SEP 23

Makani Power is one of six recent US Department of Energy ARPA-E grant winners for their Airborne Wind Turbine (AWT), a tethered flying wing that flies in endless loops around its anchor point on the ground and generates electricity from propellers on board. Makani believes it will be able to produce wind power that is 40% cheaper than conventional wind power and, more importantly, at an unsubsidized real cost competitive with coal-fired power plants.

Think of this as a really big wind turbine. But, instead of needing a big blade going back to the hub, which requires a lot of strength and a lot of weight, only the tip of the blade is used, in the form of a flying wing kite on a tethered line. The kite is flying loops just like the tip of a turbine blade. The tips are the fastest moving and most energy productive part of the turbine; this approach simply gets rid of the rest of the bulky, less-productive blade. The propellers on the wing are turned as it moves through the air, generating electricity and slowing the speed of the wing. The tether serves as both an anchor for the wing as well as the conductor to bring power to the ground for distribution.

The wing is able to self-launch and, since it is not carrying fuel or batteries, it has a very high thrust to weight ratio. The wing is turned vertically and the power-generating propellers act like helicopter rotors to power the wing to its operating altitude of 200 meters (656 feet). When wind at operating altitude drops below 3.5 m/s (7.8 mph), the speed needed to generate power, the wing re-orients into a vertical configuration (hover mode) and is winched back down to its cradle.

You can see a set of animated clips showing just how this works.

Once in flight, the wing is controlled by computer systems which steer the wing to keep it in flight and maintain power generation. "The autonomous controller is responsible for maintaining a stable flight path, while also maximizing power output. To do this, hundreds of times each second the controller calculates the wing’s position and heading from sensor data and adjusts the control surfaces (aileron, elevator, and rudder) to maintain the correct flight path. This fast response allows the wing to easily handle disturbances such as gusts. The control system has been proven, both in simulation and reality, to fly stable and reproducible paths."

We've seen other tethered power generation concepts, spinning blimps, and different versions of giant kites, as well as underwater kites, which are quite similar to the AWT. But the Makani system really seems to have everything pulled together in a complete system. The company has been testing a prototype 10 kW prototype, and will next move to the development of a utility-scale 1 MW system.

Flying at a higher altitude than turbine towers reach means that the less likely to harm birds or bats. Its maximum altitude is 600 meters (1969 feet), which is comparable with tall buildings, radio towers, and other structures, and aviation safety will be maintained with signals and lights in a fashion similar to other tall ground structures.

Comments (17)

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hmmm...
written by Joe, September 24, 2010

Good luck trying to sell a grid scale version of these planes where there's people living. A bunch of these flying around in the air would make me dizzy. I am an avid environmentalist, like most of you, but even I would fight the installation of these by my house.

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Looks kind of dangerous to me, Low-rated comment [Show]

I like it
written by Mike, September 24, 2010

What a neat idea. I know some of you have concerns with the stability of the invention. I'm sure they would need to satisfactorily address these before they are able to site them. You could have the same concerns for one of the blades from a windmill. I'd imagine the'd do a lot of damamge if one of them came loose.
But how nice it is to have something that doesn't require subsidies and can compete.

A big step for renewables.

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President and Chief Economist
written by Peter Meyer, September 24, 2010

try putting the device on old mine sites -- often very high in mountains with lots of wind -- and all the fears above would be irrelevant. (And bind kills would be even lower). This looks like a potential winner to me.

Would yo uprefer mountaintoip removal to get at coal or off-limits mountaintops, with no visible windmills, but these devices on top?

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...
written by Bryan, September 25, 2010

"Flying at a higher altitude than turbine towers reach means that the less likely to harm birds or bats..."

Why make an unqualified statement like this, resting only on the authority of the company's website? It's like saying nothing, but more dangerous than that. The graph of sources of avian mortality shown on the linked Makani page is laughable industry stuff.

Unfortunately, Ecogeek, this is not the first time you've been guilty of glossing over the downsides to alternative energy production (or the way it's being pursued). You can advocate without misleading, if you try.

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written by Ronald Brak, September 25, 2010

The kites appear large enough for birds to see and avoid. If the kites are also brightly coloured like the ones in the photoshopped picture, I think they would be very unlikely to kill birds.

