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How on earth would this work?!

DrPizza

DrPizza

Administrator Elite Member Goat Whisperer
flying windmills??

I'm left scratching my head, wondering how this would work??? Is this just one more among a long list of "inventions" that disobey the laws of physics?

I mean, it'd be like an airplane deciding to generate its own electricity by having a couple extra props attached to generators. When the air pushed against those props, the other props would just have to work that much harder to keep the plane aloft.

Something tells me I'm not looking at something the right way though... What am I missing??
 
Aye, there is definitely something going on with unbalanced forces and moment arms (torque) on the craft.

Now the vertical force (lift) required to hoist the thing into the air just needs energy to move its own mass thru the distance required against the force of gravity.

If using helicoptor like lift design then this energy is independent of the lateral windspeed (the wind we want to tap for generating electricity) so we could see where it would be feasible for there to be enough energy generated by lateral windspeed to outproduce the energy required for lift provided the mass of the system was below a threshold (defined as the maximum allowable mass of the windmill before harvesting lateral winds of X mph velocity is feasible).

Were this the end of the energy balance equation then my suspicion would be that yes it is feasible provided you can find the right magic materials to provide the minimal mass necessary to win the energy budget of lifting the thing into the air while harvesting the energy from the lateral wind.

Ah but let's consider the harvesting...a windmill's propeller rotates because it is converting the force normal (perpendicular) to the face of the blade into a lateral force (by virtue of the blades angle of tilt) causing rotation. Super. So for a free floating object this would mean the force on the blades is pushing the windmill in the direction of the wind...common sense...so what keeps the windmill stationary?

This is where you lose the energy balance argument. You can't "push" against the wind with any less energy than the wind is pushing against you. So you can't use the wind, which is pushing against you, to generate more energy than you need to push back against the wind.

Eventually your windmill will be moving with the wind in its drag-limited terminal velocity. Bye bye windmill.

Perpetual motion machine. QED.
 
Originally posted by: Idontcare
Ah but let's consider the harvesting...a windmill's propeller rotates because it is converting the force normal (perpendicular) to the face of the blade into a lateral force (by virtue of the blades angle of tilt) causing rotation. Super. So for a free floating object this would mean the force on the blades is pushing the windmill in the direction of the wind...common sense...so what keeps the windmill stationary?

This is where you lose the energy balance argument. You can't "push" against the wind with any less energy than the wind is pushing against you. So you can't use the wind, which is pushing against you, to generate more energy than you need to push back against the wind.

Eventually your windmill will be moving with the wind in its drag-limited terminal velocity. Bye bye windmill.
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The devices they want to put in the air are tethered to the ground, preventing them from simply drifting away. I initially assumed they were intending to keep these things up by utilizing that tether and a wing to generate lift (essentially like a kite), but from the pictures on their site, I take it they are not.

That being the case, it is conceivable that they could actually put these things in the air and keep them there. Plausible, after factoring in the hardware they would need to put on it in order to try to generate electricity? No idea. Plausible that they could generate a substantial amount of electricity? No idea.
 

Yes, it's my understanding that they would be tethered to the ground.

Once lifted into place, they are supposed to "fly" like kites in the constant winds of the upper atomsphere. I gather that the blades would be controlled in a way to generate enough lift to keep the windmills flying (and the tether provides the force to keep them from straying horizontally), while the rest of the rotational energy went to turning the generators to produce electricity that runs down the tether to the ground.

 
Weird idea, but it could be done. I can't imagine what it would take for them to produce the amounts of electricity they claim, though. But I haven't really thought about it.
 
The Robert's windmill has contra rotating blades to reduce the torque on the system, and stop it twisting as much. The larger prototypes will have 4 blades for safety; preventing the flying electric generator from plummeting to the ground should a motor/blade fail.

According to their figures, one flying windmill rated at 240kW with rotor diameters of 35 feet could generate power for less than two cents per kilowatt hour--that would make them the cheapest power source in the world.
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What I don't get is that a normal 10 metre blade turbine should produce about 50kW; since the flying windmill has 4 rotors the increase in efficiency isn't that great. (Unless they mean each rotor creates 240 kW in which case they should mind their plurals and state total output as well)

You might also want to have a look at this site Magenn. The technology seems more mature although cost is still in the region of 20 cents per kWh.
 
Originally posted by: dkozloski
Originally posted by: BladeVenom
That's going to be a very long and heavy tether.
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Childs play compared to the tether they're going to need with the space elevator.
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That was actually my first thought when I saw this story a while ago, the weight I mean.

Not the same thing as the space elevator though dkozloski, as the elevator is supported by orbiting FROM space. It isn't actually a tether, but more like a rope held up from above. A theoretically elevator is "held together" by the structure itself, and supported from space. This thing actually needs to provide enough LIFT to keep the body and the tether together, which is not nearly the same thing as just orbiting.

(I hope that made sense)
 
PlasmaBomb:

The point of these windmills is that they use upper atmosphere winds, which are much stronger. They'll produce more energy than other windmills, even after factoring in the power needed for lift.
 
What some of you are saying about using energy to stay aloft doesn't really apply here. It's a kite, and a kite doesn't require propellors to stay in the sky. The angle of the kite itself is what creates lift and the string keeps it from flying away. Why should it function any differently if you strap some propellors onto the kite?
 
The main thing I worry about is this - the tether connecting it to the ground.

I can't imagine one light enough that would work. They'd have to be pretty long...
 
Originally posted by: firewolfsm
Carbon nanotube rope most likely
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The technology doesn't exist. In fact, the technology to produce even "regular" carbon fibers (microscale diameters) 15,000 feet long doesn't exist. The oil companies have been trying for some time because they would love to use them to anchor deep sea platforms, but nothing has worked as yet.
 
It occurs to me that you might as well build it as an aerostat. Instead of flying it like a kite, why not attach it to a balloon to keep it up? This is, after all, what the southern US Tethered Aerostat Radar System is all about. Some data on the TARS from wikipedia:

Primary Function: Low-level, downward-looking radar; aircraft detection

Volume: 275,000 and 420,000 cubic feet

Tether Length: 25,000 feet (7,600 m)

Payload Weight: 1,200-2,200 pounds

Maximum Detection Range: 200 nautical miles (400 km)

Operational Sites: Yuma and Fort Huachuca, Ariz.; Deming, N.M.; Marfa, Eagle Pass, and Rio Grande City, Texas; Cudjoe Key, Fla.; and Lajas, Puerto Rico. Sites located at Morgan City, La., and Matagorda, Texas, are in a cold-storage configuration. Contract management office and logistics hub are located in Chesapeake, Va.

If you combine a kite-like design with a balloon I imagine you could limit the terminal velocity of the thing if it were to fall down and lift more stuff, all at the same time. Someone else will have to answer whether a decent turbine could be provided with a weight on the order of a couple of metric tons, though.
 
Assuming this thing could fly on its own, it seems to me it would still need a massive tether to transmit that much power to the ground. They don't say what voltage is being put out, but you would still need a big wire for 230kw. The tether would outweigh the aircraft.
 
Here is an idea I have been playing around in my head, why not have an array of blimps fixed to the ground through cables (assuming we can manage to reach them) the helium in the blimps will keep them afloat in the air and the cables keep the turbines fixed-partially always, then turbines pass the current generated through the cables?
 
The flying power generator we started talking about is in principle exactly the same idea as with the blimp, except they're saying that it's more effective to use rotors at the altitudes (and wind velocities) they're talking about.
 
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