4 ms·

>That would rule out a great many locations. I wonder if you can have a portable system deployable during hurricanes?

jacquesm 11y ago
Hurricanes are when you want your system stowed. The power available from wind goes up as the cube of the windspeed. So you go from generating lots of power and 'doing ok' to catastrophic failure and 'bits and pieces' over one doubling. An 8 MW output turbine that suddenly has to deal with 100 MW had better be shut-down and furled well before that moment arrives. Otherwise you can bring your vacuum cleaner and a mop. There is at this moment no blade material strong enough to deal with hurricane level winds while operating at rated speed. It works like this: Wind is moving air and moving air has mass. So if you move that mass twice as fast the energy that it contains is e=mv^2 the square of the energy that it contained before impacting on the blades. But it is also more air, twice as much air will pass through the rotor blades in the same amount of time, so you get to double again. Hence the factor of 8. Most windmills will shut down well before they reach the danger point, they simply furl their blades to ride out the storm. They will track the wind even in this state because if the wind would hit the rotor at an angle that could start up the rotor again and then all hell will break loose because the brake will not be able to withstand the rotor once it reaches a certain speed, it will simply burn up and from there to the bits and pieces stage it is less than a few minutes. There are some youtube movies about wind turbines that fail to switch to safe mode before a storm hits, not pretty.
- cinquemb 11y ago
  I'm asking about the about the kite turbines. >I think the fairly simple answer is that you don't stack them or allow for any interference at all. If your kite goes up to 250m and has a 1km tether you space all your launchers on a 1km "radius" hexagonal grid. Your wind farm takes up more space but at first that's no problem at all. You could probably make it work at a 500m hexagonal grid but there's a small amount of risk associated there.
  - jacquesm 11y ago
    Wind is wind. Whether you're a kite or on the ground makes no difference. During a hurricane you want to be out of the way or there'll be pieces.
    - cinquemb 11y ago
      So if you had a tether strong enough to withstand the tensile force and able were to distribute the moments from the forces of where its tethered, you don't think that would work?
      - jacquesm 11y ago
        No, it would not work. The tensile force is going to go up so high that you'd have to overdesign it to the point of being impractical for normal use and even then it would have to be made out of un-obtanium. If you compute the forces in a hurricane acting on any appreciable surface area acting first on the internal structure of the kite (to transfer the force to the tether attachment point), then to the tether itself (and hurricane winds change direction and strength very rapidly) and finally from the tether to the ground station (with the edge in contact with a gimball (sp?) so the kite can rotate around the attachment point) you're looking at something that is no longer economically feasible or something so heavy that it will absorb a fair amount of the power generated just to stay aloft. Hurricanes will happily destroy structures many times stronger than this kite that are anchored in concrete, will blow 30 ton trucks over and in general are a menace. To harvest their power is akin to trying to set up an electrical plant that is exclusively powered by lightning or solar flares. Yes, there is power there, no, we have no practical way of harvesting that power, the best we can do is to try to either get out of the way or to shed it in a way that it does not do damage. The events are too rare, to unpredictable and too powerful to be practically harvestable.
        cinquemb 11y ago
        >Yes, there is power there, no, we have no practical way of harvesting that power, the best we can do is to try to either get out of the way or to shed it in a way that it does not do damage. So you sample for areas of a storm you can more predicatively than other places? >The events are too rare, to unpredictable and too powerful to be practically harvestable. But the distribution isn't uniform if you look at occurrence of where it happens on earth, some places are more likely to form storm systems vs others.

Hurricanes are when you want your system stowed. The power available from wind goes up as the cube of the windspeed. So you go from generating lots of power and 'doing ok' to catastrophic failure and 'bits and pieces' over one doubling. An 8 MW output turbine that suddenly has to deal with 100 MW had better be shut-down and furled well before that moment arrives. Otherwise you can bring your vacuum cleaner and a mop. There is at this moment no blade material strong enough to deal with hurricane level winds while operating at rated speed. It works like this: Wind is moving air and moving air has mass. So if you move that mass twice as fast the energy that it contains is e=mv^2 the square of the energy that it contained before impacting on the blades. But it is also more air, twice as much air will pass through the rotor blades in the same amount of time, so you get to double again. Hence the factor of 8. Most windmills will shut down well before they reach the danger point, they simply furl their blades to ride out the storm. They will track the wind even in this state because if the wind would hit the rotor at an angle that could start up the rotor again and then all hell will break loose because the brake will not be able to withstand the rotor once it reaches a certain speed, it will simply burn up and from there to the bits and pieces stage it is less than a few minutes. There are some youtube movies about wind turbines that fail to switch to safe mode before a storm hits, not pretty.

cinquemb 11y ago
I'm asking about the about the kite turbines. >I think the fairly simple answer is that you don't stack them or allow for any interference at all. If your kite goes up to 250m and has a 1km tether you space all your launchers on a 1km "radius" hexagonal grid. Your wind farm takes up more space but at first that's no problem at all. You could probably make it work at a 500m hexagonal grid but there's a small amount of risk associated there.
- jacquesm 11y ago
  Wind is wind. Whether you're a kite or on the ground makes no difference. During a hurricane you want to be out of the way or there'll be pieces.
  - cinquemb 11y ago
    So if you had a tether strong enough to withstand the tensile force and able were to distribute the moments from the forces of where its tethered, you don't think that would work?
    - jacquesm 11y ago
      No, it would not work. The tensile force is going to go up so high that you'd have to overdesign it to the point of being impractical for normal use and even then it would have to be made out of un-obtanium. If you compute the forces in a hurricane acting on any appreciable surface area acting first on the internal structure of the kite (to transfer the force to the tether attachment point), then to the tether itself (and hurricane winds change direction and strength very rapidly) and finally from the tether to the ground station (with the edge in contact with a gimball (sp?) so the kite can rotate around the attachment point) you're looking at something that is no longer economically feasible or something so heavy that it will absorb a fair amount of the power generated just to stay aloft. Hurricanes will happily destroy structures many times stronger than this kite that are anchored in concrete, will blow 30 ton trucks over and in general are a menace. To harvest their power is akin to trying to set up an electrical plant that is exclusively powered by lightning or solar flares. Yes, there is power there, no, we have no practical way of harvesting that power, the best we can do is to try to either get out of the way or to shed it in a way that it does not do damage. The events are too rare, to unpredictable and too powerful to be practically harvestable.
      - cinquemb 11y ago
        >Yes, there is power there, no, we have no practical way of harvesting that power, the best we can do is to try to either get out of the way or to shed it in a way that it does not do damage. So you sample for areas of a storm you can more predicatively than other places? >The events are too rare, to unpredictable and too powerful to be practically harvestable. But the distribution isn't uniform if you look at occurrence of where it happens on earth, some places are more likely to form storm systems vs others.