Delft professor puts kites high on list for renewable energy

July 13, 2013 by Nancy Owano, weblog
Credit: TU Delft

( —The word "kite" at the Delft University of Technology hardly means summertime fun and recreation. Rather, scientists see "kite" as an important airborne wind technology, with advantages lacking in wind turbines. The university's kite team are encouraged by recent tests in a field near the aerospace engineering department at the university. That is where Roland Schmehl, associate professor, who has a background in computational fluid dynamics, continues to explore kite power. In terms of project scope, such kite trials are dwarfed by impressive wind turbines, but that is just the point. Schmehl believes that conventional turbines only scratch the layer of what can be available in wind as an energy resource, if kite power investigations lead to larger-scale developments. A kite can fly higher and may harness steady winds beyond the limit of conventional turbines.

"The first time I came in contact with this technology in 2009 when I took the position at this university, it was amazing for me to see the that was built by this group, to see how this 25 square meter kite in action on the airfield would fly 70 to 90 kilometers per hour," he said. Seeing the force being generated was for him "an amazing experience." He was convinced then as now that kite technology can make a difference in renewable energy.

Wind turbines are not an entirely stable path, whereas intermittent power is not a problem with kites: the higher you go, the more constantly the wind blows. Added advantages to kites are that they cause less and with lower costs.

A 25 square meter sail can produce enough energy to cover the needs of 40 households, he said, in a report this week in The Guardian. The technology involves the device tethered to a generator unit on the ground. The key in getting it all to work is the automatic control and synchronization of the drum/generator module and the of the kite. There is a traction and a phase, a reel-out and reel-in of the tether. Once the cable has completely unwound it is reeled in again. "We rotate the kite into the wind as we pull it back, so essentially the airstream does part of the work for us," he added. They need less energy to reel in the cable.

This is how the team describes the process:

"The system is operated in periodic pumping cycles, alternating between reel-out and reel-in of the tether. During reel-out, the kite is flying figure-eight maneuvers at high speed (70 to 90 km/h). This creates a high traction force (3.1 kN at 7 m/s wind speed) which is converted into electricity by the drum and the connected 20 kW generator. When reaching the maximum tether length, the kite is de-powered by releasing the rear (steering) lines such that the whole wing rotates and aligns with the apparent wind. Using the drum/generator module as a winch, the is now pulled back to the initial position to start the next pumping cycle. De-powering reduces the traction force during reel-in by 80 percent and for this reason the energy consumed during reel-in is only a fraction of the energy generated during reel-out."

As for cost, he said in The Guardian that wind-generated energy goes at eight cents per kilowatt hour but his team's projections for large-scale production, with kites of several hundred square meters, would set the price at around two cents.

The regulatory hurdle, however, to go with all this good news is aerial traffic. In Europe, he said that his team needs special permission since kites fly at heights that could interfere with flight routes. The University of Delft meanwhile is looking to Africa, and its rural electricity needs.

Whether from the Netherlands or elsewhere, wind technologies other than turbines are likely to stay in the news, According to a July blog posting from the American Association of Petroleum Geologists, numerous private companies and government labs are working on airborne wind technologies. Makani Power, acquired by Google, has attracted attention in this regard. The company site says the Makani Airborne Wind Turbine is a tethered wing that generates power by flying in large circles where the wind is stronger and more consistent. It eliminates 90 percent of the material used in conventional and can access winds at higher altitudes and above deep waters offshore.

The company goal is "utility-scale deployment of airborne turbines in offshore wind farms."

Explore further: Energy from the windy heights

More information:

via Guardian

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1.5 / 5 (8) Jul 13, 2013
They can be Remotely controlled to operate only in a limited area in Air where Airplanes would not traverse....particularly over high seas! They can always be made to shut down & come down, obviously.

In these high tech days all these will not be bothersome issues.
1 / 5 (5) Jul 13, 2013
Since unlike Europe, U.S is bestowed with vast lands...Venturing into offshore turbines has become a no no. These Kites over the gigantic oceans should be the right deal.
1 / 5 (6) Jul 13, 2013
When Eagles can withstand Air Pressure and home in on their prey scurrying on the land from such heights....Why not put (Sub-)brains into the kite to fold & unfold....drop down dead back to the base on orders from its master.
2.1 / 5 (11) Jul 13, 2013
The answer, my friend, is blowin' in the wind.
1.4 / 5 (11) Jul 13, 2013
what great fun and really cool research even if it is so impractical it will only fly high in the minds of craz........greenies.
2.3 / 5 (3) Jul 13, 2013
Seems like a really fragile thing overall. Is it scalable to the megawatt- range and how tightly can you space these things without getting the lines in a tangle when the wind changes?

