Messages in AirborneWindEnergy group.                           AWES10501to10552 Page 107 of 440.
Group: AirborneWindEnergy Message: 10501 From: joe_f_90032 Date: 10/30/2013
Subject: Re: Abbas Rezaey's 10GW AWES Concept

Group: AirborneWindEnergy Message: 10502 From: Mike Barnard Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS

Group: AirborneWindEnergy Message: 10503 From: Pierre Benhaiem Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS

Group: AirborneWindEnergy Message: 10504 From: Pierre Benhaiem Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS

Group: AirborneWindEnergy Message: 10505 From: dave santos Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10506 From: dave santos Date: 10/31/2013
Subject: Short-List of Highest-TRL AWES

Group: AirborneWindEnergy Message: 10507 From: Gabor Dobos Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS

Group: AirborneWindEnergy Message: 10508 From: dave santos Date: 10/31/2013
Subject: NASA Power Wing as TRL9 COTS WECS (the rag-flapper's revenge)

Group: AirborneWindEnergy Message: 10509 From: dave santos Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10510 From: Pierre BENHAIEM Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10511 From: joe_f_90032 Date: 10/31/2013
Subject: Re: Abbas Rezaey's 10GW AWES Concept

Group: AirborneWindEnergy Message: 10512 From: Mike Barnard Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10513 From: Pierre Benhaiem Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10514 From: dave santos Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10515 From: Mike Barnard Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10517 From: joe_f_90032 Date: 10/31/2013
Subject: Re: New Record: 97 seconds on Sept. 25, 2013

Group: AirborneWindEnergy Message: 10518 From: Pierre BENHAIEM Date: 10/31/2013
Subject: Re: New Record: 97 seconds on Sept. 25, 2013

Group: AirborneWindEnergy Message: 10519 From: joe_f_90032 Date: 11/1/2013
Subject: Kite energy and AWES in art .... collecting

Group: AirborneWindEnergy Message: 10520 From: dave santos Date: 11/1/2013
Subject: Re: Abbas Rezaey's 10GW AWES Concept

Group: AirborneWindEnergy Message: 10521 From: dave santos Date: 11/1/2013
Subject: Opposed Spin-basket Variant of Pierre's Megascale AWES Concept

Group: AirborneWindEnergy Message: 10522 From: Pierre BENHAIEM Date: 11/1/2013
Subject: Re: Opposed Spin-basket Variant of Pierre's Megascale AWES Concept

Group: AirborneWindEnergy Message: 10523 From: Pierre BENHAIEM Date: 11/1/2013
Subject: Re: Opposed Spin-basket Variant of Pierre's Megascale AWES Concept

Group: AirborneWindEnergy Message: 10524 From: dave santos Date: 11/1/2013
Subject: Re: Opposed Spin-basket Variant of Pierre's Megascale AWES Concept

Group: AirborneWindEnergy Message: 10525 From: Pierre BENHAIEM Date: 11/1/2013
Subject: Re: Opposed Spin-basket Variant of Pierre's Megascale AWES Concept

Group: AirborneWindEnergy Message: 10526 From: dave santos Date: 11/1/2013
Subject: Re: Opposed Spin-basket Variant of Pierre's Megascale AWES Concept

Group: AirborneWindEnergy Message: 10527 From: Pierre BENHAIEM Date: 11/1/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10528 From: dave santos Date: 11/1/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10529 From: Pierre BENHAIEM Date: 11/1/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10530 From: dave santos Date: 11/1/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10532 From: Mike Barnard Date: 11/1/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10533 From: Pierre BENHAIEM Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10534 From: Pierre BENHAIEM Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10535 From: Mike Barnard Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10536 From: dave santos Date: 11/2/2013
Subject: AWEC2013 Presentations Online

Group: AirborneWindEnergy Message: 10537 From: Uwe Fechner Date: 11/2/2013
Subject: Re: AWEC2013 Presentations Online

Group: AirborneWindEnergy Message: 10538 From: Gabor Dobos Date: 11/2/2013
Subject: Re: heat storage? YES !

Group: AirborneWindEnergy Message: 10539 From: dave santos Date: 11/2/2013
Subject: Kite Dense Array Geometries solve RunAway and Sprawl (review and upd

Group: AirborneWindEnergy Message: 10540 From: dave santos Date: 11/2/2013
Subject: Who is Editing Makani's Wikipedia Page with MikeB's Critiques?

Group: AirborneWindEnergy Message: 10541 From: joe_f_90032 Date: 11/2/2013
Subject: Re: Abbas Rezaey's 10GW AWES Concept

Group: AirborneWindEnergy Message: 10542 From: dave santos Date: 11/2/2013
Subject: KPower On the Move (call for participation)

Group: AirborneWindEnergy Message: 10543 From: David Lang Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10544 From: Pierre BENHAIEM Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10545 From: Andrew K Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen, tether lighting

Group: AirborneWindEnergy Message: 10546 From: joe_f_90032 Date: 11/2/2013
Subject: Slack in line or low-tension in tether

Group: AirborneWindEnergy Message: 10547 From: joe_f_90032 Date: 11/2/2013
Subject: Re: AWEC2013 Presentations Online

Group: AirborneWindEnergy Message: 10548 From: Mike Barnard Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10549 From: Bob Stuart Date: 11/2/2013
Subject: Re: Rotorcraft - Was: Clear Limits to Conventional

Group: AirborneWindEnergy Message: 10550 From: dave santos Date: 11/2/2013
Subject: Re: Rotorcraft - Was: Clear Limits to Conventional

Group: AirborneWindEnergy Message: 10551 From: Mike Barnard Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Group: AirborneWindEnergy Message: 10552 From: Mike Barnard Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW



Group: AirborneWindEnergy Message: 10501 From: joe_f_90032 Date: 10/30/2013
Subject: Re: Abbas Rezaey's 10GW AWES Concept

No new contact from him at my desk. 

However, a paper 

A Brushless Axial Flux Permanent Magnet Generator with Two Mechanical Powers 

Inputs for Marine Current Energy Generation 

 

Asghar Safari-Doust. and Abbas Rezaey

Corresponding Author: Abbas Rezaey, Department of Electrical Engineering, Islamic Azad University, South Tehran Branch, Tehran, Iran 
Group: AirborneWindEnergy Message: 10502 From: Mike Barnard Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS
Hi Pierre . . .

Actually new conventional wind energy is cheaper than new nuclear by pretty much every valid assessment around, including the International Energy Agency, Bloomberg Financial and the Lawrence Berkeley National Laboratory. They put wholesale nuclear in the 11.4 cents per KWH range, and conventional wind energy well below that. Similarly, the UK's recent deal for new nuclear at 15 cents per KWH guaranteed for 40 years is well about the ˜10 cents per KWH for onshore wind energy the UK is currently paying. The UK deal is the only clearly market-priced assessment for nuclear struck in several years, so it's the best indicator of the real cost of nuclear. 

Further, beyond the significant costs, there are other serious problems with nuclear that make it very challenging for any government to propose in any quantities, especially compared to scaling out conventional wind energy.

And conventional wind is striking deals at 5.5 cents per KWH in Brazil, winning almost all competitions including over natural gas, to the point where a new competition that excluded conventional wind energy had to be created so that the right strategic diversity of generation could be created.

Similarly, new coal generation is more expensive than wind energy in the USA as well as many other parts of the world, which is why coal plant capacity factors have been declining in most parts of the world while conventional wind energy has been increasing.

There are about 250,000 conventional utility-scale wind turbines out there right now with a capacity of 300 GW, with tens of thousands more in planning, construction and operability testing. You say thousands are a problem? Well, they aren't. They are being built today and there will be 300,000 utility scale HAWTS in a handful of years, exceeding world wide nuclear generation capacity. Wind is already producing more than nuclear in China.

As my analysis of the Makani solution -- the only AWES solution that is complete enough to be assessed against conventional wind energy -- points out, the tethers associated with crosswind AWES put serious limitations on AWES wind farms based on crosswind approaches, requiring them to be much more broadly spaced, much further from public infrastructure and unable to support multiple economic generation mechanisms such as agriculture and grazing. The acceptance of unmarked, unlit tethers by aviation authorities are also a large unknown. 

