Flying wing prototype takes wind-power to new heights


October 10, 2011

Tethered to the base station, Wing 7 flying wind turbine ascends to a height of 1,300 feet (400m) where it generates up to 20-kilowatt of power

Tethered to the base station, Wing 7 flying wind turbine ascends to a height of 1,300 feet (400m) where it generates up to 20-kilowatt of power

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Wind can be an unpredictable and unstable source of power, and high in the sky where it is more stable, it's difficult to exploit. Airborne wind turbines could provide a solution to this problem, but although the idea has been around since the 19th century, it's never been exploited on a larger scale. California's Makani Power aims to change that with its innovative flying wing turbine design. Wing 7 is essentially a cross between a UAV and a wind turbine that's tethered to a ground station from which it ascends to a height of around 1,300 feet (400m) and flies autonomously, generating up to 20-kilowatt of power in a 20mph (35km/h) wind.

Makani Power's designers have used carbon fiber to construct the 8 meter (26.2ft) wide Wing 7 prototype, keeping the weight down to 58.4kg (128.7lbs). The flying wing can move both vertically and horizontally due to its uniquely designed tail and rotors. It takes off vertically and after reaching the appropriate height, it becomes a sophisticated kite with onboard avionics that enable it to fly horizontally in crosswind circles. The electricity generated by its rotors is then transmitted down the electrically-conductive tether for storage purpose.

The circular path taken by the flying wing is designed to mimic the tip of a wind turbine blade (its most efficient part) and sweeps a much larger section of the sky than a conventional wind tower. This, along with less material and lower distribution costs, adds up to a more efficient renewable energy solution according to Makani.

Wing 7 is being tested in a series of flights this year and, with the backing of funding from the Department of Energy's Advanced Research Projects Agency-Energy (ARPA-E) and private investors including Google founders Larry Page and Sergey Brin, Makani Power hopes to develop a 1-megawat flying turbine - the Makani M1 - that's capable of operating at 1,800 ft (550m) altitude and bring it to market in 2015.

The video below presents a test flight made in July, that fully demonstrated Wing 7's power generation and autonomous flight modes:

Source: Makani Power via Popular Mechanics.


Great. Visual and real estate pollution by \'renewable\' off-again on-again hi-price power pseudo-sources has now reached the skies.

Just think! In optimum conditions, a GW of capacity will only require 50,000 tether-towers and kites. How many square miles did you say that would cover?

Brian H

I would sooner have the blimp fall on me than this 128lb weight! jt.

Jerome Thomas

I hadn\'t even thought about the mobile implications of this until I watched the video. It could easily and quickly be brought to locations in emergency situations or remote locations to provide power where it otherwise would be difficult or impossible.

As far as Brian H\'s comment goes... I\'m not surprised. People CLAIM to want clean, renewable energy, but bitch and moan without end every time a genius new idea comes up. For Jerome\'s comment, a blimp would weigh far, far more than 128 pounds and would be more likely to hit you because it would cover so much larger of a space.

This concept has massive implications, especially in those situations where other energy sources are too slow to build or impractical.

Dave Andrews

Dave, put me down as a bitcher and moaner, I guess, but \"genius\" new ideas are generally partly baked at best. For this one you have a major intrusion into the national airspace system and no mention of the logistics of accommodating it. 1300 feet puts you into class E airspace where planes are allowed to fly IFR (on instruments) Each time you put one of these up a Notice to Airmen (NOTAM) will be required and adequate time for it to be posted into the system. Disaster zones are generally areas of high airspace occupancy so the idea of putting one of these things up there is just asking for an accident to happen.


How many Birds are gonna die Flying into the Tether?, This looks like a REALLY STUPID way to make Electricity.. I looks like Sky Pollution to me. ~impractical, obnoxious, and environmentally disastrous concept alert~


Brian H - I think your assumption is off. This is a prototype, and no one\'s suggesting laying out 50,000 of these things. The megawatt version would require 100 towers to produce a GW. Keep in mind you framed production as a GW, most large windfarms top out at 500 MW. So we\'re only talking 50 towers for a major wind installation.