I can see problems when the wind starts to blow in layers, because the kites move relatively high and can get into crosswinds.
2.1 / 5 (11) Jul 13, 2013
Do it without tax subsidies and I'll be impressed, and able to buy their market determined cheap energy prices. The trillion dollars given so far to applied boondoggles not only crippled cancer and antibiotics research enough to create vast unemployment for top notch organic chemists but alone could have alternatively paid off all of recent student loan debt in the US, debt that will shackle our economy for decades. That college kids voted for green politics zeros out any and all sympathy points from the entrepreneurs who are their only hope for the economy to inflate its way out of the mess. Your daughters are now prostitutes, proud activists, including 350 New York University students with profiles on Raunchy Wall Street boys are in heaven!
2 / 5 (12) Jul 13, 2013
The trillion dollars given so far
What the fuck are you attempting to pontificate? Not everyone on Earth is retarded you need to translate
2.1 / 5 (11) Jul 13, 2013
James Hansen to the partial rescue, the missing word being "nuclear":

"Can renewable energies provide all of society's energy needs in the foreseeable future? It is conceivable in a few places, such as New Zealand and Norway. But suggesting that renewables will let us phase rapidly off fossil fuels in the United States, China, India, or the world as a whole is almost the equivalent of believing in the Easter Bunny and Tooth Fairy." / "The problem is that, by drinking the kool-aid, you are also pouring it down the throats of my dear grandchildren and yours. The tragedy in doing so is much greater than that of Jim Jones' gullible followers, who forced their children to drink his kool-aid. All life will bear the consequences." - James Hansen, 2011
2.3 / 5 (12) Jul 13, 2013
Is it not O.K. or valuable to "pontificate"? Footnotes and Cliff Notes are expensive tickets to Posterity, some sorta blasé afterlife. If I ever make you think then that's enough.
1.7 / 5 (11) Jul 13, 2013
For the record: maverick kite research deserves DARPA level R&D boosts, but no slush funding, later. This stuff is a Ferrari in the sky, 100K of them, or twenty million. Oh, but the maintenance charges!
1.7 / 5 (11) Jul 13, 2013
Energy should be a commodity, not caviar.

"Kill, kill, kill the poor!" - The Dean Kennedys
2.1 / 5 (14) Jul 13, 2013
Some *bot* is auto-voting my comments down, three seconds after posting. There's a whole industry in that, brought 2 U by divinity student and tobacco farmer not to mention *six* fireplace beachside palace owner, Al Gore. The Dumb Dumb brigade marches on, Dutch Tulips in tow. So much for gainfully optimistic review of today's science news, minus feisty parasites. Every day? REALLY?
2 / 5 (12) Jul 14, 2013
Who owns
2 / 5 (12) Jul 14, 2013
...ah, is indeed owned by Omnicron Technolgie$ of Chigago, $mart grid guru$:

"The large amount$ and complexity of the data generated by the power industry lends it$elf to our meticulou$ and methodical approach to data management. Our $mart Grid asse$$ment and consulting $ervices are also perfectly tailored to the quickly changing energy and power indu&try. We have been involved in the education $pace since OTI was founded, back in 1994. Our dedication to the education of $studen$s and the empowerment of $chool $taff has been unrivaled $ince then. With our $uite of powerful and time$aving products, we can tran$form a $chool district nearly overnight."
2 / 5 (4) Jul 14, 2013
Do it without tax subsidies and I'll be impressed

Perhaps you are geographically challenged. Are you paying for this? Involuntarily? No? Then why do you care how someone else spends their money? You are trying to do exactly what you are criticizing others of doing.
2.4 / 5 (5) Jul 14, 2013
Do it without tax subsidies and I'll be impressed

As opposed to what energy source in its infancy?
Are you aware that e.g. nuclear got (in adjusted Euros) 70 ct per kWh subsidies in its first years while solar is getting a paltry 7ct/kWh (and already outperforming nuclear for amount of electricity provided)?

Are you aware that coal and oil are so heavily subsidized that they wouldn't be economical if the companies didn't pay NEGATIVE taxes - even after almost 100 years to get that energy source up and running?

By comparison alterantive energy forms like wind and solar are a steal (and the only reason they are resisted is massive PR campaigns by the coal/oil/nuclear lobby who would see their subsidies - read: free government handouts - suddenly dry up)

1 / 5 (1) Jul 14, 2013
solar is getting a paltry 7ct/kWh (and already outperforming nuclear for amount of electricity provided)?

That is a big fat lie.
1.4 / 5 (7) Jul 14, 2013
solar is getting a paltry 7ct/kWh (and already outperforming nuclear for amount of electricity provided)?

That is a big fat lie.
@Eikka Do you claim that solar cells require a thirty year, billion dollar bond issue before electricity is generated? Do they need that half-trillion yearly DOD subsidy in order to keep oil flowing? You are on the wrong side of history. Solar has only started becoming cheaper. At some point it will be in paint and windows and hardly thought about, while your nuclear juggernaut will still poison lands for millenia
1 / 5 (4) Jul 15, 2013
I'm all for nuclear reactors because it would be amazing to have tons(literally) of Pu-238.

The risks can be mitigated using modern designs, to say nothing of the potential of sodium reactors.

That being said, this is really cool, especially in places where there is no major investment in power infrastructure.
not rated yet Aug 06, 2013
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With characteristic continuous operation should not need expensive storage systems and cumbersome

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