My apologies to all of the AWES advocates, but I'm interested in solutions that can do something about global warming today. Conventional wind energy can do that and is doing that. Waiting for something better and not deploying conventional wind is not an appropriate choice. Continuing to research other forms of generation is of course good, but deployment of conventional wind energy will proceed, is economically viable and is the right choice. Pie in the sky doesn't cut it when there is a clear and pressing concern such as global warming.

AWES must compete on full lifecycle costs of electricity. Conventional wind energy is cheaper than anything except unconventional gas in markets where there is a lot of tracking. That's a hard thing to compete with. In order to play at the generation table, you have to provide a lower cost per unit of energy on the full lifecycle, and likely lower so that people will shift.

Don't delude yourselves that conventional wind doesn't work. It works extremely well. You'll have to exceed that.

Cheers,
Mike
Group: AirborneWindEnergy Message: 10503 From: Pierre Benhaiem Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS
Mike,
 
According to IEA in 2011 renewables (wind + solar) are 3.3% of energy mix.This value is far better than for precedent years and probably will increase.But the way is long to replace fossils and nuclear.So 250.000 wind turbines will not be enough:something like some millions will be needed, or an important supplement as AWE.
 
I agree conventional wind energy is actually the better solution against global warming and must be deployed to compete against fossils.
 
About AWES some searches are needed to find the good scheme,probably not crosswind kite moving with its tether (precision because a conventional wind turbine works _ more exactly _ crosswind) as you point out and on which I mentioned limits regarding space used and also low output by unity of swept area.
 
A forum like ours is usefull to try to choose a good AWE scheme without expense of too much money.
 
The point on which I differ is AWE does not compete against but WITH conventional wind energy to contribute to replace fossils and nuclear.And solutions for conventional wind energy,above all concerning projects for offshore with floating tilted turbines, can make the junction with future working AWES.Indeed there is a possibility to increase drastrically wind production thank to AWE. So the goal should be using all possibilities in renewables, fossils working at the end as a temporary storage.
 
PierreB
 
 
 
Group: AirborneWindEnergy Message: 10504 From: Pierre Benhaiem Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS
Following my precedent post:I think investments towards conventional wind energy are better than towards non enough studied schemes in AWE which can destroy the future of AWE.
 
PierreB
 
Group: AirborneWindEnergy Message: 10505 From: dave santos Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

If Mike Barnard is allowed, for the sake of argument, as a real CWE expert voice*, he is not really proving a case that AWE does not promise to compete. His many logical and factual errors are glaring, especially short-sighted advocacy devoted to "solutions that can do something about global warming today". This avoids Franklin's "new-born baby" argument, where people deeply care about creating ever-better future solutions, like we do.

Many other logical errors abound in MikeB's many claims, for example- "the Makani solution -- the only AWES solution that is complete enough to be assessed against conventional wind energy". In fact, hundreds of AWE scientists and engineers are constantly assessing AWE "solutions" (competing architectures). To insist Makani's troubled 5kW avg output scale prototype is the one existing "solution", the only case "complete enough" to reason about, is just a lone "outlier opinion".

AWE R&D investment will continue to grow, with rapid technical progress, without any self-misinformed doubter able to slow it.


* We count Fort Felker, Coy Harris, and many others as our more experienced and sophisticated CWE expert circle, who are enthusiastic about AWE prospects and progress, based on more-careful far-sounder reasoning.






On Thursday, October 31, 2013 5:01 AM, Pierre Benhaiem <pierre.benhaiem@orange.fr
Group: AirborneWindEnergy Message: 10506 From: dave santos Date: 10/31/2013
Subject: Short-List of Highest-TRL AWES
There is now a well-established group of kitesports-derived traction-kite AWES teams, with supervised autonomy implemented by several. Most of the working prototypes generate electricity, but displacing fossil fuel and pumping water are also represented. These are early "solutions", are naturally well toward the Low-Complexity end of the spectrum (this group is collectively at higher TRL than Makani). Even if the simplest designs rely on manual operations (launching, flying, and landing), it has never been decisively proved that manual work is always inherently bad, but it is inherently high-TRL (a society with high-unemployment might welcome the jobs). Let complex automation mature, as piloted-supervised AWES* get a headstart in many interesting niches.

A partial list, in no particular order-

SkySails
KitEnergy
EnerKite
WindLift
WPI
kPower
SwissKitePower
KiteGen
etc.

There is also a growing pack of "homebrew" DIY teams (Kitebot, VisVentis, etc.), not far behind.
------------------------------------------------

* As required by current FARs.


 
Group: AirborneWindEnergy Message: 10507 From: Gabor Dobos Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS
Hi Mike,

I have to apologize before I ask my question. You can be sure, I would not like to disoblige you, but... have you already made economical calculations of a conventional WPP based on reliable data by your own hand/computer/head ? Well, I have it done, and the results were somewhat (....) else than that of yours below. I guess the reason of the difference are the differing input data.  Let's see what I think.

You know and I know that due to the fluctuations in wind power terrestrial wind power plants possess a capacity factor of only 20-30 %. Furthermore the stochastic nature of these fluctuations makes impossible to predict them.

According to opponents of wind power plants, in order to continuously ensure the equivalence of the power inputs and outputs of the energy system, a safety power reserve („backup power”) meeting the actual average power output of wind power plants are needed. Proponents of wind power plants maintain that no such backup power is needed at all. If this is indeed so, it is difficult to understand why there are so many experiments regarding energy storage. It is reasonable to think that both of these viewpoints are biased and that neither is accurate.

Renewable energy is a lucrative business around the world. At the same time wind energy holds the support of many governments, which would presumably not be the case, had these governments no good reasons for doing so. (As I know, e.g. in the United States, wind power plants are authorized for 2.1 cent/kWh production tax credit (PTC). These circumstances bring the question of what our possible projects has to be compared with. On the one hand, it would be unwise to forgo easily obtainable government support and with it the faster pay off. On the other hand, we must be aware of what technology is capable of and not forget, that government subsidies may be modified, even cancelled.

Therefore we need our own reliable data and own calculations. I propose to make a joint calculation in this forum. Let's begin to collect our own reliable input data.

Gabor
Group: AirborneWindEnergy Message: 10508 From: dave santos Date: 10/31/2013
Subject: NASA Power Wing as TRL9 COTS WECS (the rag-flapper's revenge)

The NASA Power Wing (NPW) kite has been around for almost fifty years. Its been tested in many aerospace roles, up to large scales, and is increasingly popular as a dirt-cheap but brilliant sport-kite. A typical grandmother can make one. A child* can operate a Low-Complexity crosswind AWES with NPW TRL9 COTS WECS technology [2013 kPower test finding].

The kite-sports parafoil is not far behind the NPW in WECS priority, arguably also a TRL9 COTS product.


* As defined by Pierre :)
Group: AirborneWindEnergy Message: 10509 From: dave santos Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW
In MikeB's link below, Laurence Livermore predicts Peak CWE deployment around 2021-22, with a decline after that, for a predicted build-out of only 20% of the US energy need. That more-or-less matches the Harvard SEAS assessment, and is clearly not good enough.

The AWE R&D community strives to someday meet CristinaA's call [Springer 2013] for a 50% AWE future (to compliment solar). It will be our excellent-adventure in the sky, if we just do our jobs as scientists and developers :)

Note: Nukes extract a far higher market price than surface-wind, as baseload power. The far-larger upper-wind resource closer approaches baseload need and availability, to potentially best reduce nuke-dependence, and earn the higher "baseloaded" price.
 



On Thursday, October 31, 2013 11:08 AM, Gabor Dobos <dobosg001@yahoo.com
Group: AirborneWindEnergy Message: 10510 From: Pierre BENHAIEM Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Hi Mike,

 

One time again your paper about Makani appears to be useful for AWE R&D. On our forum we (DaveS, probably RodR,DouglasS,perhaps DaveL) critic crosswind tether-kite (both flygen and groundgen moving with tether) as utility-scale and you confirm these problems adding some aspects.But crosswind tether-kite is not all AWE.Could you examine schemes with stationary rotor (Patent US20020192068 - Serpentine wind turbine - Google Patents ,

fig. 45 and 46, and 52 to 59;mine FR2975445  ,Dr Beaujean 500mw wind turbines ) and with rotor working according to reel-out/in method (SkyMill Energy, Inc. - Airborne Wind Energy Conference ,Rotokite, wind generator - YouTube ,Rotating kite?