Tomsonone - Wind installations already have to complete comprehensive environmental impacts. The flight path of a single tether is likely to reduce bird strikes as compared to a traditional turbine.

Lsaguy - Completely valid point, a couple square miles of large wings like this flying around in circles in is going to cause waves with the pilot community.


I really think air born wind generation is ONE of the ways we will replace fossil fuels. 20KW won\'t do it for utility\'s but would be great for emergency workers etc.

Everything is about scale, several high altitude units producing 25MW each would start being viable for taking the load off utility\'s.....

but then there are the hazards to aircraft..... over time it all will be worked out.

Mark Evans

Whoops :D Multiply those numbers by 10.


Would it not be easier to just have this plane act like a kite and be stationary with the propeller blades turning an onboard generator? If it just did that then it would be genius. The only thing you would have to manipulate would be the elevators. The plane would face the wind automatically because of it\'s tail, just like a windmill. Instead, this plane flies in a vertical circle to mimic a wind turbine. I sort of imagine it like putting a feather on the end of a string. If you blow on it, it buzzes around in a circle. But it\'s not reliable, so they had to waste time and money to program it to fly in a circle. Why? KISS. Keep It Simple, Stupid.


Yakov has it right,there is no reason for the kite to \"harvest \" the whole sky. A tethered ballon with an improved vertical turbine suspended beneath it would be much simpler and much less to go wrong with it. mount the generator in the basket, the turbine beneath, the power leads follow the teather back to the base. You could launch it in remote locations, mountians, valleys, rooftops during flooding with helieum to keep it aloft (wind is unreliable) the entire package could be airdropped in problem areas. You could even use it in woods or jungle once you get it through the canopy. It could even be used on ships at sea in need of emergancy power. But the kite is un-needed.


First of all what happens when the wind velocity drops to less than 5 miles an hour - or zero? Obviously it can\'t fly and will come down and since, over land, this happens fairly regularly at night it means someone has to be tending the kite almost all the time - well, probably all the time. Nobody has to sit there and watch a wind turbine on a tower. Secondly there is absolutely no way the system illustrated on this posting can generate 20 Kilowatts of power. The turbine blades look to be about 1.5 metres in diameter which would produce less than 300 watts in a 23 knot wind. Three turbines could possibly generate 900 watts. 1000 watts maximum. That\'s one Kilowatt, not 20. A 600 watt high efficiency wind turbine with carbon fibre blades about the same size as shown in the photo weighs in at 19kg which would account for most of the weight of this 58kg craft - Even if the thing is super efficient and revolutionary it could only generate 2 kilowatts with 35knots of wind. Never 20.

Richard Chesher

Why run in a circle? Efficiency! That circular trajectory makes the effective diameter of the virtual wind turbine that this thing embodies many times the physical diameter of its puny propeller/turbines. In short, it makes the concept practical. Otherwise the prototype would produce some fraction of a kW and be nothing more than a toy.

\"Keeping it simple\" by operating it as a static kite would really be stupid.


Given the wind speed and footprint far more electricity could be generated using more conventional windmills.

It is hard to beat a diesel or gas turbine trigeneration plant, although gas ICE with a biomass converter might.



For disaster relief. It is hard to beat a diesel or gas turbine trigeneration plant, although gas ICE with a biomass converter might.


\"The flying wing can move both vertically and horizontally due to its uniquely designed tail and rotors.\" False. Flying wings do not require \"uniquely designed tail and rotors\". All the other flying wings can move \"both vertically and horizontally\" due to non-uniquely designed tails etc etc. And, just what did their pr mouthpiece tell you makes theirs \"unique\"? WHAT IF IT ISN\'T UNIQUE? \"sweeps a much larger section of the sky than a conventional wind tower.\" So what? Sweeping a large area with a very small brush is not efficient. Any time the little blades are off to the right side of the \"swept area\", they are only gathering energy from the wind that is flowing over those timy blades. Not from any of the wind blowing past the entire rest of the swept area. They would only be capable of harvesting about one ten-thousandth of the energy, since it is not at all 10,000 square meters of the swept area at one time. If you put up 10,000 of these locked into a grid of 100 wide by 100 high, then you would be \"harvesting\" all that wind, and would be more efficient that a large turbine. The wind transfers force to wind turbine blades in proportion to the blade surface area, and these little blades wouldn\'t even show up as a smudge if held against the big blades of a typical 2MW HAWT.


