The Troubled Quest for the Superconducting Wind Turbine(spectrum.ieee.org)
spectrum.ieee.org
The Troubled Quest for the Superconducting Wind Turbine
https://spectrum.ieee.org/green-tech/wind/the-troubled-quest-for-the-superconducting-wind-turbine
17 comments
Holy crap, it's a magnetic version of a harmonic drive!
https://en.wikipedia.org/wiki/Harmonic_drive
https://en.wikipedia.org/wiki/Harmonic_drive
Wow! And that video is over eight years old.
Has anyone seen on in a production device?
Has anyone seen on in a production device?
The first illustration is terrible. It's making multiple comparisons at the same time, the most prominent being the difference in blade size, which isn't variable between the 3 technologies the article is actually talking about. Whilst at the same time making it harder to see the pertinent data, differences in the generator size and weight.
I'm just gonna trot this out one more time: https://en.wikipedia.org/wiki/Vaneless_ion_wind_generator
very simple design (it's basically one half of a Lord Kelvin's Thunderstorm turn on it's side and powered by wind instead of gravity.)
very simple design (it's basically one half of a Lord Kelvin's Thunderstorm turn on it's side and powered by wind instead of gravity.)
This article reminded me of the concept or an airborne turbine [0]. Interesting to think what would happen if we had thousands or more of these immersed in jetstream somewhere, siphoning terawatts. Environmental impact could be noticeable (or not) [1].
[0] https://en.wikipedia.org/wiki/Airborne_wind_turbine [1] https://en.wikipedia.org/wiki/Jet_stream#Possible_future_pow...
[0] https://en.wikipedia.org/wiki/Airborne_wind_turbine [1] https://en.wikipedia.org/wiki/Jet_stream#Possible_future_pow...
Does anyone know why the rotation force is not transferred mechanically to ground level?
Hydraulic transmission has been proposed.[1] That would move the generator to ground level. But even its enthusiasts say the hydraulics won't scale beyond the 500KW level. This article is about scaling to 20MW or so.
Vestas is up to 9.5MW for their biggest offshore model. It has a gearbox; it's not direct drive. Probably because at that scale it only turns about 10 RPM.
[1] https://www.machinedesign.com/energy/hydraulic-wind-turbines
Vestas is up to 9.5MW for their biggest offshore model. It has a gearbox; it's not direct drive. Probably because at that scale it only turns about 10 RPM.
[1] https://www.machinedesign.com/energy/hydraulic-wind-turbines
I wondered about that, longer blades, lower RPM means very slow RPM which means massive magnetics. But gears are problematic as well. Low speed means high torque which also mean large heavy gears. ($$$)
Probably because housing a 150m+ transmission capable of mechanically transferring 10MW+ would make the tower far more expensive than what you'd save by not having to support the weight of the motor.
Exactly. Other concept studies have looked at driving mechanical pumps to feed hydraulic pressure into a network [1], or (at a very small scale) mechanically drive a desalination unit [2]. As mentioned in the article, the problem is not figuring out if these concepts can work (usually they just do). The question is always: what will it cost compared to what we have now, and how much more complicated will the wind turbine become?
[1] https://www.tudelft.nl/en/2017/tu-delft/possibility-of-hydra... [2] https://www.treehugger.com/clean-technology/drinking-with-th...
[1] https://www.tudelft.nl/en/2017/tu-delft/possibility-of-hydra... [2] https://www.treehugger.com/clean-technology/drinking-with-th...
Just adding to what other people have said with some bits from the article and my ramblings:
>energy losses in mechanical gears. These losses can be 1 to 2 percent per stage, and many turbines have three gear stages, explains Powell.
In order to have the generator at the bottom you would need at least 2 things, assuming your generator/gearbox is now going to stand vertically within the tower and take its drive directly in. 1) a differential to change the motion axis, positioned at the top. 2) a shaft that either hangs or is supported at intervals, for the length of the tower.
A couple of issues I can imagine with this, The diff at the top needs to be of reasonable size. In mining and heavy industrial equipment 10MW gearboxes aren't unheard of, but the article also mentions that the turbine speed is quite slow, so the torque will be extremely high to result in that 10MW.
The 1-2 percent loss of this 'stage' will also necessitate a cooling system at the top separately just for this diff as 2% of 10MW is 200kw of waste energy (heat) that has to go somewhere.
However, an advantage is that you can gear the diff to spin the vertical shaft faster reducing the need for some of the primary gearbox gearing and reducing torque load of the shaft.