 

PierreB
Group: AirborneWindEnergy Message: 10511 From: joe_f_90032 Date: 10/31/2013
Subject: Re: Abbas Rezaey's 10GW AWES Concept
Group: AirborneWindEnergy Message: 10512 From: Mike Barnard Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW
Hi PierreB . . .

I look forward to critiquing additional AWES approaches as they become more robustly defined, and completely agree that my Makani critique is most pertinent to crosswind, which is a dominant thrust of research and development in AWES at present (Makani, Delft, etc).

Given that there is no working prototype generating any electricity, no FAA TACO to analyze and few if any claims of specific generation to make comparisons to for the concepts you've listed, it is difficult to do so however. All I will end up with are unanswered questions as opposed to a useful comparison. This might be a useful exercise if the developers of those concepts were interested in checking what questions they haven't asked yet, and were interested in my external perspective.The Sky Serpent I know from other sources had a prototype and has some worked out material, but as far as I can tell is not actively being pursued. (Doug?) Of the other examples provided, the Skymill and the counter-rotating ring wind device are closest to being worked out, but both are still very conceptual with relatively enormous numbers of unanswered questions and no prototypes from the material provided.

At this stage, analyses by people deeply inside of the AWES space who have the mathematical tools to evaluate lift claims are more likely to be of use. My broader systems thinking approach and comparison to grid management needs and HAWT realities is probably better reserved for solutions that emerge from the conceptual into more robust forms.

It is probable that I will abstract the Makani findings on to crosswind generation comments for inclusion in these posts:

Cheers,
Mike
Group: AirborneWindEnergy Message: 10513 From: Pierre Benhaiem Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW
Hi Mike,
 
Maybe have you an idea about reel-in/out systems (groudgen) with rotor (the rotor does not move crosswind with its tether but downwind during power phase,the tether going in the same direction,and upwind being depowered during recovering. With this sort of motion would be it possible for example to make agriculture?The problem of failure can be important during recovering where the rotor losses a big part of control to loss a big part of drag and lift.If an answer looks obvious and negative,the possible AWE scheme to develop could be a completely stationary tether(s)-rotor.
 
PierreB 
Group: AirborneWindEnergy Message: 10514 From: dave santos Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW
 
      Mike stated misleadingly: " there is no working prototype generating any electricity"

There are dozens of working prototypes AWES documented now. Mike seems to imply such prototypes don't even count as a pioneering case-base to reason from.

      "...no FAA TACO to analyze..."

TACO is a typical bottom-up FAA FAR development process case, emerging from the airspace user-community, with years of previous FAA cooperation, and key contributions by FAA officials, active and retired. TACO, above all, promotes strict adherence to all applicable FAA standards and does fairly represent future AWE FAR compliance. Analysis is openly invited.

       "All I will end up with are unanswered questions as opposed to a useful comparison."

A sadly fatalistic prejudice: Better to try with hope to find some useful unexpected addition to AWE domain knowledge ("seek and ye shall find").

       "Skymill...[close] to being worked out...still very conceptual with... no prototypes from the material provided."

I tested one of two SkyMill prototypes [DaveL helped test the first] with Grant Calverley a few years back on the Pacific NW coast, and it flew impressively, as expected. The video link, with discussion, was posted to the Forum. JoeF surely linked it all. Mike just needs to do this homework carefully on his own, rather than expect close spoon-feeding.
 







On Thursday, October 31, 2013 6:44 PM, Mike Barnard <mbarnardca@gmail.com
Group: AirborneWindEnergy Message: 10515 From: Mike Barnard Date: 10/31/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW
Hi PierreB . . .

I would have a number of questions about any rotary kite system. They don't preclude it by any means, but after listing a bunch of them, I do question whether the additional complexity is required for useful amounts of generation.

1. What is the range of tether angles for rotary kites?
2. What is the control mechanism for controlling the device in the air? If it is an in-air bridle controller, what is the operational model for recharging the controller? 
3. Is it single tether to ground, or multiple tethers? Single tether is simple, multiple tethers complex obviously.
4. What is the expected altitude? With the loss of cross-wind generation aerodynamic advantages, are higher altitudes required?
5. What is the advantage of a rotor over a simpler large lift kite if the goal is simply dragging cable out and semi-collapsed return?
6. What are the failure conditions?
7. Under what conditions can the device be safely used?
8. Given turbulence in air and devices at multiple heights at different times with different tether angles, what is distance required between masts?
9. How would tether marking / lighting be managed? It's much more viable given lower drag constraints, but non-trivial.
10. What working prototypes of rotor kites that can be collapsed or otherwise induced to have reduced lift exist?
11. What turbulence and weather impacts are rotor kites specifically susceptible to?
12. How much more complex is landing and launching a rotary kite vs a simple larger traction kite?
13. What is the failure rate of rotor kites compared to simple kites?
14. What is the failure rate of rotary tether linkages compared to simple tethers?
15. How far from public roads and trunk transmission lines would the device have to be setback? Would flying it in only certain wind directions be reasonable as a compromise to allow better siting choices?
16. What is the projected realistic KW output of the device at various scales?

Cheers,
Mike
Group: AirborneWindEnergy Message: 10517 From: joe_f_90032 Date: 10/31/2013
Subject: Re: New Record: 97 seconds on Sept. 25, 2013
Group: AirborneWindEnergy Message: 10518 From: Pierre BENHAIEM Date: 10/31/2013
Subject: Re: New Record: 97 seconds on Sept. 25, 2013


This device (4 rotors among which each rotor has two spaced blades and no hub,increasing swept area but not too much the weight) can be a very good model for AWE.

 

PierreB
Group: AirborneWindEnergy Message: 10519 From: joe_f_90032 Date: 11/1/2013
Subject: Kite energy and AWES in art .... collecting
Kite energy and AWES in art .... collecting. 

Fine artists, cartoonists, illustrators, technical artists, engineers, etc. will in K3 be increasingly illustrating the era of tethered aviation.   Selected pieces are invited to be linked from this topic thread.  

Start:   Item in focus has a page caption: "Modern kite for wind energy."
Group: AirborneWindEnergy Message: 10520 From: dave santos Date: 11/1/2013
Subject: Re: Abbas Rezaey's 10GW AWES Concept

Thanks JoeF, for another nice find.

What we have here from Abbas and Asghar is a pioneering AWES preliminary site study on a grand scale. The authors have identified the US NE megalopolis as a prime energy market, and found an attractive gap-wind terrain (a flank of the Catskills), with an inter-regional grid-access point. 

They have done a lot of original thinking, building on and integrating many powerful ideas from our circles. Secondary technical assumptions are just abstract stand-ins, to be modified as needed. The basic framework is bold genius-level, and the sharing of it a heroic bridge between "East and West" cultures. It would be nice if others join the authors, to further refine this work,

daveS






On Thursday, October 31, 2013 4:40 PM, "joefaust333@gmail.com" <joefaust333@gmail.com
Group: AirborneWindEnergy Message: 10521 From: dave santos Date: 11/1/2013
Subject: Opposed Spin-basket Variant of Pierre's Megascale AWES Concept

Pierre's latest megascale scheme's closest analogue is to a Bol Kite (or "spin basket"), on water, with a PTO (Power Take-Off) at the surface. There is no evident solution I see for extracting such pure tangential force, without the kite rolling to the side of the kite-window in reaction, and collapsing.

A possible solution is to match two side-by-side counter-rotating bols. This allows them to roll smoothly against each other and brace them against tangential extraction at the bottom by two opposed PTOs. This simple design-variant could be tested quickly at low cost. Launching and starting will be tricky until a suitable method is developed (as existing bols show). A future version might use "inflated gears" to mesh forces at the PTO.

