Harvesting Energy in the Sky 261
withoutfeathers writes "The Economist magazine has an article on Flying wind farms. Mind you, we're not talking about ordinary, terrestrial windmills here. We're talking about actual airborne — up to 10km in the sky — wind farms intended to harvest the immense supply of energy in the jet stream. On the surface, the idea seems a little eccentric but, in fact, San Diego (California, US) based Sky WindPower has, apparently, thought their concept through pretty thoroughly and believes they can not only make this work, but do so profitably. The article discusses several other ideas for high-flying wind farming including a Dutch proposal to use pairs of kites to drive a generator."
Would this cause any problems with the jet stream? (Score:5, Interesting)
Is it even possible for us to tap enough power from the jet stream (or other high altitude winds) to cause problems?
Much more realistic idea than kites. (Score:3, Interesting)
Re:Hmm (Score:5, Interesting)
In the Jet Stream... (Score:5, Interesting)
You know what else tends to reside in the path of the jet stream? Storm systems.
I bet that these things would make excellent conductors for lightning. Take them down when storms approach and put them back up afterwards? Probably not feasible.
Then again, they would probably build up a heck of a static charge themselves just with the wind flowing over them.
Oh yeah, would ice build-up be a problem? Maybe not at the windmill itself, but on the tether, perhaps.
Seems to me there's a few (obvious) technical hurdles to address, first./p.
Re:In the Jet Stream... (Score:5, Interesting)
The tethers will keep these continuously grounded, so any static is just some bonus power. The teathers will be great lightning rods, which will probably be more power at once than can be made usable, but it is entirely possible to design them so it's not destructive either.
Ice build up would have to be dealt with, but, hey, it's a power station, if nothing better, heat the cable.
There are definitely technical hurdles to overcome; this is at the conceptual daydreaming stage so far. But the obvious problems seem entirely doable to me.
I'd say the big issue is if you can get reliability good enough that maintenance costs don't kill your cost effectiveness.
Capturing Lightning/Static Electricity (Score:3, Interesting)
Well, the technical hurdle is capturing the energy from a massive electrical discharge and then releasing it in a controlled form. You can't just send it through some super transformer to knock down the voltage because, even if you could, the voltage rise/fall time is so fast that the inductive impedance of the transformer would probably make it quite ineffective. Even if you could down convert the voltage of the lightning, you'd have difficulty building a device that could accept such a large inrush of current in such a short period of time. Direct application of the electrical energy is most likely out.
I would think that a solution for capturing this energy would reside in a less direct solution, such as dissipating the energy into a medium (i.e. specialized oil, or vaporization of a liquid) as heat, then using standard thermodynamic heat flow to mechanically spin a turbine or something. There's several forms of energy conversion in the whole process of something like that, but it would be done to better manage the storage and release of the captured energy.
Of course, the next problem is finding a relatively abundant source of atmospheric electrical discharge to make something like this economically feasible.
Re:Well (Score:2, Interesting)
Re:wind power is overrated (Score:3, Interesting)
By necessity, any generation of electricity is going to remove energy from our environment somehow. (In the case of fossil fuels, this is stored chemical energy, but it still came from somewhere.) Hydroelectric power, the big (and relatively environmentally friendly) energy producer where I live, requires a whole river to be diverted. This wind power proposal is more like sticking your toe into a fast-moving stream. It seems fair to assume (so long as we lack evidence to the contrary) that it is unlikely to have a significant effect (good or bad), and it would replace technologies with known negative effects.
Your argument seems to me no different than one which says we should not harness electricity from tidal changes because it contributes to tidal locking between the earth and moon. In both cases, the amount of energy likely to ever be extracted is only a very small portion of the total energy available.
Forget the tether... (Score:4, Interesting)
Re:In the Jet Stream... (Score:3, Interesting)
A typical lightning strike is around a thousand kWh. That'll keep a 100W light bulb lit for a few months, but given that your air turbine gizmo will likely only get a few strikes per month, it's hardly worth the effort to capture considering how much wind energy it'll be capturing during that time.
