator" is unleashing half a megawatt into your wiring and control electronics (or the plasma in the smoke where your wiring used to be...) Beaufort scale with speeds and descriptions: https://en.wikipedia.org/wiki/Beaufort_scale#Modern_scale https://en.wikipedia.org/wiki/Beaufort_scale#Modern_scale Some real world windspeed measurements showing upper end outliers of 8 times average speed: http://www.wind-power-program.com/wind_statistics.htm http://www.wind-power-program.com/wind_statistics.htm
- hvidgaard 8y ago
  That assumes that the turbine have the same efficiency over all wind speeds. Realistically, it will not - but your point stands none the less.

Gibbon1 8y ago

I think there is optimization pressure between the size of the generator and the median amount of power produced. Wind speed probably has some sort of log distribution. AKA wind speed hours/year 0-10 4000 10-15 2700 15-20 1100 25-30 600 35-40 300 40-50 50 50-55 15 At some point the cost analysis says the extra power generated isn't worth the cost of the oversize generator needed to extract it so just feather the turbine.

bigiain 8y ago

The thing that's not obvious to most people is that the power contained in moving air is proportional to the cube of the airspeed. If you're local "average wind speed" is 5m/s (~12mph, a "Gentle Breeze" and #3 on the Beaufort scale), and you size your wind turbine to generate useful power (say, 1000W, for example) at that speed, you have two consequences due to that speed-cubed term. 1) When there's only light wind - say half your design average speed, you're only gonna get 1/8th of your 1000W target, so only 125W which isn't very useful if you've got a 1000W requirement. 2) The _bigger_ problem is when the wind blows faster than average. If you get twice average speeds, your turbine is going to generate 8kW which you'll need to safely deal with. But twice isn't your problem - in the real world it's not uncommon for 3 or 4 times average windspeed (what we'd normally just call "a windy day" and 7 or 8 on the Beaufort scale), at which stage you're going to need to safely dump 64kW of power - if your turbine hasn't been braked/parks appropriately (or torn itself to pieces.) If you're still spinning in hurricane conditions, you've got another doubling of windspeed, and another eightfold increase in power, so now your "1000W generator" is unleashing half a megawatt into your wiring and control electronics (or the plasma in the smoke where your wiring used to be...) Beaufort scale with speeds and descriptions: https://en.wikipedia.org/wiki/Beaufort_scale#Modern_scale https://en.wikipedia.org/wiki/Beaufort_scale#Modern_scale Some real world windspeed measurements showing upper end outliers of 8 times average speed: http://www.wind-power-program.com/wind_statistics.htm http://www.wind-power-program.com/wind_statistics.htm

hvidgaard 8y ago
That assumes that the turbine have the same efficiency over all wind speeds. Realistically, it will not - but your point stands none the less.