The linked image below shows two rotating Gomberg bols set side by side, for a clear general impression, but these are not optimized for max rotary output, nor reverse-handed (mirrored motion), to usefully oppose each other (they chafe a bit when they touch). Just simply turn one bol of a matched-pair inside-out. The predicted optimal direction of opposed rotation is against the natural "wing-tip vortex" direction, for a nice sort of DS-like boost.

CC BY NC SA

http://www.gombergkites.com/update/609-4.JPG
Group: AirborneWindEnergy Message: 10522 From: Pierre BENHAIEM Date: 11/1/2013
Subject: Re: Opposed Spin-basket Variant of Pierre's Megascale AWES Concept

Here is JoeF's counter-rotating variant WheelWindDoublesOneAnchor.jpg . My problem to make a proof of concept of http://wheelwind.com is in first the choice of tangential transmission:1) of type dynamo of bicycle,the generator being at sea-level;problems are possible low output,and also interactions between waves on floating station and wind forces on rotor;2) Circumferential generator,perhaps with two counter rotating rotors allowing the generator to be yet lighter.But building can be complex. The expected advantage is a higher diameter thank to lines with airborne component.

 

PierreB

 

  
Group: AirborneWindEnergy Message: 10523 From: Pierre BENHAIEM Date: 11/1/2013
Subject: Re: Opposed Spin-basket Variant of Pierre's Megascale AWES Concept

 Here is JoeF's counter-rotating variant WheelWindDoublesOneAnchor.jpg .

 

My problem to make a proof of concept of http://wheelwind.com is in first the choice of tangential transmission:

1) of type generator of bicycle,the generator being at sea-level;problems are possible low output,and also interactions between waves on floating station and wind forces on rotor;

2) circumferential generator,perhaps with two counter rotating rotors allowing the generator to be yet lighter.But building can be complex. The expected advantage is a higher diameter thank to lines with airborne component.

PierreB
Group: AirborneWindEnergy Message: 10524 From: dave santos Date: 11/1/2013
Subject: Re: Opposed Spin-basket Variant of Pierre's Megascale AWES Concept

 
Pierre,

The new part is that JoeF's two "wheels" can roll against each other, to give the PTOs needed leverage,

daveS


On Friday, November 1, 2013 11:57 AM, Pierre BENHAIEM <pierre.benhaiem@orange.fr
Group: AirborneWindEnergy Message: 10525 From: Pierre BENHAIEM Date: 11/1/2013
Subject: Re: Opposed Spin-basket Variant of Pierre's Megascale AWES Concept

DaveS,

 

For that the direction of rotation should be the same for each reel since the contact is on their respective opposite sides.Morever the generator should be implemented highly.

 

PierreB 
Group: AirborneWindEnergy Message: 10526 From: dave santos Date: 11/1/2013
Subject: Re: Opposed Spin-basket Variant of Pierre's Megascale AWES Concept

 

The idea presented is just like gears- counter-rotation (clockwise and counter-clockwise) to "mesh" the wheels.

Generation higher up (as a flygen) is different, not what JoeF and I are proposing.




On Friday, November 1, 2013 12:50 PM, Pierre BENHAIEM <pierre.benhaiem@orange.fr
Group: AirborneWindEnergy Message: 10527 From: Pierre BENHAIEM Date: 11/1/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Hi MikeB,

 

Before to go towards specificities to rotary kite system (crosswind blades or wings,but motionless tether for flygen ou Serpentine-like,or only unwinding for reel -in/reel-out_yoyo_, and concerning reel-in/reel-out crosswind tether-kite please can you (for an equal wing speed than flygen Makani) precise also if unwinding is a specific problem for aviation,marking moving while tether is cyclically unwinded at 1/3 wind speed then winded .If yes and if the problem is important,the problem can be the same for reel-in/reel-out rotary kite system, so a quite motionless tether can be preferred.For responses the mention (rigid or soft) "yoyo" (= reel-in/reel-in,examples Rotokite,my rotating kite,Skymill ,HighestWind) or (rigid) "flygen"(Sky WindPower) is indicated.Note that experience is not yet enough to answer precisely to the questions.Please correct me on the forum.

 

Note that rotary AWES can become a non-tethered light structure both airborned and land-seaborned,joining the last innovations of conventional wind energy.The problem is to catch more wind with (generally within about 600 m) less material,and avoid falling on people.Indeed it is not sure that rotary (or any sort of) AWES can resolve inherent problems of AWES (reliability,space and land used). 

 


 
1. What is the range of tether angles for rotary kites?
- 30° to 45° for flygen (the center of Makani's loop seems give the correct value), a little more for yoyo during production,far less during recovering depowered system,the cycle being about one minute. 
2. What is the control mechanism for controlling the device in the air? If it is an in-air bridle controller, what is the operational model for recharging the controller?
- For soft wing, in-air bridle controller, for rigid blades,pitch control.The controller is fed by the generator for flygen,by a small additional turbine for yoyo.  
3. Is it single tether to ground, or multiple tethers? Single tether is simple, multiple tethers complex obviously.
- Single tether for all rotary systems.
4. What is the expected altitude? With the loss of cross-wind generation aerodynamic advantages, are higher altitudes required?
- The same than for crosswind tether:about 600 m, but for it new designs are required to compensate the loss of cross-wind generation aerodynamic advantages.New designs can be by taking away blades one of the other one to sweep more wind by keeping some lightness. The weight is the reason why some systems are for Jet-stream (Sky Windpower,Skymill).
5. What is the advantage of a rotor over a simpler large lift kite if the goal is simply dragging cable out and semi-collapsed return?
- A far better maximization of the worked space, less stress on tether,better visibility (not or little tether motion),determined blades-wings trajectories.And also technology closer to the conventional turbine.DouglasS gives a good definition by telling autogyro-mode is the existing link between aviation and wind turbine.
6. What are the failure conditions?
-Falls by autorotation if the tether is broken.Possibility for flygen to pilot the system as a drone,the generator as motor. 
7. Under what conditions can the device be safely used?
-For limited altitudes (600 m) the same than for other AWES:in case of announce of storm or big gusts, the system must be recovered. 
8. Given turbulence in air and devices at multiple heights at different times with different tether angles, what is distance required between masts?
-The same that for crosswind-tether for beginning (one tether length),but with more safety. 
9. How would tether marking / lighting be managed? It's much more viable given lower drag constraints, but non-trivial.
-For yoyo,additional turbines are needed,and the motion of the whole tether can be a problem,not only because off said turbines;for flygen the generator feeds lighting,the tether being quite motionless,marking is also easier.
10. What working prototypes of rotor kites that can be collapsed or otherwise induced to have reduced lift exist?
-Not to my knowledge.
11. What turbulence and weather impacts are rotor kites specifically susceptible to?
-An autogyro-like has an inertia of rotation allowing a better resistance to gusts on short time.But if the (rigid) rotor losses its speed _due for example to both strong changement of wind direction and no control_the systems falls.
12. How much more complex is landing and launching a rotary kite vs a simple larger traction kite?
-Flygen like an helicopter,generator as motor.Both rigid blades and soft wings as yoyo look difficult;I have no precise answer,perhaps by centrifugal force with rotating mast.
13. What is the failure rate of rotor kites compared to simple kites?
Actual rigid (but not soft) designs need more wind to stay aloft (5 m/s for rigid blades against 2 m/s and less for a traction kite flying crosswind with its tether or for a soft rotary kite),so there is more possibility to fall.It is sure a rigid rotary kite must be landed and launched more often for a same medium altitude,that also increases risks.In the other hand both soft and rigid rotary kite has a determined rotation,control being easier and risks of failure lesser. 
14. What is the failure rate of rotary tether linkages compared to simple tethers?
-Rotary tether exist only for torsion transmission,not for flygen or yoyo.For rigid blades,linkages are under the form of a fixed body or a simple kneecap.These devices are able to generate some wear on the tether.For soft wings,probably no difference.
15. How far from public roads and trunk transmission lines would the device have to be setback? Would flying it in only certain wind directions be reasonable as a compromise to allow better siting choices?
-One time more it is different for yoyo where the cyclic depowered phase generates a risk,and for flygen (which risk is the generator aloft).In all cases 2 lengths (for 600 m in altitude,something like 2 or 3 km of tether) of tether seems to be a minimal value.Although motionless tethers are safer,one great problem of AWES is the link between the airplane and the ground as tether.Besides a jet-stream goes to a single direction,that facilitating the management of the (huge) worked space.
16. What is the projected realistic KW output of the device at various scales?
From some KW to 500 MW (Dr.Beaujean). But the technology is far to be ready.In first a rigid rotary system should be far lighter.
 