The shaft supports will also sap power as you have the weight of the shaft now on one or more bearings. The way I designed this mentally was having the shaft split in to sections, perhaps 5m each so 30 sections, as installing a continuous 150m shaft isn't realistic. Each shaft section with its own bearing for servicing and maintainability. This could be reduced to 1 bearing per 2-3 shafts based on losses vs ease of servicing a 15m section over a 5m section.
Other approaches that don't include a shaft could be considered, hydraulics, belts even.
>InnWind then had to add even more steel because of an unexpected resonance in the structure. This problem resulted from the mass at the top of the tower being so light that when the 41.7-metric-ton blades swung past the tower, they strained the structure at a frequency that was too close to its natural frequency.
Issue 2 raised in the article is that having the mass at the top offsets the weight and harmonics of the blade, moving all that junk to ground level may mean adding ballast weight to counter vibration.
/rambling thought experiment
>energy losses in mechanical gears. These losses can be 1 to 2 percent per stage, and many turbines have three gear stages, explains Powell.
In order to have the generator at the bottom you would need at least 2 things, assuming your generator/gearbox is now going to stand vertically within the tower and take its drive directly in. 1) a differential to change the motion axis, positioned at the top. 2) a shaft that either hangs or is supported at intervals, for the length of the tower.
A couple of issues I can imagine with this, The diff at the top needs to be of reasonable size. In mining and heavy industrial equipment 10MW gearboxes aren't unheard of, but the article also mentions that the turbine speed is quite slow, so the torque will be extremely high to result in that 10MW.
The 1-2 percent loss of this 'stage' will also necessitate a cooling system at the top separately just for this diff as 2% of 10MW is 200kw of waste energy (heat) that has to go somewhere.
However, an advantage is that you can gear the diff to spin the vertical shaft faster reducing the need for some of the primary gearbox gearing and reducing torque load of the shaft.
The shaft supports will also sap power as you have the weight of the shaft now on one or more bearings. The way I designed this mentally was having the shaft split in to sections, perhaps 5m each so 30 sections, as installing a continuous 150m shaft isn't realistic. Each shaft section with its own bearing for servicing and maintainability. This could be reduced to 1 bearing per 2-3 shafts based on losses vs ease of servicing a 15m section over a 5m section.
Other approaches that don't include a shaft could be considered, hydraulics, belts even.
>InnWind then had to add even more steel because of an unexpected resonance in the structure. This problem resulted from the mass at the top of the tower being so light that when the 41.7-metric-ton blades swung past the tower, they strained the structure at a frequency that was too close to its natural frequency.
Issue 2 raised in the article is that having the mass at the top offsets the weight and harmonics of the blade, moving all that junk to ground level may mean adding ballast weight to counter vibration.
/rambling thought experiment
That would be way more complicated/lossy than turning a coaxial generator.
In a sense, a good wind turbine has four moving "parts". The rotor axis and the actuation necessary to change the blade pitch. I'm no expert, but I don't think there's anything else.
In a sense, a good wind turbine has four moving "parts". The rotor axis and the actuation necessary to change the blade pitch. I'm no expert, but I don't think there's anything else.
These generator+gearbox combo's operate at efficiencies (mechanical to electrical power) in the order of 80-90%. I would assume it will be quite challenging to do that with a 100m long mechanical transmission system handling 5-10MW. I wonder how much maintenance such a system would require too.
>> in the order of 80-90%
I've been in the EV world for a while now. We used to do 100-200kW drive systems where motor+inverter would be 90-94 percent efficient. Adding a single stage gear to that would cost another 1-2 percent efficiency loss.
The whole time I was reading this I kept thinking we could throw 100 electric vehicle drives on a giant ring gear for a total mass under 10k-tons with no super conductors or anything too fancy. The problem is that the EV systems are not rated for continuous operation at higher power levels. You only use full power for acceleration - driving even at highway speeds doesn't take that much. OTOH one would expect good airflow in a wind application.
I think there might be room for a change of approach in the wind turbine area.
I've been in the EV world for a while now. We used to do 100-200kW drive systems where motor+inverter would be 90-94 percent efficient. Adding a single stage gear to that would cost another 1-2 percent efficiency loss.
The whole time I was reading this I kept thinking we could throw 100 electric vehicle drives on a giant ring gear for a total mass under 10k-tons with no super conductors or anything too fancy. The problem is that the EV systems are not rated for continuous operation at higher power levels. You only use full power for acceleration - driving even at highway speeds doesn't take that much. OTOH one would expect good airflow in a wind application.
I think there might be room for a change of approach in the wind turbine area.
https://www.youtube.com/watch?v=EAELukfr2oY