It's best to just treat the lightning a like a nuisance and try to dissipate it safely.
Re:wind power is overrated (Score:3, Interesting)
Not true at all. While everyone likes to paint the Americans and other first-worlders as ruining the planet, the third-worlders are certainly doing their part as well.
Look at a satellite image of Haiti, and compare it to its neighbor Dominican Republic. Haiti is dirt-poor, but they're busy chopping down every tree on their side of the island, causing all kinds of problems with erosion and destruction of the marine environment offshore.
In Brazil, they're busily chopping down the rainforests to make way for agriculture. The rainforests are a huge carbon sink and change a lot of the CO2 in our atmosphere to O2, plus they have an enormous amount of biodiversity, with potential medicines waiting to be discovered there.
Pollution has become an enormous problem in places like China and Vietnam because of the rapid industrialization there.
It's not just resource consumption, but also resource management. At least the first-worlders have put some limits in place on pollution (especially the toxic kind, rather than CO2), which the third-worlders happily ignore in their ignorance.
The only way our planet could healthily support more people at a decent standard of living is for everyone to live peacefully in arcologies or other high-density utopian environments. The only way this will happen is if scientists can genetically modify all future humans to no longer be human: to not fight, to not be greedy or evil, to not be intolerant or force others to yield to their will, etc. Basically, we need to all act like ants, working only for the common good and completely ignoring any personal needs or wishes. Good luck with that.
Re:Hmm (Score:1, Interesting)
Of course if you added some sort of parachute that would deploy at some predefined altitude and minor steering thrusters I guess you could have them attempt to home in on, and crash on, some beacon or GPS coordinates.
Re:In the Jet Stream... (Score:2, Interesting)
Re:wind power is overrated (Score:2, Interesting)
Secondly taking energy out of the antmosphere is a great thing. The global warming (I there is such a thing because New Zealand has been cooling 0.9 degrees centigrade over the last decade)puts energy into the atmosphere and windmills take it out again. Hey it's energy recycling!
I'd be surprised if pilots are allowed to fly aircraft themselves in a decade from now. So avoiding a few lousy powerstations won't be a problem.
Icing? No problem. The cables are made of aluminium and as such not a great conductor. To keep the weight down these cables need to be thin hence they probably are going to be hot or at least warm anyway.
Weight? Yeah to total killer of this concept. There is no hope in hell they can build cables light enough to transfer energy to the ground while keeping the kite tethered. However, I can think of a variation of this idea. They could use the tether as a method to transmit rotational energy to the ground. A ground based pulley system and a 20 km long loop of fancy nanotube super light cable running as a chain between the airborne windmill and the ground. The generator remains firmly on the ground. This reduces the weight of the airborne system a lot while the power station can now stay aloft at very low wind speeds. Ow, bugger it. I made a picture. Here have a look,
http://vandinther.googlepages.com/home [googlepages.com]
I don't even think such a power station would need to be in the jetstream to function thanks to it's much lower weight. Of course if the cable breaks then you are uh... well actually no. The return cable can be just slightly longer. Breakage of the cable can be detected by a sudden reduction of tension on the drums and the return cable can immediately be locked in place while electronics adjust the rotors to reduce the tension to a minimum.
Re:Be careful (Score:2, Interesting)
Re:Capturing Lightning/Static Electricity (Score:3, Interesting)
Build a very large capacitor with it's positive pole at the anchor point. If you build it large enough you might be able to keep it from melting. Large glass Leyden jars? A cap is a cap (you should see the ones I used to build my Interociter) but the methods, conductors and dielectrics can differ widely. Surround the base with induction coils to grab lumps of current that leave the cable. If necessary dump the spare voltage as heat into a bank of aluminium or other highly heat-conductive metal.