PierreB
Group: AirborneWindEnergy Message: 10528 From: dave santos Date: 11/1/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW
PierreB wrote: " it is not sure that rotary (or any sort of) AWES can resolve inherent problems of AWES (reliability,space and land used). "
 
Sorry to see you are as blind as MikeB in your doubts, but its well established that aviation has for over a century used tailwinds to offset fuel use, proving that at least one "sort of" AWE method works. Be very careful to understand this strict logic, before you make such a false claim again.

You are weirdly asking MikeB, a non rotor-expert, for technical answers he honestly admits are beyond his knowledge. What he can answer is whether you should be promoting your windwheel scheme as a proper investment, without any prototype even (no).

If you are serious about consulting a rotor expert who is actively pondering AWES use. Try our man in Austin, Jayent Sirohi:

http://www.ae.utexas.edu/news/463-sirohi-paper-award


Jayent got his PhD from the top UMD rotor-tech program (that just set the HPH record JoeF linked today). Dave Lang also has top rotorcraft engineers in his circle, who helped with SkyMill development, and would also help you (if you will focus your questions to specific factors). Many key facts about AWES rotors have been well examined on the Forum.

It seems that confidence that AWE will someday be highly perfected is highest in both children and formidable aerospace experts. The biggest doubt is just how long the talented developers will take to fully triumph :)




On Friday, November 1, 2013 3:47 PM, Pierre BENHAIEM <pierre.benhaiem@orange.fr
Group: AirborneWindEnergy Message: 10529 From: Pierre BENHAIEM Date: 11/1/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

DaveS, 

 

 

" it is not sure that rotary (or any sort of) AWES can resolve inherent problems of AWES (reliability,space and land used). "

 

What is false? My doubts or your certainties?

 

About "Note that rotary AWES can become a non-tethered light structure both airborned and land-seaborned,joining the last innovations of conventional wind energy".That concerns general concepts diverted from wheelwind,but not quite wheelwind since it has tethers.

 

As usually you deform the words.

 

 

PierreB
Group: AirborneWindEnergy Message: 10530 From: dave santos Date: 11/1/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Pierre wrote: "What is false? My doubts or your certainties?"

Both are part false, of course. I am not arguing certainty, except to assert that technical high-confidence is definitely not primitive certainty. I am highly-confident AWE is on-track to succeed, based on successful direct scale-testing of so many AWES ideas during the years, and a life of study and practice of advanced aerospace, classic kite, and industrial rigging methods. Every day adds more knowledge and capability. What a wonderful world.

Your persistent doubts seem based on a relative ignorance of the powerful case for AWE optimism. We can be phenomenologically certain that the success of kite sports exists, as well historic aviation use of wind (including rotorcraft). How can you doubt these tangible success cases of AWE?

I am sorry to be so harsh, Pierre, but spreading doubt without solving the problems is an obviously sterile path, if AWE is in fact destined to succeed. Doubt goes with depression. Risking AWE R&D  failure by eager trying, as a social responsibility, is best done with Joy. More so as we finally succeed, just as Etzler could forsee, so long ago.

The same logic of confidence applies against MikeB's doubts.





On Friday, November 1, 2013 5:23 PM, Pierre BENHAIEM <pierre.benhaiem@orange.fr
Group: AirborneWindEnergy Message: 10532 From: Mike Barnard Date: 11/1/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW
Hi Pierre . . .

From this information, a couple of quick observations of risks and limitations can be made. This might be useful in development of the idea and thinking about examples of the idea.

The first is tether length and spacing. If the devices must indeed be spaced out tether lengths apart, and the tethers are 2-3 kilometres long, this is a very large obstacle to useful deployment. But I don't think that's correct. If the device is flying downwind only with some minor variance, then all close by devices will have roughly the same angles.  Worst case scenario in normal generation is when one device directly downwind is at 45 degrees, and the directly upwind device is at full tether length and 30 degrees; the resultant possible intersection point and fouling is a lot less than tether length. Second worst case scenario is failure of a device, especially tether retraction. Given the side-to-side stability, it has a low percentage chance of impacting downwind devices if it falls out of the sky.  The devices will still have to be spaced out, but it won't be tether lengths apart.

The second is tether length and downwind infrastructure such as roads and trunk lines. As Makani notes in their TACO, with their 440 meter tether, they request what I believe is an aggressively short 1.5 kilometre setback from public roads and trunk lines. With a two kilometre tether, a winch failure could have two kilometres of draped tether lines over such infrastructure, an unacceptable outcome. With a tether failure and tether drag, even with remote control of the device it will be carried downwind. Makani's setback is, I believe, based on the autonomous upwind flight capabilities of their device, plus recovery time, plus contingency.  Building upwind autonomous flight capability into a rotating kite is far from trivial, so I suspect this risk has a very high impact if it occurs. As a result, a lot more engineering would have to go into preventing it. Automatic kite stall has been mentioned related to other AWES approaches. This would at least get the device out of the air more quickly and reduce the downwind potential. Single tether reduces complexity, but increases the likelihood of this risk.  

The concerns about tether marking or lighting have a couple of dimensions. From the FAAs perspective, the slower moving and shorter a tether is, the more likely that they will consider it to be equivalent to a guy wire as Makani asked.  A 2 km tether at potentially 600 m high that is relatively stationary will likely be viewed as a lower air traffic risk than Makani's rapidly moving tether, but they may consider greater downwind distance to be more problematic.  In any event, marking or lighting a relatively stationary tether will still likely be required but is much more viable due to lower drag. If it's lit, then energizing the lighting system becomes a significant limiting factor; two kilometres of lights is a lot and would require a lot of juice. Two kilometres of attached reflectors or balls begs the question of them dropping off, how to get them onto the tether as it is reeled out and how to get them back off as it is reeled back in.  This is a significant cost and complexity issue that has to be addressed before a commercial solution is ready for prime time.

The lack of any prototype of a rotating kite system generating useful traction to a ground regenerative winch, and the lack of evidence related significant advantages compared to simpler choices concern me, as does another generation system in mid air just to charge batteries. Of course, that's likely going to be necessary for lighting for night time generation in any event. Once again, added complexity and failure points.

How fast can two kilometres of tether with a device like this be brought in? If a thunder storm, high winds or snow is forecast, how long before the weather front hits must generation be curtailed as the device is retrieved? And how long will it take to get it up to the altitude it must usefully generate at again before it can start producing electricity?

The concept of something which spins upwards even in light or no winds is useful to allow capturing of winds aloft when it's still on the ground, but what is providing rotational stability? A motor would just spin itself around beneath the blades if the simplest concept were used, so this implies yet more complexity in air.

Basically, I'm not sold on it even as a concept. It has significant challenges.

I'd love to get detailed documentation on the Skymill to assess how it has overcome these various concerns. At present I've only found a very light powerpoint presentation with what looks like a serious generation capacity calculation error in it from the 2010 conference.

Cheers,
Mike


On 2013-11-02, at 6:47 AM, Pierre BENHAIEM wrote:
Group: AirborneWindEnergy Message: 10533 From: Pierre BENHAIEM Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Mike,

 

Question 15:" (for 600 m in altitude,something like 2 or 3 km of tether)". Correction:in fact only 1.2 km if the angle of flight is 30°. And the kite being in 600 m altitude,that means 600 m is the center of the area swept by the blades.The 440 m tether of Makani allows the wing to fly between 140 m and 310 m (I am not sure of these numbers), so the center of the area swept by the wing is 225 m. So for an equal average altitude the tether length of both rotary kite and crosswind tether-kite Makani are roughly the same.In case of broken tether,concerning Makani one must add the effect of centrifugal force making the wing going farther.

