In June, I drove across North Texas on I40 and marveled at the scale of the wind turbines. At those scales (Panhandle I and II generate 400MW according to Wikipedia), I suspect that per turbine materials cost is less of a limiting factor than site acquisition and infrastructure installation. I also wonder about modeling multi-unit installations as shifting wind direction and intensity changes local conditions and moves one kite turbine relative to its neighbors.
As I drove the landscape, I was looking at the spacing between turbine rows and thinking about dirty air and laminar flow (why Texas is a good place for wind farms). Probably because the previous week I'd watched a bit of Americas Cup on TV with a friend who sails.
In the long run, it might be possible to achieve higher energy density with kites due to dynamic repositioning. The economics of increased complexity for higher density might work out, but I suspect that the density would need to be significantly higher while maintaining similar consistency of output. Feathering a fixed turbine offline in high wind and spinning it up again as conditions become favorable looks quicker than cabling in and cabling out kites in similar conditions.
is "dirty air" nothing more than particulates suspended in the wind gusts or is it some special term of art? Just curious, is there a relationship between dirty air and laminar flow?
This may not be 100% accurate in nomenclature, but it gets the point across. Laminar flow is uniform and very easy to model mathematically, hence the reference to its "clean-ness" (e.g. clean [simple yet functional] design, clean [elegant] math proofs, etc). Its opposite: turbulence. laminar:turbulent::clean:dirty. You get turbulence/wake when there's something upstream of you disturbing the flow patterns. Air has less potential energy in it once it has been disturbed (the random motion of turbulence detracts from it's ability to generate pressure differences via flow manipulation). Riding in dirty air happens when the rich man's yacht in front of you sails upwind of your own personal rich-mans-yacht. Your vessel can still sail, but will sail a little bit slower, due to there being less available energy in the wind for you to tap into. This becomes a problem w/ turbines for obvious reasons (ask yourself why they don't just put multiple turbines all on a spoke for cost-of-installation savings, or even why they always seem to choose 3-bladed turbines [a very cool/interesting mathematical optimization problem!]).
Turbulence isn't always energy robbing, e.g. drafting in cycling and auto racing and distance running. Though it is hard to operate a sailboat like that...for what it's worth, my friend has a Sunfish these days.
The difference is which direction the energy is flowing. In sailing, you're extracting wind energy into kenetic energy. In drafting, you're expending energy from some other source to overcome the resistance of the air you're displacing to maintain your kinetic energy.
Most of the soft kite designs target this space, i.e. small generators for disaster areas and war zones. Soft kites aren't anywhere near as efficient as hard wings, but they sure pack up small.
Good video. They said costs could one day get down to $50 per MWh.
We already have solar plants selling at around $30 per MWh, so that doesn't seem like it will be a major source, although it has the potential to run all day and all night, unlike solar.
I feel like a broken record (to myself) because every time I see these concepts I immediately conclude they have no viable commercial future and are a waste of everything except enthusiasm. That's too negative, because that's how some of the old coal guys still see wind in general, but it's not completely crazy. History shows that something like this will get 5-10 years of development money, make a small scale working concept (maybe), and then go nowhere.
I guess I don't know what the answer is. Pursuing new ideas is worthwhile, but I don't expect this company to have real commercial success.
Welcome to innovation and human progress. This is how it works, lots of experiments, a few winners. It's impossible to know what will win and what won't, so our goal should be to get as many meaningful tests going as possible.
There's plenty of technologies that we are using today that previously failed. Like touch screens, now they are everywhere. And pretty much ever single technology had naysayers saying it wouldn't work for one reason or another.
And yeah most of the time the naysayers are right. Most attempts to innovate fail.
But maybe in 20 years these could completely replace traditional wind turbines and people will see them as the non-viable technology.
We don't know. Hence the need for research and development.
The history of "innovative" renewable energy development ideas of this general type over the last 15 or so years. Wind energy is my field, and I pay close attention to these ideas because I find them interesting. It's also why I'm so negative at this point: exactly zero of the ideas I've looked at have become commercial, and very few are still in active research. Most have quietly died.
I'm not remotely disagreeing with the general need for research and development. But I am firmly of the opinion that it should be research and development, not something planned to go from concept to commercial with an aggressive timeline like this.
Highly related: https://x.company/makani/ founded by Don Montague, one of the Kiteboarding pioneers - likely the first one to create software to design kites and windsurf sails.
What they don't mention is that Makani has thoroughly proven that the concept is not viable. The wing-on-a-string is too unstable and too expensive to compete with plain old wind turbines.
Please also remove the unsourced (and untrue) claim about the present, too!
I wrote a thesis ten years ago which examined the engineering and economics of a more simple kite/glider pair system. Aerodynamically, it can be stable and self-correcting, which I modelled and prototyped, but this may not be an optimal design and launching is hard due to lower (and different direction) ground wind and boundary layer issues.
The drone-like addition adds control complexity, but appears to ease take-off and can probably reduce strain in flight and improve efficiency, despite the aerodynamic cost.