This may or not be practical, but for a device worthy of a 1930's Popular Mechanics cover it would be retro-superb to look at.
Re:"Uncontrolled?" (Score:3, Interesting)
And what happens in the meantime to the 10km of (pretty heavy) power transfer and anchoring cable?
Re:"Uncontrolled?" (Score:3, Interesting)
"bump-starting" eh?
Everyone I know calls this simply, go figure, a "windmilling prop". You don't even have to go into a dive - windmilling speeds with no power on even something as small as a C172 at best glide - around 60kts - is over 1000 RPM, which is more than enough to start the engine (its capable of starting at less than 100 RPM).
And for the other poster here that thinks you have to "reverse the pitch" of prop blades to get it to windmill...nope. You can do this with a prop that can't change its pitch at all. It's a different mechanism than helicopter auto-rotation because in a helicopter the airstream is flowing opposite the desired direction to create lift when falling (which is why pitch must be reversed); in an fixed-wing aircraft the airstream is always flowing in the correct direction to create thrust.
This is big thinking. How about something small? (Score:3, Interesting)
When I was a kid, I got one of those big, plastic "bat" kites. (They were new on the U.S. toy market at the time, so that tells you how old I am.) I found it horrifically unstable, so I attached a tail made of torn cloth and other stuff. It was quite long and weighed several pounds, making the kite a pain to launch. Once it had gained some altitude, though, it was stable and pulled steadily. I ran out of kite twine, so I drove a stake in the ground and tied it off. Then I rooted around in the garage and found a giant spool of 100lb test fishing line. (Why we had it since it had been years since we'd lived near the Gulf Coast and gone offshore fishing, I didn't know.) I attached this new line to the kite string and let it play out. Quick as a wink, that kite was hundreds of yards high, just hanging there, pulling hard and steady. My older sis had a party that night and all the high school boys wanted to show off how manly they were, so they pulled in the kite for me. They had to work hard for over an hour, pulling it in as fast as they could, to get it to the ground. They were tired, sweaty, and pissed at me by the time they were finished.
I haven't thought about that episode in years. I wonder, though, if it would be possible to put up a fairly large kite to an altitude of just a few hundred yards and keep it aloft (semi-)long term with some sort of small wind generator hanging from it (I know that kite I launched in my youth could have held up 20 or 30 pounds, easily, once it was in the air.) and a small cable leading back to the ground. I live in a fairly mild climate and could pull it in if the weather got bad. I'm just wondering if this could produce enough energy to bank to some batteries that the exercise would be worthwhile.
I know lots of people have tried to go off the grid using power generated from small, often home-built terrestrial windmills. Because the wind at ground level is capricious, they need to feed big battery banks to tide them over the inevitable down time. I'm just wondering if putting a small windmill up at an altitude where air movement is more reliable could actually be a workable approach to the problem.
Of course, this is all just an unformed idea from someone who knows nothing about this stuff. For all I know, the wind at 1000 feet is no more reliable than the wind at ground level and that's why TFA is talking about getting up into the jet stream. Still, it's an intriguing idea to me.
So who wants to be the first to shoot it down?
(Yes, I love bad puns, too.)
Butterflies (Score:4, Interesting)
What you said about the Butterfly Effect is correct but deals with the impact of small random fluctuations on a chaotic system. In this situation the planned alteration is highly non-random (a consistent reduction in energy potential of the jetstream), and the inevitable consequence of success is a gradual and significant increase in the magnitude of the change. The Butterfly Effect is not the correct model for non-random state changes of increasing magnitude.
In other words, the quoted person is thinking about a valid concern, but used the wrong model to express it. The concern is still valid however. Will our actions disturb a delicate balance in nature of which we are not yet aware? We just don't know. Experiments of this scope are not the ones that you want to go the wrong way, so I sincerely hope that this company and the government spends as much time determining how to calculate the limit of what we allow ourselves to pull from the jetstream as we do figuring out how to do it.