 

PierreB

 

PierreB
Group: AirborneWindEnergy Message: 10534 From: Pierre BENHAIEM Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Mike,

 

All utility-scale AWES should be studied for offshore implementation, where deep sea is not more a problem for anchoring (where installation is not possible for conventional wind energy,even with new floating station),and where failure has less consequence,and not onshore excepted in deserts,that due to important risks,so an important no-fly no-inhabitants zone being needed.

 

Problems with aviation can be lesser in a lot of places offshore.For fishing one can consider stationary devices like rotary kites are safer than crosswind tether-kite.But an angle of 30° means ships cannot pass at all places,as well as they cannot pass too much near wind conventional turbines.

 

PierreB
Group: AirborneWindEnergy Message: 10535 From: Mike Barnard Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW
Hi Pierre . . .

That was my assessment a year or so ago when I first looked into high-altitude wind. If anything, my recent deeper dive into AWES recently has reinforced this.  

Reliability, survivability and low maintenance requirements for an effective offshore AWES system are more stringent than for an onshore AWES. It's a harder engineering target with lower external constraints. However, the lesson of offshore wind is that there is a lot of stuff going on out there and a lot of jurisdictional issues to sort out, so the external barriers to building are more equal.

Cheers,
Mike
Group: AirborneWindEnergy Message: 10536 From: dave santos Date: 11/2/2013
Subject: AWEC2013 Presentations Online

 A trickle of presentation documents are emerging from AWEC2013; the odd note is Fraunhofer Germany censorship (some Promethean attendee will need to share the content). Thanks to MarioM for this page notice-


http://www.awec2013.de/index.php?page=download
Group: AirborneWindEnergy Message: 10537 From: Uwe Fechner Date: 11/2/2013
Subject: Re: AWEC2013 Presentations Online
Hello,

there is still an error on the linked web-page:

I am working at TU Delft and not at KU Leuven. The correct
reference to my presentation is:

Fechner, U. (2013). Dynamic Kite-Power System Modelling. Airborne Wind Energy Conference 2013,
September 10-11, Berlin, Germany (Presentation).

Best regards:

Uwe Fechner


Am 02.11.2013 15:09, schrieb dave santos:
Group: AirborneWindEnergy Message: 10538 From: Gabor Dobos Date: 11/2/2013
Subject: Re: heat storage? YES !
Hi Harry,

In my previous post I have mentioned some further (maybe extreme) examples just to expand your links (you have put a "?" at the end of the subject of your message)  and to show the possibilities of heat storage and at the same time the limits and sometimes inconvenience of the technique.

The exposed difficulties justify further R&D work. The  topic has (at least) four tasks/problems to solve:

  • enhance the energy density of the applied energy storing medium in order to fulfill the special demands of the several applications. E.g.: in cars or flying vehicles decreasing the mass of the device has great significance. (See the demands of my IFO(Untethered flying wind power plant) discussed in this forum.)
  • decrease safety risks
  • simplify the technology
  • decrease costs (It contains implicitly enhancing the life cycle too.)

In my post of  On 30-Oct-13, at 7:40 AM  I cited a classification of the several techniques (see below). I vote to the chemical methods because of  the large gap in energy density in favor to the chemical methods.  Please consider that the energy density of the other methods (among other that of the batteries) is ludicrously low. The reason is simple and well known: the energy of chemical bonds are much larger than that off physical changes like fusion and evaporation.                                                                                                                                                                                                                                                                                                                                         

Well, sometimes one can find an acceptable compromise, - another time not, since there isn't today any method that fulfills compromise-free all the requirements. (Otherwise all WPPs would have an energy storage unit, - but they haven't.)

Something is sure. Energy storage is also a distinct profession, and probably not smaller than the knowledge of flight technique and it's related issues.

Gabor
Group: AirborneWindEnergy Message: 10539 From: dave santos Date: 11/2/2013
Subject: Kite Dense Array Geometries solve RunAway and Sprawl (review and upd

Dense kite arrays are both ancient and modern; as popular branches of classic kiting. Endless variations are possible by train, arch, and 3D configurations. Aggregate-unit architectures are a top megascale-AWE principle. A hundredfold increase in practical AWES array density over single tether-point space usage is typical in geometric analysis.

Surprisingly, many would-be "AWE experts" (like MikeB and maybe even PierreB) seem unaware that these methods disprove simplistic pessimistic assumptions about the field being stuck by the risk of runaway and sprawl. AWE ventures that identify and develop these methods will enjoy great advantages. The AWES Forum has long documented the emergence of the dense-array paradigm for AWE.

The modern story of dense array thinking can be traced vertically from Dave Culp's early Flexi stacks to Wubbo's Laddermill scheme, and then horizontally as crosswind arches, as popularized by Kay Buesing of the World Kite Museum. Perhaps the most advanced tested concept in the dense-array space is Mothratech, where large numbers of unit "kixels" fly closely and reliably together. WECS are similarly flyable in close formations (KiteLab Ilwaco testing).

CC BY NC SA
Group: AirborneWindEnergy Message: 10540 From: dave santos Date: 11/2/2013
Subject: Who is Editing Makani's Wikipedia Page with MikeB's Critiques?

 The following MikeB text and reference was recently added to Makani's Wikipedia article, effectively doubling its length. A whois query found the anonymous Editor working via an IBM server in Singapore-
Group: AirborneWindEnergy Message: 10541 From: joe_f_90032 Date: 11/2/2013
Subject: Re: Abbas Rezaey's 10GW AWES Concept

Abbas writes to Editor:   And Editor links photo. See his link for more interesting good works: 

Note to AWES forum by moderator: We are working out a way for Abbas to post directly. In the interim: 


 Photo of Abbas from the page he links for us:


Dave Santos, 

 I was author of another paper entitled as "Novel Airborne Floating Circular Wind Energy Generation System for Distributed Electrical Energy Generation Applications" can be used for such mega-scale wind farms.

My other publications can be found here: http://ijarer.org/cv/ publications.html

Regards
Abbas Rezaey                          Nov. 2, 2013
Group: AirborneWindEnergy Message: 10542 From: dave santos Date: 11/2/2013
Subject: KPower On the Move (call for participation)

KPower is an Austin-based Airborne Wind Energy (AWE) llc that began in 2007 as CMNA, with close connections to KiteShip of Alameda, CA (the legendary Dave Culp advising). The start-up incubated  and graduated from the University of Texas affiliated ATI (Austin Technology Incubator), winning various awards, and even landing a Challenge Investment from Austin Energy, the first electric utility in the world to so recognize AWE as a potential game-changer. KPower also developed early strategic partnerships with the SouthWest Research Institute (SWRI) and National Instruments (the most popular testing and control environment in global AWE R&D).

K-Power's initial technical kite basis was a KiteShip OL ship-kite design specially modified for stable low-drag retract, and matched to a vertical-axis winch-generator. A large customized Delta was a comparative wing and pilot kite. Early test results were partial but promising toward the Low-Complexity "softkite and groundgen" side, but High-Complexity flygen hype (rigid wings, LTA, etc.) for years dominated mindshare over all other players. The High-Complexity ventures badly over-reached and began to be widely doubted; finally opening a decade-plus window for Low-Complexity AWE (soft-kites and groundgens) to be first-to-market and take hold as the possible winning lineage. KPower emerged from this lean period with new momentum.

WOW SpA then entered the kPower picture, as the original and still-leading AWE start-up investment fund and holding company. WOW has even managed an AWE industry-first profit for its many small investors, as KiteGen bought back its founding shares at a premium. WOW now sees in kPower a new vehicle to both consolidate and diversify pioneering AWE value for  investors. KPower is being restructured for growth, seeking to amass the largest most diverse AWE human talent and IP Pool. The Austin Tech Ranch is helping kPower succeed.

Early kPower revenue is anticipated from a variety of sources. A series of small simple AWES are being developed in partnership with New Tech Kites as a current hot project. KPower and WOW are sponsoring open AWE fly-in events like AWEfest (NYC) and the Texas AWE Encampment, to integrate essential interactive R&D opportunities synergistically with public awareness-building. A particularly strategic media project being sponsored is the AWE Documentary, the first major overview for mainstream audiences. Most big-names in AWE have already been interviewed, or are scheduled for interview, to help make this a definitive media production.