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...
written by Dave, September 26, 2010

Wow! This blows my mind. I hope they start installing these things asap!

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Sea
written by Simon, September 29, 2010

Why not just put them in the sea, just like we do with windmills? I like the idea!

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Bird Kills
written by Barney Sperlin, September 29, 2010

I've posted before, on Ecogeek, about the lying that wind energy companies have done with regard to bird kills and the result was that some posters attacked me as being a shill for the oil industry. But why would a company trying to do an honest job have to lie? This new version seems more benign than the windmills with heavy metal rotars and large towers, but the coloring is irrelevant as most birds migrate at night, many considerably higher than the machine. The statement on the website shows that they are willing to do some phony hand-waving: "Move along, nothing to see here...". Are these people any different than the oil companies when it comes to CYA?

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Projects / Research
written by Breakright, September 30, 2010

Nice concept,some potential, but flakey. Next. The point however, is people are thinking, but unfortunately only as long as the grant money holds out. If our country(government)truly wanted to go green we'd be there by now. Unfortunately we have to worry about the birds, lizards and the lanscape. When's the last time we built a nuclear plant.

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written by nyak, September 30, 2010

Come on...You have got to be kidding.
Lets not sugar coat it. There are far to many moving parts for something like this not to fail under normal conditions and lets not forget someone mentioned putting them on top of mountains.

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No free lunch
written by Bob, September 30, 2010

People, you aren't going to have everything. You call yourselves environmentalists but you think that burning coal is preferable to anything that disturbs your view or carries even small risk to birds, bats, tortoises or us. After all, coal carries huge risks, they just aren't quite as visible, except for missing mountaintops.

As for those calling this flakey, it's amusing to see how people can dismiss work they know essentially nothing about. A bit arrogant, don't you think? When a large-scale demonstrator is built, we'll know whether or not this can be made practical.

And yes, we need some new nuke plants. We also need to use every bit of renewable energy that's available to us so we can use as few nukes plants as possible. This idea makes good sense from basic principles, and crazier-looking things than this run all day every day without problems, they just aren't in the news.

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Ecology anyone??
written by Barney Sperlin, September 30, 2010

Breakright wrote: "Unfortunately we have to worry about the birds, lizards and the lanscape." Well, yes we do. Life on earth is a maze of interconnections. Some we know, some we don't. Killing birds and bats jacks up the populations of their prey: insects for the most part. Killing a lot of insects, e.g. bees, ruins the harvests of crops like apples. It's complicated and our disruptions have surprising and, often, poor consequences for others and ourselves. No, I don't want more coal plants. Putting the dollars into increased efficiency, including insulation gets us more bang for the buck without the same amount of poisoning.

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Stop whining
written by Mia, October 05, 2010

Stop whining. Nothing is ever perfect, and pursuing perfection is stagnating. If we come up with a menu of solutions, we put them together based on geography, weather conditions, population, environmental impact, etc. The goal is get off of fossil fuels. Right?

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Great idea, but how do you scale it up
written by Michael, November 19, 2010

I think that this is a great idea with potential. My main concern is how well it works hundreds of these are in a small area (i.e. like a current wind turbine park). A wind kite by itself will not generate very much power. You will needs hundreds or thousands of them together to cover the cost of power lines.
Do they have a solution to this problem? If not, it can never go large scale.

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Good News and Bad News
written by Roger Carlson, November 20, 2010

The good news is that there are hundreds of thousands of square miles of American lower 48 that are no-fly zones. Hundreds of thousands more could be put off limits for low flying planes (say, 10,000 feet an less).

The bad news is that these areas would NOT be over densely populated areas. Ranchers and farmers would likely not be bothered by an occasional dropping cable or turbine. The 405 freeway at rush hour is another story. Thus, kite wind farms would have the same issues of transmission costs to the urban customers as big solar and "conventional wind" farms.

That said, there have been a number of entrapreneurial groups pursuing this approach because a few thousand feet of altitude provides significantly higher wind speeds and significantly more reliable wind. A more productive power system could better pay for those transmission lines.

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EnergyKiteSystems
written by Joe Faust, January 19, 2011

This is one of over 50 methods of converting upper wind to do works. We are gathering at EnergyKiteSystems to advance airborne wind energy conversion systems and the unfolding era of tethered aviation.

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