Tower wind turbines have enormous costs and engineering trade-offs: the generator is in the nacelle up high, adding structural cost to the tower, which, at 150m+ nowadays, is a big deal; not to mention the rotors which span the area of a sports stadium. This doesn't scale, whereas kites do, because the tower/blade height/length cost is gone, the generator sits on the ground, and can be bigger (easy access, cheaper, heavier magnets, among other benefits).
Maintenance (and finance of turbine project bearing this in mind) is huge. Servicing an offshore turbine is weather limited and expensive even if you can get there. For kites, just reel them in by pulling more power off the generator to wind in the kites. If they are offshore, then sail the boat (?autonomously) back to a harbor. The list goes on and on, and amazing possibilities open up with a moment's thought.
Agreed with responder that it is early days for the technology, but I expect strong progress through up learning curve from this early stage. Good luck Makani!
I've shared an office space with Andreas and Gustaf for some time in Copenhagen (they're currently located in the great Founders House workspace). They're an awesome, extremely passionate team. It's been great fun seeing them work on the prototypes, and sitting in a bit, asking a bunch of questions, and Andreas sharing everything he knows about building drones, and all the cool tips he's willing to share.
If you think drones are loud, wait until you've heard an industrial kite/drone combo take off in an empty office space.
I would think that the maintenance and cost to constantly (re)deploy would negate the earnings.
If its not windy enough, you have to take them in. Too windy or rainy, then pull the kites back. Wing is ripped or bow is cracked from wind or sun damage, time to rebuild.
This happens automatically, so there is no real direct cost. It of course requires pretty sophisticated autonomous control systems, but the cost of developing that is amortised.
Regarding the cost of re-launching, that is one of the things they carefully model in software. For brief pauses in the wind it's cheaper to just stay aloft under grid power. These wings are more like a sailplane than a jumbo jet; keeping them in the air probably takes less power than you would think.
Kite Power Systems (http://www.kitepowersystems.com/) came to give a talk to the Institute of Physics in Cambridge earlier this year. They use a dual kite system where one kite is generating whilst the second is being pulled back in, and having demonstrated a 40kW system are about to deploy a 500kW system.
Oh okay. The video on the site implied they'd be taking the devices into deep sea environments. I guess there's still restrictions on where they can be used.
They are (for some values of deep) - KPS is looking at deployment offshore, where the tether will be less of an issue, they can go to scale and the wind is more reliable.
The kites are expected to be cheaper to maintain and install than traditional turbines, and can be mounted on old turbine bases.
If you mean how to turn the energy in the wind into electricity in the first place (rather than transporting it to the grid) there are two basic ways:
Ground generation, where you let the kite unwind the tether and have generator connected to the spool. Occasionally you need to expend energy to wind it back up, but this can easily be made work out as a net positive.
Airborne generation, where you have small turbines with generators on the wing and lead the power down through the tether.
What happens when: there is no wind, a flock of geese crash into it, the cable snaps, etc? Better keep these things away from buildings or it will be like 9/11 all over again from multiple angles.
I see stories promoting kite energy harvesting every couple years. They never address (one of) the primary obstacles to a functional unit: transmitting the energy to the ground. They usually hand wave the problem by saying there will be a conductive tether, but they don't mention the challenge in designing a tether that is strong enough to hold the kite, while also conductive enough to transfer power, while light enough for the kite to stay airborne. The usual solution for ground based power transmission it to use a high voltage, but that requires significant insulation separating the conductors, usually air. Other materials tend to fail under high voltage. So they will be limited in maximum voltage, and be forced to have a larger diameter conductor. It would be too heavy and won't fly. Tldr; this is probably a scam.
Indeed, and both models are in development by different groups. I was responding to dietlbomb's comment that kite power proponents "never address" the problem of power transmission in the tether.
A scam? That's one elaborate scam! I mean you have some 40 organisations around the world working on kite energy, including Google X and several leading universities. It's almost like it would be more impressive if it actually were a scam. But it's not of course.
As to the tether, people are of course aware of the requirements it needs to fulfil, you can even find calculations about it online. Making it strong enough and still light is not a problem, the challenge is really in combining a structural tether with a conducting cable. It is a challenge, true, but it's far from impossible and there are several possible designs.
New Scientist ran a story[1] in 2000, covering Bryan Roberts - a professor an engineer at the University of Western Sydney in Australia - and his plan to build 'gyromills' that used wind power to stay airborne, generated electricity, and transferred that back to ground with a tether. He'd built his first proof of concept device in 1986.
Hadn't heard much about it since, but am reminded of the proposal every time someone comes up with a comparable design -- to generate electricity at high altitude, where where winds are consistent and strong, and property prices are low -- using some lighter than air or self-propelled vehicle.
I see the gyromill plan has since morphed into a company SkyWindPower[2] and appears to look more like a 4-prop drone now, coincidentally.
Gyro mills are very fascinating, but I wouldn't have high hopes for them as sources of low cost energy. That is unless you could also fly the gyro mill in a crosswind manner.