An early round of kPower equity mergers-and-acquisitions, partnerships, and IP licensing is underway. Little-known domain-expert-selected AWE R&D talents are actively being invited into kPower (by partnership, merger, acquisition, IP licensing, etc.). The working R&D model is shared microcapital and close-cooperation between many small teams, including academic players, to create scale projects representing the full range of contending AWE solutions, to field a "sport league" of internally-competitive prototypes  (flygen, groundgen, kiteplane, soft-kite, rotor, etc.) for third-party validation by Fraunhofer Society (written positive intent provided for a scoring-matrix and fly-off). This process should green-light winning solutions for major investment.

The first to jump aboard kPower as an equity partner was KiteLab Group (my affiliation), a circle of open-source players. Roy Mueller's Aerology Lab (founded by the great Jalbert, inventor of the parafoil) has joined. A top person in AWE open-source is Joe Faust, the "knowledge-hub" of AWE, as its leading archivist. KPower is proud to work closely with Joe, as an equity partner.  Many other early pioneers are increasingly closely affiliated, making kPower a major player second to none in the AWE race.  KPower is a leader within the Kite Power Cooperative. The Cooperative brings together an even larger circle of AWE talent. KPower is also a key supporter of AWEIA (Airborne Wind Energy Industry Association). KPower affiliated teams are ongoingly delivering a rich stream of industry firsts, from megascale demonstrations (Mothras) and pioneering utility R&D, to small commercial AWES offerings.

Advanced best-practice social-enterprise standards, like open-innovation and broad stakeholder orientation, are a strategic edge for kPower over competitors. The company is committed to knowledge transparency as the basis for top excellence. KPower is being prepared as an enterprise-class player  for what WOW intends as a repeat, on a grander scale, of its initial viral crowd-sourced AWE investment fundraising. An equity-growth deal with a major player, like Silverlake or Sabic, could speed the multi-year business plan along, but is not essential. Many of the kPower venture strategies now in play were first carefully explored on the AWES Forum (the expert forum-of-record in AWE). 

To accommodate vast anticipated growth of the AWE industry, kPower's long-term strategy is to relentlessly recycle equity by programmed stock by-backs. To ensure popular support, the eventual equity structure of AWE would include all stakeholders, particularly local highly impacted populations. World airspace would forever remain a commons, with freedom-of-the-skies ensured.

The hard work has barely begun. Please join us if you can help. Please contact Ed or Paolo if you are interested in the business side of KPower. Contact me to join in comparative testing planning and other technical areas.
Group: AirborneWindEnergy Message: 10543 From: David Lang Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW
MikeB,

I suggest you become rotorcraft savvy, as well as become knowledgable of design specifics of rotor-based AWE schemes before speculating about such engineering issues in public. While it is OK to be ignorant, one must indulge such ignorance without assuming any air of representing implied authority in such matters, nor insinuating design non-validity in public;  one commands respect and authority by in fact exhibiting true authoritative knowledge.

DaveL
Group: AirborneWindEnergy Message: 10544 From: Pierre BENHAIEM Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW

Hi MakeB,

 

While you point issues concerning marking and quick motion of tether for crosswind-tether-kite,it would be interesting you build more precise arguments concerning rotary systems,for example by taking again each of your 16 questions, and if possible after dialogue with experts of them (I am not among them in spite of a light contribution as a single rotating soft kite for yoyo):David Lang (specialist in tether,space,AWE;Skymill,rigid blades,yoyo,jet-stream), P.J.Shepard or Bryan Roberts (Skywindpower,rigid blades,jet-stream),D.Cherny (HighestWind,rigid blades,yoyo,"low" altitude),Gianni Vergnano (Rotokite,2 soft opposite wings,yoyo), Dr.Beaujean.

After that you can make a comparison with crosswind tether-kite (yoyo and flygen).Then the same for not-crosswind,for aerostats,and why not for non-tethered AWES from Dr. Gabos.For that you can consult the datas concerning all methods in AWE from Joe Faust,Energykitesystems.

After that arguments in favor or against any family of AWE (or the whole AWE) will take more importance.Thanks.

 

PierreB  
Group: AirborneWindEnergy Message: 10545 From: Andrew K Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen, tether lighting
The large (71 meter) TCOM aerostats all flew in restricted airspace
zones and did not have any markers or lights on the 10,000 foot
tether.

The smaller (31 meter) aerostats were sometimes ship based and they
put strobes on the 3,000 foot tether at night and orange flags during
the day, manually clipping them on during launch and removing them on
retrieval.
The ship based systems were operated by the Coast Guard so they had
definite ideas about lights and hazards to navigation.

Andrew in Ann Arbor
Group: AirborneWindEnergy Message: 10546 From: joe_f_90032 Date: 11/2/2013
Subject: Slack in line or low-tension in tether
Slack in line or low-tension in tether does not negate the "tethered" reality; the wings involved in the kite system are still tethered.   During slack or low-tension time, the wings involved in the kite system are still tethered. Careful distinction is invited in order to be clear about rogue wings, breakaway wings, broken tethers, etc. Suggested for the AWES community is to reserve "untethered" for scenes that strictly have wings that are no longer tethered.  Safety-critical matters seem to be involved. 


 "temporarily untethered"  seems to be a very misleading phrase for a situation where the wings are still actually tethered.    Such phrase was used in one of the presentations in a recent conference. 

~ JoeF

 
Group: AirborneWindEnergy Message: 10547 From: joe_f_90032 Date: 11/2/2013
Subject: Re: AWEC2013 Presentations Online

 Uwe Fechner's presentation 

in PDF format: 

http://www.awec2013.de/pdfs/Uwe_Fechner.KitepowerModelling.pdf
Group: AirborneWindEnergy Message: 10548 From: Mike Barnard Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW
Hi DaveL ...

Glad to be corrected. Please help me learn by providing quality referenced material on rotary kites to absorb. 

It's possible I was merely unclear as well. Which specific piece did you find problematic?

Cheers,
Mike

----------------------------- ipad -----------------------
The future is already here. It's just not very evenly distributed. - William Gibson
Group: AirborneWindEnergy Message: 10549 From: Bob Stuart Date: 11/2/2013
Subject: Re: Rotorcraft - Was: Clear Limits to Conventional
I have been wondering if something like an Autogyro might be particularly suitable as a pilot kite, to lift a train of parafoils through turbulence near the ground.  The flywheel effect might be a useful addition to the usual tricks to increase stability.  

Bob

On 2-Nov-13, at 5:58 PM, Mike Barnard wrote:
Group: AirborneWindEnergy Message: 10550 From: dave santos Date: 11/2/2013
Subject: Re: Rotorcraft - Was: Clear Limits to Conventional

Bob,

Yes, rotors are not just in play as pure WECS.

An electric helicopter (with autogyro mode) would indeed make a great initiator pilot-kite, because it can rise thru common surface calm into LLJs. In smooth or turbulent wind conditions, its possible to get a pilot kite up, without bothering with a copter. Tow-launch is another option in surface calm, with a pure autogyro tow possible, if not necessarily favored. Micro-LTA is a launch-initiator contender as well. Retracting the launch initiator platform after a full launch is a good option, since ordinary sessions easily go initiating full cascade-launches up into the wind gradient. Cost and safety will tend to pick the winner,

daveS








On Saturday, November 2, 2013 5:49 PM, Bob Stuart <bobstuart@sasktel.net
Group: AirborneWindEnergy Message: 10551 From: Mike Barnard Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW
Hi PierreB ...

I've poked around a bit at Skymill and Skywindpower now that you've pointed me to them specifically. 

Skymill

Skymill has precious little available outside of the lightweight conference presentation, so beyond my previous mention of the odd generation calculation and applicability of the set of concerns we are discussing to its conceptual design, I can't say much more.

Skywindpower

There is more information available for Skywindpower. The quadcopter approach makes more sense than rotary kites at one level, addresses some of the concerns identified, and like Makani looks viable to generate electricity. It does so by adding a lot of in-air complexity, as I pointed out would be required in my previous comments on rotary devices (which seem to have been misunderstood).