@piolenc: as you stated, it does have very puny propeller/turbines. Also as you stated, it is a virtual wind turbine. Thus, there is no central hub obviously. That means that the puny propeller/generator you cited as a problem in my idea, would also be the problem in this flying wing. It is the thing generating power in both designs, not the circular motion itself.

Either way, 100 pounds of precisely shaped carbon fiber with an advanced computer is very expensive. It is exponentially more expensive than a simple steel tube and plastic kite with one control surface and a cheap generator. It gets the job done for less, which is what \"green energy\" is all about.


Kindly any one explain the minimum wind velocity( flow current ) this airborne required to sustain in air ? And what are the Operation and Maintenance features regarding large scale production ? (Keenly awaits your reply )

Rohit soni

Sory for a post on this old article... (I did read it when it was new, but came back, after these months....)

For starters, this isn't a flying wing..... It is a conventional aircraft, with a t tail, and a tether.... It has a high rate of limb (STOL, call it VTOL if you must).... (If you have ever noted, all kites take off vertically when they have wind in their sails.... This system just allows the wind to be generated (via propellers) when it isn't there at ground level.)

Many of the people commenting have no idea of generating power with aerial systems....

How many of the people advocating a uncontrolled kids kite for generating power have ever even flown any kind of power kite, or advanced kite.. This is a fairly advanced rigid wing kite...

AS this aircraft is able to fly at somewhere between 6 and 10 times the wind speed, a propeller which may generate 100 Watts at 20 knots in a static installation, can now generate in the order of 20kW at an effective tip speed of 120 knots...

In any HAWT under non optimal wind conditions (too fast or too slow), the inner 2/3 of the blades do more to generate drag instead of useful power.... The variable pitch blades have a twist which is optimised at One rotational speed (decreed by the use of synchronous generators in many cases) and one wind speed.... For all other wind speeds, the blades are inefficient.... All this system is seeking to do, is remove the inner 2/3 of the blade (and much more) and using the aircraft wings flying in very large circles approximating a much larger wind turbine....

There is nothing that says there can only be one of these vehicles in any single circuit, we could have many flying the same path, all controlled by a central control system maintaining spacing relative to each other.. ...

People who have seen kites at the beach, (surfing kites I mean) with a proficient "pilot" many kites can be flown with the kiteboarders very close together and the kites flown at different altitudes, allowing them to pass and overtake without clashing.... (even if the kiteboarders are going in different directions) now take this up a level, and put a high level computer controller in charge, and you have the making for a beautiful display of aeronautical ingenuity....

Of course we have to worry about air usage but for a permanent installation it would be marked on all Aeronautical chart... NOTAM, avoid this area....

Imagine wings 10 metres in diameter flying at 300 knots at altitude 5000 feet.... How much power could this one device generate.... sure the drag on the kitestring is the limiting factor.. so it will probably not ever be done.. also, the ar users will scream, forgetting that the air is 3D and there is a lot of space on many rural parts of the world.

Of course I don't care about the carbon, I see an engineering challenge, and an efficient use of higher altitude wind velocity.... It is all about cost effectiveness, not CO2. When clean energy is cheaper than Oil we will use more of it....


I fly kites once in a while. standard kites, multi line kites, to huge power parafoils, this is feasable and maybe desirable for remote deployment, military or emergency. Another way to skin the cat is to use a power foil type and the cabling is only mechanical, turn mechanical into electrical on the ground. I think there is an article that goes in this direction on the Giz. parafoils dont require mechanical components to become energy developing wings, better for transport in the case of deployable power stations.

Jim Ellsworth
People who complain about the small propellers on this device would probably complain more if the propellers were larger. Seriously folks, Google has big bucks and can hire the best engineers in the world with ease. Google would not sink money into this technology unless their engineers and science consultants gave the thumbs up. They have a lot of skin in the game. Jim Sadler
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