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William K.
User Rank
Platinum
Re: That directed energy beam, a hazard?
William K.   12/22/2013 9:52:15 PM
NO RATINGS
78RPM, that is the reason for using really high voltages, because you are correct about the fact that big long wires are really heavy. So instead use thinner wire and much higher voltage. And run those cables from opposite corners maybe a hundred or 200 feet apart, or more. Using really high voltage is the only option that makes sense here.

78RPM
User Rank
Gold
Re: That directed energy beam, a hazard?
78RPM   12/21/2013 3:42:45 PM
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I was doing some calculations. If the conductors were copper, let's say 2.54 cm diameter, the weight of a cable 50,000 ft. long would be nearly 148,000 pounds which means that the tensile strength (50,000 lb./in2) of copper at the top of the connection would be pushed near its limit.  Add some strain from wind forces; add some metal fatigue, and the cable would break. Look out below. Silver is even heavier and softer. Feel free to correct my calculations. What advantage would there be to harvest either wind or solar energy at high altitude when we can do it on earth's surface?

William K.
User Rank
Platinum
Re: That directed energy beam, a hazard?
William K.   12/19/2013 12:22:34 PM
NO RATINGS
Elizabeth, the story was about platforms with multiple wind turbines that could be flown up to the desired altitude by driving the generators like motors, until they reached the higher windstream, at which point they would fly like kites, sort of. The challenge that everybody else was seeing was the insulation between thye conductors in the cables used to bring the power back down to earth. It would be a problem since big conductors are quite heavy, and so the solution would be to utilize much higher voltages. My proposal was to have multiple cables for the power, since the platforms would be quite large. Of course there is a bit of challenge in keeping multiple cables that are 50,000 feet long separated, but it seems like the very best approach.

I will attempt to visit the article in the link. 

My first two attempts failed to find it. Google must be blind.

Elizabeth M
User Rank
Blogger
Re: That directed energy beam, a hazard?
Elizabeth M   12/19/2013 10:28:25 AM
NO RATINGS
Yes, I think tethered drones do make more sense, William K. I may have even written that story--is this what you were referring to? http://www.designnews.com/author.asp?section_id=1386&doc_id=253968

Or perhaps it was something else, since that involves kites and not drones per se. I'd be interested to see that story if it was something different.

William K.
User Rank
Platinum
That directed energy beam, a hazard?
William K.   12/18/2013 4:17:47 PM
NO RATINGS
The concept of geostationary drone platforms is quite interesting. I recall a posting a while back in which some organization was planning to use tethered drones and bring the power down as high voltage in cables. That posting made a lot of sense, since the plan was for all of the wind turbines to be delivering energy, with the whole system flying like a kite, restained to one specific location by the cables serving both as anchors and as power transmission lines.

But if the captured energy were to be put into a directed energy beam that could be rather unsafe for anybody whom the beam happened to hit. And a free-flying platform will shift with the breeze a few times. Given that thye beam would need to be transmitting a whole lot of energy, quite likely in the hundreds of kilowatts, and given that would be concentrated in a fairly small area, any random wandering of the beam could be very lethal, at best. On the other hand it could be a fantastic "directed energy weapon" if it were able to quickly cook enemy troops. 

So I would seriously support a wired drone platform, but would consider the wireless platform to be absolutely foolhardy. 

Elizabeth M
User Rank
Blogger
Re: Drone Power
Elizabeth M   12/18/2013 6:01:19 AM
NO RATINGS
So just to let you know, I have contacted the founder of this company and asked him to take a look at the story and the comments to see if he might explain the business plan/technology a bit better. We didn't manage to speak before the story posted. Perhaps he has some answers for everyone, so let's see if he weighs in. Thanks for making this a lively discussion!

Elizabeth M
User Rank
Blogger
Re: Drone Power
Elizabeth M   12/18/2013 5:57:02 AM
NO RATINGS
So it seems there is a consensus on the wind turbine technology. I did receive an email from the company founder quite late after I contacted him (and after the story posted) so I can present these comments to him and see what he says. Perhaps he has an explanation for how the turbines might work.

Elizabeth M
User Rank
Blogger
Re: Drone Power
Elizabeth M   12/18/2013 5:55:25 AM
NO RATINGS
Thank you for your comment and perspective, FeynmanFan. I appreciate your opinion on this story and your informed analysis of the technology presented here. As for the viability of the technology New Wave plans to develop, you would have to contact the company founders themselves and discuss that further with them.

78RPM
User Rank
Gold
Re: Drone Power
78RPM   12/17/2013 3:29:47 PM
NO RATINGS
@FeynmanFan, I agree with your analysis. It's as simple as Newton's Laws of Motion, not to mention entropy. You cannot extract more wind energy than you consume for an untethered system. These drones can't harvest wind energy.

While we're talking about it, has anyone done a study or calculation to see if harvesting wind energy (on the ground) as a major energy source worldwide would slow down the rotation of the earth or affect its tilt on its axis appreciably?

FeynmanFan
User Rank
Iron
Re: Drone Power
FeynmanFan   12/17/2013 12:38:22 PM
NO RATINGS
Hi Elizabeth,

Well as I mentioned earlier you cannot harness wind energy with an unthered platform.

Energy can only be extracted by changing the momentum of the airstream which requires a force. An equal and opposite force on the platform will accelerate it until it drifts with the airstream - therefore no steady-state power generation.  Maintaining the platform position with the other rotors will consume more power than is generated in the turbines.  At best the craft could weave between airstreams of differing velocities and use its own inertia to react against the airstreams although I doubt the 400 square meter flat platform is aerodynamic enough to do this and survive.

The thinking behind this project is flawed on so many levels and yet you are providing media exposure to a company who plans to start a Kickstarter campaign to raise around £300,000 (US$500,000) based on a paper proposal and muddy thinking.

You owe it to your readership to be more discerning.

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