Skywindpower is foregoing most of the cubing of wind velocity Makani takes advantage of by cross wind flight while still suffering from a large loss of wind swept area. To get significant generation with this, as they point out they would need to be flying it in the 15,000-30,000 ft (4500-9000m) range. To be conservative this implies a minimum 9 kilometer electrified tether which is at any given time some where in a half sphere with a 9 km radius. That leads straight back to tether length and marking / lighting as unresolved problems, but multiplies them. 

They project one quarter the swept area over four blades for equivalent generation faceplate capacity. Let's consider a five MW conventional wind turbine with a minimum capacity factor of 35% as a comparison. It has 128 m rotor diameter, and PiRˆ2 gives us a swept area of just under 13,000 sqm. A small amount of math tells us that the Skywindpower device would require four 32 m diameter rotors with a total craft size of about 37 meters (130 ft) including blades per side. For context, the MI-26 heavy lift helicopter has a rotor diameter of 32 m with its eight blades; check the rotor droop. Ground equipment and tethers are not worked out in any detail on their public site.

Mil_Mi-26,_Celebration_of_the_100th_anniversary_of_Russian_Air_Force.jpg


Tether weight is a glossed over issue on their site; Makani's one km tether is projected to weigh 3660 kg; let's assume that is accurate. The minimum length 9 km conductive tether would weigh about 33,000 kg assuming adequate strength but one of the heaviest lifting helicopters in the world, the MI-26) has a max lift of about 26,000 kg and a hover ceiling of 1700 m. They seem to be projecting making a device that is much better than anything created by the military industrial complex which strikes me as unrealistic, not to mention nontrivially expensive on development and a per unit production basis. It wouldn't surprise me if a 9 km carbon fibre and aluminum conductive tether cost more than the mast of an equivalently generating conventional wind turbine, and tether plus device cost more than a conventional wind turbine of equivalent capacity.

So they are projecting building the biggest multi-rotor helicopter ever, the largest autonomous helicopter ever, the heaviest lifting helicopter ever, and the highest-flying autonomous helicopter ever. My apologies if that doesn't sound like a recipe for success in any near term time frame, or something where even a small fraction of the engineering challenges have been worked out. It's unclear to me that it's even possible given air density with increasing altitude although they assert that helicopter limitations don't matter due to using rotor kiting; they don't show their math.

Like Makani, Skywindpower do not address temperature variation as a concern in their public material. However, while Makani can safely operate in tropical and subtropical climates, or in summers in temperate climates, the Skywindpower device is projected to fly at altitudes where the temperatures are often below zero regardless of surface temperatures. The rule of thumb is 3.5 degrees F (2 degrees C with rounding) per 1000' of altitude gain. At minimum suggested operational altitude of 15,000', the Skywindpower would be operating in temperatures on average of about 53 degrees F or 30 degrees C below surface temperatures. I'm sitting 85 miles from the equator in Singapore right now in 30 degrees C weather. There is no mention of de-icing technology requirements, which will also add to in air weight and complexity as well as maintenance operational costs.

Skywindpower's current plan per public material is to land the devices when lightning is forecast. They make no mention of how long it will take their device to ascend to its 4.5 km operating minimum or descend from that altitude safely, but they project future developments again which will make this unnecessary. They are silent on other weather conditions which would require grounding of the device; personally I can think of half a dozen. They are also silent on energy required to lift the device and 33,000 kg of cable to operating height and what the net energy output will be as a result. For context, one conventional wind farm's draw from the grid for blade start and other peripheral items was 1:320th of the annual generated electricity.  http://barnardonwind.com/2013/03/02/parasitic-power-and-wind-turbines-sounds-scary-but-whats-the-real-story/

Like Makani, maintenance requirements will be much higher for this device than for a conventional wind turbine. With icing and weather related downtime as well as significant energy loss to get their device to altitude it's unclear that they will achieve the significantly greater capacity factors to overcome other challenges. Remember that new conventional wind turbines operate at 35% capacity factor in lower wind category zones, and up to 47% capacity factor in the best wind category zones per LBNL. Achieving significant multiples of those numbers is non-trivial.

Spacing requirements will also be large. 

Assuming a Skywindpower farm, and multiple devices at multiple altitudes with multiple tether angles ascending and descending, a single 37 m per side device will need a fair amount of operating leeway on all sides given turbulence, tether slack and tether oscillation. If a device manages to get the cable of a nearby device caught in its blades, both are likely to be in serious trouble and this would very likely cause a domino effect in other devices which would have to be taken account of in spacing.. Given the control mechanisms available to quadcopters and the more common angle of tethers, the spacing might be lower than Makani's, but once again, the Skywindpower public material is silent on this. 

Worst case scenario is a higher-altitude Skywindpower device having a broken tether a kilometre or two below the device due to an airplane strike or a malfunction on another Skywindpower device. The Skywindpower device would be blown downwind rapidly, with the 3700-7400 kg of severed tether penduluming beneath it. Once it stabilizes, it will not have power so it probably won't be able to make headway and will likely still be going downwind if more slowly under autorotation.  All devices downwind then will have the tether dragged through their operating airspace and potentially fouling their rotors. This implies at minimum very large gaps between devices as well as a very large amount of in air synchronous flying automation given the oscillating tether. While quad copter automated synchronous flying is advancing, at present it is only done with tiny quad copters in safely enclosed indoor volumes. The Skywindpower team assert that they could bring a device down safely in the event of a severed tether, but it's unclear that they have thought through the scenarios. In any event, the implication for spacing is that safety requirements for the foreseeable future will required significant spacing, likely more than conventional wind turbines just as with Makani.

I'd be interested in looking at their intended spacing, as I'm sure the FAA would as well. They claim 1:400th of US airspace would be required, so they've done some density math, but once again do not show that math. 

The area under a Skywindpower farm will be the equivalent of an airport. Due to very large devices landing and taking off, it is likely that no other economic uses would be allowable due to workers safety and insurance reasons. Unlike Makani, maintenance would likely not require nearby generating devices to be shutdown however. This once again is a comparative disadvantage to conventional wind farms which are mostly interspersed with agricultural and other land uses.

Skywindpower indicates that they have had initial discussions with the FAA on a TACO and have some ideas on how to achieve acceptance of their device. Their comparison to blimps is disingenuous just as Makani's comparison to antenna tower guy wires is disingenuous; blimps have passive lift and are much safer than an auto rotating quadcopter with four rapidly rotating blades of the scale of the Skywindpower projected device. Imagine four MI 26 heavy lift helicopters bolted together auto rotating down in a housing complex in a high wind. Imagine a blimp coming down in the same place. The FAA and insurers will imagine this. Like Makani however they are more optimistic about the FAA accepting their arguments than I am, and if this moves forward it will likely be a decade or more of dedicated and restricted testing. 

Makani has a much more complete solution publicly available than Skywindpower's, and one that didn't depend on what appears to be unlikely leaps in technology. Makani's solution has significant safety limitations, but the challenges pertaining to the Skywindpower solution cover a much, much larger potential impacted area.

Skywindpower doesn't pass the sniff test. It's unlikely to be allowed, it requires solving a number of non-trivial engineering problems and if they have thought through all of the above implications of their solution, they are being pretty quiet about it. They haven't done any economic analysis that they have made public, but merely stated that there is an economic case with some already significant assumptions. The cost of the device plus tether is likely greater than a conventional wind turbine of equivalent capacity and spacing will likely have to be greater for the foreseeable future, leading to lower overall generation.

Thanks for pointing it out. I'll probably turn this relatively quick analysis into a more complete blog post soon. Was there another proposed solution with relatively equivalent public documentation you would like to me to look at?


Cheers,
Mike

----------------------------- ipad -----------------------
The future is already here. It's just not very evenly distributed. - William Gibso
Group: AirborneWindEnergy Message: 10552 From: Mike Barnard Date: 11/2/2013
Subject: Re: Clear Limits to Conventional Wind foreseen by Harvard's SEAS (AW
Small math error. The Sky Windpower craft would be larger than my email of a minute ago, closer to 70 meters or 245 ft per side to scale to 5 MW. This over the 64 m blade length of a 5 MW conventional wind turbine for another sense of scale.

Mike