The VAWT (Vertical axis) styles are not as efficient on the ground or as practical when they get large. One significant reason is that the wind is stronger at height. Another is the material strength needed to hold the blades in place at operating speed is higher because the full blade is at the periphery rather than just the blade tip.
The VAWT (Vertical axis) styles are not as efficient on the ground or as practical when they get large. One significant reason is that the wind is stronger at height. Another is the material strength needed to hold the blades in place at operating speed is higher because the full blade is at the periphery rather than just the blade tip.
Lots of choices out there including floating arrays of smaller turbines that pose less bird risk and single points of failure.
Running a shaft down to transmit the full power will be expensive, either it has to be very rigid for slow sped and high torque or very well balanced and supported if at high speed. I would guess (as an electrical engineer with a mechanical engineer father) that the numbers have been run and the electrical cable down the tower is cheaper in some calculation that is used to make the choice. Sure it might cost more over decades of maintenance or even during installation but not enough to be able to swing the bean counters.
Having the extra gearbox and alternator mass at the top will also reduce the resonant frequency of the tower vibration and reduce the effect of the blade mass on tower vibration.
My gut feel is that in spite of issues with the current system it is the best engineering choice from an investor point of view. There is probably room for improvement on many aspects but they would increase costs.
The VAWT (Vertical axis) styles are not as efficient on the ground or as practical when they get large. One significant reason is that the wind is stronger at height. Another is the material strength needed to hold the blades in place at operating speed is higher because the full blade is at the periphery rather than just the blade tip.
Lots of choices out there including floating arrays of smaller turbines that pose less bird risk and single points of failure.
Running a shaft down to transmit the full power will be expensive, either it has to be very rigid for slow sped and high torque or very well balanced and supported if at high speed. I would guess (as an electrical engineer with a mechanical engineer father) that the numbers have been run and the electrical cable down the tower is cheaper in some calculation that is used to make the choice. Sure it might cost more over decades of maintenance or even during installation but not enough to be able to swing the bean counters.
Having the extra gearbox and alternator mass at the top will also reduce the resonant frequency of the tower vibration and reduce the effect of the blade mass on tower vibration.
My gut feel is that in spite of issues with the current system it is the best engineering choice from an investor point of view. There is probably room for improvement on many aspects but they would increase costs.