Also it's important to note that the potential power output for any of these systems are proportional to the cosine of the tether angle, meaning that most of the advantage airborne systems to traditional turbines won't be so much that they can reach higher winds, but just the smaller amount of material required.
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[ 2.6 ms ] story [ 108 ms ] threadIt's an interesting approach.
In the long run, it might be possible to achieve higher energy density with kites due to dynamic repositioning. The economics of increased complexity for higher density might work out, but I suspect that the density would need to be significantly higher while maintaining similar consistency of output. Feathering a fixed turbine offline in high wind and spinning it up again as conditions become favorable looks quicker than cabling in and cabling out kites in similar conditions.
We already have solar plants selling at around $30 per MWh, so that doesn't seem like it will be a major source, although it has the potential to run all day and all night, unlike solar.
I was not able to find the numbers, but they would be interesting. Why not share them?
[1] http://minesto.com/
I guess I don't know what the answer is. Pursuing new ideas is worthwhile, but I don't expect this company to have real commercial success.
This process is the answer ....
There's plenty of technologies that we are using today that previously failed. Like touch screens, now they are everywhere. And pretty much ever single technology had naysayers saying it wouldn't work for one reason or another.
And yeah most of the time the naysayers are right. Most attempts to innovate fail.
But maybe in 20 years these could completely replace traditional wind turbines and people will see them as the non-viable technology.
We don't know. Hence the need for research and development.
I'm not remotely disagreeing with the general need for research and development. But I am firmly of the opinion that it should be research and development, not something planned to go from concept to commercial with an aggressive timeline like this.
Edit: removed unsourced claim about the future.
I wrote a thesis ten years ago which examined the engineering and economics of a more simple kite/glider pair system. Aerodynamically, it can be stable and self-correcting, which I modelled and prototyped, but this may not be an optimal design and launching is hard due to lower (and different direction) ground wind and boundary layer issues.
The drone-like addition adds control complexity, but appears to ease take-off and can probably reduce strain in flight and improve efficiency, despite the aerodynamic cost.
Tower wind turbines have enormous costs and engineering trade-offs: the generator is in the nacelle up high, adding structural cost to the tower, which, at 150m+ nowadays, is a big deal; not to mention the rotors which span the area of a sports stadium. This doesn't scale, whereas kites do, because the tower/blade height/length cost is gone, the generator sits on the ground, and can be bigger (easy access, cheaper, heavier magnets, among other benefits).
Maintenance (and finance of turbine project bearing this in mind) is huge. Servicing an offshore turbine is weather limited and expensive even if you can get there. For kites, just reel them in by pulling more power off the generator to wind in the kites. If they are offshore, then sail the boat (?autonomously) back to a harbor. The list goes on and on, and amazing possibilities open up with a moment's thought.
Agreed with responder that it is early days for the technology, but I expect strong progress through up learning curve from this early stage. Good luck Makani!
http://www.newyorker.com/magazine/2013/05/20/inherit-the-win...
If you think drones are loud, wait until you've heard an industrial kite/drone combo take off in an empty office space.
If its not windy enough, you have to take them in. Too windy or rainy, then pull the kites back. Wing is ripped or bow is cracked from wind or sun damage, time to rebuild.
The kites are expected to be cheaper to maintain and install than traditional turbines, and can be mounted on old turbine bases.
Ground generation, where you let the kite unwind the tether and have generator connected to the spool. Occasionally you need to expend energy to wind it back up, but this can easily be made work out as a net positive.
Airborne generation, where you have small turbines with generators on the wing and lead the power down through the tether.
http://cdn.syscop.de/publications/Diehl2013a.pdf
As to the tether, people are of course aware of the requirements it needs to fulfil, you can even find calculations about it online. Making it strong enough and still light is not a problem, the challenge is really in combining a structural tether with a conducting cable. It is a challenge, true, but it's far from impossible and there are several possible designs.
Makani's 600 kW prototype: https://www.youtube.com/watch?v=An8vtD1FDqs
Hadn't heard much about it since, but am reminded of the proposal every time someone comes up with a comparable design -- to generate electricity at high altitude, where where winds are consistent and strong, and property prices are low -- using some lighter than air or self-propelled vehicle.
I see the gyromill plan has since morphed into a company SkyWindPower[2] and appears to look more like a 4-prop drone now, coincidentally.
[1] https://www.newscientist.com/article/mg16722574-800-reach-fo...
[2] http://www.skywindpower.com/
This article by Moritz Diehl describes very well the expected power output for a crosswind device. https://pdfs.semanticscholar.org/f5da/681fe152e5a81264f8a919....
Also it's important to note that the potential power output for any of these systems are proportional to the cosine of the tether angle, meaning that most of the advantage airborne systems to traditional turbines won't be so much that they can reach higher winds, but just the smaller amount of material required.
https://lirias.kuleuven.be/bitstream/123456789/398835/2/12-8...
The tether is a surprisingly large component of the system's drag. With the two kite design, most of the tether is stationary.